Codiak BioSciences (CDAKQ) 10-Q 5 Aug 21 2021 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 02, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	CODIAK BIOSCIENCES, INC.
Entity Central Index Key	0001659352
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		22,331,222
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	CDAK
Security Exchange Name	NASDAQ
Entity File Number	001-39615
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4926530
Entity Address, Address Line One	35 CambridgePark Drive
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02140
City Area Code	617
Local Phone Number	949-4100
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 113,681	$ 88,915
Prepaid expenses and other current assets	5,641	4,843
Total current assets	119,322	93,758
Property and equipment, net	30,263	31,410
Restricted cash, net of current portion	4,170	4,170
Operating right-of-use assets	21,519	22,003
Total assets	175,274	151,341
Current liabilities:
Accounts payable	1,782	2,018
Accrued expenses	7,689	8,870
Deferred revenue	9,117	5,281
Operating lease liabilities	2,333	1,482
Total current liabilities	20,921	17,651
Long-term liabilities:
Deferred revenue, net of current portion	41,746	57,416
Note payable, net of discount	25,230	24,960
Operating lease liabilities, net of current portion	35,306	36,540
Other long-term liabilities	207	207
Total liabilities	123,410	136,774
Commitments and contingencies (Note 8)
Stockholders’ equity:
Common stock, $0.0001 par value; 150,000,000 shares authorized as of June 30, 2021 and December 31, 2020; 22,272,975 and 18,787,579 shares issued and outstanding as of June 30, 2021 and December 31, 2020, respectively	2	2
Additional paid-in capital	372,069	302,655
Accumulated deficit	(320,207)	(288,090)
Total stockholders’ equity	51,864	14,567
Total liabilities and stockholders’ equity	$ 175,274	$ 151,341

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	22,272,975	18,787,579
Common stock, shares outstanding	22,272,975	18,787,579

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue:
Collaboration revenue	$ 890	$ 187	$ 14,081	$ 321
Total revenue	890	187	14,081	321
Operating expenses:
Research and development	15,419	11,622	31,969	30,013
General and administrative	6,937	4,358	13,525	8,591
Total operating expenses	22,356	15,980	45,494	38,604
Loss from operations	(21,466)	(15,793)	(31,413)	(38,283)
Other income (expense):
Interest expense	(704)	(294)	(1,401)	(589)
Interest income	9	19	14	242
Other income	352	155	683	215
Total other expense, net	(343)	(120)	(704)	(132)
Net loss	(21,809)	(15,913)	(32,117)	(38,415)
Cumulative dividends on redeemable convertible preferred stock		(3,420)		(6,839)
Net loss attributable to common stockholders	$ (21,809)	$ (19,333)	$ (32,117)	$ (45,254)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.99)	$ (6.44)	$ (1.51)	$ (15.07)
Weighted average common shares outstanding, basic and diluted	22,117,593	3,003,887	21,230,424	3,002,773
Comprehensive loss:
Net loss	$ (21,809)	$ (15,913)	$ (32,117)	$ (38,415)
Other comprehensive loss:
Unrealized loss on investments, net of tax of $0		(2)		(43)
Total other comprehensive loss		(2)		(43)
Comprehensive loss	$ (21,809)	$ (15,915)	$ (32,117)	$ (38,458)

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Unrealized loss on investments, tax	$ 0	$ 0	$ 0	$ 0

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' (EQUITY) - USD ($) $ in Thousands	Total	Initial Public Offering	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Series C Redeemable Convertible Preferred Stock	Common Stock	Common StockInitial Public Offering	Additional Paid-in Capital	Additional Paid-in CapitalInitial Public Offering	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ (192,833)							$ 2		$ 43	$ (192,878)
Temporary equity, Beginning balance, shares at Dec. 31, 2019			33,200,000	20,520,828	20,204,079
Temporary equity, Beginning balance at Dec. 31, 2019			$ 44,169	$ 81,108	$ 89,507
Beginning balance, shares at Dec. 31, 2019						2,997,040
Issuance of Series B redeemable convertible preferred stock in conjunction with sponsored research agreement, shares				62,500
Exercise of options to purchase common stock	104							104
Exercise of options to purchase common stock, shares						13,812
Accretion of preferred stock to redemption value	(6,792)							(3,245)			(3,547)
Temporary equity, Accretion of preferred stock to redemption value			$ 1,324	$ 2,416	$ 3,052
Stock-based compensation	3,141							3,141
Unrealized loss on investments	(43)									(43)
Net loss	(38,415)										(38,415)
Ending balance at Jun. 30, 2020	(234,838)							2			(234,840)
Temporary equity, Ending balance, shares at Jun. 30, 2020			33,200,000	20,583,328	20,204,079
Temporary equity, Ending balance at Jun. 30, 2020			$ 45,493	$ 83,524	$ 92,559
Ending balance, shares at Jun. 30, 2020						3,010,852
Beginning balance at Mar. 31, 2020	(216,980)							2		2	(216,984)
Temporary equity, Beginning balance, shares at Mar. 31, 2020			33,200,000	20,583,328	20,204,079
Temporary equity, Beginning balance at Mar. 31, 2020			$ 44,831	$ 82,292	$ 91,033
Beginning balance, shares at Mar. 31, 2020						3,002,380
Exercise of options to purchase common stock	86							86
Exercise of options to purchase common stock, shares						8,472
Accretion of preferred stock to redemption value	(3,420)							(1,477)			(1,943)
Temporary equity, Accretion of preferred stock to redemption value			$ 662	$ 1,232	$ 1,526
Stock-based compensation	1,391							1,391
Unrealized loss on investments	(2)									$ (2)
Net loss	(15,913)										(15,913)
Ending balance at Jun. 30, 2020	(234,838)							2			(234,840)
Temporary equity, Ending balance, shares at Jun. 30, 2020			33,200,000	20,583,328	20,204,079
Temporary equity, Ending balance at Jun. 30, 2020			$ 45,493	$ 83,524	$ 92,559
Ending balance, shares at Jun. 30, 2020						3,010,852
Beginning balance at Dec. 31, 2020	14,567					$ 2		302,655			(288,090)
Beginning balance, shares at Dec. 31, 2020						18,787,579
Exercise of options to purchase common stock	$ 2,770							2,770
Exercise of options to purchase common stock, shares	322,896					322,896
Stock-based compensation	$ 4,963							4,963
Issuance costs related to common stock	(560)
Issuance of common stock, net of issuance costs		$ 61,681							$ 61,681
Issuance of common stock, net of issuance costs, shares							3,162,500
Net loss	(32,117)										(32,117)
Ending balance at Jun. 30, 2021	51,864					$ 2		372,069			(320,207)
Ending balance, shares at Jun. 30, 2021						22,272,975
Beginning balance at Mar. 31, 2021	68,716					$ 2		367,112			(298,398)
Beginning balance, shares at Mar. 31, 2021						21,996,886
Exercise of options to purchase common stock	2,454							2,454
Exercise of options to purchase common stock, shares						276,089
Stock-based compensation	2,690							2,690
Issuance costs related to common stock	(187)							(187)
Net loss	(21,809)										(21,809)
Ending balance at Jun. 30, 2021	$ 51,864					$ 2		$ 372,069			$ (320,207)
Ending balance, shares at Jun. 30, 2021						22,272,975

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' (EQUITY) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Statement Of Stockholders Equity [Abstract]
Issuance of common stock upon public offering, net of issuance costs	$ 187	$ 560

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)
Cash flows from operating activities:
Net loss		$ (32,117)	$ (38,415)
Adjustments to reconcile net loss to net cash from operating activities:
Stock-based compensation expense		4,963	3,141
Non-cash interest expense		270	133
Depreciation and amortization expense	$ 900	2,759	1,970
Accretion of investments			(40)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(947)	3,207
Operating right-of-use assets		484	748
Other non-current assets			(10)
Accounts payable		(54)	(40)
Accrued expenses		(459)	(4,916)
Deferred revenue		(11,835)	9,679
Operating lease liabilities		(384)	10,093
Net cash used in operating activities		(37,320)	(14,450)
Cash flows from investing activities:
Purchases of property and equipment		(2,365)	(18,085)
Maturities of investments			73,062
Net cash (used in) provided by investing activities		(2,365)	54,977
Cash flows from financing activities:
Proceeds from exercise of common stock options		2,770	104
Proceeds from public offering of common stock, net of issuance costs		61,681
Net cash provided by financing activities		64,451	104
Net Increase in cash, cash equivalents and restricted cash		24,766	40,631
Cash, cash equivalents and restricted cash, beginning of period		93,085	14,853
Cash, cash equivalents and restricted cash, end of period	55,484	117,851	55,484
Supplemental disclosures:
Cash paid for interest		1,138	458
Non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued expenses		368	1,356
Deferred offering costs included in accrued expenses		16	18
Accretion of redeemable convertible preferred stock to redemption value			6,792
Operating right-of-use assets obtained in exchange for operating lease liabilities			23,186
Reconciliation to amounts within the condensed consolidated balance sheets
Cash and cash equivalents	50,947	113,681	50,947
Restricted cash	367		367
Restricted cash, net of current portion	4,170	4,170	4,170
Cash, cash equivalents and restricted cash at end of period	$ 55,484	$ 117,851	$ 55,484

Nature of the Business

Nature of the Business	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of the Business	1. Nature of the Business Codiak BioSciences, Inc. (collectively, with its consolidated subsidiaries, any of Codiak, we, us, or the Company) was incorporated in Delaware on June 12, 2015 and is headquartered in Cambridge, Massachusetts. Codiak is a clinical-stage biopharmaceutical company focused on pioneering the development of exosome-based therapeutics, a new class of medicines with the potential to transform the treatment of a wide spectrum of diseases with high unmet medical need. Exosomes have evolved as intercellular transfer mechanisms for complex, biologically active macromolecules and have emerged in recent years as a compelling potential drug delivery vehicle. By leveraging Codiak’s deep understanding of exosome biology, the Company has developed its engineering and manufacturing platform (the engEx Platform), to expand upon the innate properties of exosomes to design, engineer and manufacture novel exosome therapeutics. Codiak has utilized its engEx Platform to generate a deep pipeline of engineered exosomes (engEx exosomes) aimed at treating a broad range of diseases, including oncology, neuro-oncology, neuromuscular disease and infectious disease and rare disease. In September 2020, Codiak initiated clinical trials for its two lead product candidates, exoSTING and exoIL-12, which are being developed to address solid tumors. Codiak has multiple preclinical and discovery programs that it is advancing either independently or through its strategic collaborations with Jazz Pharmaceuticals Ireland Limited (Jazz) and Sarepta Therapeutics, Inc. (Sarepta). Since its inception, the Company has devoted substantially all of its resources to its research and development efforts, including activities to develop its engEx Platform, advance engEx product candidates into clinical trials, perform preclinical research to identify potential engEx product candidates, to perform process development to refine Codiak’s exosome engineering and manufacturing processes, and to provide general and administrative support for these operations. The Company has primarily funded its operations with proceeds from the sales of common stock, redeemable convertible preferred stock, collaborative and research arrangements with Jazz and Sarepta and its Loan and Security agreement with Hercules Capital, Inc. (Hercules). As of June 30, 2021, the Company has raised an aggregate of $168.2 million through the issuance of its redeemable convertible preferred stock and convertible debt, net of issuance costs, $24.6 million from its term loan facility with Hercules, net of issuance costs, and received $66.0 million in payments from its collaborations with Jazz and Sarepta. On October 16, 2020, the Company completed its initial public offering (IPO), pursuant to which it issued and sold 5,500,000 shares of its common stock at a public offering price of $15.00 per share, resulting in net proceeds of $74.4 million, after deducting underwriting discounts and commissions and other offering expenses. In addition, on February 17, 2021, the Company completed a follow-on public offering, pursuant to which it issued and sold 3,162,500 shares of its common stock (inclusive of the exercise of the underwriter’s option to purchase 412,500 additional shares of common stock) at a public offering price of $21.00 per share, resulting in aggregate net proceeds of $61.7 million, after deducting underwriting discounts and commissions and other offering expenses. The Company has incurred significant operating losses and negative cash flows from operations since inception. The Company expects to continue to incur significant expenses and operating losses for the foreseeable future. In addition, the Company anticipates that its expenses will increase significantly in connection with ongoing activities to support its engEx Platform development, drug discovery and preclinical and clinical development, in addition to creating a portfolio of intellectual property and providing administrative support. The Company does not expect to generate significant revenue from sales of its engEx product candidates unless and until clinical development has been successfully completed and regulatory approval is obtained. If the Company obtains regulatory approval for any of its investigational products, it expects to incur significant commercialization expenses. As a result, the Company will need substantial additional funding to support its continued operations and growth strategy. Until such a time as the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operations through the sale of equity, debt financings or other capital sources, including collaborations with other companies or other strategic transactions. The Company may be unable to raise additional funds or enter into such other agreements on favorable terms, or at all. If the Company fails to raise capital or enter into such agreements as, and when, needed, the Company may have to significantly delay, scale back or discontinue the development and commercialization of one or more of its product candidates or delay its pursuit of potential in-licenses or acquisitions. As of June 30, 2021, the Company had cash and cash equivalents of $113.7 million. Management believes that its cash and cash equivalent resources at June 30, 2021, will be sufficient to allow the Company to fund its current operating plan through at least the next twelve months from the issuance of these financial statements. The Company is subject to those risks associated with any biopharmaceutical company that has substantial expenditures for research and development. There can be no assurance that the Company’s research and development projects will be successful, that products developed will obtain necessary regulatory approval, or that any approved product will be commercially viable. In addition, the Company operates in an environment of rapid technological change and is largely dependent on the services of its employees and consultants. If the Company fails to become profitable or is unable to sustain profitability on a continuing basis, then it may be unable to continue its operations at planned levels and be forced to reduce its operations.

