Surface Oncology (SURF) 10-Q 4 Nov 21 2021 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Sep. 30, 2021	Nov. 01, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-38459
Entity Registrant Name	SURFACE ONCOLOGY, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5543980
Entity Address, Address Line One	50 Hampshire Street
Entity Address, Address Line Two	8th Floor
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	714-4096
Title of 12(b) Security	Common stock, $0.0001
Trading Symbol	SURF
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		46,135,245
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001718108
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 60,848	$ 175,141
Marketable securities	88,850	0
Prepaid expenses and other current assets	5,059	5,368
Total current assets	154,757	180,509
Property and equipment, net	5,522	6,664
Operating lease right-of-use asset	26,394	27,911
Restricted cash	1,595	1,595
Other assets	344	459
Total assets	188,612	217,138
Current liabilities:
Accounts payable	440	1,674
Accrued expenses and other current liabilities	9,923	10,448
Operating lease liability	5,440	5,529
Total current liabilities	15,803	17,651
Operating lease liability, non-current	27,426	28,981
Convertible note payable, non-current	14,186	14,759
Total liabilities	57,415	61,391
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized    at September 30, 2021 and December 31, 2020; no shares    issued and outstanding at September 30, 2021 and December 31, 2020	0	0
Common stock, $0.0001 par value; 150,000,000 shares    authorized at September 30, 2021 and December 31, 2020, respectively;    45,503,061 and 40,707,047 shares issued and outstanding at September 30, 2021    and December 31, 2020, respectively	5	4
Additional paid-in capital	247,888	218,001
Accumulated other comprehensive loss	(3)	0
Accumulated deficit	(116,693)	(62,258)
Total stockholders’ equity	131,197	155,747
Total liabilities and stockholders’ equity	$ 188,612	$ 217,138

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized (in shares)	5,000,000	5,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, issued (in shares)	45,503,061	40,707,047
Common stock, outstanding (in shares)	45,503,061	40,707,047

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Collaboration revenue - related party	$ 0	$ 0	$ 0	$ 38,592
License related revenue	392	0	2,532	0
Total revenue	392	0	2,532	38,592
Operating expenses:
Research and development	14,037	9,454	37,250	30,290
General and administrative	5,847	4,904	17,923	14,686
Total operating expenses	19,884	14,358	55,173	44,976
Loss from operations	(19,492)	(14,358)	(52,641)	(6,384)
Interest expense	(421)	(1,469)	(1,861)	(2,237)
Other income (expense), net	20	53	67	610
Net loss	$ (19,893)	$ (15,774)	$ (54,435)	$ (8,011)
Net loss per share attributable to common stockholders— basic (in dollars per share)	$ (0.44)	$ (0.39)	$ (1.25)	$ (0.24)
Weighted average common shares outstanding— basic (in shares)	45,236,775	40,004,555	43,510,078	33,822,682
Net loss per share attributable to common stockholders— diluted (in dollars per share)	$ (0.44)	$ (0.39)	$ (1.25)	$ (0.24)
Weighted average common shares outstanding— diluted (in shares)	45,236,775	40,004,555	43,510,078	33,822,682
Comprehensive loss:
Net loss	$ (19,893)	$ (15,774)	$ (54,435)	$ (8,011)
Other comprehensive loss:
Unrealized gain (loss) on marketable securities, net of tax of $0	6	(50)	(3)	(99)
Comprehensive loss	$ (19,887)	$ (15,824)	$ (54,438)	$ (8,110)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Marketable securities tax	$ 0	$ 0	$ 0	$ 0

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		27,893,337
Beginning balance at Dec. 31, 2019	$ 56,666	$ 3	$ 178,155	$ 103	$ (121,595)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		27,832
Issuance of common stock upon exercise    of stock options	10		10
Issuance of common stock under stock purchase plan (in shares)		49,025
Issuance of common stock under stock purchase plan	83		83
Issuance of common stock upon public offering, net of issuance costs (in shares)		91,003
Issuance of common stock upon public offering, net of issuance costs	320		320
Stock-based compensation expense	1,850		1,850
Unrealized gain (loss) on marketable securities	67			67
Net loss	22,570				22,570
Ending balance (in shares) at Mar. 31, 2020		28,061,197
Ending balance at Mar. 31, 2020	81,566	$ 3	180,418	170	(99,025)
Beginning balance (in shares) at Dec. 31, 2019		27,893,337
Beginning balance at Dec. 31, 2019	56,666	$ 3	178,155	103	(121,595)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) on marketable securities	(99)
Net loss	(8,011)
Ending balance (in shares) at Sep. 30, 2020		40,616,644
Ending balance at Sep. 30, 2020	86,064	$ 4	215,662	4	(129,606)
Beginning balance (in shares) at Dec. 31, 2019		27,893,337
Beginning balance at Dec. 31, 2019	$ 56,666	$ 3	178,155	103	(121,595)
Ending balance (in shares) at Dec. 31, 2020	40,707,047	40,707,047
Ending balance at Dec. 31, 2020	$ 155,747	$ 4	218,001	0	(62,258)
Beginning balance (in shares) at Mar. 31, 2020		28,061,197
Beginning balance at Mar. 31, 2020	81,566	$ 3	180,418	170	(99,025)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		68,426
Issuance of common stock upon exercise    of stock options	262		262
Issuance of common stock upon public offering, net of issuance costs (in shares)		11,127,590
Issuance of common stock upon public offering, net of issuance costs	28,766	$ 1	28,765
Stock-based compensation expense	2,000		2,000
Unrealized gain (loss) on marketable securities	(116)			(116)
Net loss	(14,807)				(14,807)
Ending balance (in shares) at Jun. 30, 2020		39,257,213
Ending balance at Jun. 30, 2020	97,671	$ 4	211,445	54	(113,832)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		37,234
Issuance of common stock upon exercise    of stock options	143		143
Issuance of common stock under stock purchase plan (in shares)		40,147
Issuance of common stock under stock purchase plan	111		111
Issuance of common stock upon conversion of convertible note payable (in shares)		1,282,050
Issuance of common stock upon conversion of convertible note payable	2,000		2,000
Stock-based compensation expense	1,963		1,963
Unrealized gain (loss) on marketable securities	(50)			(50)
Net loss	(15,774)				(15,774)
Ending balance (in shares) at Sep. 30, 2020		40,616,644
Ending balance at Sep. 30, 2020	$ 86,064	$ 4	215,662	4	(129,606)
Beginning balance (in shares) at Dec. 31, 2020	40,707,047	40,707,047
Beginning balance at Dec. 31, 2020	$ 155,747	$ 4	218,001	0	(62,258)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		55,761
Issuance of common stock upon exercise    of stock options	148		148
Issuance of common stock under stock purchase plan (in shares)		19,377
Issuance of common stock under stock purchase plan	118		118
Issuance of common stock upon public offering, net of issuance costs (in shares)		1,677,118
Issuance of common stock upon public offering, net of issuance costs	14,716	$ 1	14,715
Issuance of common stock upon conversion of convertible note payable (in shares)		961,538
Issuance of common stock upon conversion of convertible note payable	1,500		1,500
Stock-based compensation expense	2,380		2,380
Unrealized gain (loss) on marketable securities	(1)			(1)
Net loss	(15,561)				(15,561)
Ending balance (in shares) at Mar. 31, 2021		43,420,841
Ending balance at Mar. 31, 2021	$ 159,047	$ 5	236,862	(1)	(77,819)
Beginning balance (in shares) at Dec. 31, 2020	40,707,047	40,707,047
Beginning balance at Dec. 31, 2020	$ 155,747	$ 4	218,001	0	(62,258)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) on marketable securities	(3)
Net loss	$ (54,435)
Ending balance (in shares) at Sep. 30, 2021	45,503,061	45,503,061
Ending balance at Sep. 30, 2021	$ 131,197	$ 5	247,888	(3)	(116,693)
Beginning balance (in shares) at Mar. 31, 2021		43,420,841
Beginning balance at Mar. 31, 2021	159,047	$ 5	236,862	(1)	(77,819)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		358,126
Issuance of common stock upon exercise    of stock options	1,486		1,486
Issuance of common stock upon public offering, net of issuance costs (in shares)		556,642
Issuance of common stock upon public offering, net of issuance costs	4,266		4,266
Stock-based compensation expense	2,279		2,279
Unrealized gain (loss) on marketable securities	(8)			(8)
Net loss	(18,981)				(18,981)
Ending balance (in shares) at Jun. 30, 2021		44,335,609
Ending balance at Jun. 30, 2021	148,089	$ 5	244,893	(9)	(96,800)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		72,745
Issuance of common stock upon exercise    of stock options	305		305
Issuance of common stock upon vesting of RSUs (in shares)		997,400
Issuance of common stock under stock purchase plan (in shares)		27,522
Issuance of common stock under stock purchase plan	149		149
Issuance of common stock upon conversion of convertible note payable (in shares)		69,785
Issuance of common stock upon conversion of convertible note payable	497		497
Stock-based compensation expense	2,044		2,044
Unrealized gain (loss) on marketable securities	6			6
Net loss	$ (19,893)				(19,893)
Ending balance (in shares) at Sep. 30, 2021	45,503,061	45,503,061
Ending balance at Sep. 30, 2021	$ 131,197	$ 5	$ 247,888	$ (3)	$ (116,693)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (54,435)	$ (8,011)
Adjustments to reconcile net loss to net cash provided by (used in)    operating activities:
Depreciation and amortization expense	1,194	1,260
Stock-based compensation expense	6,703	5,813
Non-cash interest expense related to note payable	927	1,484
Net amortization of premiums and discounts on marketable securities	586	(50)
Loss on disposal of property and equipment	0	1
Non-cash operating lease cost	1,517	1,537
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	309	(2,358)
Other assets	115	(181)
Accounts payable	(1,234)	(2,875)
Accrued expenses and other current liabilities	(525)	(1,339)
Operating lease liability	(1,644)	(101)
Other liabilities	0	1,100
Deferred revenue - related party	0	(38,592)
Net cash used in operating activities	(46,487)	(42,312)
Cash flows from investing activities:
Purchases of property and equipment	(52)	(22)
Purchases of marketable securities	(91,439)	(650)
Proceeds from sales or maturities of marketable securities	2,000	56,000
Net cash provided by (used in) investing activities	(89,491)	55,328
Cash flows from financing activities:
Proceeds from issuance of convertible note payable	0	10,000
Proceeds from issuance of common stock upon public offering, net	19,479	29,086
Proceeds from employee stock purchases	267	194
Proceeds from exercise of stock options	1,939	415
Net cash provided by financing activities	21,685	39,695
Net increase (decrease) in cash and cash equivalents and restricted cash	(114,293)	52,711
Cash and cash equivalents and restricted cash at beginning of period	176,736	48,350
Cash and cash equivalents and restricted cash at end of period	62,443	101,061
Supplemental disclosure of cash flow information:
Cash paid for interest	945	753
Supplemental disclosure of non-cash investing and financing activities:
Additional right-of-use asset and related lease liability	0	15,003
Purchases of property and equipment included in accounts payable and accrued expenses	0	869
Conversion of note payable into shares of common stock	$ 1,500	$ 2,000

