C4 Therapeutics (CCCC) 10-K 11 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 01, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	CCCC
Entity Registrant Name	C4 Therapeutics, Inc.
Entity Central Index Key	0001662579
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		43,119,385
Entity Public Float			$ 0
Entity File Number	001-39567
Entity Tax Identification Number	47-5617627
Entity Address, Address Line One	490 Arsenal Way
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	Watertown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02472
City Area Code	617
Local Phone Number	231-0700
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s definitive proxy statement for its 2021 Annual Meeting of Stockholders to be filed pursuant to Regulation 14A within 120 days of the end of the registrant’s fiscal year ended December 31, 2020 are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 181,727	$ 90,549
Marketable securities	189,962
Accounts receivable	4,484	4,623
Prepaid expenses and other current assets	4,836	1,595
Total current assets	381,009	96,767
Property and equipment, net	3,323	4,463
Right-of-use asset	13,229	14,453
Restricted cash	2,577	2,577
Total assets	400,138	118,260
Current liabilities:
Accounts payable	5,683	5,385
Accrued expenses and other current liabilities	9,524	6,671
Deferred revenue, current	27,603	20,705
Operating lease liability, current	1,042	880
Total current liabilities	43,852	33,641
Deferred revenue, net of current	53,617	72,718
Operating lease liability, net of current	11,826	12,869
Long-term debt—related party	10,052
Total liabilities	119,347	119,228
Commitments and contingencies (See Note 6 and Note 9)
Redeemable convertible preferred stock (See Note 10)		110,995
Stockholders’ equity (deficit):
Preferred stock, par value of $0.0001 per share; 10,000,000 and no shares authorized, and no shares issued or outstanding as of December 31, 2020 and 2019, respectively
Common stock, par value of $0.0001 per share; 150,000,000 and 21,343,452 shares authorized, and 43,059,632 and 1,426,641 shares issued and outstanding as of December 31, 2020 and 2019, respectively	4
Additional paid-in capital	464,597	5,525
Accumulated other comprehensive loss	13
Accumulated deficit	(183,823)	(117,488)
Total stockholders’ equity (deficit)	280,791	(111,963)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	$ 400,138	$ 118,260

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value per share	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	21,343,452
Common stock, shares issued	43,059,632	1,426,641
Common stock, shares outstanding	43,059,632	1,426,641

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue from collaboration agreements	$ 33,195	$ 21,381
Operating expenses:
Research and development	78,440	48,059
General and administrative	15,204	8,774
Total operating expenses	93,644	56,833
Operating loss	(60,449)	(35,452)
Other (expense) income
Change in fair value of warrant liability—related party	(5,676)
Interest expense and amortization of long-term debt—related party	(1,229)
Interest and other income, net	393	2,157
Total other (expense) income	(6,512)	2,157
Loss before income taxes	(66,961)	(33,295)
Income tax benefit (expense)	626	(804)
Net loss	(66,335)	(34,099)
Unrealized gain on marketable securities	13
Comprehensive loss	(66,322)	(34,099)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(66,335)	(34,099)
Accrual of preferred stock dividends		(8,468)
Net loss attributable to common stockholders—basic and diluted	$ (66,335)	$ (42,567)
Net loss per share attributable to common stockholders—basic and diluted	$ (5.83)	$ (31.03)
Weighted-average common stock outstanding—basic and diluted	11,370,328	1,371,905

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Redeemable Convertible Preferred Stock
Beginning balance at Dec. 31, 2018	$ (79,750)		$ 3,639		$ (83,389)
Redeemable convertible preferred stock, Beginning balance, Shares at Dec. 31, 2018						113,145,900
Redeemable convertible preferred stock, Beginning balance at Dec. 31, 2018						$ 110,995
Beginning balance, Shares at Dec. 31, 2018		1,338,956
Exercise of stock options	274		274
Exercise of stock options, Shares		93,797
Stock-based compensation	1,642		1,642
Repurchase of common stock	(30)		(30)
Repurchase of common stock, Shares		(6,112)
Net loss	(34,099)				(34,099)
Ending balance at Dec. 31, 2019	$ (111,963)		5,525		(117,488)
Redeemable convertible preferred stock, Ending balance, Shares at Dec. 31, 2019	113,145,900					113,145,900
Redeemable convertible preferred stock, Ending balance at Dec. 31, 2019	$ 110,995					$ 110,995
Ending balance, Shares at Dec. 31, 2019		1,426,641
Issuance of Series B redeemable convertible preferred stock, net of issuance costs of $4.5 million						$ 145,525
Issuance of Series B redeemable convertible preferred stock, net of issuance costs of $4.5 million, Shares						142,857,142
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering	256,520	$ 3	256,517			$ (256,520)
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering, Shares		30,355,379				(256,003,042)
Reclassification of warrant liability to equity	8,001		8,001
Issuance of common stock upon closing of initial public offering, net of issuance costs of $18.6 million	191,173	$ 1	191,172
Issuance of common stock upon closing of initial public offering, net of issuance costs of $18.6 million, Shares		11,040,000
Exercise of stock options	887		887
Exercise of stock options, Shares		281,584
Stock-based compensation	3,432		3,432
Repurchase of common stock	(210)		(210)
Repurchase of common stock, Shares		(43,972)
Vested Stock Option Settlement	(727)		(727)
Unrealized gain on investments	13			$ 13
Net loss	(66,335)				(66,335)
Ending balance at Dec. 31, 2020	$ 280,791	$ 4	$ 464,597	$ 13	$ (183,823)
Ending balance, Shares at Dec. 31, 2020		43,059,632

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Series B Redeemable Convertible Preferred Stock
Issuance costs	$ 4.5
Initial Public Offering
Issuance costs	$ 18.6

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows used in operating activities:
Net loss	$ (66,335)	$ (34,099)
Adjustments to reconcile net loss to cash (used in) provided by operating activities:
Depreciation and amortization	1,617	1,595
Stock-based compensation expense	3,432	1,642
Gain on disposal of fixed assets		16
Accretion of (premium) discount on investments	(95)	334
Reduction in carrying amount of right-of-use assets	1,224	1,144
Amortization of debt discount	409
Change in fair value of warrant liability	5,676
Changes in operating assets and liabilities:
Accounts receivable	139	81,815
Prepaid expenses and other current assets	(3,257)	(814)
Accounts payable	467	4,231
Accrued expenses and other liabilities	2,558	3,719
Operating lease liability	(881)	(734)
Deferred revenue	(12,203)	(3,235)
Net cash (used in) provided by operating activities	(67,249)	55,614
Cash flows used in investing activities:
Proceeds received from maturities of marketable securities	104,000	78,666
Purchase of marketable securities	(293,855)	(79,000)
Purchases of property and equipment	(650)	(1,349)
Proceeds from sale of property and equipment		63
Net cash used in investing activities	(190,505)	(1,620)
Cash flows provided by financing activities:
Proceeds from issuance of Series B shares, net of issuance costs of $4.5 million	145,525
Proceeds from long-term debt and warrant, net of issuance costs of $0.5 million	11,973
Proceeds from initial public offering, net of underwriting discount of $14.7 million	195,074
Payment of initial public offering costs	(3,606)
Proceeds from exercises of stock options	887	274
Repurchase of common stock	(194)	(30)
Vested stock option settlement	(727)
Net cash provided by financing activities	348,932	244
Net change in cash, cash equivalents and restricted cash	91,178	54,238
Cash, cash equivalents and restricted cash at beginning of period	93,126	38,888
Cash, cash equivalents and restricted cash at end of period	184,304	93,126
Reconciliation of cash, cash equivalents and restricted cash:
Cash, cash equivalents and restricted cash at end of period	184,304	93,126
Less: restricted cash	(2,577)	(2,577)
Cash and cash equivalents at end of the year	181,727	90,549
Supplemental disclosure of cash flow information:
Cash paid for interest	820
Cash paid for taxes	143	1,088
Supplemental disclosures of non-cash investing and financing activities:
Conversion of redeemable convertible preferred stock to common stock upon closing of the initial public offering	256,520
Reclassification of warrant liability to equity	8,001
Initial public offering costs in accounts payable and accrued expenses	$ 296
Capital expenditures in accounts payable		172
Stock option repurchases included in accrued expenses		$ 16

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Statement Of Cash Flows [Abstract]
Stock issuance costs	$ 4.5
Long-term debt and warrant, net of issuance costs	0.5
Underwriting discount	$ 14.7