Summary of Basis of Presentatio

Summary of Basis of Presentation and Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Basis of Presentation and Significant Accounting Policies	2. Summary of Basis of Presentation and Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements that accompany these notes have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and applicable rules and regulations of the Securities and Exchange Commission (SEC) for interim financial reporting, consistent in all material respects with those applied in our Annual Report on Form 10-K for the year ended December 31, 2020 (2020 Annual Report). Any reference in these notes to applicable guidance is meant to refer to the authoritative accounting principles generally accepted in the United States as found in the Accounting Standard Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). Certain reclassifications were made to the 2020 financial statements to conform to the current period’s presentation. The reclassifications did not result in any changes to net loss or net stockholders’ deficit in either period presented. This report should be read in conjunction with the consolidated financial statements in our 2020 Annual Report. The consolidated financial statements include the Company and its subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Actual results could materially differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. Significant estimates relied upon in preparing the consolidated financial statements include, among others: estimates related to revenue recognition, the valuation of common stock and stock-based compensation awards, leases, accrued expenses and income taxes. Significant Accounting Policies The significant accounting policies used in preparation of these condensed consolidated financial statements for the three and six months ended June 30, 2021 are consistent with those described in our 2020 Annual Report. Recent accounting pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption. In December 2019, the FASB issued ASU No. 2019-12 Income Taxes (Topic 740)-Simplifying the Accounting for Income Taxes In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) .

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The following tables present information about the Company’s assets measured at fair value on a recurring basis, and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): JUNE 30, 2021 TOTAL LEVEL 1 LEVEL 2 LEVEL 3 NOT SUBJECT TO LEVELING(1) Assets: Cash equivalents: Money market funds $ 72,501 $ — $ — $ — $ 72,501 $ 72,501 $ — $ — $ — $ 72,501 DECEMBER 31, 2020 TOTAL LEVEL 1 LEVEL 2 LEVEL 3 NOT SUBJECT TO LEVELING(1) Assets: Cash equivalents: Money market funds $ 81,601 $ — $ — $ — $ 81,601 $ 81,601 $ — $ — $ — $ 81,601 (1) Certain cash equivalents that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. As of June 30, 2021 and December 31, 2020, the Company’s cash equivalents consisted of money market funds invested in US Treasury securities with original maturities of less than 90 days from the date of purchase. During the three and six months ended June 30, 2021 and 2020, there were no transfers between Level 1, Level 2 and Level 3. The fair value of the Company’s debt is classified as Level 2 for the periods presented and approximates its carrying value due to the variable interest rate.

Investments

Investments	6 Months Ended
	Jun. 30, 2021
Investments Debt And Equity Securities [Abstract]
Investments	4. Investments All of the Company’s investments matured during the year ended December 31, 2020. The Company did not hold any investments as of June 30, 2021. Investments with original maturities of less than 90 days are included in cash and cash equivalents on the condensed consolidated balance sheets. Investments with maturities of less than 12 months would be considered current and those investments with maturities greater than 12 months would be considered non-current. The Company did not recognize any realized gains or losses in the three and six months ended June 30, 2021 and 2020.

Property and Equipment, Net

Property and Equipment, Net	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	5. Property and Equipment, net Property and equipment, net, consisted of the following (in thousands): JUNE 30, 2021 DECEMBER 31, 2020 Leasehold improvements $ 24,093 $ 23,949 Laboratory equipment 17,839 14,837 Furniture and fixtures 1,288 1,288 Computer equipment and software 159 159 Construction-in-process 133 1,667 $ 43,512 $ 41,900 Less: Accumulated depreciation and amortization (13,249 ) (10,490 ) Property and equipment, net $ 30,263 $ 31,410 Depreciation and amortization expense for the three and six months ended June 30, 2021 was $1.4 million and $2.8, respectively.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Accrued Expenses	6. Accrued Expenses Accrued expenses consists of the following (in thousands): JUNE 30, 2021 DECEMBER 31, 2020 Accrued employee compensation $ 5,049 $ 5,040 Accrued external research and development costs 1,104 1,475 Accrued professional services and consulting 931 902 Other expenditures 360 846 Accrued facilities costs 245 607 $ 7,689 $ 8,870

Leases

Leases	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Leases	7. Leases We have entered into various long-term non-cancelable lease arrangements for our facilities, expiring at various times through 2029. Certain arrangements have free rent periods or escalating rent payment provisions; costs under such arrangements are recognized on a straight-line basis over the life of the leases. We have two locations in Massachusetts, our office and laboratory, located in Cambridge and manufacturing space, located in Lexington. Operating Leases 500 Technology Square The Company leased building space at 500 Technology Square in Cambridge, Massachusetts. Under the terms of the lease, the Company leased approximately 19,823 square feet for $1.5 million per year in base rent, which was subject to a 2.5% annual rent increase plus certain operating expenses and taxes. The Company accounted for this lease as an operating lease. The lease commenced on December 28, 2016 and originally expired on December 31, 2021. On August 26, 2019, the Company signed a lease termination to accelerate the expiration date of the lease to February 28, 2020. 4 Hartwell Place On March 5, 2019, the Company entered into a lease for manufacturing space at 4 Hartwell Place in Lexington, Massachusetts. Under the terms of the lease, the Company leases approximately 18,707 square feet for $0.9 million per year in base rent, which is subject to a 3.0% annual rent increase during the initial lease term, plus certain operating expenses and taxes. The lease term commenced in July 2019 and will end in December 2029. The Company has the option to extend the lease twice, each for a 5-year period, on the same terms and conditions as the current lease, subject to a change in base rent based on market rates. The Company has fully occupied the space as of December 31, 2020. Upon execution of the lease agreement, the Company provided a security deposit of $0.4 million which is held in the form of a letter of credit and was classified as non-current restricted cash on the condensed consolidated balance sheets as of June 30, 2021 and December 31, 2020. The lease provides the Company with a tenant improvement allowance of up to $1.3 million, which is being amortized as a reduction to rent expense over the remaining lease term. As of June 30, 2021, the Company had received all $1.3 million of the tenant improvement allowance. Costs incurred related to the allowance are capitalized as leasehold improvements. 35 CambridgePark Drive On March 22, 2019, the Company entered into a lease for office and laboratory space at 35 CambridgePark Drive in Cambridge, Massachusetts. Under the terms of the lease, the Company leases approximately 68,258 square feet for $4.9 million per year in base rent, which is subject to a 3.0% annual rent increase during the initial lease term, plus certain operating expenses and taxes. The lease term commenced upon execution of the lease on March 26, 2019 and is expected to end in November 2029 Sublease On April 27, 2020, the Company entered into a sublease for 23,280 square feet of its leased space at 35 CambridgePark Drive. Under the terms of the sublease, the sublessee is to pay the Company approximately $1.3 million per year, which is subject to a 3.0% annual rent increase, plus certain operating expenses. The Company remains jointly and severally liable under the head lease and accounts for the sublease as an operating lease. The lease term commenced on May 18, 2020 and is expected to end in May 2022. The sublessee has the option to extend the sublease for a one-year The components of operating lease costs were as follows (in thousands): FOR THE THREE MONTHS ENDED JUNE 30, FOR THE SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Operating lease costs $ 1,209 $ 1,209 $ 2,418 $ 2,421 Short-term lease costs 7 6 13 9 Variable lease costs 590 493 1,259 1,110 Sublease income (348 ) (158 ) (704 ) (158 ) $ 1,458 $ 1,550 $ 2,986 $ 3,382 Variable lease costs were primarily related to operating expenses, taxes and utilities associated with the operating leases, which were assessed based on the Company’s proportionate share of such costs for the leased premises. Additional lease information is summarized in the following table (in millions, except lease term and discount rate): SIX MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 Cash paid for amounts included in the measurement of operating lease liabilities $ 3.0 $ 3.1 Weighted-average remaining lease term - operating leases (years) 8.4 9.4 Weighted-average discount rate - operating leases 10.3 % 10.3 % Undiscounted cash flows used in calculating the Company’s operating lease liabilities and amounts to be received under the sublease at 35 CambridgePark Drive as of June 30, 2021 are as follows (in thousands): Fiscal Year OPERATING LEASE PAYMENTS SUBLEASE RECEIPTS NET OPERATING LEASE PAYMENTS 2021 (remainder of the year) $ 2,980 $ 644 $ 2,336 2022 6,123 483 5,640 2023 6,307 6,307 2024 6,496 6,496 2025 6,691 6,691 Thereafter 28,287 28,287 Total undiscounted cash flows $ 56,884 $ 1,127 $ 55,757 Less: Amounts representing interest (19,245 ) Present value of lease liabilities $ 37,639

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and contingencies Purchase commitments Under the Company’s Sponsored Research Agreement with the University of Texas MD Anderson Cancer Center (MDACC), as amended (the MDACC Research Agreement), the Company was obligated to pay fixed quarterly cash payments to MDACC over the term of the agreement. The Company was also obligated to make additional quarterly payments pursuant to the MDACC Research Agreement, payable in the form of a fixed number of the Company’s Series B redeemable convertible preferred stock throughout the remainder of the agreement. Pursuant to the Third Amendment to the MDACC Research Agreement, the termination date was modified to be effective December 31, 2019. The Company made the final $1.2 million cash payment and issued the remaining shares of Series B redeemable convertible preferred stock to MDACC in January 2020. There are no further payments or share issuances owed to MDACC pursuant to the MDACC Research Agreement. In November 2015, the Company entered into a Patent and Technology License Agreement with MDACC, as amended in April 2018 (the MDACC License Agreement). Under the terms of this agreement the Company is obligated to pay milestone payments upon the achievement of development and regulatory milestones and payments upon the execution of sublicenses for qualifying products, in addition to potential royalty payments on commercial products. Additionally, the Company has a license agreement with Kayla Therapeutics S.A.S. (Kayla) under which the Company is obligated to make milestone payments upon the achievement of clinical and regulatory milestones and payments upon the execution of sublicenses, in addition to potential royalty payments on commercial products. The first milestone was achieved upon the first dosing of exoSTING to the first subject in the Company’s Phase 1/2 clinical trial in September 2020. Upon achievement of the milestone, the Company was obligated to make a nonrefundable payment of $15.0 million in cash and issue 177,318 shares of common stock to Kayla. The common stock was issued as of the date of dosing, and the cash payment of $15.0 million was paid during 2020. The expense related to the milestone payment to Kayla was recorded as research and development expense in the year ended December 31, 2020 because the associated asset was in development at the time the contingency that triggered the milestone was resolved. Purchase orders The Company has agreements with third parties for various services, including services related to clinical and preclinical operations and support, for which the Company is not contractually able to terminate for convenience to avoid future obligations to the vendors. Certain agreements provide for termination rights subject to termination fees or wind down costs. Under such agreements, the Company is contractually obligated to make certain payments to vendors, primarily to reimburse them for their unrecoverable outlays incurred prior to cancelation. The actual amounts the Company could pay in the future to the vendors under such agreements may differ from the purchase order amounts due to cancellation provisions. Indemnification agreements The Company enters into standard indemnification agreements and/or indemnification sections in other agreements in the ordinary course of business. Pursuant to the agreements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally the Company’s business partners. The term of these indemnification agreements is generally perpetual any time after execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. The Company does not believe that the outcome of any existing claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it had not accrued any liabilities related to such obligations in its condensed consolidated balance sheets as of June 30, 2021 or December 31, 2020. Legal proceedings The Company is not currently party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of FASB ASC Topic 450, Contingencies