Nature of the Business

Nature of the Business	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business	Nature of the Business Surface Oncology, Inc. (the “Company” or “Surface”) is a clinical-stage immuno-oncology company focused on using its specialized knowledge of the biological pathways critical to the immunosuppressive tumor microenvironment (“TME”) for the development of next-generation cancer therapies. Surface was incorporated in April 2014 under the laws of the State of Delaware. The Company is subject to risks common to early-stage companies in the biotechnology industry including, but not limited to, development by competitors of new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the ability to obtain additional financing to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. On May 22, 2020, the Company entered into a Capital on Demand ™ Sales Agreement (the “2020 Sales Agreement”) with JonesTrading Institutional Services LLC (“JonesTrading") to issue and sell shares of the Company’s common stock of up to $50,000 in gross proceeds, from time to time during the term of the 2020 Sales Agreement, through an “at-the-market” equity offering program under which JonesTrading will act as the Company’s agent and/or principal (the “2020 ATM Facility”). The 2020 ATM Facility provides that JonesTrading will be entitled to compensation for its services in an amount of up to 3.0% of the gross proceeds of any shares sold under the 2020 ATM Facility. The Company has no obligation to sell any shares under the 2020 ATM Facility and may, at any time, suspend solicitation and offers under the 2020 Sales Agreement. In the three and nine months ended September 30, 2021, the Company sold 69,785 and 2,303,545 shares of common stock, respectively, at-the-market under the 2020 Sales Agreement, resulting in net proceeds of approximately $497 and $19,479, respectively. The Company did not sell any shares of common stock at-the-market under the 2020 Sales Agreement in 2020. On August 5, 2021, the Company entered into Amendment No. 1 to Capital on DemandTM Sales Agreement (the “Amended Sales Agreement”) with JonesTrading, which amends the 2020 Sales Agreement to allow the issuance and sale of up to $80,000 in gross proceeds, from time to time during the term of the Amended Sales Agreement, through an “at-the-market” equity offering program under which JonesTrading will act as the Company’s sales agent ("the 2021 ATM Facility"). The 2021 ATM Facility provides that JonesTrading will continue to be entitled to compensation for its services in an amount of up to 3.0% of the gross proceeds of any shares sold under the 2021 ATM Facility. The Company has no obligation to sell any shares under the Amended Sales Agreement and may, at any time, suspend solicitation and offers under the 2021 ATM Facility. The Company has not sold any shares of common stock at-the-market under the 2021 ATM Facility as of September 30, 2021. The Company’s financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has primarily funded its operations with proceeds from private and public sales of its securities, proceeds from a collaboration agreement with Novartis Institutes for Biomedical Research, Inc. (“Novartis”), proceeds from a license agreement with GlaxoSmithKline Intellectual Property (No. 4) Limited (“GSK”) and issuance of a term loan with K2 Health Ventures LLC (“K2HV”). The Company has a history of incurring losses and negative cash flows from operations. As of September 30, 2021, the Company had an accumulated deficit of $116,693. The Company expects that its operating losses and negative cash flows will continue for the foreseeable future. As of November 4, 2021, the issuance date of this Quarterly Report on Form 10-Q, the Company expects that its cash, cash equivalents and marketable securities will be sufficient to fund its operating expenses, debt service obligations and capital expenditure requirements for at least the next 12 months. The future viability of the Company beyond that date is dependent on its ability to raise additional capital to finance its operations. The Company will seek additional funding through public financings, debt financings, collaboration agreements, strategic alliances and licensing arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be required to delay, reduce, or eliminate research and development programs, product portfolio expansion, or future commercialization efforts, which could adversely affect its business prospects. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. The ongoing global outbreak of the novel coronavirus disease (“COVID-19”) has resulted in significant governmental measures being implemented to control the spread of the virus and while the Company cannot predict their scope or the severity of the outbreak, these developments and measures could materially and adversely affect the Company's business, the Company's results of operations and financial condition. The Company is closely monitoring the impact of the COVID-19 pandemic on all aspects of its business and has taken steps to minimize its impact on the Company's business. Although COVID-19 has not had a material adverse impact on the Company's operations and its clinical and preclinical programs, the extent to which COVID-19 ultimately impacts the Company's business, results of operations or financial condition will depend on future developments which are highly uncertain and cannot be predicted with confidence, such as the duration of the outbreak, new information that may emerge concerning the severity of COVID-19 or the effectiveness of actions taken to contain the pandemic or mitigate its impact, among others. Certain of the Company's third-party service providers have experienced shutdowns or other business disruptions. As a result, the Company's ability to conduct its business in the manner and on the timelines presently planned could be materially or negatively affected, which could have a material adverse impact on the Company's business, results of operations and financial condition.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and its wholly owned subsidiary, Surface Securities Corporation, a Massachusetts corporation, after elimination of all intercompany accounts and transactions. The accounting policies followed in the preparation of the interim condensed consolidated financial statements are consistent in all material respects with those presented in Note 2 to the financial statements included in the Company’s Annual Report on Form 10-K, filed with the Securities and Exchange Commission (the “SEC”) on March 9, 2021. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, revenue recognition and the accrual of research and development expenses. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from the Company’s estimates. Unaudited Interim Financial Information The accompanying condensed consolidated financial statements are unaudited. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of September 30, 2021 and the results of its operations and its cash flows for the nine months ended September 30, 2021 and 2020. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2021 and 2020 are also unaudited. The condensed balance sheet at December 31, 2020, was derived from audited annual financial statements but does not contain all of the footnote disclosures from the annual financial statements. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, any other interim periods, or any future year period. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13") , which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss model. It also eliminates the concept of other-than-temporary impairment and requires credit losses related to available-for-sale debt securities to be recorded through an allowance for credit losses rather than as a reduction in the amortized cost basis of the securities. These changes may result in earlier recognition of credit losses. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments—Credit Losses , which narrowed the scope and changed the effective date for non-public entities for ASU 2016-13. The FASB subsequently issued supplemental guidance within ASU No. 2019-05, Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief ("ASU 2019-05") . ASU 2019-05 provides an option to irrevocably elect the fair value option for certain financial assets previously measured at amortized cost basis. For public entities that are Securities and Exchange Commission filers, excluding entities eligible to be smaller reporting companies, ASU 2016-13 is effective for annual periods beginning after December 15, 2019, including interim periods within those fiscal years. For all other entities, ASU 2016-13 is effective for annual periods beginning after December 15, 2022, including interim periods within those fiscal years. Early adoption is permitted. This standard will be effective for the Company on January 1, 2023. The Company is currently evaluating the potential impact that this standard may have on its condensed consolidated financial statements and related disclosures. Other accounting standards that have been issued by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s financial statements upon adoption.

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities As of September 30, 2021, the fair value of available-for-sale marketable debt securities by type of security was as follows: September 30, 2021 Amortized Gross Gross Fair Marketable debt securities: U.S. Treasury notes $ 73,017 $ 9 (10) $ 73,016 U.S. government agency bonds 15,836 1 (3) 15,834 $ 88,853 $ 10 $ (13) $ 88,850 The amortized cost and fair value of the Company’s available-for-sale debt securities by contractual maturity are summarized as follows: September 30, 2021 Amortized Fair Maturing in one year or less $ 56,568 $ 56,576 Maturing after one year 32,285 32,274 $ 88,853 $ 88,850 As of December 31, 2020, there were no available-for-sale marketable debt securities. The Company determined that there was no material change in the credit risk of these investments. As a result, the Company determined it did not hold any investments with an other-than-temporary decline in fair value as of September 30, 2021 and December 31, 2020.

Fair Value of Financial Assets

Fair Value of Financial Assets	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets	Fair Value of Financial Assets The following tables present information about the Company’s financial assets that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values: Fair Value Measurements as of September 30, 2021 using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 44,686 $ — $ — $ 44,686 Cash 23 — — 23 Marketable securities: U.S. Treasury notes — 73,016 — 73,016 U.S. government agency bonds — 15,834 — 15,834 $ 44,709 $ 88,850 $ — $ 133,559 Fair Value Measurements as of December 31, 2020 using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 139,266 $ — $ — $ 139,266 $ 139,266 $ — $ — $ 139,266 As of September 30, 2021 and December 31, 2020, the Company’s cash equivalents were invested in money market funds, U.S. Treasury notes and U.S. government agency bonds and were valued based on Level 1 and Level 2 inputs. During the nine months ended September 30, 2021 and 2020, there were no transfers between Level 1, Level 2 and Level 3.

