0001193125-20-291681 | 10-Q | XBRL Viewer

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Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2020	Nov. 10, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Registrant Name	Relay Therapeutics, Inc.
Entity Central Index Key	0001812364
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Address, State or Province	MA
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	RLAY
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		89,984,775

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 559,282	$ 41,954
Investments	154,184	313,862
Prepaid expenses and other current assets	8,384	4,720
Total current assets	721,850	360,536
Property and equipment, net	6,579	8,094
Operating lease assets	22,374	23,560
Restricted cash	878	878
Total assets	751,681	393,068
Current liabilities:
Accounts payable	4,553	6,991
Accrued expenses and other current liabilities	9,680	3,746
Operating lease liability	1,433	1,249
Total current liabilities	15,666	11,986
Operating lease liability, net of current portion	22,484	23,583
Restricted stock liability	6	156
Total liabilities	38,156	35,725
Commitments and contingencies (Note 9)
Convertible preferred stock (Series A, B and C), $0.001 par value; no shares authorized as of September 30, 2020 and 337,272,859 shares authorized as of December 31, 2019; no shares issued and outstanding as of September 30, 2020 and 212,642,857 shares issued and outstanding (aggregate liquidation preference of $519,825) as of December 31, 2019		537,781
Stockholders' equity (deficit):
Undesignated preferred stock, $0.001 par value, 10,000,000 shares authorized as of September 30, 2020 and no shares authorized as of December 31, 2019; no shares issued and outstanding at September 30,2020 and December 31, 2019	0
Common stock, $0.001 par value; 150,000,000 and 260,000,000 shares authorized at September 30,2020 and December 31, 2019, respectively; 89,977,603 and 4,716,634 shares issued at September 30, 2020 and December 31, 2019, respectively; 89,803,785 and 4,037,476 shares outstanding at September 30, 2020 and December 31, 2019, respectively	90	4
Additional paid-in capital	1,152,763	8,715
Accumulated other comprehensive income	176	325
Accumulated deficit	(439,504)	(189,482)
Total stockholders' equity (deficit)	713,525	(180,438)
Total liabilities, convertible preferred stock, and stockholders' equity (deficit)	$ 751,681	$ 393,068

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Common stock par value	$ 0.001	$ 0.001
Common stock shares authorized	150,000,000	260,000,000
Common stock shares issued	89,977,603	4,716,634
Common stock shares outstanding	89,803,785	4,037,476
Convertible Preferred Stock [Member]
Temporary equity par value	$ 0.001	$ 0.001
Temporary equity shares authorized	0	337,272,859
Temporary equity shares issued	0	212,642,857
Temporary equity shares outstanding	0	212,642,857
Temporary equity liquidation preference		$ 519,825
Undesignated Preferred Stock [Member]
Preferred stock par value	$ 0.001	$ 0.001
Preferred stock shares authorized	10,000,000	0
Preferred stock shares issued	0	0
Preferred stock shares outstanding	0	0

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating expenses:
Research and development expenses	$ 24,376	$ 18,256	$ 67,739	$ 47,899
General and administrative expenses	12,231	3,652	23,045	10,316
Total operating expenses	36,607	21,908	90,784	58,215
Loss from operations	(36,607)	(21,908)	(90,784)	(58,215)
Other income (expense):
Interest income	534	2,236	3,104	6,881
Other expense	(5)	(1)	(8)	(58)
Total other income (expense), net	529	2,235	3,096	6,823
Net loss	(36,078)	(19,673)	(87,688)	(51,392)
Deemed dividend resulting from extinguishment upon modification of Series C preferred stock	(177,789)		(177,789)
Net loss attributable to common stockholders	$ (213,867)	$ (19,673)	$ (265,477)	$ (51,392)
Net loss attributable to common stockholders per share, basic and diluted	$ (3.00)	$ (5.53)	$ (9.92)	$ (15.46)
Weighted average shares of common stock, basic and diluted	71,248,846	3,556,303	26,766,687	3,323,456
Other comprehensive income:
Unrealized holding gain (loss)	$ (455)	$ (68)	$ (149)	$ 407
Total other comprehensive income (loss)	(455)	(68)	(149)	407
Total comprehensive loss	$ (36,533)	$ (19,741)	$ (87,837)	$ (50,985)

Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]	Convertible Preferred Stock [Member]
Beginning balance at Dec. 31, 2018	$ (110,927)	$ 3	$ 3,247		$ (114,177)	$ 532,120
Beginning balance, shares at Dec. 31, 2018		2,998,017				210,863,764
Issuance of Series C preferred stock, net of issuance costs						$ 5,686
Issuance of Series C preferred stock, net of issuance costs, shares						1,779,093
Issuance of common stock upon exercise of stock options	29		29
Issuance of common stock upon exercise of stock options, shares		7,040
Vesting of restricted common stock	101		101
Vesting of restricted common stock ,shares		216,777
Stock-based compensation expense	820		820
Net loss	(14,182)				(14,182)
Ending balance at Mar. 31, 2019	(124,159)	$ 3	4,197		(128,359)	$ 537,806
Ending balance, shares at Mar. 31, 2019		3,221,834				212,642,857
Beginning balance at Dec. 31, 2018	(110,927)	$ 3	3,247		(114,177)	$ 532,120
Beginning balance, shares at Dec. 31, 2018		2,998,017				210,863,764
Net loss	(51,392)
Ending balance at Sep. 30, 2019	(158,291)	$ 4	6,867	$ 407	(165,569)	$ 537,781
Ending balance, shares at Sep. 30, 2019		3,701,910				212,642,857
Beginning balance at Mar. 31, 2019	(124,159)	$ 3	4,197		(128,359)	$ 537,806
Beginning balance, shares at Mar. 31, 2019		3,221,834				212,642,857
Series C preferred stock issuance costs						$ (21)
Issuance of common stock upon exercise of stock options	23		23
Issuance of common stock upon exercise of stock options, shares		16,897
Vesting of restricted common stock	100		100
Vesting of restricted common stock ,shares		216,777
Stock-based compensation expense	1,082		1,082
Unrealized gain(Loss) on investments	475			475
Net loss	(17,537)				(17,537)
Ending balance at Jun. 30, 2019	(140,016)	$ 3	5,402	475	(145,896)	$ 537,785
Ending balance, shares at Jun. 30, 2019		3,455,508				212,642,857
Series C preferred stock issuance costs						$ (4)
Issuance of common stock upon exercise of stock options	120		120
Issuance of common stock upon exercise of stock options, shares		31,581
Vesting of restricted common stock	98	$ 1	97
Vesting of restricted common stock ,shares		214,821
Stock-based compensation expense	1,248		1,248
Unrealized gain(Loss) on investments	(68)			(68)
Net loss	(19,673)				(19,673)
Ending balance at Sep. 30, 2019	(158,291)	$ 4	6,867	407	(165,569)	$ 537,781
Ending balance, shares at Sep. 30, 2019		3,701,910				212,642,857
Beginning balance at Dec. 31, 2019	(180,438)	$ 4	8,715	325	(189,482)	$ 537,781
Beginning balance, shares at Dec. 31, 2019		4,037,476				212,642,857
Issuance of common stock upon exercise of stock options	351		351
Issuance of common stock upon exercise of stock options, shares		85,845
Vesting of restricted common stock	98		98
Vesting of restricted common stock ,shares		210,516
Stock-based compensation expense	1,455		1,455
Unrealized gain(Loss) on investments	1,069			1,069
Net loss	(24,886)				(24,886)
Ending balance at Mar. 31, 2020	(202,351)	$ 4	10,619	1,394	(214,368)	$ 537,781
Ending balance, shares at Mar. 31, 2020		4,333,837				212,642,857
Beginning balance at Dec. 31, 2019	$ (180,438)	$ 4	8,715	325	(189,482)	$ 537,781
Beginning balance, shares at Dec. 31, 2019		4,037,476				212,642,857
Issuance of common stock upon exercise of stock options, shares	283,275
Net loss	$ (87,688)
Ending balance at Sep. 30, 2020	713,525	$ 90	1,152,763	176	(439,504)
Ending balance, shares at Sep. 30, 2020		89,803,785
Beginning balance at Mar. 31, 2020	(202,351)	$ 4	10,619	1,394	(214,368)	$ 537,781
Beginning balance, shares at Mar. 31, 2020		4,333,837				212,642,857
Issuance of common stock upon exercise of stock options	367		367
Issuance of common stock upon exercise of stock options, shares		95,573
Vesting of restricted common stock	47	$ 1	46
Vesting of restricted common stock ,shares		163,321
Stock-based compensation expense	4,032		4,032
Unrealized gain(Loss) on investments	(763)			(763)
Net loss	(26,724)				(26,724)
Ending balance at Jun. 30, 2020	(225,392)	$ 5	15,064	631	(241,092)	$ 537,781
Ending balance, shares at Jun. 30, 2020		4,592,731				212,642,857
Extinguishment upon modification of Series C preferred stock	(177,789)		(15,455)		(162,334)	$ 177,789
Conversion of convertible preferred stock into common stock upon initial public offering	715,570	$ 62	715,508			$ (715,570)
Conversion of convertible preferred stock into common stock upon initial public offering, shares		61,992,534				(212,642,857)
Issuance of common stock in public offering, net of discounts and issuance costs of $34,707	425,293	$ 23	425,270
Issuance of common stock in public offering, net of discounts and issuance costs of $34,707, shares		23,000,000
Issuance of common stock upon exercise of stock options	442		442
Issuance of common stock upon exercise of stock options, shares		101,861
Vesting of restricted common stock	5		5
Vesting of restricted common stock ,shares		116,659
Stock-based compensation expense	11,929		11,929
Unrealized gain(Loss) on investments	(455)			(455)
Net loss	(36,078)				(36,078)
Ending balance at Sep. 30, 2020	$ 713,525	$ 90	$ 1,152,763	$ 176	$ (439,504)
Ending balance, shares at Sep. 30, 2020		89,803,785

Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (parenthetical) $ in Thousands	3 Months Ended
	Sep. 30, 2020 USD ($)
Statement of Stockholders' Equity [Abstract]
Net of discounts and issuance costs	$ 34,707

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (87,688)	$ (51,392)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	17,416	3,150
Depreciation expense	2,637	1,992
Net amortization of premiums and discounts on investments	(430)	(1,860)
Loss on sale of equipment		56
Changes in assets and liabilities:
Prepaid expenses and other current assets	(3,664)	(1,102)
Lease assets and liabilities, net	271	1,136
Accounts payable	(1,693)	653
Accrued expenses and other liabilities	5,934	3,995
Net cash used in operating activities	(67,217)	(43,372)
Cash flows from investing activities:
Purchases of property and equipment	(1,867)	(7,404)
Proceeds from sale of equipment		20
Purchases of investments	(140,097)	(464,537)
Proceeds from maturities of investments	300,056	117,000
Net cash provided by (used in) investing activities	158,092	(354,921)
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net of issuance costs		5,661
Proceeds from issuance of common stock upon exercise of stock options	1,160	172
Proceeds from issuance of common stock upon initial public offering	427,800
Offering costs paid	(2,507)
Net cash provided by financing activities	426,453	5,833
Net increase (decrease) in cash, cash equivalents and restricted cash	517,328	(392,460)
Cash, cash equivalents and restricted cash at beginning of period	42,832	422,383
Cash, cash equivalents and restricted cash at end of period	560,160	29,923
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment additions included in accounts payable and accrued expenses		24
Reclassification of restricted stock liability to additional paid in capital	150	$ 299
Extinguishment upon modification of series C preferred stock	(177,789)
Conversion of preferred stock into common stock upon initial public offering	$ 715,508

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Restricted Cash And Cash Equivalents At Carrying Value [Abstract]
Cash and cash equivalents	$ 559,282	$ 41,954	$ 29,045
Restricted cash	878	878	878
Total cash, cash equivalents and restricted cash as shown on consolidated statements of cash flows	$ 560,160	$ 42,832	$ 29,923	$ 422,383

Nature of Business and Basis of Presentation

9 Months Ended

Sep. 30, 2020

Text Block [Abstract]

