<?xml version="1.0" encoding="us-ascii" standalone="yes"?>
<!-- DFIN ActiveDisclosure(SM) XBRL Linkbase Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2021-03-16T22:00:56.2428090+00:00 -->
<!-- Version            : 5.0.1.571 -->
<!-- Package ID         : 087d8ce7bda94d2086bbe5a350a72846 -->
<!-- Copyright (c) 2021 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedLabel" xlink:type="simple" />
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedNetLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedNetLabel" xlink:type="simple" />
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedPeriodEndLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedPeriodEndLabel" xlink:type="simple" />
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedPeriodStartLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedPeriodStartLabel" xlink:type="simple" />
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTerseLabel" xlink:type="simple" />
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTotalLabel" xlink:type="simple" />
  <link:roleRef roleURI="http://www.xbrl.org/2009/role/netLabel" xlink:href="http://www.xbrl.org/lrr/role/net-2009-12-16.xsd#netLabel" xlink:type="simple" />
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/label/axisDefault" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-roles-2020-01-31.xsd#axisDefault" xlink:type="simple" />
  <link:labelLink xlink:role="http://www.xbrl.org/2003/role/link" xlink:type="extended">
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCentralIndexKey" xlink:type="locator" xlink:label="dei_EntityCentralIndexKey" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCentralIndexKey" xlink:to="dei_EntityCentralIndexKey_lbl" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CoverAbstract" xlink:type="locator" xlink:label="dei_CoverAbstract" />
    <link:label xml:lang="en-US" xlink:label="dei_CoverAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Cover [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CoverAbstract" xlink:to="dei_CoverAbstract_lbl" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityRegistrantName" xlink:type="locator" xlink:label="dei_EntityRegistrantName" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityRegistrantName_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Registrant Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityRegistrantName" xlink:to="dei_EntityRegistrantName_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityRegistrantName_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Registrant Name</link:label>
    <link:label xml:lang="en-US" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Central Index Key</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentType" xlink:type="locator" xlink:label="dei_DocumentType" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentType_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Type</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentType" xlink:to="dei_DocumentType_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentType_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Document Type</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_AmendmentFlag" xlink:type="locator" xlink:label="dei_AmendmentFlag" />
    <link:label xml:lang="en-US" xlink:label="dei_AmendmentFlag_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment Flag</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_AmendmentFlag" xlink:to="dei_AmendmentFlag_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_AmendmentFlag_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Amendment Flag</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentPeriodEndDate" xlink:type="locator" xlink:label="dei_DocumentPeriodEndDate" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Period End Date</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentPeriodEndDate" xlink:to="dei_DocumentPeriodEndDate_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Document Period End Date</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:type="locator" xlink:label="dei_DocumentFiscalPeriodFocus" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Fiscal Period Focus</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalPeriodFocus" xlink:to="dei_DocumentFiscalPeriodFocus_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Period Focus</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_TradingSymbol" xlink:type="locator" xlink:label="dei_TradingSymbol" />
    <link:label xml:lang="en-US" xlink:label="dei_TradingSymbol_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_TradingSymbol" xlink:to="dei_TradingSymbol_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_TradingSymbol_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Trading Symbol</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:type="locator" xlink:label="dei_DocumentFiscalYearFocus" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Year Focus</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalYearFocus" xlink:to="dei_DocumentFiscalYearFocus_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Year Focus</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:type="locator" xlink:label="dei_CurrentFiscalYearEndDate" />
    <link:label xml:lang="en-US" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Fiscal Year End Date</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CurrentFiscalYearEndDate" xlink:to="dei_CurrentFiscalYearEndDate_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Current Fiscal Year End Date</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityWellKnownSeasonedIssuer" xlink:type="locator" xlink:label="dei_EntityWellKnownSeasonedIssuer" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityWellKnownSeasonedIssuer_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Well-known Seasoned Issuer</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityWellKnownSeasonedIssuer" xlink:to="dei_EntityWellKnownSeasonedIssuer_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityWellKnownSeasonedIssuer_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Well Known Seasoned Issuer</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityVoluntaryFilers" xlink:type="locator" xlink:label="dei_EntityVoluntaryFilers" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityVoluntaryFilers_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Voluntary Filers</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityVoluntaryFilers" xlink:to="dei_EntityVoluntaryFilers_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityVoluntaryFilers_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Voluntary Filers</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCurrentReportingStatus" xlink:type="locator" xlink:label="dei_EntityCurrentReportingStatus" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Current Reporting Status</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCurrentReportingStatus" xlink:to="dei_EntityCurrentReportingStatus_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Current Reporting Status</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFilerCategory" xlink:type="locator" xlink:label="dei_EntityFilerCategory" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityFilerCategory_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Filer Category</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFilerCategory" xlink:to="dei_EntityFilerCategory_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityFilerCategory_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Filer Category</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntitySmallBusiness" xlink:type="locator" xlink:label="dei_EntitySmallBusiness" />
    <link:label xml:lang="en-US" xlink:label="dei_EntitySmallBusiness_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Small Business</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntitySmallBusiness" xlink:to="dei_EntitySmallBusiness_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntitySmallBusiness_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Small Business</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityEmergingGrowthCompany" xlink:type="locator" xlink:label="dei_EntityEmergingGrowthCompany" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Emerging Growth Company</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityEmergingGrowthCompany" xlink:to="dei_EntityEmergingGrowthCompany_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Emerging Growth Company</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityShellCompany" xlink:type="locator" xlink:label="dei_EntityShellCompany" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityShellCompany_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Shell Company</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityShellCompany" xlink:to="dei_EntityShellCompany_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityShellCompany_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Shell Company</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityPublicFloat" xlink:type="locator" xlink:label="dei_EntityPublicFloat" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityPublicFloat_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Public Float</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityPublicFloat" xlink:to="dei_EntityPublicFloat_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityPublicFloat_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Public Float</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:type="locator" xlink:label="dei_EntityCommonStockSharesOutstanding" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Common Stock, Shares Outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCommonStockSharesOutstanding" xlink:to="dei_EntityCommonStockSharesOutstanding_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Common Stock Shares Outstanding</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityInteractiveDataCurrent" xlink:type="locator" xlink:label="dei_EntityInteractiveDataCurrent" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Interactive Data Current</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityInteractiveDataCurrent" xlink:to="dei_EntityInteractiveDataCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Interactive Data Current</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFileNumber" xlink:type="locator" xlink:label="dei_EntityFileNumber" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityFileNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFileNumber" xlink:to="dei_EntityFileNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityFileNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity File Number</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityTaxIdentificationNumber" xlink:type="locator" xlink:label="dei_EntityTaxIdentificationNumber" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Tax Identification Number</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityTaxIdentificationNumber" xlink:to="dei_EntityTaxIdentificationNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Tax Identification Number</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressAddressLine1" xlink:type="locator" xlink:label="dei_EntityAddressAddressLine1" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressAddressLine1" xlink:to="dei_EntityAddressAddressLine1_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address Address Line1</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressAddressLine2" xlink:type="locator" xlink:label="dei_EntityAddressAddressLine2" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line Two</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressAddressLine2" xlink:to="dei_EntityAddressAddressLine2_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address Address Line2</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressCityOrTown" xlink:type="locator" xlink:label="dei_EntityAddressCityOrTown" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressCityOrTown" xlink:to="dei_EntityAddressCityOrTown_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address City Or Town</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressStateOrProvince" xlink:type="locator" xlink:label="dei_EntityAddressStateOrProvince" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, State or Province</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressStateOrProvince" xlink:to="dei_EntityAddressStateOrProvince_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address State Or Province</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressPostalZipCode" xlink:type="locator" xlink:label="dei_EntityAddressPostalZipCode" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Postal Zip Code</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressPostalZipCode" xlink:to="dei_EntityAddressPostalZipCode_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address Postal Zip Code</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CityAreaCode" xlink:type="locator" xlink:label="dei_CityAreaCode" />
    <link:label xml:lang="en-US" xlink:label="dei_CityAreaCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">City Area Code</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CityAreaCode" xlink:to="dei_CityAreaCode_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_CityAreaCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">City Area Code</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LocalPhoneNumber" xlink:type="locator" xlink:label="dei_LocalPhoneNumber" />
    <link:label xml:lang="en-US" xlink:label="dei_LocalPhoneNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Local Phone Number</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_LocalPhoneNumber" xlink:to="dei_LocalPhoneNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_LocalPhoneNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Local Phone Number</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentAnnualReport" xlink:type="locator" xlink:label="dei_DocumentAnnualReport" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentAnnualReport_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Annual Report</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentAnnualReport" xlink:to="dei_DocumentAnnualReport_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentAnnualReport_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Document Annual Report</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentTransitionReport" xlink:type="locator" xlink:label="dei_DocumentTransitionReport" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentTransitionReport_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Transition Report</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentTransitionReport" xlink:to="dei_DocumentTransitionReport_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentTransitionReport_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Document Transition Report</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_Security12bTitle" xlink:type="locator" xlink:label="dei_Security12bTitle" />
    <link:label xml:lang="en-US" xlink:label="dei_Security12bTitle_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of 12(b) Security</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_Security12bTitle" xlink:to="dei_Security12bTitle_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_Security12bTitle_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Security12b Title</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_SecurityExchangeName" xlink:type="locator" xlink:label="dei_SecurityExchangeName" />
