0001564590-21-041902 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2021	Jul. 30, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Trading Symbol	KYMR
Entity Registrant Name	KYMERA THERAPEUTICS, INC.
Entity Central Index Key	0001815442
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		51,039,817
Entity Shell Company	false
Entity File Number	001-39460
Entity Tax Identification Number	81-2992166
Entity Address, Address Line One	200 Arsenal Yards Blvd
Entity Address, Address Line Two	Suite 230
Entity Address, City or Town	Watertown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02472
City Area Code	857
Local Phone Number	285-5300
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 84,903	$ 31,004
Marketable securities (Note 4)	274,204	265,198
Accounts receivable—due from related parties		577
Contract assets—due from related parties	904	856
Prepaid expenses and other current assets	4,795	4,704
Total current assets	364,806	302,339
Marketable securities, non-current (Note 4)	45,305	162,531
Property and equipment, net (Note 6)	12,118	10,841
Right-of-use assets, operating leases	9,648	9,845
Other non-current assets	920	30
Restricted cash	1,589	1,589
Total assets	434,386	487,175
Current liabilities:
Accounts payable	8,177	4,368
Accrued expenses (Note 8)	14,668	10,330
Deferred revenue	82,263	92,552
Operating lease liabilities	2,425	2,572
Finance lease liabilities	1,038	689
Other current liabilities	114	106
Total current liabilities	108,685	110,617
Non-current liabilities
Deferred revenue, net of current portion	52,672	77,838
Operating lease liabilities, net of current portion	13,696	14,128
Finance lease liabilities, net of current portion	1,145	604
Other non-current liabilities	84	100
Total liabilities	176,282	203,287
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized as of June 30, 2021 and December 31, 2020; 0 shares issued or outstanding as of June 30, 2021 and December 31, 2020
Common stock, $0.0001 par value; 150,000,000 shares authorized at June 30, 2021 and December 31, 2020, 45,401,203 and 44,592,288 shares issued at June 30, 2021 and December 31, 2020, respectively; 45,327,681 and 44,482,186 shares outstanding at June 30, 2021 and December 31, 2020, respectively	5	4
Additional paid-in capital	424,599	412,777
Accumulated deficit	(166,500)	(128,765)
Accumulated other comprehensive loss		(128)
Total stockholders’ equity	258,104	283,888
Total liabilities and stockholders’ equity	$ 434,386	$ 487,175

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, authorized	150,000,000	150,000,000
Common stock, issued	45,401,203	44,592,288
Common Stock, outstanding	45,327,681	44,482,186

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Collaboration Revenue—from related parties	$ 18,519	$ 3,288	$ 37,221	$ 6,716
Revenue from Contract with Customer, Product and Service [Extensible List]	kymr:CollaborationsRevenueMember	kymr:CollaborationsRevenueMember	kymr:CollaborationsRevenueMember	kymr:CollaborationsRevenueMember
Operating expenses:
Research and development	$ 35,220	$ 13,819	$ 61,181	$ 25,935
General and administrative	8,029	3,661	13,939	6,220
Total operating expenses	43,249	17,480	75,120	32,155
Loss from operations	(24,730)	(14,192)	(37,899)	(25,439)
Other income (expense):
Interest Income	98	228	217	577
Interest Expense	(28)	(25)	(53)	(59)
Total other income:	70	203	164	518
Net loss	(24,660)	(13,989)	(37,735)	(24,921)
Other comprehensive loss:
Unrealized gain (loss) on marketable securities	14	(189)	128	25
Total comprehensive loss	(24,646)	(14,178)	(37,607)	(24,896)
Reconciliation of net loss to net loss attributable to common stockholders:
Net Loss	(24,660)	(13,989)	(37,735)	(24,921)
Deemed dividend from exchange of convertible preferred stock				(9,050)
Net loss attributable to common stockholders	$ (24,660)	$ (13,989)	$ (37,735)	$ (33,971)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.55)	$ (6.98)	$ (0.84)	$ (17.18)
Weighted average common stock outstanding, basic and diluted	45,094,238	2,002,825	44,873,083	1,977,720

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - USD ($) $ in Thousands	Total	Series Seed Convertible Preferred Stock	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Series B-1 Convertible Preferred Stock	Series C Convertible Preferred Stock	Common Stock	Additional Paid In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2019		3,000,000	14,720,126	14,827,580	3,059,695
Temporary Equity, Beginning Balance at Dec. 31, 2019		$ 5,900	$ 29,237	$ 59,918	$ 14,025
Beginning Balance at Dec. 31, 2019	$ (74,406)							$ 2,044	$ (76,456)	$ 6
Beginning Balance, Shares at Dec. 31, 2019							1,929,516
Vesting of Series A Preferred Stock in connection with collaboration arrangement (Note 5)			$ 222
Vesting of Series A Preferred Stock in connection with collaboration arrangement (Note 5), Shares			110,788
Issuance of Preferred Stock, net of issuance costs				$ 4,800		$ 88,180
Issuance of Preferred Stock, net of issuance costs, Shares				1,182,265		13,539,141
Exchange of Series A Convertible Preferred Stock for Series C Preferred Convertible Preferred Stock	(9,050)							(2,333)	(6,717)
Temporary Equity, Exchange of Series A Convertible Preferred Stock for Series C Preferred Convertible Preferred Stock, Shares			(1,988,802)			1,988,802
Temporary Equity, Exchange of Series A Convertible Preferred Stock for Series C Preferred Convertible Preferred Stock			$ (3,950)			$ 13,000
Exercise of stock options	28							28
Exercise of stock options, Shares							16,106
Vesting restricted stock, Shares							90,334
Stock-based compensation expense	1,035							1,035
Unrealized gain on marketable securities	25									25
Net Loss	(24,921)								(24,921)
Ending Balance at Jun. 30, 2020	(107,289)							774	(108,094)	31
Temporary Equity, Ending Balance, Shares at Jun. 30, 2020		3,000,000	12,842,112	16,009,845	3,059,695	15,527,943
Temporary Equity, Ending Balance at Jun. 30, 2020		$ 5,900	$ 25,509	$ 64,718	$ 14,025	$ 101,180
Ending Balance, Shares at Jun. 30, 2020							2,035,956
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2019		3,000,000	14,720,126	14,827,580	3,059,695
Temporary Equity, Beginning Balance at Dec. 31, 2019		$ 5,900	$ 29,237	$ 59,918	$ 14,025
Beginning Balance at Dec. 31, 2019	(74,406)							2,044	(76,456)	6
Beginning Balance, Shares at Dec. 31, 2019							1,929,516
Ending Balance at Dec. 31, 2020	283,888						$ 4	412,777	(128,765)	(128)
Ending Balance, Shares at Dec. 31, 2020							44,482,186
Temporary Equity, Beginning Balance, Shares at Mar. 31, 2020		3,000,000	12,786,718	16,009,845	3,059,695	15,527,943
Temporary Equity, Beginning Balance at Mar. 31, 2020		$ 5,900	$ 25,398	$ 64,718	$ 14,025	$ 101,180
Beginning Balance at Mar. 31, 2020	(93,803)							82	(94,105)	220
Beginning Balance, Shares at Mar. 31, 2020							1,975,813
Vesting of Series A Preferred Stock in connection with collaboration arrangement (Note 5)			$ 111
Vesting of Series A Preferred Stock in connection with collaboration arrangement (Note 5), Shares			55,394
Exercise of stock options	28							28
Exercise of stock options, Shares							16,106
Vesting restricted stock, Shares							44,037
Stock-based compensation expense	664							664
Unrealized gain on marketable securities	(189)									(189)
Net Loss	(13,989)								(13,989)
Ending Balance at Jun. 30, 2020	(107,289)							774	(108,094)	31
Temporary Equity, Ending Balance, Shares at Jun. 30, 2020		3,000,000	12,842,112	16,009,845	3,059,695	15,527,943
Temporary Equity, Ending Balance at Jun. 30, 2020		$ 5,900	$ 25,509	$ 64,718	$ 14,025	$ 101,180
Ending Balance, Shares at Jun. 30, 2020							2,035,956
Beginning Balance at Dec. 31, 2020	283,888						$ 4	412,777	(128,765)	(128)
Beginning Balance, Shares at Dec. 31, 2020							44,482,186
Exercise of stock options	2,618						$ 1	2,617
Exercise of stock options, Shares							801,233
Vesting restricted stock, Shares							36,582
Issuance of shares under employee stock purchase plan	307							307
Issuance of shares under employee stock purchase plan, Shares							7,680
Stock-based compensation expense	8,898							8,898
Unrealized gain on marketable securities	128									128
Net Loss	(37,735)								(37,735)
Ending Balance at Jun. 30, 2021	258,104						$ 5	424,599	(166,500)
Ending Balance, Shares at Jun. 30, 2021							45,327,681
Beginning Balance at Mar. 31, 2021	275,247						$ 4	417,096	(141,840)	(13)
Beginning Balance, Shares at Mar. 31, 2021							44,879,376
Exercise of stock options	1,471						$ 1	1,470
Exercise of stock options, Shares							422,471
Vesting restricted stock, Shares							18,154
Issuance of shares under employee stock purchase plan	307							307
Issuance of shares under employee stock purchase plan, Shares							7,680
Stock-based compensation expense	5,726							5,726
Unrealized gain on marketable securities	13									$ 13
Net Loss	(24,660)								(24,660)
Ending Balance at Jun. 30, 2021	$ 258,104						$ 5	$ 424,599	$ (166,500)
Ending Balance, Shares at Jun. 30, 2021							45,327,681

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Series B Preferred Stock
Underwriting discounts, offering costs and issuance costs	$ 0	$ 0
Series C Preferred Stock
Underwriting discounts, offering costs and issuance costs	$ 320	$ 320

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities
Net loss	$ (37,735)	$ (24,921)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	8,898	1,035
Depreciation and amortization	1,037	776
Premiums and discounts on available-for-sale marketable securities	2,511
Non-cash research and development expense		222
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(91)	(2,182)
Receivables—due from related parties	(327)
Contract asset—due from related parties	856
Accounts payable	4,005	(372)
Accrued expenses and other current liabilities	4,092	3,136
Deferred revenue	(35,455)	(6,716)
Operating lease right-of-use assets	197	7,349
Operating lease liabilities	(579)	(1,796)
Other assets and liabilities	(743)
Net cash used in operating activities	(53,334)	(23,469)
Investing activities
Purchase of property and equipment, net	(790)	(5,250)
Purchases of investments	(46,164)	(110,527)
Maturities of investments	152,000	31,500
Net cash provided by (used in) investing activities	105,046	(84,277)
Financing activities
Proceeds from stock option exercises	2,618	29
Proceeds from employee stock purchase plan	307
Payments of offering costs in connection with initial public offering	(397)
Payments on finance leases	(341)	(293)
Net cash provided by financing activities	2,187	92,717
Net increase in cash, cash equivalents and restricted cash	53,899	(15,029)
Cash, cash equivalents and restricted cash at beginning of period	32,593	77,789
Cash, cash equivalents and restricted cash at end of period	86,492	62,760
Supplemental disclosure of cash flow activities
Cash paid for interest	54	65
Supplemental disclosure of noncash investing and financing activities
Property and equipment purchases included in accounts payable and accrued expenses	320	1,076
Purchase of property and equipment through finance lease	1,231
Offering costs included in accrued expenses	154
Supplemental disclosure of noncash operating activities
Tenant improvements included in other assets		833
Reduction of right-of-use asset and liability due to lease modification		2,161
Cash and cash equivalents	84,903	60,971
Restricted cash	$ 1,589	1,789
Series B Convertible Preferred Stock
Financing activities
Proceeds from the issuance of Convertible Preferred Stock, net of issuance costs		4,800
Series C Convertible Preferred Stock
Financing activities
Proceeds from the issuance of Convertible Preferred Stock, net of issuance costs		$ 88,181