Nature of Business and Basis of Presentation

1. Nature of Business and Basis of Presentation

Relay Therapeutics, Inc. (the “Company”) was incorporated in Delaware on May 4, 2015 and is headquartered in Cambridge, Massachusetts. The Company is a clinical-stage precision medicines company transforming the drug discovery process with an initial focus on enhancing small molecule therapeutic discovery in targeted oncology. The Company is built upon unparalleled insights into protein motion and how this dynamic behavior relates to protein function. The Company’s Dynamo platform integrates an array of leading edge experimental and computational approaches, which allows the Company to apply the understanding of protein structure and motion to drug discovery. The Company is advancing its lead product candidates,

RLY-4008

and

RLY-1971,

and a development candidate selection for a PI3Kα selective mutant program, known as the

RLY-PI3K1047

program, for the treatment of patients with advanced solid tumors. The Company initiated a Phase 1 clinical trial for

RLY-1971

in patients with advanced solid tumors in the first quarter of 2020 and a first-in-human clinical trial of

RLY-4008

enriched for patients with advanced solid tumors having oncogenic FGFR2 alterations in September 2020.

The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. Product candidates currently under development will require significant additional research and development efforts, including extensive

pre-clinical

and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities.

The Company’s product candidates are in development. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants.

The Company has devoted substantially all of its resources to developing its product candidates, including

RLY-1971

and

RLY-4008,

and the

RLY-PI3K1047

program by developing its innovative experimental and computational approaches on protein motion, building its intellectual property portfolio, business planning, raising capital and providing general and administrative support for these operations.

The Company has incurred net operating losses since inception and had an accumulated deficit of $439,504 as of September 30, 2020. The Company expects that its existing cash, cash equivalents and investments as of September 30, 2020 will enable it to fund its planned operating expenses and capital expenditure requirements for at least one year from the date of the issuance of these condensed consolidated financial statements. The future viability of the Company is dependent on its ability to generate cash from operating activities or to raise additional capital to finance its operations. The Company’s failure to raise capital as and when needed could have a material adverse effect on its financial condition and ability to pursue its business strategies. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaboration arrangements or obtain government grants. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. In the event the Company requires additional funding, there can be no assurance that it will be successful in obtaining sufficient funding on terms acceptable to the Company to fund its continuing operations, if at all.

Initial Public Offering

On July 20, 2020, the Company closed its initial public offering (“IPO”) and issued 23,000,000 shares of its common stock at a price of $20.00 per share for net proceeds of $425,293, after deducting underwriting discounts and commissions of $32,200 and expenses of $2,507. In connection with the IPO, all shares of Series A, Series B and Series C convertible preferred stock converted into 61,992,534 shares of common stock.

Reverse Stock Split

On July 8, 2020, the Company’s stockholders approved a decrease in the number of authorized shares of common stock from 260,000,000 to 150,000,000. The Company also effected a

one-for-3.55092

reverse stock split of its issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each series of the Company’s

referred

tock. Accordingly, all share and per share amounts for all periods presented in the accompanying financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this reverse stock split and adjustment of the preferred stock conversion ratios.

Significant Accounting Policies

9 Months Ended

Sep. 30, 2020

Accounting Policies [Abstract]

Significant Accounting Policies

2. Significant Accounting Policies

Basis of presentation

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) for interim information and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) for reporting on Form

10-Q.

The Company’s consolidated financial statements include the accounts of Relay Therapeutics, Inc. and its wholly-owned subsidiary, Relay Therapeutics Securities Corporation. All intercompany balances and transactions have been eliminated.

Unaudited Interim Financial Information

The accompanying consolidated balance sheet as of September 30, 2020, the consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019, the consolidated statements of convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2020 and 2019, and the consolidated statements of cash flows for the nine months ended September 30, 2020 and 2019 are unaudited. The unaudited consolidated interim financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the Company’s consolidated financial position as of September 30, 2020 and the consolidated results of its operations and cash flows for the three and nine months ended September 30, 2020 and 2019. The consolidated financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2020 and 2019 are unaudited. The consolidated results for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020, any other interim periods, or any future year or period.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual of research and development and manufacturing expenses, the valuation of equity instruments, the probability of achieving milestones for performance-based vesting of equity awards, and the incremental borrowing rate for determining the operating lease asset and liability. Estimates are periodically reviewed in light of changes in circumstances, facts and experience.