    <link:label xml:lang="en-US" xlink:label="dei_SecurityExchangeName_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_SecurityExchangeName" xlink:to="dei_SecurityExchangeName_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_SecurityExchangeName_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Security Exchange Name</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityIncorporationStateCountryCode" xlink:type="locator" xlink:label="dei_EntityIncorporationStateCountryCode" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Incorporation, State or Country Code</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityIncorporationStateCountryCode" xlink:to="dei_EntityIncorporationStateCountryCode_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Incorporation State Country Code</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:type="locator" xlink:label="us-gaap_StatementOfFinancialPositionAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Statement Of Financial Position [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementOfFinancialPositionAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsAbstract" xlink:type="locator" xlink:label="us-gaap_AssetsAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASSETS</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_AssetsAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:type="locator" xlink:label="us-gaap_AssetsCurrentAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current assets:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_AssetsCurrentAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Assets Current [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Cash And Cash Equivalents At Carrying Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsCurrent" xlink:type="locator" xlink:label="us-gaap_OtherAssetsCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other current assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAssetsCurrent" xlink:to="us-gaap_OtherAssetsCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Other Assets Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrent" xlink:type="locator" xlink:label="us-gaap_AssetsCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrent" xlink:to="us-gaap_AssetsCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Assets Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Right-of-use asset - operating</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseRightOfUseAsset" xlink:to="us-gaap_OperatingLeaseRightOfUseAsset_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Right Of Use Asset</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment, net</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentNet" xlink:to="us-gaap_PropertyPlantAndEquipmentNet_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Net</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:type="locator" xlink:label="us-gaap_OtherAssetsNoncurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAssetsNoncurrent" xlink:to="us-gaap_OtherAssetsNoncurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Other Assets Noncurrent</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets" xlink:type="locator" xlink:label="us-gaap_Assets" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_Assets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Assets" xlink:to="us-gaap_Assets_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_Assets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Assets</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:type="locator" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LIABILITIES AND STOCKHOLDERS&#8217; EQUITY</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities And Stockholders Equity [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:type="locator" xlink:label="us-gaap_LiabilitiesCurrentAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current liabilities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_LiabilitiesCurrentAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities Current [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:type="locator" xlink:label="us-gaap_AccountsPayableCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableCurrent" xlink:to="us-gaap_AccountsPayableCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:type="locator" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued compensation and employee benefits</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:to="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Employee Related Liabilities Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAccruedLiabilitiesCurrent" xlink:type="locator" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued expenses and other liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAccruedLiabilitiesCurrent" xlink:to="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Other Accrued Liabilities Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:type="locator" xlink:label="us-gaap_LiabilitiesCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrent" xlink:to="us-gaap_LiabilitiesCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease liability, net of current portion</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:to="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Liability Noncurrent</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Liabilities" xlink:type="locator" xlink:label="us-gaap_Liabilities" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_Liabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_Liabilities_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_Liabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:type="locator" xlink:label="us-gaap_CommitmentsAndContingencies" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and contingencies</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingencies" xlink:to="us-gaap_CommitmentsAndContingencies_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Commitments And Contingencies</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:type="locator" xlink:label="us-gaap_StockholdersEquityAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders&#8217; equity:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquityAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders Equity [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockValue" xlink:type="locator" xlink:label="us-gaap_PreferredStockValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, $0.001 par value; 5 million shares authorized; no shares issued or outstanding at December 31, 2020 and 2019</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockValue" xlink:to="us-gaap_PreferredStockValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockValue" xlink:type="locator" xlink:label="us-gaap_CommonStockValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, $0.001 par value; 100 million shares authorized at December 31, 2020 and 2019; 9,548,150 and 1,594,070 shares issued and outstanding at December 31, 2020 and 2019, respectively</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockValue" xlink:to="us-gaap_CommonStockValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:type="locator" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalCommonStock" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid In Capital Common Stock</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:type="locator" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated deficit</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings Accumulated Deficit</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity" xlink:type="locator" xlink:label="us-gaap_StockholdersEquity" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total stockholders&#8217; equity</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquity" xlink:to="us-gaap_StockholdersEquity_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders Equity</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:type="locator" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities and stockholders&#8217; equity</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities And Stockholders Equity</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:type="locator" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, par value</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock Par Or Stated Value Per Share</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:type="locator" xlink:label="us-gaap_PreferredStockSharesAuthorized" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares authorized</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesAuthorized" xlink:to="us-gaap_PreferredStockSharesAuthorized_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock Shares Authorized</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:type="locator" xlink:label="us-gaap_PreferredStockSharesIssued" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, issued</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesIssued" xlink:to="us-gaap_PreferredStockSharesIssued_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock Shares Issued</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:type="locator" xlink:label="us-gaap_PreferredStockSharesOutstanding" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesOutstanding" xlink:to="us-gaap_PreferredStockSharesOutstanding_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock Shares Outstanding</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:type="locator" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, par value</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockParOrStatedValuePerShare" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Par Or Stated Value Per Share</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:type="locator" xlink:label="us-gaap_CommonStockSharesAuthorized" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares authorized</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesAuthorized" xlink:to="us-gaap_CommonStockSharesAuthorized_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Shares Authorized</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:type="locator" xlink:label="us-gaap_CommonStockSharesIssued" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares issued</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesIssued" xlink:to="us-gaap_CommonStockSharesIssued_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Shares Issued</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:type="locator" xlink:label="us-gaap_CommonStockSharesOutstanding" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesOutstanding" xlink:to="us-gaap_CommonStockSharesOutstanding_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Shares Outstanding</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementAbstract" xlink:type="locator" xlink:label="us-gaap_IncomeStatementAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_IncomeStatementAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpensesAbstract" xlink:type="locator" xlink:label="us-gaap_OperatingExpensesAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Costs and expenses:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingExpensesAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:type="locator" xlink:label="us-gaap_ResearchAndDevelopmentExpense" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and development</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpense" xlink:to="us-gaap_ResearchAndDevelopmentExpense_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Research And Development Expense</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeneralAndAdministrativeExpense" xlink:type="locator" xlink:label="us-gaap_GeneralAndAdministrativeExpense" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and administrative</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GeneralAndAdministrativeExpense" xlink:to="us-gaap_GeneralAndAdministrativeExpense_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">General And Administrative Expense</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpenses" xlink:type="locator" xlink:label="us-gaap_OperatingExpenses" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total costs and expenses</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OperatingExpenses_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:type="locator" xlink:label="us-gaap_OperatingIncomeLoss" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Loss from operations</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingIncomeLoss" xlink:to="us-gaap_OperatingIncomeLoss_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Income Loss</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestAndOtherIncome" xlink:type="locator" xlink:label="us-gaap_InterestAndOtherIncome" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_InterestAndOtherIncome_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and other income</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestAndOtherIncome" xlink:to="us-gaap_InterestAndOtherIncome_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_InterestAndOtherIncome_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Interest And Other Income</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpense" xlink:type="locator" xlink:label="us-gaap_InterestExpense" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_InterestExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Interest expense</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpense" xlink:to="us-gaap_InterestExpense_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_InterestExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:type="locator" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Loss before income taxes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Income tax benefit</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_IncomeTaxExpenseBenefit_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense Benefit</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss" xlink:type="locator" xlink:label="us-gaap_NetIncomeLoss" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net loss</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_NetIncomeLoss_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Income Loss</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:type="locator" xlink:label="us-gaap_EarningsPerShareBasicAndDilutedAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareBasicAndDilutedAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net loss per share:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:to="us-gaap_EarningsPerShareBasicAndDilutedAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareBasicAndDilutedAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Basic And Diluted [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:type="locator" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basic and diluted</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasicAndDiluted" xlink:to="us-gaap_EarningsPerShareBasicAndDiluted_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Basic And Diluted</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:type="locator" xlink:label="us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average shares outstanding:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:to="us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Basic And Diluted Other Disclosures [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basic and diluted</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:to="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number Of Share Outstanding Basic And Diluted</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_StockIssuedDuringPeriodValueStockSplits" xlink:type="locator" xlink:label="abio_StockIssuedDuringPeriodValueStockSplits" />
    <link:label xml:lang="en-US" xlink:label="abio_StockIssuedDuringPeriodValueStockSplits_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock issued during period value stock splits.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_StockIssuedDuringPeriodValueStockSplits" xlink:to="abio_StockIssuedDuringPeriodValueStockSplits_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrantsShares" xlink:type="locator" xlink:label="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrantsShares" />
    <link:label xml:lang="en-US" xlink:label="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrantsShares_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of common stock and exercise of prefunded warrants shares.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrantsShares" xlink:to="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrantsShares_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrants" xlink:type="locator" xlink:label="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrants" />
