Jounce Therapeutics (JNCE) 10-Q 6 Nov 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Nov. 02, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-37998
Entity Registrant Name	JOUNCE THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	45-4870634
Entity Address, Address Line One	780 Memorial Drive
Entity Address, City or Town	Cambridge,
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	857
Local Phone Number	259-3840
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	JNCE
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	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		39,851,475
Entity Central Index Key	0001640455
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 67,103	$ 53,241
Short-term investments	37,144	115,602
Prepaid expenses and other current assets	3,210	4,854
Total current assets	107,457	173,697
Property and equipment, net	8,097	10,672
Long-term investments	1,034	1,601
Operating lease right-of-use asset	15,567	17,615
Other non-current assets	3,678	2,297
Total assets	135,833	205,882
Current liabilities:
Accounts payable	2,707	2,460
Accrued expenses	10,323	8,907
Operating lease liability, current	3,176	2,901
Other current liabilities	74	132
Total current liabilities	16,280	14,400
Operating lease liability, net of current portion	14,466	16,889
Total liabilities	30,746	31,289
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value: 5,000 shares authorized at September 30, 2020 and December 31, 2019; no shares issued or outstanding at September 30, 2020 or December 31, 2019	0	0
Common stock, $0.001 par value: 160,000 shares authorized at September 30, 2020 and December 31, 2019; 34,287 and 33,738 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	34	34
Additional paid-in capital	291,481	281,664
Accumulated other comprehensive income	45	54
Accumulated deficit	(186,473)	(107,159)
Total stockholders’ equity	105,087	174,593
Total liabilities and stockholders’ equity	$ 135,833	$ 205,882

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock (in dollars per share)	$ 0.001	$ 0.001
Preferred stock shares authorized (in shares)	5,000,000	5,000,000
Preferred stock shares issued (in shares)	0	0
Preferred stock shares outstanding (in shares)	0	0
Common stock (in dollars per share)	$ 0.001	$ 0.001
Common stock shares authorized (in shares)	160,000,000	160,000,000
Common stock shares issued (in shares)	34,287,000	33,738,000
Common stock shares outstanding (in shares)	34,287,000	33,738,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue:
License and collaboration revenue—related party	$ 0	$ 119,445	$ 0	$ 147,872
Operating expenses:
Research and development	18,002	15,115	58,671	50,525
General and administrative	7,102	6,483	21,867	20,998
Total operating expenses	25,104	21,598	80,538	71,523
Operating (loss) income	(25,104)	97,847	(80,538)	76,349
Other income, net	203	1,025	1,238	3,177
(Loss) income before provision for income taxes	(24,901)	98,872	(79,300)	79,526
Provision for income taxes	2	12	14	36
Net (loss) income	$ (24,903)	$ 98,860	$ (79,314)	$ 79,490
Net income (loss) per share, basic (in dollars per share)	$ (0.73)	$ 2.99	$ (2.33)	$ 2.41
Net income (loss) per share, diluted (in dollars per share)	$ (0.73)	$ 2.90	$ (2.33)	$ 2.33
Weighted-average common shares outstanding, basic (in shares)	34,159	33,112	34,081	33,015
Weighted-average common shares outstanding, diluted (in shares)	34,159	34,141	34,081	34,160
Comprehensive (loss) income:
Net (loss) income	$ (24,903)	$ 98,860	$ (79,314)	$ 79,490
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for-sale securities	(88)	(57)	(9)	156
Comprehensive (loss) income	$ (24,991)	$ 98,803	$ (79,323)	$ 79,646

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit	Accumulated DeficitCumulative Effect, Period of Adoption, Adjustment
Beginning balance, common stock (in shares) at Dec. 31, 2018			32,941
Beginning balance at Dec. 31, 2018	$ 104,129	$ (75)	$ 33	$ 268,081	$ (78)	$ (163,907)	$ (75)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercises of common stock options (in shares)	24
Exercises of common stock options	$ 69			69
Vesting of restricted stock units (in shares)			2
Vesting of restricted stock units	7			7
Stock-based compensation expense	2,542			2,542
Other comprehensive income (loss)	129				129
Net (loss) income	(12,377)					(12,377)
Ending balance (in shares) at Mar. 31, 2019			32,967
Ending balance at Mar. 31, 2019	$ 94,424		$ 33	270,699	51	(176,359)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Beginning balance, common stock (in shares) at Dec. 31, 2018			32,941
Beginning balance at Dec. 31, 2018	$ 104,129	$ (75)	$ 33	268,081	(78)	(163,907)	$ (75)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	156
Net (loss) income	79,490
Ending balance (in shares) at Sep. 30, 2019			33,224
Ending balance at Sep. 30, 2019	191,409		$ 33	275,790	78	(84,492)
Beginning balance, common stock (in shares) at Mar. 31, 2019			32,967
Beginning balance at Mar. 31, 2019	$ 94,424		$ 33	270,699	51	(176,359)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercises of common stock options (in shares)	9
Exercises of common stock options	$ 29			29
Vesting of restricted stock units (in shares)			2
Vesting of restricted stock units	7			7
Stock-based compensation expense	2,513			2,513
Other comprehensive income (loss)	84				84
Net (loss) income	(6,993)					(6,993)
Ending balance (in shares) at Jun. 30, 2019			32,978
Ending balance at Jun. 30, 2019	$ 90,064		$ 33	273,248	135	(183,352)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercises of common stock options (in shares)	88
Exercises of common stock options	$ 247			247
Vesting of restricted stock units (in shares)			158
Vesting of restricted stock units	6			6
Stock-based compensation expense	2,289			2,289
Other comprehensive income (loss)	(57)				(57)
Net (loss) income	98,860					98,860
Ending balance (in shares) at Sep. 30, 2019			33,224
Ending balance at Sep. 30, 2019	$ 191,409		$ 33	275,790	78	(84,492)
Beginning balance, common stock (in shares) at Dec. 31, 2019	33,738		33,738
Beginning balance at Dec. 31, 2019	$ 174,593		$ 34	281,664	54	(107,159)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)			201
Issuance of common stock from at the market offering, net of issuance costs	$ 1,648			1,648
Exercises of common stock options (in shares)	9
Exercises of common stock options	$ 38			38
Vesting of restricted stock units (in shares)			101
Stock-based compensation expense	2,618			2,618
Other comprehensive income (loss)	90				90
Net (loss) income	(26,443)					(26,443)
Ending balance (in shares) at Mar. 31, 2020			34,049
Ending balance at Mar. 31, 2020	$ 152,544		$ 34	285,968	144	(133,602)
Beginning balance, common stock (in shares) at Dec. 31, 2019	33,738		33,738
Beginning balance at Dec. 31, 2019	$ 174,593		$ 34	281,664	54	(107,159)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercises of common stock options (in shares)	100
Other comprehensive income (loss)	$ (9)
Net (loss) income	$ (79,314)
Ending balance (in shares) at Sep. 30, 2020	34,287		34,287
Ending balance at Sep. 30, 2020	$ 105,087		$ 34	291,481	45	(186,473)
Beginning balance, common stock (in shares) at Mar. 31, 2020			34,049
Beginning balance at Mar. 31, 2020	$ 152,544		$ 34	285,968	144	(133,602)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercises of common stock options (in shares)	16
Exercises of common stock options	$ 61			61
Stock-based compensation expense	2,643			2,643
Other comprehensive income (loss)	(11)				(11)
Net (loss) income	(27,968)					(27,968)
Ending balance (in shares) at Jun. 30, 2020			34,065
Ending balance at Jun. 30, 2020	$ 127,269		$ 34	288,672	133	(161,570)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercises of common stock options (in shares)	75
Exercises of common stock options	$ 348			348
Vesting of restricted stock units (in shares)			147
Stock-based compensation expense	2,461			2,461
Other comprehensive income (loss)	(88)				(88)
Net (loss) income	$ (24,903)					(24,903)
Ending balance (in shares) at Sep. 30, 2020	34,287		34,287
Ending balance at Sep. 30, 2020	$ 105,087		$ 34	$ 291,481	$ 45	$ (186,473)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net (loss) income	$ (79,314)	$ 79,490
Adjustments to reconcile net (loss) income to net cash used in operating activities:
Stock-based compensation expense	7,722	7,344
Depreciation expense	2,601	2,906
Net amortization of premiums and discounts on investments	(68)	(1,247)
Other non-cash items	(1)	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,641	(1,774)
Other non-current assets	(1,378)	(582)
Accounts payable	411	167
Accrued expenses and other current liabilities	1,358	30
Deferred revenue—related party	0	(97,872)
Other liabilities	(100)	8
Net cash used in operating activities	(67,128)	(11,530)
Investing activities:
Purchases of investments	(37,203)	(147,995)
Proceeds from maturities of investments	116,287	178,661
Purchases of property and equipment	(55)	(985)
Net cash provided by investing activities	79,029	29,681
Financing activities:
Proceeds from at the market offering, net of issuance costs	1,514	0
Proceeds from exercise of stock options	447	345
Net cash provided by financing activities	1,961	345
Net increase in cash, cash equivalents and restricted cash	13,862	18,496
Cash, cash equivalents and restricted cash, beginning of period	54,511	49,176
Cash, cash equivalents and restricted cash, end of period	68,373	67,672
Supplemental cash flow information:
Cash paid for lease liabilities	2,924	3,200
Cash paid for income taxes	$ 45	$ 101