The full extent to which the

COVID-19

pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including expenses, clinical trials and research and development costs, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning

COVID-19

and the actions taken to contain or treat

COVID-19,

as well as the economic impact on local, regional, national and international markets. The Company has made estimates of the impact of

COVID-19

within its financial statements and there may be changes to those estimates in future periods. Actual results could differ from the Company’s estimates.

Recently Adopted Accounting Pronouncements

The Company adopted ASU

No. 2018-13,

Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement

on January 1, 2020. This standard modifies certain disclosure requirements on fair value measurements. The adoption of this standard did not have a material impact on the Company’s disclosures.

Recently Issued Accounting Pronouncements Not Yet Adopted

In June 2016, the

Financial Accounting Standards Board

(“FASB”)

issued ASU No.

2016-13,

Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

. This standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and it establishes additional disclosure requirements related to credit risks. For

available-for-sale

debt securities with expected credit losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This guidance was originally effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption was permitted. In November 2019, the FASB subsequently issued ASU

2019-10,

Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging

(Topic 815), and Leases (Topic 842): Effective Dates

, whereby the effective date of this standard for smaller reporting companies was deferred to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years, and early adoption is still permitted.

In August 2020, the FASB issued ASU No. 2020-06,

Debt – Debt with Conversion and Other

Options

(Subtopic

470-20)

and Derivatives and Hedging—Contracts in Entity

’

s Own Equity

(Subtopic

815-40).

This standard amends the guidance on convertible instruments and the derivatives scope exception for contracts in an entity’s own equity and amends the related earnings per share (“EPS”) guidance. The ASU will be effective for smaller reporting companies for fiscal years beginning after December 15, 2023 and interim periods within those fiscal years. Early adoption is permitted in fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. The Company is assessing the impact of ASU

2020-06 on

the condensed consolidated financial statements and does not expect it to have a material impact.

In December 2019, the FASB

issued ASU 2019-12,

Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

(“ASU 2019-12”),

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 certain aspects of the existing guidance to improve consistent application. The new standard will be effective for public business entities for fiscal years beginning after December 15, 2020. The Company is currently evaluating the potential

impact ASU 2019-12 may

have on its financial position and results of operations upon adoption.

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 and has elected to use the extended transition period related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different effective dates for public and nonpublic companies, the Company can adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and can do so until such time that the Company either (i) irrevocably elects to “opt out” of such extended transition period or (ii) no longer qualifies as an emerging growth company.

Fair Value of Financial Assets

9 Months Ended

Sep. 30, 2020

Fair Value Disclosures [Abstract]

Fair Value of Financial Assets

3. Fair Value of Financial Assets

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values:


	Fair Value Measurements as of September 30, 2020:
	Level 1		Level 2		Level 3		Total
Assets
Cash equivalents:
Money market funds	$	558,782	$	—	$	—	$	558,782
Investments:
US treasury bills		—		57,172		—		57,172
US agency securities		—		97,012		—		97,012

Total investments		—		154,184		—		154,184

Total	$	558,782	$	154,184	$	—	$	712,966


	Fair Value Measurements as of December 31, 2019:
	Level 1		Level 2		Level 3		Total
Assets
Cash equivalents:
Money market funds	$	41,658	$	—	$	—	$	41,658
Investments:
US treasury bills		—		232,604		—		232,604
US agency securities		—		81,258		—		81,258

Total investments		—		313,862		—		313,862

Total	$	41,658	$	313,862	$	—	$	355,520

In determining the fair value of its investments at each date presented above, the Company relied on quoted prices for similar securities in active markets or using other inputs that are observable or can be corroborated by observable market data. The Company did not have any financial assets or liabilities that required Level 3 inputs during any of the periods presented in the accompanying consolidated financial statements.

- 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

Investments

9 Months Ended

Sep. 30, 2020

Schedule of Investments [Abstract]

Investments

4. Investments

The fair value of

available-for-sale

investments by type of security was as follows:


	September 30, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Investments:
U.S treasury bills	$	57,009	$	163	$	—	$	57,172
U.S agency securities		96,999		13		—		97,012

Total investments	$	154,008	$	176	$	—	$	154,184


	December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Investments:
U.S treasury bills	$	232,336	$	268	$	—	$	232,604
U.S agency securities		81,201		57		—		81,258

Total investments	$	313,537	$	325	$	—	$	313,862

All

available-for-sale

securities have contractual maturities of less than one year.