    <link:label xml:lang="en-US" xlink:label="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrants_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of common stock and exercise of prefunded warrants.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrants" xlink:to="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrants_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfStockholdersEquityAbstract" xlink:type="locator" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Statement Of Stockholders Equity [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfStockholdersEquityAbstract" xlink:to="us-gaap_StatementOfStockholdersEquityAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable" xlink:type="locator" xlink:label="us-gaap_StatementTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:type="locator" xlink:label="us-gaap_StatementEquityComponentsAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Components</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_StatementEquityComponentsAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Statement Equity Components [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain" xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Component</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_EquityComponentDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember" xlink:type="locator" xlink:label="us-gaap_CommonStockMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockMember" xlink:to="us-gaap_CommonStockMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:type="locator" xlink:label="us-gaap_AdditionalPaidInCapitalMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional Paid-In Capital</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalMember" xlink:to="us-gaap_AdditionalPaidInCapitalMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid In Capital [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:type="locator" xlink:label="us-gaap_RetainedEarningsMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Deficit</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsMember" xlink:to="us-gaap_RetainedEarningsMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems" xlink:type="locator" xlink:label="us-gaap_StatementLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning Balance</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning Balance, shares</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock for cash, net of offering costs</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value New Issues</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock for cash, net of offering costs, shares</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares New Issues</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_StockIssuedDuringPeriodValueStockSplits_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustment for fractional, value</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_StockIssuedDuringPeriodValueStockSplits_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value Stock Splits</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustment for fractional shares</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" xlink:to="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares Reverse Stock Splits</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrants_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock and exercise of prefunded warrants for cash, net of offering costs</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrants_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock And Exercise Of Prefunded Warrants</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrantsShares_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock and exercise of prefunded warrants for cash, net of offering costs, shares</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IssuanceOfCommonStockAndExerciseOfPrefundedWarrantsShares_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock And Exercise Of Prefunded Warrants Shares</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:type="locator" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based compensation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net loss</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending Balance</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending Balance, shares</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_CommonStockOfferingCostsAccruedReversalButNotYetPaid" xlink:type="locator" xlink:label="abio_CommonStockOfferingCostsAccruedReversalButNotYetPaid" />
    <link:label xml:lang="en-US" xlink:label="abio_CommonStockOfferingCostsAccruedReversalButNotYetPaid_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock offering costs accrued (reversal) but not yet paid.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_CommonStockOfferingCostsAccruedReversalButNotYetPaid" xlink:to="abio_CommonStockOfferingCostsAccruedReversalButNotYetPaid_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:type="locator" xlink:label="us-gaap_StatementOfCashFlowsAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Statement Of Cash Flows [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_StatementOfCashFlowsAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash flows from operating activities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Operating Activities [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:type="locator" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile net loss to net cash used in operating activities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationAndAmortization" xlink:type="locator" xlink:label="us-gaap_DepreciationAndAmortization" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Depreciation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DepreciationAndAmortization" xlink:to="us-gaap_DepreciationAndAmortization_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation And Amortization</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of right-of-use asset - operating</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense" xlink:to="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Right Of Use Asset Amortization Expense</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensation" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based compensation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensation" xlink:to="us-gaap_ShareBasedCompensation_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in operating assets and liabilities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Operating Capital [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssets" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentAssets" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentAssets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other current assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOtherCurrentAssets" xlink:to="us-gaap_IncreaseDecreaseInOtherCurrentAssets_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentAssets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Other Current Assets</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" xlink:to="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Other Noncurrent Assets</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsPayable" xlink:to="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accounts Payable</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued compensation and employee benefits</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities" xlink:to="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Employee Related Liabilities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued expenses and other liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities" xlink:to="us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accrued Liabilities And Other Operating Liabilities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash used in operating activities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Operating Activities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash flows from investing activities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Investing Activities [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchase of property and equipment</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:to="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Payments To Acquire Property Plant And Equipment</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash used in investing activities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Investing Activities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash flows from financing activities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Financing Activities [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:type="locator" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from the issuance of common stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Issuance Of Common Stock</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsOfStockIssuanceCosts" xlink:type="locator" xlink:label="us-gaap_PaymentsOfStockIssuanceCosts" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PaymentsOfStockIssuanceCosts_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Common stock offering costs</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsOfStockIssuanceCosts" xlink:to="us-gaap_PaymentsOfStockIssuanceCosts_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PaymentsOfStockIssuanceCosts_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Payments Of Stock Issuance Costs</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths" xlink:type="locator" xlink:label="us-gaap_RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayment of principal on vendor finance agreement</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths" xlink:to="us-gaap_RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Repayments Of Short Term Debt Maturing In More Than Three Months</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by financing activities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Financing Activities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:type="locator" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net increase in cash and cash equivalents</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:type="locator" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash and cash equivalents, beginning of year</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash and cash equivalents, end of year</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:type="locator" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental cash flow information:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_SupplementalCashFlowInformationAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Information [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestPaidNet" xlink:type="locator" xlink:label="us-gaap_InterestPaidNet" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest paid</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestPaidNet" xlink:to="us-gaap_InterestPaidNet_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Interest Paid Net</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIncomeTaxRefunds" xlink:type="locator" xlink:label="us-gaap_ProceedsFromIncomeTaxRefunds" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProceedsFromIncomeTaxRefunds_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax refund received</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIncomeTaxRefunds" xlink:to="us-gaap_ProceedsFromIncomeTaxRefunds_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProceedsFromIncomeTaxRefunds_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Income Tax Refunds</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:type="locator" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental disclosure of noncash investing and financing transactions:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:to="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability" xlink:type="locator" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leased assets obtained in exchange for operating lease liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability" xlink:to="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Right Of Use Asset Obtained In Exchange For Operating Lease Liability</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CommonStockOfferingCostsAccruedReversalButNotYetPaid_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock offering costs accrued but not yet paid</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CommonStockOfferingCostsAccruedReversalButNotYetPaid_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Offering Costs Accrued Reversal But Not Yet Paid</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentsIncorporatedByReferenceTextBlock" xlink:type="locator" xlink:label="dei_DocumentsIncorporatedByReferenceTextBlock" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentsIncorporatedByReferenceTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Documents Incorporated by Reference</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentsIncorporatedByReferenceTextBlock" xlink:to="dei_DocumentsIncorporatedByReferenceTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_DocumentsIncorporatedByReferenceTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Documents Incorporated By Reference [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountingPoliciesAbstract" xlink:type="locator" xlink:label="us-gaap_AccountingPoliciesAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccountingPoliciesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Policies [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_AccountingPoliciesAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock" xlink:type="locator" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">The Company and Summary of Significant Accounting Policies</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock" xlink:to="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Organization Consolidation And Presentation Of Financial Statements Disclosure And Significant Accounting Policies [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareAbstract" xlink:type="locator" xlink:label="us-gaap_EarningsPerShareAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareAbstract" xlink:to="us-gaap_EarningsPerShareAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareTextBlock" xlink:type="locator" xlink:label="us-gaap_EarningsPerShareTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Loss Per Share</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareTextBlock" xlink:to="us-gaap_EarningsPerShareTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:type="locator" xlink:label="us-gaap_FairValueDisclosuresAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueDisclosuresAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresTextBlock" xlink:type="locator" xlink:label="us-gaap_FairValueDisclosuresTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Disclosures</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosuresTextBlock" xlink:to="us-gaap_FairValueDisclosuresTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAbstract" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and Equipment</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Disclosure [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsAbstract" xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionsAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsAbstract" xlink:to="us-gaap_RelatedPartyTransactionsAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Arrangements</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:to="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions Disclosure [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:type="locator" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Commitments And Contingencies Disclosure [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:type="locator" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Commitments And Contingencies Disclosure [Text Block]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_EquityFinancingsAndWarrantsDisclosureTextBlock" xlink:type="locator" xlink:label="abio_EquityFinancingsAndWarrantsDisclosureTextBlock" />
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingsAndWarrantsDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Description of equity financings during the periods presented and information related to outstanding warrants of company stock.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_EquityFinancingsAndWarrantsDisclosureTextBlock" xlink:to="abio_EquityFinancingsAndWarrantsDisclosureTextBlock_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityAbstract" xlink:type="locator" xlink:label="us-gaap_EquityAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EquityAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_EquityAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingsAndWarrantsDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Financings and Warrants</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingsAndWarrantsDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Equity Financings And Warrants Disclosure [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract" xlink:type="locator" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract" xlink:to="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:type="locator" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based Compensation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:to="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Disclosure Of Compensation Related Costs Share Based Payments [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CompensationAndRetirementDisclosureAbstract" xlink:type="locator" xlink:label="us-gaap_CompensationAndRetirementDisclosureAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CompensationAndRetirementDisclosureAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Compensation And Retirement Disclosure [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CompensationAndRetirementDisclosureAbstract" xlink:to="us-gaap_CompensationAndRetirementDisclosureAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock" xlink:type="locator" xlink:label="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Benefit Plans</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock" xlink:to="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Pension And Other Postretirement Benefits Disclosure [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:type="locator" xlink:label="us-gaap_IncomeTaxDisclosureAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxDisclosureAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_IncomeTaxDisclosureAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxDisclosureTextBlock" xlink:type="locator" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxDisclosureTextBlock" xlink:to="us-gaap_IncomeTaxDisclosureTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventsAbstract" xlink:type="locator" xlink:label="us-gaap_SubsequentEventsAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventsAbstract" xlink:to="us-gaap_SubsequentEventsAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventsTextBlock" xlink:type="locator" xlink:label="us-gaap_SubsequentEventsTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventsTextBlock" xlink:to="us-gaap_SubsequentEventsTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Text Block]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_DescriptionOfBusinessPolicyTextBlock" xlink:type="locator" xlink:label="abio_DescriptionOfBusinessPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="abio_DescriptionOfBusinessPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Description of business.