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	Note 1. Nature of the business and basis of presentation C4 Therapeutics, Inc., or, together with its subsidiary, the Company, is a biopharmaceutical company focused on harnessing the body’s natural regulation of protein levels to develop novel therapeutic candidates to target and eliminate disease-causing proteins for the treatment of cancer, neurodegenerative conditions and other diseases. The Company was incorporated in Delaware on October 7, 2015 and has its principal office in Watertown, Massachusetts. Liquidity and capital resources Since its inception, the Company’s primary activities have been focused around research and development activities, building the Company’s intellectual property, recruiting personnel and raising capital to support these activities. To date, the Company has funded its operations primarily with proceeds received from the sales of redeemable convertible preferred stock, sales of common stock through an initial public offering, through its collaboration agreements, and debt financing. The Company has incurred recurring losses since its inception, including net losses of $66.3 million and $34.1 million for the years ended December 31, 2020 and 2019, respectively. In addition, as of December 31, 2020, the Company had an accumulated deficit of $183.8 million. To date, the Company has not generated any revenue from product sales as none of its product candidates has been approved for commercialization. The Company expects to continue to generate operating losses for the foreseeable future. On October 6, 2020, the Company completed its initial public offering, or the IPO, at which time the Company issued 11,040,000 shares of its common stock at a price to the public of $19.00 per share, which number includes 1,440,000 shares of common stock that were issued to the underwriters for the IPO when they exercised in full their overallotment option. Upon the closing of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock automatically converted into 30,355,379 shares of common stock. Net proceeds from the IPO, including the exercise in full of the underwriters’ option to purchase additional shares, were $191.2 million, after deducting underwriting discounts and commissions of $14.7 million and expenses of $3.9 million. The Company expects that its cash, cash equivalents and marketable securities of $371.7 million as of December 31, 2020 will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these consolidated financial statements. Reverse Stock Split On September 25, 2020, the Company effected a one-for-8.4335 reverse stock split of its issued and outstanding common stock and stock options, and a proportional adjustment to the existing conversion ratios for the Company’s redeemable convertible preferred stock. Additionally, upon closing of the IPO a warrant issued to purchase up to 2,857,142 shares of the Company’s Series B redeemable convertible preferred stock converted into a warrant exercisable for 338,784 shares of the Company’s common stock. Accordingly, all issued and outstanding common stock, options to purchase common stock and per share amounts contained in the consolidated financial statements have been retroactively adjusted to give effect to the reverse stock split for all periods presented, except as otherwise stated. Risks and Uncertainties The Company is subject to risks common to other life science companies in the early development stage including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on key personnel, market acceptance of products, product liability, protection of proprietary technology, ability to raise additional financing and compliance with the Food and Drug Administration, or the FDA, and other government regulations. If the Company does not successfully advance its programs into and through human clinical trials and/or enter into collaborations for its programs and commercialize any of its product candidates, the Company may be unable to produce product revenue or achieve profitability. There can be no assurance that the Company’s research and development efforts will be successful, adequate protection for the Company’s intellectual property will be obtained, any products developed will obtain necessary government regulatory approval, or any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. COVID-19 Pandemic The impact of the coronavirus, or COVID-19, pandemic on the Company’s business, results of operations and financial condition is uncertain and will depend on future developments, including the duration and spread of the outbreak, the impact of vaccines and new strains of COVID-19, and any governmental advisories and restrictions.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2. Summary of significant accounting policies Basis of Presentation The Company has prepared the accompanying consolidated financial statements in conformity with generally accepted accounting principles in the United States of America, or U.S. GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB. Principles of Consolidation The Company’s consolidated financial statements include the accounts of C4 Therapeutics, Inc. and its wholly owned subsidiary C4T Securities Corporation, a Massachusetts securities corporation. All significant intercompany balances and transactions have been eliminated in consolidation. Emerging Growth Company The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act. Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it is (i) no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. This process may result in actual results differing materially from those estimated amounts used in the preparation of the consolidated financial statements if these results differ from historical experience or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, amounts and timing of revenues recognized under the Company’s research and development collaboration arrangements and accrued research and development expense. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates. Segments Operating segments are defined as components of an enterprise for which separate and discrete information is available for evaluation by the chief operating decision-maker in deciding how to allocate resources and assess performance. The Company has one operating segment. The Company’s chief operating decision maker, its Chief Executive Officer, manages the Company’s operations on a consolidated basis for the purpose of allocating resources. All of the Company’s long-lived assets are held in the United States. Cash and Cash Equivalents The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. The Company’s cash equivalents are measured at fair value on a recurring basis. Marketable securities The Company classifies marketable securities with a remaining maturity when purchased of greater than three months as available-for-sale. Available-for-sale securities are carried at fair value with the unrealized gains and losses included in accumulated other comprehensive income as a component of stockholders’ equity (deficit) until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the instrument. Realized gains and losses are determined using the specific identification method and are included in other income (expense). Restricted Cash Restricted cash consists of cash placed in separate restricted bank accounts as required under the terms of the Company’s lease agreements for its Watertown, Massachusetts facility (see Note 6, Leases Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, and restricted cash. The Company may maintain deposits in financial institutions in excess of government insured limits. The Company believes that it is not exposed to significant credit risk as its deposits are held at financial institutions that management believes to be of high credit quality and the Company has not experienced any losses on these deposits. Additionally, t he Company has established guidelines relative to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. The Company maintains its funds in accordance with its investment policy, which defines allowable investments, specifies credit quality standards and is designed to limit credit exposure to any single issuer. Fair Value of Financial Instruments ASC Topic 820, Fair Value Measurement • Level 1—Quoted market prices in active markets for identical assets or liabilities. • Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves. • Level 3—Unobservable inputs developed using estimates of assumptions developed by the Company, which reflect those that a market participant would use. To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair values requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Cash, cash equivalents and restricted cash are Level 1 assets which are comprised of funds held in checking and money market accounts. Marketable securities are Level 2 assets which are comprised of US treasury funds with maturity dates of less than one year. The carrying amounts of accounts receivable, which relate to the Company’s collaboration agreements, accounts payable, and accrued expenses approximate their fair values due to their short-term nature. Property and Equipment Property and equipment are recorded at cost. Expenditures for repairs and maintenance are expensed as incurred. When assets are retired or disposed of, the assets and related accumulated depreciation are derecognized from the accounts, and any resulting gain or loss is included in the determination of net loss. Depreciation on equipment is calculated using the straight-line method over the estimated useful lives of the assets as follows: Asset category Estimated useful life Laboratory equipment 5 years Computer equipment 3 years Office equipment, furniture and fixtures 5 years Leasehold improvements Lesser of useful life or remaining lease term Leases The Company accounts for leases in accordance with ASC Topic 842, Leases Certain adjustments to the right-of-use asset may be required for items such as incentives received. The Company typically only includes an initial lease term in its assessment of a lease arrangement; options to renew a lease are not included in the assessment unless there is reasonable certainty that the Company will renew. Impairment of Long-Lived Assets The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceed the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. No impairments were recognized for these assets in the years ended December 31, 2020 and 2019. Commitments and Contingencies Liabilities for loss contingencies arising from claims, assessments, litigation, fines and penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. Legal costs incurred in connection with loss contingencies are expensed as incurred. Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers The Company enters into collaboration and licensing agreements with strategic partners, which are within the scope of ASC 606, under which it may exclusively license rights to research, develop, manufacture, and commercialize its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: (1) non-refundable, upfront license fees; (2) reimbursement of certain costs; (3) customer option fees for additional goods or services; (4) development milestone payments, (5) regulatory and commercial milestone payments; and (6) royalties on net sales of licensed products. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must use its judgment to determine: (a) the number of performance obligations based on the determination under step (ii) above; (b) the transaction price under step (iii) above; (c) the stand-alone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above; and (d) the contract term and pattern of satisfaction of the performance obligations under step (v) above. The Company uses judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price as described further below. The transaction price is allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. Amounts due to the Company for satisfying the revenue recognition criteria or that are contractually due based upon the terms of the collaboration agreements are recorded as accounts receivable in the Company’s consolidated balance sheet. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current deferred revenue. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. Upfront License Fees If the license to the Company’s intellectual property is determined to be distinct from the other promises or performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. In assessing whether a promise or performance obligation is distinct from the other promises, the Company considers factors such as the research, manufacturing, and commercialization capabilities of the customer; the retention of any key rights by the Company; and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the customer can benefit from a promise for its intended purpose without the receipt of the remaining promises, whether the value of the promise is dependent on the unsatisfied promise, whether there are other vendors that could provide the remaining promise and whether it is separately identifiable from the remaining promise. For licenses that are combined with other promises, the Company exercises judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Customer Options If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, the goods and services underlying the customer options are not considered to be performance obligations at the outset of the arrangement, as they are contingent upon option exercise. The Company evaluates the customer options for material rights or options to acquire additional goods or services for free or at a discount. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the relative standalone selling price, which is determined based on the identified discount and the probability that the customer will exercise the option. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised. If an option is not exercised and the target is terminated, the Company will accelerate and recognize all remaining revenue related to the material right performance obligation. Research and Development Services The promises under the Company’s collaboration agreements may include research and development services to be performed by the Company for or on behalf of the customer. Payments or reimbursements resulting from the Company’s research and development efforts are recognized as the services are performed and presented on a gross basis because the Company is the principal for such efforts. Reimbursements from and payments to the customer that are the result of a collaborative relationship with the customer, instead of a customer relationship, such as co-development activities, are recorded as a reduction to research and development expense. Milestone Payments At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant revenue reversal would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. For further discussion of accounting for collaboration revenues, see Note 8, Collaboration and License Agreements. Research and Development Research and development costs are expensed as incurred. Research and development costs include salaries, share-based compensation and other employee benefit expenses, lab related supplies and other operational costs related to the Company’s research and development activities, including allocated facility-related expenses and external costs of outside vendors engaged to conduct research and development activities. Costs associated with licenses of technology are expensed as incurred and are included in research and development expense in the consolidated statement of operations and comprehensive loss. As part of the process of preparing the consolidated financial statements, the Company is required to estimate their accrued research and development expenses. The Company makes estimates of the accrued expenses as of each balance sheet date in the consolidated financial statements based on facts and circumstances known at that time. In addition, there may be instances in which payments made to the Company’s vendors will exceed the level of services provided and result in a prepayment of the expense in which case such amounts are reflected as prepaid expenses and other current assets. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company adjusts the accrual or the amount of prepaid expenses accordingly. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized in prepaid expenses and other current assets. The capitalized amounts are expensed as the related goods are delivered or the services are performed. Stock-Based Compensation The Company measures and recognizes stock-based compensation expense based on the grant date fair value of the awards, which consist of option grants. The fair value of each share option grant was determined using the expected term, expected volatility, risk-free interest rate, dividend rate, and the fair value of the common stock underlying the share-based award. Prior to the IPO, the fair value of common stock underlying share-based awards is based on an estimate at each grant date by the Company’s board of directors. The Company determined the estimated per share fair value of its common stock at various dates considering contemporaneous and retrospective valuations in accordance with the guidance outlined in the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation The Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period of the awards for service-based awards, which is generally the vesting period. Stock-based compensation expense is classified in the consolidated statement of operations and comprehensive loss in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified. Warrant Liability Expense In connection with the Company’s completion of a financing involving the sale of shares of Series B redeemable convertible preferred stock, or the Series B Financing, in June and July 2020 and the entry into the Term Loan (see Note 9, Long-term debt and warrant liability Upon completion of the IPO, the warrant converted into a warrant to purchase shares of the Company’s common stock, as described in Note 9, Long-term debt and warrant liability As noted above, the Company utilized the Black-Scholes option-pricing model, which incorporates assumptions and estimates, to value the warrant. Estimates and assumptions impacting the fair value measurement include the fair value per share of the underlying redeemable convertible Series B Preferred Stock or common stock issuable upon exercise of the warrant, remaining contractual term of the warrant, risk-free interest rate, expected dividend yield and expected volatility of the price of the underlying redeemable convertible preferred stock or common stock. Income Taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequence of events that have been recognized in the consolidated financial statements or the Company’s tax returns. Under this method, deferred tax assets and liabilities are determined based on the differences between the consolidated financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established. The Company accounts for uncertain tax positions recognized in the consolidated financial statements by prescribing a more-likely-than-not threshold for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) which includes certain changes in equity that are excluded from net loss. The Company’s only element of other comprehensive income is unrealized gains and losses on marketable securities. Net Loss Per Share Basic net loss per share and diluted net loss per share are computed using the weighted-average number of shares of common stock outstanding for the period. Net loss per share attributable to common stockholders is calculated using the two-class method, which is an earnings allocation formula that determines net loss per share for the holders of shares of the Company’s common stock and participating securities. The Company’s Preferred Stock contains participation rights in any dividend paid by the Company and is deemed to be a participating security. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods in which a net loss is recorded. Diluted net loss per share is computed using the more dilutive of (a) the two-class method or (b) the if-converted method. The Company allocates earnings first to preferred stockholders based on dividend rights and then to common and preferred stockholders based on ownership interests. The weighted-average number of shares of common stock included in the computation of diluted net loss gives effect to all potentially dilutive common stock equivalent shares, including outstanding stock options and Preferred Stock. Common stock equivalent shares are excluded from the computation of diluted net loss per share if their effect is antidilutive. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is generally the same as basic net loss per share attributable to common stockholders since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Going Concern At each reporting period, the Company evaluates whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the consolidated financial statements are issued. The Company is required to make certain additional disclosures if it concludes substantial doubt exists and it is not alleviated by the Company’s plans or when its plans alleviate substantial doubt about the Company’s ability to continue as a going concern. The Company’s evaluation entails analyzing prospective operating budgets and forecasts for expectations of the Company’s cash needs and comparing those needs to the current cash and cash equivalent balance. Recently Adopted Accounting Standards In June 2016 the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses This standard became effective for the Company on January 1, 2020 and, based on the composition of the Company’s receivables and available-for-sale debt securities, current economic conditions and historical credit loss activity, the adoption of this standard did not have a material impact on its consolidated financial statements and related disclosures. Recently Issued Accounting Standards In December 2019, the FASB issued ASU No. 2019-12, Income Taxes Simplifying the Accounting for Income Taxes, or In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 3. Fair value measurements The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values as of December 31, 2020 (in thousands): Fair Value Level 1 Level 2 Level 3 Assets Cash equivalents Money market funds $ 180,078 $ 180,078 $ — $ — Marketable securities U.S. Treasury securities 189,962 — 189,962 — Total assets $ 370,040 $ 180,078 $ 189,962 $ — The following table sets forth the fair value of the Company’s financial assets by level within the fair value hierarchy at December 31, 2019 (in thousands): Fair Value Level 1 Level 2 Level 3 Assets Cash equivalents Money market funds $ 80,902 $ 80,902 $ — $ — Total assets $ 80,902 $ 80,902 $ — $ — The Company classifies its money market funds, which are valued based on quoted market prices in active markets, with no valuation adjustment, as Level 1 assets within the fair value hierarchy. Marketable securities consist of U.S. Treasury securities and are classified as available-for-sale pursuant to ASC 320, Investments – Debt and Equity Securities As further discussed in Note 9, Long-term debt and warrant liability, Stock price $ 26.96 Exercise price $ 8.86 Expected term (in years) 9.75 Volatility 75.00 % Risk-free interest rate 0.76 % Dividend yield — The following table presents the changes in Level 3 instruments, redeemable convertible preferred stock warrant, for the year ended December 31, 2020: Balance at December 31, 2019 $ — Issuance of warrant 2,325 Change in fair value 5,676 Reclassification to equity (8,001 ) Balance at December 31, 2020 $ — As of December 31, 2020, the warrant has not been exercised. There have been no transfers between fair value levels during the years ended December 31, 2020 and 2019.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2020
Marketable Securities [Abstract]
Marketable Securities	Note 4. Marketable securities Marketable securities at December 31, 2020 consisted of the following: Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value U.S. Treasury securities $ 189,949 $ 13 $ — $ 189,962 As of December 31, 2020, none of the Company’s marketable securities were in an unrealized loss position. During the year ended December 31, 2020, the Company did not recognize any other-than-temporary impairment losses. The contractual maturity dates of the Company’s marketable securities are less than one year. The Company did not have any marketable securities at December 31, 2019.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Property and Equipment	Note 5. Property and equipment Property and equipment as of December 31, 2020 and 2019 consisted of the following (in thousands): As of December 31, 2020 2019 Laboratory equipment $ 7,207 $ 6,766 Furniture and fixtures 805 797 Leasehold improvements 541 520 Computer equipment 223 167 Office equipment 179 167 Total 8,955 8,417 Less: accumulated depreciation (5,632 ) (3,954 ) Property and equipment, net $ 3,323 $ 4,463 Depreciation expense related to property and equipment for the years ended December 31, 2020 and 2019 is as follows (in thousands): Years Ended December 31, 2020 2019 Depreciation expense $ 1,617 $ 1,595

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Note 6. Leases In July 2017, the Company entered into a lease of office and laboratory space for its headquarters in Watertown, Massachusetts, or the Watertown Lease. The Watertown Lease has a non-cancelable term of ten years with an option to extend for one additional five-year period and is subject to rent escalation throughout the term. Additionally, the Watertown Lease required the Company to provide collateral in the amount of $2.6 million, which is recorded as restricted cash on the accompanying consolidated balance sheets. The Watertown Lease commenced in April 2018, with rent commencing in May 2018. The Watertown Lease was classified as an operating lease and, upon the commencement in April 2018, the Company recorded a lease liability of $15.1 million and a right-of-use asset of $16.7 million, which is inclusive of $1.5 million of construction costs funded by the Company. In calculating the lease liability and the right-of-use asset, the Company did not include the additional five-year period option as management does not believe there is reasonable certainty the Company will exercise the option. In addition to rent, the Company is also responsible for paying its pro rata share of costs incurred for common area maintenance, real estate taxes and property insurance related to the leased space, which are accounted for as variable lease costs. The elements of lease costs for the years ended December 31, 2020 and 2019 were as follows (in thousands): 2020 2019 Lease cost: Operating lease cost $ 2,550 $ 2,550 Variable lease cost 1,066 1,020 Total lease cost $ 3,616 $ 3,570 Other information: Operating cash flows for operating liabilities $ 2,206 $ 2,141 Remaining lease term 7.3 years 8.3 years Discount rate 10 % 10 % Future lease payments under non-cancelable leases as of December 31, 2020 for each of the years ending December 31 are as follows (in thousands): 2021 $ 2,272 2022 2,340 2023 2,410 2024 2,483 2025 2,557 Thereafter 6,277 Total undiscounted lease payments 18,339 Less: imputed interest (5,471 ) Total operating lease liability at December 31, 2020 $ 12,868

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Note 7. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following as of December 31, 2020 and 2019 (in thousands): 2020 2019 Accrued research and development $ 3,799 $ 2,615 Accrued compensation and benefits 3,724 3,048 Accrued professional fees 1,532 728 Other 469 280 Total accrued expenses and other current liabilities $ 9,524 $ 6,671