Indebtedness

Indebtedness	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Indebtedness	9. Indebtedness On September 30, 2019 (the Closing Date), the Company entered into a Loan and Security Agreement (the Loan Agreement) with Hercules pursuant to which a term loan in an aggregate principal amount of up to $75.0 million (the Term Loan Facility) is available to the Company in four tranches, subject to certain terms and conditions. $10.0 million of the first tranche was advanced to the Company on the Closing Date and an additional $15.0 million under the first tranche was drawn down on July 24, 2020. Upon satisfaction of certain liquidity and clinical milestones, the second tranche was available under the Term Loan Facility, which allowed the Company to borrow an additional amount up to $10.0 million through March 31, 2021. The Company did not elect to borrow against the second $10.0 million tranche. Upon satisfaction of certain additional clinical milestones, the third tranche was available under the Term Loan Facility, which allowed the Company to borrow an additional amount up to $10.0 million through June 30, 2021. The Company did not elect to borrow against the third $10.0 million tranche. The fourth tranche, which allows the Company to borrow an additional amount up to $30.0 million, will be available upon Hercules’ approval on or prior to December 15, 2021. Advances under the Term Loan Facility bear interest at a rate equal to the greater of (i) 9.00% plus the Prime Rate (as reported in The Wall Street Journal) less 5.25%, and (ii) 9.00%. During the three months ended June 30, 2021 the interest only period under the Term Loan Facility was extended based on the satisfaction of certain performance milestones. The Company will now make interest only payments through November 1, 2022. Following the interest only period, the Company will repay the principal balance and interest on the advances in equal monthly installments through October 1, 2024. The Company may prepay advances under the Loan Agreement, in whole or in part, at any time subject to a prepayment charge (Prepayment Premium) equal to: (i) 2.0% of amounts so prepaid, if such prepayment occurs during the first year following the Closing Date; (ii) 1.5% of the amount so prepaid, if such prepayment occurs during the second year following the Closing Date, or (iii) 1.0% of the amount so prepaid, if such prepayment occurs after the second year following the Closing Date. Upon prepayment or repayment of all or any of the term loans under the Term Loan Facility, the Company will pay (in addition to any Prepayment Premium) an end of term charge of 5.5% of the aggregate funded amount under the Term Loan Facility. With respect to the first tranche, an end of term charge of $ 1.4 million will be payable upon any prepayment or repayment. To the extent that the Company is provided additional advances under the Term Loan Facility, the 5.5% end of term charge will be applied to any such additional amounts. The Term Loan Facility is secured by a lien on substantially all of the Company’s assets, other than the Company’s intellectual property. The Company has agreed to not pledge or grant a security interest on the Company’s intellectual property to any third party. The Term Loan Facility also contains customary covenants and representations, including a liquidity covenant, whereby the Company is obligated to maintain, in an account covered by Hercules’ account control agreement, an amount equal to the lesser of: (i) 110% of the amount of the Company’s obligations under the Term Loan Facility or (ii) the Company’s then existing cash and cash equivalents; financial reporting covenant and limitations on dividends, indebtedness, collateral, investments, distributions, transfers, mergers or acquisitions, taxes, corporate changes, deposit accounts, and subsidiaries. Upon issuance, the initial advance under the first tranche was recorded as a liability with an initial carrying value of $9.5 million, net of debt issuance costs. The July 24, 2020 advance under the first tranche was recorded as a liability with an initial carrying value of $15.0 million. The initial carrying value of all outstanding advances will be accreted to the repayment amount, which includes the outstanding principal plus the end of term charge, through interest expense using the effective interest rate method over the term of the loan. As of June 30, 2021 and December 31, 2020, the carrying value of the term loan was $25.2 million and $25.0 million, respectively, which is classified as a long-term liability on the Company’s condensed consolidated balance sheets as of each respective period. The fair value of debt is classified as Level 2 for the periods presented and approximates its carrying value. The events of default under the Loan Agreement include, without limitation, and subject to customary grace periods, the following: (i) any failure by the Company to make any payments of principal or interest under the Loan Agreement, (ii) any breach or default in the performance of any covenant under the Loan Agreement, (iii) the occurrence of a material adverse effect, (iv) any making of false or misleading representations or warranties in any material respect, (v) the Company’s insolvency or bankruptcy, (vi) certain attachments or judgments on the assets of the Company or (vii) the occurrence of any material default under certain agreements or obligations of the Company’s involving indebtedness. If an event of default occurs, Hercules is entitled to take enforcement action, including acceleration of amounts due under the Loan Agreement. The future principal payments under the Loan Agreement are as follows as of June 30, 2021 (in thousands): Fiscal Year PRINCIPAL 2021 $ — 2022 1,910 2023 12,097 2024 10,993 $ 25,000 During the three and six months ended June 30, 2021, the Company recognized $0.7 million and $1.4 million of interest expense related to the Loan Agreement, respectively. During the three and six months ended June 30, 2020, the Company recognized $0.3 million and $0.6 million of interest expense related to the Loan Agreement, respectively. Such amounts were reflected as interest expense on the condensed consolidated statements of operations and comprehensive loss.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2021
Employee Service Share Based Compensation Aggregate Disclosures [Abstract]
Stock-Based Compensation	10. Stock-based compensation Stock plans As of June 30, 2021, the Company has granted service-based awards, which vest over a defined period of service, and performance-based and market-based awards, which vest upon the achievement of defined conditions. Service-based awards generally vest over a four-year 2020 Stock Option and Incentive Plan The 2020 Stock Option and Incentive Plan (the 2020 Plan), was adopted by the Company’s board of directors in October 2020, approved by the Company’s stockholders in October 2020 and became effective as of October 12, 2020. The 2020 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units, and other stock-based awards. The number of shares of the Company’s common stock initially reserved for issuance under the 2020 Plan was 1,043,402 shares. The shares of the Company’s common stock subject to outstanding awards under the 2015 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right will be added back to the shares of common stock available for issuance under the 2020 Plan. As of June 30, 2021, there were 1,281,040 shares available for future issuance under the 2020 Plan. The Company’s stock options expire after approximately ten years from the date of grant. As of June 30, 2021, the Company does not hold any treasury shares. Upon stock option exercise, the Company issues new shares and delivers them to the participant. 2020 Employee stock purchase plan The Company’s 2020 Employee Stock Purchase Plan, (the ESPP) was adopted by our board of directors in October 2020, approved by the Company’s stockholders in October 2020 and became effective October 12, 2020. The ESPP initially provides participating employees with the opportunity to purchase up to an aggregate of 208,680 shares of the Company’s common stock. The number of shares of common stock reserved for issuance under the ESPP will automatically increase on each January 1st, beginning on January 1, 2021 and ending on January 1, 2030, by the lesser of (i) 834,720 shares of common stock, (ii) 0.5% of the outstanding shares of common stock on the immediately preceding December 31st or (iii) such lesser number of shares as determined by the administrator of the ESPP. There was no increase in the number of common stock reserved for issuance under the ESPP as of June 30, 2021. Stock Options The following table summarizes the Company’s option activity during the six months ended June 30, 2021: NUMBER OF SHARES WEIGHTED AVERAGE EXERCISE PRICE PER SHARE WEIGHTED AVERAGE REMAINING CONTRACTUAL TERM AGGREGATE INTRINSIC VALUE (1) (In years) (In thousands) Outstanding as of December 31, 2020 4,543,318 $ 8.52 7.22 $ 108,048 Granted 1,140,400 24.77 Exercised (322,896 ) 8.58 Forfeited/Cancelled (194,165 ) 14.33 Outstanding as of June 30, 2021 5,166,657 11.88 7.02 41,555 Exercisable as of June 30, 2021 2,652,701 7.05 5.50 30,455 Vested and expected to vest as of June 30, 2021 5,166,657 11.88 7.02 41,555 (1) Aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock as of June 30, 2021 and December 31, 2020. The weighted average grant date fair value per share of options granted during the three and six months ended June 30, 2021, was $11.63 per share and $15.35 per share, respectively. The weighted average grant date fair value per share of options granted during the three and six months ended June 30, 2020 was $6.27 per share and $6.31 per share, respectively. The aggregate intrinsic value of stock options exercised during the three and six months ended June 30, 2021 was $ million and $ million, respectively. The aggregate intrinsic value of stock options exercised during the three and six months ended June 30, 2020 was less than $ millio n in each period, respectively . Stock Option Valuation Service-based awards The key assumptions used in the Black-Scholes option pricing model on the date of grant for options with service-based vesting conditions were as follows, presented on a weighted average basis: THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Risk-free interest rate 1.08 % 0.46 % 0.77 % 1.38 % Expected term (in years) 6.12 6.25 6.21 6.25 Expected volatility 65.28 % 68.17 % 68.82 % 67.17 % Expected dividend yield 0.00 % 0.00 % 0.00 % 0.00 % Fair value per share of common stock $ 11.63 $ 6.27 $ 15.35 $ 6.31 Performance-based awards The Company did not grant any performance-based awards during the three and six months ended June 30, 2021 and 2020. Stock-based Compensation Expense The following table presents the components and classification of stock-based compensation expense (in thousands): THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Research and development $ 1,221 $ 788 $ 2,279 $ 1,821 General and administrative 1,469 603 2,684 1,320 $ 2,690 $ 1,391 $ 4,963 $ 3,141 Employee $ 2,620 $ 1,329 $ 4,859 $ 2,879 Non-employee 70 62 104 262 $ 2,690 $ 1,391 $ 4,963 $ 3,141 The Company did not recognize any stock-based compensation expense during the three months ended June 30, 2021 related to performance-based awards and recognized less than $0.1 million during the six months ended June 30, 2021 related to performance-based awards that vested upon achievement of their underlying performance condition. The Company did not recognize expense related to performance-based awards during the three and six months ended June 30, 2020 because the associated performance conditions were not deemed probable of achievement. As of June 30, 2021, the total unrecognized compensation expense related to the Company’s option awards was $25.3 million, which the Company expects to recognize over a weighted-average period of approximately 3.07 years.