Nature of Business

Nature of Business	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Jounce Therapeutics, Inc. (the “Company”) is a clinical-stage immunotherapy company dedicated to transforming the treatment of cancer by developing therapies that enable the immune system to attack tumors and provide long-lasting benefits to patients. The Company is subject to a number of risks similar to those of other clinical-stage companies, including dependence on key individuals; the need to develop commercially viable products; competition from other companies, many of which are larger and better capitalized; and the need to obtain adequate additional financing to fund the development of its products. As of September 30, 2020, the Company had cash, cash equivalents and investments of $105.3 million. The Company expects that its existing cash, cash equivalents and investments, together with cash proceeds of $120.0 million received from the transaction with Gilead Sciences, Inc. (“Gilead”) that closed in October 2020, will enable the Company to fund its expected operating expenses and capital expenditure requirements for at least 12 months from November 6, 2020, the filing date of this Quarterly Report on Form 10-Q. The Company expects to finance its future cash needs through a combination of equity or debt financings, collaborations, licensing arrangements and strategic alliances.

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements as of September 30, 2020 and December 31, 2019, and for the three and nine months ended September 30, 2020 and 2019, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) of the Financial Accounting Standards Board (“FASB”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all normal recurring adjustments which are necessary for a fair presentation of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on February 27, 2020 (the “Annual Report on Form 10-K”). The information presented in the condensed consolidated financial statements and related notes as of September 30, 2020, and for the three and nine months ended September 30, 2020 and 2019, is unaudited. The December 31, 2019 condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Interim results for the nine months ended September 30, 2020 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2020, or any future period. The accompanying condensed consolidated financial statements include the accounts of Jounce Therapeutics, Inc. and its wholly-owned subsidiary, Jounce Mass Securities, Inc. All intercompany transactions and balances have been eliminated in consolidation. Summary of Significant Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Annual Report on Form 10-K. There have been no material changes in the Company’s significant accounting policies during the nine months ended September 30, 2020. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates which include, but are not limited to, accrued expenses, stock-based compensation expense and income taxes. The Company bases its estimates on historical experience and other market specific or other relevant assumptions it believes to be reasonable under the circumstances. Actual results could differ from those estimates. Recent Accounting Pronouncements In June 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . This standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For available-for-sale debt securities with expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance was originally effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption was permitted. In November 2019, the FASB subsequently issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates , which deferred the effective date of this standard for smaller reporting companies to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years, and early adoption is still permitted. Accordingly, the Company will now adopt this standard effective January 1, 2023, and it is currently evaluating the potential impact that ASU 2016-13 may have on the consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. This guidance became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Accordingly, the Company adopted ASU 2018-13 effective January 1, 2020, and there was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract . This guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected. This guidance became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The amendments in this update are able to be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. Accordingly, the Company adopted ASU 2018-15 effective January 1, 2020, and it elected to apply this guidance on a prospective basis. There was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 , which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”) when the counterparty is a customer. In addition, ASU 2018-18 adds unit-of-account guidance to ASC Topic 808, Collaborative Arrangements , in order to align this guidance with ASC 606 and also precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. This guidance became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Accordingly, the Company adopted ASU 2018-18 effective January 1, 2020, and there was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