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_DescriptionOfBusinessPolicyTextBlock" xlink:to="abio_DescriptionOfBusinessPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_DescriptionOfBusinessPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Description of Business</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DescriptionOfBusinessPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Description Of Business Policy [Text Block]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_LiquidityAndGoingConcernPolicyTextBlock" xlink:type="locator" xlink:label="abio_LiquidityAndGoingConcernPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="abio_LiquidityAndGoingConcernPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Liquidity and going concern.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_LiquidityAndGoingConcernPolicyTextBlock" xlink:to="abio_LiquidityAndGoingConcernPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_LiquidityAndGoingConcernPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liquidity and Going Concern</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_LiquidityAndGoingConcernPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Liquidity And Going Concern Policy [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:type="locator" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:to="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Basis Of Accounting Policy Policy [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:type="locator" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recent Accounting Pronouncements</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:to="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">New Accounting Pronouncements Policy Policy [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UseOfEstimates" xlink:type="locator" xlink:label="us-gaap_UseOfEstimates" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounting Estimates in the Preparation of Financial Statements</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UseOfEstimates" xlink:to="us-gaap_UseOfEstimates_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Use Of Estimates</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Equivalents</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:to="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Cash And Cash Equivalents Policy [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskCreditRisk" xlink:type="locator" xlink:label="us-gaap_ConcentrationRiskCreditRisk" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ConcentrationRiskCreditRisk_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Concentrations of Credit Risk</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskCreditRisk" xlink:to="us-gaap_ConcentrationRiskCreditRisk_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ConcentrationRiskCreditRisk_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Concentration Risk Credit Risk</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and Equipment</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Policy [Text Block]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_ComprehensiveLossPolicyPolicyTextBlock" xlink:type="locator" xlink:label="abio_ComprehensiveLossPolicyPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="abio_ComprehensiveLossPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Comprehensive loss policy.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_ComprehensiveLossPolicyPolicyTextBlock" xlink:to="abio_ComprehensiveLossPolicyPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_ComprehensiveLossPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Comprehensive Loss</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_ComprehensiveLossPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Loss Policy Policy [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeLeasesPolicyTextBlock" xlink:type="locator" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leases</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeLeasesPolicyTextBlock" xlink:to="us-gaap_LesseeLeasesPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Leases Policy [Text Block]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_AccruedOutsourcingExpensesPolicyTextBlock" xlink:type="locator" xlink:label="abio_AccruedOutsourcingExpensesPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="abio_AccruedOutsourcingExpensesPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued outsourcing expenses.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_AccruedOutsourcingExpensesPolicyTextBlock" xlink:to="abio_AccruedOutsourcingExpensesPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_AccruedOutsourcingExpensesPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued Outsourcing Expenses</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_AccruedOutsourcingExpensesPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Outsourcing Expenses Policy [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingPolicyPolicyTextBlock" xlink:type="locator" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segments</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SegmentReportingPolicyPolicyTextBlock" xlink:to="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting Policy Policy [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpensePolicy" xlink:type="locator" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and Development</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpensePolicy" xlink:to="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Research And Development Expense Policy</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-Based Compensation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" xlink:to="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Option And Incentive Plans Policy</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxPolicyTextBlock" xlink:type="locator" xlink:label="us-gaap_IncomeTaxPolicyTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxPolicyTextBlock" xlink:to="us-gaap_IncomeTaxPolicyTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxPolicyTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Policy [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock" xlink:type="locator" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Potentially Dilutive Shares of Common Stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock" xlink:to="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Property and Equipment</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock" xlink:type="locator" xlink:label="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Future Minimum Commitments due Under October 2020 Lease Agreement</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock" xlink:to="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Future Minimum Rental Payments For Operating Leases Table [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock" xlink:type="locator" xlink:label="us-gaap_ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Warrants by Year of Expiration</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock" xlink:to="us-gaap_ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfStockholdersEquityNoteWarrantsOrRightsTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Stockholders Equity Note Warrants Or Rights [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:type="locator" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated Weighted Average Grant Date Fair Value per Share</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:type="locator" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Stock Option Activities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Share Based Compensation Stock Options Activity Table [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:type="locator" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Non-cash, Share-based Compensation Expense</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock" xlink:type="locator" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Tax Benefit Attributable to Our Loss from Operations</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock" xlink:to="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Effective Income Tax Rate Reconciliation Table [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" xlink:type="locator" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Deferred Tax Assets and Liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" xlink:to="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Deferred Tax Assets And Liabilities Table [Text Block]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_CompanyAndSummaryOfSignificantAccountingPoliciesTableLineItems" xlink:type="locator" xlink:label="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTableLineItems" />
    <link:label xml:lang="en-US" xlink:label="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTableLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Company and summary of significant accounting policies.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTableLineItems" xlink:to="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTableLineItems_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_CompanyAndSummaryOfSignificantAccountingPoliciesTable" xlink:type="locator" xlink:label="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTable" />
    <link:label xml:lang="en-US" xlink:label="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Company and summary of significant accounting policies.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTable" xlink:to="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company And Summary Of Significant Accounting Policies [Table]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Company And Summary Of Significant Accounting Policies [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfArrangementAxis" xlink:type="locator" xlink:label="us-gaap_TypeOfArrangementAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_TypeOfArrangementAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Type Of Arrangement [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:type="locator" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Arrangements And Nonarrangement Transactions [Member]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_NewCapitalOnDemandSalesAgreementMember" xlink:type="locator" xlink:label="abio_NewCapitalOnDemandSalesAgreementMember" />
    <link:label xml:lang="en-US" xlink:label="abio_NewCapitalOnDemandSalesAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">New Capital on Demand Sales Agreement.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_NewCapitalOnDemandSalesAgreementMember" xlink:to="abio_NewCapitalOnDemandSalesAgreementMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_NewCapitalOnDemandSalesAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Sales Agreement</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_NewCapitalOnDemandSalesAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">New Capital On Demand Sales Agreement [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event Type</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event Type</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventTypeDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember" xlink:type="locator" xlink:label="us-gaap_SubsequentEventMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventMember" xlink:to="us-gaap_SubsequentEventMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Member]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTableLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company And Summary Of Significant Accounting Policies Table [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CompanyAndSummaryOfSignificantAccountingPoliciesTableLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Company And Summary Of Significant Accounting Policies Table [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Revenues" xlink:type="locator" xlink:label="us-gaap_Revenues" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_Revenues_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenues</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Revenues" xlink:to="us-gaap_Revenues_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_Revenues_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revenues</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountAsset" xlink:type="locator" xlink:label="us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountAsset" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Concentrations of credit risk</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountAsset" xlink:to="us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountAsset_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosure Offbalance Sheet Risks Amount Asset</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfOperatingSegments" xlink:type="locator" xlink:label="us-gaap_NumberOfOperatingSegments" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of segments</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NumberOfOperatingSegments" xlink:to="us-gaap_NumberOfOperatingSegments_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Operating Segments</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:type="locator" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:to="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:type="locator" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:type="locator" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities, Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Name [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockOptionMember" xlink:type="locator" xlink:label="us-gaap_StockOptionMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockOptionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding stock options</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockOptionMember" xlink:to="us-gaap_StockOptionMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockOptionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stock Option [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WarrantMember" xlink:type="locator" xlink:label="us-gaap_WarrantMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_WarrantMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants to purchase common stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WarrantMember" xlink:to="us-gaap_WarrantMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_WarrantMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Warrant [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:type="locator" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:type="locator" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_FairValueAssetsBetweenHierarchyLevelsTransfersAmount" xlink:type="locator" xlink:label="abio_FairValueAssetsBetweenHierarchyLevelsTransfersAmount" />