Collaborative Arrangements

Collaborative Arrangements	6 Months Ended
	Jun. 30, 2021
Collaboration Agreements [Abstract]
Collaborative Arrangements	11. Collaboration agreements The following table summarizes our total consolidated net revenue from our strategic collaborators for the periods presented (in thousands): THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, Collaboration Revenue by Strategic Collaborator: 2021 2020 2021 2020 Jazz $ (511 ) $ 187 $ 11,107 $ 321 Sarepta 1,401 — 2,974 — Total collaboration revenue $ 890 $ 187 $ 14,081 $ 321 The following tables present changes in the Company’s contract assets and liabilities for the six months ended June 30, 2021 (in thousands): SIX MONTHS ENDED JUNE 30, 2021 BALANCE BEGINNING OF PERIOD ADDITIONS DEDUCTIONS BALANCE END OF PERIOD Contract assets: Account receivable (1) $ — $ 2,248 $ (842 ) $ 1,406 Contract liabilities: Deferred revenue $ 62,697 $ — $ (11,834 ) $ 50,863 (1) Included in prepaid expenses and other current assets as shown within the condensed consolidated balance sheets. During the three and six months ended June 30, 2021 and 2020, the Company recognized the following revenue (in thousands): THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Revenue recognized in the period from: Amounts included in deferred revenue at the beginning of the period $ 890 $ 187 $ 14,081 $ 321 Jazz collaboration and license agreement Agreement summary On January 2, 2019, the Company entered into a Collaboration and License Agreement (the Jazz Collaboration Agreement) with Jazz focused on the research, development and commercialization of exosome therapeutics to treat cancer. The Company granted Jazz an exclusive, worldwide, sublicensable, royalty-bearing license to develop, manufacture and commercialize therapeutic candidates directed at up to five oncogene targets (each, a Development and Commercialization License) to be developed using the Company’s engEx Platform for exosome therapeutics. The targets, one of which is NRAS, have been validated in hematological malignancies and solid tumors but generally have been undruggable with current modalities. Four of the targets were identified at the inception of the collaboration (the Initial Collaboration Targets) and on June 30 , Under the terms of the Jazz Collaboration Agreement, the Company is responsible for the initial development of therapeutic candidates directed at all five targets as well as the costs associated with such development activities. In addition, the Company is responsible for development costs up to and including IND acceptance, and certain development costs of the Phase 1, Phase 1/2 and Phase 2 clinical trials for each of the first two therapeutic candidates to commence clinical trials. In April 2021, the Company and Jazz mutually agreed to discontinue their work on exoASO™-STAT3 (STAT3), one of the five oncogene targets subject to the Jazz Collaboration Agreement. Following the conclusion of the applicable clinical trials for the first two candidates, and for the remaining three candidates, Jazz will be responsible for the further development and associated costs of the therapeutic candidates, including all Phase 3 and any Phase 4 clinical trials, potential regulatory submissions and commercialization for each product at its sole cost and expense. The Company has the option to participate in co-commercialization and cost/profit-sharing in the US and Canada on up to two products, subject to a one-time veto right by Jazz (which exercise of such veto may result in an additional $20.0 million milestone payment to the Company related to regulatory approval of the product). Should the Company choose to exercise this option, the Company and Jazz will equally split most of the remaining development costs and the net profits or losses in the US and Canada, while the Company would receive milestones and royalties for sales in other parts of the world. In the event that the Company does not exercise its option, the Company will receive milestones and royalties based upon sales worldwide. As part of the Jazz Collaboration Agreement, Jazz has paid the Company an up-front payment of $56.0 million. The Company is eligible to receive up to $20.0 million in preclinical development milestone payments, the first of which is for $10.0 million and will be due from Jazz upon the second initiation of IND-enabling toxicology studies for a collaboration target. The Company is also eligible to receive milestone payments totaling up to $200.0 million per product based on IND acceptance, clinical and regulatory milestones, including approvals in the US, the EU and Japan, and sales milestones. In addition, the Company will receive tiered royalties on net sales of each approved product, with percentages ranging from mid-single digits in the lowest tier to high teens in the highest tier, excluding such net sales in the US and Canada if the Company has exercised its option to co-commercialize the related product. The milestone and royalty payments are each subject to reduction under certain specified conditions set forth in the Jazz Collaboration Agreement, provided, however, that in the case of a termination with respect to a licensed compound that is a Development Candidate (as defined below), Jazz will maintain its obligation to reimburse the Company for certain development costs. Either party can terminate the agreement with respect to a region and a target upon the other party’s material breach relating to such region and target, subject to specified notice and cure provisions. Jazz also has the right to terminate the agreement in its entirety or in part (with respect to a particular collaboration target, research program, licensed compound or product, region or, in some cases, country) for convenience at any time upon 180 days’ written notice or for safety reasons immediately upon notice, provided, however, that in the case of a termination for convenience with respect to a licensed compound that is a Development Candidate, Jazz will maintain its obligation to reimburse the Company for certain development costs. Absent early termination, the term of the Jazz Collaboration Agreement will continue on a country-by-country basis and licensed product-by-licensed product basis, until the expiration of the royalty payment obligations for the country and the licensed product (or, in the case of a shared territory for an optioned product, will continue for so long as such optioned product is being sold by Jazz or its affiliates or sublicensees in the shared territory). Any expiration or termination of the Jazz Collaboration Agreement does not affect the rights and obligations of the parties that accrued prior to the expiration or termination date. Upon termination of the Jazz Collaboration Agreement, all licenses granted by the Company to Jazz will immediately terminate. Accounting analysis The Company evaluated the Jazz Collaboration Agreement, as amended, in accordance with the provisions of ASC 606. The Company concluded that the contract counterparty is a customer in the arrangement. The Company accounted for the extension of the exercise period pursuant to the First Amendment as a modification. The Company did not account for the First Amendment as a separate contract because the amendment did not result in an increase to the scope of the arrangement nor was the pricing of the arrangement increased. Accordingly, the First Amendment was combined with the Jazz Collaboration Agreement. For the remaining promised goods and services that are distinct from the goods and services that were transferred on or before the date of the effectiveness of the First Amendment, the Company has accounted for the modification on a prospective basis as if it were a termination of the existing contract and the creation of a new contract. Conversely, the remaining promised goods and services that are not distinct from the goods and services that were transferred on or before the date of the effectiveness of the First Amendment were deemed to form part of a single performance obligation that is partially satisfied so they have been accounted for as part of the existing contract for which an adjustment has been recorded on a cumulative catch-up basis at the date of the modification. The Company determined that the change to the arrangement that was enacted by the First Amendment did not impact the identification of the promises in the contract. The Company’s obligations under the Jazz Collaboration Agreement, as amended, comprise the following substantive promises: • Development and Commercialization Licenses for each of the Initial Collaboration Targets (each, a Development and Commercialization License Promise) • Research services related to the conduct of the applicable work plan, which provides a framework for the applicable research activities, performed on a target-by-target basis, pursuant to a program aimed at identifying and evaluating exosome therapeutics directed to the individual targets (each such program for research activities, a Research Program) and sets forth the specific activities to be undertaken over the course of such Research Program, including the associated objectives and timelines therefor (each, a Work Plan) for each of the four Initial Collaboration Targets that are the subject of the collaboration (each, a Research Services Promise) • Preclinical and clinical services related to the completion of the Early Development Plans (as defined below) for each of the four Initial Collaboration Targets that are the subject of the collaboration (each, a Development Services Promise) • Material right associated with Jazz’s ability to obtain either: (i) a Development and Commercialization License, research services pursuant to an associated Work Plan, and preclinical and clinical services pursuant to an associated plan that describes the preclinical studies, manufacturing process development, and clinical development to be performed with respect to an applicable product candidate that the parties determine is suitable for IND-enabling studies (each such product candidate, a Development Candidate) and the associated timelines, budget and resource allocation therefor (each, an Early Development Plan) for an Additional Target or (ii) research services pursuant to an associated Work Plan and preclinical and clinical services pursuant to an associated Early Development Plan for an additional Research Program for one of the Initial Collaboration Targets (an Additional Research Program, and such material right, the Additional Target or Program Material Right Promise) • Material right associated with Jazz’s ability to obtain a Development and Commercialization License, research services pursuant to an associated Work Plan and preclinical and clinical services pursuant to an associated Early Development Plan for a Replacement Target (the Replacement Target Material Right Promise) • Material rights associated with Jazz’s ability to obtain services with respect to non-GLP toxicology studies for two Backup Candidates (each, a Backup Candidate Material Right Promise) For purposes of evaluating the Jazz Collaboration Agreement, as amended, in accordance with ASC 606, the Company has determined that the ability for Jazz to either nominate an Additional Target or request an Additional Research Program represents a material right because the pricing inherent in such option provides the customer with a discount that is incremental to the range of discounts that would otherwise be granted for the related goods and services to comparable customers. More specifically, the Development and Commercialization License and associated research services under the related Work Plan that would be provided pursuant to Jazz’s option to include an Additional Target within the scope of the arrangement would be provided at no additional cost to Jazz. Similarly, the research services under a Work Plan that would be provided upon an exercise of Jazz’s option to request an Additional Research Program would be provided at no additional cost to Jazz. The deadline for the exercise of this option was extended by a defined period of time under the First Amendment, but the option was otherwise unchanged. Additionally, the Company has determined that the ability for Jazz to elect a Replacement Target represents a material right because the pricing inherent in such option provides the customer with a discount that is incremental to the range of discounts that would otherwise be granted for the related goods and services to comparable customers. Consistent with an Additional Target, to the extent Jazz requests that a Replacement Target be included within the scope of the arrangement, the Development and Commercialization License and associated research services under the related Work Plan would be provided at no additional cost to Jazz. Lastly, the Company determined that the ability for Jazz to request the Company to render services with respect to non-GLP toxicology studies for certain Backup Candidates represents a material right because the pricing inherent in such option also provides the customer with a discount that is incremental to the range of discounts that would otherwise be granted for the related services to comparable customers. Along the same lines as the other material rights, upon Jazz’s exercise, the Company would render services with respect to the conduct of non-GLP toxicology studies for one Backup Candidate for each of the first two Development Candidates at no cost to Jazz. The Company determined that the extension of the exercise period pursuant to the First Amendment did not affect the composition of the performance obligations. For purposes of evaluating the Jazz Collaboration Agreement, as amended, in accordance with ASC 606, the Company determined that the Development and Commercialization License Promise for each of the Initial Collaboration Targets is neither capable of being distinct nor distinct within the context of the contract from the associated Research Services Promise and Development Services Promise. Due to the specialized nature of the services to be provided by the Company, specifically with respect to the Company’s proprietary expertise related to exosome engineering and manufacturing, the customer cannot benefit from or utilize the license without the research and development services. Moreover, the Company concluded that the Development and Commercialization License Promise, Research Services Promise and Development Services Promise for each individual target are interrelated to and interdependent on each other. Due to the nature of the services and capabilities of the parties, the customer cannot derive its intended benefit from the license without the accompanying research and development services to be performed pursuant to the underlying Work Plans and Early Development Plans. The nature of the combined performance obligation is to provide certain research and development services for targets that are designated for inclusion in the arrangement in order to transfer a combined item to the customer in the form of a product candidate for which human proof of concept has been established. As such, the Company has treated the Development and Commercialization License Promise, Research Services Promise and Development Services Promise related to each target as a combined performance obligation (each, a License and Services Performance Obligation; collectively, the License and Services Performance Obligations). However, the Company has determined that the License and Services Performance Obligation associated with each target is distinct from the License and Services Performance Obligation for the other targets because: (i) Jazz can benefit from the license and research and development services for a given target on their own since the results related thereto can be evaluated discretely and (ii) e ach bundle for an individual target is separately identifiable since it does not affect either the Company’s ability to perform or Jazz’s ability to assess the program for any other target. Thus, the License and Services Performance Obligation for each target is a separate performance obligation. Each of the material right promises has been deemed a distinct performance obligation due to their nature as specified in ASC 606. Therefore, the Company has identified the following eight performance obligations in connection with its obligations under the Jazz Collaboration Agreement, as amended: • Combined performance obligation comprising the Development and Commercialization License Promise, Research Services Promise and Development Services Promise for each of the four Initial Collaboration Targets (the License and Services Performance Obligation: Initial Collaboration Target #1, License and Services Performance Obligation: Initial Collaboration Target #2, License and Services Performance Obligation: Initial Collaboration Target #3 and License and Services Performance Obligation: Initial Collaboration Target #4, respectively) • Material right associated with Jazz’s option to request either: (i) an Additional Target or (ii) an Additional Research Program (the Additional Target or Program Material Right Performance Obligation) • Material right associated with Jazz’s option to request a Replacement Target (the Replacement Target Material Right Performance Obligation) • Material right associated with Jazz’s option to request certain Backup Candidates (the Backup Candidate Material Right Performance Obligation: Backup Candidate #1 and Backup Candidate Material Right Performance Obligation: Backup Candidate #2, respectively) Accordingly, in accounting for the modification resulting from the First Amendment, the License and Services Performance Obligations were treated as part of the existing contract, whereas the material right performance obligations were treated as a termination of the existing contract and the creation of a new contract. At inception of the arrangement, the Company measured the transaction price solely in reference to the $56.0 million non-refundable and non-creditable up-front payment. None of the variable consideration payable under the arrangement was included in the transaction price at inception. The Company estimates the amount of variable consideration to which it expects to be entitled associated with cost reimbursements, in addition to preclinical development, IND acceptance, clinical and regulatory milestones, using the most likely amount method. The Company did not include any cost reimbursements in the transaction price at inception due to the uncertainty around the Company’s receipt of such amounts as it is dependent upon viable product candidates progressing through development. All preclinical development, IND acceptance, clinical and regulatory milestone payments were excluded from the transaction price at inception due to the uncertainty of initiating the specified phase of preclinical development, achieving the associated development criteria or receiving approval or acknowledgement from the relevant regulatory authorities. Further, regulatory milestone payments will be excluded from the transaction price until the associated regulatory milestone is achieved. The sales milestone payments, royalties and profit share are subject to the royalty recognition constraint because the associated license is deemed to be the sole or predominant item to which the payments relate. As of December 23, 2020, the total remaining consideration was $55.0 million which solely comprises the transaction price on the original contract not yet recognized as revenue because the modification did not change the arrangement consideration. The Company updates its assessment of the estimated transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. There have been no changes to the Company’s estimate of variable consideration since inception of the arrangement through June 30, 2021 . As of June 30, 2021 , the Company has not achieved any preclinical development, IND acceptance, clinical, regulatory or sales milestones or earned any royalties or profit share under the Jazz Collaboration Agreement. Upon modification, the Company allocated the transaction price associated with the remaining consideration to each of the identified performance obligations on a relative standalone selling price basis. Certain elements of variable consideration are attributable to specific performance obligations; however, no amounts of variable consideration have been included in the transaction price. The Company updated the standalone selling prices for each of the identified performance obligations to reflect assumptions and estimates in effect on the modification date. The Company determined the updated standalone selling prices for each of the performance obligations included in the Jazz Collaboration Agreement considering relevant market conditions, entity-specific factors and information about the customer, while maximizing the use of available observable inputs. As a result, the transaction price associated with the remaining consideration was reallocated to the identified performance obligations as follows (in thousands): PERFORMANCE OBLIGATION ALLOCATED TRANSACTION PRICE License and Services Performance Obligation: Initial Collaboration Target #1 $ 12,717 License and Services Performance Obligation: Initial Collaboration Target #2 13,702 License and Services Performance Obligation: Initial Collaboration Target #3 10,866 License and Services Performance Obligation: Initial Collaboration Target #4 13,593 Additional Target or Program Material Right Performance Obligation 2,812 Replacement Target Material Right Performance Obligation 1,188 Backup Candidate Material Right Performance Obligation: Backup Candidate #1 47 Backup Candidate Material Right Performance Obligation: Backup Candidate #2 47 Transaction Price $ 54,972 The standalone selling price for each of the License and Services Performance Obligations was estimated using a hybrid approach whereby the standalone selling price for each of the Development and Commercialization License Promises was estimated using an income approach, while the standalone selling price of the Research Services Promises and Development Services Promises for each of the plans associated with the individual targets were estimated using an expected cost-plus margin approach. The discounted cash flow analysis utilized in deriving the estimated standalone selling price for each of the Development and Commercialization License Promises included such key assumptions as: development timeline, revenue forecast, discount rate and probabilities of technical and regulatory success. The cost-plus margin approach utilized in deriving the estimated standalone selling price for the Research Services Promises and Development Services Promises for each target was based on the estimate of the overall effort to perform the underlying Work Plans and Early Development Plans and an estimated market rate for the associated services. The standalone selling prices for the Additional Target or Program Material Right Performance Obligation and Replacement Target Material Right Performance Obligation were estimated based on a similar hybrid approach as the License and Services Performance Obligations, but also contemplated the discount the customer could receive without exercising the corresponding option and the likelihood that the respective option will be exercised. The standalone selling price for the Additional Target or Program Material Right Performance Obligation also reflects the likelihood that each of the alternatives will be selected by Jazz. Lastly, the standalone selling prices for the Backup Candidate Material Right Performance Obligations was estimated using an expected cost-plus margin approach based on the estimate of the overall effort to perform the associated non-GLP toxicology studies. Amounts allocated to each of the License and Services Performance Obligations is recognized as revenue over time commensurate with the term of the associated Research Program and development activities performed pursuant to a program focused on establishing human proof-of-concept for a given target using a proportional performance model which depicts the Company’s performance in transferring control to the customer. The Company utilizes a cost-based input method to measure progress because such method best reflects the satisfaction of the performance obligation as the underlying services are provided. In applying the cost-based input method of revenue recognition, the Company uses actual costs incurred relative to the budgeted costs to complete each of the respective programs. These costs consist primarily of internal full-time equivalent effort and third-party costs. Allocated amounts are recognized as revenue based on actual costs incurred as a percentage of total budgeted costs. A cost-based input method of revenue recognition requires management to make estimates of costs to complete the Company’s performance obligations. In making such estimates, significant judgment is required to evaluate assumptions related to cost estimates. The cumulative effect of revisions to estimated costs to complete the programs is recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods . On April 2, 2021, the Company and Jazz mutually agreed to discontinue their work on STAT3, one of five oncogene targets subject to the Jazz Collaboration Agreement. The Company recognized the remaining $10.9 million in deferred revenue allocated to this target during the three months ended March 31, 2021 as the preclinical activities that informed this decision were completed prior to the end of the period. On June 30, 2021, Jazz formally nominated the fifth collaboration target, ahead of the contractual deadline of July 2, 2021. The Company will recognize the $2.8 million of revenue allocated to this performance obligation consistent with all active Jazz targets, recording revenue based on actual costs incurred relative to the budgeted costs to complete each of the respective programs. As of June 30, 2021, there are three remaining material rights outstanding under the Jazz Collaboration Agreement. During the three months ended June 30, 2021, the Company recorded an immaterial error correction associated with revenue recognized under the Jazz Collaboration Agreement resulting in a net reduction to revenue totaling $0.5 million. The Company recognized $11.1 million of revenue during the six months ended June 30, 2021. The Company recognized $0.2 million and $ 0.3 million of revenue during the three and six months ended June 30, 2020 under with the Jazz Collaboration Agreement, respectively. The aggregate amount of the transaction price allocated to the License and Services Performance Obligations that were unsatisfied, as of June 30, 2021 was $42.8 million, which is expected to be recognized over the respective term of the associated Research Program and development activities for each target, through approximately 2026. The aggregate amount of the transaction price allocated to all other performance obligations that were unsatisfied as of June 30, 2021 was $1.3 million, which is expected to be recognized upon the earlier of when the respective option is exercised or expires. As of June 30, 2021 and December 31, 2020, the Company had $43.9 million and $55.0 million, respectively, of deferred revenue related to the Company’s collaboration with Jazz which is classified as current or long-term in the accompanying condensed consolidated balance sheets based on the expected timing of satisfaction of the underlying goods and/or services. The Company incurred $0.7 million and $1.3 million of costs associated with its obligations under the arrangement with Jazz during the three and six months ended June 30, 2021. The Company incurred $0.9 million and $1.6 million of costs associated with its obligations under the arrangement with Jazz during the three and six months ended June 30, 2020, respectively. The costs are classified Sarepta license and option agreement Agreement summary On June 17, 2020, the Company entered into a two-year Under the terms of the Sarepta Research Agreement, the Company granted to Sarepta a non-exclusive, royalty-free, worldwide license, with a limited right to sublicense, to use certain intellectual property of the Company in the conduct of activities for which Sarepta is responsible under the Sarepta Research Agreement (the Research License). The Sarepta Research Agreement provides that the activities conducted by the parties will be performed in accordance with a research plan which sets forth the activities to be undertaken over the course of the Sarepta Research Agreement covering all targets included in the agreement (the Research Plan). The Company is responsible for the conduct of all activities to which it is assigned under the Research Plan. The Sarepta Research Agreement initially covers five agreed targets as selected by Sarepta at inception of the Sarepta Research Agreement (each, a Research Target). However, Sarepta has the right to replace up to two of the Research Targets with certain other agreed pre-named targets. To the extent a target is replaced, the original target is discontinued as a Research Target under the arrangement and the replacement target becomes a Research Target under the Sarepta Research Agreement. Pursuant to the terms of the Sarepta Research Agreement, the Company granted to Sarepta an option to obtain an exclusive, worldwide, sublicensable license to use certain intellectual property of the Company for the development, manufacturing and commercialization of exosome therapeutic candidates directed to one or more of the Research Targets (each, a Sarepta Option). Each of the licenses that would be issued upon exercise of a Sarepta Option cover the use of the Company’s intellectual property in the exploitation of therapeutics directed to a particular target (each, a Development and Commercialization License). Sarepta Options may be exercised on a Research Target-by-Research Target basis any time prior to completion of the research activities for the respective target, but not later than June 17, 2022 , subject to extension to December 17, 2022 (the Option Term). Following option exercise, the parties will execute a definitive license agreement that outlines the terms and conditions of the collaboration arrangement that would govern the further development and commercialization of exosome therapeutics directed to the subject target (the Collaboration Agreement), contingent on remittance of the option exercise fee. Under the terms of the Collaboration Agreement which would be entered into upon the exercise of a Sarepta Option, the Company would be responsible for the conduct of the associated preclinical development through the generation of a development candidate directed to the applicable target in accordance with a plan which sets forth the activities to be conducted with respect to each preclinical development program (each, a Preclinical Development Plan). Additionally, the Company is obligated to provide manufacturing and supply through the completion of Phase 2 clinical trials. The Company is entitled to receive reimbursement of costs incurred with respect to the activities performed in the execution of the Preclinical Development Plans and any manufacturing activities. Following the selection of a development candidate from a preclinical development program, Sarepta is responsible for any further development, regulatory matters and commercialization at its sole cost and expense. Under the terms of the Sarepta Research Agreement, the Company received up-front and non-refundable cash payments totaling $10.0 million, consisting of a $7.0 million up-front payment and a $3.0 million up-front research services prepayment. In addition, the Company is eligible for the reimbursement of costs incurred in the execution of the Research Plan. To the extent Sarepta exercises its option and the parties enter into a Collaboration Agreement with respect to any target included in the arrangement, Sarepta would be obligated to remit an option exercise payment of $12.5 million to the Company per target, up to a total of $62.5 million if all options are exercised. Conditional on the exercise of a Sarepta Option and execution of a Collaboration Agreement, the Company may earn potential development and regulatory milestones and t