License and Collaboration Reven

License and Collaboration Revenue	9 Months Ended
	Sep. 30, 2020
Research and Development [Abstract]
License and Collaboration Revenue	License and Collaboration Revenue Celgene License Agreement On July 22, 2019, the Company entered into a License Agreement (the “Celgene License Agreement”) with Celgene Corporation (“Celgene”). Pursuant to the Celgene License Agreement, the Company granted to Celgene a worldwide and exclusive license to develop, manufacture and commercialize JTX-8064 and certain derivatives thereof (an “Initial Licensed Compound”), as well as any antibody (other than the Initial Licensed Compound) or other biologic controlled by the Company as of July 22, 2019 that is specifically directed to the LILRB2 receptor (the “Licensed Compounds”), and Celgene paid the Company a one-time, non-refundable upfront payment of $50.0 million. As of November 2019, Celgene became a Bristol Myers Squibb company. As part of its Celgene integration process, Bristol Myers Squibb streamlined its pipeline to address areas of overlap. As a result, Celgene provided the Company with a notice of termination and the Celgene License Agreement was terminated effective June 3, 2020 (the “Celgene License Agreement Termination Date”). As of the Celgene License Agreement Termination Date, the Company has sole worldwide rights to JTX-8064, and all of the Company’s intellectual property rights pertaining to JTX-8064 and licensed to Celgene were reacquired by the Company. No party had any further financial or service obligations to one another beyond transition costs and efforts, which were completed during the quarter ended September 30, 2020. Accounting Analysis Identification of the Contract(s) The Company assessed the Celgene License Agreement and concluded that it represents a contract with a customer within the scope of ASC 606. Identification of Promises and Performance Obligations The Company determined that the Celgene License Agreement contained the following promises: (i) delivery of a worldwide and exclusive license to develop, manufacture and commercialize an Initial Licensed Compound and the Licensed Compounds (the “JTX-8064 License”) and (ii) provision of certain transition activities, specifically outlined within the Celgene License Agreement, related to the delivery of the JTX-8064 License (the “Transition Activities”). The Company also evaluated certain other optional activities outlined within the Celgene License Agreement and concluded that none conveyed a material right to Celgene. Accordingly, these options were not considered to be promises within the Celgene License Agreement. The Company assessed the above promises and concluded that the JTX-8064 License was both capable of being distinct and distinct within the context of the Celgene License Agreement. The Company also assessed its promise to perform the Transition Activities and concluded that it was both quantitatively and qualitatively immaterial in the context of the Celgene License Agreement. Accordingly, the Company did not assess the Transition Activities as a performance obligation. Based upon this evaluation, the Company concluded that its promise to deliver the JTX-8064 License represented the sole performance obligation in the Celgene License Agreement. Determination of Transaction Price As noted above, the Company received a non-refundable upfront payment of $50.0 million upon the execution of the Celgene License Agreement. This upfront payment represented an element of fixed consideration under the Celgene License Agreement. The Company also evaluated as possible variable consideration clinical, regulatory and sales milestone payments and royalties that the Company was eligible to receive under the Celgene License Agreement. With respect to clinical and regulatory milestones, based upon the high degree of uncertainty and risk associated with these potential payments, the Company concluded that all such amounts should be fully constrained as it was not probable that a significant reversal in the amount of cumulative revenue recognized would not occur. As for royalties and sales milestones, the Company determined that the royalties and milestones related solely to the JTX-8064 License, which is a license of intellectual property (“IP”). Accordingly, the Company did not include any potential royalty or sales milestone amounts in the initial transaction price, and the Company determined it would not recognize revenue related to these royalties and sales milestones until the associated sales occurred and relevant thresholds were met. Based upon the above considerations, the Company concluded that the initial transaction price associated with the Celgene License Agreement consisted solely of the upfront payment of $50.0 million. Allocation of Transaction Price to Performance Obligations As the Company’s promise to deliver the JTX-8064 License represented the sole performance obligation in the Celgene License Agreement, the entirety of the $50.0 million transaction price was allocated to this performance obligation. Recognition of Revenue The Company determined that the JTX-8064 License was a functional license as the underlying IP had significant standalone functionality. In addition, the Company determined that the JTX-8064 License represented a right to use certain of the Company’s IP as it existed at a point in time. Finally, the Company determined that July 22, 2019 represented (i) the date at which the Company made available the IP to Celgene and (ii) the beginning of the period during which Celgene was able to use and benefit from its right to use the IP. Based upon these considerations, the Company recognized $50.0 million of license revenue during the three months ended September 30, 2019. As the upfront payment was non-refundable, the subsequent termination of the Celgene License Agreement had no impact on this revenue recognition. Up through the Celgene License Agreement Termination Date, the Company did not receive any milestone or royalty payments. Celgene Collaboration Agreement In July 2016, the Company entered into a Master Research and Collaboration Agreement (the “Celgene Collaboration Agreement”) with Celgene. The primary goal of the collaboration was to co-develop and co-commercialize innovative biologic immunotherapies that either activate or suppress the immune system by binding to targets identified by leveraging the Company’s Translational Science Platform. Under the Celgene Collaboration Agreement, the Company granted Celgene exclusive options to develop and commercialize the Company’s lead product candidate, vopratelimab, and up to four early-stage programs, consisting of targets to be selected from a pool of certain B cell, T regulatory cell and tumor-associated macrophage targets. Additionally, the Company granted Celgene an exclusive option to develop and commercialize the Company’s product candidate JTX-4014, an anti-PD-1 antibody, which, upon exercise of such option, would have been a shared program to be used by both parties in and outside of the collaboration. The Company and Celgene terminated the Celgene Collaboration Agreement effective July 22, 2019. The Company received a non-refundable upfront cash payment of $225.0 million in July 2016 upon the execution of the Celgene Collaboration Agreement. The Company also received $36.1 million from the sale of 10,448,100 shares of Series B-1 convertible preferred stock upon the execution of a Series B-1 Preferred Stock Purchase Agreement with Celgene, which shares converted into 2,831,463 shares of common stock upon the completion of the Company’s initial public offering (“IPO”). If Celgene had elected to exercise any of the program options, Celgene would have been required to pay the Company an option-exercise fee that varied by program. The initial research term of the collaboration was four years, which could have been extended, at Celgene’s option, annually for up to three Worldwide Development Cost and U.S. Operating Profit and Loss Sharing Prior to Celgene exercising any of its options, the Company was responsible for all research and development activities under the Celgene Collaboration Agreement. Upon the exercise of each program option, the parties would have entered into a co-development and co-commercialization agreement (the “Co-Co Agreements”) or, in the case of JTX-4014, a license agreement (the “JTX-4014 License Agreement”) to govern the development and commercialization of the applicable program. As part of the Celgene Collaboration Agreement, the parties agreed to the terms of the Co-Co Agreements and the JTX-4014 License Agreement that would have been executed upon Celgene’s exercise of any option. Milestones and Royalties Under the Co-Co Agreements and the JTX-4014 License Agreement, Celgene would have been required to pay the Company for specified development, regulatory and commercial milestones, if achieved, across all collaboration programs. Development milestones were payable on the initiation of certain clinical trials, regulatory approval milestones were payable upon regulatory approval in the United States and outside the United States and commercial milestones were payable upon achievement of specified aggregate product sales outside the United States for each program. The Company was also eligible to receive royalties on product sales outside the United States. Accounting Analysis Identification of the Contract(s) The Company assessed the Celgene Collaboration Agreement and concluded that it represented a contract with a customer within the scope of ASC 606. The Company also concluded that each of the Co-Co Agreements and the JTX-4014 License Agreement, if any had been executed, would have represented separate contracts apart from the Celgene Collaboration Agreement. Identification of Promises and Performance Obligations The Company determined that the Celgene Collaboration Agreement contained the following promises: (i) research and development services for vopratelimab (“Vopratelimab Research Services”), (ii) research and development services for JTX-4014 (“JTX-4014 Research Services”), (iii) research and development services associated with the Lead Program and Other Programs (“Lead and Other Programs Research Services”), (iv) research services associated with target screening (“Target Screening Services”), (v) non-transferable, limited sub-licensable and non-exclusive licenses to use the Company’s intellectual property and the Company’s rights in the collaboration intellectual property to conduct certain activities, on a program-by-program basis (the “Research Licenses”), (vi) various record-keeping and reporting requirements on a program-by-program basis, (vii) exclusivity provisions with respect to each Collaboration Exclusive Target and biologics binding to such Collaboration Exclusive Targets and (viii) establishment of and participation in a joint steering committee (the “JSC”) and a joint patent committee (the “JPC”). The Company also evaluated the six program options as well as the research term extension options and concluded that none conveyed a material right to Celgene. Accordingly, neither the program options nor the research term extension options were considered to be promises within the Celgene Collaboration Agreement. The Company assessed the above promises and concluded that each of the Vopratelimab Research Services, JTX-4014 Research Services, Lead and Other Programs Research Services and Target Screening Services were both capable of being distinct and distinct within the context of the Celgene Collaboration Agreement. Therefore, the Company concluded that each of the Vopratelimab Research Services, JTX-4014 Research Services, Lead and Other Programs Research Services and Target Screening Services represented separate performance obligations. The Company determined that the Research Licenses were not distinct within the context of the Celgene Collaboration Agreement as the Research Licenses allowed Celgene to evaluate the results of the research and development services performed by the Company and the right to perform its duties under the Celgene Collaboration Agreement, but did not provide Celgene with any commercialization rights. Celgene could only benefit from the Research Licenses in conjunction with the related research and development services. Accordingly, the Research Licenses related to vopratelimab, JTX-4014 and the Lead and Other Programs were combined with their respective research and development services performance obligations. Similarly, the Company also determined that the various record-keeping and reporting requirements related to each program and the exclusivity provisions with respect to each Collaboration Exclusive Target and biologics binding to such Collaboration Exclusive Targets were not distinct within the context of the Celgene Collaboration Agreement. Accordingly, the various record-keeping and reporting requirements on a program-by-program basis and the exclusivity provisions with respect to each Collaboration Exclusive Target and biologics binding to such Collaboration Exclusive Targets were combined with their respective research and development services performance obligations. Finally, the Company assessed its participation in the JSC and the JPC and concluded that it was both quantitatively and qualitatively immaterial in the context of the Celgene Collaboration Agreement. Accordingly, the Company did not assess its participation in the JSC and the JPC as a performance obligation. Determination of Transaction Price As noted above, the Company received a non-refundable upfront payment of $225.0 million upon the execution of the Celgene Collaboration Agreement. This upfront payment represented an element of fixed consideration under the Celgene Collaboration Agreement. Celgene also purchased 10,448,100 shares of Series B-1 convertible preferred stock (“Series B-1 Preferred Stock”) for gross proceeds of $36.1 million, which shares converted into 2,831,463 shares of common stock upon the completion of the IPO. The Company determined the shares of Series B-1 Preferred Stock were sold at fair value. Therefore, the proceeds from the issuance of Series B-1 Preferred Stock did not impact the transaction price to be allocated to the performance obligations. The Company evaluated as possible variable consideration the milestones, royalties, development cost sharing and profit-sharing provisions discussed above. The Company concluded that none of these items represented variable consideration under the Celgene Collaboration Agreement as all such amounts were dependent upon the execution of a related Co-Co Agreement or the JTX-4014 License Agreement. The Co-Co Agreements and the JTX-4014 License Agreement, if any had been executed, would have represented separate contracts apart from the Celgene Collaboration Agreement. The Company also considered the existence of any significant financing component within the Celgene Collaboration Agreement given its upfront payment structure. Based upon this assessment, the Company concluded that any difference between the promised consideration and the cash selling price of the services under the Celgene Collaboration Agreement arose for reasons other than the provision of financing, and the difference between those amounts was proportional to the reason for the difference. Accordingly, the Company concluded that the upfront payment structure of the Celgene Collaboration Agreement did not result in the existence of a significant financing component. Based upon the above considerations, the Company concluded that the transaction price associated with the Celgene Collaboration Agreement consisted solely of the upfront payment of $225.0 million. Allocation of Transaction Price to Performance Obligations The Company allocated the transaction price to each performance obligation on a relative standalone selling price basis. For all performance obligations, the Company determined the standalone selling price using estimates of the costs to perform the research and development services, including expected internal and external costs for services and supplies, adjusted to reflect a reasonable profit margin. The total estimated cost of the research and development services reflected the nature of the services to be performed and the Company’s best estimate of the length of time required to perform the services. Recognition of Revenue Prior to the termination of the Celgene Collaboration Agreement, the Company was recognizing revenue over time as the services related to each performance obligation were rendered. The Company concluded that an input method under ASC 606 was a representative depiction of the transfer of services under the Celgene Collaboration Agreement. The method of measuring progress towards delivery of the services incorporated actual internal and external costs incurred, relative to total internal and external costs expected to be incurred to satisfy the performance obligations. The period over which total costs were estimated reflected the Company’s estimate of the period over which it would perform the research and development services to deliver a pre-defined data package to Celgene for each program subject to an option. The Company was recognizing revenue for each performance obligation over periods ranging from twelve months to four years. Changes in estimates of total internal and external costs expected to be incurred were recognized in the period of change as a cumulative catch-up adjustment.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value is determined based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect certain market assumptions. As a basis for considering such assumptions, GAAP establishes a three-tier value hierarchy, which prioritizes the inputs used to develop the assumptions and for measuring fair value as follows: (Level 1) observable inputs such as quoted prices in active markets for identical assets; (Level 2) inputs other than the quoted prices in active markets that are observable either directly or indirectly; and (Level 3) unobservable inputs in which there is little or no market data, which requires the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The Company measures the fair value of money market funds, U.S. Treasuries and government agency securities based on quoted prices in active markets for identical securities. Investments also include corporate debt securities which are valued either based on recent trades of securities in inactive markets or based on quoted market prices of similar instruments and other significant inputs derived from or corroborated by observable market data. The carrying amounts reflected in the condensed consolidated balance sheets for cash, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature. Assets measured at fair value on a recurring basis as of September 30, 2020 were as follows (in thousands): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Money market funds, included in cash equivalents $ 63,922 $ 63,922 $ — $ — Investments: Corporate debt securities 28,832 — 28,832 — U.S. Treasuries 8,506 8,506 — — Government agency securities 4,021 — 4,021 — Totals $ 105,281 $ 72,428 $ 32,853 $ — Assets measured at fair value on a recurring basis as of December 31, 2019 were as follows (in thousands): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Money market funds, included in cash equivalents $ 50,242 $ 50,242 $ — $ — Investments: Corporate debt securities 48,300 — 48,300 — U.S. Treasuries 59,082 59,082 — — Government agency securities 12,820 — 12,820 — Totals $ 170,444 $ 109,324 $ 61,120 $ — There were no changes in valuation techniques during the nine months ended September 30, 2020 or during the year ended December 31, 2019. There were no liabilities measured at fair value on a recurring basis as of September 30, 2020 or December 31, 2019.