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2020
Collaboration And License Agreements [Abstract]
Collaboration and License Agreements	Note 8. Collaboration and license agreement Financial information related to the collaboration and license agreements consisted of the following as of and for the year ended December 31, 2020 (in thousands): Accounts Receivable Collaboration Revenue Deferred Revenue, Current Deferred Revenue, Net of Current Deferred Revenue, Total Roche Agreement $ 750 $ 9,051 $ 11,238 $ 26,991 $ 38,229 Biogen License Agreement 776 9,913 13,965 26,026 39,991 Calico License Agreement 2,958 14,231 2,400 600 3,000 $ 4,484 $ 33,195 $ 27,603 $ 53,617 $ 81,220 Financial information related to the collaboration and license agreements consisted of the following as of and for the year ended December 31, 2019 (in thousands): Description Accounts Receivable Collaboration Revenue Deferred Revenue, Current Deferred Revenue, Net of Current Deferred Revenue, Total Roche Agreement $ — $ 6,409 $ 12,164 $ 32,784 $ 44,948 Biogen License Agreement — 2,432 6,141 36,934 43,075 Calico License Agreement 4,348 12,540 2,400 3,000 5,400 $ 4,348 $ 21,381 $ 20,705 $ 72,718 $ 93,423 Other financial information related to the collaboration and license agreements for the years ended December 31, 2020 and 2019 are (in thousands): 2020 2019 Revenue recognized that was included in the contract liability at the beginning of the period $ 17,570 $ 11,948 Revenue recognized from performance obligations fully or partially satisfied in previous periods 348 — Aggregate amount of the transaction price allocated to the performance obligations that are partially or fully unsatisfied as of the end of the reporting period 91,137 103,923 Roche Collaboration and License Agreement Original Roche Agreement Structure In March 2016, the Company entered into a license agreement, or the Original Roche Agreement, with Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc., or Roche. Pursuant to the terms of the Original Roche Agreement, the Company and Roche agreed to collaborate on research activities to develop novel treatments in the field of targeted protein degradation using the Company’s degrader technology. In exchange for a $15.0 million nonrefundable upfront payment and additional fees for dedicated personnel, the Company performed initial research and development services for drug discovery and preclinical development, provided a non-exclusive research and development license to its technology and participated on the joint research committee, or the Roche JRC. Restated Roche Agreement Structure On December 22, 2018, the Company and Roche executed the Amended and Restated Roche License Agreement, or the Roche Agreement. Under the Roche Agreement, the Company has a more active role in the manufacturing and commercialization of the targets, whereby if certain co-development and co-detailing rights are opted into by the Company, the parties will split future development costs in return for the rights to a larger share of future earnings from commercialization of the target. The target structure was revised to six potential targets, three of which were nominated as of the execution of the Roche Agreement and represent continuations of the initial preclinical research and development efforts begun under the Original Roche Agreement and three additional targets that were not nominated as of the execution of the Roche Agreement. Roche maintained its option rights to license and commercialize these six targets. For certain targets, Roche is required to pay the Company fees of $2.0 million and $3.0 million upon the progression of targets to the lead series identification achievement and GLP toxicology, or Tox, study phase, respectively. For each target option exercised by Roche, the Company is eligible to receive up to $275.0 million in research and development milestones per target and commercial milestone payments, with the commercial milestones being dependent on underlying net sales. Roche is also required to pay the Company up to $150.0 million per target in one-time sales-based payments if the target achieves certain levels of net sales. In addition, Roche is required to pay the Company royalties, at percentages from the mid-single digits to the low double-digits, on a licensed product-by licensed product basis, on worldwide net product sales. Under the Roche Agreement: • the Company received additional upfront consideration of $40.0 million from Roche; • the Company has an option for co-development and co-detailing rights, whereby it would be required to provide additional financial support in return for the rights to a larger share of future earnings from commercializing one or more of the six targets; • Roche will no longer provide FTE reimbursement; rather, it will make annual research plan payments of $1.0 million for each active research plan; and • Adjustments were made to the option exercise fees, whereby certain targets now have option exercise fees of $7.0 million to $12.0 million (those progressed up to Phase 1 or through the GLP Tox studies, respectively) and others have $20.0 million (those progressed through clinical trials). The collaboration is managed by a joint research committee. The Company has control over the committee and may terminate the Roche Agreement on a target-by-target or product-by-product basis under several scenarios, upon at least 90 days’ prior written notice. In November 2020, the Company signed an amendment to the Roche Agreement that provides a mechanism through which the Company and Roche can mutually agree to terminate the Roche Agreement on a target-by-target basis by entry into a mutual target termination agreement. Upon a termination of this nature, the Roche Agreement, as amended, provides that all rights in know-how and intellectual property in support of products that use inhibition as their mode of action, referred to as the Roche Field, will revert to Roche and all rights in respect of know-how and intellectual property in support of products that use degradation as their mode of action, referred to as the C4T Field, will revert to the Company. Further, this amendment states that, following the entry into a mutual target termination agreement, Roche will have rights in and responsibility for any know-how and intellectual property generated as a result of the collaboration that fits within the Roche Field and the Company will have rights in and responsibility for any know-how and intellectual property generated as a result of the collaboration that fits within the C4T Field. In support of this allocation of rights, under the amendment, Roche provided the Company, and the Company provided Roche, with a perpetual, irrevocable, fully paid up, exclusive (even as to party granting the license), sublicensable (including in multiple tiers) license to the know-how and intellectual property rights that are allocated to a party under the mutual target termination agreement. Finally, through the entry into this amendment, the Company and Roche mutually agreed to terminate the Roche Agreement as to the target EGFR. Roche Agreement Accounting The Roche Agreement is a modification of the Original Roche Agreement under ASC 606 as both the scope and price of the contract were changed under the Roche Agreement and new, distinct performance obligations were created for targets that have different standalone selling prices based on the Company’s revised obligations. The Roche Agreement was not determined to be a separate contract for accounting purposes. The modification was accounted for as if it were a termination of the existing contract and the creation of a new contract, for which the unrecognized consideration from the Original Roche Agreement is added to the new transaction price promised as part of the Roche Agreement and will be recognized as revenue prospectively, as the new performance obligations are satisfied. The Company made this determination after considering the performance obligations under the Roche Agreement. When the amendment was signed, the contract was restructured such that the Company would pursue some of the same targets, but would have additional material responsibility to potentially develop the targets beyond the option exercise point, to either Phase 1 completion or to a point where the Company will exercise its co-development and co-detailing options and more fully share in the costs and future revenues. The $40.0 million upfront payment, $13.5 million of expected research plan funding payments, plus $6.4 million of remaining deferred revenue from the Original Roche Agreement represent the transaction price as of the outset of the arrangement. The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Roche, is a customer. The Company identified the following promises at the outset of the Roche Agreement: (1) a non-exclusive royalty-free license to use the Company’s intellectual property to conduct research and development activities; (2) research and development services under the research plan for the three initial targets; (3) participation on the Roche JRC; (4) option rights to initiate a research plan for three additional targets; (5) an option to obtain a non-exclusive commercial license to intellectual property and know-how generated from the collaboration, subject to certain exclusivity requirements; (6) option rights to develop, commercialize and manufacture products related to any of the six targets; and (7) rights for Roche to substitute targets prior to completion of a research plan, limited to six exchanges in total across the arrangement and subject to approval by the Roche JRC. The Roche JRC has equal representation from both parties, but the Company holds final decision-making authority in the event of a disagreement until the time at which Roche licenses a target and leads development efforts. The six potential targets were determined to be distinct from one another, as Roche can derive benefit from each target independent of the others. For each target, the Company determined that the research and development license and research and development services were not distinct from one another, because the research and development services are essential to the license. Roche would receive little to no economic benefit from the license if it did not obtain the research services. Participation on the Roche JRC to oversee the research and development activities and the technology transfer associated with the Original Roche Agreement were determined to be quantitatively and qualitatively immaterial. The Company evaluated Roche’s option rights to initiate a research plan for three additional targets as well as the option rights to license and commercialize each target to determine whether they provide Roche with any material rights. The Company concluded that each of the options were issued with an option exercise fee that represented a significant and incremental discount and therefore provide material rights for six of the six targets—three material rights from the option to license the three initial targets at the end of their research terms and three material rights from the option to initiate a research plan for the three additional targets along with the option to license such at the end of their research terms. The consideration allocated to the option rights to initiate the three additional targets is deferred until the underlying option is exercised, at which point the Company will begin recognizing revenue for these targets. The non-exclusive, limited commercial license to the intellectual property and know-how generated from the collaboration was determined to be immaterial and, as such, no consideration was allocated to it. Based on these assessments, the Company identified twelve performance obligations, including three research services performance obligations, six material rights for the options to purchase a commercial license for six targets, and three material rights for the option to initiate research services for the uninitiated three targets as of the outset of the arrangement. The first three performance obligations primarily comprise: (1) the non-exclusive research and development license and (2) the research and development services for the target, including the related substitution rights. The Company included the $40.0 million upfront payment, $13.5 million of expected research plan funding payments ($1.0 million per active target per year, for a maximum of $3.0 million per target), and $6.4 million of remaining deferred revenue from the Original Roche Agreement in the transaction price as of the outset of the arrangement. The Company also achieved a milestone for the identification of lead series for target 2 in April 2019, resulting in a milestone payment of $2.0 million, which was added to the transaction price and recognized cumulatively. The transaction price of $61.9 million was allocated to the performance obligations based on the estimated stand-alone selling prices at the time of the amendment. For each performance obligation, the stand-alone selling price was determined considering the expected cost of the research and development services and a reasonable margin for the respective services. The material rights from the option rights were valued based on the estimated discount at which the option is priced and the Company’s estimated probability of the options’ exercise as of the time of the amendment. The Company allocated the following amounts of the total transaction price to the performance obligations as of the amendment date, including the $2.0 million milestone achieved in April 2019: • $29.0 million to the research and development performance obligations for targets 1-3; • $4.1 million to the three material rights, related to the three targets initiated at the outset of the Roche Agreement, which will not begin revenue recognition until the option is exercised or expires; and • $28.8 million to the option to nominate targets 4-6 and the three material rights related to these options. The Company will recognize the portion of the transaction price allocated to each of the research and development performance obligations as the research and development services are provided, using an input method, according to costs incurred as related to the research and development activities for each individual program and the costs expected to be incurred in the future to satisfy that individual performance obligation. The transfer of control occurs over this time period and, in management’s judgment, is the best measure of progress towards satisfying the performance obligation. Amounts due to the Company that have not yet been received are recorded as accounts receivable and amounts received that have not yet been recognized as revenue are recorded in deferred revenue on the Company’s consolidated balance sheet. Biogen Collaboration Research and License Agreement In December 2018, the Company entered into a collaboration research and license agreement, or the Biogen License Agreement, with Biogen MA, Inc., or Biogen. Pursuant to the terms of the Biogen License Agreement, the Company and Biogen agreed to collaborate on research activities to develop novel treatments in the field of TPD using the Company’s degrader technology. In February 2020, the Company entered into an amendment to the Biogen Agreement that provided further clarity around Biogen’s ownership of target binding moieties, which are portions of molecules, and any related intellectual property that are directed at or bind to collaboration targets. This amendment further provides that Biogen licenses to the Company the rights to use these Biogen target binding moieties and any related intellectual property as needed in order to conduct the research and development activities contemplated under the Biogen Agreement. Under the terms of the Biogen License Agreement, the Company will initially develop TPD therapeutics that utilize degrader technology for up to five target proteins over a period of 54 months. On a target-by-target basis, after successful completion of a defined target evaluation period, Biogen assumes full rights and responsibility to each degrader to meet certain criteria against a target. Biogen also has the option to pay an additional $62.5 million to extend the contract and select up to five additional targets for development. In exchange for the non-exclusive research license from Biogen as well as a $45.0 million nonrefundable upfront payment, the Company will grant a license to develop, commercialize and manufacture products related to each of the targets, which is contingent on not cancelling the contract, will perform initial research services for drug discovery, provide a non-exclusive research and commercial license to its intellectual property and will participate on the joint steering committee, or the Biogen JSC. The Company will also be obligated to participate in early research activities for other potential targets, referred to as sandbox activities at Biogen’s election up to a maximum amount; any work performed for these services will be reimbursed by Biogen, and Biogen will reimburse the Company for certain FTE costs. Biogen is also required to pay the Company up to $35.0 million per target in development milestones and $26.0 million per target in one-time sales-based payments for the first product to achieve certain levels of net sales. In addition, Biogen is required to pay the Company royalties on a licensed product-by-licensed product basis, on worldwide net product sales. The collaboration is managed by the Biogen JSC, which Biogen has control over, and Biogen may terminate the Biogen License Agreement on a target-by-target or product-by-product basis under several scenarios, upon at least 90 days’ prior written notice. The nonrefundable upfront cash payment of $45.0 million is not creditable against any of the target development milestone fees. The research will be performed by the Company over 54 months according to the research plan approved by the Biogen JSC. Biogen License Agreement Accounting The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Biogen, is a customer. The Company identified the following promises under the arrangement: (1) a non-exclusive, royalty-free license to use the Company’s intellectual property to conduct research activities; (2) an upfront license to develop, commercialize and manufacture products related to each of the targets (which is contingent on not cancelling the contract); (3) research services for preclinical activities under the research plan; (4) participation on the Biogen JSC; and (5) substitution rights for Biogen via sandbox activities to replace targets prior to a program reaching completion of a research plan, limited to five exchanges in total. Substitution is dependent on the original target failing to meet certain criteria; Biogen may only replace a target in this specific scenario. The Company also determined that Biogen’s ability to terminate the Agreement at-will with 90 days’ notice is not representative of a substantive purchase option to continue to the research and does not provide a material right in the form of a continuous renewal option. The Company determined that the licenses and research activities were not distinct from one another, as the licenses have limited value without the performance of the research activities by the Company. Participation on the Biogen JSC to oversee the research activities and the technology transfer associated with the Biogen License Agreement were determined to be quantitatively and qualitatively immaterial and therefore are excluded from performance obligations. Based on these assessments, the Company identified one performance obligation at the outset of the Biogen License Agreement, representing a combined performance obligation consisting of (1) the licenses, (2) the research activities for the target evaluation phase for all five targets and (3) the joint research plan phase for each target. The Company will recognize the transaction price as the research and development services are provided, using an input method, according to costs incurred as related to the research and development activities for the costs expected to be incurred in the future to satisfy that individual performance obligation. The transfer of control occurs over this time period and, in management’s judgment, is the best measure of progress towards satisfying the performance obligation. Biogen also has the option to fund sandbox activities in exchange for consideration, whereby the Company will perform discovery-type research at Biogen’s election to develop other potential targets that may be used as replacement targets for the initially nominated targets or two additional targets under the Biogen Agreement. Revenues earned under this option, if initiated, will be recognized as services are performed and are not included in the transaction price. Sandbox research activities will be reimbursed on an FTE basis at market rates, which is adjusted for changes in the “Consumer Price Index” each year. The sandbox activities constitute additional research that can be purchased on an a la carte basis at an amount consistent with standalone selling price. The Company recognizes revenue as the services performed for the sandbox activities are performed and recognized $2.8 and $0.5 million of revenue for the years ended December 31, 2020 and 2019, respectively, related to the sandbox activities. The Company recognizes FTE reimbursement related to sandbox activities as revenue as the hours are incurred each quarter. Amounts due to the Company that have not yet been received are recorded as accounts receivable and amounts received that have not yet been recognized as revenue are recorded in deferred revenue on the Company’s consolidated balance sheet. The Company achieved $4.0 million in milestones under the Biogen Agreement in June 2020, which amount was recorded as accounts receivable and deferred revenue at that time. The Company received payment of these milestones from Biogen in August 2020. Calico Collaboration and License Agreement In March 2017, the Company entered into a collaboration and license agreement, or the Calico License Agreement, with Calico Life Sciences LLC, or Calico, whereby the Company and Calico agreed to collaborate to develop and commercialize small molecule protein degraders for diseases of aging, including cancer for a five-year period ending in March 2022, the research term. Under the terms of the Calico License Agreement, the Company will initially develop and commercialize small molecule protein degraders for up to five target proteins over the research term. On a target-by-target basis, after successful completion of a defined target evaluation period, Calico has an exclusive option to pursue further pre-clinical development and commercialization via a joint research plan for each target. Under the Calico License Agreement, Calico paid an upfront amount of $5.0 million and certain annual payments totaling $5.0 million through December 31, 2020 and pays target initiation fees and reimburses the Company for a number of FTEs, depending on the stage of the research, at specified market rates. Upon completion of the required discovery research and development services on any target, Calico is entitled to pursue commercial development of that target. The Company will perform initial research services for drug discovery and preclinical development, provide a non-exclusive research and commercial license to its IP and will participate on the Calico joint research committee, or the CJRC. For each target, the Company is eligible to receive up to $132.0 million in potential research, development and commercial milestone payments, on sales of all products resulting from the collaboration efforts. Calico is also required to pay the Company up to $65.0 million in one-time sales-based payments for the first product to achieve certain levels of net sales. In addition, Calico is required to pay the Company royalties, at percentages in the mid-single digits, on a licensed product-by-licensed product basis, on worldwide net product sales. The Calico License Agreement is managed by CJRC. Calico has control over the CJRC and may terminate the Calico License Agreement on a target-by-target or product-by-product basis under several scenarios, upon prior written notice. The nonrefundable upfront and certain annual payments are not creditable against any other payments. Calico will reimburse the Company for a contractually defined number of FTEs per target depending on the phase of development, unless otherwise agreed upon by the CJRC. The research will be performed by the Company over the research term in accordance with the research plan. For the year ended December 31, 2019 the Company received $2.0 million in cash consideration for milestone revenue and no additional consideration in the form of cash received for target initiation fees. The Company recorded an accounts receivable of $1.0 million for additional target initiation fees in 2019 and received payment in 2020. Calico License Agreement Accounting The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Calico, is a customer. The Company identified the following promises under the arrangement: (1) the non-exclusive, royalty-free research license and commercial license, which function for purposes of the arrangement as a license and are therefore analyzed together; (2) the target evaluation research services for all five targets; (3) the joint research plan research services related to targets 1 and 2, which were nominated at the execution of the Calico License Agreement; (4) the target initiation rights or options associated with targets 3, 4 and 5, subject to nomination; and (5) the joint research plan services associated with targets 3, 4 and 5, subject to nomination and payment of the target initiation fees from (4). The Company determined that the license and research activities were not distinct from one another, as the license has limited value without the performance of the research activities by the Company. Participation on the CJRC to oversee the R&D activities and the technology transfer associated with the Calico License Agreement were determined to be quantitatively and qualitatively immaterial and therefore are excluded from performance obligations. The Company determined that the option rights to nominate the targets were not distinct from one another or from the other promises in the arrangement, specifically the research license and research services. The Company evaluated the target initiation rights for targets 3, 4 and 5 and the research services associated with the joint research plan nomination for these targets to determine whether they provide Calico with any material rights. The Company concluded that these options were not issued at a significant and incremental discount and therefore do not provide material rights. Based on these assessments, the Company identified one performance obligation at the outset of the Calico License Agreement, which consists of: (1) the non-exclusive license and (2) the research activities for the target evaluation phase for all five targets and the joint research plan phase for targets 1 and 2. Under the Calico License Agreement, the transaction price determined by the Company is the upfront amount plus the committed anniversary payments and the target initiation fees related to the targets nominated at the execution of the Calico License Agreement. Based on the ability of Calico to cancel the arrangement for any reason, Calico effectively has an option for continued access to the Company’s research license and procurement of research services that they can cancel at any time. Under the Calico License Agreement, the Company amortized the upfront fee received on a straight-line basis over the period services are available to the counterparty (i.e., the contractual term of five years). Straight-line amortization of the upfront payment was considered the best measure of progress because the customer has access to research and development services throughout the period. Incremental fees for research and development services are paid at agreed upon FTE rates and recognized in the period incurred. Amounts due to the Company that have not yet been received are recorded as accounts receivable and amounts received that have not yet been recognized as revenue are recorded in deferred revenue on the Company’s consolidated balance sheet.