    <link:label xml:lang="en-US" xlink:label="abio_FairValueAssetsBetweenHierarchyLevelsTransfersAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value assets between hierarchy levels transfers amount.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_FairValueAssetsBetweenHierarchyLevelsTransfersAmount" xlink:to="abio_FairValueAssetsBetweenHierarchyLevelsTransfersAmount_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:type="locator" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:type="locator" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:to="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value By Measurement Frequency [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementFrequencyDomain" xlink:to="us-gaap_FairValueMeasurementFrequencyDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement Frequency [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementsRecurringMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Measurements, Recurring</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementsRecurringMember" xlink:to="us-gaap_FairValueMeasurementsRecurringMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurements Recurring [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:type="locator" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value By Fair Value Hierarchy Level [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurements Fair Value Hierarchy [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:type="locator" xlink:label="us-gaap_FairValueInputsLevel1Member" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 1</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueInputsLevel1Member" xlink:to="us-gaap_FairValueInputsLevel1Member_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Inputs Level1 [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByAssetClassAxis" xlink:type="locator" xlink:label="us-gaap_FairValueByAssetClassAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueByAssetClassAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset Class</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueByAssetClassAxis" xlink:to="us-gaap_FairValueByAssetClassAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueByAssetClassAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value By Asset Class [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:type="locator" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset Class</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation By Asset Class [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MoneyMarketFundsMember" xlink:type="locator" xlink:label="us-gaap_MoneyMarketFundsMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Money Market Funds</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MoneyMarketFundsMember" xlink:to="us-gaap_MoneyMarketFundsMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:type="locator" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash equivalents consisting of money market funds and commercial paper</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:to="us-gaap_CashAndCashEquivalentsFairValueDisclosure_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Cash And Cash Equivalents Fair Value Disclosure</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_FairValueAssetsBetweenHierarchyLevelsTransfersAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transfers of assets between fair value hierarchy levels</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_FairValueAssetsBetweenHierarchyLevelsTransfersAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Assets Between Hierarchy Levels Transfers Amount</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:type="locator" xlink:label="us-gaap_DebtLongtermAndShorttermCombinedAmount" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtLongtermAndShorttermCombinedAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:to="us-gaap_DebtLongtermAndShorttermCombinedAmount_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtLongtermAndShorttermCombinedAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Longterm And Shortterm Combined Amount</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:type="locator" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Property Plant And Equipment [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:to="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Property Plant And Equipment [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:to="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment By Type [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Type [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:type="locator" xlink:label="us-gaap_ComputerEquipmentMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computer Equipment</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComputerEquipmentMember" xlink:to="us-gaap_ComputerEquipmentMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Computer Equipment [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquipmentMember" xlink:type="locator" xlink:label="us-gaap_EquipmentMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EquipmentMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lab Equipment</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquipmentMember" xlink:to="us-gaap_EquipmentMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EquipmentMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Equipment [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:type="locator" xlink:label="us-gaap_FurnitureAndFixturesMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Furniture and Fixtures</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FurnitureAndFixturesMember" xlink:to="us-gaap_FurnitureAndFixturesMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Furniture And Fixtures [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember" xlink:type="locator" xlink:label="us-gaap_SoftwareAndSoftwareDevelopmentCostsMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computer Software</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SoftwareAndSoftwareDevelopmentCostsMember" xlink:to="us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Software And Software Development Costs [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:type="locator" xlink:label="us-gaap_LeaseholdImprovementsMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leasehold Improvements</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseholdImprovementsMember" xlink:to="us-gaap_LeaseholdImprovementsMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Leasehold Improvements [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property Plant And Equipment [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated Life</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:to="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Useful Life</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated Life</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives" xlink:to="us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Estimated Useful Lives</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentGross" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and Equipment, Gross</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentGross" xlink:to="us-gaap_PropertyPlantAndEquipmentGross_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Gross</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:type="locator" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accumulated depreciation and amortization</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:to="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Depreciation Depletion And Amortization Property Plant And Equipment</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Property and equipment, net</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Depreciation and amortization expense</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:type="locator" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Related Party Transactions By Related Party [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Related Party Transactions By Related Party [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions By Related Party [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="us-gaap_RelatedPartyDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Related Party [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ChiefExecutiveOfficerMember" xlink:type="locator" xlink:label="srt_ChiefExecutiveOfficerMember" />
    <link:label xml:lang="en-US" xlink:label="srt_ChiefExecutiveOfficerMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Chief Executive Officer</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ChiefExecutiveOfficerMember" xlink:to="srt_ChiefExecutiveOfficerMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="srt_ChiefExecutiveOfficerMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Chief Executive Officer [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:type="locator" xlink:label="us-gaap_IncomeStatementLocationAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement Location [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:type="locator" xlink:label="us-gaap_IncomeStatementLocationDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_IncomeStatementLocationDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement Location [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:type="locator" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research Grants</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpenseMember" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Research And Development Expense [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_RelatedPartyTransactionLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total expense</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:to="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction Expenses From Transactions With Related Party</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_CommitmentsAndContingenciesLineItems" xlink:type="locator" xlink:label="abio_CommitmentsAndContingenciesLineItems" />
    <link:label xml:lang="en-US" xlink:label="abio_CommitmentsAndContingenciesLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Commitments and contingencies.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_CommitmentsAndContingenciesLineItems" xlink:to="abio_CommitmentsAndContingenciesLineItems_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_CommitmentsAndContingenciesTable" xlink:type="locator" xlink:label="abio_CommitmentsAndContingenciesTable" />
    <link:label xml:lang="en-US" xlink:label="abio_CommitmentsAndContingenciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Commitments and contingencies.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_CommitmentsAndContingenciesTable" xlink:to="abio_CommitmentsAndContingenciesTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_CommitmentsAndContingenciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments And Contingencies [Table]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CommitmentsAndContingenciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Commitments And Contingencies [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:type="locator" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and Administrative Expense</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GeneralAndAdministrativeExpenseMember" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">General And Administrative Expense [Member]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CommitmentsAndContingenciesLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments And Contingencies [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CommitmentsAndContingenciesLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Commitments And Contingencies [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AreaOfRealEstateProperty" xlink:type="locator" xlink:label="us-gaap_AreaOfRealEstateProperty" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AreaOfRealEstateProperty_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Area of office facilities taken on lease</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AreaOfRealEstateProperty" xlink:to="us-gaap_AreaOfRealEstateProperty_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AreaOfRealEstateProperty_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Area Of Real Estate Property</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_LeaseRenewalStartDate" xlink:type="locator" xlink:label="abio_LeaseRenewalStartDate" />
    <link:label xml:lang="en-US" xlink:label="abio_LeaseRenewalStartDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Lease renewal start date.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_LeaseRenewalStartDate" xlink:to="abio_LeaseRenewalStartDate_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional operating lease term</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseRenewalTerm" xlink:to="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Renewal Term</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_LeaseRenewalStartDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease renewal start date</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_LeaseRenewalStartDate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lease Renewal Start Date</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseExpirationDate1" xlink:type="locator" xlink:label="us-gaap_LeaseExpirationDate1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LeaseExpirationDate1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease expiration date</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseExpirationDate1" xlink:to="us-gaap_LeaseExpirationDate1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LeaseExpirationDate1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lease Expiration Date1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseTermOfContract" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease term</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseTermOfContract" xlink:to="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Term Of Contract</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseOptionToExtend" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease renewal option</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseOptionToExtend" xlink:to="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Option To Extend</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lessee, Operating Lease, Existence of Option to Extend [true false]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend" xlink:to="us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseExistenceOfOptionToExtend_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Existence Of Option To Extend</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseAssumptionsAndJudgmentsAllocationOfLeaseAndNonleaseComponent" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseAssumptionsAndJudgmentsAllocationOfLeaseAndNonleaseComponent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseAssumptionsAndJudgmentsAllocationOfLeaseAndNonleaseComponent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lessee, operating lease, assumptions and judgments, allocation of lease and nonlease component</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseAssumptionsAndJudgmentsAllocationOfLeaseAndNonleaseComponent" xlink:to="us-gaap_LesseeOperatingLeaseAssumptionsAndJudgmentsAllocationOfLeaseAndNonleaseComponent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseAssumptionsAndJudgmentsAllocationOfLeaseAndNonleaseComponent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Assumptions And Judgments Allocation Of Lease And Nonlease Component</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2021</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due Next Twelve Months</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due Year Two</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due Year Three</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due Year Four</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2025</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due Year Five</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thereafter</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due After Year Five</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total remaining lease payments</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: imputed lease interest</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Undiscounted Excess Amount</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: Current portion</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityCurrent" xlink:to="us-gaap_OperatingLeaseLiabilityCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Liability Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList" xlink:to="us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Liability Current Statement Of Financial Position Extensible List</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseCost" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseCost" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseCost_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Rent expense</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseCost" xlink:to="us-gaap_OperatingLeaseCost_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseCost_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Cost</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasePayments" xlink:type="locator" xlink:label="us-gaap_OperatingLeasePayments" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease, cash paid for measurement of lease liabilities</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasePayments" xlink:to="us-gaap_OperatingLeasePayments_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Payments</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiability" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease liability</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiability" xlink:to="us-gaap_OperatingLeaseLiability_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Liability</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList" xlink:to="us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Liability Noncurrent Statement Of Financial Position Extensible List</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average remaining lease term</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:to="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Weighted Average Remaining Lease Term1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:type="locator" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average discount rate</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:to="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Weighted Average Discount Rate Percent</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_SellingCommissionPerAdditionalSharesSoldPercentage" xlink:type="locator" xlink:label="abio_SellingCommissionPerAdditionalSharesSoldPercentage" />