Investments

Investments	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Short-term investments consist of investments with maturities greater than ninety days and less than one year from the balance sheet date. Long-term investments consist of investments with maturities of greater than one year that are not expected to be used to fund current operations. The Company classifies all of its investments as available-for-sale securities. Accordingly, these investments are recorded at fair value. Realized gains and losses, amortization and accretion of discounts and premiums are included in other income, net. Unrealized gains and losses on available-for-sale securities are included in other comprehensive income as a component of stockholders’ equity until realized. Cash equivalents, short-term investments and long-term investments as of September 30, 2020 were comprised as follows (in thousands): September 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 63,922 $ — $ — $ 63,922 Corporate debt securities 27,774 25 (1) 27,798 U.S. Treasuries 8,500 6 — 8,506 Government agency securities 4,006 15 — 4,021 Total cash equivalents and short-term investments 104,202 46 (1) 104,247 Long-term investments: Corporate debt securities 1,034 — — 1,034 Total long-term investments $ 1,034 $ — $ — $ 1,034 Total cash equivalents and investments $ 105,236 $ 46 $ (1) $ 105,281 Cash equivalents, short-term investments and long-term investments as of December 31, 2019 were comprised as follows (in thousands): December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 50,242 $ — $ — $ 50,242 Corporate debt securities 46,695 8 (4) 46,699 U.S. Treasuries 59,058 26 (2) 59,082 Government agency securities 12,796 24 — 12,820 Total cash equivalents and short-term investments 168,791 58 (6) 168,843 Long-term investments: Corporate debt securities 1,599 2 — 1,601 Total long-term investments 1,599 2 — 1,601 Total cash equivalents and investments $ 170,390 $ 60 $ (6) $ 170,444 As of September 30, 2020 and December 31, 2019, the aggregate fair value of securities that were in an unrealized loss position for less than twelve months was $1.4 million and $28.3 million, respectively. There were no securities that were in an unrealized loss position for more than twelve months as of either September 30, 2020 or December 31, 2019. As of September 30, 2020, the Company did not intend to sell, and would not be more likely than not required to sell, the securities in an unrealized loss position before recovery of their amortized cost bases. Furthermore, the Company determined that there was no material change in the credit risk of these securities. As a result, the Company determined it did not hold any securities with any other-than-temporary impairment as of September 30, 2020. There were immaterial realized gains on available-for-sale securities during the three and nine months ended September 30, 2020. There were no realized gains or losses on available-for-sale securities during the three or nine months ended September 30, 2019.

Restricted Cash

Restricted Cash	9 Months Ended
	Sep. 30, 2020
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted Cash As of both September 30, 2020 and December 31, 2019, the Company maintained non-current restricted cash of $1.3 million. This amount is included within “Other non-current assets” in the accompanying condensed consolidated balance sheets and is comprised solely of a letter of credit required pursuant to the lease for the Company’s corporate headquarters. The following table provides a reconciliation of cash, cash equivalents and restricted cash that sums to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): Nine Months Ended Nine Months Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 53,241 $ 67,103 $ 47,906 $ 66,402 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 54,511 $ 68,373 $ 49,176 $ 67,672

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2020
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses as of September 30, 2020 and December 31, 2019 were comprised as follows (in thousands): September 30, December 31, 2020 2019 External research and development and professional services $ 4,753 $ 3,639 Employee compensation and benefits 5,339 5,147 Lab consumables and other 231 121 Total accrued expenses $ 10,323 $ 8,907

Common Stock and Preferred Stoc

Common Stock and Preferred Stock	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Common Stock and Preferred Stock	Common Stock and Preferred Stock Common Stock The Company is authorized to issue 160,000,000 shares of common stock. Holders of common stock are entitled to one vote per share. Holders of common stock are entitled to receive dividends, if and when declared by the board of directors. On December 17, 2019, the Company entered into a Sales Agreement with Cowen and Company, LLC (“Cowen”) pursuant to which the Company may offer and sell shares of its common stock with an aggregate offering price of up to $50.0 million under an “at the market” offering program (the “ATM Offering”). The Sales Agreement provides that Cowen will be entitled to a sales commission equal to 3.0% of the gross sales price per share of all shares sold under the ATM Offering. From the initiation of the ATM Offering through September 30, 2020, the Company has sold an aggregate of 648,845 shares at an average price of $8.54 per share for net proceeds of $5.2 million after deducting sales commissions and offering expenses, $0.8 million of which was earned in 2020. Preferred Stock The Company is authorized to issue 5,000,000 shares of undesignated preferred stock in one or more series. As of September 30, 2020, no shares of preferred stock were issued or outstanding. Shares Reserved for Future Issuance As of September 30, 2020 and December 31, 2019, the Company had reserved for future issuance the following number of shares of common stock (in thousands): September 30, December 31, 2020 2019 Shares reserved for vesting of restricted stock units 601 460 Shares reserved for exercises of outstanding stock options 6,686 5,735 Shares reserved for future issuance under the 2017 Stock Option and Incentive Plan 1,198 1,288 Total shares reserved for future issuance 8,485 7,483