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and License Agreements	Collaboration and License Agreements Novartis Agreement In January 2016, the Company entered into a collaboration agreement with Novartis (the “Novartis Agreement”), which was subsequently amended in May 2016, July 2017, September 2017, and October 2018. Pursuant to the Novartis Agreement, the Company granted Novartis a worldwide exclusive license to research, develop, manufacture and commercialize antibodies that target cluster of differentiation 73 (“CD73”). In addition, the Company initially granted Novartis the right to purchase exclusive option rights (each an “Option”) for up to four specified targets (each an “Option Target”) including certain development, manufacturing, and commercialization rights. Novartis initially had the right to exercise up to three purchased Options. Under the Novartis Agreement, therefore, Novartis had the ability to exclusively license the development and manufacturing rights for up to four targets (inclusive of CD73). In January 2020, Novartis did not purchase and exercise its single remaining Option under the Novartis Agreement and, as a result, the option purchase period expired. Therefore, there are no Options remaining eligible for purchase, and potential exercise, and the Company’s performance obligations under the Novartis Agreement have ended. Under the Novartis Agreement, the Company is currently entitled to potential development milestones of $325,000 and sales milestones of $200,000, as well as tiered royalties on annual net sales by Novartis ranging from high single-digit to mid-teens percentages upon the successful commercialization of NZV930 (formerly SRF373). Termination Unless terminated earlier, the Novartis Agreement will continue in effect until neither the Company nor Novartis is researching, developing, manufacturing or commercializing NZV930. Novartis may terminate the Novartis Agreement for any reason upon prior notice to the Company within a specified time period. Either party may terminate the Novartis Agreement in full if an undisputed material breach is not cured within a certain period of time or upon notice of insolvency of the other party. To the extent Novartis terminates for convenience, or the Company terminates for Novartis’ material breach, Novartis will grant the Company, on mutually agreeable financial terms, an exclusive, worldwide, irrevocable, perpetual and royalty-bearing license with respect to intellectual property controlled by Novartis that is reasonably necessary to research, develop, manufacture or commercialize NZV930. Revenue Recognition – Collaboration Revenue – Related Party In determining the appropriate amount of revenue to be recognized under ASC 606, the Company performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Under ASC 606, the Company recognized revenue using the cost-to-cost method, which it believes best depicts the transfer of control to the customer. Under the cost-to-cost method, the extent of progress towards completion is measured based on the ratio of actual costs incurred to the total estimated costs expected upon satisfying the identified performance obligation. Under this method, revenue will be recorded as a percentage of the estimated transaction price based on the extent of progress towards completion. Under ASC 606, the estimated transaction price will include variable consideration. The Company does not include variable consideration to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will occur when any uncertainty associated with the variable consideration is resolved. The estimate of the Company’s measure of progress and estimate of variable consideration to be included in the transaction price will be updated at each reporting date as a change in estimate. The amount related to the unsatisfied portion will be recognized as that portion is satisfied over time. Under ASC 606 the Company accounted for (i) the license it conveyed with respect to CD73; and (ii) its obligations to perform research on CD73 and other specified targets as a single performance obligation under the Novartis Agreement. Novartis’ right to purchase exclusive options to obtain certain development, manufacturing and commercialization rights would have been accounted for separately as they did not represent material rights, based on the criteria of ASC 606. Upon the exercise of any purchased option by Novartis, the contract promises associated with an Option Target would have used a separate cost-to-cost model for purposes of revenue recognition under ASC 606. In January 2020, Novartis did not purchase and exercise its single remaining Option under the Novartis Agreement and, as a result, the option purchase period expired. Future costs associated with this target were removed from the estimated total costs in the cost-to-cost model. This resulted in the Company recognizing the remaining deferred revenue of $38,592 to collaboration revenue - related party in January 2020. For the three and nine months ended September 30, 2021 and 2020, the Company recognized the following totals of collaboration revenue – related party: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Collaboration revenue - related party $ — $ — $ — $ 38,592 GSK Agreement In December 2020, the Company entered into a license agreement with GSK (as amended by the GSK Amendment (as defined below) the "GSK Agreement"). Pursuant to the GSK Agreement, the Company granted GSK a worldwide, exclusive, sublicensable license to develop, manufacture and commercialize antibodies that target the antibody SRF813, targeting CD112R, also known as PVRIG (the “Licensed Antibodies”). GSK will be responsible for the development, manufacturing and commercialization of the Licensed Antibodies and a joint development committee has been formed to facilitate information sharing between the Company and GSK. Under the terms of the GSK Agreement, GSK is obligated to use commercially reasonable efforts to develop and commercialize the Licensed Antibodies. In August 2021, the Company entered into the first amendment to the GSK License Agreement (the "GSK Amendment"). Pursuant to the GSK Amendment, the Company will provide additional transition and supply services related to the development and manufacturing of the Licensed Antibodies. Development, Manufacturing and Commercialization of Licensed Antibodies GSK has the sole right to develop, manufacture and commercialize the Licensed Antibodies and corresponding licensed products worldwide. GSK is obligated to use commercially reasonable efforts to develop the Licensed Antibodies and corresponding licensed products. GSK is responsible for all costs and expenses of such development, manufacturing and commercialization and is obligated to provide the Company with updates on its development, manufacturing and commercialization activities through the joint development committee. Exclusivity During the term of the GSK Agreement, neither the Company, nor any affiliates, will research, develop, manufacture, or commercialize any alternative product. Financial Terms Under the terms of the GSK Agreement, GSK made a one-time upfront payment of $85,000 and is required to make additional payments to the Company for supply services and transition services, estimated to be $4,952 and $990, respectively. The Company is eligible to receive up to $90,000 in clinical and $155,000 in regulatory milestones. In addition, the Company may receive up to $485,000 in sales milestone payments. The Company is also eligible to receive royalties on global net sales of any approved products based on the licensed antibodies, ranging in percentages from high single digits to mid-teens. Due to the uncertainty of pharmaceutical development and the historical failure rates generally associated with drug development, the Company may not receive any milestone payments or any royalty payments under the GSK Agreement. Termination Unless terminated earlier, the GSK Agreement expires on a licensed product-by-licensed product and country-by-country basis on the later of ten years from the date of first commercial sale or when there is no longer a valid patent claim or regulatory exclusivity covering such licensed product in such country. Either party may terminate the GSK Agreement for an uncured material breach by the other party or upon the bankruptcy or insolvency of the other party. GSK may terminate the GSK Agreement for its convenience. The Company may terminate the GSK Agreement if GSK institutes certain actions related to the licensed patents or if GSK ceases development activities, other than for certain specified technical or safety reasons. In the event of termination, the Company would regain worldwide rights to the terminated program. Revenue Recognition – License Related Revenue In determining the appropriate amount of revenue to be recognized under ASC 606, the Company performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company assessed the GSK Agreement in accordance with ASC 606 and concluded that GSK is a customer. The Company identified the following promises under the contract: (i) a worldwide, exclusive, sublicensable license to develop, manufacture and commercialize the Licensed Antibodies; (ii) supplying Licensed Antibodies until an Investigational New Drug application is accepted by a regulatory authority (iii) transition services until an Investigational New Drug application is accepted by a regulatory authority; and (iv) participation on the joint development and joint patent committees. The Company assessed the above promises and determined that the worldwide, exclusive, sublicensable license to develop, manufacture and commercialize the Licensed Antibodies is considered functional intellectual property and distinct from other promises under the contract. This functional license is distinct in the context of the GSK Agreement as GSK can benefit from the license on its own or together with other readily available resources. In addition, the supply and transition services are not complex or specialized, could be performed by another qualified third party, are not expected to significantly modify or customize the license to SRF813, and are expected to be performed only for a short period of time. The Company determined that the impact of participation on the joint development and joint patent committees was insignificant and had an immaterial impact on the accounting model. Based on these assessments, the Company identified three distinct performance obligations at the outset of the GSK Agreement. The Company determined the transaction price of the GSK Agreement, under ASC 606, to be $90,942, consisting of the upfront payment of $85,000 plus $4,952 for supply of the Licensed Antibodies and $990 for the transition services. The Company evaluated how much variable consideration related to clinical and regulatory milestones to include in the transaction price using the most likely amount approach and concluded that no amount should be included in the transaction price due to the high degree of uncertainty and risk associated with these potential payments. The Company also determined that royalties and sales milestones relate solely to the licenses of intellectual property and are therefore excluded from the transaction price under the sales- or usage-based royalty exception of ASC 606. Revenue related to these royalties and sales milestones will only be recognized when the associated sales occur, and relevant thresholds are met. As noted above, the Company identified three performance obligations in the GSK Agreement: (i) the delivery of the worldwide, exclusive, sublicensable license to develop, manufacture and commercialize the Licensed Antibodies; (ii) supply of Licensed Antibodies until an Investigational New Drug application is accepted by a regulatory authority; and (iii) transition services until an Investigational New Drug application is accepted by a regulatory authority. The selling price of each performance obligation in the GSK Agreement was determined based on the Company’s standalone selling price, with the objective of determining the price at which it would sell such an item if it were to be sold regularly on a standalone basis. The Company recognizes revenue for the license performance obligation at a point in time, that is upon transfer of the license to GSK. As control of the license was transferred on the effective date of December 16, 2020 and GSK could begin to use and benefit from the license, the Company recognized $85,000 of license related revenue during the year ended December 31, 2020 under the GSK Agreement. The Company will recognize $4,952 and $990 allocated to the supply services and transition services over time. The Company transfers control of these services over time and GSK receives and consumes the benefit over time as the Company performs the services. During the three and nine months ended September 30, 2021, the Company recognized $48 and $709 of license related revenue, respectively, related to the transition services and recognized $344 and $1,823 of license related revenue, respectively, related to the supply services, which represents the costs incurred for the manufacturing and transition services that were performed. The aggregate amount of the transaction price allocated to the performance obligations that is partially unsatisfied was $912. The Company expects to recognize the remaining revenue associated with the GSK Agreement in the year ending December 31, 2021. As of September 30, 2021, the Company did not have a contract liability associated with the GSK Agreement. The Company will re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved, or other changes in circumstances occur, adjust its estimate of the transaction price if necessary. For the three and nine months ended September 30, 2021 and 2020 , the Company recognized the following totals of license related revenue: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 License related revenue $ 392 $ — $ 2,532 $ —