Convertible Preferred Stock

9 Months Ended

Sep. 30, 2020

Temporary Equity Disclosure [Abstract]

Convertible Preferred Stock

5. Convertible Preferred Stock

The Company issued Series A, Series B and Series C convertible preferred stock (collectively, “Convertible Preferred Stock”). Upon issuance of each class of Convertible Preferred Stock, the Company assessed the embedded conversion and liquidity features of the shares and determined that such features did not require the Company to separately account for these features. The Company also concluded that no beneficial conversion feature existed on the issuance date of each class of Convertible Preferred Stock. The Company’s Convertible Preferred Stock was classified outside of stockholders’ equity (deficit) on the consolidated balance sheet prior to the Company’s IPO because the holders of such shares had liquidation rights in the event of a deemed liquidation that, in certain situations, were not solely within the control of the Company and would require the redemption of the then-outstanding Convertible Preferred Stock. The Convertible Preferred Stock was not redeemable, except in the event of a deemed liquidation. Because the occurrence of a deemed liquidation event was not currently probable, the carrying values of the Convertible Preferred Stock were not accreted to their redemption values. The rights and preferences for Convertible Preferred Stock are detailed in audited financial statements included in the Company’s final prospectus filed with the Securities and Exchange Commission pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended, on July 16, 2020.

On July 8, 2020, the Company’s board of directors and its Series C preferred stockholders approved a reduction in the conversion price of the Series C preferred stock from $3.21 to $3.027603 and the Series C preferred stockholders relinquished their protective right with respect to the approval of an automatic conversion of preferred stock in a firm commitment underwritten public offering if the per share price is less than $22.80. As a result of the change in the conversion price, the outstanding shares of Series C preferred stock were convertible into 37,206,604 shares of common stock. The changes to the conversion feature are considered to be a significant change to the substantive contractual terms of the Series C preferred stock, and, therefore, the Company accounted for the changes as an extinguishment and reissuance

of the Series C preferred stock, which requires the difference between the fair value of the modified Series C preferred stock and its carrying amount to be treated in a manner similar to the treatment of dividends paid on preferred stock.

Upon the closing of the Company’s IPO in July 2020, all outstanding Convertible Preferred Stock automatically converted into

61,992,534 shares of common stock. No

Convertible Preferred Stock was outstanding as of September 30, 2020.

Common Stock

9 Months Ended

Sep. 30, 2020

Stockholders' Equity Note [Abstract]

Common Stock

6. Common Stock

The Company has issued restricted shares of common stock to its founders and

non-employees.

In addition, the Company has issued restricted shares of common stock upon the early exercise of stock options under the Company’s 2016 Stock Option and Grant Plan (the “2016 Stock Plan”). The restrictions on the common shares generally lapse over four years. The Company has included the proceeds from the sale of the restricted shares of common stock as a restricted stock liability in the accompanying consolidated balance sheets. Amounts are reclassified to additional

paid-in

capital as the restrictions lapse. The Company has the right to repurchase any unvested shares of restricted common stock at the original cost in the event of termination.

The following table summarizes the restricted stock activity for the nine months ended September 30, 2020:


	Shares			Weighted- Average Purchase Price
Unvested at December 31, 2019		679,158		$	0.21
Vested		(490,496	)		0.30
Cancelled		(14,844	)		0.03

Unvested at September 30, 2020		173,818		$	0.04

Employee Stock Purchase Plan

On July 8, 2020, the Company’s shareholders approved the 2020 Employee Stock Purchase Plan (the “ESPP”). The ESPP became effective on the date immediately prior to the effectiveness of Company’s registration statement on Form

S-1

for its IPO. The ESPP provides for the issuance of up to 1,092,532 of share-based awards. As of September 30, 2020, no shares have been issued under the ESPP.

