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<!-- DFIN ActiveDisclosure(SM) XBRL Linkbase Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2019-08-14T18:38:48.3387812+00:00 -->
<!-- Version            : 3.6.7150.26138 -->
<!-- Package ID         : 3de9e78ae2844603a0723d9616cb7cfa -->
<!-- Copyright (c) 2019 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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    <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>
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    <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>
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    <link:label xml:lang="en-US" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Period Focus</link:label>
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    <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/2018/dei-2018-01-31.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>
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    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd#dei_EntityRegistrantName" xlink:type="locator" xlink:label="dei_EntityRegistrantName" />
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    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.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>
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    <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>
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    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.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>
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    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.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>
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    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.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>
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    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.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/terseLabel">Entity Common Stock, Shares Outstanding</link:label>
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    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.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>
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    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.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>
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    <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/2018/dei-2018-01-31.xsd#dei_EntityExTransitionPeriod" xlink:type="locator" xlink:label="dei_EntityExTransitionPeriod" />
    <link:label xml:lang="en-US" xlink:label="dei_EntityExTransitionPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Ex Transition Period</link:label>
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    <link:label xml:lang="en-US" xlink:label="dei_EntityExTransitionPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Entity Ex Transition Period</link:label>
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2018/dei-2018-01-31.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>
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    <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/2018/dei-2018-01-31.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>
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    <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>
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    <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>
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    <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/2018/elts/us-gaap-2018-01-31.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 (Note 5)</link:label>
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    <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/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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</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/2018/elts/us-gaap-2018-01-31.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</link:label>
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    <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/2018/elts/us-gaap-2018-01-31.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>
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    <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/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TreasuryStockValue" xlink:type="locator" xlink:label="us-gaap_TreasuryStockValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Treasury stock</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockValue" xlink:to="us-gaap_TreasuryStockValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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>
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    <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/2018/elts/us-gaap-2018-01-31.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>
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    <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>
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    <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, shares issued</link:label>
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    <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>
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    <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, shares outstanding</link:label>
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    <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>
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    <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>
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    <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>
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    <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>
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    <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>
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    <link:loc xlink:href="dtil-20190630.xsd#dtil_ChangeInFairValueOfConvertibleNotePayable" xlink:type="locator" xlink:label="dtil_ChangeInFairValueOfConvertibleNotePayable" />
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    <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>
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    <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>
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    <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 operating expenses</link:label>
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    <link:label xml:lang="en-US" xlink:label="dtil_IssuanceOfCommonStockInInitialPublicOfferingNetOfUnderwritingDiscountsAndIssuanceCostShares_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock in initial public offering, net of discounts and issuance costs, shares</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_IssuanceOfCommonStockInInitialPublicOfferingNetOfUnderwritingDiscountsAndIssuanceCostShares_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock In Initial Public Offering Net Of Underwriting Discounts And Issuance Cost Shares</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock option exercises</link:label>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value Stock Options Exercised</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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/2003/role/terseLabel">Stock option exercises, Shares</link:label>
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    <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/2018/elts/us-gaap-2018-01-31.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 expense</link:label>
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    <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>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance, Shares</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_NonCashInterestExpense" xlink:type="locator" xlink:label="dtil_NonCashInterestExpense" />
    <link:label xml:lang="en-US" xlink:label="dtil_NonCashInterestExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-cash interest expense.</link:label>
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    <link:loc xlink:href="dtil-20190630.xsd#dtil_ChangeInFairValueOfConvertibleNotesPayable" xlink:type="locator" xlink:label="dtil_ChangeInFairValueOfConvertibleNotesPayable" />
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    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_ChangeInFairValueOfConvertibleNotesPayable" xlink:to="dtil_ChangeInFairValueOfConvertibleNotesPayable_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_CommonStockIssuedOnConversionOfConvertibleNotes" xlink:type="locator" xlink:label="dtil_CommonStockIssuedOnConversionOfConvertibleNotes" />