Organization and Nature of Business

6 Months Ended

Jun. 30, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Nature of Business

1. Organization and Nature of Business

Kymera Therapeutics, Inc., together with its subsidiary Kymera Securities Corporation, is referred to on a consolidated basis as the “Company”. The Company is a biopharmaceutical company focused on discovering and developing small molecule therapeutics that selectively degrade disease-causing proteins by harnessing the body’s own natural cellular process, a method known as targeted protein degradation. The Company has devoted its efforts principally to research and development since formation. The Company has not yet completed product development, filed for or obtained regulatory approvals for any products, nor verified the market acceptance and demand for such products. As a result, the Company is subject to a number of risks common to emerging companies in the biotech industry. Principal among these risks are the uncertainties of the product discovery and development process, dependence on key individuals, development of the same or similar technological innovations by the Company’s competitors, protection of proprietary technology, compliance with government regulations and approval requirements, the Company’s ability to access capital and uncertainty of market acceptance of products.

The Company has historical net losses and anticipates that it will continue to incur losses for the foreseeable future and had an accumulated deficit of $166.5 million as of June 30, 2021. The Company has funded these losses principally through issuance of common stock, including its follow-on offering and concurrent private placement completed in July 2021, initial public offering (“IPO”), which was completed in August 2020, preferred stock, convertible notes and from cash proceeds received in connection with the Company’s collaboration agreements with Vertex Pharmaceuticals Incorporated (“Vertex”) and Genzyme Corporation (“Sanofi”) (see Note 5). The Company expects to continue to incur operating losses and negative cash flows until such time as it generates a level of revenue that is sufficient to support its cost structure.

As of June 30, 2021, the Company had cash, cash equivalents and marketable securities of $404.4 million. The Company believes these cash, cash equivalents and marketable securities together with the net proceeds from the sale of its common stock in a public offering on July 6, 2021 of $243.1 million will be sufficient to fund its operations and capital expenditure requirements through at least twelve months from the issuance of these condensed consolidated financial statements.

The Company expects to finance the future research and development costs of its product portfolio with its existing cash, cash equivalents and marketable securities, or through strategic financing opportunities that could include, but are not limited to future offerings of its equity, collaboration agreements, or the incurrence of debt. However, there is no guarantee that any of these strategic or financing opportunities will be executed or realized on favorable terms, if at all, and some could be dilutive to existing stockholders. If the Company fails to obtain additional future capital, it may be unable to complete its planned preclinical studies and clinical trials.

Reverse Stock Split

On August 20, 2020, the Board approved a 1-for-1.5949 reverse stock split of the Company’s issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each of the Company’s outstanding series of preferred stock. All share and per share amounts in the accompanying condensed consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital.

Initial Public Offering

On August 20, 2020, the Company’s registration statement on Form S-1 relating to its initial public offering of its common stock was declared effective by the Securities and Exchange Commission (“SEC”). In the IPO, which closed on August 25, 2020, the Company issued and sold 9,987,520 shares of common stock, including full exercise of the underwriters’ over-allotment option to purchase an additional 1,302,720 shares, at a public offering price of $20.00 per share and the aggregate gross proceeds before deducting underwriting discounts and commissions, and other estimated offering expenses payable by the Company, were approximately $199.8 million. Concurrent with the IPO, the Company issued and sold 676,354 shares of common stock at $20.00 per share in a private placement to Vertex and the aggregate proceeds were $13.5 million.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

The accompanying condensed consolidated financial statements reflect the application of certain significant accounting policies as described in this note, and elsewhere in the accompanying condensed consolidated financial statements and notes.

Principles of Consolidation

The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary Kymera Securities Corporation. All intercompany transactions and balances have been eliminated in consolidation.

Basis of Presentation

The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) as found in the Accounting Standards Codification (“ASC”), Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”) and the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K, filed with the SEC on March 11, 2021.

The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements as of and for the year ended December 31, 2020, and, in the opinion of management, reflect all adjustments necessary, all of which were normal and recurring, for the fair statement of the Company’s financial position as of June 30, 2021, the results of operations for the three and six months ended June 30, 2021 and 2020, and cash flows for the six months ended June 30, 2021 and 2020. The results for the six months ended June 30, 2021 are not necessarily indicative of the results for the year ended December 31, 2021 or for any future period.

Significant Accounting Policies

The significant accounting policies used in preparation of these condensed consolidated financial statements for the three and six months ended June 30, 2021 are consistent with those discussed in Note 2 to the consolidated financial statements in the 2020 Annual Report on Form 10-K.

Recent Accounting Pronouncements

Recently Adopted Accounting Standards

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which is intended to simplify the accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard was effective beginning January 1, 2021. The Company adopted this standard as of January 1, 2021 and it did not have a material impact on its financial position or results of operation.

Recently Issued Accounting Standards Not Yet Adopted

In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. As an emerging growth company, the Company expects to delay adoption until January 1, 2023 and is evaluating the impact that the adoption of ASU 2016-13 will have on its condensed consolidated financial statements.

Fair Value Measurements

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

3. Fair Value Measurements

The following table presents 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 June 30, 2021 and December 31, 2020 (in thousands):

	Fair Value Measurements at June 30, 2021:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market fund	$	46,209	$	—	$	—	$	46,209
Marketable securities, current
US treasuries		205,976		—		—		205,976
Corporate bonds		—		68,228		—		68,228
Marketable securities, non-current
US treasuries		22,167		—		—		22,167
Corporate bonds		—		23,138		—		23,138
Restricted cash		1,589		—		—		1,589
Total	$	275,941	$	91,366	$	—	$	367,307

	Fair Value Measurements at December 31, 2020:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market fund	$	19,943	$	—	$	—	$	19,943
Corporate bonds		—		10,499		—		10,499
Marketable securities, current
US treasuries		192,275		—		—		192,275
Corporate bonds		—		72,923		—		72,923
Marketable securities, non-current
US treasuries		132,589		—		—		132,589
Corporate bonds		—		29,942		—		29,942
Restricted cash		1,589		—		—		1,589
Total	$	346,396	$	113,364	$	—	$	459,760

During the six months ended June 30, 2021 and the year ended December 31, 2020, there were no transfers between Level 1, Level 2 and Level 3.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Marketable Securities

6 Months Ended

Jun. 30, 2021

Marketable Securities [Abstract]

Marketable Securities

4. Marketable Securities

The following table summarizes the available-for-sale debt securities held at June 30, 2021 and December 31, 2020 and (in thousands):

Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
June 30, 2021
U.S. treasury securities	$	228,130	$	18	$	(5	)	$	228,143
Corporate securities		91,379		2		(15	)		91,366
Total	$	319,509	$	20	$	(20	)	$	319,509

Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2020
U.S. treasury securities	$	324,917	$	—	$	(53	)	$	324,864
Corporate securities		102,946		—		(81	)		102,865
Total	$	427,863	$	—	$	(134	)	$	427,729

As of June 30, 2021, the Company held 28 securities that had been in an unrealized loss position for less than 12 months with an aggregate fair value of $91.0 million. As of December 31, 2020, the Company held 65 securities that had been in an unrealized loss position for less than 12 months with an aggregate fair value of $392.2 million.

As of June 30, 2021, the Company had 43 securities with a fair value of $274.2 million with a contractual maturity of less than 12 months and 12 securities with a fair value of $45.3 million with a contractual maturity of greater than 12 months. As of December 31, 2020, the Company had 48 securities with a fair value of $295.6 million with a contractual maturity of less than 12 months and 25 securities with a fair value of $162.5 million with a contractual maturity of greater than 12 months. There were no sales of marketable securities during the three and six months ending June 30, 2021 and 2020.

The Company evaluates securities for other-than-temporary impairments based on quantitative and qualitative factors, and considered the decline in market value for the 28 securities in an unrealized loss position as of June 30, 2021 to be primarily attributable to the then current economic and market conditions. The Company neither intends to sell these investments nor concludes that it is more-likely-than-not that the Company will have to sell them before recovery of their carrying values. The Company also believes that it will be able to collect both principal and interest amounts due to it at maturity.

Collaborations

6 Months Ended

Jun. 30, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaborations

5. Collaborations

Sanofi Collaboration Arrangement

Agreement Terms

On July 7, 2020, the Company entered into a collaboration agreement, or the Sanofi Agreement, with Sanofi, to co-develop drug candidates directed to two biological targets. Under the Sanofi Agreement, the Company granted to Sanofi a worldwide exclusive license to develop, manufacture and commercialize certain lead compounds generated during the collaboration directed against IRAK4, or Collaboration Target 1, and one additional undisclosed target in an undisclosed field of use, or Collaboration Target 2. Such license is exercisable on a collaboration target-by-collaboration target basis only after specified milestones. For compounds directed against IRAK4, the field of use includes diagnosis, treatment, cure, mitigation or prevention of any diseases, disorders or conditions, excluding oncology and immune-oncology.

Pursuant to the Sanofi Agreement, the Company is responsible for discovery and preclinical research and conducting a phase 1 clinical trial for at least one degrader directed against IRAK4 plus up to three backup degraders. With respect to both targets, Sanofi is responsible for development, manufacturing, and commercialization of product candidates after a specified development milestone occurs with respect to each collaboration candidate.

In addition, pursuant to the Sanofi Agreement, Sanofi will grant to the Company an exclusive option, or Opt-In Right, exercisable on a collaboration target-by-collaboration target basis that will include the right to (i) to fund 50% of the United States development costs for collaboration products directed against such target in the applicable field of use and (ii) share equally in the net profits and net losses of commercializing collaboration products directed against such target in the applicable field of use in the United States. In addition, if the Company exercises the Opt-In Right, Sanofi will grant to the Company an exclusive option, applicable to each collaboration target, which upon exercise will allow the Company to conduct certain co-promotion activities in the field in the United States.