Share-Based Payments

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

Share-Based Payments

7. Share-Based Payments

In 2016, the Company adopted the 2016 Stock Plan. On July 8, 2020, the Company’s shareholders approved the 2020 Stock Option and Incentive Plan (the “2020 Stock Plan”), which became effective on the date immediately prior to the effectiveness of the Company’s registration statement on Form

S-1

for its IPO. The 2020 Stock Plan provides for the issuance of up to 8,376,080 of share-based awards. All of the Company’s employees, officers, directors and consultants are eligible to be granted options, restricted stock units (“RSUs”) and other stock-based awards under the terms of the 2020 Stock Plan. There were 8,275,722 share-based awards available for grant at September 30, 2020.

Subsequent to July 20, 2020, no

further

awards will be made under the 2016 Stock Plan and all future equity-based awards will be granted under the 2020

Stock

Plan. To the extent outstanding options granted under the 2016 Plan are cancelled, forfeited or otherwise terminated without being exercised and would otherwise have been returned to the share reserve under the 2016 Plan, the number of shares underlying such awards will be available for future grant under the 2020 Stock Plan.

The following table summarizes the stock option activity under the 2016 Stock Plan and the 2020 Stock Plan for the nine months ended September 30, 2020:


	Number of Stock Options			Weighted- Average Exercise Price		Weighted- Average Remaining Term (years)		Aggregate Intrinsic Value
Outstanding at December 31, 2019		5,306,176		$	4.62		8.99	$	3,214
Granted		2,649,713			7.67
Exercised		(283,275	)		4.09
Cancelled		(210,835	)		4.91

Outstanding at September 30, 2020		7,461,779		$	5.71		8.71	$	275,178

Vested at September 30, 2020		1,696,242		$	4.42		8.06	$	64,744

In the first quarter of 2020, the Company’s board of directors approved the issuance of options with performance-based vesting conditions to purchase 1,960,547 shares of common stock. The commencement of vesting is based on the achievement of certain scientific and operational milestones during a

two-year

period, for which the achievement is discretionary and subject to the approval of the Company’s board of directors. Accordingly, the Company is applying variable accounting for these awards until the board of directors approves the commencement of vesting of the options. The service inception date precedes the grant date for these awards as the awards have been authorized, the recipients are providing service prior to the grant date, and there are performance conditions that, if not met by the accounting grant date, would result in the forfeiture of the award. Therefore, the stock-based compensation expense to be recognized for the options is based on the fair value of the awards on the accounting grant date. The Company’s board of directors, in its discretion, determined that a portion of the performance conditions had been achieved during the second quarter of 2020. The Company has made a probability assessment of the likelihood for achievement of the remaining conditions as of September 30, 2020. The Company recognized stock-based compensation expense associated with the options for which the board of directors approved the commencement of vesting and for awards where achievement of the performance conditions is considered probable in the amount of $10,324

and $12,947

in the statement of operations for the

three and

nine month period

ended September 30, 2020

, respectively

Stock-based compensation expense included in the Company’s consolidated statements of operations and comprehensive loss is as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Research and development expenses	$	5,367	$	734	$	8,205	$	1,935
General and administrative expenses		6,562		514		9,211		1,215

	$	11,929	$	1,248	$	17,416	$	3,150

As of September 30, 2020, total unrecognized compensation cost related to the unvested stock-based awards was $55,762, which is expected to be recognized over a weighted average period of 2.64 years.

Net Loss Per Share

9 Months Ended

Sep. 30, 2020

Earnings Per Share [Abstract]

Net Loss Per Share

8. Net Loss Per Share

The following table summarizes the computation of basic and diluted net loss per share of the Company:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2020			2019			2020			2019
Net loss	$	(36,078	)	$	(19,673	)	$	(87,688	)	$	(51,392	)

Deemed dividend resulting from extinguishment upon modification of series C preferred stock	$	(177,789	)		—		$	(177,789	)		—
Net loss attributable to common shareholders	$	(213,867	)	$	(19,673	)	$	(265,477	)	$	(51,392	)

Net loss per share attributable to common shareholders, basic and diluted	$	(3.00	)	$	(5.53	)	$	(9.92	)	$	(15.46	)

Weighted average shares of common stock, basic and diluted		71,248,846			3,556,303			26,766,687			3,323,456