    <link:label xml:lang="en-US" xlink:label="dtil_CommonStockIssuedOnConversionOfConvertibleNotes_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock issued on conversion of convertible notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_CommonStockIssuedOnConversionOfConvertibleNotes" xlink:to="dtil_CommonStockIssuedOnConversionOfConvertibleNotes_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_ConvertiblePreferredStockOfferingCostsIncludedInAccountsPayableAccruedExpensesAndOtherCurrentLiabilities" xlink:type="locator" xlink:label="dtil_ConvertiblePreferredStockOfferingCostsIncludedInAccountsPayableAccruedExpensesAndOtherCurrentLiabilities" />
    <link:label xml:lang="en-US" xlink:label="dtil_ConvertiblePreferredStockOfferingCostsIncludedInAccountsPayableAccruedExpensesAndOtherCurrentLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Series B convertible preferred stock offering costs included in accounts payable, accrued expenses and other current liabilities.</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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>
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    <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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProfitLoss" xlink:type="locator" xlink:label="us-gaap_ProfitLoss" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProfitLoss_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net loss</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_ProfitLoss_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProfitLoss_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Profit Loss</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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>
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    <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/2018/elts/us-gaap-2018-01-31.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 and amortization</link:label>
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    <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/2018/elts/us-gaap-2018-01-31.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>
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    <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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GainsLossesOnSalesOfAssets" xlink:type="locator" xlink:label="us-gaap_GainsLossesOnSalesOfAssets" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_GainsLossesOnSalesOfAssets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Loss on disposal of assets</link:label>
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    <link:label xml:lang="en-US" xlink:label="dtil_NonCashInterestExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Non Cash Interest Expense</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ChangeInFairValueOfConvertibleNotesPayable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in fair value of convertible notes payable</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ChangeInFairValueOfConvertibleNotesPayable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Change In Fair Value Of Convertible Notes Payable</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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">Changes in operating assets and liabilities:</link:label>
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    <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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidExpense" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInPrepaidExpense" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInPrepaidExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expenses</link:label>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInPrepaidExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Prepaid Expense</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accounts receivable</link:label>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accounts Receivable</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other assets</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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>
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    <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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilities" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued expenses</link:label>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accrued Liabilities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue</link:label>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Contract With Customer Liability</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
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    <link:loc xlink:href="dtil-20190630.xsd#dtil_PrecisionPlantSciencesIncMember" xlink:type="locator" xlink:label="dtil_PrecisionPlantSciencesIncMember" />
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    <link:loc xlink:href="dtil-20190630.xsd#dtil_SeriesAAndSeriesBConvertiblePreferredStockMember" xlink:type="locator" xlink:label="dtil_SeriesAAndSeriesBConvertiblePreferredStockMember" />
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    <link:loc xlink:href="dtil-20190630.xsd#dtil_UnderwritingDiscountsAndCommission" xlink:type="locator" xlink:label="dtil_UnderwritingDiscountsAndCommission" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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">Shares issued and sold, public offering price</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:label xml:lang="en-US" xlink:label="us-gaap_ProceedsFromIssuanceInitialPublicOffering_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Gross proceeds from issuance of common stock</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_UnderwritingDiscountsAndCommission_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underwriting discount and commission</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_UnderwritingDiscountsAndCommission_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Underwriting Discounts And Commission</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_PaymentsOfStockIssuanceCosts_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">issuance costs</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquityReverseStockSplit" xlink:type="locator" xlink:label="us-gaap_StockholdersEquityReverseStockSplit" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockholdersEquityReverseStockSplit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders&apos; equity, reverse stock split</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityReverseStockSplit" xlink:to="us-gaap_StockholdersEquityReverseStockSplit_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockholdersEquityReverseStockSplit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders Equity Reverse Stock Split</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable" xlink:type="locator" xlink:label="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue Initial Application Period Cumulative Effect Transition [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable" xlink:to="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Initial Application Period Cumulative Effect Transition [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member" xlink:type="locator" xlink:label="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Balances without adoption of ASC 606</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member" xlink:to="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Calculated Under Revenue Guidance In Effect Before Topic606 [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems" xlink:type="locator" xlink:label="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue Initial Application Period Cumulative Effect Transition [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems" xlink:to="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Initial Application Period Cumulative Effect Transition [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInPrepaidExpense_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Changes in prepaid expenses</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Changes in deferred revenue</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRevenueRevenueRecognized1" xlink:type="locator" xlink:label="us-gaap_DeferredRevenueRevenueRecognized1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredRevenueRevenueRecognized1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue recorded included in deferred revenue</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRevenueRevenueRecognized1" xlink:to="us-gaap_DeferredRevenueRevenueRecognized1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredRevenueRevenueRecognized1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Revenue Revenue Recognized1</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_AccruedClinicalAndResearchAndDevelopmentExpenseCurrent" xlink:type="locator" xlink:label="dtil_AccruedClinicalAndResearchAndDevelopmentExpenseCurrent" />