Stockholders_ Equity

Stockholders’ Equity	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Stockholders’ Equity	Stockholders’ Equity Common Stock As of September 30, 2021 and December 31, 2020, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue 150,000,000 shares, of $0.0001 par value common stock. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any, subject to the preferential dividend rights of any outstanding preferred stock. No dividends have been declared or paid by the Company through September 30, 2021. As of September 30, 2021 and December 31, 2020, the Company had reserved 33,878,328 and 22,728,991 shares, respectively, of common stock for the exercise of outstanding stock options, shares to be issued under the 2021 ATM Facility, shares to be issued upon the conversion of the Loan Agreement (as defined below), and the number of shares remaining available for future grant under the Company’s 2018 Stock Option and Incentive Plan and 2018 Employee Stock Purchase Plan. On May 1, 2019, the Company entered into the 2019 Sales Agreement with JonesTrading to issue and sell up to $30,000 in shares of the Company’s common stock from time to time. In the nine months ended September 30, 2020, the Company sold 11,218,593 shares of common stock at-the-market under the 2019 Sales Agreement, resulting in net proceeds of approximately $29,086. The Company did not sell any shares of common stock at-the-market under the 2019 Sales Agreement in the three months ended September 30, 2020. Through September 30, 2020, the Company sold 11,229,174 shares of common stock at-the-market under the 2019 Sales Agreement for net proceeds of $29,110. As of June 30, 2020 the Company fully utilized and closed the 2019 ATM Facility. In May 2020, the Company entered into the 2020 Sales Agreement with JonesTrading to issue and sell up to $50,000 in shares of the Company's common stock, from time to time. In the three and nine months ended September 30, 2021, the Company sold 69,785 and 2,303,545 shares of common stock at-the-market under the 2020 Sales Agreement, resulting in net proceeds of approximately $497 and $19,479, respectively. The Company did not sell any shares of common stock at-the-market under the 2020 Sales Agreement in 2020. In August 2021, the Company entered into the Amended Sales Agreement with JonesTrading, which amends the 2020 Sales Agreement to allow the issuance and sale of up to $80,000 in shares of the Company's common stock, from time to time. The Company has not sold any shares of common stock at-the-market under the 2021 ATM Facility as of September 30, 2021.

Stock-Based Awards

Stock-Based Awards	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Awards	Stock-Based Awards 2014 Stock Incentive Plan The Company’s 2014 Stock Incentive Plan (the “2014 Plan”) provides for the Company to grant incentive stock options or nonqualified stock options, restricted stock awards, unrestricted stock awards or restricted stock units to employees, directors and consultants of the Company. The 2014 Plan is administered by the board of directors, or at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or their committee if so delegated, except that the exercise price per share of the stock options may not be less than 100% of the fair market value of a share of the Company’s common stock on the date of grant and the term of the stock options may not be greater than ten years. As of December 31, 2018, all remaining shares available under the 2014 Plan were transferred to the Company’s 2018 Stock Option and Incentive Plan (the “2018 Plan”). 2018 Stock Option and Incentive Plan In April 2018, the Company’s 2018 Plan was approved by its stockholders and became effective. The 2018 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock units, restricted stock awards, unrestricted stock awards, cash-based awards and dividend equivalent rights to the Company’s officers, employees, non-employee directors and other key persons (including consultants). The number of shares initially reserved for issuance under the 2018 Plan was 1,545,454, plus the shares of common stock remaining available for issuance under the 2014 Plan, which shall be cumulatively increased each January 1 by 4% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or such lesser number of shares determined by the Company’s board of directors or compensation committee of the board of directors. The shares of common stock underlying any awards that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of stock, expire or are otherwise terminated (other than by exercise) under the 2018 Plan and the 2014 Plan will be added back to the shares of common stock available for issuance under the 2018 Plan. As of September 30, 2021, 855,968 shares were available for future issuance under the 2018 Plan. Stock options granted under the 2014 Plan and 2018 Plan to employees generally vest over four years and expire after ten years. Stock Options The following table summarizes the Company’s stock option activity since December 31, 2020: Number of Weighted Weighted Aggregate (in years) Outstanding as of December 31, 2020 6,011,126 $ 5.55 7.28 $ 24,912 Granted 1,725,605 9.24 Exercised (486,632) 3.99 Forfeited (242,848) 5.51 Outstanding as of September 30, 2021 7,007,251 $ 6.57 7.17 $ 15,121 Options exercisable at September 30, 2021 4,427,353 $ 6.12 6.27 $ 11,324 Vested and expected to vest at September 30, 2021 7,007,251 $ 6.57 7.17 $ 15,121 The weighted average grant-date fair value per share of stock options granted during the nine months ended September 30, 2021 and year ended December 31, 2020 was $6.50 and $2.11, respectively. As of September 30, 2021 and December 31, 2020, there were outstanding stock options held by non-employees for the purchase of 276,570 and 253,971 shares of common stock, respectively, with service-based vesting conditions. 2018 Employee Stock Purchase Plan In April 2018, the Company’s 2018 Employee Stock Purchase Plan (the “ESPP”) was approved by its stockholders and became effective. A total of 256,818 shares of common stock were initially reserved for issuance under this plan. In addition, the number of shares of common stock that may be issued under the ESPP automatically increased on January 1, 2019, and shall increase each January 1 thereafter through January 1, 2028, by the lesser of (i) 1% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 and (ii) such lesser number of shares as determined by the administrator of the Company’s ESPP. As of September 30, 2021, a total of 1,084,476 shares of common stock were reserved for issuance under this plan. For the three and nine months ended September 30, 2021 and 2020, the Company issued 27,522 and 46,899, and 40,147 and 89,172 shares of common stock under the ESPP, respectively. Restricted Stock Units The Company has granted restricted stock units (“RSUs”) with service-based vesting conditions. RSUs represent the right to receive shares of common stock upon meeting specified vesting requirements. Unvested shares of restricted common stock may not be sold or transferred by the holder. These restrictions lapse according to the service-based vesting conditions of each award. In 2020, the Company granted 1,071,400 RSUs that vest in full after eighteen-months as long as the individual remains an employee of the Company at such time. The table below summarizes the Company’s restricted stock unit activity since December 31, 2020: Number of Weighted Unvested restricted stock units as of December 31, 2020 1,043,300 $ 3.21 Granted — — Vested (997,400) 3.21 Forfeited (45,900) 3.18 Unvested restricted stock units as of September 30, 2021 — $ — The expense related to RSUs granted to employees was $124 and $1,103, and $552 and $1,541 for the three and nine months ended September 30, 2021 and 2020, respectively. Stock-Based Compensation The Company recorded stock-based compensation expense related to stock options and restricted stock unit awards in the following expense categories of its condensed consolidated statements of operations and comprehensive loss: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Research and development expenses $ 848 $ 709 $ 2,535 $ 2,134 General and administrative expenses 1,196 1,254 4,168 3,679 $ 2,044 $ 1,963 $ 6,703 $ 5,813