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock-based Compensation	Stock-based Compensation 2013 Stock Option and Grant Plan In February 2013, the board of directors adopted and the Company’s stockholders approved the 2013 Stock Option and Grant Plan (the “2013 Plan”), as amended and restated, under which it could grant incentive stock options (“ISOs”), non-qualified stock options, restricted stock awards (“RSAs”) and restricted stock units (“RSUs”) to eligible employees, officers, directors, and consultants. The 2013 Plan was subsequently amended in January 2015, April 2015, July 2015, March 2016 and October 2016 to allow for the issuance of additional shares of common stock. 2017 Stock Option and Incentive Plan In January 2017, the board of directors adopted and the Company’s stockholders approved the 2017 Stock Option and Incentive Plan (the “2017 Plan”). Upon the adoption of the 2017 Plan, no further awards will be granted under the 2013 Plan. The 2017 Plan provides for the grant of ISOs, non-qualified stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors and consultants and advisors are eligible to receive awards under the 2017 Plan. The terms of awards, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2017 Plan. The Company initially registered on Form S-8 1,753,758 shares of common stock under the 2017 Plan, which was comprised of (i) 1,510,000 shares of common stock reserved for issuance under the 2017 Plan, plus (ii) 243,758 shares of common stock originally reserved for issuance under the 2013 Plan that became available for issuance under the 2017 Plan upon the completion of the Company’s IPO. The 2017 Plan also provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2017 Plan on January 1, 2018 and each January 1 st thereafter. The number of shares added each year will be equal to the lesser of (i) 4% of the outstanding shares on the immediately preceding December 31 st or (ii) such amount as determined by the compensation committee of the board of directors. Effective January 1, 2018, 2019 and 2020, 1,290,609, 1,317,935 and 1,349,526 additional shares, respectively, were automatically added to the shares authorized for issuance under the 2017 Plan. As of September 30, 2020, there were 1,198,253 shares available for future issuance under the 2017 Plan. 2017 Employee Stock Purchase Plan In January 2017, the board of directors adopted and the Company’s stockholders approved the 2017 Employee Stock Purchase Plan (the “2017 ESPP”). The Company initially reserved 302,000 shares of common stock for future issuance under the 2017 ESPP. The 2017 ESPP also provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2017 ESPP on January 1, 2018 and each January 1 st thereafter through January 1, 2027. The number of shares added each year will be equal to the lesser of (i) 1% of the outstanding shares on the immediately preceding December 31 st , (ii) 603,000 shares or (iii) such amount as determined by the compensation committee of the board of directors. Effective January 1, 2018, 2019 and 2020, 322,652, 329,483 and 337,381 additional shares, respectively, were automatically added to the shares authorized for issuance under the 2017 ESPP. No offering periods under the 2017 ESPP had been initiated as of September 30, 2020. Stock-based Compensation Expense Total stock-based compensation expense recognized in the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019 was as follows (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Research and development $ 1,033 $ 1,096 $ 3,410 $ 3,290 General and administrative 1,428 1,193 4,312 4,054 Total stock-based compensation expense $ 2,461 $ 2,289 $ 7,722 $ 7,344 RSU Activity The Company has also granted RSUs to its employees under the 2017 Plan. The following table summarizes RSU activity for the nine months ended September 30, 2020 (in thousands, except per share amounts): RSUs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2019 460 $ 5.61 Issued 420 $ 6.50 Vested (248) $ 6.54 Cancelled (31) $ 6.28 Unvested as of September 30, 2020 601 $ 5.82 The aggregate fair value of RSUs that vested during the three and nine months ended September 30, 2020, based upon the fair values of the stock underlying the RSUs on the day of vesting, was $0.7 million and $1.5 million, respectively. The aggregate fair value of RSUs that vested during each of the three and nine months ended September 30, 2019, based upon the fair values of the stock underlying the RSUs on the day of vesting, was $0.7 million. As of September 30, 2020, there was unrecognized stock-based compensation expense related to unvested RSUs of $2.5 million, which the Company expects to recognize over a weighted-average period of approximately 2.0 years. Stock Option Activity The fair value of stock options granted during the three and nine months ended September 30, 2020 and 2019 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Risk-free interest rate 0.4 % 1.7 % 1.2 % 2.4 % Expected dividend yield — % — % — % — % Expected term (in years) 6.1 6.1 6.0 6.0 Expected volatility 75.3 % 70.3 % 72.2 % 69.3 % Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended September 30, 2020 and 2019 was $4.35 per share and $2.90 per share, respectively. The weighted-average grant date fair value of stock options granted during the nine months ended September 30, 2020 and 2019 was $4.23 per share and $2.88 per share, respectively. The following table summarizes stock option activity during the nine months ended September 30, 2020 (in thousands, except per share amounts): Options Weighted-Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at December 31, 2019 5,735 $ 8.76 7.2 $ 18,959 Granted 1,206 $ 6.65 Exercised (100) $ 4.50 Cancelled (155) $ 11.36 Outstanding at September 30, 2020 6,686 $ 8.39 6.9 $ 18,122 Exercisable at September 30, 2020 4,381 $ 8.09 5.9 $ 13,627 The aggregate intrinsic value of stock options exercised during the three months ended September 30, 2020 and 2019 was $0.4 million and $0.1 million, respectively. The aggregate intrinsic value of stock options exercised during the nine months ended September 30, 2020 and 2019 was $0.4 million and $0.2 million, respectively. As of September 30, 2020, there was unrecognized stock-based compensation expense related to unvested stock options of $11.3 million, which the Company expects to recognize over a weighted-average period of approximately 2.3 years.

Related-party Transactions

Related-party Transactions	9 Months Ended
	Sep. 30, 2020
Related Party Transactions [Abstract]
Related-party Transactions	Related-party TransactionsIn July 2019, the Company entered into the Celgene License Agreement under which it received a non-refundable upfront payment of $50.0 million from Celgene. In July 2016, the Company entered into the Celgene Collaboration Agreement and a Series B-1 Preferred Stock Purchase Agreement with Celgene. Under the Celgene Collaboration Agreement, the Company received a non-refundable upfront payment of $225.0 million. Under the Series B-1 Preferred Stock Purchase Agreement, Celgene purchased 10,448,100 shares of Series B-1 convertible preferred stock for $36.1 million. These shares of Series B-1 convertible preferred stock converted into 2,831,463 shares of common stock upon the completion of the IPO. In addition, an affiliate of Celgene purchased 625,000 shares of the Company’s common stock in the IPO at the public offering price of $16.00 per share for a total of $10.0 million. As of September 30, 2020 there were no reimbursable expenses due from Celgene. As of and December 31, 2019 the Company had recorded $0.7 million of reimbursable expenses due from Celgene within prepaid expenses and other current assets in the accompanying condensed consolidated balance sheets.See Note 3, “License and Collaboration Revenue”, for further information about the Company’s agreements with Celgene

Net (Loss) Income per Share

Net (Loss) Income per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Net (Loss) Income per Share	Net (Loss) Income per ShareBasic net (loss) income per share is calculated based upon the weighted-average number of common shares outstanding during the period, excluding outstanding stock options, RSAs and RSUs that have been issued but are not yet vested. Diluted net (loss) income per share is calculated based upon the weighted-average number of common shares outstanding during the period plus the dilutive impact of weighted-average common equivalent shares outstanding during the period. The potentially dilutive shares of common stock resulting from the assumed exercise of outstanding stock options and the assumed vesting of RSAs and RSUs were determined under the treasury stock method. The following table summarizes the calculation of basic and diluted net (loss) income per share (in thousands, except per share amounts): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Net (loss) income $ (24,903) $ 98,860 $ (79,314) $ 79,490 Weighted-average common shares outstanding, basic 34,159 33,112 34,081 33,015 Dilutive effect of outstanding stock options — 991 — 1,093 Dilutive effect of unvested RSAs — — — 1 Dilutive effect of unvested RSUs — 38 — 51 Weighted-average common shares outstanding, diluted 34,159 34,141 34,081 34,160 Net (loss) income per share, basic $ (0.73) $ 2.99 $ (2.33) $ 2.41 Net (loss) income per share, diluted $ (0.73) $ 2.90 $ (2.33) $ 2.33 The following weighted-average amounts were excluded from the valuation of diluted net (loss) income per share because their effect would be anti-dilutive (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Outstanding stock options 6,735 4,350 6,581 3,772 Unvested RSAs — 2 — — Unvested RSUs 674 11 684 314 Total 7,409 4,363 7,265 4,086

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company and Gilead entered into an exclusive license agreement (the “License Agreement”) to license the Company's JTX-1811 program to Gilead in August 2020. Concurrently with executing the License Agreement, the Company and Gilead entered into a stock purchase agreement (the “Stock Purchase Agreement”) and a registration rights agreement (the “Registration Rights Agreement”, and together with the License Agreement and the Stock Purchase Agreement, the “Transaction Agreements”). The transactions with Gilead were subject to review under the Hart-Scott Rodino Antitrust Improvements Act of 1976 and other customary closing conditions, and the closing date of the Transaction Agreements was October 16, 2020. In October 2020, the Company received an upfront cash license payment of $85.0 million upon the closing of the Transaction Agreements and Gilead purchased 5,539,727 shares of the Company’s common stock for $35.0 million. After the issuance of common shares to Gilead, the Company had 39,838,781 of common shares outstanding. In addition to the $85.0 million upfront cash payment from Gilead, the Company will also be eligible to receive up to $685.0 million in aggregate potential development, regulatory and commercial milestone payments as well as royalties based on a percentage of worldwide sales ranging from the high single digits to mid-teens, subject to adjustments in certain circumstances. The Company will be responsible for all expenses related to development activities until (i) the clearance of an investigational new drug application for JTX-1811 by the Food and Drug Administration, or (ii) an earlier date specified by Gilead. After such time, Gilead will have the sole right and responsibility and bear all expenses to develop and commercialize JTX-1811.