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedClinicalAndResearchAndDevelopmentExpenseCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued research and development expense, current.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_AccruedClinicalAndResearchAndDevelopmentExpenseCurrent" xlink:to="dtil_AccruedClinicalAndResearchAndDevelopmentExpenseCurrent_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_AccruedPropertyEquipmentAndSoftwarePurchasesCurrent" xlink:type="locator" xlink:label="dtil_AccruedPropertyEquipmentAndSoftwarePurchasesCurrent" />
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedPropertyEquipmentAndSoftwarePurchasesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued property equipment and software purchases, current.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_AccruedPropertyEquipmentAndSoftwarePurchasesCurrent" xlink:to="dtil_AccruedPropertyEquipmentAndSoftwarePurchasesCurrent_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_AccruedDeferredOfferingCostsCurrent" xlink:type="locator" xlink:label="dtil_AccruedDeferredOfferingCostsCurrent" />
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedDeferredOfferingCostsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued deferred offering costs, current.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_AccruedDeferredOfferingCostsCurrent" xlink:to="dtil_AccruedDeferredOfferingCostsCurrent_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_AccruedPropertyAndFranchiseTaxesCurrent" xlink:type="locator" xlink:label="dtil_AccruedPropertyAndFranchiseTaxesCurrent" />
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedPropertyAndFranchiseTaxesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued property and franchise taxes current.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_AccruedPropertyAndFranchiseTaxesCurrent" xlink:to="dtil_AccruedPropertyAndFranchiseTaxesCurrent_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_AccruedExpensesAndOtherLiabilitiesCurrent" xlink:type="locator" xlink:label="dtil_AccruedExpensesAndOtherLiabilitiesCurrent" />
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedExpensesAndOtherLiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued expenses and other liabilities, current.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_AccruedExpensesAndOtherLiabilitiesCurrent" xlink:to="dtil_AccruedExpensesAndOtherLiabilitiesCurrent_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccruedEmployeeBenefitsCurrent" xlink:type="locator" xlink:label="us-gaap_AccruedEmployeeBenefitsCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccruedEmployeeBenefitsCurrent_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_AccruedEmployeeBenefitsCurrent" xlink:to="us-gaap_AccruedEmployeeBenefitsCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccruedEmployeeBenefitsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Employee Benefits Current</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedClinicalAndResearchAndDevelopmentExpenseCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued clinical and research and development expenses</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedClinicalAndResearchAndDevelopmentExpenseCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Clinical And Research And Development Expense Current</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedPropertyEquipmentAndSoftwarePurchasesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued property, equipment and software purchases</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedPropertyEquipmentAndSoftwarePurchasesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Property Equipment And Software Purchases Current</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedDeferredOfferingCostsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued deferred offering costs</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedDeferredOfferingCostsCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Deferred Offering Costs Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRentCreditCurrent" xlink:type="locator" xlink:label="us-gaap_DeferredRentCreditCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredRentCreditCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred rent</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRentCreditCurrent" xlink:to="us-gaap_DeferredRentCreditCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DeferredRentCreditCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Rent Credit Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccruedProfessionalFeesCurrent" xlink:type="locator" xlink:label="us-gaap_AccruedProfessionalFeesCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccruedProfessionalFeesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued legal fees</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedProfessionalFeesCurrent" xlink:to="us-gaap_AccruedProfessionalFeesCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_AccruedProfessionalFeesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Professional Fees Current</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedPropertyAndFranchiseTaxesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued property and franchise taxes</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedPropertyAndFranchiseTaxesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Property And Franchise Taxes Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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">Other</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:label xml:lang="en-US" xlink:label="dtil_AccruedExpensesAndOtherLiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total accrued expenses and other current liabilities</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AccruedExpensesAndOtherLiabilitiesCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Expenses And Other Liabilities Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable" xlink:type="locator" xlink:label="us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsidiary Or Equity Method Investee Sale Of Stock By Subsidiary Or Equity Investee [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable" xlink:to="us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Subsidiary Or Equity Method Investee Sale Of Stock By Subsidiary Or Equity Investee [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsidiarySaleOfStockLineItems" xlink:type="locator" xlink:label="us-gaap_SubsidiarySaleOfStockLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsidiarySaleOfStockLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders&apos; Equity [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsidiarySaleOfStockLineItems" xlink:to="us-gaap_SubsidiarySaleOfStockLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_SubsidiarySaleOfStockLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Subsidiary Sale Of Stock [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/positiveVerboseLabel">Common stock issued upon conversion of convertible preferred stock or convertible promissory notes</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_CommonAndPreferredStocksSharesAuthorized" xlink:type="locator" xlink:label="dtil_CommonAndPreferredStocksSharesAuthorized" />
    <link:label xml:lang="en-US" xlink:label="dtil_CommonAndPreferredStocksSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">The maximum number of of common and preferred stock shares permitted to be issued by an entity&apos;s charter and bylaws.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_CommonAndPreferredStocksSharesAuthorized" xlink:to="dtil_CommonAndPreferredStocksSharesAuthorized_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_CommonAndPreferredStocksSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common and prferred stocks, shares authorized</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_CommonAndPreferredStocksSharesAuthorized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Common And Preferred Stocks Shares Authorized</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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="dtil-20190630.xsd#dtil_TwoThousandSixStockIncentivePlanMember" xlink:type="locator" xlink:label="dtil_TwoThousandSixStockIncentivePlanMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandSixStockIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand six stock incentive plan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_TwoThousandSixStockIncentivePlanMember" xlink:to="dtil_TwoThousandSixStockIncentivePlanMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandSixStockIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2006 Plan</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandSixStockIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Six Stock Incentive Plan [Member]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_TwoThousandFifteenStockIncentivePlanMember" xlink:type="locator" xlink:label="dtil_TwoThousandFifteenStockIncentivePlanMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandFifteenStockIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand fifteen stock incentive plan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_TwoThousandFifteenStockIncentivePlanMember" xlink:to="dtil_TwoThousandFifteenStockIncentivePlanMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandFifteenStockIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2015 