Debt

Debt	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Debt	Debt On November 22, 2019, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with K2HV (the “Lender”). The Lender made available to the Company term loans in an aggregate principal amount of up to $25,000 under the Loan Agreement. The Company plans to use the proceeds of the term loans to support clinical development as well as for working capital and general corporate purposes. The Loan Agreement provides a term loan commitment of $25,000 in three potential tranches: (i) a $7,500 term loan facility funded on November 22, 2019 (the “First Tranche Term Loan”), (ii) a $10,000 term loan facility funded on June 5, 2020 (the “Second Tranche Term Loan”), and (iii) a $7,500 term loan facility (the “Third Tranche Term Loan”). All three of these term loans have a maturity date of December 1, 2023. Borrowings under all three loan facilities bear interest at a floating per annum rate equal to the greater of (i) 8.65% and (ii) the Prime Rate plus 3.90%. The Company is permitted to make interest-only payments on the First Tranche Term Loan for the first eighteen months following the funding date. The interest-only period can be extended by an additional six months, subject to the funding of the Second Tranche Term Loan; and by an additional six months, subject to the funding of the Third Tranche Term Loan. The term of the combined facility will be 48 months, with repayment in monthly installments commencing at the end of the resulting interest-only period as outlined above through the end of the 48-month term. The Company is obligated to pay a final fee equal to 4.45% of the aggregate amount of the term loans funded, such payment to occur upon the earliest of (i) the maturity date, (ii) the acceleration of the term loans, and (iii) the prepayment of the term loans. The Company has the option to prepay all, but not less than all, of the outstanding principal balance of the term loans under the Loan Agreement. If the Company prepays all of the term loans prior to the maturity date, it will pay the Lender a prepayment penalty fee based on a percentage of the outstanding principal balance, equal to 5% if the payment occurs on or before 24 months after the initial funding date, 3% if the prepayment occurs more than 24 months after, but on or before 36 months after the initial funding date, or 1% if the prepayment occurs more than 36 months after the initial funding date. The Lender may, at its option, elect to convert any portion of no more than $4,000 of the then outstanding term loan amount and all accrued and unpaid interest thereon into shares of the Company’s common stock at a conversion price of $1.56 per share. The Company determined that the embedded conversion option is not required to be separated from the term loan. The embedded conversion option meets the derivative accounting scope exception since the embedded conversion option is indexed to the Company’s own common stock and qualifies for classification within stockholders’ equity. The Company recognized a beneficial conversion feature of $2,101, which represents the difference between the commitment date stock price of $2.33 per share and the conversion price of $1.56 per share. The beneficial conversion feature was recorded as a discount on the term loan and is accreted to interest expense using the effective interest method over the term of the loan. The effective interest rate of the term loan as of September 30, 2021 is 12.36%. The Company’s obligations under the Loan Agreement are secured by a first priority security interest in substantially all of its assets. The Loan Agreement contains customary representations, warranties and also includes customary events of default, including payment defaults, breaches of covenants, change of control and a material adverse effect clause. Upon the occurrence of an event of default, a default interest rate of an additional 5.00% per annum may be applied to the outstanding loan balances, and the Lender may declare all outstanding obligations immediately due and payable and exercise all of its rights and remedies as set forth in the Loan Agreement and under applicable law. In June 2020, the Company drew down the Second Tranche Term Loan and received an additional $10,000 in proceeds. The Company is permitted to make interest-only payments on the First Tranche Term Loan and the Second Tranche Term Loan until January 2022 in accordance with the terms of the Loan Agreement. In August 2020, the Lender elected to convert $2,000 of the outstanding term loan amount into 1,282,050 shares of the Company's common stock, in accordance with the Loan Agreement. In February 2021, the Lender elected to convert $1,500 of the outstanding term loan amount into 961,538 shares of the Company's common stock, in accordance with the Loan Agreement. The Company recognized $563 of interest expense in the nine months ended September 30, 2021 from accelerating amortization of the beneficial conversion feature and debt discount as a result of the conversion in February 2021. As of September 30, 2021, the outstanding principal balance was $14,000. On October 1, 2021, the Company entered into a First Amendment to Loan and Security Agreement (the “Loan Amendment”) with the Lender, which amends the existing Loan Agreement. Under the Loan Amendment, the Lender made available to the Company term loans in an aggregate principal amount of up to $50,000, in three potential tranches: (i) a $25,000 term loan facility (including refinancing of the Company’s outstanding amounts under the Existing Loan Agreement) funded on October 1, 2021, (ii) up to a $15,000 term loan facility, and (iii) a $10,000 term loan facility. All three of these tranches have a maturity date of October 1, 2025. Borrowings under all three tranches of the term loan facility bear interest at a floating per annum rate equal to the greater of (i) 8.50% and (ii) the sum of (A) the greater of (x) the prime rate last quoted in The Wall Street Journal (or a comparable replacement rate if The Wall Street Journal ceases to quote such rate) or (y) 3.25%, plus (B) 5.25%. The Company is permitted to make interest-only payments on the outstanding principal balance of the term loan for approximately nineteen months following the funding date. The interest-only period can be extended by an additional nine months, subject to the Company raising net cash proceeds from financing activities (including without limitation sales of the Company's securities and up-front or milestone payments pursuant to existing or new strategic partnerships), in an aggregate amount of at least $100,000. The term of the loan facility is 48 months, with repayment in monthly installments commencing at the end of the resulting interest-only period as outlined above through the end of the 48-month term. The Company is obligated to pay a final fee equal to (i) 4.25% of the aggregate amount of the term loans funded, such payment to occur upon the earliest of (i) the maturity date, (ii) the acceleration of the term loans, and (iii) the prepayment of the term loans and (ii) $779 on the earlier of December 1, 2023 or the prepayment of the term loans. The Company has the option to prepay all, but not less than all, of the outstanding principal balance of the term loans under the Loan Amendment. If the Company prepays all of the term loans prior to the maturity date, it will pay the Lender a prepayment penalty fee based on a percentage of the outstanding principal balance, equal to 5% if the payment occurs on or before 24 months after the initial funding date, 3% if the prepayment occurs more than 24 months after, but on or before 36 months after the initial funding date, or 1% if the prepayment occurs more than 36 months after the initial funding date. The Lender may, at its option, elect to convert any portion of no more than $4,500 of the then outstanding term loan amount and all accrued and unpaid interest thereon into shares of the Company’s common stock at a conversion price of (i) with respect to the first $500 converted, $1.56 per share and (ii) with respect to any additional amounts converted in excess of $500, $7.81 per share. The Company’s obligations under the Loan Amendment are secured by a first priority security interest in substantially all of its assets. The Loan Amendment contains customary representations, warranties and also includes customary events of default, including payment defaults, breaches of covenants, change of control and a material adverse effect clause. Upon the occurrence of an event of default, a default interest rate of an additional 5.00% per annum may be applied to the outstanding loan balances, and the Lender may declare all outstanding obligations immediately due and payable and exercise all of its rights and remedies as set forth in the Loan Amendment and under applicable law. The Company recorded interest expense related to the loan facility of $421 and $1,858, and $1,469 and $2,237 for the three and nine months ended September 30, 2021 and 2020, respectively. The fair value of the loan at September 30, 2021 approximates its face amount due to the floating interest rate. Future principal debt payments on the loan payable reflecting the amended terms are as follows: September 30, 2021 2021 $ — 2022 — 2023 3,739 2024 5,378 2025 4,883 Total principal payments 14,000 Final fee due at maturity in 2025 779 Total principal payments and final fee 14,779 Unamortized debt discount and final fee (593) Note payable $ 14,186

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic and diluted net loss per share attributable to common stockholders was calculated as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Basic and diluted net loss per share attributable to common stockholders: Numerator: Net loss $ (19,893) $ (15,774) $ (54,435) $ (8,011) Denominator: Weighted average common shares outstanding — basic and diluted 45,236,775 40,004,555 43,510,078 33,822,682 Net loss per share attributable to common stockholders — basic and diluted $ (0.44) $ (0.39) $ (1.25) $ (0.24) The Company’s potential dilutive securities have been excluded from the computation of diluted net loss per share for the three and nine months ended September 30, 2021, as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated above because including them would have had an anti-dilutive effect: September 30, 2021 2020 Stock options to purchase common stock 7,007,251 6,114,639 Shares to be issued under the 2018 ESPP 1,084,476 724,305 RSUs issued and expected to vest — 1,051,900 Shares available from conversion of note payable 320,514 1,282,050 8,412,241 9,172,894

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company did not provide for any income taxes for the three and nine months ended September 30, 2021 or 2020. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of September 30, 2021 and December 31, 2020. Management reevaluates the positive and negative evidence at each reporting period. As of September 30, 2021 and December 31, 2020, the Company had no accrued interest or tax penalties recorded. The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. The Company's tax years are still open under statute from 2017 to present. All years may be examined to the extent the tax credit or net operating loss carryforwards are used in future periods. There are currently no federal or state audits.

Leases

Leases	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Leases	Leases Sublease Agreement with EQRx, Inc. In the three and nine months ended September 30, 2021 and 2020, the Company recognized sublease income of $656 and $1,969, and $792 and $1,885, respectively. As of September 30, 2021, future undiscounted cash inflows under the sublease are as follows: Year Ending December 31, 2021 $ 709 2022 2,884 2023 241 $ 3,834

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings The Company is not currently party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to its legal proceedings. Adimab Development and Option Agreement During the three and nine months ended September 30, 2021, the Company recognized research and development expense related to milestones achieved under the agreement of $1,500 and $3,000, respectively. During the nine months ended September 30, 2020, the Company recognized research and development expense related to milestones achieved under the agreement of $2,000. The Company did not recognize research and development expense related to milestones achieved under the agreement in the three months ended September 30, 2020.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Novartis Institutes for BioMedical Research, Inc. Novartis is a related party because it is a greater than 5% stockholder of the Company. In January 2016, the Company entered into the Novartis Agreement and sold 2,000,000 shares of its Series A-1 Preferred Stock to Novartis for gross proceeds of $13,500. In addition, concurrent with the Company’s initial public offering of common stock, the Company issued Novartis 766,666 shares of its common stock at $15.00 per share, for proceeds of $11,500 in a private placement. The Company did not recognize any collaboration revenue - related party under the Novartis Agreement in the nine months ended September 30, 2021. The Company recognized $38,592 in collaboration revenue - related party in the nine months ended September 30, 2020. The Company did not recognize any collaboration revenue - related party under the Novartis Agreement in the three months ended September 30, 2021 or 2020. As of September 30, 2021 and 2020, no amounts were due from Novartis. During the three and nine months ended September 30, 2021 and 2020, the Company made no cash payments to Novartis related to the Novartis Agreement. Vaccinex, Inc. On November 30, 2017, the Company entered into a research agreement (the “Vaccinex Research Agreement”) with Vaccinex, Inc. (“Vaccinex”), pursuant to which Vaccinex used its technology to assist the Company with identifying and selecting experimental human monoclonal antibodies against targets selected by the Company. On March 23, 2021, the Company exercised its option under the Vaccinex Research Agreement to enter into an exclusive license agreement (the “Vaccinex License Agreement”) to certain antibodies generated under the Vaccinex Research Agreement. The Company’s Chairman of the Board and former Chief Executive Officer is a member of the board of directors of Vaccinex. During the nine