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements as of September 30, 2020 and December 31, 2019, and for the three and nine months ended September 30, 2020 and 2019, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) of the Financial Accounting Standards Board (“FASB”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all normal recurring adjustments which are necessary for a fair presentation of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on February 27, 2020 (the “Annual Report on Form 10-K”). The information presented in the condensed consolidated financial statements and related notes as of September 30, 2020, and for the three and nine months ended September 30, 2020 and 2019, is unaudited. The December 31, 2019 condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Summary of Significant Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Annual Report on Form 10-K. There have been no material changes in the Company’s significant accounting policies during the nine months ended September 30, 2020.
Principles of Consolidation	The accompanying condensed consolidated financial statements include the accounts of Jounce Therapeutics, Inc. and its wholly-owned subsidiary, Jounce Mass Securities, Inc. All intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates which include, but are not limited to, accrued expenses, stock-based compensation expense and income taxes. The Company bases its estimates on historical experience and other market specific or other relevant assumptions it believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . This standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For available-for-sale debt securities with expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance was originally effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption was permitted. In November 2019, the FASB subsequently issued ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates , which deferred the effective date of this standard for smaller reporting companies to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years, and early adoption is still permitted. Accordingly, the Company will now adopt this standard effective January 1, 2023, and it is currently evaluating the potential impact that ASU 2016-13 may have on the consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds and modifies certain disclosure requirements for fair value measurements. This guidance became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Accordingly, the Company adopted ASU 2018-13 effective January 1, 2020, and there was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract . This guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected. This guidance became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The amendments in this update are able to be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. Accordingly, the Company adopted ASU 2018-15 effective January 1, 2020, and it elected to apply this guidance on a prospective basis. There was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 , which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”) when the counterparty is a customer. In addition, ASU 2018-18 adds unit-of-account guidance to ASC Topic 808, Collaborative Arrangements , in order to align this guidance with ASC 606 and also precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. This guidance became effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Accordingly, the Company adopted ASU 2018-18 effective January 1, 2020, and there was no impact to the condensed consolidated financial statements due to the adoption of this guidance. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes
Fair Value Measurement Policy	Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value is determined based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect certain market assumptions. As a basis for considering such assumptions, GAAP establishes a three-tier value hierarchy, which prioritizes the inputs used to develop the assumptions and for measuring fair value as follows: (Level 1) observable inputs such as quoted prices in active markets for identical assets; (Level 2) inputs other than the quoted prices in active markets that are observable either directly or indirectly; and (Level 3) unobservable inputs in which there is little or no market data, which requires the Company to develop its own assumptions. This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The Company measures the fair value of money market funds, U.S. Treasuries and government agency securities based on quoted prices in active markets for identical securities. Investments also include corporate debt securities which are valued either based on recent trades of securities in inactive markets or based on quoted market prices of similar instruments and other significant inputs derived from or corroborated by observable market data. The carrying amounts reflected in the condensed consolidated balance sheets for cash, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value	Assets measured at fair value on a recurring basis as of September 30, 2020 were as follows (in thousands): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Money market funds, included in cash equivalents $ 63,922 $ 63,922 $ — $ — Investments: Corporate debt securities 28,832 — 28,832 — U.S. Treasuries 8,506 8,506 — — Government agency securities 4,021 — 4,021 — Totals $ 105,281 $ 72,428 $ 32,853 $ — Assets measured at fair value on a recurring basis as of December 31, 2019 were as follows (in thousands): Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Money market funds, included in cash equivalents $ 50,242 $ 50,242 $ — $ — Investments: Corporate debt securities 48,300 — 48,300 — U.S. Treasuries 59,082 59,082 — — Government agency securities 12,820 — 12,820 — Totals $ 170,444 $ 109,324 $ 61,120 $ —

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities by Security Type	Cash equivalents, short-term investments and long-term investments as of September 30, 2020 were comprised as follows (in thousands): September 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 63,922 $ — $ — $ 63,922 Corporate debt securities 27,774 25 (1) 27,798 U.S. Treasuries 8,500 6 — 8,506 Government agency securities 4,006 15 — 4,021 Total cash equivalents and short-term investments 104,202 46 (1) 104,247 Long-term investments: Corporate debt securities 1,034 — — 1,034 Total long-term investments $ 1,034 $ — $ — $ 1,034 Total cash equivalents and investments $ 105,236 $ 46 $ (1) $ 105,281 Cash equivalents, short-term investments and long-term investments as of December 31, 2019 were comprised as follows (in thousands): December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents and short-term investments: Money market funds, included in cash equivalents $ 50,242 $ — $ — $ 50,242 Corporate debt securities 46,695 8 (4) 46,699 U.S. Treasuries 59,058 26 (2) 59,082 Government agency securities 12,796 24 — 12,820 Total cash equivalents and short-term investments 168,791 58 (6) 168,843 Long-term investments: Corporate debt securities 1,599 2 — 1,601 Total long-term investments 1,599 2 — 1,601 Total cash equivalents and investments $ 170,390 $ 60 $ (6) $ 170,444

Restricted Cash (Tables)

Restricted Cash (Tables)	9 Months Ended
	Sep. 30, 2020
Cash and Cash Equivalents [Abstract]
Schedule of Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash that sums to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): Nine Months Ended Nine Months Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 53,241 $ 67,103 $ 47,906 $ 66,402 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 54,511 $ 68,373 $ 49,176 $ 67,672
Schedule of Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash that sums to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): Nine Months Ended Nine Months Ended Beginning of Period End of Period Beginning of Period End of Period Cash and cash equivalents $ 53,241 $ 67,103 $ 47,906 $ 66,402 Restricted cash 1,270 1,270 1,270 1,270 Cash, cash equivalents and restricted cash $ 54,511 $ 68,373 $ 49,176 $ 67,672

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2020
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses as of September 30, 2020 and December 31, 2019 were comprised as follows (in thousands): September 30, December 31, 2020 2019 External research and development and professional services $ 4,753 $ 3,639 Employee compensation and benefits 5,339 5,147 Lab consumables and other 231 121 Total accrued expenses $ 10,323 $ 8,907

Common Stock and Preferred St_2

Common Stock and Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Schedule of Stock by Class	As of September 30, 2020 and December 31, 2019, the Company had reserved for future issuance the following number of shares of common stock (in thousands): September 30, December 31, 2020 2019 Shares reserved for vesting of restricted stock units 601 460 Shares reserved for exercises of outstanding stock options 6,686 5,735 Shares reserved for future issuance under the 2017 Stock Option and Incentive Plan 1,198 1,288 Total shares reserved for future issuance 8,485 7,483

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Stock-Based Compensation Expense	Total stock-based compensation expense recognized in the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019 was as follows (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Research and development $ 1,033 $ 1,096 $ 3,410 $ 3,290 General and administrative 1,428 1,193 4,312 4,054 Total stock-based compensation expense $ 2,461 $ 2,289 $ 7,722 $ 7,344
Schedule of Restricted Stock Activity	The Company has also granted RSUs to its employees under the 2017 Plan. The following table summarizes RSU activity for the nine months ended September 30, 2020 (in thousands, except per share amounts): RSUs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2019 460 $ 5.61 Issued 420 $ 6.50 Vested (248) $ 6.54 Cancelled (31) $ 6.28 Unvested as of September 30, 2020 601 $ 5.82
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The fair value of stock options granted during the three and nine months ended September 30, 2020 and 2019 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Risk-free interest rate 0.4 % 1.7 % 1.2 % 2.4 % Expected dividend yield — % — % — % — % Expected term (in years) 6.1 6.1 6.0 6.0 Expected volatility 75.3 % 70.3 % 72.2 % 69.3 %
Schedule of Stock Options, Activity	The following table summarizes stock option activity during the nine months ended September 30, 2020 (in thousands, except per share amounts): Options Weighted-Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at December 31, 2019 5,735 $ 8.76 7.2 $ 18,959 Granted 1,206 $ 6.65 Exercised (100) $ 4.50 Cancelled (155) $ 11.36 Outstanding at September 30, 2020 6,686 $ 8.39 6.9 $ 18,122 Exercisable at September 30, 2020 4,381 $ 8.09 5.9 $ 13,627