Plan</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandFifteenStockIncentivePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Fifteen Stock Incentive Plan [Member]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_TwoThousandNineteenIncentiveAwardPlanMember" xlink:type="locator" xlink:label="dtil_TwoThousandNineteenIncentiveAwardPlanMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandNineteenIncentiveAwardPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand nineteen incentive award plan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_TwoThousandNineteenIncentiveAwardPlanMember" xlink:to="dtil_TwoThousandNineteenIncentiveAwardPlanMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandNineteenIncentiveAwardPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2019 Plan</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandNineteenIncentiveAwardPlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Nineteen Incentive Award Plan [Member]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_TwoThousandNineteenEmployeeStockPurchasePlanMember" xlink:type="locator" xlink:label="dtil_TwoThousandNineteenEmployeeStockPurchasePlanMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandNineteenEmployeeStockPurchasePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand nineteen employee stock purchase plan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_TwoThousandNineteenEmployeeStockPurchasePlanMember" xlink:to="dtil_TwoThousandNineteenEmployeeStockPurchasePlanMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandNineteenEmployeeStockPurchasePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2019 ESPP</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_TwoThousandNineteenEmployeeStockPurchasePlanMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Nineteen Employee Stock Purchase Plan [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remaining shares available to be granted</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_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 Available For Grant</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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">Options outstanding</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/2018/elts/us-gaap-2018-01-31.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">Common stock reserved for issuance</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="dtil-20190630.xsd#dtil_AllowedAnnualPercentageIncreaseInSharesAuthorizedAsPercentageOfOutstandingSharesOfCommonStock" xlink:type="locator" xlink:label="dtil_AllowedAnnualPercentageIncreaseInSharesAuthorizedAsPercentageOfOutstandingSharesOfCommonStock" />
    <link:label xml:lang="en-US" xlink:label="dtil_AllowedAnnualPercentageIncreaseInSharesAuthorizedAsPercentageOfOutstandingSharesOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Allowed annual percentage increase in shares authorized as percentage of outstanding shares of common stock.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_AllowedAnnualPercentageIncreaseInSharesAuthorizedAsPercentageOfOutstandingSharesOfCommonStock" xlink:to="dtil_AllowedAnnualPercentageIncreaseInSharesAuthorizedAsPercentageOfOutstandingSharesOfCommonStock_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_MaximumSharesAllowedToBeIssued" xlink:type="locator" xlink:label="dtil_MaximumSharesAllowedToBeIssued" />
    <link:label xml:lang="en-US" xlink:label="dtil_MaximumSharesAllowedToBeIssued_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Maximum shares allowed to be issued.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_MaximumSharesAllowedToBeIssued" xlink:to="dtil_MaximumSharesAllowedToBeIssued_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_AllowedAnnualPercentageIncreaseInSharesAuthorizedAsPercentageOfOutstandingSharesOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Allowed annual percentage increase in shares authorized as percentage of outstanding shares of common stock</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AllowedAnnualPercentageIncreaseInSharesAuthorizedAsPercentageOfOutstandingSharesOfCommonStock_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Allowed Annual Percentage Increase In Shares Authorized As Percentage Of Outstanding Shares Of Common Stock</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_MaximumSharesAllowedToBeIssued_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum shares of common stock may be issued</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_MaximumSharesAllowedToBeIssued_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Shares Allowed To Be Issued</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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">Stock options outstanding</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="dtil-20190630.xsd#dtil_MaximumSharesAllowedToBeIssuedUnderESPP" xlink:type="locator" xlink:label="dtil_MaximumSharesAllowedToBeIssuedUnderESPP" />
    <link:label xml:lang="en-US" xlink:label="dtil_MaximumSharesAllowedToBeIssuedUnderESPP_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Maximum shares allowed to be issued under ESPP.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_MaximumSharesAllowedToBeIssuedUnderESPP" xlink:to="dtil_MaximumSharesAllowedToBeIssuedUnderESPP_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockThroughPayrollDeductionsPercentage" xlink:type="locator" xlink:label="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockThroughPayrollDeductionsPercentage" />
    <link:label xml:lang="en-US" xlink:label="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockThroughPayrollDeductionsPercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Share based compensation arrangement by share based payment award purchase price of common stock through payroll deductions percentage.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockThroughPayrollDeductionsPercentage" xlink:to="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockThroughPayrollDeductionsPercentage_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_PurchaseRightsOutstandingUnderESPP" xlink:type="locator" xlink:label="dtil_PurchaseRightsOutstandingUnderESPP" />
    <link:label xml:lang="en-US" xlink:label="dtil_PurchaseRightsOutstandingUnderESPP_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Purchase rights outstanding under the Employee Stock Purchase Plan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_PurchaseRightsOutstandingUnderESPP" xlink:to="dtil_PurchaseRightsOutstandingUnderESPP_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_MaximumSharesAllowedToBeIssuedUnderESPP_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum shares allowed to be issued under ESPP</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_MaximumSharesAllowedToBeIssuedUnderESPP_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Shares Allowed To Be Issued Under E S P P</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockThroughPayrollDeductionsPercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase of common stock through payroll deductions expressed in percentage of fair market value</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockThroughPayrollDeductionsPercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Purchase Price Of Common Stock Through Payroll Deductions Percentage</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_PurchaseRightsOutstandingUnderESPP_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase rights outstanding under the ESPP</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_PurchaseRightsOutstandingUnderESPP_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Purchase Rights Outstanding Under E S P P</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TitleOfIndividualAxis" xlink:type="locator" xlink:label="us-gaap_TitleOfIndividualAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TitleOfIndividualAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of Individual</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TitleOfIndividualAxis" xlink:to="us-gaap_TitleOfIndividualAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TitleOfIndividualAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Title Of Individual [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:type="locator" xlink:label="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Relationship to Entity</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:to="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Title Of Individual With Relationship To Entity [Domain]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_EmployeesMember" xlink:type="locator" xlink:label="dtil_EmployeesMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_EmployeesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Employees.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_EmployeesMember" xlink:to="dtil_EmployeesMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_EmployeesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employees</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_EmployeesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Employees [Member]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_NonemployeesMember" xlink:type="locator" xlink:label="dtil_NonemployeesMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_NonemployeesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Nonemployees.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_NonemployeesMember" xlink:to="dtil_NonemployeesMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_NonemployeesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Nonemployees</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_NonemployeesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Nonemployees [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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">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_AllocatedShareBasedCompensationExpense" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense_lbl" />