Other Significant Agreements

Other Significant Agreements	6 Months Ended
	Jun. 30, 2021
Significant Agreements [Abstract]
Other Significant Agreements	12. Other significant agreements MDACC sponsored research agreement In November 2015, the Company entered into the MDACC Research Agreement with MDACC. Under the MDACC Research Agreement, the Company engaged MDACC to perform research and development services relating to its technology on patients suffering with cancer (the Research Program). MDACC was obligated to use reasonable efforts to conduct the Research Program and furnish the facilities necessary to carry out the program. The Research Program allowed for amendments from time to time during the term, by agreement of the parties, to modify the current Research Program or to add additional research projects for inclusion as part of the Research Program. The MDACC Research Agreement provided the Company with an option to negotiate a license to certain other technology derived from the program in the field of exosome technology. The term of the MDACC Research Agreement was originally scheduled to expire in November 2018. The MDACC Research Agreement was subsequently amended in February 2017 and in April 2018 to extend the term of the MDACC Research Agreement to February 2021 and to modify the payment terms of the MDACC Research Agreement. The MDACC Research Agreement was further amended in September 2019 to terminate the agreement, effective as of December 31, 2019. Under the terms of the MDACC Research Agreement, the Company was obligated to pay fixed tiered quarterly cash payments (the Quarterly Payments) and to issue a fixed number of shares of its Series A Preferred Stock or Series B Preferred Stock to MDACC in consideration for the research services. The Quarterly Payments consisted of the following: (i) direct expenses comprising $1.0 million payable to MDACC in the first year and $1.25 million payable in years two through five, and (ii) overhead charges of 25% of the direct expenses. In addition to the Quarterly Payments, the Company was also obligated to issue an aggregate of 200,000 shares of Series A Preferred Stock in the first year of the arrangement and 20,833 shares of Series B Preferred Stock, quarterly, in years two through five of the MDACC Research Agreement. The Company recognized the payments made to MDACC as research and development expense as incurred. The shares to be issued were expensed on the date the associated Quarterly Payment was due based on the estimated fair value of the underlying series of redeemable convertible preferred stock on such date. Subsequent to issuance, the Series A Preferred Stock and Series B Preferred Stock issued to MDACC was accounted for consistent with all other outstanding shares of the respective series of redeemable convertible preferred stock. As noted above, the agreement was terminated as of December 31, 2019. The Company made the final cash payment of $1.2 million and issued the remaining shares of Series B Preferred Stock to MDACC in January 2020. There was no related expense recognized during the year ended December 31, 2020. There are no further payments or share issuances owed to MDACC pursuant to the MDACC Research Agreement. All shares of Series A Preferred Stock and Series B Preferred converted into common stock in connection with the IPO. MDACC in-license agreement In November 2015, the Company entered into a Patent and Technology License Agreement with MDACC, as amended in April 2018 (the MDACC License Agreement). Pursuant to the MDACC License Agreement, the Company holds exclusive worldwide license rights to certain intellectual property relating to the use of exosomes for diagnostic and therapeutic applications and a non-exclusive worldwide license under certain related technologies, with the right to grant sublicenses. The Company also obtained the exclusive right of first negotiation, for a specified time period, for a license to certain of MDACC’s rights in future exosome technology. Under the terms of the MDACC License Agreement, the Company is responsible for all patent costs incurred by MDACC for the underlying licensed technology in excess of $1.5 million from the effective date of the agreement through February 1, 2021, and for all patent costs incurred or invoiced after this date. As of June 30, 2021, there was no remaining funding provided by MDACC for patent-related costs under the MDACC License Agreement. Pursuant to the MDACC License Agreement, the Company is also required to make future payments to MDACC upon the occurrence of events related to the development of products and upon the achievement of certain development and regulatory approval milestones up to an aggregate of $11.9 million, comprising up to $2.4 million for diagnostic products and up to $9.5 million for therapeutic products. The Company may at its discretion pay up to $4.4 million in such contingent payments in cash or through the issuance of equity in the form of redeemable convertible preferred stock or common stock, as applicable. Such payments will be expensed or capitalized based on the nature of the associated asset at the date the related contingency is resolved. In addition, the Company is obligated to pay certain payments upon the execution of sublicenses for qualifying products, as well as single digit percentage royalty payments on net sales from a licensed product. The MDACC License Agreement will continue until the last to occur of: (i) the expiration of all patents issued underlying the licenses conveyed, (ii) the cancellation, withdrawal or express abandonment of all patent rights underlying the licenses conveyed or (iii) the fifteenth anniversary of the effective date of the agreement. Upon expiration of the MDACC License Agreement, the licenses granted will automatically convert to a fully-paid irrevocable and perpetual license. The Company may terminate the license for convenience upon 180 days prior written notice to MDACC. The license automatically terminates upon the Company’s bankruptcy, if the Company challenges the validity or enforceability of any of the licensed patent rights, or if the Company fails to make a number of payments in a timely manner over a specified period of time. Additionally, MDACC may terminate the license for the Company’s breach subject to certain specified cure periods. As of June 30, 2021, no milestones had been achieved, nor had any royalties, sublicensing fees or other contingent payments been incurred under the MDACC License Agreement. The Company did not make any payments to MDACC for the three and six months ended June 30, 2021 and 2020 with respect to the MDACC License Agreement. Kayla Therapeutics S.A.S license agreement On November 6, 2018, the Company entered into a License Agreement with Kayla, pursuant to which it obtained a co-exclusive worldwide, sublicensable license under certain patent rights and to related know-how and methods to research, develop, manufacture and commercialize compounds and products covered by such patent rights in all diagnostic, prophylactic and therapeutic uses (the Kayla License Agreement). The foregoing license is co-exclusive with Kayla, but Kayla’s retained rights are subject to certain restrictions. During the first 6 years following the effective date of the Kayla License Agreement, Kayla and its affiliates may not research, develop, manufacture or commercialize anywhere in the world any product containing a small molecule STING agonist and an exosome. In addition, during the term of the Kayla License Agreement, Kayla and its affiliates may not grant a license to any third party under the licensed patent rights to, develop, manufacture or commercialize anywhere in the world a product containing certain STING compounds for therapeutic or veterinary purpose. The Kayla License Agreement also restricts the Company from developing any competing product containing a small molecule STING agonist and an exosome until the expiration of a non-compete period determined by the achievement of clinical milestones. Pursuant to ASC 730, the Company determined that the assets acquired represent in-process research and development with no alternative future use. Therefore, the value of the consideration given for the licenses was expensed to acquired in-process research and development in the period in which it was incurred. In consideration for entering into the Kayla License Agreement, the Company paid an up-front payment of $6.5 million in cash and issued 118,212 shares of common stock. The Company recorded an aggregate of $8.1 million to acquired in-process research and development expense during the year ended December 31, 2018 comprised of: (i) $6.5 million related to the cash payment and (ii) $1.6 million related to the issuance of its common stock based on the fair value of the Company’s common stock at the effective date of the Kayla License Agreement. The Company has certain diligence obligations under the Kayla License Agreement, which include using commercially reasonable efforts to develop, commercialize and market the products developed under the licensed patent rights, including using commercially reasonable efforts to initiate a cohort extension of a Phase 1/2 trial after obtaining IND approval. The Company is also obligated to pay up to $100.0 million in cash payments and up to $13.0 million payable in shares of the Company’s common stock upon the achievement of specified clinical and regulatory milestones, including approvals in the US, the EU and Japan. Such payments will be expensed or capitalized based on the nature of the associated asset at the date the related contingency is resolved. Additionally, the Company is obligated to pay to Kayla a percentage of the payments that the Company receives from sublicensees of the rights licensed to it by Kayla, excluding any royalties. This percentage varies from single digits to low double digits. The first milestone was achieved upon the first dosing of exoSTING to the first subject in the Company’s Phase 1/2 clinical trial in September 2020. Upon achievement of the milestone, the Company was obligated to make a nonrefundable payment of $15.0 million in cash and issue 177,318 shares of common stock to Kayla. The common stock was issued as of the date of dosing, and the cash payment of $15.0 million was paid as of December 31, 2020. As of June 30, 2021, no other milestones had been achieved. The Company is obligated to pay to Kayla tiered royalties ranging from low single-digits to mid-single-digits based on annual net sales by the Company, its affiliates and its sublicensees of licensed products. The royalty term is determined on a product-by-product and country-by-country basis and continues until the later of (i) the expiration of the last valid claim of the licensed patent rights that covers such product in such country, (ii) the loss or expiration of any period of marketing exclusivity for such product in such country, or (iii) ten years after the first commercial sale of such product in such country; provided that if the royalty is payable when no valid claim covers a given product in a given country, the royalty rate for sales of such product in such country is decreased. The Company may terminate the Kayla License Agreement on a licensed compound-by-licensed compound basis and on a region-by region basis for any reason upon 30 days prior written notice to Kayla. The Company or Kayla may terminate the Kayla License Agreement for the other’s material breach that remains uncured for 60 days after receiving notice thereof. As of June 30, 2021 , no royalties, or other contingent payments had been incurred under the Kayla License Agreement.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	13. Net loss per share Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share data): THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Numerator: Net loss $ (21,809 ) $ (15,913 ) $ (32,117 ) $ (38,415 ) Cumulative dividends on redeemable convertible preferred stock — (3,420 ) — (6,839 ) Net loss attributable to common stockholders $ (21,809 ) $ (19,333 ) $ (32,117 ) $ (45,254 ) Denominator: Weighted average common shares outstanding, basic and diluted 22,117,593 3,003,887 21,230,424 3,002,773 Net loss per share attributable to common stockholders, basic and diluted $ (0.99 ) $ (6.44 ) $ (1.51 ) $ (15.07 ) The following common stock equivalents, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have been anti-dilutive: THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Series A redeemable convertible preferred stock — 4,247,153 — 4,247,153 Series B redeemable convertible preferred stock — 2,633,138 — 2,633,138 Series C redeemable convertible preferred stock — 2,584,633 — 2,584,633 Outstanding stock options 5,166,657 4,212,125 5,166,657 4,212,125 5,166,657 13,677,049 5,166,657 13,677,049

