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Convertible Preferred Stock and Stockholders' Equity (Deficit) - Schedule of Reserved Common Stock on an if-Converted Basis for Issuance (Details) - shares | Dec. 31, 2019 | Dec. 31, 2018
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Class Of Stock [Line Items] |  |
Total shares of authorized common stock reserved for future issuance | 8,310,754 | 5,259,271
Common Stock Options Issued and Outstanding |  |
Class Of Stock [Line Items] |  |
Total shares of authorized common stock reserved for future issuance | 4,738,004 | 1,458,080
Remaining Shares Available for Issuance under 2015 & 2018 Stock Plan |  |
Class Of Stock [Line Items] |  |
Total shares of authorized common stock reserved for future issuance | 2,315,099 | 3,801,191
Unvested Restricted Stock Issued as Part of Collaboration Agreement |  |
Class Of Stock [Line Items] |  |
Total shares of authorized common stock reserved for future issuance | 1,257,651 |

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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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