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    <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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:type="locator" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember" />
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    <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" />
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    <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:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AwardTypeAxis" xlink:type="locator" xlink:label="us-gaap_AwardTypeAxis" />
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    <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>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Award</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="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:type="locator" xlink:label="us-gaap_EmployeeStockOptionMember" />
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    <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="dtil-20190630.xsd#dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValuePerOption" xlink:type="locator" xlink:label="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValuePerOption" />
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    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValuePerOption" xlink:to="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValuePerOption_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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">Estimated 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/2018/elts/us-gaap-2018-01-31.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">Weighted-average expected stock price volatility</link:label>
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    <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/2018/elts/us-gaap-2018-01-31.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">Weighted-average 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/2018/elts/us-gaap-2018-01-31.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 life of options (in years)</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:label xml:lang="en-US" xlink:label="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValuePerOption_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average fair value per option</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValuePerOption_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 Weighted Average Fair Value Per Option</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">Outstanding Option Shares, Beginning Balance</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Option, Exercised</link:label>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Option, Forfeited/canceled</link:label>
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    <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">Outstanding Option Shares, Ending Balance</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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/periodStartLabel">Weighted-Average Exercise Price Outstanding at Beginning Balance</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/2018/elts/us-gaap-2018-01-31.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>
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    <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/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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/canceled</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 Outstanding at Ending Balance</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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 cost</link:label>
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    <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/2018/elts/us-gaap-2018-01-31.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">Weighted-average period for recognition of compensation cost</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/2018/elts/us-gaap-2018-01-31.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/verboseLabel">Intrinsic value of options exercised</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/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract" xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases Future Minimum Payments Due [Abstract]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear" xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remainder of 2019</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases Future Minimum Payments Remainder Of Fiscal Year</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases Future Minimum Payments Due Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_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_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases Future Minimum Payments Due In Two Years</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_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_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases Future Minimum Payments Due In Three Years</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_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_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases Future Minimum Payments Due In Four Years</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 and beyond</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases Future Minimum Payments Due Thereafter</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_AgreementTerminationNoticePeriod" xlink:type="locator" xlink:label="dtil_AgreementTerminationNoticePeriod" />
    <link:label xml:lang="en-US" xlink:label="dtil_AgreementTerminationNoticePeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Agreement termination notice period.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_AgreementTerminationNoticePeriod" xlink:to="dtil_AgreementTerminationNoticePeriod_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_CommitmentsAndContingenciesLineItems" xlink:type="locator" xlink:label="dtil_CommitmentsAndContingenciesLineItems" />
    <link:label xml:lang="en-US" xlink:label="dtil_CommitmentsAndContingenciesLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Line items represent commitments and contingencies.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_CommitmentsAndContingenciesLineItems" xlink:to="dtil_CommitmentsAndContingenciesLineItems_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_CommitmentAndContingenciesTable" xlink:type="locator" xlink:label="dtil_CommitmentAndContingenciesTable" />
    <link:label xml:lang="en-US" xlink:label="dtil_CommitmentAndContingenciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Commitment and contingencies.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_CommitmentAndContingenciesTable" xlink:to="dtil_CommitmentAndContingenciesTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_CommitmentAndContingenciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitment And Contingencies [Table]</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_CommitmentAndContingenciesTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Commitment And Contingencies [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.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">Range</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/2018/elts/srt-2018-01-31.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">Range</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/2018/elts/srt-2018-01-31.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/srt/2018/elts/srt-2018-01-31.