Summary of Basis of Presentat_2

Summary of Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements that accompany these notes have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and applicable rules and regulations of the Securities and Exchange Commission (SEC) for interim financial reporting, consistent in all material respects with those applied in our Annual Report on Form 10-K for the year ended December 31, 2020 (2020 Annual Report). Any reference in these notes to applicable guidance is meant to refer to the authoritative accounting principles generally accepted in the United States as found in the Accounting Standard Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). Certain reclassifications were made to the 2020 financial statements to conform to the current period’s presentation. The reclassifications did not result in any changes to net loss or net stockholders’ deficit in either period presented. This report should be read in conjunction with the consolidated financial statements in our 2020 Annual Report. The consolidated financial statements include the Company and its subsidiaries. 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 reported amounts in the financial statements and accompanying notes. Actual results could materially differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. Significant estimates relied upon in preparing the consolidated financial statements include, among others: estimates related to revenue recognition, the valuation of common stock and stock-based compensation awards, leases, accrued expenses and income taxes.
Significant Accounting Policies	Significant Accounting Policies The significant accounting policies used in preparation of these condensed consolidated financial statements for the three and six months ended June 30, 2021 are consistent with those described in our 2020 Annual Report.
Recent Accounting Pronouncements	Recent accounting pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption. In December 2019, the FASB issued ASU No. 2019-12 Income Taxes (Topic 740)-Simplifying the Accounting for Income Taxes In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) .

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value on a Recurring Basis	The following tables present information about the Company’s assets measured at fair value on a recurring basis, and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): JUNE 30, 2021 TOTAL LEVEL 1 LEVEL 2 LEVEL 3 NOT SUBJECT TO LEVELING(1) Assets: Cash equivalents: Money market funds $ 72,501 $ — $ — $ — $ 72,501 $ 72,501 $ — $ — $ — $ 72,501 DECEMBER 31, 2020 TOTAL LEVEL 1 LEVEL 2 LEVEL 3 NOT SUBJECT TO LEVELING(1) Assets: Cash equivalents: Money market funds $ 81,601 $ — $ — $ — $ 81,601 $ 81,601 $ — $ — $ — $ 81,601 (1) Certain cash equivalents that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): JUNE 30, 2021 DECEMBER 31, 2020 Leasehold improvements $ 24,093 $ 23,949 Laboratory equipment 17,839 14,837 Furniture and fixtures 1,288 1,288 Computer equipment and software 159 159 Construction-in-process 133 1,667 $ 43,512 $ 41,900 Less: Accumulated depreciation and amortization (13,249 ) (10,490 ) Property and equipment, net $ 30,263 $ 31,410

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consists of the following (in thousands): JUNE 30, 2021 DECEMBER 31, 2020 Accrued employee compensation $ 5,049 $ 5,040 Accrued external research and development costs 1,104 1,475 Accrued professional services and consulting 931 902 Other expenditures 360 846 Accrued facilities costs 245 607 $ 7,689 $ 8,870

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Components of Operating Lease Costs	The components of operating lease costs were as follows (in thousands): FOR THE THREE MONTHS ENDED JUNE 30, FOR THE SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Operating lease costs $ 1,209 $ 1,209 $ 2,418 $ 2,421 Short-term lease costs 7 6 13 9 Variable lease costs 590 493 1,259 1,110 Sublease income (348 ) (158 ) (704 ) (158 ) $ 1,458 $ 1,550 $ 2,986 $ 3,382
Summary of Additional Lease Information	Additional lease information is summarized in the following table (in millions, except lease term and discount rate): SIX MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 Cash paid for amounts included in the measurement of operating lease liabilities $ 3.0 $ 3.1 Weighted-average remaining lease term - operating leases (years) 8.4 9.4 Weighted-average discount rate - operating leases 10.3 % 10.3 %
Schedule of Undiscounted Cash Flows Used in Calculating the Operating Lease Liabilities and Amounts to be Received under the Sublease	Undiscounted cash flows used in calculating the Company’s operating lease liabilities and amounts to be received under the sublease at 35 CambridgePark Drive as of June 30, 2021 are as follows (in thousands): Fiscal Year OPERATING LEASE PAYMENTS SUBLEASE RECEIPTS NET OPERATING LEASE PAYMENTS 2021 (remainder of the year) $ 2,980 $ 644 $ 2,336 2022 6,123 483 5,640 2023 6,307 6,307 2024 6,496 6,496 2025 6,691 6,691 Thereafter 28,287 28,287 Total undiscounted cash flows $ 56,884 $ 1,127 $ 55,757 Less: Amounts representing interest (19,245 ) Present value of lease liabilities $ 37,639

Indebtedness (Tables)

Indebtedness (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Schedule of Future Principal Payments	The future principal payments under the Loan Agreement are as follows as of June 30, 2021 (in thousands): Fiscal Year PRINCIPAL 2021 $ — 2022 1,910 2023 12,097 2024 10,993 $ 25,000

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Summary of Stock Option Activity	The following table summarizes the Company’s option activity during the six months ended June 30, 2021: NUMBER OF SHARES WEIGHTED AVERAGE EXERCISE PRICE PER SHARE WEIGHTED AVERAGE REMAINING CONTRACTUAL TERM AGGREGATE INTRINSIC VALUE (1) (In years) (In thousands) Outstanding as of December 31, 2020 4,543,318 $ 8.52 7.22 $ 108,048 Granted 1,140,400 24.77 Exercised (322,896 ) 8.58 Forfeited/Cancelled (194,165 ) 14.33 Outstanding as of June 30, 2021 5,166,657 11.88 7.02 41,555 Exercisable as of June 30, 2021 2,652,701 7.05 5.50 30,455 Vested and expected to vest as of June 30, 2021 5,166,657 11.88 7.02 41,555 (1) Aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock as of June 30, 2021 and December 31, 2020.
Schedule of Components and Classification of Stock-Based Compensation Expense	The following table presents the components and classification of stock-based compensation expense (in thousands): THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Research and development $ 1,221 $ 788 $ 2,279 $ 1,821 General and administrative 1,469 603 2,684 1,320 $ 2,690 $ 1,391 $ 4,963 $ 3,141 Employee $ 2,620 $ 1,329 $ 4,859 $ 2,879 Non-employee 70 62 104 262 $ 2,690 $ 1,391 $ 4,963 $ 3,141
Service-Based Awards
Summary of Key Assumptions Used for Stock Option Valuation	The key assumptions used in the Black-Scholes option pricing model on the date of grant for options with service-based vesting conditions were as follows, presented on a weighted average basis: THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Risk-free interest rate 1.08 % 0.46 % 0.77 % 1.38 % Expected term (in years) 6.12 6.25 6.21 6.25 Expected volatility 65.28 % 68.17 % 68.82 % 67.17 % Expected dividend yield 0.00 % 0.00 % 0.00 % 0.00 % Fair value per share of common stock $ 11.63 $ 6.27 $ 15.35 $ 6.31

Collaborative Arrangements (Tab

Collaborative Arrangements (Tables)	6 Months Ended
	Jun. 30, 2021
Summary of Total Consolidated Net Revenue from Strategic Collaborators	The following table summarizes our total consolidated net revenue from our strategic collaborators for the periods presented (in thousands): THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, Collaboration Revenue by Strategic Collaborator: 2021 2020 2021 2020 Jazz $ (511 ) $ 187 $ 11,107 $ 321 Sarepta 1,401 — 2,974 — Total collaboration revenue $ 890 $ 187 $ 14,081 $ 321
Schedule of Changes in Contract Assets and Liabilities	The following tables present changes in the Company’s contract assets and liabilities for the six months ended June 30, 2021 (in thousands): SIX MONTHS ENDED JUNE 30, 2021 BALANCE BEGINNING OF PERIOD ADDITIONS DEDUCTIONS BALANCE END OF PERIOD Contract assets: Account receivable (1) $ — $ 2,248 $ (842 ) $ 1,406 Contract liabilities: Deferred revenue $ 62,697 $ — $ (11,834 ) $ 50,863 (1) Included in prepaid expenses and other current assets as shown within the condensed consolidated balance sheets.
Schedule of Revenue Recognized	During the three and six months ended June 30, 2021 and 2020, the Company recognized the following revenue (in thousands): THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Revenue recognized in the period from: Amounts included in deferred revenue at the beginning of the period $ 890 $ 187 $ 14,081 $ 321
Jazz Pharmaceuticals Ireland Limited
Schedule of Transaction Price Allocated to Identified Performance Obligations	As a result, the transaction price associated with the remaining consideration was reallocated to the identified performance obligations as follows (in thousands): PERFORMANCE OBLIGATION ALLOCATED TRANSACTION PRICE License and Services Performance Obligation: Initial Collaboration Target #1 $ 12,717 License and Services Performance Obligation: Initial Collaboration Target #2 13,702 License and Services Performance Obligation: Initial Collaboration Target #3 10,866 License and Services Performance Obligation: Initial Collaboration Target #4 13,593 Additional Target or Program Material Right Performance Obligation 2,812 Replacement Target Material Right Performance Obligation 1,188 Backup Candidate Material Right Performance Obligation: Backup Candidate #1 47 Backup Candidate Material Right Performance Obligation: Backup Candidate #2 47 Transaction Price $ 54,972
Sarepta Therapeutics
Schedule of Transaction Price Allocated to Identified Performance Obligations	As a result, the transaction price was allocated to the identified performance obligations as follows: PERFORMANCE OBLIGATION ALLOCATED TRANSACTION PRICE Research License and Services Performance Obligation $ 11,000 Material Right Performance Obligation: Research Target #1 1,400 Material Right Performance Obligation: Research Target #2 1,400 Material Right Performance Obligation: Research Target #3 1,400 Material Right Performance Obligation: Research Target #4 1,400 Material Right Performance Obligation: Research Target #5 1,400 Transaction Price $ 18,000

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Basic and Diluted Net Loss Per Share Attributable to Common Stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share data): THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Numerator: Net loss $ (21,809 ) $ (15,913 ) $ (32,117 ) $ (38,415 ) Cumulative dividends on redeemable convertible preferred stock — (3,420 ) — (6,839 ) Net loss attributable to common stockholders $ (21,809 ) $ (19,333 ) $ (32,117 ) $ (45,254 ) Denominator: Weighted average common shares outstanding, basic and diluted 22,117,593 3,003,887 21,230,424 3,002,773 Net loss per share attributable to common stockholders, basic and diluted $ (0.99 ) $ (6.44 ) $ (1.51 ) $ (15.07 )
Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders	The following common stock equivalents, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have been anti-dilutive: THREE MONTHS ENDED JUNE 30, SIX MONTHS ENDED JUNE 30, 2021 2020 2021 2020 Series A redeemable convertible preferred stock — 4,247,153 — 4,247,153 Series B redeemable convertible preferred stock — 2,633,138 — 2,633,138 Series C redeemable convertible preferred stock — 2,584,633 — 2,584,633 Outstanding stock options 5,166,657 4,212,125 5,166,657 4,212,125 5,166,657 13,677,049 5,166,657 13,677,049