Long-term Debt and Warrant Liab

Long-term Debt and Warrant Liability	12 Months Ended
	Dec. 31, 2020
Long Term Debt And Warrant Liability [Abstract]
Long-term Debt and Warrant Liability	Note 9. Long-term debt and warrant liability On June 5, 2020, contemporaneously with the completion of the Series B Financing (see Note 10, Stockholders’ equity The Company is required to make interest-only payments until December 5, 2022, after which point the Company will be required to make payments of principal equal to 2% of the Term Loan until maturity on June 5, 2024, or the Maturity Date. If the Company pays off the Term Loan prior to the Maturity Date, it will be required to pay a prepayment fee. Per the terms of the Credit Agreement, the prepayment fee is $5.0 million less any interest paid through the prepayment period. As of December 31, 2020, the prepayment fee would be $4.2 million. The Company paid issuance costs of $0.5 million in connection with its entry into the Credit Agreement. Under the terms of the Credit Agreement, the Company issued a warrant to purchase up to 2,857,142 shares of the Company’s Series B preferred stock to Perceptive at an exercise price per share of $1.05. The fair value of the warrant at the time of issuance was determined to be $2.3 million. The warrant is exercisable at any time prior to the ten-year anniversary of the closing date of the Credit Agreement. At issuance, the Company determined that the warrant is liability-classified and would be remeasured to fair value each reporting period, with changes in fair value recorded in the statement of operations and comprehensive loss. Upon the completion of the Company’s IPO on October 6, 2020, the warrant was effected for one-for-8.4335 reverse stock split and automatically converted into a warrant to purchase up to 338,784 shares of the Company’s common stock at an exercise price per share of $8.86. Based on information available at that time, the fair value of the warrant was determined to be $8.0 million on October 6, 2020. Upon the conversion into a warrant exercisable for shares of the Company’s common stock, management concluded that the warrant meets the definition of an equity instrument and the warrant was recorded, at its fair value on October 6, 2020, as an increase to additional paid-in capital. For the year ended December 31, 2020, the Company recognized $5.7 million in change in the fair value of the warrant liability as a component of other income (expense), net in the consolidated statement of operations and comprehensive loss. As of December 31, 2020, the outstanding long-term debt was $12.5 million. The outstanding amount is reduced by the unamortized portions of 1) issuance costs, and 2) the issuance date fair value of the warrant to arrive at the carrying value of long-term debt as of December 31, 2020, which was determined to be $10.1 million. As of December 31, 2020, the Company had met the criteria to draw down on the second tranche of $7.5 million. It has the ability, but not the obligation, to draw down the second tranche until June 30, 2021. Anticipated future minimum payments on long-term debt for the years ending December 31 are (in thousands): 2021 $ — 2022 — 2023 3,000 2024 9,500 Total minimum long-term debt payments 12,500 Less: Unamortized debt issuance costs, and debt discount related to warrant (2,448 ) Carrying value of long-term debt—related party at December 31, 2020 $ 10,052

Stockholder_s Equity

Stockholder’s Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Stockholder’s Equity	Note 10. Stockholders’ equity Certificate of Incorporation Prior to the IPO, the terms of the Company’s equity securities were defined in the Company’s Fourth Amended and Restated Certificate of Incorporation, which was filed with the Secretary of the State of Delaware on June 3, 2020, or the Fourth Charter. Under the Fourth Charter, the Company was authorized to issue Series Seed Preferred Stock, Series A Preferred Stock and Series B Preferred Stock, each of which had a par value of $0.0005 per share and which are referred to collectively as Preferred Stock. On October 6, 2020, in connection with the consummation of the IPO, the Company filed its Fifth Amended and Restated Certificate of Incorporation with the Secretary of the State of Delaware. The summary below relates to the Company’s Fourth Charter. Reverse Stock Split As described in Note 1, Nature of the business and basis of presentation Common Stock Under the Fourth Charter, the Company’s common stock had a par value of $0.0001 and the holders of common stock were entitled to one vote for each share held at all meetings of stockholders and written actions in lieu of meetings provided. The Fourth Charter also provided that all dividends shall be declared and paid pro rata according to the number of shares held by each holder of common stock. In the event of a liquidation, dissolution or winding up of the Company, the common stock ranks behind the Preferred Stock in terms of distribution of assets. The holders of the common stock have no preemptive or other subscription rights, and there are no redemption or sinking fund provisions with respect to such stock. Preferred Stock In June and July 2020, the Company closed a $150.0 million Series B Financing with existing and new investors. As part of the Series B Financing, the Company issued 142,857,142 shares of its Series B preferred stock at a purchase price of $1.05 per share, for aggregate gross proceeds of $150.0 million. Of the amounts above, 138,571,428 shares were issued for gross proceeds of $145.5 million, less related offering costs of $4.5 million in June 2020, and 4,285,714 shares were issued for proceeds of $4.5 million in July 2020. Upon the completion of the Company’s IPO on October 6, 2020, all outstanding shares of the Company’s Preferred Stock were converted into 30,355,379 shares of common stock using the exchange rate set forth in the Fourth Charter, as amended, which provided that every 8.4335 shares of Preferred Stock converted into one share of common stock. As a result, as of December 31, 2020, no shares of Preferred Stock are presently outstanding. As of December 31, 2019, Preferred Stock consisted of the following (in thousands, except share data): Preferred Stock Authorized Preferred Stock Issued and Outstanding Carrying Value Liquidation Value Common Stock Issuable Upon Conversion Series Seed Preferred Stock 4,000,000 4,000,000 $ 1,000 $ 1,000 474,298 Series A Preferred Stock 110,000,000 109,145,900 109,995 109,995 12,941,857 FF Preferred Stock 32,760,000 — — — — 146,760,000 113,145,900 $ 110,995 $ 110,995 13,416,155