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 [Member]</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:label xml:lang="en-US" xlink:label="dtil_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="dtil_CommitmentsAndContingenciesLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Commitments And Contingencies [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AgreementTerminationNoticePeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Agreement termination notice period</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AgreementTerminationNoticePeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Agreement Termination Notice Period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:type="locator" xlink:label="us-gaap_DebtInstrumentTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:type="locator" xlink:label="us-gaap_CreditFacilityAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:type="locator" xlink:label="us-gaap_CreditFacilityDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_CreditFacilityDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:type="locator" xlink:label="us-gaap_RevolvingCreditFacilityMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevolvingCreditFacilityMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Line [Member]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevolvingCreditFacilityMember" xlink:to="us-gaap_RevolvingCreditFacilityMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevolvingCreditFacilityMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:type="locator" xlink:label="us-gaap_DebtInstrumentAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:type="locator" xlink:label="us-gaap_DebtInstrumentNameDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument, Name</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="us-gaap_DebtInstrumentNameDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Name [Domain]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_RevolvingLineIfDailyBalanceIsMaintainedMember" xlink:type="locator" xlink:label="dtil_RevolvingLineIfDailyBalanceIsMaintainedMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_RevolvingLineIfDailyBalanceIsMaintainedMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Member stands for revelving line if the company maintains a daily demand deposit balance requirment for the loan.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_RevolvingLineIfDailyBalanceIsMaintainedMember" xlink:to="dtil_RevolvingLineIfDailyBalanceIsMaintainedMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_RevolvingLineIfDailyBalanceIsMaintainedMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Line If Daily Balance Is Maintained [Member]</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_RevolvingLineIfDailyBalanceIsMaintainedMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Line If Daily Balance Is Maintained [Member]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_RevolvingLineIfDailyBalanceIsNotMaintainedMember" xlink:type="locator" xlink:label="dtil_RevolvingLineIfDailyBalanceIsNotMaintainedMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_RevolvingLineIfDailyBalanceIsNotMaintainedMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Member stands for revelving line if the company does not maintain a daily demand deposit balance requirment for the loan..</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_RevolvingLineIfDailyBalanceIsNotMaintainedMember" xlink:to="dtil_RevolvingLineIfDailyBalanceIsNotMaintainedMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_RevolvingLineIfDailyBalanceIsNotMaintainedMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Line If Daily Balance Is Not Maintained [Member]</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_RevolvingLineIfDailyBalanceIsNotMaintainedMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Line If Daily Balance Is Not Maintained [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateAxis" xlink:type="locator" xlink:label="us-gaap_VariableRateAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Rate</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateAxis" xlink:to="us-gaap_VariableRateAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateDomain" xlink:type="locator" xlink:label="us-gaap_VariableRateDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Rate</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateDomain" xlink:to="us-gaap_VariableRateDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PrimeRateMember" xlink:type="locator" xlink:label="us-gaap_PrimeRateMember" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PrimeRateMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prime Rate [Member]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PrimeRateMember" xlink:to="us-gaap_PrimeRateMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PrimeRateMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Prime Rate [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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">Type of Arrangement and Non-arrangement Transactions</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/2018/elts/us-gaap-2018-01-31.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">Arrangements and Non-arrangement Transactions</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="dtil-20190630.xsd#dtil_PacificWesternLoanAgreementMember" xlink:type="locator" xlink:label="dtil_PacificWesternLoanAgreementMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_PacificWesternLoanAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Pacific western loan agreement.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_PacificWesternLoanAgreementMember" xlink:to="dtil_PacificWesternLoanAgreementMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_PacificWesternLoanAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pacific Western Loan Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_PacificWesternLoanAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Pacific Western Loan Agreement [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:type="locator" xlink:label="us-gaap_DebtInstrumentLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Line Items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:type="locator" xlink:label="us-gaap_DebtInstrumentFaceAmount" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate principal amount</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentFaceAmount" xlink:to="us-gaap_DebtInstrumentFaceAmount_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Face Amount</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_PercentageOfSettlementPriceEqualOnIntialPublicOfferingPricePerShare" xlink:type="locator" xlink:label="dtil_PercentageOfSettlementPriceEqualOnIntialPublicOfferingPricePerShare" />
    <link:label xml:lang="en-US" xlink:label="dtil_PercentageOfSettlementPriceEqualOnIntialPublicOfferingPricePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of settlement price equal on intial public offering price per share.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_PercentageOfSettlementPriceEqualOnIntialPublicOfferingPricePerShare" xlink:to="dtil_PercentageOfSettlementPriceEqualOnIntialPublicOfferingPricePerShare_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Number of common stock issued upon settlement convertible promissory notes</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:type="locator" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notes accrue interest rate</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Interest Rate Stated Percentage</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_PercentageOfSettlementPriceEqualOnIntialPublicOfferingPricePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Settlement price equal on IPO price per Share</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_PercentageOfSettlementPriceEqualOnIntialPublicOfferingPricePerShare_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Settlement Price Equal On Intial Public Offering Price Per Share</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtFairValue" xlink:type="locator" xlink:label="us-gaap_LongTermDebtFairValue" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LongTermDebtFairValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of notes</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtFairValue" xlink:to="us-gaap_LongTermDebtFairValue_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LongTermDebtFairValue_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Debt Fair Value</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ChangeInFairValueOfConvertibleNotePayable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in fair value of convertible note payable</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:type="locator" xlink:label="us-gaap_InterestExpenseDebt" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest expense</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpenseDebt" xlink:to="us-gaap_InterestExpenseDebt_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense Debt</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_DebtInstrumentBasisSpreadToBeDeductedFromReferenceRate" xlink:type="locator" xlink:label="dtil_DebtInstrumentBasisSpreadToBeDeductedFromReferenceRate" />