Net (Loss) Income per Share (Ta

Net (Loss) Income per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of Dilutive Securities Included In Computation of Net Income (Loss) per Share	The following table summarizes the calculation of basic and diluted net (loss) income per share (in thousands, except per share amounts): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Net (loss) income $ (24,903) $ 98,860 $ (79,314) $ 79,490 Weighted-average common shares outstanding, basic 34,159 33,112 34,081 33,015 Dilutive effect of outstanding stock options — 991 — 1,093 Dilutive effect of unvested RSAs — — — 1 Dilutive effect of unvested RSUs — 38 — 51 Weighted-average common shares outstanding, diluted 34,159 34,141 34,081 34,160 Net (loss) income per share, basic $ (0.73) $ 2.99 $ (2.33) $ 2.41 Net (loss) income per share, diluted $ (0.73) $ 2.90 $ (2.33) $ 2.33
Schedule of Antidilutive Securities Excluded from Computation of Net Loss per Share	The following weighted-average amounts were excluded from the valuation of diluted net (loss) income per share because their effect would be anti-dilutive (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Outstanding stock options 6,735 4,350 6,581 3,772 Unvested RSAs — 2 — — Unvested RSUs 674 11 684 314 Total 7,409 4,363 7,265 4,086

Nature of Business (Details)

Nature of Business (Details) - USD ($) $ in Millions	Nov. 06, 2020	Oct. 31, 2020	Sep. 30, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cash, cash equivalents, and marketable securities			$ 105.3
Gilead Transaction Agreements | Subsequent Event
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from collaborative agreement		$ 120
Scenario, Forecast
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Duration of funding requirement	12 months

License and Collaboration Rev_2

License and Collaboration Revenue - Narrative (Details) $ in Thousands	Jul. 22, 2019USD ($)	Feb. 01, 2017shares	Jul. 31, 2016USD ($)customer_programdeliverableshares	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration revenue				$ 0	$ 119,445	$ 0	$ 147,872
Celgene Corporation | Common Stock | Celgene Collaboration Agreement | IPO
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock converted upon completion of IPO (in shares) | shares		2,831,463
Celgene License Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront payment received	$ 50,000
Collaboration revenue					$ 50,000
Celegene Collaborative Arrangement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront payment received			$ 225,000
Collaboration revenue							$ 97,900
Number of early-stage programs | customer_program			4
Initial research term			4 years
Potential addition to research term			3 years
Number of program options | deliverable			6
Celegene Collaborative Arrangement | Convertible Preferred Stock (Series B-1)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Issuances of convertible preferred stock			$ 36,100
Issuances of convertible preferred stock (in shares) | shares			10,448,100
Celegene Collaborative Arrangement | Celgene Corporation | Celgene Collaboration Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront payment received			$ 225,000
Celegene Collaborative Arrangement | Celgene Corporation | Convertible Preferred Stock (Series B-1) | Celgene Collaboration Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Issuances of convertible preferred stock			$ 36,100
Issuances of convertible preferred stock (in shares) | shares			10,448,100

License and Collaboration Rev_3

License and Collaboration Revenue - Performance Obligations (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01 - Celegene Collaborative Arrangement	Sep. 30, 2020
Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance period for unit of accounting	12 months
Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance period for unit of accounting	4 years

Fair Value Measurements - Asset

Fair Value Measurements - Assets Measured at Fair Value (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Measurements, Recurring
Investments:
Totals	$ 105,281,000	$ 170,444,000
Liabilities measured at fair value	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Totals	72,428,000	109,324,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Totals	32,853,000	61,120,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Totals	0	0
Corporate debt securities | Fair Value, Measurements, Recurring
Investments:
Available-for-sale debt securities, fair value	28,832,000	48,300,000
Corporate debt securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Available-for-sale debt securities, fair value	0	0
Corporate debt securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Available-for-sale debt securities, fair value	28,832,000	48,300,000
Corporate debt securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Available-for-sale debt securities, fair value	0	0
U.S. Treasuries | Fair Value, Measurements, Recurring
Investments:
Available-for-sale debt securities, fair value	8,506,000	59,082,000
U.S. Treasuries | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Available-for-sale debt securities, fair value	8,506,000	59,082,000
U.S. Treasuries | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Available-for-sale debt securities, fair value	0	0
U.S. Treasuries | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Available-for-sale debt securities, fair value	0	0
Government agency securities | Fair Value, Measurements, Recurring
Investments:
Available-for-sale debt securities, fair value	4,021,000	12,820,000
Government agency securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Investments:
Available-for-sale debt securities, fair value	0	0
Government agency securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Investments:
Available-for-sale debt securities, fair value	4,021,000	12,820,000
Government agency securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Investments:
Available-for-sale debt securities, fair value	0	0
Money market funds, included in cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	63,922,000	50,242,000
Money market funds, included in cash equivalents | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	63,922,000	50,242,000
Money market funds, included in cash equivalents | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	63,922,000	50,242,000
Money market funds, included in cash equivalents | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	0	0
Money market funds, included in cash equivalents | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds, included in cash equivalents	$ 0	$ 0

Investments - Available-for-sal

Investments - Available-for-sale Securities by Security Type (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	$ 46	$ 60
Unrealized Losses	(1)	(6)
Cash equivalents, short-term and long-term investments, carrying value	105,236	170,390
Cash equivalents, short-term and long-term investments, fair vale disclosure	105,281	170,444
Short-term Investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	46	58
Unrealized Losses	(1)	(6)
Total cash equivalents and short-term investments, carrying value	104,202	168,791
Total cash equivalents and short-term investments, fair value	104,247	168,843
Short-term Investments | Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	27,774	46,695
Unrealized Gains	25	8
Unrealized Losses	(1)	(4)
Available-for-sale debt securities, fair value	27,798	46,699
Short-term Investments | U.S. Treasuries
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	8,500	59,058
Unrealized Gains	6	26
Unrealized Losses	0	(2)
Available-for-sale debt securities, fair value	8,506	59,082
Short-term Investments | Government agency securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	4,006	12,796
Unrealized Gains	15	24
Unrealized Losses	0	0
Available-for-sale debt securities, fair value	4,021	12,820
Long-term Investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	1,034	1,599
Unrealized Gains	0	2
Unrealized Losses	0	0
Available-for-sale debt securities, fair value	1,034	1,601
Long-term Investments | Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Available-for-sale debt securities, amortized cost basis	1,034	1,599
Unrealized Gains	0	2
Unrealized Losses	0	0
Available-for-sale debt securities, fair value	1,034	1,601
Money market funds, included in cash equivalents
Debt Securities, Available-for-sale [Line Items]
Cash equivalents at carrying value	63,922	50,242
Cash equivalents at fair value	63,922	50,242
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Unrealized Gains	0	0
Unrealized Losses	$ 0	$ 0

Investments - Narrative (Detail

Investments - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities in an unrealized loss position for less than twelve months	$ 1,400,000		$ 1,400,000		$ 28,300,000
Aggregate fair value of securities in an unrealized position for more than twelve months	0		0		$ 0
Realized gains or losses on available-for-sale securities	$ 0	$ 0	$ 0	$ 0

Restricted Cash - Narrative (De

Restricted Cash - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Non-current restricted cash	$ 1.3	$ 1.3

Restricted Cash - Schedule of C

Restricted Cash - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 67,103	$ 53,241	$ 66,402	$ 47,906
Restricted cash	1,270	1,270	1,270	1,270
Cash, cash equivalents and restricted cash	$ 68,373	$ 54,511	$ 67,672	$ 49,176

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
External research and development and professional services	$ 4,753	$ 3,639
Employee compensation and benefits	5,339	5,147
Lab consumables and other	231	121
Total accrued expenses	$ 10,323	$ 8,907

Common Stock and Preferred St_3

Common Stock and Preferred Stock - Narrative (Details) $ / shares in Units, $ in Millions	Dec. 17, 2019USD ($)	Sep. 30, 2020USD ($)vote$ / sharesshares	Sep. 30, 2020USD ($)vote$ / sharesshares	Dec. 31, 2019shares
Subsidiary, Sale of Stock [Line Items]
Common stock shares authorized (in shares)		160,000,000	160,000,000	160,000,000
Common stock, votes per share | vote		1	1
Preferred stock shares authorized (in shares)		5,000,000	5,000,000	5,000,000
Preferred stock shares issued (in shares)		0	0	0
Preferred stock shares outstanding (in shares)		0	0	0
ATM Offering
Subsidiary, Sale of Stock [Line Items]
Aggregate offering price shares | $	$ 50
Sales commission percentage	3.00%
Sale of stock, number of shares issued (in shares)		648,845
Sale of stock, price per share (in dollars per share) | $ / shares		$ 8.54	$ 8.54
Proceeds from IPO, net of discounts, commissions, and other offering expenses | $		$ 5.2	$ 0.8