The Sanofi Agreement, unless earlier terminated, will expire on a product-by-product basis on the date of expiration of all payment obligations under the Sanofi Agreement with respect to such product. The Company or Sanofi may terminate the agreement upon the other party’s material breach or insolvency or for certain patent challenges. In addition, Sanofi may terminate the Sanofi Agreement for convenience or for a material safety event upon advance prior written notice, and the Company may terminate the Sanofi Agreement with respect to any collaboration candidate if, following Sanofi’s assumption of responsibility for the development, commercialization or manufacturing of collaboration candidates with respect to a particular target, Sanofi ceases to exploit any collaboration candidates directed to such target for a specified period.

In consideration for the exclusive licenses granted to Sanofi under the Sanofi Agreement, Sanofi paid to the Company an upfront payment of $150.0 million. The Company will also be reimbursed for certain research activities for a certain backup degrader under the

IRAK4 program, unless certain criteria are not met for an initial IRAK4 degrader. In addition to the upfront payment and the reimbursements, the Company is eligible to receive certain development milestone payments of up to $1.48 billion in the aggregate, of which more than $1.0 billion relates to the IRAK4 program, upon the achievement of certain developmental or regulatory events. The Company will be eligible to receive certain commercial milestone payments up to $700.0 million in the aggregate, of which $400.0 million relate to the IRAK4 program, which are payable upon the achievement of certain net sales thresholds. The Company will be eligible to receive tiered royalties for each program on net sales ranging from the high-single digits to high teens, subject to low-single digits upward adjustments in certain circumstances.

Accounting Treatment

The Company analyzed the discovery and pre-clinical research activities as well as the exclusive license grants under the Sanofi Agreement and concluded that the arrangement was indicative of a vendor-customer relationship and would be accounted for under ASC 606.

The Company identified the following material promises under the arrangement: (1) research services for Collaboration Target 1, (2) research license for Collaboration Target 1, (3) exclusive license for Collaboration Target 1, (4) research services for Collaboration Target 2, (5) research license for Collaboration Target 2, (6) exclusive license for Collaboration Target 2, (7) option to extend the research term, and (8) optional research services during the development period.

The Company determined that Collaboration Targets 1 and 2 are distinct from each other. The research associated with degraders directed to each target is at different stages and the licensed field, should development activities be successful, are different from each other. As such, all promises associated with each target are considered distinct from promises associated with the other target.

The research and development services for each collaboration target were determined not to be distinct from the research license and the exclusive license and have been combined into a single performance obligation for each collaboration target. That is, two performance obligations were identified, the combined research services, research license and exclusive license for Collaboration Target 1 and the combined research services, research license and exclusive license for Collaboration Target 2. The exclusive license for each target is not distinct from the pre-clinical and clinical research and development services under the Sanofi Agreement, primarily due to the highly specialized nature of the research and novel technology involved with developing protein degraders – the pre-clinical activities and studies and first phase 1 clinical trial could not be conducted by another party in the manner required.

The option to extend the research term and optional research services during the development period were evaluated as material rights. The fees associated with each option are at or above the standalone selling price. As such, the underlying options are not performance obligations and fees associated with each option are excluded from the transaction price until the underlying option is exercised.

The Company determined the total transaction price to be $150.0 million, which consists solely of the upfront payment. All milestone payments and option payments are constrained as the achievement of such milestones are contingent upon the success of the underlying research and development activities and are generally outside the control of the Company. The reimbursement of costs for the IRAK4 backup degrader is also treated as constrained variable consideration as the criteria for reimbursement may not always be met, under which circumstances the Company would be responsible for the costs related to the backup degrader. Upon becoming unconstrained, the reimbursement consideration will be added to the transaction price and allocated to Collaboration Target 1.

The Company allocated the upfront payment to each performance obligation based on the relative standalone selling price, as follows:

•

Collaboration Target 1: $120.0 million

•

Collaboration Target 2: $30.0 million

The Company determined the allocation of the $150.0 million transaction price between Collaboration Target 1 and Collaboration Target 2 based on the value of the research and development for the programs from projected research and development costs for each collaboration target plus a developer’s profit and the total potential milestones for each collaboration target.

The Company recognizes revenue associated with each performance obligation 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 each performance obligation. The amounts received that have not yet been recognized as revenue are deferred as a contract liability on the Company’s consolidated balance sheet and will be recognized over the remaining research and development period until the performance obligation is satisfied. Reimbursement consideration added to the transaction price will be recognized as revenue on the same pattern as Collaboration Target 1, with a cumulative catch-up upon becoming unconstrained. The performance obligation has not been fully satisfied as of June 30, 2021. In the three months ended June 30, 2021, the Company recognized $14.4 million in revenue under the Sanofi Agreement, of which $12.0 million was associated with Collaboration Target 1 and $2.4 million was associated with Collaboration Target 2. In the six months ended June 30, 2021, the Company recognized $26.0 million in revenue under the Sanofi Agreement, of which $21.5 million was associated with Collaboration Target 1 and $4.5 million was associated with Collaboration Target 2. The aggregate amount of the transaction price allocated to the Company’s unsatisfied performance obligations and recorded in deferred revenue at June 30, 2021 and December 31, 2020 is $108.4 million and $132.6 million, respectively. During the six months ended June 30, 2021, the Company received $1.7 million in cost reimbursement payments. No milestone or royalty payments have been received under the Sanofi Agreement. As of June 30, 2021, the Company recorded unbilled accounts receivable of $0.9 million related to reimbursable research and development costs under the Sanofi Agreement for activities performed during the second quarter of 2021. As of June 30, 2021, the Company did not have any research and development costs under the Sanofi Agreement for activities performed during the second quarter of 2021 in accounts receivable. The Company will recognize the deferred revenue related to the research and development services based on a cost input method, as described, over the remaining research term, which is a maximum of 2.7 years as of June 30, 2021.

Any consideration related to performance based milestones will be recognized when the risk of probable reversal is resolved, at which point the Company shall adjust the transaction price determined for the agreement accordingly and recognize revenue on a cumulative-catch up basis, reallocating the revised arrangement consideration to the performance obligations. Any consideration related to sales milestone payments and royalties will be recognized when the related milestone events or sales occur and therefore are recognized at the later of when the related sales occur or the relevant performance obligation is satisfied. As part of its evaluation of constraining the milestones, the Company considered numerous factors, including the fact that the achievement of the research and development milestones are contingent upon the results of the underlying research and development activities and are thus outside of the control of the Company.

Sanofi participated in the Company’s Series B Convertible Preferred Stock offering and as a result of this, is considered a related party.

Vertex Agreement

On May 9, 2019 (the “Effective Date”), the Company entered into a collaboration agreement (the “Vertex Agreement”) with Vertex to advance small molecule protein degraders against up to six targets. Under the Vertex Agreement, Vertex has the exclusive option to license the rights to the product candidates developed for the designated targets at which point Vertex will control development and commercialization. Pursuant to the Vertex Agreement, the Company is only responsible for discovery and preclinical research on the targets, and Vertex is responsible for development, manufacturing, and commercialization of the product candidates after it exercises its option to license. The initial research term of the collaboration is four (4) years, extendable for an additional one (1) year period upon mutual agreement by the parties and payment by Vertex of certain per-target fees.

Vertex provided the Company with a non-refundable upfront payment of $50.0 million and purchased 3,059,695 shares of the Company’s Series B-1 Convertible Preferred Stock (the “Series B-1 Preferred Stock”) at $6.54 a share, pursuant to a separate, but simultaneously executed Share Purchase Agreement. The shares were purchased at a premium of $5.9 million, which was included in the transaction price and will be recognized as revenue over the period of performance. As a result of this purchase, Vertex is considered a related party.

The Company is eligible to receive up to $170.0 million in payments per target, including development, regulatory and commercial milestones as well as option exercise payments. In addition, Vertex is obligated to pay the Company tiered royalties on future net sales on any products that may result from the Vertex Agreement. None of the payments under the Vertex Agreement are refundable. The Company may also perform follow-on research for an optioned target upon Vertex’s request and at Vertex’s expense.

The term of the Vertex Agreement began on the Effective Date and expires upon the expiration of all payment obligations from Vertex to Company under the Vertex Agreement or, if Vertex does not exercise any of its options, the lapse of all Vertex’s option rights under the Vertex Agreement. Vertex also has the ability to terminate for convenience with prior written notice to the Company, and either party may terminate for an uncured material breach.

Accounting Treatment

The Company analyzed the joint research activities required under the Vertex Agreement and concluded that the arrangement was indicative of a vendor-customer relationship and would be accounted for under ASC 606.

The Company identified the following material promises under the arrangement: (1) the non-exclusive, royalty-free research license; (2) the research and development services to be performed on up to six targets; and (3) the option to license each of the targets for development, manufacturing, and commercialization efforts. The research and development services were determined not to be distinct from the research and development license and have been combined into a single performance obligation. The Company determined that the option to license the targets in the future was not priced at a discount, and that the option exercise fee for each target is at or above the standalone selling price for research at this stage of development; as such, the options and the underlying licenses are excluded from the performance obligation and the option exercise fees are excluded from the transaction price until the underlying option is exercised.

As part of its evaluation of constraining the research and development milestones, the Company considered numerous factors, including the fact that the achievement of the research and development milestones is contingent upon the results of the underlying research and development activities and is thus outside of the control of the Company.

At the commencement of the arrangement, two units of accounting were identified: the issuance of 3,059,695 shares of the Series B-1 Preferred Stock and the research activities the Company will perform over the Research Term. The Company determined the total transaction price to be $55.9 million, which consists of $5.9 million attributed to the premium from the shares of Series B-1 Preferred Stock sold to Vertex and the $50.0 million upfront payment. To determine the fair value of the Series B-1 Preferred Stock issued to Vertex, the Company performed a valuation of the shares of the Company’s common and preferred stock, which took into consideration recent financings, and the Company’s recent development and future exit strategies, as well as a discount for lack of marketability.

The Company recognizes revenue associated with the performance obligation as the research and development services are provided using an input method, according to the costs incurred as related to the research and development activities on each program and the costs expected to be incurred in the future to satisfy the 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. The amounts received that have not yet been recognized as revenue are deferred as a contract liability on the Company’s consolidated balance sheet and will be recognized over the remaining research and development period until the performance obligation is satisfied. The performance obligation has not been fully satisfied as June 30, 2021. During the three months ended June 30, 2021 and 2020, the Company recognized $4.1 million and $3.3 million, respectively, under the Vertex Agreement. During the six months ended June 30, 2021 and 2020, the Company recognized $11.2 million and $6.7 million respectively, in revenue under the Vertex Agreement. All $11.2 million revenue recognized in the six months ended June 30, 2021 was recognized from amounts that were recorded in deferred revenue as of December 31, 2020. The aggregate amount of the transaction price allocated to the Company’s unsatisfied performance obligation and recorded in deferred revenue at June 30, 2021 and December 31, 2020 is $26.5 million and $37.7 million, respectively. The Company will recognize the deferred revenue related to the research and development services based on a cost input method, over the remaining research term, which is a maximum of 1.3 years as June 30, 2021.