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsOn October 1, 2021, the Company entered into the Loan Amendment, which amends the existing Loan Agreement. Refer to Note 8 for further discussion of the terms of the Loan Amendment.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and its wholly owned subsidiary, Surface Securities Corporation, a Massachusetts corporation, after elimination of all intercompany accounts and transactions. The accounting policies followed in the preparation of the interim condensed consolidated financial statements are consistent in all material respects with those presented in Note 2 to the financial statements included in the Company’s Annual Report on Form 10-K, filed with the Securities and Exchange Commission (the “SEC”) on March 9, 2021.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, revenue recognition and the accrual of research and development expenses. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from the Company’s estimates.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying condensed consolidated financial statements are unaudited. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of September 30, 2021 and the results of its operations and its cash flows for the nine months ended September 30, 2021 and 2020. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2021 and 2020 are also unaudited. The condensed balance sheet at December 31, 2020, was derived from audited annual financial statements but does not contain all of the footnote disclosures from the annual financial statements. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, any other interim periods, or any future year period.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13") , which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss model. It also eliminates the concept of other-than-temporary impairment and requires credit losses related to available-for-sale debt securities to be recorded through an allowance for credit losses rather than as a reduction in the amortized cost basis of the securities. These changes may result in earlier recognition of credit losses. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments—Credit Losses , which narrowed the scope and changed the effective date for non-public entities for ASU 2016-13. The FASB subsequently issued supplemental guidance within ASU No. 2019-05, Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief ("ASU 2019-05") . ASU 2019-05 provides an option to irrevocably elect the fair value option for certain financial assets previously measured at amortized cost basis. For public entities that are Securities and Exchange Commission filers, excluding entities eligible to be smaller reporting companies, ASU 2016-13 is effective for annual periods beginning after December 15, 2019, including interim periods within those fiscal years. For all other entities, ASU 2016-13 is effective for annual periods beginning after December 15, 2022, including interim periods within those fiscal years. Early adoption is permitted. This standard will be effective for the Company on January 1, 2023. The Company is currently evaluating the potential impact that this standard may have on its condensed consolidated financial statements and related disclosures. Other accounting standards that have been issued by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s financial statements upon adoption.

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Summary of Fair Value of Available-for-sale Marketable Debt Securities by Type of Security	As of September 30, 2021, the fair value of available-for-sale marketable debt securities by type of security was as follows: September 30, 2021 Amortized Gross Gross Fair Marketable debt securities: U.S. Treasury notes $ 73,017 $ 9 (10) $ 73,016 U.S. government agency bonds 15,836 1 (3) 15,834 $ 88,853 $ 10 $ (13) $ 88,850
Summary of Available-for-sale Debt Securities by Contractual Maturity	The amortized cost and fair value of the Company’s available-for-sale debt securities by contractual maturity are summarized as follows: September 30, 2021 Amortized Fair Maturing in one year or less $ 56,568 $ 56,576 Maturing after one year 32,285 32,274 $ 88,853 $ 88,850

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured at Fair Value on Recurring Basis	The following tables present information about the Company’s financial assets that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values: Fair Value Measurements as of September 30, 2021 using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 44,686 $ — $ — $ 44,686 Cash 23 — — 23 Marketable securities: U.S. Treasury notes — 73,016 — 73,016 U.S. government agency bonds — 15,834 — 15,834 $ 44,709 $ 88,850 $ — $ 133,559 Fair Value Measurements as of December 31, 2020 using: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 139,266 $ — $ — $ 139,266 $ 139,266 $ — $ — $ 139,266

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Collaboration Revenue	For the three and nine months ended September 30, 2021 and 2020, the Company recognized the following totals of collaboration revenue – related party: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Collaboration revenue - related party $ — $ — $ — $ 38,592 For the three and nine months ended September 30, 2021 and 2020 , the Company recognized the following totals of license related revenue: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 License related revenue $ 392 $ — $ 2,532 $ —

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Summary of Stock Option Activity	The following table summarizes the Company’s stock option activity since December 31, 2020: Number of Weighted Weighted Aggregate (in years) Outstanding as of December 31, 2020 6,011,126 $ 5.55 7.28 $ 24,912 Granted 1,725,605 9.24 Exercised (486,632) 3.99 Forfeited (242,848) 5.51 Outstanding as of September 30, 2021 7,007,251 $ 6.57 7.17 $ 15,121 Options exercisable at September 30, 2021 4,427,353 $ 6.12 6.27 $ 11,324 Vested and expected to vest at September 30, 2021 7,007,251 $ 6.57 7.17 $ 15,121
Summary of Restricted Stock Unit Activity	The table below summarizes the Company’s restricted stock unit activity since December 31, 2020: Number of Weighted Unvested restricted stock units as of December 31, 2020 1,043,300 $ 3.21 Granted — — Vested (997,400) 3.21 Forfeited (45,900) 3.18 Unvested restricted stock units as of September 30, 2021 — $ —
Summary of Stock-Based Compensation Expense Related to Stock Options and Restricted Stock Awards	The Company recorded stock-based compensation expense related to stock options and restricted stock unit awards in the following expense categories of its condensed consolidated statements of operations and comprehensive loss: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Research and development expenses $ 848 $ 709 $ 2,535 $ 2,134 General and administrative expenses 1,196 1,254 4,168 3,679 $ 2,044 $ 1,963 $ 6,703 $ 5,813

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Schedule of Future Principal Debt Payments on the Loan Payable	Future principal debt payments on the loan payable reflecting the amended terms are as follows: September 30, 2021 2021 $ — 2022 — 2023 3,739 2024 5,378 2025 4,883 Total principal payments 14,000 Final fee due at maturity in 2025 779 Total principal payments and final fee 14,779 Unamortized debt discount and final fee (593) Note payable $ 14,186

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Basic and diluted net loss per share attributable to common stockholders: Numerator: Net loss $ (19,893) $ (15,774) $ (54,435) $ (8,011) Denominator: Weighted average common shares outstanding — basic and diluted 45,236,775 40,004,555 43,510,078 33,822,682 Net loss per share attributable to common stockholders — basic and diluted $ (0.44) $ (0.39) $ (1.25) $ (0.24)
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated above because including them would have had an anti-dilutive effect: September 30, 2021 2020 Stock options to purchase common stock 7,007,251 6,114,639 Shares to be issued under the 2018 ESPP 1,084,476 724,305 RSUs issued and expected to vest — 1,051,900 Shares available from conversion of note payable 320,514 1,282,050 8,412,241 9,172,894

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Schedule of Future Undiscounted Cash Inflows Under Sublease	As of September 30, 2021, future undiscounted cash inflows under the sublease are as follows: Year Ending December 31, 2021 $ 709 2022 2,884 2023 241 $ 3,834

Nature of the Business - Additi

Nature of the Business - Additional Information (Details) - USD ($)	Aug. 05, 2021	May 22, 2020	May 31, 2020	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Accumulated deficit				$ (116,693,000)	$ (116,693,000)	$ (62,258,000)
Operating expenses and capital expenditure requirements (in months)					12 months
2020 ATM Facility
Class of Stock [Line Items]
Common stock, issued (in shares)				69,785	2,303,545	0
Net proceeds from issuance of common stock				$ 497,000	$ 19,479,000
2020 ATM Facility | Maximum
Class of Stock [Line Items]
Gross proceeds from issuance of common stock		$ 50,000,000	$ 50,000,000
Percentage of gross proceeds of shares sold for compensation (as a percent)		3.00%
Net proceeds from issuance of common stock				$ 497,000
2021 ATM Facility
Class of Stock [Line Items]
Common stock, issued (in shares)				0	0
2021 ATM Facility | Maximum
Class of Stock [Line Items]
Gross proceeds from issuance of common stock	$ 80,000,000
Percentage of gross proceeds of shares sold for compensation (as a percent)	3.00%

Marketable Securities - Summary

Marketable Securities - Summary of Fair Value of Available-for-sale Marketable Debt Securities by Type of Security (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 88,853,000
Gross Unrealized Gains	10,000
Gross Unrealized Losses	(13,000)
Fair Value	88,850,000	$ 0
U.S. Treasury notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	73,017,000
Gross Unrealized Gains	9,000
Gross Unrealized Losses	(10,000)
Fair Value	73,016,000
U.S. government agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,836,000
Gross Unrealized Gains	1,000
Gross Unrealized Losses	(3,000)
Fair Value	$ 15,834,000

Marketable Securities - Summa_2

Marketable Securities - Summary of Fair Value of Available-for-sale Debt Securities by Contractual Maturity (Details) $ in Thousands	Sep. 30, 2021USD ($)
Amortized Cost
Maturing in one year or less	$ 56,568
Maturing after one year	32,285
Amortized Cost	88,853
Fair Value
Maturing in one year or less	56,576
Maturing after one year	32,274
Fair Value	$ 88,850

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Available-for-sale marketable debt securities	$ 88,850,000	$ 0
Investments in other-than-temporary decline in fair value	$ 0	$ 0