    <link:label xml:lang="en-US" xlink:label="dtil_DebtInstrumentBasisSpreadToBeDeductedFromReferenceRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage points to be deducted from the reference rate to compute the variable rate on the debt instrument..</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_DebtInstrumentBasisSpreadToBeDeductedFromReferenceRate" xlink:to="dtil_DebtInstrumentBasisSpreadToBeDeductedFromReferenceRate_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:type="locator" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum borrowing capacity</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:to="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Maximum Borrowing Capacity</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:type="locator" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturity of line of credit</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityExpirationDate1" xlink:to="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Expiration Date1</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_DebtInstrumentBasisSpreadToBeDeductedFromReferenceRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis point deducted from the prime rate</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_DebtInstrumentBasisSpreadToBeDeductedFromReferenceRate_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Basis Spread To Be Deducted From Reference Rate</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:type="locator" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate during period</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:to="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Interest Rate During Period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CompensatingBalanceAmount" xlink:type="locator" xlink:label="us-gaap_CompensatingBalanceAmount" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CompensatingBalanceAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Required daily balance of cash in demand deposits accounts</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CompensatingBalanceAmount" xlink:to="us-gaap_CompensatingBalanceAmount_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CompensatingBalanceAmount_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Compensating Balance Amount</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:type="locator" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis point added to the prime rate</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:to="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Basis Spread On Variable Rate1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage" xlink:type="locator" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeePercentage" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeePercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving line, fee percentage</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityCommitmentFeePercentage" xlink:to="us-gaap_LineOfCreditFacilityCommitmentFeePercentage_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeePercentage_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Commitment Fee Percentage</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCredit" xlink:type="locator" xlink:label="us-gaap_LineOfCredit" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCredit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Borrowings</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCredit" xlink:to="us-gaap_LineOfCredit_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_LineOfCredit_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLossAbstract" xlink:type="locator" xlink:label="us-gaap_NetIncomeLossAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetIncomeLossAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Numerator:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLossAbstract" xlink:to="us-gaap_NetIncomeLossAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_NetIncomeLossAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Net Income Loss [Abstract]</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/verboseLabel">Net loss attributable to common stockholders</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Denominator:</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number Of Shares Outstanding [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted average shares of common stock outstanding &#8212; basic and diluted</link:label>
    <link:label xml:lang="en-US" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net loss per share attributable to common stockholders &#8212; basic and diluted</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_IncomeTaxDisclosureLineItems" xlink:type="locator" xlink:label="dtil_IncomeTaxDisclosureLineItems" />
    <link:label xml:lang="en-US" xlink:label="dtil_IncomeTaxDisclosureLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Income tax disclosure.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_IncomeTaxDisclosureLineItems" xlink:to="dtil_IncomeTaxDisclosureLineItems_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_IncomeTaxDisclosureTable" xlink:type="locator" xlink:label="dtil_IncomeTaxDisclosureTable" />
    <link:label xml:lang="en-US" xlink:label="dtil_IncomeTaxDisclosureTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Income tax disclosure.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_IncomeTaxDisclosureTable" xlink:to="dtil_IncomeTaxDisclosureTable_lbl" />
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    <link:label xml:lang="en-US" xlink:label="dtil_IncomeTaxDisclosureTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Table]</link:label>
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    <link:loc xlink:href="dtil-20190630.xsd#dtil_DevelopmentMilestonePayments" xlink:type="locator" xlink:label="dtil_DevelopmentMilestonePayments" />
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Development milestone payments.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_DevelopmentMilestonePayments" xlink:to="dtil_DevelopmentMilestonePayments_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_CommercialMilestonePayments" xlink:type="locator" xlink:label="dtil_CommercialMilestonePayments" />
    <link:label xml:lang="en-US" xlink:label="dtil_CommercialMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Commercial milestone payments.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_CommercialMilestonePayments" xlink:to="dtil_CommercialMilestonePayments_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_UpfrontPayment" xlink:type="locator" xlink:label="dtil_UpfrontPayment" />
    <link:label xml:lang="en-US" xlink:label="dtil_UpfrontPayment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront payment.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_UpfrontPayment" xlink:to="dtil_UpfrontPayment_lbl" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable" xlink:type="locator" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable" xlink:to="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_DevelopmentAndCommercialLicenseAgreementMember" xlink:type="locator" xlink:label="dtil_DevelopmentAndCommercialLicenseAgreementMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentAndCommercialLicenseAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Development and commercial license agreement.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_DevelopmentAndCommercialLicenseAgreementMember" xlink:to="dtil_DevelopmentAndCommercialLicenseAgreementMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentAndCommercialLicenseAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Development and Commercial License Agreement</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentAndCommercialLicenseAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Development And Commercial License Agreement [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.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/2018/elts/us-gaap-2018-01-31.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="dtil-20190630.xsd#dtil_ServierMember" xlink:type="locator" xlink:label="dtil_ServierMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_ServierMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Servier</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_ServierMember" xlink:to="dtil_ServierMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_ServierMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Servier</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ServierMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Servier [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:type="locator" xlink:label="us-gaap_BalanceSheetLocationAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_BalanceSheetLocationAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Balance Sheet Location</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_BalanceSheetLocationAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Balance Sheet Location [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:type="locator" xlink:label="us-gaap_BalanceSheetLocationDomain" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_BalanceSheetLocationDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Balance Sheet Location</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BalanceSheetLocationDomain" xlink:to="us-gaap_BalanceSheetLocationDomain_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_BalanceSheetLocationDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Balance Sheet Location [Domain]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_CurrentLiabilitiesMember" xlink:type="locator" xlink:label="dtil_CurrentLiabilitiesMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_CurrentLiabilitiesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Current liabilities.