Any consideration related to sales milestone payments (including royalties) will be recognized when the related milestone events or sales occur and therefore is recognized at the later of when the related sales occur or the relevant performance obligation is satisfied.

Compound Collaboration

In October 2017, the Company entered into a collaboration agreement (the “Collaboration”) with a pharmaceutical company to jointly identify, research and conduct preclinical development of collaboration compounds against specified collaboration targets to identify drug candidates. Under the terms of the Collaboration, both parties provided one another with a non-exclusive, royalty-free, sub-licensable research and development license to each party’s intellectual property to develop five agreed-upon collaboration targets, as well as an exclusive, royalty-bearing development and commercialization license to sell any licensed products that stem from such research. The parties also have the ability to nominate additional collaboration targets if agreed-upon, as long as there are no more than five targets at any given time.

In exchange for the non-exclusive license rights, the Company provided the pharmaceutical company with an equity grant and is required to make tiered royalty payments based on net sales of all products licensed under the agreement in the low single-digit percentages. In conjunction with the Collaboration, the Company initially issued 886,305 Series A Preferred Units (“Series A Preferred Units”) to the pharmaceutical company. On November 1, 2018, these Series A Preferred Units were exchanged on a one-for-one basis for shares of Series A Convertible Preferred Stock (the “Series A Preferred Stock”). These shares vested in equal installments over three years and the Company recorded expense over the vesting period based on the fair value of the shares under the Collaboration. The Company recorded $0.2 million to research and development expense related to the vesting of 110,788 shares of Series A Preferred Stock for the six months ended June 30, 2020. As of December 31, 2020, all shares under the Collaboration were fully vested and all expenses had been recognized.

The royalty payments are contingent and as such are not being recorded until incurred. The Company determined that the license is representative of an in-process research and development asset, with no future alternative use. As such, the Company recorded the expense related to the vesting of shares of Series A Preferred Stock as research and development expense in the Company’s condensed consolidated statements of operations and comprehensive loss.

The Collaboration can be terminated by either party for convenience with 60-days written notice and may also be terminated in the event of a material breach.

The following table presents the changes in accounts receivable, contract assets and liabilities for the six months ended June 30, 2021 (in thousands):

	Balance at December 31, 2020		Additions		Deductions			Balance at June 30, 2021
Accounts receivable and contract assets:
Billed receivables - Sanofi	$	577	$	1,718	$	(2,295	)	$	—
Unbilled receivables - Sanofi		856		1,766		(1,718	)		904
Total accounts receivable and contract assets	$	1,433	$	3,484	$	(4,013	)	$	904
Contract liabilities:
Deferred revenue - Vertex	$	37,748	$	—	$	(11,226	)	$	26,522
Deferred revenue - Sanofi		132,642		1,766		(25,995	)		108,413
Total contract liabilities	$	170,390	$	1,766	$	(37,221	)	$	134,935

Property and Equipment

6 Months Ended

Jun. 30, 2021

Property Plant And Equipment [Abstract]

Property and Equipment

6. Property and Equipment

Property and equipment consists of the following as of June 30, 2021 and December 31, 2020 (in thousands):

	June 30, 2021			December 31, 2020
Lab and office equipment under finance right-of-use asset	$	4,003		$	2,771
Lab equipment		2,373			1,636
Computer equipment		266			89
Furniture & fixtures		921			861
Leasehold improvements		7,731			7,599
Assets not yet in service		—			32
Total property and equipment		15,294			12,988
Less accumulated depreciation		(3,176	)		(2,147	)
Property and equipment, net	$	12,118		$	10,841

Depreciation expense for the three months ended June 30, 2021 and 2020 was $0.6 million and $0.4 million, respectively. Depreciation expense for the six months ended June 30, 2021 and 2020 was $1.0 million and $0.8 million, respectively

Included in property and equipment is lab and office equipment right-of-use assets under finance leases with a cost basis of $4.0 million and $2.8 million as of June 30, 2021 and December 31, 2020, respectively and accumulated amortization expense of $1.5 million and $1.2 million, respectively.

Amortization expense related to right-of-use assets during both the three months ended June 30, 2021 and 2020 was $0.2 million. Amortization expense related to right-of-use assets during both the six months ended June 30, 2021 and 2020 was $0.4 million.

Leases

6 Months Ended

Jun. 30, 2021

Leases [Abstract]

Leases

7. Leases

In February 2018, the Company entered into a noncancelable facility lease agreement (the “Lease”) for 9,836 square feet of research and development and office space in Cambridge, Massachusetts. In March 2020, the Company signed a termination agreement for this lease which was determined to be a lease modification that resulted in a reduction of the right-of-use asset and liability of $2.2 million. The lease termination was effective July 31, 2020 at which point the Company no longer had any obligations under the Lease.

In accordance with the Lease, the Company was required to maintain a security deposit and provided a letter of credit to the landlord for $0.2 million, which was subsequently collected in October 2020 following the Company’s release from the security deposit and letter of credit.

In April 2019, the Company entered into a facility sublease agreement (the “Sublease”) for 1,471 square feet of office space in Cambridge, Massachusetts. The term of the Sublease began on June 24, 2019 and terminated on June 30, 2020, and following termination, the Company had no further obligations under the Sublease. The Sublease required the Company to share in prorated operating expenses and property taxes based upon actual amounts incurred; those amounts were considered variable lease costs and, therefore, are not included in the measurement of the lease and are instead recognized to expense as incurred.

In October 2019, the Company entered into a noncancelable facility lease agreement (the “New Lease”) for 34,522 square feet of research and development and office space in Watertown, Massachusetts. The term of the New Lease is 120 months and expires on March 31, 2030. The New Lease has an option to be extended for an additional five years. The New Lease is not reasonably certain to be extended and as such the additional term is not included in the measurement of the lease. The New Lease includes a rent escalation clause, and rent expense is being recorded on a straight-line basis. The Company was eligible for and received a tenant incentive allowance of $5.5 million in 2020 as the tenant improvements were completed. The full allowance amount had been collected from the landlord as of December 31, 2020. In accordance with the New Lease, the Company is required to maintain a security deposit and provided a letter of credit to the landlord for $1.6 million, which is classified as restricted cash on the condensed consolidated balance sheets as of June 30, 2021.

The Company’s finance lease obligations consist of certain property and equipment financed through capital leases.

The components of the lease costs for the three and six months ended June 30, 2021 and 2020, were as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Operating lease costs	$	524	$	673	$	1,047	$	1,562
Finance lease costs:
Amortization of right-to-use assets, finance leases		193		195		371		356
Interest expense for finance lease liabilities		21		31		37		65
Variable lease costs		153		94		385		201
Total lease costs	$	891	$	993	$	1,840	$	2,184

Supplemental cash flow information relating to the Company’s leases for the six months ended June 30, 2021 and 2020 was as follows (in thousands):

	Six Months Ended June 30,
	2021		2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in (provided by) operating leases	$	1,428	$	(3,905	)
Operating cash flows used in finance leases	$	350	$	309
Financing cash flows used in finance leases	$	37	$	65

Weighted average remaining lease terms and discount rates as of June 30, 2021 and 2020 were as follows:

	Six Months Ended June 30,
	2021			2020
Remaining lease term:
Operating lease	8.84 years			9.80 years
Finance lease	2.68 years			3.30 years
Discount Rate:
Operating lease		10.50	%		10.50	%
Finance lease		8.51	%		7.9	%

The undiscounted future lease payments for operating and finance leases as of June 30, 2021, were as follows (in thousands):

Fiscal Year	Operating Leases			Finance Leases
2021 (excluding the first and second quarter)	$	1,262		$	588
2022		2,581			924
2023		2,659			710
2024		2,732			194
2025		2,814			—
Thereafter		12,925			—
Total minimum lease payments		24,973			2,416
Less amounts representing interest or imputed interest		(8,852	)		(233	)
Present value of lease liabilities	$	16,121		$	2,183

Accrued Expenses

6 Months Ended

Jun. 30, 2021

Accrued Liabilities Current [Abstract]

Accrued Expenses

8. Accrued Expenses

Accrued expenses consist of the following as of June 30, 2021 and December 31, 2020 (in thousands):

	June 30, 2021		December 31, 2020
Research and development expenses	$	10,504	$	5,821
Payroll and payroll-related		2,319		2,918
Professional fees		1,590		1,585
Other		255		6
Accrued expenses	$	14,668	$	10,330

Other Commitments and Contingencies

6 Months Ended

Jun. 30, 2021

Commitments And Contingencies Disclosure [Abstract]

Other Commitments and Contingencies

9. Other Commitments and Contingencies

Legal Proceedings

In the ordinary course of business, the Company may be subject to legal proceedings, claims and litigation as the Company operates in an industry susceptible to patent legal claims. The Company accounts for estimated losses with respect to legal proceedings and claims when such losses are probable and estimable. Legal costs associated with these matters are expensed when incurred. The Company is not currently a party to any legal proceedings.

Indemnification Arrangements

As permitted under Delaware law, the Company has agreements whereby it indemnifies its investors, employees, officers, and directors (collectively, the “Indemnified Parties”) for certain events or occurrences while the Indemnified Parties are, or were serving, at its request in such capacity. The term of the indemnification period is for the Indemnified Parties’ lifetime. The Company believes the estimated fair value of these indemnification agreements is minimal. The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to these agreements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally the Company’s business partners or customers, in connection with any U.S. patent or any copyright or other intellectual property infringement claim by any third party with respect to the Company’s products. The maximum potential amount of future payments the Company could be required to make under these

indemnification agreements is unlimited. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations as of June 30, 2021 or December 31, 2020.

Convertible Preferred Stock

6 Months Ended

Jun. 30, 2021

Temporary Equity Disclosure [Abstract]

Convertible Preferred Stock

10. Convertible Preferred Stock

In January 2020, the Company issued 1,182,265 shares of Series B Preferred Stock at $4.06 per share to complete the second closing of the Series B Preferred Stock issuance for total proceeds of $4.8 million. The issuance costs related to the second tranche were insignificant.