Nature of the Business - Additi

Nature of the Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 17, 2021	Oct. 16, 2020	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Entity date of incorporation			Jun. 12, 2015
Common stock, shares issued	3,162,500	5,500,000
Common stock, offering price	$ 21	$ 15
Proceeds from public offering of common stock, net of issuance costs	$ 61,700	$ 74,400	$ 61,681
Additional Common stock, shares issued	412,500
Issuance of redeemable convertible preferred stock			168,200
Net of issuance costs			24,600
Payments from its collaborations			66,000
Cash and cash equivalents			$ 113,700

Fair Value Measurements - Asset

Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - Recurring Basis - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Assets	$ 72,501	$ 81,601
Money Market Funds
Assets:
Cash equivalents	72,501	81,601
Not Subject to Netting
Assets:
Assets	72,501	81,601
Not Subject to Netting | Money Market Funds
Assets:
Cash equivalents	$ 72,501	$ 81,601

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Assets transfer, Level 1 to 2	$ 0	$ 0	$ 0	$ 0
Assets transfer, Level 2 to 1	0	0	0	0
Assets transfer, out of Level 3	0	0	0	0
Assets transfer, into Level 3	$ 0	$ 0	$ 0	$ 0

Investments - Additional Inform

Investments - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Investments Debt And Equity Securities [Abstract]
Available-for-sale investments	$ 0		$ 0
Realized gains or losses	$ 0	$ 0	$ 0	$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 43,512	$ 41,900
Less: Accumulated depreciation and amortization	(13,249)	(10,490)
Property and equipment, net	30,263	31,410
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	159	159
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	1,288	1,288
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	17,839	14,837
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	24,093	23,949
Construction-In-Process
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 133	$ 1,667

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 1,400	$ 900	$ 2,759	$ 1,970

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued employee compensation	$ 5,049	$ 5,040
Accrued external research and development costs	1,104	1,475
Accrued professional services and consulting	931	902
Other expenditures	360	846
Accrued facilities costs	245	607
Accrued expenses	$ 7,689	$ 8,870

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	Apr. 27, 2020USD ($)ft²	Aug. 26, 2019	Mar. 22, 2019USD ($)ft²	Mar. 05, 2019USD ($)ft²	Jun. 30, 2021USD ($)ft²	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)ft²Office	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Lessee Lease Description [Line Items]
Lease expiration year							2029
Number of location | Office							2
Sublease income					$ 348	$ 158	$ 704	$ 158
500 Technology Square
Lessee Lease Description [Line Items]
Area of lease | ft²					19,823		19,823
Lease, base rent per year							$ 1,500
Increase in annual rent percentage					2.50%		2.50%
Lease commencement date							Dec. 28, 2016
Original lease expiration date							Dec. 31, 2021
Accelerated lease expiration date		Feb. 28, 2020
4 Hartwell Place
Lessee Lease Description [Line Items]
Area of lease | ft²				18,707
Lease, base rent per year				$ 900
Increase in annual rent percentage				3.00%
Lease expiration month and year				2029-12
Lease commencement month and year				2019-07
Lessee, operating lease, existence of option to extend [true false]				true
Lessee, operating lease, option to extend							The Company has the option to extend the lease twice, each for a 5-year period, on the same terms and conditions as the current lease, subject to a change in base rent based on market rates.
Lessee, operating lease, option to extend term				5 years
Tenant improvement allowance, received					$ 1,300		$ 1,300
4 Hartwell Place | Maximum
Lessee Lease Description [Line Items]
Tenant improvement allowance				$ 1,300
4 Hartwell Place | Letter of Credit
Lessee Lease Description [Line Items]
Security deposit					400		$ 400		$ 400
35 Cambridge Park Drive
Lessee Lease Description [Line Items]
Area of lease | ft²			68,258
Lease, base rent per year			$ 4,900
Increase in annual rent percentage			3.00%
Lease commencement date			Mar. 26, 2019
Original lease expiration date			Nov. 30, 2029
Lessee, operating lease, existence of option to extend [true false]			true
Lessee, operating lease, option to extend							The Company has the option to extend the lease for a 10-year period on the same terms and conditions as the current lease, subject to a change in base rent based on market rates.
Lessee, operating lease, option to extend term			10 years
Tenant improvement allowance			$ 12,300
Tenant improvement allowance, received									12,300
Construction oversight fee			2.00%
Area of space for sublease | ft²	23,280
Sublease payments to be received annually	$ 1,300
Sublease income, increase in annual percentage	3.00%
Sublease commencement date	May 18, 2020
Sublease expiration month and year	2022-05
Lessee, operating sublease, existence of option to extend	true
Lessee, operating sublease, option to extend							The sublessee has the option to extend the sublease for a one-year period on the same terms and conditions as the current sublease, subject to a change in base rent based on the greater of (i) an increase of 3% of the annual rent owed by the sublessee in year two, and (ii) market rent for the subleased premises.
Lessee, operating sublease, option to extend term	1 year
35 Cambridge Park Drive | Other Income
Lessee Lease Description [Line Items]
Sublease income					300	$ 200	$ 700	$ 200
35 Cambridge Park Drive | Letter of Credit
Lessee Lease Description [Line Items]
Security deposit					$ 3,700		$ 3,700		$ 3,700
Security deposit in connection with sublease	$ 300

Leases - Components of Operatin

Leases - Components of Operating Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Lease Cost [Abstract]
Operating lease costs	$ 1,209	$ 1,209	$ 2,418	$ 2,421
Short-term lease costs	7	6	13	9
Variable lease costs	590	493	1,259	1,110
Sublease income	(348)	(158)	(704)	(158)
Lease, cost	$ 1,458	$ 1,550	$ 2,986	$ 3,382

Leases - Summary of Additional

Leases - Summary of Additional Lease Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 3	$ 3.1
Weighted-average remaining lease term - operating leases (years)	8 years 4 months 24 days	9 years 4 months 24 days
Weighted-average discount rate - operating leases	10.30%	10.30%

Leases - Schedule of Undiscount

Leases - Schedule of Undiscounted Cash Flows Used in Calculating the Operating Lease Liabilities and Amounts to be Received under the Sublease (Details) $ in Thousands	Jun. 30, 2021USD ($)
Leases [Abstract]
Operating Lease payments, 2021 (remainder of the year)	$ 2,980
Operating Lease Payments, 2022	6,123
Operating Lease Payments, 2023	6,307
Operating Lease Payments, 2024	6,496
Operating Lease Payments, 2025	6,691
Operating Lease Payments, Thereafter	28,287
Operating Lease Payments, Total undiscounted cash flows	56,884
Operating Lease Payments, Less: Amounts representing interest	(19,245)
Operating Lease Payments, Present value of lease liabilities	37,639
Sublease Receipts, 2021 (remainder of the year)	644
Sublease Receipts, 2022	483
Sublease Receipts, Total undiscounted cash flows	1,127
Net Operating Lease Payments, 2021 (remainder of the year)	2,336
Net Operating Lease Payments, 2022	5,640
Net Operating Lease Payments, 2023	6,307
Net Operating Lease Payments, 2024	6,496
Net Operating Lease Payments, 2025	6,691
Net Operating Lease Payments, Thereafter	28,287
Net Operating Lease Payments, Total undiscounted cash flows	$ 55,757

Commitments and contingencies -

Commitments and contingencies - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Dec. 31, 2019	Sep. 30, 2020	Dec. 31, 2020
License Agreement | Kayla Therapeutics S.A.S
Commitments And Contingencies [Line Items]
Nonrefundable payment in cash		$ 15
Nonrefundable payment in shares of common stock		177,318
Nonrefundable cash payment paid			$ 15
MDAndersonCancerCenterMember | Research Agreement | Series B Redeemable Convertible Preferred Stock
Commitments And Contingencies [Line Items]
Issuance of common stock, net of issuance costs	$ 1.2

Indebtedness - Additional Infor

Indebtedness - Additional Information (Details)	Jul. 24, 2020USD ($)	Sep. 30, 2019USD ($)Tranche	Jun. 30, 2021USD ($)	Mar. 31, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Interest expense			$ 704,000		$ 294,000	$ 1,401,000	$ 589,000
Loan Agreement | Term Loan | Hercules
Debt Instrument [Line Items]
Number of tranches | Tranche		4
Debt instrument, interest rate terms						Advances under the Term Loan Facility bear interest at a rate equal to the greater of (i) 9.00% plus the Prime Rate (as reported in The Wall Street Journal) less 5.25%, and (ii) 9.00%.
Interest rate		9.00%
Debt instrument, interest only payment end date		Nov. 1, 2022
Debt instrument repayment end date		Oct. 1, 2024
Debt instrument, end of term payment charge on funded amount percentage		5.50%
Debt instrument, covenants, obligated to maintain account cover amount percentage		110.00%
Loan carrying value	$ 15,000,000	$ 9,500,000	25,200,000			$ 25,200,000		$ 25,000,000
Interest expense			700,000		$ 300,000	1,400,000	$ 600,000
Loan Agreement | Term Loan | Hercules | Prime Rate
Debt Instrument [Line Items]
Variable interest rate		9.00%
Reduced from variable interest rate		5.25%
Loan Agreement | Term Loan | Hercules | Maximum
Debt Instrument [Line Items]
Aggregate principal amount		$ 75,000,000
Loan Agreement | Term Loan | Hercules | Second Tranche
Debt Instrument [Line Items]
Aggregate principal amount				$ 10,000,000
Borrowing capacity term				second tranche was available under the Term Loan Facility, which allowed the Company to borrow an additional amount up to $10.0 million through March 31, 2021. The Company did not elect to borrow against the second $10.0 million tranche.
Interest rate		1.50%
Loan Agreement | Term Loan | Hercules | Second Tranche | Maximum
Debt Instrument [Line Items]
Aggregate principal amount		$ 10,000,000
Loan Agreement | Term Loan | Hercules | First Tranche
Debt Instrument [Line Items]
Advanced amount under term loan	$ 15,000,000	$ 10,000,000
Interest rate		2.00%
Amount payable upon any prepayment or repayment		$ 1,400,000
Loan Agreement | Term Loan | Hercules | Third Tranche
Debt Instrument [Line Items]
Aggregate principal amount			$ 10,000,000			$ 10,000,000
Borrowing capacity term						third tranche was available under the Term Loan Facility, which allowed the Company to borrow an additional amount up to $10.0 million through June 30, 2021. The Company did not elect to borrow against the third $10.0 million tranche.
Interest rate		1.00%
Loan Agreement | Term Loan | Hercules | Third Tranche | Maximum
Debt Instrument [Line Items]
Aggregate principal amount		$ 10,000,000
Loan Agreement | Term Loan | Hercules | Fourth Tranche
Debt Instrument [Line Items]
Borrowing capacity term						fourth tranche, which allows the Company to borrow an additional amount up to $30.0 million, will be available upon Hercules’ approval on or prior to December 15, 2021.
Loan Agreement | Term Loan | Hercules | Fourth Tranche | Maximum
Debt Instrument [Line Items]
Aggregate principal amount		$ 30,000,000

Indebtedness - Schedule of Futu

Indebtedness - Schedule of Future Principal Payments (Details) - Loan Agreement $ in Thousands	Jun. 30, 2021USD ($)
Debt Instrument [Line Items]
2022	$ 1,910
2023	12,097
2024	10,993
Long-term debt	$ 25,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jan. 01, 2021	Oct. 12, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based awards, vesting conditions			As of June 30, 2021, the Company has granted service-based awards, which vest over a defined period of service, and performance-based and market-based awards, which vest upon the achievement of defined conditions. Service-based awards generally vest over a four-year period, with the first 25% vesting following twelve months of continued employment or service, and the remainder vesting in twelve quarterly installments over the following three years.
Share-based awards, vesting period			4 years
Shares of common stock reserved for future issuance						834,720
Annual increased percentage on outstanding common stock reserved						0.50%
Number of shares available for future issuance						208,680
Stock option, expiration period			10 years
Treasury stock, shares	0		0
Weighted average grant date fair value per share of options granted	$ 11.63	$ 6.27	$ 15.35	$ 6.31
Aggregate intrinsic value of stock options exercised	$ 3,300,000		$ 4,300,000
Shares granted			1,140,400
Stock-based compensation expense	2,690,000	$ 1,391,000	$ 4,963,000	$ 3,141,000
Total unrecognized compensation expense related to option awards	$ 25,300,000		$ 25,300,000
Weighted-average period of unrecognized compensation expense related to option awards			3 years 25 days
Performance-Based Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted	0	0	0	0
Stock-based compensation expense	$ 0	$ 0		$ 0
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value of stock options exercised		$ 100,000		$ 100,000
Maximum | Performance-Based Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense			$ 100,000
2020 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for future issuance						1,043,402
Additional shares of common stock reserved for future issuance					938,384
Number of shares available for future issuance	1,281,040		1,281,040
2020 Stock Option and Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Annual increased percentage on outstanding common stock reserved						5.00%
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for future issuance	0		0
Tranche 1
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based awards, vesting period			12 months
Share-based awards, vesting percentage			25.00%
Tranche 2
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based awards, vesting period			3 years
Share-based awards, vesting description			twelve quarterly installments