Fair Value of Financial Assets

Fair Value of Financial Assets - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 88,850,000	$ 0
U.S. Treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	73,016,000
U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	15,834,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured on recurring basis	133,559,000	139,266,000
Fair Value, Measurements, Recurring | U.S. Treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	73,016,000
Fair Value, Measurements, Recurring | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	15,834,000
Fair Value, Measurements, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	44,686,000	139,266,000
Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	23,000
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured on recurring basis	44,709,000	139,266,000
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Fair Value, Measurements, Recurring | Level 1 | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Fair Value, Measurements, Recurring | Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	44,686,000	139,266,000
Fair Value, Measurements, Recurring | Level 1 | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	23,000
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured on recurring basis	88,850,000	0
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	73,016,000
Fair Value, Measurements, Recurring | Level 2 | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	15,834,000
Fair Value, Measurements, Recurring | Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 2 | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured on recurring basis	0	0
Fair Value, Measurements, Recurring | Level 3 | U.S. Treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Fair Value, Measurements, Recurring | Level 3 | U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Fair Value, Measurements, Recurring | Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	$ 0
Fair Value, Measurements, Recurring | Level 3 | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 0

Collaboration and License Agr_3

Collaboration and License Agreements - Additional Information (Details)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2020USD ($)	Jan. 31, 2016target	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)obligation	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue - related party			$ 0	$ 0	$ 0	$ 38,592,000
License related revenue			392,000	0	2,532,000	0
Novartis Collaboration
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of option targets | target		4
Number of option targets purchased | target		3
Novartis Collaboration | Novartis Institutes for Biomedical Research, Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue - related party	$ 38,592,000		0	0	0	38,592,000
Novartis Collaboration | Novartis Institutes for Biomedical Research, Inc. | Development Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment					325,000,000
Novartis Collaboration | Novartis Institutes for Biomedical Research, Inc. | Sales Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment					$ 200,000,000
GSK Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract with customer, expiration period					10 years
Number of performance obligations | obligation					3
Transaction price			90,942,000		$ 90,942,000
Revenue performance obligation			912,000		912,000
GSK Agreement | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License related revenue			392,000	$ 0	2,532,000	$ 0
GSK Agreement | License | Transferred at Point in Time
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment			85,000,000		85,000,000
License related revenue							$ 85,000
GSK Agreement | License | Transferred over Time
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional payments to be received			4,952,000		4,952,000
GSK Agreement | Supply Services
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License related revenue			48,000		709,000
GSK Agreement | Transition Services
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License related revenue			344,000		1,823,000
GSK Agreement | Transition Services | Transferred over Time
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional payments to be received			$ 990,000		990,000
GSK Agreement | Clinical Milestone Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment					90,000
GSK Agreement | Regulatory Milestone Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment					155,000
GSK Agreement | Sales Milestone Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment					$ 485,000

Collaboration and License Agr_4

Collaboration and License Agreements - Schedule of Collaboration Revenue (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue - related party		$ 0	$ 0	$ 0	$ 38,592,000
License related revenue		392,000	0	2,532,000	0
GSK Agreement | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License related revenue		392,000	0	2,532,000	0
Novartis Institutes for Biomedical Research, Inc. | Novartis Collaboration
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue - related party	$ 38,592,000	$ 0	$ 0	$ 0	$ 38,592,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details)	Aug. 05, 2021USD ($)	May 22, 2020USD ($)	May 31, 2020USD ($)	May 31, 2019USD ($)	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020shares	Sep. 30, 2021USD ($)vote$ / sharesshares	Sep. 30, 2020USD ($)shares	Dec. 31, 2020$ / sharesshares	Sep. 30, 2020USD ($)shares
Subsidiary, Sale of Stock [Line Items]
Common stock, authorized (in shares) | shares					150,000,000		150,000,000		150,000,000
Common stock, par value (in dollars per share) | $ / shares					$ 0.0001		$ 0.0001		$ 0.0001
Number of votes entitled by each share of common stock holder | vote							1
Dividends, declared or paid							$ 0
Capital common shares reserved for future issuance (in shares) | shares					33,878,328		33,878,328		22,728,991
2019 ATM Facility
Subsidiary, Sale of Stock [Line Items]
Common stock, issued (in shares) | shares						0		11,218,593		11,229,174
Net proceeds from issuance of common stock								$ 29,086,000		$ 29,110,000
2020 ATM Facility
Subsidiary, Sale of Stock [Line Items]
Common stock, issued (in shares) | shares					69,785		2,303,545		0
Net proceeds from issuance of common stock					$ 497,000		$ 19,479,000
2021 ATM Facility
Subsidiary, Sale of Stock [Line Items]
Common stock, issued (in shares) | shares					0		0
Maximum | 2019 ATM Facility
Subsidiary, Sale of Stock [Line Items]
Gross proceeds from issuance of common stock				$ 30,000,000
Maximum | 2020 ATM Facility
Subsidiary, Sale of Stock [Line Items]
Gross proceeds from issuance of common stock		$ 50,000,000	$ 50,000,000
Net proceeds from issuance of common stock					$ 497,000
Maximum | 2021 ATM Facility
Subsidiary, Sale of Stock [Line Items]
Gross proceeds from issuance of common stock	$ 80,000,000

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2018	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 2,044	$ 1,963	$ 6,703	$ 5,813
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		1,196	1,254	4,168	3,679
2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation cost		12,433		$ 12,433
Unrecognized stock-based compensation cost, weighted-average period (in years)				1 year 7 months 2 days
Chief Executive Officer | General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 28		$ 449
Stock options to purchase common stock | Non-Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock converted under option plan (in shares)		276,570		276,570		253,971
RSUs issued and expected to vest
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting period (in years)						18 months
RSUs issued and expected to vest | Granted to Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 124	$ 552	$ 1,103	$ 1,541
2014 Plan | Stock options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of exercise price per share of stock options to fair market value of share of common stock (as a percent)				100.00%
Stock options granted expiry period (in years)				10 years
Weighted average grant-date fair value per share of stock options granted (in dollars per share)				$ 6.50		$ 2.11
2018 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock to be issued (in shares)	1,545,454
Percentage of authorized number of shares of common stock outstanding (as a percent)	4.00%
Number of shares of common stock converted under option plan (in shares)		7,007,251		7,007,251		6,011,126
2018 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance (in shares)		855,968		855,968
2018 Stock Option and Incentive Plan | 2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock to be issued (in shares)	256,818	1,084,476		1,084,476
Percentage of authorized number of shares of common stock outstanding (as a percent)	1.00%
Number of shares of common stock issued (in shares)		27,522	40,147	46,899	89,172
2014 Plan and 2018 Plan | Stock options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted expiry period (in years)				10 years
Stock options granted vesting period (in years)				4 years

Stock-Based Awards - Summary of

Stock-Based Awards - Summary of Stock Option Activity (Details) - 2018 Stock Option and Incentive Plan $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Stock Option Activity Under Plans
Number of Shares, outstanding beginning balance (in shares) | shares	6,011,126
Number of Shares, granted (in shares) | shares	1,725,605
Number of Shares, exercised (in shares) | shares	(486,632)
Number of Shares, forfeited (in shares) | shares	(242,848)
Number of Shares, outstanding ending balance (in shares) | shares	7,007,251	6,011,126
Number of Shares, options exercisable at September 30, 2021 (in shares) | shares	4,427,353
Number of Shares, vested and expected to vest at September 30, 2021 (in shares) | shares	7,007,251
Stock Options Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding beginning balance (in dollars per share) | $ / shares	$ 5.55
Weighted Average Exercise Price, Granted (in dollars per share) | $ / shares	9.24
Weighted Average Exercise Price, Exercised (in dollars per share) | $ / shares	3.99
Weighted Average Exercise Price, Forfeited (in dollars per share) | $ / shares	5.51
Weighted Average Exercise Price, Outstanding ending balance (in dollars per share) | $ / shares	6.57	$ 5.55
Weighted Average Exercise Price, Options exercisable at September 30, 2021 (in dollars per share) | $ / shares	6.12
Weighted Average Exercise Price, Vested and expected to vest at September 30, 2021 (in dollars per share) | $ / shares	$ 6.57
Stock Option Activity, Additional Disclosures
Weighted Average Remaining Contractual Term (in years), Outstanding	7 years 2 months 1 day	7 years 3 months 10 days
Weighted Average Remaining Contractual Term (in years), Options exercisable	6 years 3 months 7 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	7 years 2 months 1 day
Aggregate Intrinsic Value (in USD) | $	$ 15,121	$ 24,912
Aggregate Intrinsic Value, Options exercisable at September 30, 2021 (in USD) | $	11,324
Aggregate Intrinsic Value, Vested and expected to vest at September 30, 2021 (in USD) | $	$ 15,121

Stock-Based Awards - Summary _2

Stock-Based Awards - Summary of Restricted Stock Unit Activity (Details) - RSUs issued and expected to vest - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Restricted Stock Unit Activity
Unvested restricted stock units, beginning balance (in shares)	1,043,300
Unvested restricted stock units, Granted (in shares)	0	1,071,400
Unvested restricted stock units, Vested (in shares)	(997,400)
Unvested restricted stock units, Forfeited (in shares)	(45,900)
Unvested restricted stock units, ending balance (in shares)	0	1,043,300
Weighted Average Grant Date Fair Value
Weighted Average Grant-Date Fair Value, beginning balance (in dollars per share)	$ 3.21
Weighted Average Grant-Date Fair Value, Granted (in dollars per share)	0
Weighted Average Grant-Date Fair Value, Vested (in dollars per share)	3.21
Weighted Average Grant-Date Fair Value, Forfeited (in dollars per share)	3.18
Weighted Average Grant-Date Fair Value, ending balance (in dollars per share)	$ 0	$ 3.21

Stock-Based Awards - Summary _3

Stock-Based Awards - Summary of Stock-Based Compensation Expense Related to Stock Options and Restricted Stock Awards (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,044	$ 1,963	$ 6,703	$ 5,813
Research and development expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	848	709	2,535	2,134
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,196	$ 1,254	$ 4,168	$ 3,679