In March 2020, the Company executed a Series C Preferred Stock Purchase Agreement (the “Series C SPA”) to issue 13,539,141 shares of Series C Convertible Preferred Stock (the “Series C Preferred Stock”) at a purchase price of $6.5366 per share for a total consideration of $88.2 million, net of issuance costs of $0.3 million. In conjunction with the Series C SPA, the Company exchanged 1,988,802 shares of Series A Convertible Preferred Stock (the “Series A Preferred Stock”) for an equal number of shares of Series C Preferred Stock related to a transaction amongst investors. This resulted in a total issuance of 15,527,943 shares of Series C Preferred Stock. The fair value of the shares of Series C Preferred Stock issued exceeded the carrying value of the shares of Series A Preferred Stock exchanged by $9.1 million, which was recognized as a deemed dividend through a reduction of $2.3 million to additional paid-in capital and an increase of $6.7 million to the accumulated deficit. The $9.1 million deemed dividend increased the net loss for the six months ended June 30, 2020 to arrive at net loss attributable to common stockholders in the calculation of earnings per share.

Immediately prior to the IPO, the Company’s Articles of Association (the “Articles”), as further amended and restated (the “2018 Amended Articles”), authorized a total of 52,483,788 shares of convertible preferred stock with a par value of $0.0001 per share, of which 3,000,000 shares have been designated as Series Seed Convertible Preferred Stock, 14,886,305 shares have been designated as Series A Preferred Stock, 16,009,845 shares have been designated as Series B Preferred Stock (the “Series B Preferred Stock”), 3,059,695 shares have been designated as Series B-1 Preferred Stock and 15,527,943 shares have been designated as Series C Preferred Stock. The Series A, Series B, Series B-1 and Series C Preferred Stock are collectively referred to as the Convertible Preferred Stock.

In connection with the Company’s August 21, 2020 IPO all issued and outstanding 50,439,595 shares of Convertible Preferred Stock were converted into 31,625,534 shares of the Company’s common stock and are no longer issued or outstanding following the completion of the offering.

Equity-Based Compensation

6 Months Ended

Jun. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity-Based Compensation

11. Equity-Based Compensation

2018 Stock Option and Grant Plan

In November 2018, the Company adopted, and its stockholders approved, the 2018 Stock Option and Grant Plan (the “2018 Plan”), which provides for the granting of stock options and other equity-based awards at the discretion of the Board of Directors or any subcommittee of the Board of Directors to the Company’s employees, officers, directors, and independent contractors. No further grants will be made under the 2018 Plan. However, the 2018 Plan will continue to govern outstanding equity awards granted thereunder. To the extent outstanding options granted under the 2018 Plan are cancelled, forfeited or otherwise terminated without being exercised and would otherwise have been returned to the share reserve under the 2018 Plan, the number of shares underlying such awards will be available for future grant under the 2020 Stock Option and Incentive Plan.

2020 Stock Option and Incentive Plan

In August 2020, the Company and its stockholders approved the 2020 Stock Option and Incentive Plan (the “2020 Plan”), which became effective on August 20, 2020. The 2020 Plan replaced the 2018 Plan as the Company’s Board of Directors has determined not to make additional awards under the 2018 Plan following the closing of the Company’s IPO. The 2020 Plan allows the Company to make equity-based and cash-based incentive awards to its officers, employees, directors and consultants. The Company has initially reserved 4,457,370 shares of its common stock for the issuance of awards under the 2020 Plan, which includes the shares of common stock remaining available for issuance under its 2018 Plan as of the business day immediately prior to the effective date of the registration statement. The 2020 Plan provides that the number of shares reserved and available for issuance will automatically increase on January 1, 2021 and each January 1 thereafter, by 4% of the Company’s outstanding number of shares of common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. These limits are subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. As of June 30, 2021, there were an aggregate of 3,150,858 shares remaining available for future grants.

2020 Employee Stock Purchase Plan

In August 2020, the Company and its stockholders approved the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), which became effective August 20, 2020. The 2020 ESPP initially reserves and authorizes the issuance of up to a total of 445,653 shares of common stock to participating employees. The 2020 ESPP provides that the number of shares reserved and available for issuance will automatically increase on January 1, 2021 and each January 1 thereafter through January 1, 2030, by the least of (i) 438,898 shares of common stock, (ii) 1% of the Company’s outstanding number of shares of common stock on the immediately preceding December 31 or (iii) such lesser number of shares of common stock as determined by the administrator of the 2020 ESPP. The number of shares reserved under the 2020 ESPP is subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization.

Stock Options

A summary of stock option activity under the 2020 Plan during the six months ended June 30, 2021 is as follows (in thousands except share and per share data):

	Number of Options Outstanding			Weighted Average Strike Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2020		5,832,712		$	8.17		9.08	$	314,001
Granted		1,871,037			49.07
Exercised		(801,233	)		3.27
Forfeited		(89,527	)		13.85
Outstanding at June 30. 2021		6,812,989		$	19.90		8.93	$	197,003
Exercisable at June 30, 2021		1,596,721		$	7.48		8.49	$	65,526

The intrinsic value of stock options exercised during the three months ended June 30, 2021 and 2020 was $17.1 million and $0.0 million, respectively. The intrinsic value of stock options exercised during the six months ended June 30, 2021 and 2020 was $37.1 million and $0.1 million, respectively.

The weighted-average fair value of options granted during the three months ended June 30, 2021 and 2020 was $26.99 and $3.32, respectively. The weighted-average fair value of options granted during the six months ended June 30, 2021 and 2020 was $28.66 and $3.62, respectively.

As of June 30, 2021, the total unrecognized stock-based compensation expense for unvested stock options was $69.7 million, which is expected to be recognized over 2.8 years.

The following table outlines our equity-based compensation expense for stock options for the three and six months ended June 30, 2021 and 2020:

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development	$	2,821	$	371	$	4,458	$	553
General and administrative		2,792		235		4,226		363
Total equity-based compensation	$	5,613	$	606	$	8,684	$	916

The weighted-average assumptions that the Company used in the Black-Scholes option pricing model to determine the grant date fair value of stock options granted to employees and non-employees for the three and six months ended June 30, 2021 and 2020 were as follows:

	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2020			2021			2020
Expected term (in years)		5.87			6.27			5.83			6.22
Volatility		65	%		70	%		66	%		78	%
Risk-free interest rate		1.05	%		0.41	%		0.90	%		0.65	%
Dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

Restricted Common Stock

The Company has granted shares of restricted common stock with service-based and performance-based vesting conditions. A summary of restricted stock activity under the 2018 Plan during the six months ended June 30, 2021 is as follows:

	Number of Units Outstanding			Grant Date Fair Value per Share
Unvested at December 31, 2020		110,104		$	1.60
Vested		(36,582	)		1.60
Unvested at June 30, 2021		73,522		$	1.60

No restricted stock awards were granted during the three or six months ended June 30, 2021 and 2020. As of June 30, 2021, the total unrecognized stock-based compensation expense for unvested restricted stock was $0.2 million, which is expected to be recognized over one year.

During the three months ended June 30, 2021 and 2020, the Company recognized an immaterial amount of equity-based compensation expense for restricted stock. During both the six months ended June 30, 2021 and 2020, the Company recognized approximately $0.1 million for restricted stock of which approximately $0.1 million and an immaterial amount were included in research and development and general and administrative expense, respectively.

Equity-Based Compensation Expense

Total equity-based compensation expense recorded as research and development and general and administrative expenses for employees, directors, and non-employees during the three and six months ended June 30, 2021 and 2020 is as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development	$	2,917	$	423	$	4,642	$	662
General and administrative		2,809		241		4,256		373
Total equity-based compensation	$	5,726	$	664	$	8,898	$	1,035

Related Party Transactions

6 Months Ended

Jun. 30, 2021

Related Party Transactions

12. Related-Party Transactions

In addition to the collaborations discussed in Note 5, the Company had the following related party transactions for the period presented in the accompanying condensed consolidated financial statements, which have not otherwise been discussed in these notes to the condensed consolidated financial statements. The Company made payments of $0.4 million to an investor for rent expenses during the six months ended June 30, 2020. No such payments were made during the three or six months ended June 30, 2021.

Income Taxes

6 Months Ended

Jun. 30, 2021

Income Tax Disclosure [Abstract]

Income Taxes

13. Income Taxes

Income taxes for the three and six months ended June 30, 2021 and 2020 have been calculated based on an estimated annual effective tax rate and certain discrete items. For the three and six months ended June 30, 2021 and 2020, no income tax was recorded.

On March 27, 2020, the CARES Act was enacted in response to the COVID-19 pandemic. Among other things, the CARES Act permits corporate taxpayers to carryback net operating losses (“NOLs”) originating in 2018 through 2020 to each of the five preceding tax years. Further, the CARES Act removed the 80% taxable income limitation on utilization of those NOLs allowing corporate taxpayers to fully utilize NOL carryforwards to offset taxable income in 2018, 2019 or 2020. Such changes may result in the generation of refunds of previously paid income taxes which are expected to be received over the next eighteen months.

The Company has never been examined by the Internal Revenue Service or any other jurisdiction for any tax years and, as such, all years within the applicable statutes of limitations are potentially subject to audit.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Net Loss per Share

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Net Loss per Share

14. Net Loss per Share

Net Loss per Share

Basic and diluted loss per share is computed by dividing net loss attributable to common stockholders by the weighted-average common shares outstanding (in thousands, except for share and per share data):

	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2020			2021			2020
Numerator:
Net loss	$	(24,660	)	$	(13,989	)	$	(37,735	)	$	(24,921	)
Deemed dividend from exchange of convertible preferred stock		—			—			—			(9,050	)
Net loss attributable to common stockholders	$	(24,660	)	$	(13,989	)	$	(37,735	)	$	(33,971	)
Denominator:
Weighted average common shares outstanding, basic and diluted		45,094,238			2,002,825			44,873,083			1,977,720
Net loss per share, basic and diluted	$	(0.55	)	$	(6.98	)	$	(0.84	)	$	(17.18	)

The Company’s potentially dilutive securities, which include convertible preferred stock, restricted stock, and stock options, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following from the computation of diluted net loss per share attributable to common stockholders at June 30, 2021 and 2020 because including them would have had an anti-dilutive effect:

	Six Months Ended June 30,
	2021		2020
Convertible preferred stock		—		31,625,534
Unvested restricted stock		73,522		157,692
Options to purchase common stock		6,812,989		4,343,062
Total		6,886,511		36,126,288

Subsequent Events

6 Months Ended

Jun. 30, 2021

Subsequent Events [Abstract]

Subsequent Events

15. Subsequent Events

In July 2021, the Company completed a follow-on offering and issued and sold 5,468,250 shares of common stock, including full exercise of the underwriters’ over-allotment option to purchase an additional 713,250 shares, at a public offering price of $47.00 per share. The aggregate gross proceeds before deducting underwriting discounts and commissions, and other estimated offering expenses payable by the Company were approximately $257.0 million. Concurrent with the follow-on offering, the Company issued and sold 49,928 shares of common stock at $47.00 per share in a private placement to Vertex and the aggregate proceeds were $2.3 million.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2021
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary Kymera Securities Corporation. All intercompany transactions and balances have been eliminated in consolidation.
Basis of Presentation	Basis of Presentation The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) as found in the Accounting Standards Codification (“ASC”), Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”) and the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2020 included in the Company’s Annual Report on Form 10-K, filed with the SEC on March 11, 2021. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements as of and for the year ended December 31, 2020, and, in the opinion of management, reflect all adjustments necessary, all of which were normal and recurring, for the fair statement of the Company’s financial position as of June 30, 2021, the results of operations for the three and six months ended June 30, 2021 and 2020, and cash flows for the six months ended June 30, 2021 and 2020. The results for the six months ended June 30, 2021 are not necessarily indicative of the results for the year ended December 31, 2021 or for any future period.
Significant Accounting Policies	Significant Accounting Policies The significant accounting policies used in preparation of these condensed consolidated financial statements for the three and six months ended June 30, 2021 are consistent with those discussed in Note 2 to the consolidated financial statements in the 2020 Annual Report on Form 10-K.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Standards In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which is intended to simplify the accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard was effective beginning January 1, 2021. The Company adopted this standard as of January 1, 2021 and it did not have a material impact on its financial position or results of operation. Recently Issued Accounting Standards Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. As an emerging growth company, the Company expects to delay adoption until January 1, 2023 and is evaluating the impact that the adoption of ASU 2016-13 will have on its condensed consolidated financial statements.