Common Stock and Preferred St_4

Common Stock and Preferred Stock - Shares Reserved for Future Issuance (Details) - shares	Sep. 30, 2020	Dec. 31, 2019	Jan. 31, 2017
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	8,485,000	7,483,000	1,753,758
Shares reserved for vesting of restricted stock units (in shares)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	601,000	460,000
Shares reserved for exercise of outstanding stock options (in shares)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	6,686,000	5,735,000
Shares reserved for future issuance under the 2017 Stock Option and Incentive Plan (in shares)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	1,198,000	1,288,000

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2020	Jan. 01, 2019	Jan. 01, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)				8,485,000		8,485,000		7,483,000	1,753,758
Weighted average fair value of options granted (in dollars per share)				$ 4.35	$ 2.90	$ 4.23	$ 2.88
Intrinsic value of stock options exercised (less than)				$ 0.4	$ 0.1	$ 0.4	$ 0.2
Unrecognized stock-based compensation expense, options				$ 11.3		$ 11.3
Shares reserved for future issuance under the 2017 Stock Option and Incentive Plan (in shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares)				1,198,253		1,198,253
Shares of common stock eligible to be purchased (in shares)				1,198,000		1,198,000		1,288,000
Shares reserved for vesting of restricted stock units (in shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)				601,000		601,000		460,000
Aggregate fair value of awards vested in period				$ 0.7	$ 0.7	$ 1.5	$ 0.7
Unrecognized stock-based compensation expense, RSUs				$ 2.5		$ 2.5
Remaining weighted average vesting period						2 years
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average vesting period						2 years 3 months 18 days
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares)									0
Shares of common stock eligible to be purchased (in shares)									243,758
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)									1,510,000
Percent of outstanding shares able to be added each year									4.00%
Number of additional shares authorized (in shares)	1,349,526	1,317,935	1,290,609
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock eligible to be purchased (in shares)									302,000
Percent of outstanding shares able to be added each year									1.00%
Number of additional shares authorized (in shares)	337,381	329,483	322,652
Shares of common stock to determine number of additional shares (in shares)									603,000

Stock-based Compensation - Stoc

Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,461	$ 2,289	$ 7,722	$ 7,344
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,033	1,096	3,410	3,290
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,428	$ 1,193	$ 4,312	$ 4,054

Stock-based Compensation - RSU

Stock-based Compensation - RSU Activity (Details) - Shares reserved for vesting of restricted stock units (in shares) shares in Thousands	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning unvested balance (in shares) | shares	460
Issued (in shares) | shares	420
Vested (in shares) | shares	(248)
Cancelled (in shares) | shares	(31)
Ending unvested balance (in shares) | shares	601
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning unvested balance (in dollars per share) | $ / shares	$ 5.61
Issued (in dollars per share) | $ / shares	6.50
Vested (in dollars per share) | $ / shares	6.54
Cancelled (in dollars per share) | $ / shares	6.28
Ending unvested balance (in dollars per share) | $ / shares	$ 5.82

Stock-based Compensation - Weig

Stock-based Compensation - Weighted Average Assumptions (Details) - Employee Stock Option	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.40%	1.70%	1.20%	2.40%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years	6 years
Expected volatility	75.30%	70.30%	72.20%	69.30%

Stock-based Compensation - St_2

Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning outstanding balance (in shares)			5,735				5,735
Granted (in shares)							1,206
Exercised (in shares)	(75)	(16)	(9)	(88)	(9)	(24)	(100)
Cancelled (in shares)							(155)
Ending outstanding balance (in shares)	6,686						6,686	5,735
Exercisable (in shares)	4,381						4,381
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning outstanding balance (in dollars per share)			$ 8.76				$ 8.76
Granted (in dollars per share)							6.65
Exercised (in dollars per share)							4.50
Cancelled or forfeited (in dollars per share)							11.36
Ending outstanding balance (in dollars per share)	$ 8.39						8.39	$ 8.76
Exercisable (in dollars per share)	$ 8.09						$ 8.09
Remaining contractual life, outstanding							6 years 10 months 24 days	7 years 2 months 12 days
Remaining contractual life, exercisable							5 years 10 months 24 days
Aggregate intrinsic value, outstanding	$ 18,122						$ 18,122	$ 18,959
Aggregate intrinsic value, exercisable	$ 13,627						$ 13,627

Related-party Transactions (Det

Related-party Transactions (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 22, 2019	Feb. 01, 2017	Jul. 31, 2019	Jul. 31, 2016	Sep. 30, 2020	Dec. 31, 2019
Celgene License Agreement
Related Party Transaction [Line Items]
Non-refundable upfront payment received	$ 50
Celegene Collaborative Arrangement
Related Party Transaction [Line Items]
Non-refundable upfront payment received				$ 225
Celegene Collaborative Arrangement | Convertible Preferred Stock (Series B-1)
Related Party Transaction [Line Items]
Issuances of convertible preferred stock (in shares)				10,448,100
Issuances of convertible preferred stock				$ 36.1
Celgene License Agreement | Celgene License Agreement | Celgene Corporation
Related Party Transaction [Line Items]
Non-refundable upfront payment received			$ 50
Reimbursable expenses due from Celgene					$ 0	$ 0.7
Celgene Collaboration Agreement | Celgene Corporation | Common Stock | IPO
Related Party Transaction [Line Items]
Stock converted upon completion of IPO (in shares)		2,831,463
Celgene Collaboration Agreement | Celgene Corporation | Common Stock | IPO | Affiliated Entity
Related Party Transaction [Line Items]
Sale of stock, number of shares issued (in shares)		625,000
Sale of stock, price per share (in dollars per share)		$ 16
Proceeds from IPO, net of discounts, commissions, and other offering expenses		$ 10
Celgene Collaboration Agreement | Celegene Collaborative Arrangement | Celgene Corporation
Related Party Transaction [Line Items]
Non-refundable upfront payment received				$ 225
Celgene Collaboration Agreement | Celegene Collaborative Arrangement | Celgene Corporation | Convertible Preferred Stock (Series B-1)
Related Party Transaction [Line Items]
Issuances of convertible preferred stock (in shares)				10,448,100
Issuances of convertible preferred stock				$ 36.1

Net (Loss) Income per Share Sch

Net (Loss) Income per Share Schedule of Dilutive Securities Included In Computation of Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net (loss) income	$ (24,903)	$ (27,968)	$ (26,443)	$ 98,860	$ (6,993)	$ (12,377)	$ (79,314)	$ 79,490
Weighted-average common shares outstanding, basic (in shares)	34,159			33,112			34,081	33,015
Weighted-average common shares outstanding, diluted (in shares)	34,159			34,141			34,081	34,160
Net income (loss) per share, basic (in dollars per share)	$ (0.73)			$ 2.99			$ (2.33)	$ 2.41
Net income (loss) per share, diluted (in dollars per share)	$ (0.73)			$ 2.90			$ (2.33)	$ 2.33
Outstanding stock options
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Dilutive securities included in computation of net income (loss) per share (in shares)	0			991			0	1,093
Unvested RSAs
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Dilutive securities included in computation of net income (loss) per share (in shares)	0			0			0	1
Unvested RSUs
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Dilutive securities included in computation of net income (loss) per share (in shares)	0			38			0	51

Net (Loss) Income per Share S_2

Net (Loss) Income per Share Schedule of Antidilutive Securities Excluded from Computation of Net Loss per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	7,409	4,363	7,265	4,086
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	6,735	4,350	6,581	3,772
Unvested RSAs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	0	2	0	0
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net loss per share (in shares)	674	11	684	314

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Millions	1 Months Ended
	Oct. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Common stock shares outstanding (in shares)		34,287,000	33,738,000
Subsequent Event
Subsequent Event [Line Items]
Common stock shares outstanding (in shares)	39,838,781
Gilead Transaction Agreements | Subsequent Event
Subsequent Event [Line Items]
Non-refundable upfront payment received	$ 85
Consideration received on transaction	35
Aggregate revenue for sales milestones	$ 685
Gilead Stock Purchase Agreement | Subsequent Event
Subsequent Event [Line Items]
Sale of stock, number of shares issued (in shares)	5,539,727