Debt - Additional Information (

Debt - Additional Information (Details) - K2 Health Ventures LLC	Oct. 01, 2021USD ($)$ / shares	Nov. 22, 2019USD ($)tranche$ / shares	Feb. 28, 2021USD ($)shares	Aug. 31, 2020USD ($)shares	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)
Loan and Security Agreement
Debt Instrument [Line Items]
Commitment date stock price (in dollars per share) | $ / shares		$ 2.33
Effective interest rate (as a percent)					12.36%		12.36%
Loan and Security Agreement | Term Loans
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 25,000,000
Number of potential tranches | tranche		3
Debt instrument interest rate, floating (as a percent)		8.65%
Term of the combined facility (months)		48 months
Final fee percentage (as a percent)		4.45%
Portion of outstanding term loan amount converted			$ 1,500,000	$ 2,000,000
Conversion price per share (USD per share) | $ / shares		$ 1.56
Beneficial conversion feature		$ 2,101,000
Number of shares issued upon conversion of term loan (in shares) | shares			961,538	1,282,050
Amortization of debt discount							$ 563,000
Outstanding term loan principal balance					$ 14,000,000		14,000,000
Interest expense					$ 421,000	$ 1,469,000	$ 1,858,000	$ 2,237,000
Loan and Security Agreement | Term Loans | Maximum
Debt Instrument [Line Items]
Portion of outstanding term loan amount converted		$ 4,000,000
Loan and Security Agreement | Term Loans | Payment Occurs on or before Twenty Four Months after Initial Funding Date
Debt Instrument [Line Items]
Prepayment penalty fee percentage (as a percent)		5.00%
Default interest rate (as a percent)		5.00%
Loan and Security Agreement | Term Loans | Prepayment Occurs More than Twenty Four Months after, but on or before Thirty Six Months after Initial Funding Date
Debt Instrument [Line Items]
Prepayment penalty fee percentage (as a percent)		3.00%
Loan and Security Agreement | Term Loans | Prepayment Occurs More than Thirty Six Months after Initial Funding Date
Debt Instrument [Line Items]
Prepayment penalty fee percentage (as a percent)		1.00%
Loan and Security Agreement | Term Loans | Prime Rate
Debt Instrument [Line Items]
Debt instrument variable rate (as a percent)		3.90%
Loan and Security Agreement | First Tranche Term Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 7,500,000
Debt instrument interest only payment period (months)		18 months
Debt instrument interest only payment extension period subject to funding of second tranche term loan (months)		6 months
Debt instrument interest only payment extension period subject to funding of third tranche term loan (months)		6 months
Loan and Security Agreement | Second Tranche Term Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 10,000,000							$ 10,000,000
Loan and Security Agreement | Third Tranche Term Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 7,500,000
Loan Amendment | Term Loans | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50,000,000
Debt instrument interest rate, floating (as a percent)	8.50%
Debt instrument variable rate (as a percent)	5.25%
Term of the combined facility (months)	48 months
Final fee percentage (as a percent)	4.25%
Debt Instrument, Interest Rate, Stated Percentage	3.25%
Amount of cash from financing activities needed to extend interest-only period	$ 100,000,000
Debt instrument, term, prepayment amount	779,000
Loan Amendment | Term Loans | Subsequent Event | First $500 Converted at $1.56 per share
Debt Instrument [Line Items]
Portion of outstanding term loan amount converted	$ 500,000
Conversion price per share (USD per share) | $ / shares	$ 1.56
Loan Amendment | Term Loans | Subsequent Event | Additional Amounts Converted in Excess of $500 at $7.81 per share
Debt Instrument [Line Items]
Portion of outstanding term loan amount converted	$ 500,000
Conversion price per share (USD per share) | $ / shares	$ 7.81
Loan Amendment | Term Loans | Maximum | Subsequent Event
Debt Instrument [Line Items]
Portion of outstanding term loan amount converted	$ 4,500,000
Loan Amendment | Term Loans | Payment Occurs on or before Twenty Four Months after Initial Funding Date | Subsequent Event
Debt Instrument [Line Items]
Prepayment penalty fee percentage (as a percent)	5.00%
Default interest rate (as a percent)	5.00%
Loan Amendment | Term Loans | Prepayment Occurs More than Twenty Four Months after, but on or before Thirty Six Months after Initial Funding Date | Subsequent Event
Debt Instrument [Line Items]
Prepayment penalty fee percentage (as a percent)	3.00%
Loan Amendment | Term Loans | Prepayment Occurs More than Thirty Six Months after Initial Funding Date | Subsequent Event
Debt Instrument [Line Items]
Prepayment penalty fee percentage (as a percent)	1.00%
Loan Amendment | First Tranche Term Loan | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 25,000,000
Loan Amendment | Second Tranche Term Loan | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	15,000,000
Loan Amendment | Third Tranche Term Loan | Subsequent Event
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 10,000,000

Debt - Schedule of Future Princ

Debt - Schedule of Future Principal Debt Payments on the Loan Payable (Details) - Notes Payable $ in Thousands	Sep. 30, 2021USD ($)
Debt Instrument [Line Items]
2021	$ 0
2022	0
2023	3,739
2024	5,378
2025	4,883
Total principal payments	14,000
Final fee due at maturity in 2025	779
Total principal payments and final fee	14,779
Unamortized debt discount and final fee	(593)
Note payable	$ 14,186

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss	$ (19,893)	$ (18,981)	$ (15,561)	$ (15,774)	$ (14,807)	$ 22,570	$ (54,435)	$ (8,011)
Denominator:
Weighted average common shares outstanding— basic (in shares)	45,236,775			40,004,555			43,510,078	33,822,682
Weighted average common shares outstanding— diluted (in shares)	45,236,775			40,004,555			43,510,078	33,822,682
Net loss per share attributable to common stockholders— basic (in dollars per share)	$ (0.44)			$ (0.39)			$ (1.25)	$ (0.24)
Net loss per share attributable to common stockholders— diluted (in dollars per share)	$ (0.44)			$ (0.39)			$ (1.25)	$ (0.24)

Net Loss per Share - Securities

Net Loss per Share - Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average shares excluded from computation of diluted net income per share attributable to common stockholders (in shares)	8,412,241	9,172,894
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average shares excluded from computation of diluted net income per share attributable to common stockholders (in shares)	7,007,251	6,114,639
Shares to be issued under the 2018 ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average shares excluded from computation of diluted net income per share attributable to common stockholders (in shares)	1,084,476	724,305
RSUs issued and expected to vest
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average shares excluded from computation of diluted net income per share attributable to common stockholders (in shares)	0	1,051,900
Shares available from conversion of note payable
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average shares excluded from computation of diluted net income per share attributable to common stockholders (in shares)	320,514	1,282,050

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income tax provision or benefit	$ 0	$ 0	$ 0	$ 0
Interest and penalties accrued	$ 0		$ 0		$ 0

Leases - Schedule of Future Und

Leases - Schedule of Future Undiscounted Cash Inflows Under Sublease (Details) - Sublease Agreement with EQRx - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lease Agreements [Line Items]
Sublease income	$ 656	$ 792	$ 1,969	$ 1,885
2021	709		709
2022	2,884		2,884
2023	241		241
Total future sublease payments	$ 3,834		$ 3,834

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	$ 14,037,000	$ 9,454,000	$ 37,250,000	$ 30,290,000
Adimab Development | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	$ 1,500,000	$ 0	$ 3,000,000	$ 2,000,000

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Jan. 31, 2020	Jan. 31, 2016	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Preferred stock shares issued to related party (in shares)			0		0		0
Collaboration revenue - related party			$ 0	$ 0	$ 0	$ 38,592,000
Amounts due from related party				0		0
Novartis Institutes for Biomedical Research, Inc. | Novartis Collaboration
Related Party Transaction [Line Items]
Collaboration revenue - related party	$ 38,592,000		0	0	0	38,592,000
Amounts due from related party			0		0
Payment for reimbursement of manufacturing costs incurred			0	0	0	0
Novartis Institutes for Biomedical Research, Inc. | Novartis Collaboration | Minimum
Related Party Transaction [Line Items]
Percentage of share holding (as a percent)		5.00%
Novartis Institutes for Biomedical Research, Inc. | Novartis Collaboration | Series A One Redeemable Convertible Preferred Stock
Related Party Transaction [Line Items]
Preferred stock shares issued to related party (in shares)		2,000,000
Gross proceeds from issuance of preference stock		$ 13,500,000
Novartis Institutes for Biomedical Research, Inc. | Novartis Collaboration | Private Placement
Related Party Transaction [Line Items]
Common stock, issued (in shares)		766,666
Share price (in dollars per share)		$ 15
Proceeds from issuance of private placement		$ 11,500,000
Vaccinex, Inc. | Clinical Milestone Payment
Related Party Transaction [Line Items]
Potential milestones payment					3,500,000
Vaccinex, Inc. | Regulatory Milestone Payment
Related Party Transaction [Line Items]
Potential milestones payment					11,500,000
Vaccinex, Inc. | Vaccinex License Agreement
Related Party Transaction [Line Items]
Due to related party			0	0	0	0
Vaccinex, Inc. | Vaccinex License Agreement | Research and development expenses
Related Party Transaction [Line Items]
Payments to related party			0	0	850,000	0
Vaccinex, Inc. | Vaccinex Research Agreement
Related Party Transaction [Line Items]
Due to related party			50,000	50,000	50,000	50,000
Vaccinex, Inc. | Vaccinex Research Agreement | Research and development expenses
Related Party Transaction [Line Items]
Payments to related party			$ 0	$ 0	$ 0	$ 0