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on Recurring Basis

	Fair Value Measurements at June 30, 2021:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market fund	$	46,209	$	—	$	—	$	46,209
Marketable securities, current
US treasuries		205,976		—		—		205,976
Corporate bonds		—		68,228		—		68,228
Marketable securities, non-current
US treasuries		22,167		—		—		22,167
Corporate bonds		—		23,138		—		23,138
Restricted cash		1,589		—		—		1,589
Total	$	275,941	$	91,366	$	—	$	367,307

	Fair Value Measurements at December 31, 2020:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market fund	$	19,943	$	—	$	—	$	19,943
Corporate bonds		—		10,499		—		10,499
Marketable securities, current
US treasuries		192,275		—		—		192,275
Corporate bonds		—		72,923		—		72,923
Marketable securities, non-current
US treasuries		132,589		—		—		132,589
Corporate bonds		—		29,942		—		29,942
Restricted cash		1,589		—		—		1,589
Total	$	346,396	$	113,364	$	—	$	459,760

Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2021

Marketable Securities [Abstract]

Summary of Available-for-Sale Debt Securities

The following table summarizes the available-for-sale debt securities held at June 30, 2021 and December 31, 2020 and (in thousands):

Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
June 30, 2021
U.S. treasury securities	$	228,130	$	18	$	(5	)	$	228,143
Corporate securities		91,379		2		(15	)		91,366
Total	$	319,509	$	20	$	(20	)	$	319,509

Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2020
U.S. treasury securities	$	324,917	$	—	$	(53	)	$	324,864
Corporate securities		102,946		—		(81	)		102,865
Total	$	427,863	$	—	$	(134	)	$	427,729

Collaborations (Tables)

6 Months Ended

Jun. 30, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Change in Accounts Receivable, Contract Asset and Liabilities

The following table presents the changes in accounts receivable, contract assets and liabilities for the six months ended June 30, 2021 (in thousands):

	Balance at December 31, 2020		Additions		Deductions			Balance at June 30, 2021
Accounts receivable and contract assets:
Billed receivables - Sanofi	$	577	$	1,718	$	(2,295	)	$	—
Unbilled receivables - Sanofi		856		1,766		(1,718	)		904
Total accounts receivable and contract assets	$	1,433	$	3,484	$	(4,013	)	$	904
Contract liabilities:
Deferred revenue - Vertex	$	37,748	$	—	$	(11,226	)	$	26,522
Deferred revenue - Sanofi		132,642		1,766		(25,995	)		108,413
Total contract liabilities	$	170,390	$	1,766	$	(37,221	)	$	134,935

Property and Equipment (Tables)

6 Months Ended

Jun. 30, 2021

Property Plant And Equipment [Abstract]

Summary of Property and Equipment

Property and equipment consists of the following as of June 30, 2021 and December 31, 2020 (in thousands):

	June 30, 2021			December 31, 2020
Lab and office equipment under finance right-of-use asset	$	4,003		$	2,771
Lab equipment		2,373			1,636
Computer equipment		266			89
Furniture & fixtures		921			861
Leasehold improvements		7,731			7,599
Assets not yet in service		—			32
Total property and equipment		15,294			12,988
Less accumulated depreciation		(3,176	)		(2,147	)
Property and equipment, net	$	12,118		$	10,841

Leases (Tables)

6 Months Ended

Jun. 30, 2021

Leases [Abstract]

Components of Lease Costs

The components of the lease costs for the three and six months ended June 30, 2021 and 2020, were as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Operating lease costs	$	524	$	673	$	1,047	$	1,562
Finance lease costs:
Amortization of right-to-use assets, finance leases		193		195		371		356
Interest expense for finance lease liabilities		21		31		37		65
Variable lease costs		153		94		385		201
Total lease costs	$	891	$	993	$	1,840	$	2,184

Supplemental Cash Flow Information Relating to Leases

Supplemental cash flow information relating to the Company’s leases for the six months ended June 30, 2021 and 2020 was as follows (in thousands):

	Six Months Ended June 30,
	2021		2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in (provided by) operating leases	$	1,428	$	(3,905	)
Operating cash flows used in finance leases	$	350	$	309
Financing cash flows used in finance leases	$	37	$	65

Summary of Weighted Average Remaining Lease Terms and Discount Rates

Weighted average remaining lease terms and discount rates as of June 30, 2021 and 2020 were as follows:

	Six Months Ended June 30,
	2021			2020
Remaining lease term:
Operating lease	8.84 years			9.80 years
Finance lease	2.68 years			3.30 years
Discount Rate:
Operating lease		10.50	%		10.50	%
Finance lease		8.51	%		7.9	%

Summary of Undiscounted Future Lease Payments for Operating and Finance Leases

The undiscounted future lease payments for operating and finance leases as of June 30, 2021, were as follows (in thousands):

Fiscal Year	Operating Leases			Finance Leases
2021 (excluding the first and second quarter)	$	1,262		$	588
2022		2,581			924
2023		2,659			710
2024		2,732			194
2025		2,814			—
Thereafter		12,925			—
Total minimum lease payments		24,973			2,416
Less amounts representing interest or imputed interest		(8,852	)		(233	)
Present value of lease liabilities	$	16,121		$	2,183

Accrued Expenses (Tables)

6 Months Ended

Jun. 30, 2021

Accrued Liabilities Current [Abstract]

Schedule of Accrued Liabilities

Accrued expenses consist of the following as of June 30, 2021 and December 31, 2020 (in thousands):

	June 30, 2021		December 31, 2020
Research and development expenses	$	10,504	$	5,821
Payroll and payroll-related		2,319		2,918
Professional fees		1,590		1,585
Other		255		6
Accrued expenses	$	14,668	$	10,330

Equity-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Summary of Stock Option Activity

A summary of stock option activity under the 2020 Plan during the six months ended June 30, 2021 is as follows (in thousands except share and per share data):

	Number of Options Outstanding			Weighted Average Strike Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2020		5,832,712		$	8.17		9.08	$	314,001
Granted		1,871,037			49.07
Exercised		(801,233	)		3.27
Forfeited		(89,527	)		13.85
Outstanding at June 30. 2021		6,812,989		$	19.90		8.93	$	197,003
Exercisable at June 30, 2021		1,596,721		$	7.48		8.49	$	65,526

Summary of Equity-Based Compensation Expense

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development	$	2,917	$	423	$	4,642	$	662
General and administrative		2,809		241		4,256		373
Total equity-based compensation	$	5,726	$	664	$	8,898	$	1,035

Summary of Weighted-Average Assumptions

	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2020			2021			2020
Expected term (in years)		5.87			6.27			5.83			6.22
Volatility		65	%		70	%		66	%		78	%
Risk-free interest rate		1.05	%		0.41	%		0.90	%		0.65	%
Dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

Summary of Restricted Stock Activity

	Number of Units Outstanding			Grant Date Fair Value per Share
Unvested at December 31, 2020		110,104		$	1.60
Vested		(36,582	)		1.60
Unvested at June 30, 2021		73,522		$	1.60

Stock Options

Summary of Equity-Based Compensation Expense

The following table outlines our equity-based compensation expense for stock options for the three and six months ended June 30, 2021 and 2020:

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development	$	2,821	$	371	$	4,458	$	553
General and administrative		2,792		235		4,226		363
Total equity-based compensation	$	5,613	$	606	$	8,684	$	916

Net Loss per Share (Tables)

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Summary of Basic and Diluted Loss Per Share

	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2020			2021			2020
Numerator:
Net loss	$	(24,660	)	$	(13,989	)	$	(37,735	)	$	(24,921	)
Deemed dividend from exchange of convertible preferred stock		—			—			—			(9,050	)
Net loss attributable to common stockholders	$	(24,660	)	$	(13,989	)	$	(37,735	)	$	(33,971	)
Denominator:
Weighted average common shares outstanding, basic and diluted		45,094,238			2,002,825			44,873,083			1,977,720
Net loss per share, basic and diluted	$	(0.55	)	$	(6.98	)	$	(0.84	)	$	(17.18	)

Schedule of Diluted Net Loss Per Share Attributable to Common Stockholders Anti-Diluted Effect

The Company excluded the following from the computation of diluted net loss per share attributable to common stockholders at June 30, 2021 and 2020 because including them would have had an anti-dilutive effect:

	Six Months Ended June 30,
	2021		2020
Convertible preferred stock		—		31,625,534
Unvested restricted stock		73,522		157,692
Options to purchase common stock		6,812,989		4,343,062
Total		6,886,511		36,126,288

Organization and Nature of Business - Additional Information (Details) $ / shares in Units, $ in Thousands				1 Months Ended	6 Months Ended
	Jul. 06, 2021 USD ($)	Aug. 25, 2020 USD ($) $ / shares shares	Aug. 20, 2020	Jul. 31, 2021 USD ($) $ / shares shares	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Organization and Nature of Business [Line Items]
Accumulated deficit					$ 166,500	$ 128,765
Cash, cash equivalents and marketable securities					$ 404,400
Reverse stock split, description					On August 20, 2020, the Board approved a 1-for-1.5949 reverse stock split of the Company’s issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each of the Company’s outstanding series of preferred stock. All share and per share amounts in the accompanying condensed consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital.
Reverse stock split			1.5949
Initial Public Offering
Organization and Nature of Business [Line Items]
Common stock shares issued \| shares		9,987,520
Common stock per share \| $ / shares		$ 20.00
Gross proceeds from issuance initial public offering		$ 199,800
Underwriters
Organization and Nature of Business [Line Items]
Common stock shares issued \| shares		1,302,720
Private Placement \| Vertex Pharmaceuticals Incorporated
Organization and Nature of Business [Line Items]
Common stock shares issued \| shares		676,354
Common stock per share \| $ / shares		$ 20.00
Aggregate proceeds from issuance of private placement		$ 13,500
Subsequent Events
Organization and Nature of Business [Line Items]
Net proceeds from sale of common stock in public offering	$ 243,100
Subsequent Events \| Underwriters
Organization and Nature of Business [Line Items]
Common stock shares issued \| shares				713,250
Subsequent Events \| Private Placement \| Vertex Pharmaceuticals Incorporated
Organization and Nature of Business [Line Items]
Common stock shares issued \| shares				49,928
Common stock per share \| $ / shares				$ 47.00
Aggregate proceeds from issuance of private placement				$ 2,300

Summary of Significant Accounting Policies - Additional Information (Details) - ASU 2019-12	Jun. 30, 2021
Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Accounting standards update, adoption date	Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect	true

- Definition

Indicates (true false) whether accounting standards update was adopted.