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_CurrentLiabilitiesMember" xlink:to="dtil_CurrentLiabilitiesMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_CurrentLiabilitiesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Liabilities</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_CurrentLiabilitiesMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Current Liabilities [Member]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_CollaborationAndLicenseAgreementMember" xlink:type="locator" xlink:label="dtil_CollaborationAndLicenseAgreementMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_CollaborationAndLicenseAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Collaboration and license agreement.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_CollaborationAndLicenseAgreementMember" xlink:to="dtil_CollaborationAndLicenseAgreementMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_CollaborationAndLicenseAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaboration and License Agreement</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_CollaborationAndLicenseAgreementMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Collaboration And License Agreement [Member]</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_GileadSciencesIncMember" xlink:type="locator" xlink:label="dtil_GileadSciencesIncMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_GileadSciencesIncMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Gilead Sciences, Inc.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_GileadSciencesIncMember" xlink:to="dtil_GileadSciencesIncMember_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_GileadSciencesIncMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gilead</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_GileadSciencesIncMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Gilead Sciences Inc [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems" xlink:type="locator" xlink:label="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaboration and License Agreements [Line items]</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems" xlink:to="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_UpfrontPayment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront payment</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_UpfrontPayment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Payment</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AggregatePaymentOnCollaborationAgreementToBeReceived_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total payments to be received</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AggregatePaymentOnCollaborationAgreementToBeReceived_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Payment On Collaboration Agreement To Be Received</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AggregateMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate milestone payments</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_AggregateMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Milestone Payments</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Development milestone payments</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Development Milestone Payments</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_CommercialMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commercial milestone payments</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_CommercialMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Commercial Milestone Payments</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" xlink:type="locator" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" xlink:to="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation" xlink:type="locator" xlink:label="us-gaap_RevenueRemainingPerformanceObligation" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueRemainingPerformanceObligation_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue from upfront payment</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRemainingPerformanceObligation" xlink:to="us-gaap_RevenueRemainingPerformanceObligation_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueRemainingPerformanceObligation_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Remaining Performance Obligation</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" xlink:type="locator" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated period performance obligation</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" xlink:to="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:type="locator" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recognized revenue under agreement</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:to="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Contract With Customer Liability Revenue Recognized</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromCollaborators" xlink:type="locator" xlink:label="us-gaap_ProceedsFromCollaborators" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProceedsFromCollaborators_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Development or sales-based milestone payments</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromCollaborators" xlink:to="us-gaap_ProceedsFromCollaborators_lbl" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_ProceedsFromCollaborators_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Collaborators</link:label>
    <link:loc xlink:href="dtil-20190630.xsd#dtil_ReceivableFromResearchFunding" xlink:type="locator" xlink:label="dtil_ReceivableFromResearchFunding" />
    <link:label xml:lang="en-US" xlink:label="dtil_ReceivableFromResearchFunding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Receivable from research funding.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_ReceivableFromResearchFunding" xlink:to="dtil_ReceivableFromResearchFunding_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_DevelopmentAndCommercialMilestonePayments" xlink:type="locator" xlink:label="dtil_DevelopmentAndCommercialMilestonePayments" />
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentAndCommercialMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Development and commercial milestone payments.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_DevelopmentAndCommercialMilestonePayments" xlink:to="dtil_DevelopmentAndCommercialMilestonePayments_lbl" />
    <link:loc xlink:href="dtil-20190630.xsd#dtil_ResearchFundingPaymentTerm" xlink:type="locator" xlink:label="dtil_ResearchFundingPaymentTerm" />
    <link:label xml:lang="en-US" xlink:label="dtil_ResearchFundingPaymentTerm_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Research funding payment term.</link:label>
    <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dtil_ResearchFundingPaymentTerm" xlink:to="dtil_ResearchFundingPaymentTerm_lbl" />
    <link:label xml:lang="en-US" xlink:label="dtil_ReceivableFromResearchFunding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Receivable from research funding</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ReceivableFromResearchFunding_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Receivable From Research Funding</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ResearchFundingPaymentTerm_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research funding payment term</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_ResearchFundingPaymentTerm_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Research Funding Payment Term</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentAndCommercialMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Development and commercial milestone payments</link:label>
    <link:label xml:lang="en-US" xlink:label="dtil_DevelopmentAndCommercialMilestonePayments_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label">Development And Commercial Milestone Payments</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment" xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment" />
    <link:label xml:lang="en-US" xlink:label="us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Semi-annual research funding payments</link:label>
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    <link:label xml:lang="en-US" xlink:label="us-gaap_SegmentDomain_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segments</link:label>
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    <link:label xml:lang="en-US" xlink:label="dtil_TherapeuticsSegmentMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Therapeutics segment.</link:label>
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    <link:loc xlink:href="dtil-20190630.xsd#dtil_FoodSegmentMember" xlink:type="locator" xlink:label="dtil_FoodSegmentMember" />
    <link:label xml:lang="en-US" xlink:label="dtil_FoodSegmentMember_lbl" xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation">Food Segment [Member].</link:label>
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