    <link:label xml:lang="en-US" xlink:label="abio_SellingCommissionPerAdditionalSharesSoldPercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Selling commission per additional shares sold percentage.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_SellingCommissionPerAdditionalSharesSoldPercentage" xlink:to="abio_SellingCommissionPerAdditionalSharesSoldPercentage_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_EquityFinancingAndWarrantsLineItems" xlink:type="locator" xlink:label="abio_EquityFinancingAndWarrantsLineItems" />
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingAndWarrantsLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity financing and warrants.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_EquityFinancingAndWarrantsLineItems" xlink:to="abio_EquityFinancingAndWarrantsLineItems_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_EquityFinancingAndWarrantsTable" xlink:type="locator" xlink:label="abio_EquityFinancingAndWarrantsTable" />
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingAndWarrantsTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity financing and warrants.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_EquityFinancingAndWarrantsTable" xlink:to="abio_EquityFinancingAndWarrantsTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingAndWarrantsTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Financing And Warrants [Table]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingAndWarrantsTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Equity Financing And Warrants [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:type="locator" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SubsidiarySaleOfStockAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Subsidiary Sale Of Stock [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:type="locator" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sale Of Stock Name Of Transaction [Domain]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_DirectOfferingMember" xlink:type="locator" xlink:label="abio_DirectOfferingMember" />
    <link:label xml:lang="en-US" xlink:label="abio_DirectOfferingMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Direct offering.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_DirectOfferingMember" xlink:to="abio_DirectOfferingMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_DirectOfferingMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Direct Offering</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DirectOfferingMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Direct Offering [Member]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_CapitalOnDemandSalesAgreementMember" xlink:type="locator" xlink:label="abio_CapitalOnDemandSalesAgreementMember" />
    <link:label xml:lang="en-US" xlink:label="abio_CapitalOnDemandSalesAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Capital on demand sales agreement.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_CapitalOnDemandSalesAgreementMember" xlink:to="abio_CapitalOnDemandSalesAgreementMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_CapitalOnDemandSalesAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sales Agreement</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CapitalOnDemandSalesAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Capital On Demand Sales Agreement [Member]</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:type="locator" xlink:label="dei_LegalEntityAxis" />
    <link:label xml:lang="en-US" xlink:label="dei_LegalEntityAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Legal Entity</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_LegalEntityAxis" xlink:to="dei_LegalEntityAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_LegalEntityAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Legal Entity [Axis]</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:type="locator" xlink:label="dei_EntityDomain" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityDomain" xlink:to="dei_EntityDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity [Domain]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_JonesTradingInstitutionalServicesLLCMember" xlink:type="locator" xlink:label="abio_JonesTradingInstitutionalServicesLLCMember" />
    <link:label xml:lang="en-US" xlink:label="abio_JonesTradingInstitutionalServicesLLCMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">JonesTrading Institutional Services LLC.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_JonesTradingInstitutionalServicesLLCMember" xlink:to="abio_JonesTradingInstitutionalServicesLLCMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_JonesTradingInstitutionalServicesLLCMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">JonesTrading</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_JonesTradingInstitutionalServicesLLCMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Jones Trading Institutional Services L L C [Member]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingAndWarrantsLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Financing And Warrants [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_EquityFinancingAndWarrantsLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Equity Financing And Warrants [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock issued</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" xlink:to="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares Issued For Services</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SaleOfStockPricePerShare" xlink:type="locator" xlink:label="us-gaap_SaleOfStockPricePerShare" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase price per share</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SaleOfStockPricePerShare" xlink:to="us-gaap_SaleOfStockPricePerShare_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sale Of Stock Price Per Share</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:type="locator" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-funded warrants to purchase shares of common stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:to="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:type="locator" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase price per warrant</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:to="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightOutstanding" xlink:type="locator" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-funded warrants outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightOutstanding" xlink:to="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right Outstanding</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/positiveVerboseLabel">Net proceeds from issuance of common stock</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_SellingCommissionPerAdditionalSharesSoldPercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of selling commission per additional shares sold</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_SellingCommissionPerAdditionalSharesSoldPercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Selling Commission Per Additional Shares Sold Percentage</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_CommonStockAuthorizedOfferingAmountUnderAgreementToSell" xlink:type="locator" xlink:label="abio_CommonStockAuthorizedOfferingAmountUnderAgreementToSell" />
    <link:label xml:lang="en-US" xlink:label="abio_CommonStockAuthorizedOfferingAmountUnderAgreementToSell_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock, authorized offering amount under agreement to sell.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_CommonStockAuthorizedOfferingAmountUnderAgreementToSell" xlink:to="abio_CommonStockAuthorizedOfferingAmountUnderAgreementToSell_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_CommonStockAuthorizedOfferingAmountUnderAgreementToSell_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate offering price of common stock authorized</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_CommonStockAuthorizedOfferingAmountUnderAgreementToSell_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Authorized Offering Amount Under Agreement To Sell</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_NetProceedsFromIssuanceOfCommonStock" xlink:type="locator" xlink:label="abio_NetProceedsFromIssuanceOfCommonStock" />
    <link:label xml:lang="en-US" xlink:label="abio_NetProceedsFromIssuanceOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">The cash inflow associated with the amount received from entity&apos;s raising of capital, net of related financing costs.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_NetProceedsFromIssuanceOfCommonStock" xlink:to="abio_NetProceedsFromIssuanceOfCommonStock_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_NetProceedsFromIssuanceOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net proceeds from issuance of common stock</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_NetProceedsFromIssuanceOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Proceeds From Issuance Of Common Stock</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Sale of common stock</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_WarrantsExpirationYear" xlink:type="locator" xlink:label="abio_WarrantsExpirationYear" />
    <link:label xml:lang="en-US" xlink:label="abio_WarrantsExpirationYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Year during which outstanding warrants of company stock will expire.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_WarrantsExpirationYear" xlink:to="abio_WarrantsExpirationYear_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" xlink:label="us-gaap_ClassOfWarrantOrRightTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class Of Warrant Or Right [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightTable" xlink:to="us-gaap_ClassOfWarrantOrRightTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" xlink:label="us-gaap_ClassOfWarrantOrRightAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Warrant or Right</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightAxis" xlink:to="us-gaap_ClassOfWarrantOrRightAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" xlink:label="us-gaap_ClassOfWarrantOrRightDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Warrant or Right</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="us-gaap_ClassOfWarrantOrRightDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right [Domain]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_WarrantExpirationTwoThousandAndTwentyTwoMember" xlink:type="locator" xlink:label="abio_WarrantExpirationTwoThousandAndTwentyTwoMember" />
    <link:label xml:lang="en-US" xlink:label="abio_WarrantExpirationTwoThousandAndTwentyTwoMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrant expiration two thousand and twenty two.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_WarrantExpirationTwoThousandAndTwentyTwoMember" xlink:to="abio_WarrantExpirationTwoThousandAndTwentyTwoMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_WarrantExpirationTwoThousandAndTwentyTwoMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_WarrantExpirationTwoThousandAndTwentyTwoMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Warrant Expiration Two Thousand And Twenty Two [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" xlink:label="us-gaap_ClassOfWarrantOrRightLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class Of Warrant Or Right [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_WarrantsExpirationYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Year of Expiration</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_WarrantsExpirationYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Warrants Expiration Year</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Number of Warrants</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted Average Exercise Price</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:type="locator" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameAxis" xlink:type="locator" xlink:label="us-gaap_PlanNameAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain" xlink:type="locator" xlink:label="us-gaap_PlanNameDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameDomain" xlink:to="us-gaap_PlanNameDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Domain]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_TwoThousandAndTwentyEquityIncentivePlanMember" xlink:type="locator" xlink:label="abio_TwoThousandAndTwentyEquityIncentivePlanMember" />
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndTwentyEquityIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand and twenty equity incentive plan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_TwoThousandAndTwentyEquityIncentivePlanMember" xlink:to="abio_TwoThousandAndTwentyEquityIncentivePlanMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndTwentyEquityIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Equity Incentive Plan</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndTwentyEquityIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand And Twenty Equity Incentive Plan [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis" xlink:type="locator" xlink:label="srt_RangeAxis" />
    <link:label xml:lang="en-US" xlink:label="srt_RangeAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeAxis" xlink:to="srt_RangeAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="srt_RangeAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Range [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember" xlink:type="locator" xlink:label="srt_RangeMember" />
    <link:label xml:lang="en-US" xlink:label="srt_RangeMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeMember" xlink:to="srt_RangeMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="srt_RangeMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Range [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember" xlink:type="locator" xlink:label="srt_MinimumMember" />
    <link:label xml:lang="en-US" xlink:label="srt_MinimumMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MinimumMember" xlink:to="srt_MinimumMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="srt_MinimumMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember" xlink:type="locator" xlink:label="srt_MaximumMember" />
    <link:label xml:lang="en-US" xlink:label="srt_MaximumMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MaximumMember" xlink:to="srt_MaximumMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="srt_MaximumMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis" xlink:type="locator" xlink:label="us-gaap_AwardTypeAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AwardTypeAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Award Type</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_AwardTypeAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AwardTypeAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Award Type [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Award Type</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_IncentiveStockOptionMember" xlink:type="locator" xlink:label="abio_IncentiveStockOptionMember" />
    <link:label xml:lang="en-US" xlink:label="abio_IncentiveStockOptionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive stock option.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_IncentiveStockOptionMember" xlink:to="abio_IncentiveStockOptionMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_IncentiveStockOptionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive Stock Option</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IncentiveStockOptionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Stock Option [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrincipalOwnerMember" xlink:type="locator" xlink:label="us-gaap_PrincipalOwnerMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PrincipalOwnerMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PrincipalOwnerMember" xlink:to="us-gaap_PrincipalOwnerMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PrincipalOwnerMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Principal Owner [Member]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_TwoThousandAndThirteenPlanMember" xlink:type="locator" xlink:label="abio_TwoThousandAndThirteenPlanMember" />
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndThirteenPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand and thirteen plan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_TwoThousandAndThirteenPlanMember" xlink:to="abio_TwoThousandAndThirteenPlanMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndThirteenPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2013 Plan</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndThirteenPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand And Thirteen Plan [Member]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_TwoThousandAndFourStockOptionPlanMember" xlink:type="locator" xlink:label="abio_TwoThousandAndFourStockOptionPlanMember" />