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Number of Shares
Outstanding | shares	4,543,318
Granted | shares	1,140,400
Exercised | shares	(322,896)
Forfeited/Cancelled | shares	(194,165)
Outstanding | shares	5,166,657	4,543,318
Exercisable | shares	2,652,701
Vested and expected to vest | shares	5,166,657
Weighted Average Exercise Price Per Share
Outstanding | $ / shares	$ 8.52
Granted | $ / shares	24.77
Exercised | $ / shares	8.58
Forfeited/Cancelled | $ / shares	14.33
Outstanding | $ / shares	11.88	$ 8.52
Exercisable | $ / shares	7.05
Vested and expected to vest | $ / shares	$ 11.88
Weighted Average Remaining Contractual Term
Outstanding	7 years 7 days	7 years 2 months 19 days
Exercisable	5 years 6 months
Vested and expected to vest	7 years 7 days
Aggregate Intrinsic Value
Outstanding | $	$ 41,555	$ 108,048
Exercisable | $	30,455
Vested and expected to vest | $	$ 41,555

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Assumptions used in Black-Scholes Option Pricing Model (Details) - Service-Based Awards - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	1.08%	0.46%	0.77%	1.38%
Expected term (in years)	6 years 1 month 13 days	6 years 3 months	6 years 2 months 15 days	6 years 3 months
Expected volatility	65.28%	68.17%	68.82%	67.17%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Fair value per share of common stock	$ 11.63	$ 6.27	$ 15.35	$ 6.31

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Components and Classification of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2,690	$ 1,391	$ 4,963	$ 3,141
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1,221	788	2,279	1,821
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1,469	603	2,684	1,320
Employee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	2,620	1,329	4,859	2,879
Non-employee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 70	$ 62	$ 104	$ 262

Collaboration Agreements - Summ

Collaboration Agreements - Summary of Total Consolidated Net Revenue from Strategic Collaborators (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Collaboration Agreements [Line Items]
Total collaboration revenue	$ 890	$ 187	$ 14,081	$ 321
Jazz
Collaboration Agreements [Line Items]
Total collaboration revenue	(511)	$ 187	11,107	$ 321
Sarepta
Collaboration Agreements [Line Items]
Total collaboration revenue	$ 1,401		$ 2,974

Collaboration Agreements - Sche

Collaboration Agreements - Schedule of Changes in Contract Assets and Liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Contract assets:
Accounts receivable, ADDITIONS	$ 2,248	[1]
Accounts receivable, DEDUCTIONS	(842)	[1]
Accounts receivable, BALANCE END OF PERIOD	1,406	[1]
Contract liabilities:
Deferred revenue, BALANCE BEGINNING OF PERIOD	62,697
Deferred revenue, DEDUCTIONS	(11,834)
Deferred revenue, BALANCE END OF PERIOD	$ 50,863
[1]	Included in prepaid expenses and other current assets as shown within the condensed consolidated balance sheets.

Collaboration Agreements - Sc_2

Collaboration Agreements - Schedule of Revenue Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Collaboration Agreements [Abstract]
Amounts included in deferred revenue at the beginning of the period	$ 890	$ 187	$ 14,081	$ 321

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details)	Apr. 02, 2021USD ($)	Jun. 17, 2020USD ($)Target	Jan. 02, 2019USD ($)TargetCandidateObligation	Apr. 30, 2021Target	Jun. 30, 2021USD ($)	Mar. 31, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 23, 2020USD ($)
Collaboration Agreements [Line Items]
Number of performance obligations | Obligation			8
Total collaboration revenue					$ 890,000		$ 187,000	$ 14,081,000	$ 321,000
Deferred revenue					50,863,000			50,863,000
Up-front and non-refundable cash payments received								66,000,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited
Collaboration Agreements [Line Items]
Number of oncogene targets | Target			5
Number of targets | Target			4
Number of oncogene targets discontinue work | Target				1
Number of clinical trial candidates | Candidate			2
Number of remaining candidates | Candidate			3
Additional milestone payment related to regulatory approval of product			$ 20,000,000
Up-front payment			56,000,000
Preclinical development milestone payments eligible to receive			20,000,000
Collaboration target payment receivable due upon second initiation			10,000,000
Milestone payments eligible to receive			$ 200,000,000
Notice period for termination of agreement			180 days
Collaboration arrangement transaction price measured based on non-refundable and non creditable up-front payment								56,000,000
Variable consideration payable included in transaction price at inception								0
Remaining consideration comprised solely of transaction price											$ 55,000,000
Changes in estimate of variable consideration								0
Remaining deferred revenue recognized						$ 10,900,000
Total collaboration revenue	$ 2,800				500,000		200,000	11,100,000	300,000
Deferred revenue					43,900,000			43,900,000		$ 55,000,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Research and Development
Collaboration Agreements [Line Items]
Cost associated with obligations under arrangement					700,000		900,000	1,300,000	1,600,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Development and Commercialization License and Associated Research Services | ASU 2014-09
Collaboration Agreements [Line Items]
Option to include additional target additional cost			$ 0
Replacement target additional cost			0
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Research Services | ASU 2014-09
Collaboration Agreements [Line Items]
Option to request additional research program additional cost			0
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | Non-GLP Toxicology Studies | ASU 2014-09
Collaboration Agreements [Line Items]
Per backup development candidate cost upon exercise			$ 0
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | License and Services
Collaboration Agreements [Line Items]
Performance obligation unsatisfied					42,800,000			42,800,000
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited | All Other Services
Collaboration Agreements [Line Items]
Performance obligation unsatisfied					1,300,000			1,300,000
Sarepta Research Agreement
Collaboration Agreements [Line Items]
Up-front payment		$ 7,000,000
Milestone payments eligible to receive		$ 192,500,000
Total collaboration revenue					1,400,000		0	3,000,000	0
Deferred revenue					7,000,000			7,000,000		$ 7,700,000
Research agreement period		2 years
Number of agreed targets | Target		5
Term of option exercise		Jun. 17, 2022
Extended term of option exercise		Dec. 17, 2022
Up-front and non-refundable cash payments received		$ 10,000,000
Up-front research services prepayment		3,000,000
Collaboration arrangement obligated to remit option exercise payment		12,500,000
Collaboration arrangement obligated options exercised		$ 62,500,000
Additional term of agreement		2 years
Material rights outstanding either exercised or expired					0			0
Sarepta Research Agreement | Research and Development
Collaboration Agreements [Line Items]
Cost associated with obligations under arrangement					1,400,000		$ 0	3,000,000	$ 0
Sarepta Research Agreement | ASU 2014-09
Collaboration Agreements [Line Items]
Up-front payment		$ 7,000,000
Up-front research services prepayment		3,000,000
Aggregate transaction price		18,000,000
Estimation of cost reimbursements		$ 8,000,000
Sarepta Research Agreement | All Other Services
Collaboration Agreements [Line Items]
Performance obligation unsatisfied					7,000,000			7,000,000
Sarepta Research Agreement | Research License and Services
Collaboration Agreements [Line Items]
Performance obligation unsatisfied					$ 5,800,000			$ 5,800,000

Collaboration Agreements - Sc_3

Collaboration Agreements - Schedule of Transaction Price Allocated to Identified Performance Obligation (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Jun. 17, 2020
Collaboration and License Agreement | Jazz Pharmaceuticals Ireland Limited
Collaboration Agreements [Line Items]
License and Services Performance Obligation: Initial Collaboration Target #1	$ 12,717
License and Services Performance Obligation: Initial Collaboration Target #2	13,702
License and Services Performance Obligation: Initial Collaboration Target #3	10,866
License and Services Performance Obligation: Initial Collaboration Target #4	13,593
Additional Target or Program Material Right Performance Obligation	2,812
Replacement Target Material Right Performance Obligation	1,188
Backup Candidate Material Right Performance Obligation: Backup Candidate #1	47
Backup Candidate Material Right Performance Obligation: Backup Candidate #2	47
Transaction Price	$ 54,972
Sarepta Research Agreement
Collaboration Agreements [Line Items]
Transaction Price		$ 18,000
Research License and Services Performance Obligation		11,000
Material Right Performance Obligation: Research Target #1		1,400
Material Right Performance Obligation: Research Target #2		1,400
Material Right Performance Obligation: Research Target #3		1,400
Material Right Performance Obligation: Research Target #4		1,400
Material Right Performance Obligation: Research Target #5		$ 1,400

Other Significant Agreements -

Other Significant Agreements - Additional Information (Details)

Feb. 17, 2021shares

Oct. 16, 2020shares

Nov. 06, 2018USD ($)shares

Jan. 31, 2021USD ($)shares

Nov. 30, 2015USD ($)shares

Jun. 30, 2021USD ($)

Jun. 30, 2020USD ($)

Jun. 30, 2021USD ($)Milestone

Jun. 30, 2020USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2018USD ($)

Feb. 01, 2021USD ($)

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Research and development

$ 15,419,000

$ 11,622,000

$ 31,969,000

$ 30,013,000

Stock issued, new issues | shares

3,162,500

5,500,000

MDAndersonCancerCenterMember | Patent and Technology License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Remaining funding amount for patent-related costs under license agreement

0

$ 0

Number of days of prior written notice to terminate agreement

180 days

Number of milestones achieved | Milestone

0

Payments with respect to license agreement

0

$ 0

$ 0

$ 0

MDAndersonCancerCenterMember | Patent and Technology License Agreement | Minimum [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Patent costs

$ 1,500,000

MDAndersonCancerCenterMember | Patent and Technology License Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Contingent future payments upon achievement of certain development and regulatory approval milestones

$ 11,900,000

Contingent payments in cash or through issuance of equity

4,400,000

MDAndersonCancerCenterMember | Patent and Technology License Agreement | Maximum | Diagnostic Products

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Contingent future payments upon achievement of certain development and regulatory approval milestones

2,400,000

MDAndersonCancerCenterMember | Patent and Technology License Agreement | Maximum | Therapeutic Products

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Contingent future payments upon achievement of certain development and regulatory approval milestones

9,500,000

MDAndersonCancerCenterMember | Research Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Research agreement extension of expiration year and month

2021-02

Research and development expense payment due year one

1,000,000

Research and development expense payment due year two through five

$ 1,250,000

Percentage of overhead charges on direct expenses

25.00%

Preferred stock shares issuable in year one under research agreement | shares

200,000

Preferred stock shares issuable in year two through five under research agreement | shares

20,833

Research agreement expiration date

Dec. 31, 2019

Research and development

$ 1,200,000

Research and development expense payment due

$ 0

Preferred stock shares issuable under research agreement | shares

0

MDAndersonCancerCenterMember | Research Agreement | Series B Redeemable Convertible Preferred Stock

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Stock issued, new issues | shares

1,200,000

Expense recognized to estimate fair value of shares

$ 0

Kayla Therapeutics S.A.S | Kayla License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Number of days of prior written notice to terminate agreement

30 days

Payments with respect to license agreement

$ 0

$ 0

Upfront payment paid in cash

$ 6,500,000

Acquired in-process research and development expense

$ 8,100,000

Cash payment related to acquired in-process research and development

6,500,000

Royalty term determination period after first commercial sale of such product in such country

10 years

Number of days of notice to terminate agreement upon material breach

60 days

Kayla Therapeutics S.A.S | Kayla License Agreement | Phase 1/2 Clinical Trial

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Number of milestones achieved | Milestone

0

Non-refundable milestone payment in cash

$ 15,000,000

Non-refundable milestone payment in common stock | shares

177,318

Milestone payment

$ 15,000,000

Kayla Therapeutics S.A.S | Kayla License Agreement | Common Stock

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Shares issued in consideration for license agreement | shares

118,212

Value of shares issued, acquired in process research and development

$ 1,600,000

Kayla Therapeutics S.A.S | Kayla License Agreement | Maximum | Phase 1/2 Clinical Trial

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Obligated to make cash payments upon achievement of clinical and regulatory milestones

$ 100,000,000

Value of common stock shares payable upon achievement of clinical and regulatory milestones

$ 13,000,000

Net Loss Per Share - Basic and

Net Loss Per Share - Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss	$ (21,809)	$ (15,913)	$ (32,117)	$ (38,415)
Cumulative dividends on redeemable convertible preferred stock		(3,420)		(6,839)
Net loss attributable to common stockholders	$ (21,809)	$ (19,333)	$ (32,117)	$ (45,254)
Denominator:
Weighted average common shares outstanding, basic and diluted	22,117,593	3,003,887	21,230,424	3,002,773
Net loss per share attributable to common stockholders, basic and diluted	$ (0.99)	$ (6.44)	$ (1.51)	$ (15.07)

Net Loss Per Share - Anti-dilut

Net Loss Per Share - Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share attributable to common stockholders	5,166,657	13,677,049	5,166,657	13,677,049
Series A Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share attributable to common stockholders		4,247,153		4,247,153
Series B Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share attributable to common stockholders		2,633,138		2,633,138
Series C Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share attributable to common stockholders		2,584,633		2,584,633
Outstanding Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share attributable to common stockholders	5,166,657	4,212,125	5,166,657	4,212,125