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	Note 11. Stock-based compensation 2015 Incentive Stock Option and Grant Plan On December 28, 2015, the Company’s board of directors adopted the 2015 Incentive Stock Option and Grant Plan, or the 2015 Plan, and reserved 2,525,327 shares of common stock for issuance under this plan. The 2015 Plan authorizes the board of directors or a committee of the board to grant incentive stock options, nonqualified stock options and restricted stock awards to eligible employees, outside directors and consultants of the Company. Options generally vest over a period of five or eight years with a cliff vesting at one year and quarterly vesting thereafter and options that lapse or are forfeited are available to be granted again. The contractual life of all options is ten years from the date of grant. 2020 Stock Option and Incentive Plan On September 8, 2020, the Company’s board of directors adopted the C4 Therapeutics, Inc. 2020 Stock Option and Incentive Plan, or the 2020 Plan, which became effective on September 30, 2020. Upon adoption there were 6,567,144 shares of common stock reserved for issuance under the 2020 Plan. The Company’s Board of Directors, the Compensation Committee of the Board of Directors, and the Chief Executive Officer of the Company are authorized to grant a broad range of equity-based awards under the 2020 Plan, including stock options, stock appreciation rights, or SARs, restricted stock awards, or RSAs, restricted stock units, or RSUs, performance awards and stock bonus awards to the Company’s officers, employees, directors and other key persons, including consultants. Following the effectiveness of the 2020 Plan, the Company ceased making grants under the 2015 Plan. However, the 2015 Plan continues to govern the terms and conditions of the outstanding awards granted under it. Shares of common stock subject to awards granted under the 2015 Plan that cease to be subject to such awards by forfeiture or otherwise after the termination of the 2015 Plan will be available for issuance under the 2020 Plan. As of December 31, 2020, the Company had 8,880,367 shares reserved under the 2020 Plan and 2015 Plan, and 3,851,003 shares available for future issuance under the 2020 Plan. The 2020 Plan provides for an annual increase, to be added on the first day of each fiscal year, beginning with January 1, 2021 and continuing until the expiration of the 2020 Plan, equal to the lesser of (i) 5% of the outstanding shares of common stock on the immediately preceding December 31st, or (ii) lesser number of shares determined by the administrator of the 2020 Plan, which is the Company’s Board of Directors or the Compensation Committee of the Board of Directors. On January 1, 2021, the annual increase for the 2020 Plan resulted in an additional 2,152,981 shares authorized for issuance being added to the 2020 Plan. Stock-based compensation expense for the year ended December 31, 2020 and 2019 was classified in the consolidated statement of operations and comprehensive loss as follows (in thousands): 2020 2019 Research and development $ 972 $ 395 General and administrative 2,460 1,247 Total stock-based compensation expense $ 3,432 $ 1,642 The following table summarizes the stock option activity under the Company’s equity awards plans for the year ended December 31, 2020 : Number of Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2019 2,310,886 $ 4.42 8.11 $ 4,801 Granted 4,222,179 14.27 Exercised (281,584 ) 3.15 Forfeited/expired (1,222,117 ) 4.58 Outstanding as of December 31, 2020 5,029,364 $ 12.72 9.25 $ 102,635 Exercisable as of December 31, 2020 455,633 $ 4.28 7.34 $ 13,144 Vested and expected to vest as of December 31, 2020 5,029,364 $ 12.72 9.25 $ 102,635 Other information related to the option activity of the Company is as follows for the years ended December 31, 2020 and 2019: 2020 2019 Weighted-average fair value of options granted $ 9.24 $ 4.13 Intrinsic value of options exercised (in thousands) $ 2,587 $ 337 As of December 31, 2020, the unrecognized compensation cost related to outstanding options was $37.5 million, which is expected to be recognized over a weighted-average period of 3.7 years. The following table summarizes assumptions used in the Black-Scholes option pricing model to determine the fair value of stock options granted to employees for the years ended December 31, 2020 and 2019: 2020 2019 Expected option life (years) 5.23 - 6.35 6.35 Risk-free interest rate 0.32% - 0.57% 1.71% - 2.36% Expected volatility 69.54% - 83.76% 65.50% - 76.80% Expected dividend yield 0.00% 0.00% 2020 Employee Stock Purchase Plan On September 8, 2020, the Company’s board of directors adopted the C4 Therapeutics, Inc. 2020 Employee Stock Purchase Plan, or the 2020 ESPP, which became effective on September 30, 2020 for use by the Company following its IPO. Upon adoption there were 437,809 shares of common stock reserved for issuance under the 2020 ESPP. The 2020 ESPP provides for an annual increase to be added on the first day of each fiscal year, beginning with January 1, 2021 and continuing thereafter through January 1, 2030, equal to the lesser of (i) 1% of the outstanding shares of common stock on the immediately preceding December 31st, (ii) 656,714 shares, or (ii) lesser number of shares determined by the administrator of the 2020 ESPP. On January 1, 2021, the annual increase for the 2020 ESPP resulted in an additional 430,596 shares authorized for issuance being added to the 2020 ESPP. To participate in the 2020 ESPP, eligible employees may authorize payroll deductions of up to 15% of their eligible compensation during an offering period. The Company may hold one or more offering periods each year during which employees will be able to purchase shares under the 2020 ESPP. As of December 31, 2020, the Company had not held any offering periods and no shares had been issued under the 2020 ESPP. President and Chief Executive Officer Termination On March 3, 2020, or the Separation Date, the employment of the Company’s then current president and chief executive officer, or the Former CEO, terminated. The Company repurchased all of the Former CEO’s outstanding shares of common stock, which had been issued upon his exercise of previously granted stock options, for total consideration of $0.1 million. The Former CEO also relinquished his right to purchase shares of common stock upon the exercise of stock options that were vested as of his Separation Date, in exchange for total consideration paid by the Company of $0.7 million. The Company recognized the repurchase price of these shares of common stock and the relinquishment of these vested options in additional-paid-in-capital.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 12. Income Taxes Income tax (benefit) expense consists of the following for the years ended December 31, 2020 and 2019 (in thousands): 2020 2019 Current tax provision: Current federal provision $ (673 ) $ 669 Current state provision 47 135 Total current provision (626 ) 804 Deferred tax provision: Deferred federal provision — — Deferred state provision — — Total tax provision $ (626 ) $ 804 (a) Tax Rate Reconciliation A reconciliation of the expected income tax (benefit) expense computed at the statutory federal rate to income taxes as reflected in the consolidated financial statements is as follows for the years ended December 31, 2020 and 2019: 2020 2019 Income tax benefit computed at federal statutory tax rate 21.0 % 21.0 % Stock-based compensation (0.1 )% (0.4 )% State tax—net of federal 8.1 % 6.6 % State credits 1.2 % 0.6 % Federal credits 3.5 % 1.1 % Valuation allowance (34.1 )% (32.1 )% Rate change 3.1 % (0.1 )% Net operating loss carryback benefits 1.0 % 0.0 % Tax attributes true up due to net operating loss carryback (1.0 )% 0.0 % Other permanent differences (1.8 )% 0.9 % Total 0.9 % (2.4 )% (b) Significant Components of Deferred Taxes Deferred income taxes reflect the net tax effects of (a) temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and (b) operating losses and tax credit carryforwards. Significant components of the Company’s deferred tax assets and deferred tax liabilities are as follows as of December 31, 2020 and 2019 (in thousands): 2020 2019 Deferred tax assets: Capitalized start-up costs $ 1,075 $ 1,151 Operating lease liability 3,859 3,821 Stock-based compensation 1,344 542 Net operating losses 19,399 575 R&D and investment tax credits 5,578 441 Deferred revenue 23,157 25,271 Other 168 — Total gross deferred tax assets 54,580 31,801 Deferred tax liabilities: Right-of-use asset (3,967 ) (4,017 ) Fixed assets (744 ) (726 ) Unrealized gain/loss (3 ) Less: valuation allowance (49,866 ) (27,058 ) Net deferred taxes $ — $ — The Company has evaluated the positive and negative evidence bearing upon the realizability of the deferred tax assets. As of December 31, 2020 and 2019, based on the Company’s historical operating losses, the Company has concluded that it is more-likely-than-not that the benefit of its deferred tax assets will not be realized. Accordingly, the Company has provided a full valuation allowance for the deferred tax assets as of December 31, 2020 and 2019. The valuation allowance for deferred tax assets as of December 31, 2020 and 2019 was $49.9 million and $27.1 million, respectively. The net valuation allowance increase of $22.8 million during the year ended December 31, 2020 was primarily due to the increase in net operating loss and tax credits carryforward and a decrease in deferred revenue recognized during the year. As of December 31, 2020 and 2019, the Company had $58.8 million and no gross United States federal net operating loss, or NOL, carryforwards, respectively, which may be available to offset future income tax liabilities. The Tax Cuts and Jobs Act, or TCJA, which was enacted in December 2017, will generally allow federal losses generated after 2017 to be carried over indefinitely, but will generally limit the NOL deduction to the lesser of the NOL carryover or 80% of a corporation’s taxable income (subject to Section 382 of the Internal Revenue Code of 1986, as amended, or IRC). In addition, there will be no carryback for losses generated after 2017. Losses generated prior to 2018 will generally be deductible to the extent of the lesser of a corporation’s NOL carryover or 100% of a corporation’s taxable income and be available for twenty years from the period the loss was generated. For U.S. federal income tax purposes, the Company has federal NOLs generated after 2017 of $ As of December 31, 2020 and 2019, the Company has total gross United States state net operating loss carryforwards of $105.1 million and $8.2 million, respectively, which may be available to offset future income tax liabilities that expire at various dates through 2040. At December 31, 2020 and 2019, the Company has United States federal research credit carryforwards of $4.7 million and $0.4 million, respectively, which are available to offset future federal income tax liabilities, which expire at various dates through 2040. At December 31, 2020 and 2019, the Company has United States state research credit carryforwards of $1.1 million and $0.1 million, respectively, which are available to reduce future tax liabilities which expire at various dates through 2035. Under the provisions of the IRC, the net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the IRC, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. In 2020, the Company completed a study of ownership changes from inception through December 31, 2020, to assess whether an ownership change has occurred or whether there have been multiple ownership changes since its formation. The result of this study indicated that the Company experienced ownership changes as defined by IRS Section 382 of the Code, however there are no net operating loss carryforwards that will be limited and expire unused as a result of such ownership changes. The Company will recognize interest and/or penalties related to uncertain tax benefits in income tax expense as they arise. As of December 31, 2020 and 2019, the Company had no accrued interest or penalties related to uncertain tax benefits. The Company files income tax returns in the United States, California, and Massachusetts. The federal and state income tax returns are generally subject to tax examinations for the tax years ended December 31, 2017 through present. To the extent that the Company has tax attribute carryforwards, the tax years in which the attributes were generated may still be adjusted upon examination by the Internal Revenue Services or State tax authorities to the extent utilized in a future period. The Company is not currently under examination by any tax authorities. The CARES Act was enacted on March 27, 2020. The CARES Act contains a significant number of provisions that may impact on the Company’s accounting for income taxes. The Company has considered several key corporate provisions within the CARES Act, has evaluated its potential impact and as a result recorded a tax benefit of $0.6 million related to an anticipated refund to be received for federal taxes incurred for the tax year ended December 31, 2019. The refund is expected to be received in 2021 after the Company files the tax year 2020 net operating loss carryback claim upon the completion of its tax year 2020 tax returns, which are due October 15, 2021.

Loss Per Share

Loss Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Loss Per Share	Note 13. Loss per share As noted in Note 2, Summary of significant accounting policies 2020 2019 Series Seed Preferred Stock — 474,298 Series A Preferred Stock — 12,941,857 Options to purchase common stock 5,029,364 2,310,886 Warrant to purchase common stock 338,784 — 5,368,148 15,727,041 All redeemable, convertible preferred stock, including those that were outstanding as of December 31, 2019, as shown above, were converted to shares of the Company’s common and effected for a one-for-8.4335 reverse stock split. Basic and diluted loss per share is computed by dividing net loss attributable to common stockholders by the weighted-average common shares outstanding for the years ended December 31, 2020 and 2019 (in thousands, except share and per share data): 2020 2019 Numerator: Net loss $ (66,335 ) $ (34,099 ) Accrual of preferred stock dividends — (8,468 ) Net loss attributable to common stockholders—basic and diluted $ (66,335 ) $ (42,567 ) Denominator: Weighted-average common stock outstanding—basic and diluted 11,370,328 1,371,905 Net loss per share attributable to common stockholders—basic and diluted $ (5.83 ) $ (31.03 )

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan	Note 14. Defined contribution plan The Company has a 401(k) retirement plan, the 401(k) Plan, whereby all full-time employees may contribute up to 90% of their pre-tax compensation, up to the maximum allowable amount set by the Internal Revenue Service. The Company, at its discretion, matches 100% of contributions to the 401(k) Plan up to a maximum of $6,000 per year for each full-time employee. During each of the years ended December 31, 2020 and 2019, the Company contributed approximately $0.5 million and $0.4 million, respectively, to the 401(k) Plan.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company has prepared the accompanying consolidated financial statements in conformity with generally accepted accounting principles in the United States of America, or U.S. GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB.
Principles of Consolidation	Principles of Consolidation The Company’s consolidated financial statements include the accounts of C4 Therapeutics, Inc. and its wholly owned subsidiary C4T Securities Corporation, a Massachusetts securities corporation. All significant intercompany balances and transactions have been eliminated in consolidation.
Emerging Growth Company	Emerging Growth Company The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act. Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it is (i) no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. This process may result in actual results differing materially from those estimated amounts used in the preparation of the consolidated financial statements if these results differ from historical experience or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, amounts and timing of revenues recognized under the Company’s research and development collaboration arrangements and accrued research and development expense. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.
Segments	Segments Operating segments are defined as components of an enterprise for which separate and discrete information is available for evaluation by the chief operating decision-maker in deciding how to allocate resources and assess performance. The Company has one operating segment. The Company’s chief operating decision maker, its Chief Executive Officer, manages the Company’s operations on a consolidated basis for the purpose of allocating resources. All of the Company’s long-lived assets are held in the United States.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. The Company’s cash equivalents are measured at fair value on a recurring basis.
Marketable Securities	Marketable securities The Company classifies marketable securities with a remaining maturity when purchased of greater than three months as available-for-sale. Available-for-sale securities are carried at fair value with the unrealized gains and losses included in accumulated other comprehensive income as a component of stockholders’ equity (deficit) until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the instrument. Realized gains and losses are determined using the specific identification method and are included in other income (expense).
Restricted Cash	Restricted Cash Restricted cash consists of cash placed in separate restricted bank accounts as required under the terms of the Company’s lease agreements for its Watertown, Massachusetts facility (see Note 6, Leases
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, and restricted cash. The Company may maintain deposits in financial institutions in excess of government insured limits. The Company believes that it is not exposed to significant credit risk as its deposits are held at financial institutions that management believes to be of high credit quality and the Company has not experienced any losses on these deposits. Additionally, t he Company has established guidelines relative to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. The Company maintains its funds in accordance with its investment policy, which defines allowable investments, specifies credit quality standards and is designed to limit credit exposure to any single issuer.
Fair Value of Financial Instruments	Fair Value of Financial Instruments ASC Topic 820, Fair Value Measurement • Level 1—Quoted market prices in active markets for identical assets or liabilities. • Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves. • Level 3—Unobservable inputs developed using estimates of assumptions developed by the Company, which reflect those that a market participant would use. To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair values requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Cash, cash equivalents and restricted cash are Level 1 assets which are comprised of funds held in checking and money market accounts. Marketable securities are Level 2 assets which are comprised of US treasury funds with maturity dates of less than one year. The carrying amounts of accounts receivable, which relate to the Company’s collaboration agreements, accounts payable, and accrued expenses approximate their fair values due to their short-term nature.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost. Expenditures for repairs and maintenance are expensed as incurred. When assets are retired or disposed of, the assets and related accumulated depreciation are derecognized from the accounts, and any resulting gain or loss is included in the determination of net loss. Depreciation on equipment is calculated using the straight-line method over the estimated useful lives of the assets as follows: Asset category Estimated useful life Laboratory equipment 5 years Computer equipment 3 years Office equipment, furniture and fixtures 5 years Leasehold improvements Lesser of useful life or remaining lease term
Leases	Leases The Company accounts for leases in accordance with ASC Topic 842, Leases Certain adjustments to the right-of-use asset may be required for items such as incentives received. The Company typically only includes an initial lease term in its assessment of a lease arrangement; options to renew a lease are not included in the assessment unless there is reasonable certainty that the Company will renew.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceed the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. No impairments were recognized for these assets in the years ended December 31, 2020 and 2019.
Commitments and Contingencies	Commitments and Contingencies Liabilities for loss contingencies arising from claims, assessments, litigation, fines and penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. Legal costs incurred in connection with loss contingencies are expensed as incurred.
Revenue Recognition	Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers The Company enters into collaboration and licensing agreements with strategic partners, which are within the scope of ASC 606, under which it may exclusively license rights to research, develop, manufacture, and commercialize its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: (1) non-refundable, upfront license fees; (2) reimbursement of certain costs; (3) customer option fees for additional goods or services; (4) development milestone payments, (5) regulatory and commercial milestone payments; and (6) royalties on net sales of licensed products. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must use its judgment to determine: (a) the number of performance obligations based on the determination under step (ii) above; (b) the transaction price under step (iii) above; (c) the stand-alone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above; and (d) the contract term and pattern of satisfaction of the performance obligations under step (v) above. The Company uses judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price as described further below. The transaction price is allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. Amounts due to the Company for satisfying the revenue recognition criteria or that are contractually due based upon the terms of the collaboration agreements are recorded as accounts receivable in the Company’s consolidated balance sheet. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current deferred revenue. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. Upfront License Fees If the license to the Company’s intellectual property is determined to be distinct from the other promises or performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. In assessing whether a promise or performance obligation is distinct from the other promises, the Company considers factors such as the research, manufacturing, and commercialization capabilities of the customer; the retention of any key rights by the Company; and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the customer can benefit from a promise for its intended purpose without the receipt of the remaining promises, whether the value of the promise is dependent on the unsatisfied promise, whether there are other vendors that could provide the remaining promise and whether it is separately identifiable from the remaining promise. For licenses that are combined with other promises, the Company exercises judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Customer Options If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, the goods and services underlying the customer options are not considered to be performance obligations at the outset of the arrangement, as they are contingent upon option exercise. The Company evaluates the customer options for material rights or options to acquire additional goods or services for free or at a discount. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the relative standalone selling price, which is determined based on the identified discount and the probability that the customer will exercise the option. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised. If an option is not exercised and the target is terminated, the Company will accelerate and recognize all remaining revenue related to the material right performance obligation. Research and Development Services The promises under the Company’s collaboration agreements may include research and development services to be performed by the Company for or on behalf of the customer. Payments or reimbursements resulting from the Company’s research and development efforts are recognized as the services are performed and presented on a gross basis because the Company is the principal for such efforts. Reimbursements from and payments to the customer that are the result of a collaborative relationship with the customer, instead of a customer relationship, such as co-development activities, are recorded as a reduction to research and development expense. Milestone Payments At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant revenue reversal would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. For further discussion of accounting for collaboration revenues, see Note 8, Collaboration and License Agreements.
Research and Development	Research and Development Research and development costs are expensed as incurred. Research and development costs include salaries, share-based compensation and other employee benefit expenses, lab related supplies and other operational costs related to the Company’s research and development activities, including allocated facility-related expenses and external costs of outside vendors engaged to conduct research and development activities. Costs associated with licenses of technology are expensed as incurred and are included in research and development expense in the consolidated statement of operations and comprehensive loss. As part of the process of preparing the consolidated financial statements, the Company is required to estimate their accrued research and development expenses. The Company makes estimates of the accrued expenses as of each balance sheet date in the consolidated financial statements based on facts and circumstances known at that time. In addition, there may be instances in which payments made to the Company’s vendors will exceed the level of services provided and result in a prepayment of the expense in which case such amounts are reflected as prepaid expenses and other current assets. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company adjusts the accrual or the amount of prepaid expenses accordingly. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized in prepaid expenses and other current assets. The capitalized amounts are expensed as the related goods are delivered or the services are performed.
Stock-Based Compensation	Stock-Based Compensation The Company measures and recognizes stock-based compensation expense based on the grant date fair value of the awards, which consist of option grants. The fair value of each share option grant was determined using the expected term, expected volatility, risk-free interest rate, dividend rate, and the fair value of the common stock underlying the share-based award. Prior to the IPO, the fair value of common stock underlying share-based awards is based on an estimate at each grant date by the Company’s board of directors. The Company determined the estimated per share fair value of its common stock at various dates considering contemporaneous and retrospective valuations in accordance with the guidance outlined in the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation The Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period of the awards for service-based awards, which is generally the vesting period. Stock-based compensation expense is classified in the consolidated statement of operations and comprehensive loss in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified.
Warrant Liability Expense	Warrant Liability Expense In connection with the Company’s completion of a financing involving the sale of shares of Series B redeemable convertible preferred stock, or the Series B Financing, in June and July 2020 and the entry into the Term Loan (see Note 9, Long-term debt and warrant liability Upon completion of the IPO, the warrant converted into a warrant to purchase shares of the Company’s common stock, as described in Note 9, Long-term debt and warrant liability As noted above, the Company utilized the Black-Scholes option-pricing model, which incorporates assumptions and estimates, to value the warrant. Estimates and assumptions impacting the fair value measurement include the fair value per share of the underlying redeemable convertible Series B Preferred Stock or common stock issuable upon exercise of the warrant, remaining contractual term of the warrant, risk-free interest rate, expected dividend yield and expected volatility of the price of the underlying redeemable convertible preferred stock or common stock.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequence of events that have been recognized in the consolidated financial statements or the Company’s tax returns. Under this method, deferred tax assets and liabilities are determined based on the differences between the consolidated financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established. The Company accounts for uncertain tax positions recognized in the consolidated financial statements by prescribing a more-likely-than-not threshold for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) which includes certain changes in equity that are excluded from net loss. The Company’s only element of other comprehensive income is unrealized gains and losses on marketable securities.
Net Loss Per Share	Net Loss Per Share Basic net loss per share and diluted net loss per share are computed using the weighted-average number of shares of common stock outstanding for the period. Net loss per share attributable to common stockholders is calculated using the two-class method, which is an earnings allocation formula that determines net loss per share for the holders of shares of the Company’s common stock and participating securities. The Company’s Preferred Stock contains participation rights in any dividend paid by the Company and is deemed to be a participating security. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods in which a net loss is recorded. Diluted net loss per share is computed using the more dilutive of (a) the two-class method or (b) the if-converted method. The Company allocates earnings first to preferred stockholders based on dividend rights and then to common and preferred stockholders based on ownership interests. The weighted-average number of shares of common stock included in the computation of diluted net loss gives effect to all potentially dilutive common stock equivalent shares, including outstanding stock options and Preferred Stock. Common stock equivalent shares are excluded from the computation of diluted net loss per share if their effect is antidilutive. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is generally the same as basic net loss per share attributable to common stockholders since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.
Going Concern	Going Concern At each reporting period, the Company evaluates whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the consolidated financial statements are issued. The Company is required to make certain additional disclosures if it concludes substantial doubt exists and it is not alleviated by the Company’s plans or when its plans alleviate substantial doubt about the Company’s ability to continue as a going concern. The Company’s evaluation entails analyzing prospective operating budgets and forecasts for expectations of the Company’s cash needs and comparing those needs to the current cash and cash equivalent balance.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards In June 2016 the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses This standard became effective for the Company on January 1, 2020 and, based on the composition of the Company’s receivables and available-for-sale debt securities, current economic conditions and historical credit loss activity, the adoption of this standard did not have a material impact on its consolidated financial statements and related disclosures. Recently Issued Accounting Standards In December 2019, the FASB issued ASU No. 2019-12, Income Taxes Simplifying the Accounting for Income Taxes, or In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Depreciation on Equipment Calculated Using Straight-Line Method Over Estimated Useful Lives of Assets	Depreciation on equipment is calculated using the straight-line method over the estimated useful lives of the assets as follows: Asset category Estimated useful life Laboratory equipment 5 years Computer equipment 3 years Office equipment, furniture and fixtures 5 years Leasehold improvements Lesser of useful life or remaining lease term