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndFourStockOptionPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">2004 Stock Option Plan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_TwoThousandAndFourStockOptionPlanMember" xlink:to="abio_TwoThousandAndFourStockOptionPlanMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndFourStockOptionPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2004 Plan</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_TwoThousandAndFourStockOptionPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand And Four Stock Option Plan [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:type="locator" xlink:label="us-gaap_EmployeeStockOptionMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeStockOptionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Stock Option</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeStockOptionMember" xlink:to="us-gaap_EmployeeStockOptionMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeStockOptionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock Option [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of shares issuable under Equity plan</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of shares outstanding under Equity plan</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average exercise Price of Options Outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:type="locator" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares reserved for future</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:to="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Capital Shares Reserved For Future Issuance</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_PercentageHoldingForStockOptionsExercisePrice" xlink:type="locator" xlink:label="abio_PercentageHoldingForStockOptionsExercisePrice" />
    <link:label xml:lang="en-US" xlink:label="abio_PercentageHoldingForStockOptionsExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum ownership percentage for 110% fair market value on the grant date.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_PercentageHoldingForStockOptionsExercisePrice" xlink:to="abio_PercentageHoldingForStockOptionsExercisePrice_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options award, vesting period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options award, expiration</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sharebased Compensation Arrangement By Sharebased Payment Award Expiration Period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of exercise price of stock option</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sharebased Compensation Arrangement By Sharebased Payment Award Purchase Price Of Common Stock Percent</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_PercentageHoldingForStockOptionsExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage holding for stock options exercise price</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_PercentageHoldingForStockOptionsExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Holding For Stock Options Exercise Price</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Options granted</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Shares Issued In Period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated weighted average grant date fair value per share</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected term</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected volatility</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Risk-free interest rate</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected dividend yield</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average grant date fair value per share</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of Stock Options</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Number of Options, Options outstanding, beginning of period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of Options, Granted</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Number of Options, Exercised</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares Stock Options Exercised</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Number of Options, Forfeited and cancelled</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Number of Options, Options outstanding, end of period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of Options, Options exercisable, end of period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of Options, Options vested and expected to vest</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Number</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock Options, Weighted Average Exercise Price</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Rollforward</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Weighted Average Exercise Price, Options outstanding, beginning of period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Exercise Price, Granted</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average exercise Price, Exercised</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Exercise Price, Forfeited and cancelled</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Weighted Average Exercise Price, Options outstanding, end of period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Exercise Price, Options exercisable, end of period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Exercise Price, Options vested and expected to vest, end of period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Exercise Price</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock Options, Weighted Average Remaining Contractual Term</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Remaining Contractual Term (in years), Options outstanding</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Remaining Contractual Term (in years), Options exercisable</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Remaining Contractual Term (in years), Options vested and expected to vest</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term1</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" xlink:type="locator" xlink:label="abio_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" />
    <link:label xml:lang="en-US" xlink:label="abio_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Share based compensation arrangement by share based payment award options aggregate intrinsic value abstract.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" xlink:to="abio_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Options, Aggregate Intrinsic Value</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Aggregate Intrinsic Value [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate intrinsic value, Options Outstanding, end of period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate intrinsic value, Options exercisable, end of period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate intrinsic value, Options vested and expected to vest, end of period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Aggregate Intrinsic Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" xlink:type="locator" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrecognized compensation expense related to unvested options</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Stock Options</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:type="locator" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturity period of weighted average period of compensation expenses</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:type="locator" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Research and development</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">General and administrative</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:type="locator" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:type="locator" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total expenses</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AllocatedShareBasedCompensationExpense" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Allocated Share Based Compensation Expense</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanTable" xlink:type="locator" xlink:label="us-gaap_DefinedContributionPlanTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Defined Contribution Plan [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedContributionPlanTable" xlink:to="us-gaap_DefinedContributionPlanTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Defined Contribution Plan [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanNameAxis" xlink:type="locator" xlink:label="us-gaap_RetirementPlanNameAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RetirementPlanNameAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Retirement Plan Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetirementPlanNameAxis" xlink:to="us-gaap_RetirementPlanNameAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RetirementPlanNameAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Retirement Plan Name [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanNameDomain" xlink:type="locator" xlink:label="us-gaap_RetirementPlanNameDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RetirementPlanNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Retirement Plan Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetirementPlanNameDomain" xlink:to="us-gaap_RetirementPlanNameDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RetirementPlanNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Retirement Plan Name [Domain]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_FirstThreePercentPayContributionMember" xlink:type="locator" xlink:label="abio_FirstThreePercentPayContributionMember" />
    <link:label xml:lang="en-US" xlink:label="abio_FirstThreePercentPayContributionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">First three percent pay contribution.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_FirstThreePercentPayContributionMember" xlink:to="abio_FirstThreePercentPayContributionMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_FirstThreePercentPayContributionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First 3% of pay contributed</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_FirstThreePercentPayContributionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">First Three Percent Pay Contribution [Member]</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_NextTwoPercentPayContributionMember" xlink:type="locator" xlink:label="abio_NextTwoPercentPayContributionMember" />
    <link:label xml:lang="en-US" xlink:label="abio_NextTwoPercentPayContributionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Next two percent pay contribution.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_NextTwoPercentPayContributionMember" xlink:to="abio_NextTwoPercentPayContributionMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_NextTwoPercentPayContributionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Next 2% of pay contributed</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_NextTwoPercentPayContributionMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Next Two Percent Pay Contribution [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanDisclosureLineItems" xlink:type="locator" xlink:label="us-gaap_DefinedContributionPlanDisclosureLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanDisclosureLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Defined Contribution Plan Disclosure [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedContributionPlanDisclosureLineItems" xlink:to="us-gaap_DefinedContributionPlanDisclosureLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanDisclosureLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Defined Contribution Plan Disclosure [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans" xlink:type="locator" xlink:label="us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Matching contribution</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans" xlink:to="us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Description Of Defined Contribution Pension And Other Postretirement Plans</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch" xlink:type="locator" xlink:label="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Benefit Plan, Percentage of Match</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch" xlink:to="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Defined Contribution Plan Employer Matching Contribution Percent Of Match</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent" xlink:type="locator" xlink:label="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employer matching contribution percentage</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent" xlink:to="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Defined Contribution Plan Employer Matching Contribution Percent</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanCostRecognized" xlink:type="locator" xlink:label="us-gaap_DefinedContributionPlanCostRecognized" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanCostRecognized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company&apos;s contribution</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedContributionPlanCostRecognized" xlink:to="us-gaap_DefinedContributionPlanCostRecognized_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DefinedContributionPlanCostRecognized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Defined Contribution Plan Cost Recognized</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_OperatingLossCarryforwardsExpirationYear" xlink:type="locator" xlink:label="abio_OperatingLossCarryforwardsExpirationYear" />
    <link:label xml:lang="en-US" xlink:label="abio_OperatingLossCarryforwardsExpirationYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Operating loss carryforwards expiration year.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_OperatingLossCarryforwardsExpirationYear" xlink:to="abio_OperatingLossCarryforwardsExpirationYear_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_IncomeTaxLineItems" xlink:type="locator" xlink:label="abio_IncomeTaxLineItems" />
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Income tax.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_IncomeTaxLineItems" xlink:to="abio_IncomeTaxLineItems_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_IncomeTaxTable" xlink:type="locator" xlink:label="abio_IncomeTaxTable" />
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Income Tax.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_IncomeTaxTable" xlink:to="abio_IncomeTaxTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Tax [Table]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodAxis" xlink:type="locator" xlink:label="us-gaap_TaxPeriodAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxPeriodAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax Period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxPeriodAxis" xlink:to="us-gaap_TaxPeriodAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxPeriodAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Tax Period [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxPeriodDomain" xlink:type="locator" xlink:label="us-gaap_TaxPeriodDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxPeriodDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax Period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxPeriodDomain" xlink:to="us-gaap_TaxPeriodDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxPeriodDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Tax Period [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarliestTaxYearMember" xlink:type="locator" xlink:label="us-gaap_EarliestTaxYearMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarliestTaxYearMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earliest Tax Year</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarliestTaxYearMember" xlink:to="us-gaap_EarliestTaxYearMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarliestTaxYearMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Earliest Tax Year [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LatestTaxYearMember" xlink:type="locator" xlink:label="us-gaap_LatestTaxYearMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LatestTaxYearMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Latest Tax Year</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LatestTaxYearMember" xlink:to="us-gaap_LatestTaxYearMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LatestTaxYearMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Latest Tax Year [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardAxis" xlink:type="locator" xlink:label="us-gaap_TaxCreditCarryforwardAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax Credit Carryforward</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardAxis" xlink:to="us-gaap_TaxCreditCarryforwardAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardNameDomain" xlink:type="locator" xlink:label="us-gaap_TaxCreditCarryforwardNameDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax Credit Carryforward, Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardNameDomain" xlink:to="us-gaap_TaxCreditCarryforwardNameDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward Name [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchMember" xlink:type="locator" xlink:label="us-gaap_ResearchMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research Tax Credit Carryforward</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchMember" xlink:to="us-gaap_ResearchMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ResearchMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Research [Member]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Tax [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLossCarryforwards" xlink:type="locator" xlink:label="us-gaap_OperatingLossCarryforwards" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLossCarryforwards_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net operating loss carryforwards</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLossCarryforwards" xlink:to="us-gaap_OperatingLossCarryforwards_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLossCarryforwards_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Loss Carryforwards</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardAmount" xlink:type="locator" xlink:label="us-gaap_TaxCreditCarryforwardAmount" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and experimentation credits</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardAmount" xlink:to="us-gaap_TaxCreditCarryforwardAmount_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward Amount</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardDescription" xlink:type="locator" xlink:label="us-gaap_TaxCreditCarryforwardDescription" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardDescription_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax Credit Carryforward, Description</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardDescription" xlink:to="us-gaap_TaxCreditCarryforwardDescription_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardDescription_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward Description</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_OperatingLossCarryforwardsExpirationYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating loss carryforwards expiration year</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_OperatingLossCarryforwardsExpirationYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Loss Carryforwards Expiration Year</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLossCarryforwardsLimitationsOnUse" xlink:type="locator" xlink:label="us-gaap_OperatingLossCarryforwardsLimitationsOnUse" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLossCarryforwardsLimitationsOnUse_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating loss carryforwards, limitations on use</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLossCarryforwardsLimitationsOnUse" xlink:to="us-gaap_OperatingLossCarryforwardsLimitationsOnUse_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLossCarryforwardsLimitationsOnUse_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Loss Carryforwards Limitations On Use</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardLimitationsOnUse" xlink:type="locator" xlink:label="us-gaap_TaxCreditCarryforwardLimitationsOnUse" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardLimitationsOnUse_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax credit carryforward, limitations on use</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardLimitationsOnUse" xlink:to="us-gaap_TaxCreditCarryforwardLimitationsOnUse_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TaxCreditCarryforwardLimitationsOnUse_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward Limitations On Use</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_ValuationAllowanceDeferredTaxAssetsAndLiabilitiesChangeInAmount" xlink:type="locator" xlink:label="abio_ValuationAllowanceDeferredTaxAssetsAndLiabilitiesChangeInAmount" />
    <link:label xml:lang="en-US" xlink:label="abio_ValuationAllowanceDeferredTaxAssetsAndLiabilitiesChangeInAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Valuation allowance deferred tax assets and liabilities change in amount.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_ValuationAllowanceDeferredTaxAssetsAndLiabilitiesChangeInAmount" xlink:to="abio_ValuationAllowanceDeferredTaxAssetsAndLiabilitiesChangeInAmount_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_DeferredTaxAssetsLiabilitiesNetIncreaseDecrease" xlink:type="locator" xlink:label="abio_DeferredTaxAssetsLiabilitiesNetIncreaseDecrease" />
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsLiabilitiesNetIncreaseDecrease_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax assets liabilities, net, increase (decrease).</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_DeferredTaxAssetsLiabilitiesNetIncreaseDecrease" xlink:to="abio_DeferredTaxAssetsLiabilitiesNetIncreaseDecrease_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_DeferredTaxAssetsAndLiabilitiesValuationAllowance" xlink:type="locator" xlink:label="abio_DeferredTaxAssetsAndLiabilitiesValuationAllowance" />
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsAndLiabilitiesValuationAllowance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax assets and liabilities valuation allowance.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_DeferredTaxAssetsAndLiabilitiesValuationAllowance" xlink:to="abio_DeferredTaxAssetsAndLiabilitiesValuationAllowance_lbl" />
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsAndLiabilitiesValuationAllowance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Valuation allowance</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsAndLiabilitiesValuationAllowance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets And Liabilities Valuation Allowance</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_ValuationAllowanceDeferredTaxAssetsAndLiabilitiesChangeInAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase in net deferred tax assets and liabilities</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_ValuationAllowanceDeferredTaxAssetsAndLiabilitiesChangeInAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Allowance Deferred Tax Assets And Liabilities Change In Amount</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsLiabilitiesNetIncreaseDecrease_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Decrease in deferred tax assets and liabilities</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsLiabilitiesNetIncreaseDecrease_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Liabilities Net Increase Decrease</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" xlink:type="locator" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Federal statutory income tax rate</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" xlink:to="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_IncomeTaxReconciliationAdjustmentToDeferredTaxAsset" xlink:type="locator" xlink:label="abio_IncomeTaxReconciliationAdjustmentToDeferredTaxAsset" />
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxReconciliationAdjustmentToDeferredTaxAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Adjustment of the carrying value of deferred tax assets during the year.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_IncomeTaxReconciliationAdjustmentToDeferredTaxAsset" xlink:to="abio_IncomeTaxReconciliationAdjustmentToDeferredTaxAsset_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationAbstract" xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effective Income Tax Rate Reconciliation, Amount [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationAbstract" xlink:to="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. federal income tax benefit at statutory rates</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" xlink:to="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">State income tax benefit, net of federal benefit</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" xlink:to="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Reconciliation State And Local Income Taxes</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in state tax rate</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate" xlink:to="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Reconciliation Change In Enacted Tax Rate</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationTaxCreditsResearch" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationTaxCreditsResearch" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationTaxCreditsResearch_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Research and experimentation credits</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationTaxCreditsResearch" xlink:to="us-gaap_IncomeTaxReconciliationTaxCreditsResearch_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationTaxCreditsResearch_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Reconciliation Tax Credits Research</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxReconciliationAdjustmentToDeferredTaxAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax asset adjustment</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_IncomeTaxReconciliationAdjustmentToDeferredTaxAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Reconciliation Adjustment To Deferred Tax Asset</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationOtherAdjustments" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationOtherAdjustments" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationOtherAdjustments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationOtherAdjustments" xlink:to="us-gaap_IncomeTaxReconciliationOtherAdjustments_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationOtherAdjustments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Reconciliation Other Adjustments</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance" xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in valuation allowance</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance" xlink:to="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income tax benefit</link:label>
    <link:loc xlink:href="abio-20201231.xsd#abio_DeferredTaxAssetsLeaseLiabilities" xlink:type="locator" xlink:label="abio_DeferredTaxAssetsLeaseLiabilities" />
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsLeaseLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from lease liabilities.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_DeferredTaxAssetsLeaseLiabilities" xlink:to="abio_DeferredTaxAssetsLeaseLiabilities_lbl" />
    <link:loc xlink:href="abio-20201231.xsd#abio_DeferredTaxLiabilitiesRightOfUseAsset" xlink:type="locator" xlink:label="abio_DeferredTaxLiabilitiesRightOfUseAsset" />
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxLiabilitiesRightOfUseAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Amount of deferred tax liability attributable to taxable temporary differences from right of use assets.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="abio_DeferredTaxLiabilitiesRightOfUseAsset" xlink:to="abio_DeferredTaxLiabilitiesRightOfUseAsset_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsNetOfValuationAllowanceAbstract" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsNetOfValuationAllowanceAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsNetOfValuationAllowanceAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax assets:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsNetOfValuationAllowanceAbstract" xlink:to="us-gaap_DeferredTaxAssetsNetOfValuationAllowanceAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsNetOfValuationAllowanceAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Net Of Valuation Allowance [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net operating loss carryforwards</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration" xlink:to="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Operating Loss Carryforwards Subject To Expiration</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Charitable contribution carryforwards</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards" xlink:to="us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Charitable Contribution Carryforwards</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and experimentation credits</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch" xlink:to="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Tax Credit Carryforwards Research</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capitalized intangibles</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets" xlink:to="us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Goodwill And Intangible Assets</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Depreciation and amortization</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment" xlink:to="us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Property Plant And Equipment</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued compensation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Tax Deferred Expense Compensation And Benefits</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsLeaseLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease liabilities</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxAssetsLeaseLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Lease Liabilities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOther" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsOther" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsOther_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsOther" xlink:to="us-gaap_DeferredTaxAssetsOther_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsOther_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Other</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsGross" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsGross" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total deferred tax assets</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsGross_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Gross</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Valuation allowance</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsValuationAllowance" xlink:to="us-gaap_DeferredTaxAssetsValuationAllowance_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Valuation Allowance</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsNet" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsNet" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred tax assets, net of valuation allowance</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsNet" xlink:to="us-gaap_DeferredTaxAssetsNet_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Net</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxLiabilitiesAbstract" xlink:type="locator" xlink:label="us-gaap_DeferredTaxLiabilitiesAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxLiabilitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax liabilities:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxLiabilitiesAbstract" xlink:to="us-gaap_DeferredTaxLiabilitiesAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxLiabilitiesAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Liabilities [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxLiabilitiesRightOfUseAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Right-of-use asset</link:label>
    <link:label xml:lang="en-US" xlink:label="abio_DeferredTaxLiabilitiesRightOfUseAsset_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Liabilities Right Of Use Asset</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net deferred tax liability</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:to="us-gaap_DeferredTaxAssetsLiabilitiesNet_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets Liabilities Net</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilityForUncertainTaxPositionsCurrent" xlink:type="locator" xlink:label="us-gaap_LiabilityForUncertainTaxPositionsCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilityForUncertainTaxPositionsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reserve for uncertain tax positions</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilityForUncertainTaxPositionsCurrent" xlink:to="us-gaap_LiabilityForUncertainTaxPositionsCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LiabilityForUncertainTaxPositionsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Liability For Uncertain Tax Positions Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense" xlink:type="locator" xlink:label="us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest or penalties recognized</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense" xlink:to="us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Examination Penalties And Interest Expense</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OpenTaxYear" xlink:type="locator" xlink:label="us-gaap_OpenTaxYear" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OpenTaxYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Open tax year</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OpenTaxYear" xlink:to="us-gaap_OpenTaxYear_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OpenTaxYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Open Tax Year</link:label>
  </link:labelLink>
</link:linkbase>