+ References

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+ Details

- Definition

Date accounting standards update was adopted, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Subparagraph (a)
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-URI http://asc.fasb.org/extlink&oid=121483254&loc=SL120254523-199619

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-Paragraph 8
-Subparagraph (a)

+ Details

Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Marketable securities	$ 319,509	$ 427,729
Fair Value, Recurring
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Restricted cash	1,589	1,589
Total	367,307	459,760
Fair Value, Recurring \| Money Market Fund
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents	46,209	19,943
Fair Value, Recurring \| Corporate Bonds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents		10,499
Short-term investments	68,228	72,923
Long-term investments	23,138	29,942
Fair Value, Recurring \| US Treasuries
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Short-term investments	205,976	192,275
Long-term investments	22,167	132,589
Fair Value, Recurring \| Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Restricted cash	1,589	1,589
Total	275,941	346,396
Fair Value, Recurring \| Level 1 \| Money Market Fund
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents	46,209	19,943
Fair Value, Recurring \| Level 1 \| US Treasuries
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Short-term investments	205,976	192,275
Long-term investments	22,167	132,589
Fair Value, Recurring \| Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total	91,366	113,364
Fair Value, Recurring \| Level 2 \| Corporate Bonds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents		10,499
Short-term investments	68,228	72,923
Long-term investments	$ 23,138	$ 29,942

Fair Value Measurements - Additional Information (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
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 assets, level 1 to level 3 transfers, amount	0	0
Fair value assets, level 3 to level 1 transfers, amount	0	0
Fair value assets, level 3 to level 2 transfers, amount	0	0
Fair value assets, level 2 to level 3 transfers, amount	$ 0	$ 0

Marketable Securities - Summary of Available-for-Sale Debt Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Amortized Cost	$ 319,509	$ 427,863
Unrealized Gains	20
Unrealized Losses	(20)	(134)
Fair Value	319,509	427,729
U.S. Treasury Securities
Marketable Securities [Line Items]
Amortized Cost	228,130	324,917
Unrealized Gains	18
Unrealized Losses	(5)	(53)
Fair Value	228,143	324,864
Corporate Securities
Marketable Securities [Line Items]
Amortized Cost	91,379	102,946
Unrealized Gains	2
Unrealized Losses	(15)	(81)
Fair Value	$ 91,366	$ 102,865

Marketable Securities - Additional Information (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($) Security	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) Security	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) Security
Marketable Securities [Abstract]
Number of available-for-sale debt securities, continuous unrealized loss position for less than 12 months \| Security	28		28		65
Aggregate fair value of available-for-sale debt securities, continuous unrealized loss position for less than 12 months \| $	$ 91,000,000.0		$ 91,000,000.0		$ 392,200,000
Number of available-for-sale debt securities, contractual maturity of less than 12 months \| Security			43		48
Fair value of available-for-sale debt securities, contractual maturity of less than 12 months \| $	274,200,000		$ 274,200,000		$ 295,600,000
Number of available-for-sale debt securities, contractual maturity of greater than 12 months \| Security			12		25
Fair value of available-for-sale debt securities, contractual maturity of greater than 12 months \| $	45,305,000		$ 45,305,000		$ 162,531,000
Sales of marketable securities \| $	$ 0	$ 0	$ 0	$ 0
Number of securities decline in market value for in an unrealized loss position \| Security			28

Collaborations - Additional Information (Details)						3 Months Ended		6 Months Ended		12 Months Ended
Collaborations - Additional Information (Details)	Aug. 20, 2020	Jul. 07, 2020 USD ($)	May 09, 2019 USD ($) $ / shares shares	Nov. 01, 2018	Oct. 31, 2017 shares	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($) shares	Dec. 31, 2020 USD ($) shares
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development						$ 35,220,000	$ 13,819,000	$ 61,181,000	$ 25,935,000
Revenue recognized						18,519,000	3,288,000	37,221,000	6,716,000
Stock split, conversion ratio	1.5949
Sanofi Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment		$ 150,000,000.0
Collaboration agreement transaction price		150,000,000.0
Revenue recognized recorded in deferred revenue						14,400,000		26,000,000.0
Unsatisfied performance obligation						108,400,000		108,400,000		$ 132,600,000
Cost reimbursement payment received								1,700,000
Milestone receivable						0		0
Royalty receivable						0		0
Unbilled accounts receivable						900,000		$ 900,000
Research and development						0
Remaining research term of collaboration								2 years 8 months 12 days
Sanofi Agreement \| Collaboration Target 1
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement transaction price		120,000,000.0
Revenue recognized recorded in deferred revenue						12,000,000.0		$ 21,500,000
Sanofi Agreement \| Collaboration Target 2
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement transaction price		30,000,000.0
Revenue recognized recorded in deferred revenue						2,400,000		4,500,000
Sanofi Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone payments		1,480,000,000
Commercial Milestone Payments		700,000,000.0
Sanofi Agreement \| Minimum \| IRAK4 Program
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone payments		1,000,000,000.0
Commercial Milestone Payments		$ 400,000,000.0
Vertex Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized recorded in deferred revenue								11,200,000
Unsatisfied performance obligation						26,500,000		26,500,000		37,700,000
Initial research term of collaboration			4 years
Extended research term of collaboration			1 year
Revenue recognized						$ 4,100,000	$ 3,300,000	$ 11,200,000	6,700,000
Vertex Agreement \| Series B-1 Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement transaction price			$ 55,900,000
Non refundable upfront payment received			$ 50,000,000.0
Number of shares issued \| shares			3,059,695
Stock issued price per share \| $ / shares			$ 6.54
Preferred stock premium			$ 5,900,000
Vertex Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Eligible to receive payments including development, regulatory and commercial milestones			$ 170,000,000.0
Revenue remaining research term						1 year 3 months 18 days		1 year 3 months 18 days
Compound Collaboration
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period to terminate collaboration agreement								60 days
Compound Collaboration \| Series A Preferred Units
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development									$ 200,000	$ 200,000
Number of shares issued \| shares					886,305
Stock split, conversion ratio				100
Share-based compensation vesting period				3 years
Number of shares vested \| shares									110,788	110,788

Collaborations - Change in Accounts Receivable, Contract Asset and Liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable and contract assets, Beginning balance	$ 1,433
Accounts receivable and contract assets, Additions	3,484
Accounts receivable and contract assets, Deductions	(4,013)
Accounts receivable and contract assets, Ending balance	904
Contract Liabilities, Beginning balance	170,390
Contract Liabilities, Additions	1,766
Contract Liabilities, Deductions	(37,221)
Contract Liabilities, Ending balance	134,935
Billed Receivables - Sanofi
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable and contract assets, Beginning balance	577
Accounts receivable and contract assets, Additions	1,718
Accounts receivable and contract assets, Deductions	(2,295)
Unbilled Receivables - Sanofi
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable and contract assets, Beginning balance	856
Accounts receivable and contract assets, Additions	1,766
Accounts receivable and contract assets, Deductions	(1,718)
Accounts receivable and contract assets, Ending balance	904
Deferred Revenue - Vertex
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Beginning balance	37,748
Contract Liabilities, Deductions	(11,226)
Contract Liabilities, Ending balance	26,522
Deferred Revenue - Sanofi
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Beginning balance	132,642
Contract Liabilities, Additions	1,766
Contract Liabilities, Deductions	(25,995)
Contract Liabilities, Ending balance	$ 108,413

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 15,294	$ 12,988
Less accumulated depreciation	(3,176)	(2,147)
Property and equipment, net	12,118	10,841
Lab and Office Equipment Under Finance Right of Use Asset
Property Plant And Equipment [Line Items]
Total property and equipment	4,003	2,771
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	2,373	1,636
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	266	89
Furniture & Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	921	861
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 7,731	7,599
Assets Not Yet in Service
Property Plant And Equipment [Line Items]
Total property and equipment		$ 32

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Depreciation expense	$ 600	$ 400	$ 1,000	$ 800
Property and equipment right of use assets under finance leases with cost basis	15,294		15,294		$ 12,988
Amortization expense related to right-of-use assets	193	$ 195	371	$ 356
Lab and Office Equipment Under Finance Right of Use Asset
Property Plant And Equipment [Line Items]
Property and equipment right of use assets under finance leases with cost basis	4,003		4,003		2,771
Accumulated amortization	$ 1,500		$ 1,500		$ 1,200

Leases - Additional Information (Details) $ in Millions	1 Months Ended
Leases - Additional Information (Details) $ in Millions	Mar. 31, 2020 USD ($)	Oct. 31, 2019 USD ($) ft²	Apr. 30, 2019 ft²	Jun. 30, 2021 USD ($)	Oct. 31, 2020 USD ($)	Feb. 28, 2018 ft²
Cambridge, Massachusetts \| Noncancelable Facility Lease Agreement
Lessee Lease Description [Line Items]
Area of office space \| ft²						9,836
Reduction of right-of-use asset and liability due to lease modification	$ 2.2
Lease termination date	Jul. 31, 2020
Cambridge, Massachusetts \| Noncancelable Facility Lease Agreement \| Prepaid Expenses and Other Current Assets \| Letter of Credit
Lessee Lease Description [Line Items]
Security deposit					$ 0.2
Cambridge, Massachusetts \| Facility Sublease Agreement
Lessee Lease Description [Line Items]
Area of office space \| ft²			1,471
Sublease commencement date			Jun. 24, 2019
Watertown, Massachusetts \| Noncancelable Facility Lease Agreement
Lessee Lease Description [Line Items]
Area of office space \| ft²		34,522
Lease term		120 months
Lease expiration date		Mar. 31, 2030
Lease additional term		5 years
Tenant incentive allowance receivable		$ 5.5
Watertown, Massachusetts \| Noncancelable Facility Lease Agreement \| Restricted Cash \| Letter of Credit
Lessee Lease Description [Line Items]
Security deposit				$ 1.6