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Financial Assets Measured at Fair Value on Recurring Basis	The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values as of December 31, 2020 (in thousands): Fair Value Level 1 Level 2 Level 3 Assets Cash equivalents Money market funds $ 180,078 $ 180,078 $ — $ — Marketable securities U.S. Treasury securities 189,962 — 189,962 — Total assets $ 370,040 $ 180,078 $ 189,962 $ — The following table sets forth the fair value of the Company’s financial assets by level within the fair value hierarchy at December 31, 2019 (in thousands): Fair Value Level 1 Level 2 Level 3 Assets Cash equivalents Money market funds $ 80,902 $ 80,902 $ — $ — Total assets $ 80,902 $ 80,902 $ — $ —
Summary of Assumptions to Determine Fair Value of Warrant	The fair value of the warrant was determined on October 6, 2020 using the following assumptions: Stock price $ 26.96 Exercise price $ 8.86 Expected term (in years) 9.75 Volatility 75.00 % Risk-free interest rate 0.76 % Dividend yield —
Summary of Changes in Level 3 Instruments, Redeemable Convertible Preferred Stock Warrant	The following table presents the changes in Level 3 instruments, redeemable convertible preferred stock warrant, for the year ended December 31, 2020: Balance at December 31, 2019 $ — Issuance of warrant 2,325 Change in fair value 5,676 Reclassification to equity (8,001 ) Balance at December 31, 2020 $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2020
Marketable Securities [Abstract]
Summary of Marketable Securities	Marketable securities at December 31, 2020 consisted of the following: Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value U.S. Treasury securities $ 189,949 $ 13 $ — $ 189,962

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	Property and equipment as of December 31, 2020 and 2019 consisted of the following (in thousands): As of December 31, 2020 2019 Laboratory equipment $ 7,207 $ 6,766 Furniture and fixtures 805 797 Leasehold improvements 541 520 Computer equipment 223 167 Office equipment 179 167 Total 8,955 8,417 Less: accumulated depreciation (5,632 ) (3,954 ) Property and equipment, net $ 3,323 $ 4,463
Summary of Depreciation Expense Related to Property and Equipment	Depreciation expense related to property and equipment for the years ended December 31, 2020 and 2019 is as follows (in thousands): Years Ended December 31, 2020 2019 Depreciation expense $ 1,617 $ 1,595

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Lessee Lease Description [Line Items]
Undiscounted Minimum Future Lease Payments Under Non-cancelable Leases	Future lease payments under non-cancelable leases as of December 31, 2020 for each of the years ending December 31 are as follows (in thousands): 2021 $ 2,272 2022 2,340 2023 2,410 2024 2,483 2025 2,557 Thereafter 6,277 Total undiscounted lease payments 18,339 Less: imputed interest (5,471 ) Total operating lease liability at December 31, 2020 $ 12,868
Watertown Lease
Lessee Lease Description [Line Items]
Summary of Lease Costs	The elements of lease costs for the years ended December 31, 2020 and 2019 were as follows (in thousands): 2020 2019 Lease cost: Operating lease cost $ 2,550 $ 2,550 Variable lease cost 1,066 1,020 Total lease cost $ 3,616 $ 3,570 Other information: Operating cash flows for operating liabilities $ 2,206 $ 2,141 Remaining lease term 7.3 years 8.3 years Discount rate 10 % 10 %

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Payables And Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following as of December 31, 2020 and 2019 (in thousands): 2020 2019 Accrued research and development $ 3,799 $ 2,615 Accrued compensation and benefits 3,724 3,048 Accrued professional fees 1,532 728 Other 469 280 Total accrued expenses and other current liabilities $ 9,524 $ 6,671

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2020
Collaboration And License Agreements [Abstract]
Schedule of Financial Information Related to Collaboration and License Agreements	Financial information related to the collaboration and license agreements consisted of the following as of and for the year ended December 31, 2020 (in thousands): Accounts Receivable Collaboration Revenue Deferred Revenue, Current Deferred Revenue, Net of Current Deferred Revenue, Total Roche Agreement $ 750 $ 9,051 $ 11,238 $ 26,991 $ 38,229 Biogen License Agreement 776 9,913 13,965 26,026 39,991 Calico License Agreement 2,958 14,231 2,400 600 3,000 $ 4,484 $ 33,195 $ 27,603 $ 53,617 $ 81,220 Financial information related to the collaboration and license agreements consisted of the following as of and for the year ended December 31, 2019 (in thousands): Description Accounts Receivable Collaboration Revenue Deferred Revenue, Current Deferred Revenue, Net of Current Deferred Revenue, Total Roche Agreement $ — $ 6,409 $ 12,164 $ 32,784 $ 44,948 Biogen License Agreement — 2,432 6,141 36,934 43,075 Calico License Agreement 4,348 12,540 2,400 3,000 5,400 $ 4,348 $ 21,381 $ 20,705 $ 72,718 $ 93,423
Schedule of Other Financial Information Related to Collaboration and License Agreements	Other financial information related to the collaboration and license agreements for the years ended December 31, 2020 and 2019 are (in thousands): 2020 2019 Revenue recognized that was included in the contract liability at the beginning of the period $ 17,570 $ 11,948 Revenue recognized from performance obligations fully or partially satisfied in previous periods 348 — Aggregate amount of the transaction price allocated to the performance obligations that are partially or fully unsatisfied as of the end of the reporting period 91,137 103,923

Long-term Debt and Warrant Li_2

Long-term Debt and Warrant Liability (Tables)	12 Months Ended
	Dec. 31, 2020
Long Term Debt And Warrant Liability [Abstract]
Summary of Anticipated Future Minimum Payments of Long-term Debt	Anticipated future minimum payments on long-term debt for the years ending December 31 are (in thousands): 2021 $ — 2022 — 2023 3,000 2024 9,500 Total minimum long-term debt payments 12,500 Less: Unamortized debt issuance costs, and debt discount related to warrant (2,448 ) Carrying value of long-term debt—related party at December 31, 2020 $ 10,052

Stockholder_s Equity (Tables)

Stockholder’s Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of Preferred Stock	As of December 31, 2019, Preferred Stock consisted of the following (in thousands, except share data): Preferred Stock Authorized Preferred Stock Issued and Outstanding Carrying Value Liquidation Value Common Stock Issuable Upon Conversion Series Seed Preferred Stock 4,000,000 4,000,000 $ 1,000 $ 1,000 474,298 Series A Preferred Stock 110,000,000 109,145,900 109,995 109,995 12,941,857 FF Preferred Stock 32,760,000 — — — — 146,760,000 113,145,900 $ 110,995 $ 110,995 13,416,155

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Stock-based Compensation Expense	Stock-based compensation expense for the year ended December 31, 2020 and 2019 was classified in the consolidated statement of operations and comprehensive loss as follows (in thousands): 2020 2019 Research and development $ 972 $ 395 General and administrative 2,460 1,247 Total stock-based compensation expense $ 3,432 $ 1,642
Summary of Stock Option Activity	The following table summarizes the stock option activity under the Company’s equity awards plans for the year ended December 31, 2020 : Number of Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2019 2,310,886 $ 4.42 8.11 $ 4,801 Granted 4,222,179 14.27 Exercised (281,584 ) 3.15 Forfeited/expired (1,222,117 ) 4.58 Outstanding as of December 31, 2020 5,029,364 $ 12.72 9.25 $ 102,635 Exercisable as of December 31, 2020 455,633 $ 4.28 7.34 $ 13,144 Vested and expected to vest as of December 31, 2020 5,029,364 $ 12.72 9.25 $ 102,635 Other information related to the option activity of the Company is as follows for the years ended December 31, 2020 and 2019: 2020 2019 Weighted-average fair value of options granted $ 9.24 $ 4.13 Intrinsic value of options exercised (in thousands) $ 2,587 $ 337
Summary of Significant Assumptions Used in the Black-scholes Pricing Model to Determine the Fair Value of Stock Options Granted	The following table summarizes assumptions used in the Black-Scholes option pricing model to determine the fair value of stock options granted to employees for the years ended December 31, 2020 and 2019: 2020 2019 Expected option life (years) 5.23 - 6.35 6.35 Risk-free interest rate 0.32% - 0.57% 1.71% - 2.36% Expected volatility 69.54% - 83.76% 65.50% - 76.80% Expected dividend yield 0.00% 0.00%

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Summary of Income Tax (Benefit) Expense	Income tax (benefit) expense consists of the following for the years ended December 31, 2020 and 2019 (in thousands): 2020 2019 Current tax provision: Current federal provision $ (673 ) $ 669 Current state provision 47 135 Total current provision (626 ) 804 Deferred tax provision: Deferred federal provision — — Deferred state provision — — Total tax provision $ (626 ) $ 804
Summary of Reconciliation of Expected Income Tax (Benefit) Expense	A reconciliation of the expected income tax (benefit) expense computed at the statutory federal rate to income taxes as reflected in the consolidated financial statements is as follows for the years ended December 31, 2020 and 2019: 2020 2019 Income tax benefit computed at federal statutory tax rate 21.0 % 21.0 % Stock-based compensation (0.1 )% (0.4 )% State tax—net of federal 8.1 % 6.6 % State credits 1.2 % 0.6 % Federal credits 3.5 % 1.1 % Valuation allowance (34.1 )% (32.1 )% Rate change 3.1 % (0.1 )% Net operating loss carryback benefits 1.0 % 0.0 % Tax attributes true up due to net operating loss carryback (1.0 )% 0.0 % Other permanent differences (1.8 )% 0.9 % Total 0.9 % (2.4 )%
Summary of Significant Components of Deferred Tax Assets and Deferred Tax Liabilities	Deferred income taxes reflect the net tax effects of (a) temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and (b) operating losses and tax credit carryforwards. Significant components of the Company’s deferred tax assets and deferred tax liabilities are as follows as of December 31, 2020 and 2019 (in thousands): 2020 2019 Deferred tax assets: Capitalized start-up costs $ 1,075 $ 1,151 Operating lease liability 3,859 3,821 Stock-based compensation 1,344 542 Net operating losses 19,399 575 R&D and investment tax credits 5,578 441 Deferred revenue 23,157 25,271 Other 168 — Total gross deferred tax assets 54,580 31,801 Deferred tax liabilities: Right-of-use asset (3,967 ) (4,017 ) Fixed assets (744 ) (726 ) Unrealized gain/loss (3 ) Less: valuation allowance (49,866 ) (27,058 ) Net deferred taxes $ — $ —

Loss Per Share (Tables)

Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Computation of Diluted Net Loss Per Share Attributable to Common Stockholders	2020 2019 Series Seed Preferred Stock — 474,298 Series A Preferred Stock — 12,941,857 Options to purchase common stock 5,029,364 2,310,886 Warrant to purchase common stock 338,784 — 5,368,148 15,727,041
Schedule of Basic and Diluted Loss Per Share	All redeemable, convertible preferred stock, including those that were outstanding as of December 31, 2019, as shown above, were converted to shares of the Company’s common and effected for a one-for-8.4335 reverse stock split. Basic and diluted loss per share is computed by dividing net loss attributable to common stockholders by the weighted-average common shares outstanding for the years ended December 31, 2020 and 2019 (in thousands, except share and per share data): 2020 2019 Numerator: Net loss $ (66,335 ) $ (34,099 ) Accrual of preferred stock dividends — (8,468 ) Net loss attributable to common stockholders—basic and diluted $ (66,335 ) $ (42,567 ) Denominator: Weighted-average common stock outstanding—basic and diluted 11,370,328 1,371,905 Net loss per share attributable to common stockholders—basic and diluted $ (5.83 ) $ (31.03 )

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands	Oct. 06, 2020USD ($)shares$ / shares	Sep. 25, 2020shares	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)shares
Class Of Stock [Line Items]
Net loss | $				$ 66,335	$ 34,099
Accumulated deficit | $				183,823	$ 117,488
Outstanding shares of preferred stock automatically converted | shares					13,416,155
Underwriting discount | $				14,700
Expenses | $				4,500
Cash, cash equivalents and marketable securities | $				$ 371,700
Reverse stock split				one-for-8.4335
Series B Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Shares issued price per share | $ / shares				$ 1.05
Expenses | $			$ 4,500
Warrant issued to purchase shares | shares		2,857,142
Initial Public Offering
Class Of Stock [Line Items]
Initial public offering closing date	Oct. 6, 2020
Outstanding shares of preferred stock automatically converted | shares	30,355,379
Common Stock
Class Of Stock [Line Items]
Issued shares of common stock | shares				11,040,000
Common Stock | Warrant Exercisable
Class Of Stock [Line Items]
Number of warrants converted into shares | shares		338,784
Common Stock | Initial Public Offering
Class Of Stock [Line Items]
Initial public offering closing date	Oct. 6, 2020
Issued shares of common stock | shares	11,040,000
Shares issued price per share | $ / shares	$ 19
Outstanding shares of preferred stock automatically converted | shares	30,355,379
Net proceeds including exercise in full of underwriters option to purchase additional shares | $	$ 191,200
Underwriting discount | $	14,700
Expenses | $	$ 3,900
Common Stock | Initial Public Offering | Warrant Exercisable
Class Of Stock [Line Items]
Number of warrants converted into shares | shares	338,784
Underwriters for IPO Exercised in full Overallotment Option | Common Stock | Initial Public Offering
Class Of Stock [Line Items]
Issued shares of common stock | shares	1,440,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020USD ($)SEGMENT	Dec. 31, 2019USD ($)
Accounting Policies [Abstract]
Number of operating segments | SEGMENT	1
Impairment of long-lived assets to be disposed of | $	$ 0	$ 0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Depreciation on Equipment Calculated Using Straight-Line Method Over Estimated Useful Lives of Assets (Details)	12 Months Ended
	Dec. 31, 2020
Laboratory Equipment
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	5 years
Computer Equipment
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	3 years
Office Equipment, Furniture and Fixtures
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	5 years
Leasehold Improvements
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	Lesser of useful life or remaining lease term

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Marketable securities
Total assets	$ 370,040	$ 80,902
Money Market Funds
Cash equivalents
Money market funds	180,078	80,902
U.S. Treasury Securities
Marketable securities
U.S. Treasury securities	189,962
Level 1
Marketable securities
Total assets	180,078	80,902
Level 1 | Money Market Funds
Cash equivalents
Money market funds	180,078	$ 80,902
Level 2
Marketable securities
Total assets	189,962
Level 2 | U.S. Treasury Securities
Marketable securities
U.S. Treasury securities	$ 189,962

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	Oct. 06, 2020shares	Sep. 25, 2020shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of warrants exercised | shares			0
Fair value, assets, level 1 to level 2 transfers, amount			$ 0	$ 0
Fair value, assets, level 2 to level 1 transfers, amount			0	0
Fair value, liabilities, level 1 to level 2 transfers, amount			0	0
Fair value, liabilities, level 2 to level 1 transfers, amount			0	0
Fair value, assets, level 1 to level 3 transfers, amount			0	0
Fair value, assets, level 3 to level 1 transfers, amount			0	0
Fair value, liabilities, level 1 to level 3 transfers, amount			0	0
Fair value, liabilities, level 3 to level 1 transfers, amount			0	0
Fair value, assets, level 2 to level 3 transfers, amount			0	0
Fair value, assets, level 3 to level 2 transfers, amount			0	0
Fair value, liabilities, level 2 to level 3 transfers, amount			0	0
Fair value, liabilities, level 3 to level 2 transfers, amount			$ 0	$ 0
Common Stock | Warrant Exercisable
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of warrants converted into shares | shares		338,784
Initial Public Offering | Common Stock | Warrant Exercisable
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of warrants converted into shares | shares	338,784

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assumptions to Determine Fair Value of Warrant (Details)	Oct. 06, 2020$ / shares
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Stock price	$ 26.96
Exercise price	$ 8.86
Expected term (in years)	9 years 9 months
Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.7500
Risk-free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.0076

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Changes in Level 3 Instruments, Redeemable Convertible Preferred Stock Warrant (Details) - Redeemable Convertible Preferred Stock Warrant - Level 3	12 Months Ended
	Dec. 31, 2020USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Issuance of warrant	$ 2,325
Change in fair value	5,676
Reclassification to equity	$ (8,001)

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Details) - U.S. Treasury Securities $ in Thousands	Dec. 31, 2020USD ($)
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 189,949
Gross Unrealized Gains	13
Fair Value	$ 189,962

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Marketable Securities [Abstract]
Other-than-temporary impairment losses	$ 0
Contractual maturity dates of marketable securities	less than one year
Marketable securities		$ 0

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 8,955	$ 8,417
Less: accumulated depreciation	(5,632)	(3,954)
Property and equipment, net	3,323	4,463
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	7,207	6,766
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	805	797
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	541	520
Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	223	167
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 179	$ 167

Property and Equipment - Summ_2

Property and Equipment - Summary of Depreciation Expense Related to Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 1,617	$ 1,595

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2017	Dec. 31, 2020	Dec. 31, 2019
Lessee Lease Description [Line Items]
Right-of-use assets		$ 13,229	$ 14,453
Liabilities under lease		12,868
Watertown Lease
Lessee Lease Description [Line Items]
Right-of-use assets		16,700
Liabilities under lease		15,100
Construction costs		$ 1,500
Watertown Lease | Office and Laboratory Space
Lessee Lease Description [Line Items]
Lease commencement date	2018-04
Lessee operating lease, description		In July 2017, the Company entered into a lease of office and laboratory space for its headquarters in Watertown, Massachusetts, or the Watertown Lease. The Watertown Lease has a non-cancelable term of ten years with an option to extend for one additional five-year period and is subject to rent escalation throughout the term. Additionally, the Watertown Lease required the Company to provide collateral in the amount of $2.6 million, which is recorded as restricted cash on the accompanying consolidated balance sheets. The Watertown Lease commenced in April 2018, with rent commencing in May 2018.
Rent commencing date	2018-05
Watertown Lease | Restricted Cash
Lessee Lease Description [Line Items]
Lease collateral amount		$ 2,600

Leases - Summary of Lease Costs

Leases - Summary of Lease Costs (Details) - Watertown Lease - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease cost:
Operating lease cost	$ 2,550	$ 2,550
Variable lease cost	1,066	1,020
Total lease cost	3,616	3,570
Other information:
Operating cash flows for operating liabilities	$ 2,206	$ 2,141
Remaining lease term	7 years 3 months 18 days	8 years 3 months 18 days
Discount rate	10.00%	10.00%

Leases - Undiscounted Minimum F

Leases - Undiscounted Minimum Future Lease Payments Under Non-cancelable Leases (Details) $ in Thousands	Dec. 31, 2020USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2021	$ 2,272
2022	2,340
2023	2,410
2024	2,483
2025	2,557
Thereafter	6,277
Total undiscounted lease payments	18,339
Less: imputed interest	(5,471)
Total operating lease liability at December 31, 2020	$ 12,868

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued research and development	$ 3,799	$ 2,615
Accrued compensation and benefits	3,724	3,048
Accrued professional fees	1,532	728
Other	469	280
Total accrued expenses and other current liabilities	$ 9,524	$ 6,671

Collaboration and License Agr_3

Collaboration and License Agreements - Schedule of Financial Information Related to Collaboration and License Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts Receivable	$ 4,484	$ 4,348
Collaboration Revenue	33,195	21,381
Deferred Revenue, Current	27,603	20,705
Deferred Revenue, Net of Current	53,617	72,718
Deferred Revenue, Total	81,220	93,423
Roche Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts Receivable	750
Collaboration Revenue	9,051	6,409
Deferred Revenue, Current	11,238	12,164
Deferred Revenue, Net of Current	26,991	32,784
Deferred Revenue, Total	38,229	44,948
Biogen License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts Receivable	776
Collaboration Revenue	9,913	2,432
Deferred Revenue, Current	13,965	6,141
Deferred Revenue, Net of Current	26,026	36,934
Deferred Revenue, Total	39,991	43,075
Calico License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts Receivable	2,958	4,348
Collaboration Revenue	14,231	12,540
Deferred Revenue, Current	2,400	2,400
Deferred Revenue, Net of Current	600	3,000
Deferred Revenue, Total	$ 3,000	$ 5,400

Collaboration and License Agr_4

Collaboration and License Agreements - Schedule of Other Financial Information Related to Collaboration and License Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Revenue recognized that was included in the contract liability at the beginning of the period	$ 17,570	$ 11,948
Revenue recognized from performance obligations fully or partially satisfied in previous periods	348
Aggregate amount of the transaction price allocated to the performance obligations that are partially or fully unsatisfied as of the end of the reporting period	$ 91,137	$ 103,923

Collaboration and License Agr_5

Collaboration and License Agreements - Additional Information (Details)	Dec. 22, 2018USD ($)Target	Jun. 30, 2020USD ($)	Dec. 31, 2018USD ($)TargetProtein	Mar. 31, 2016USD ($)	Dec. 31, 2020USD ($)TargetExchangeMaterialRightPerformanceobligationTargetProtein	Dec. 31, 2019USD ($)
Original Roche Agreement | Roche JRC | Research and Development License
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Nonrefundable upfront payment and additional fees				$ 15,000,000
Roche Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of potential targets | Target	6
Number of target nominated as of the execution of the Restated Roche Agreement | Target	3
Number of target not nominated as of the execution of the Restated Roche Agreement | Target	3
Additional upfront consideration received	$ 40,000,000
Annual research plan payments receivables	1,000,000
Collaboration description					The Company has control over the committee and may terminate the Roche Agreement on a target-by-target or product-by-product basis under several scenarios, upon at least 90 days’ prior written notice.
Roche Agreement | Progressed Through Clinical Trials
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise fees	20,000,000
Roche Agreement | Minimum | Progressed Through Clinical Trials
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise fees	7,000,000
Roche Agreement | Maximum | Research, Development and Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive	275,000,000
Roche Agreement | Maximum | One-Time Sales-Based Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive	150,000,000
Roche Agreement | Maximum | Progressed Through Clinical Trials
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise fees	12,000,000
Roche Agreement | Lead Series Identification Achievement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fees	2,000,000
Roche Agreement | Good Laboratory Practice (“GLP”) Toxicology (“Tox”) Study Phase
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fees	$ 3,000,000
Roche Agreement Accounting
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of potential targets | Target					6
Upfront payment					$ 40,000,000
Expected research plan funding payments					13,500,000
Remaining deferred revenue					$ 6,400,000
Number of initial targets | Target					3
Number of additional targets | Target					3
Number of targets | Target					6
Number of exchanges | Exchange					6
Number of additional targets | Target					3
Number of performance obligation | Performanceobligation					12
Amount of expected research plan funding payments of per active target per year					$ 1,000,000
Roche Agreement Accounting | Option to License
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of material rights | MaterialRight					3
Roche Agreement Accounting | Option to Initiate Research Plan
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of additional targets | Target					3
Number of material rights | MaterialRight					3
Roche Agreement Accounting | Research Services Performance Obligations
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligation | Performanceobligation					3
Roche Agreement Accounting | Commercial License for Six Targets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targets | Target					6
Number of performance obligation | Performanceobligation					6
Roche Agreement Accounting | Research Services for Uninitiated Three Targets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targets | Target					3
Number of performance obligation | Performanceobligation					3
Roche Agreement Accounting | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount of expected research plan funding payments of per target					$ 3,000,000
Roche Agreement Accounting | Target Two
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment received					2,000,000
Transaction price allocated to performance obligations					61,900,000
Roche Agreement Accounting | Targets 1-3
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligations					$ 29,000,000
Roche Agreement Accounting | Targets 3
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of material rights | MaterialRight					3
Transaction price allocated to performance obligations					$ 4,100,000
Roche Agreement Accounting | Targets 4-6
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligations					$ 28,800,000
Biogen License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of additional targets | Target					2
Number of targets | Target					5
Number of performance obligation | Performanceobligation					1
Milestone payment received		$ 4,000,000
Agreement date			2018-12
Research agreement, period			54 months		54 months
Additional payment on extension of contract			$ 62,500,000
Nonrefundable upfront payment					$ 45,000,000
Written notice period for termination of agreement					90 days
Revenue recognized					$ 2,800,000	$ 500,000
Biogen License Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period for termination of agreement					90 days
Biogen License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targeted protein degradation | Protein			5
Additional targets for development | Target			5
Biogen License Agreement | Maximum | One-Time Sales-Based Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received					$ 26,000,000
Biogen License Agreement | Maximum | Research And Development Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received					35,000,000
Calico License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment					$ 5,000,000
Number of targets | Target					5
Number of performance obligation | Performanceobligation					1
Research term					5 years
Annual Payments					$ 5,000,000
Cash consideration received for milestone revenue						2,000,000
Additional consideration received in cash for target initiation fees						0
Accounts receivable for additional target initiation fees						$ 1,000,000
Contractual term					5 years
Calico License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of target proteins | TargetProtein					5
Calico License Agreement | Maximum | One-Time Sales-Based Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received					$ 65,000,000
Calico License Agreement | Maximum | Potential Research, Development and Commercial Milestone Payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received					$ 132,000,000