Leases - Components of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating lease costs	$ 524	$ 673	$ 1,047	$ 1,562
Amortization expense related to right-of-use assets	193	195	371	356
Interest expense for finance lease liabilities	21	31	37	65
Variable lease costs	153	94	385	201
Total lease costs	$ 891	$ 993	$ 1,840	$ 2,184

Leases - Supplemental Cash Flow Information Relating to Leases (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating cash flows used in (provided by) operating leases	$ 1,428	$ (3,905)
Operating cash flows used in finance leases	350	309
Financing cash flows used in finance leases	$ 37	$ 65

Leases - Summary of Weighted Average Remaining Lease Terms and Discount Rates (Details)	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating lease, remaining lease term	8 years 10 months 2 days	9 years 9 months 18 days
Finance lease, remaining lease term	2 years 8 months 4 days	3 years 3 months 18 days
Operating lease, discount rate	10.50%	10.50%
Finance lease, discount rate	8.51%	7.90%

Leases - Summary of Undiscounted Future Lease Payments for Operating and Finance Leases (Details) $ in Thousands	Jun. 30, 2021 USD ($)
Operating Leases
2021 (excluding the first and second quarter)	$ 1,262
2022	2,581
2023	2,659
2024	2,732
2025	2,814
Thereafter	12,925
Total minimum lease payments	24,973
Less amounts representing interest or imputed interest	(8,852)
Present value of lease liabilities	16,121
Finance Leases
2021 (excluding the first and second quarter)	588
2022	924
2023	710
2024	194
Total minimum lease payments	2,416
Less amounts representing interest or imputed interest	(233)
Present value of lease liabilities	$ 2,183

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued Liabilities Current [Abstract]
Research and development expenses	$ 10,504	$ 5,821
Payroll and payroll-related	2,319	2,918
Professional fees	1,590	1,585
Other	255	6
Accrued expenses	$ 14,668	$ 10,330

Other Commitments and Contingencies - Additional Information (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Indemnified Parties
Loss Contingencies [Line Items]
Liabilities accrued	$ 0	$ 0

Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended		6 Months Ended
	Aug. 21, 2020	Mar. 31, 2020	Jan. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Aug. 20, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Deemed dividend from exchange of convertible preferred stock						$ 9,050
Common Stock
Temporary Equity [Line Items]
Conversion of stock, shares issued and outstanding	50,439,595
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, issued			1,182,265
Convertible Preferred Stock, par or stated value per share			$ 4.06
Proceeds from issuance of convertible preferred stock			$ 4,800			4,800
Stock issuance costs				$ 0		$ 0
Convertible Preferred Stock, authorized							16,009,845
Convertible Preferred Stock, outstanding		16,009,845		16,009,845	16,009,845	16,009,845		14,827,580
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, issued		15,527,943			15,527,943
Proceeds from issuance of convertible preferred stock						$ 88,181
Stock issuance costs				$ 320		320
Shares issued upon exchange of Series A convertible preferred stock		1,988,802			1,988,802
Deemed dividend from exchange of convertible preferred stock					$ 9,100	$ 9,100
Reduction of additional paid-in-capital related to temporary equity deemed dividend					2,300
Increase in accumulated deficit related to temporary equity deemed dividend					$ 6,700
Convertible Preferred Stock, authorized							15,527,943
Convertible Preferred Stock, outstanding		15,527,943		15,527,943	15,527,943	15,527,943
Series C Convertible Preferred Stock \| Series C SPA
Temporary Equity [Line Items]
Convertible Preferred Stock, issued		13,539,141			13,539,141
Convertible Preferred Stock, par or stated value per share		$ 6.5366			$ 6.5366
Proceeds from issuance of convertible preferred stock		$ 88,200
Stock issuance costs		$ 300
Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, issued	0
Convertible Preferred Stock, par or stated value per share							$ 0.0001
Convertible Preferred Stock, authorized							52,483,788
Number of preferred Stock converted to common stock	31,625,534
Convertible Preferred Stock, outstanding	0
Series Seed Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized							3,000,000
Convertible Preferred Stock, outstanding		3,000,000		3,000,000	3,000,000	3,000,000		3,000,000
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized							14,886,305
Convertible Preferred Stock, outstanding		12,786,718		12,842,112	12,786,718	12,842,112		14,720,126
Series B-1 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized							3,059,695
Convertible Preferred Stock, outstanding		3,059,695		3,059,695	3,059,695	3,059,695		3,059,695

Equity-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Aug. 20, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense	$ 5,726	$ 664	$ 8,898	$ 1,035
Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense	2,917	423	4,642	662
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of stock options exercised	$ 17,100	$ 0	$ 37,100	$ 100
Weighted-average fair value of options granted	$ 26.99	$ 3.32	$ 28.66	$ 3.62
Unrecognized stock-based compensation expense	$ 69,700		$ 69,700
Unrecognized compensation cost, recognition period			2 years 9 months 18 days
Equity-based compensation expense	5,613	$ 606	$ 8,684	$ 916
Stock Options \| Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense	2,821	$ 371	$ 4,458	553
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost, recognition period			1 year
Unrecognized stock-based compensation expense	$ 200		$ 200
Equity-based compensation expense			100	100
Restricted Stock \| Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense			$ 100	$ 100
2020 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance under plan					4,457,370
Maximum number of shares to be issued, percentage			4.00%
Shares remaining available for future grants	3,150,858		3,150,858
2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance under plan					445,653
Share-based compensation, description			The 2020 ESPP provides that the number of shares reserved and available for issuance will automatically increase on January 1, 2021 and each January 1 thereafter through January 1, 2030, by the least of (i) 438,898 shares of common stock, (ii) 1% of the Company’s outstanding number of shares of common stock on the immediately preceding December 31 or (iii) such lesser number of shares of common stock as determined by the administrator of the 2020 ESPP.
2020 ESPP \| Lesser of Potential Outcome 1
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional shares authorized			438,898
2020 ESPP \| Lesser of Potential Outcome 2
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares to be issued, percentage			1.00%
2018 Plan \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted	0	0	0	0

Equity-Based Compensation - Summary of Stock Option Activity (Details) - 2020 Plan $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Number of Options Outstanding
Outstanding at beginning of period \| shares	5,832,712
Granted \| shares	1,871,037
Exercised \| shares	(801,233)
Forfeited \| shares	(89,527)
Outstanding at end of period \| shares	6,812,989	5,832,712
Exercisable at June 30, 2021 \| shares	1,596,721
Weighted Average Strike Price Per Option
Outstanding at beginning of period \| $ / shares	$ 8.17
Granted \| $ / shares	49.07
Exercised \| $ / shares	3.27
Forfeited \| $ / shares	13.85
Outstanding at end of period \| $ / shares	19.90	$ 8.17
Exercisable at June 30, 2021 \| $ / shares	$ 7.48
Weighted Average Remaining Contractual Term (in years)
Outstanding	8 years 11 months 4 days	9 years 29 days
Exercisable at June 30, 2021	8 years 5 months 26 days
Aggregate Intrinsic Value
Outstanding at beginning of period \| $	$ 314,001
Outstanding at end of period \| $	197,003	$ 314,001
Exercisable at June 30, 2021 \| $	$ 65,526

Equity-Based Compensation - Summary of Equity-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	$ 5,726	$ 664	$ 8,898	$ 1,035
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	2,917	423	4,642	662
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	2,809	241	4,256	373
Stock Options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	5,613	606	8,684	916
Stock Options \| Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	2,821	371	4,458	553
Stock Options \| General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	$ 2,792	$ 235	$ 4,226	$ 363

Equity-Based Compensation - Summary of Weighted-Average Assumptions (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (in years)	5 years 10 months 13 days	6 years 3 months 7 days	5 years 9 months 29 days	6 years 2 months 19 days
Volatility	65.00%	70.00%	66.00%	78.00%
Risk-free interest rate	1.05%	0.41%	0.90%	0.65%
Dividend yield	0.00%	0.00%	0.00%	0.00%

Equity-Based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Stock - 2018 Plan	6 Months Ended
	Jun. 30, 2021 $ / shares shares
Number of Units Outstanding
Unvested at beginning of period \| shares	110,104
Vested \| shares	(36,582)
Unvested at end of period \| shares	73,522
Grant Date Fair Value per Share
Unvested at beginning of period \| $ / shares	$ 1.60
Vested \| $ / shares	1.60
Unvested at end of period \| $ / shares	$ 1.60

Related Party Transactions - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020
Investor
Related Party Transaction [Line Items]
Rent expenses	$ 0.0	$ 0.0	$ 0.4

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 0	$ 0	$ 0	$ 0
Net operating loss carryforwards period CARES Act			5 years
Net operating loss carryforwards percentage limitations on use CARES Act			80.00%
Expected income tax refund period CARES Act			18 months
Earliest Tax Year
Income Tax Disclosure [Line Items]
Net operating loss carryforwards year CARES Act			2018
Latest Tax Year
Income Tax Disclosure [Line Items]
Net operating loss carryforwards year CARES Act			2020

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Net Loss per Share - Summary of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss	$ (24,660)	$ (13,989)	$ (37,735)	$ (24,921)
Deemed dividend from exchange of convertible preferred stock				(9,050)
Net loss attributable to common stockholders	$ (24,660)	$ (13,989)	$ (37,735)	$ (33,971)
Weighted average common shares outstanding, basic and diluted	45,094,238	2,002,825	44,873,083	1,977,720
Net loss per share, basic and diluted	$ (0.55)	$ (6.98)	$ (0.84)	$ (17.18)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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+ Details

Net Loss per Share - Schedule of Diluted Net Loss Per Share Attributable to Common Stockholders Anti-Diluted Effect (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive stock	6,886,511	36,126,288
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive stock		31,625,534
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive stock	73,522	157,692
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive stock	6,812,989	4,343,062

Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended
	Jul. 06, 2021	Aug. 25, 2020	Jul. 31, 2021
Subsequent Events
Subsequent Event [Line Items]
Gross proceeds from issuance of common stock	$ 243.1
Follow-on Offering \| Subsequent Events
Subsequent Event [Line Items]
Common stock shares issued			5,468,250
Common stock per share			$ 47.00
Gross proceeds from issuance of common stock			$ 257.0
Underwriters
Subsequent Event [Line Items]
Common stock shares issued		1,302,720
Underwriters \| Subsequent Events
Subsequent Event [Line Items]
Common stock shares issued			713,250
Private Placement \| Vertex Pharmaceuticals Incorporated
Subsequent Event [Line Items]
Common stock shares issued		676,354
Common stock per share		$ 20.00
Aggregate proceeds from issuance of private placement		$ 13.5
Private Placement \| Subsequent Events \| Vertex Pharmaceuticals Incorporated
Subsequent Event [Line Items]
Common stock shares issued			49,928
Common stock per share			$ 47.00
Aggregate proceeds from issuance of private placement			$ 2.3