Long-term Debt and Warrant Li_3

Long-term Debt and Warrant Liability - Additional Information (Details)	Oct. 06, 2020USD ($)$ / sharesshares	Sep. 25, 2020	Jun. 05, 2020USD ($)	Dec. 31, 2020USD ($)$ / sharesshares	Jun. 30, 2020USD ($)
Long Term Debt And Warrant Liability [Line Items]
Exercise price per share | $ / shares	$ 8.86
Change in fair value of warrant liability				$ 5,676,000
Reverse stock split				one-for-8.4335
Stock split conversion ratio	0.118574732	0.118574732		0.118574732
Outstanding long term debt				$ 12,500,000
Long term debt				10,052,000
Initial Public Offering
Long Term Debt And Warrant Liability [Line Items]
Exercise price per share | $ / shares	$ 8.86
Change in fair value of warrant liability	$ 8,000,000
Initial Public Offering | Other Income (Expense)
Long Term Debt And Warrant Liability [Line Items]
Change in fair value of warrant liability				5,700,000
Maximum | Initial Public Offering
Long Term Debt And Warrant Liability [Line Items]
Warrant issued to purchase shares | shares	338,784
Tranche Two
Long Term Debt And Warrant Liability [Line Items]
Amount withdrawn				$ 7,500,000
Expiration date				Jun. 30, 2021
Term Loan | Series B Preferred Stock
Long Term Debt And Warrant Liability [Line Items]
Exercise price per share | $ / shares				$ 1.05
Change in fair value of warrant liability				$ 2,300,000
Term Loan | Maximum | Series B Preferred Stock
Long Term Debt And Warrant Liability [Line Items]
Warrant issued to purchase shares | shares				2,857,142
Credit Agreement with Perceptive Life Sciences Master Fund LTD | Term Loan
Long Term Debt And Warrant Liability [Line Items]
Description of Variable Rate Basis				greater of LIBOR or 1.75%, plus 9.50%
Applicable margin rate			9.50%
Date until which interest only payments are made			Dec. 5, 2022
Maturity date			Jun. 5, 2024
Percentage of principal payments until maturity			2.00%
Prepayment fee			$ 5,000,000	$ 4,200,000
Issuance cost in connection with entry into Credit Agreement			500,000
Credit Agreement with Perceptive Life Sciences Master Fund LTD | Term Loan | Maximum
Long Term Debt And Warrant Liability [Line Items]
Aggregate principal amount			20,000,000
Credit Agreement with Perceptive Life Sciences Master Fund LTD | Term Loan | Minimum
Long Term Debt And Warrant Liability [Line Items]
Balance to be maintained in bank account while debt is outstanding			3,000
Credit Agreement with Perceptive Life Sciences Master Fund LTD | Term Loan | Tranche One
Long Term Debt And Warrant Liability [Line Items]
Aggregate principal amount			12,500,000
Amount withdrawn					$ 12,500,000
Credit Agreement with Perceptive Life Sciences Master Fund LTD | Term Loan | Tranche Two
Long Term Debt And Warrant Liability [Line Items]
Aggregate principal amount			$ 7,500,000

Long-term Debt and Warrant Li_4

Long-term Debt and Warrant Liability - Summary of Anticipated Future Minimum Payments of Long-term Debt (Details) $ in Thousands	Dec. 31, 2020USD ($)
Long Term Debt By Maturity [Abstract]
2023	$ 3,000
2024	9,500
Total minimum long-term debt payments	12,500
Less: Unamortized debt issuance costs, and debt discount related to warrant	(2,448)
Carrying value of long-term debt—related party at December 31, 2020	$ 10,052

Stockholder's Equity - Addition

Stockholder's Equity - Additional Information (Details) $ / shares in Units, $ in Thousands	Oct. 06, 2020shares	Sep. 25, 2020	Jul. 31, 2020USD ($)shares	Jun. 30, 2020USD ($)shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019$ / sharesshares
Stockholders Equity [Line Items]
Reverse stock split					one-for-8.4335
Stock split conversion ratio	0.118574732	0.118574732			0.118574732
Common stock, par value per share | $ / shares					$ 0.0001	$ 0.0001
Common stock voting right					one vote for each share
Proceeds from issuance of convertible preferred stock | $					$ 145,525
Redeemable convertible preferred stock, shares issued						113,145,900
Stock issuance costs | $					$ 4,500
Outstanding shares of preferred stock converted						13,416,155
Preferred stock, outstanding					0	0
Initial Public Offering
Stockholders Equity [Line Items]
Initial public offering closing date	Oct. 6, 2020
Outstanding shares of preferred stock converted	30,355,379
Number of preferred stock converted in to one common stock	8.4335
Preferred stock, outstanding	0
Series Seed Preferred Stock
Stockholders Equity [Line Items]
Redeemable convertible preferred stock, par value per share | $ / shares					$ 0.0005
Redeemable convertible preferred stock, shares issued						4,000,000
Outstanding shares of preferred stock converted						474,298
Series A Preferred Stock
Stockholders Equity [Line Items]
Redeemable convertible preferred stock, par value per share | $ / shares					0.0005
Redeemable convertible preferred stock, shares issued						109,145,900
Outstanding shares of preferred stock converted						12,941,857
Series B Convertible Preferred Stock
Stockholders Equity [Line Items]
Redeemable convertible preferred stock, par value per share | $ / shares					$ 0.0005
Proceeds from issuance of convertible preferred stock | $			$ 4,500	$ 145,500	$ 150,000
Redeemable convertible preferred stock, shares issued			4,285,714	138,571,428	142,857,142
Shares issued price per share | $ / shares					$ 1.05
Stock issuance costs | $				$ 4,500

Stockholder's Equity - Schedule

Stockholder's Equity - Schedule of Preferred Stock (Details) $ in Thousands	Dec. 31, 2019USD ($)shares
Class Of Stock [Line Items]
Preferred Stock Authorized	146,760,000
Preferred Stock Issued	113,145,900
Preferred Stock Outstanding	113,145,900
Carrying Value | $	$ 110,995
Liquidation Value | $	$ 110,995
Common Stock Issuable Upon Conversion	13,416,155
Series Seed Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	4,000,000
Preferred Stock Issued	4,000,000
Preferred Stock Outstanding	4,000,000
Carrying Value | $	$ 1,000
Liquidation Value | $	$ 1,000
Common Stock Issuable Upon Conversion	474,298
Series A Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	110,000,000
Preferred Stock Issued	109,145,900
Preferred Stock Outstanding	109,145,900
Carrying Value | $	$ 109,995
Liquidation Value | $	$ 109,995
Common Stock Issuable Upon Conversion	12,941,857
FF Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	32,760,000

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Thousands	Dec. 30, 2020	Mar. 03, 2020	Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2021	Sep. 30, 2020	Dec. 28, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, common stock shares authorized			150,000,000	21,343,452
Stock-based compensation, common stock shares outstanding			43,059,632	1,426,641
Payments for repurchase of common stock		$ 100	$ 194	$ 30
Payments for relinquishment of right to purchase common stock upon exercise of stock options		$ 700
2015 Incentive Stock Option and Grant Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, common stock shares reserved for issuance			8,880,367				2,525,327
Stock-based compensation, options vesting description			Options generally vest over a period of five or eight years with a cliff vesting at one year and quarterly vesting thereafter and options that lapse or are forfeited are available to be granted again.
Contractual life of options from the date of grant			10 years
2015 Incentive Stock Option and Grant Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, options vesting period			5 years
2015 Incentive Stock Option and Grant Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, options vesting period			8 years
2020 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, common stock shares reserved for issuance			8,880,367			6,567,144
Stock-based compensation, common stock shares available for issuance			3,851,003
Percentage of outstanding shares of common stock	5.00%
Unrecognized compensation costs			$ 37,500
Expected to be recognized over a weighted average period			3 years 8 months 12 days
2020 Stock Option and Incentive Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, common stock shares authorized					2,152,981
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, common stock shares reserved for issuance						437,809
Percentage of outstanding shares of common stock	1.00%
Stock-based compensation, common stock shares outstanding	656,714
Maximum authorized payroll deduction percentage of eligible compensation for eligible employees			15.00%
Shares issued under employee stock purchase plan			0
2020 Employee Stock Purchase Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation, common stock shares authorized					430,596

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 3,432	$ 1,642
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	972	395
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,460	$ 1,247

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Details) - 2020 Stock Option and Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options, Outstanding as of December 31, 2019	2,310,886
Number of options, Granted	4,222,179
Number of options, Exercised	(281,584)
Number of options, Forfeited/expired	(1,222,117)
Number of options, Outstanding as of December 31, 2020	5,029,364	2,310,886
Number of options, Exercisable as of December 31, 2020	455,633
Number of options, Vested and expected to vest as of December 31, 2020	5,029,364
Weighted-average exercise price, Outstanding as of December 31, 2019	$ 4.42
Weighted-average exercise price, Granted	14.27
Weighted-average exercise price, Exercised	3.15
Weighted-average exercise price, Forfeited/expired	4.58
Weighted-average exercise price, Outstanding as of December 31, 2020	12.72	$ 4.42
Weighted-average exercise price, Exercisable as of December 31, 2020	4.28
Weighted-average exercise price, Vested and expected to vest as of December 31, 2020	$ 12.72
Weighted average remaining contractual term (in years), Options outstanding	9 years 3 months	8 years 1 month 9 days
Weighted average remaining contractual term (in years), Options exercisable	7 years 4 months 2 days
Weighted average remaining contractual term (in years), Vested and expected to vest	9 years 3 months
Aggregate intrinsic value, Outstanding as of December 31, 2019	$ 4,801
Aggregate intrinsic value, Outstanding as of December 31, 2020	102,635	$ 4,801
Aggregate intrinsic value, Exercisable as of December 31, 2020	13,144
Aggregate intrinsic value, Vested and expected to vest as of December 31, 2020	$ 102,635

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Other Information Related to the Option Activity (Details) - 2020 Stock Option and Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average fair value of options granted	$ 9.24	$ 4.13
Intrinsic value of options exercised (in thousands)	$ 2,587	$ 337

Stock-based Compensation - Su_3

Stock-based Compensation - Summary of Significant Assumptions Used in the Black-scholes Pricing Model to Determine the Fair Value of Stock Options Granted (Details) - 2020 Stock Option and Incentive Plan	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected option life (years)		6 years 4 months 6 days
Risk-free interest rate, Minimum	0.32%	1.71%
Risk-free interest rate, Maximum	0.57%	2.36%
Expected volatility, Minimum	69.54%	65.50%
Expected volatility, Maximum	83.76%	76.80%
Expected dividend yield	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected option life (years)	5 years 2 months 23 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected option life (years)	6 years 4 months 6 days

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax (Benefit) Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Current tax provision:
Current federal provision	$ (673)	$ 669
Current state provision	47	135
Total current provision	(626)	804
Deferred tax provision:
Total tax provision	$ (626)	$ 804

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Expected Income Tax (Benefit) Expense (Benefit) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax benefit computed at federal statutory tax rate	21.00%	21.00%
Stock-based compensation	(0.10%)	(0.40%)
State tax—net of federal	8.10%	6.60%
State credits	1.20%	0.60%
Federal credits	3.50%	1.10%
Valuation allowance	(34.10%)	(32.10%)
Rate change	3.10%	(0.10%)
Net operating loss carryback benefits	1.00%	0.00%
Tax attributes true up due to net operating loss carryback	(1.00%)	0.00%
Other permanent differences	(1.80%)	0.90%
Total	0.90%	(2.40%)

Income Taxes - Summary of Signi

Income Taxes - Summary of Significant Components of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Capitalized start-up costs	$ 1,075	$ 1,151
Operating lease liability	3,859	3,821
Stock-based compensation	1,344	542
Net operating losses	19,399	575
R&D and investment tax credits	5,578	441
Deferred revenue	23,157	25,271
Other	168
Total gross deferred tax assets	54,580	31,801
Deferred tax liabilities:
Right-of-use asset	(3,967)	(4,017)
Fixed assets	(744)	(726)
Unrealized gain/loss	(3)
Less: valuation allowance	$ (49,866)	$ (27,058)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Income Tax [Line Items]
Deferred tax assets, valuation allowance	$ 49,866,000	$ 27,058,000
Net valuation allowance increases	22,800,000
Federal net operating loss carryforwards	$ 58,800,000	0
Tax credit carryforward, description	The Tax Cuts and Jobs Act, or TCJA, which was enacted in December 2017, will generally allow federal losses generated after 2017 to be carried over indefinitely, but will generally limit the NOL deduction to the lesser of the NOL carryover or 80% of a corporation’s taxable income (subject to Section 382 of the Internal Revenue Code of 1986, as amended, or IRC).
Federal net operating loss carryforwards do not expire	$ 58,800,000
Refund due to anticipated carryback portion of net operating loss		600,000
Percentage of taxable income limitation under TCJA	0.80
State net operating loss carryforwards	$ 105,100,000	8,200,000
Accrued interest or penalties related to uncertain tax benefits	0	0
Tax benefit	(626,000)	804,000
Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”)
Income Tax [Line Items]
Tax benefit	$ (600,000)
Internal Revenue Service (IRS)
Income Tax [Line Items]
Net operating loss and tax credit carryforwards description	Under the provisions of the IRC, the net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%
Net operating loss carryforwards limited and expire due to ownership changes	$ 0
Domestic Tax Authority | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credit carryforwards	4,700,000	400,000
State and Local Jurisdiction | Research Tax Credit Carryforward
Income Tax [Line Items]
Tax credit carryforwards	$ 1,100,000	$ 100,000

Loss Per Share - Schedule of Co

Loss Per Share - Schedule of Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	5,368,148	15,727,041
Series Seed Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities		474,298
Series A Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities		12,941,857
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	5,029,364	2,310,886
Warrant to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	338,784

Loss Per Share - Additional Inf

Loss Per Share - Additional Information (Details)	Oct. 06, 2020	Sep. 25, 2020	Dec. 31, 2020
Earnings Per Share [Abstract]
Reverse stock split			one-for-8.4335
Stock split conversion ratio	0.118574732	0.118574732	0.118574732

Loss Per Share - Schedule of Ba

Loss Per Share - Schedule of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss	$ (66,335)	$ (34,099)
Accrual of preferred stock dividends		(8,468)
Net loss attributable to common stockholders—basic and diluted	$ (66,335)	$ (42,567)
Denominator:
Weighted-average common stock outstanding—basic and diluted	11,370,328	1,371,905
Net loss per share attributable to common stockholders—basic and diluted	$ (5.83)	$ (31.03)

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Details) - 401(k) Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan Disclosure [Line Items]
Pre-tax compensation of employees	90.00%
Percentage of employer discretion contribution	100.00%
Defined benefit plan, contributions by employer	$ 500	$ 400
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer discretionary contribution amount	$ 6,000