As discussed in Note 5, on July 8, 2020, the Company’s board of directors and its Series C preferred stockholders approved an amendment to the conversion preferences and rights of the Series C preferred stock which, among other changes, resulted in a reduction in the conversion price of the Series C preferred stock from $3.21 to $3.027603. The changes to the conversion feature are considered to be a significant change to the substantive contractual terms of the Series C preferred stock, and, therefore, the Company accounted for the changes as an extinguishment and reissuance of the Series C preferred stock. In accordance with SEC staff guidance codified in ASC

260-10-S99-2,

when equity classified preferred shares are extinguished, the difference between (1) the fair value of the consideration transferred to the holders of the preferred shares and (2) the carrying amount of the preferred shares, net of issuance costs, is subtracted from (or added back to) net income to arrive at income available to common stockholders in the calculation of EPS. This difference between fair value of consideration transferred and carrying amount of the preferred shares, also referred to as a “deemed dividend”, has therefore been added back to net loss above to derive net loss attributable to common shareholders.

The Company’s potentially dilutive securities, which include Convertible Preferred Stock (prior to the IPO), options to purchase common stock and unvested restricted stock, 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 is the same.

The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Convertible preferred stock		—		59,883,877		—		59,883,877
Options to purchase common stock		7,461,779		5,007,344		7,461,779		5,007,344
Unvested restricted stock		173,818		876,456		173,818		876,456

		7,635,597		65,767,677		7,635,597		65,767,677

Commitments and Contingencies

9 Months Ended

Sep. 30, 2020

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

9. Commitments and Contingencies

Intellectual Property License

The Company has a Collaboration and License Agreement with D. E. Shaw Research, LLC (“D. E. Shaw Research”). The agreement provides that the parties will jointly conduct research efforts with the goal of identifying and developing product candidates. The original term of the agreement was three years and required the Company to pay an annual fee of $1,000. On June 15, 2020, the Company and D. E. Shaw Research agreed to amend the Collaboration and License Agreement (the “Amended and Restated Collaboration and License Agreement”). The Amended and Restated Collaboration and License Agreement extended the term of the agreement to August 16, 2025 and increased the annual fee from $1,000 to $7,900. The Amended and Restated Collaboration and License Agreement automatically renews for successive one year periods unless either party provides at least one year notice of

non-renewal,

and the annual fee during each of the one year renewal terms is subject to the mutual agreement of the Company and D. E. Shaw Research.

The Company is obligated to pay potential development milestone payments under the terms of the agreement up to $7,300 per target, plus sales milestones and royalties, upon the achievement of certain specified contingent events. The Company assessed the milestone and royalty events at September 30, 2020 and December 31, 2019,

respectively,

and concluded no such payments were

due

. The Company recorded research and development expense of $1,845 and $250 under this agreement for the three months ended September 30, 2020 and 2019, respectively, and $3,069 and $750 for the nine months ended September 30, 2020 and 2019, respectively. At September 30, 2020 and December 31, 2019, the Company had an accrued expense balance to D. E. Shaw Research of approximately $2,941 and $372, respectively.

Other Research Arrangements

The Company has certain other research and license arrangements with third parties, which provide the Company with research services with the goal of identifying and developing product candidates. The Company is obligated to pay development milestone payments for up to four targets, each in the range of $4,000 to $7,000, upon the achievement of certain specified contingent events. The Company assessed the milestones at September 30, 2020 and December 31, 2019

, respectively,

and concluded no such milestone payments were due. The Company incurred approximately $235 and $245 of research and development expense under these agreements for the three months ended September 30, 2020 and 2019, respectively, and $1,665 and $871 for the nine months ended September 30, 2020 and 2019, respectively.

Other Commitments

In September 2020, the Company entered into an amendment to its existing facility lease agreement dated January 2018 to expand the leased area by approximately 1,824 square feet of office space at 399 Binney Street, Cambridge, Massachusetts. The amendment is effective as of October 2020 and expires in April 2029, subject to certain renewal options.

As the Company did not control the space as of September 30, 2020, no right of use asset or lease liability was recorded as of the balance sheet date.

In connection with the lease

amendment

, the Company has committed to making $1.3 million in rental payments

for the expansion space

over the lease term.

Related Party Transactions

9 Months Ended

Sep. 30, 2020

Related Party Transactions

10. Related Party Transactions

From inception to December 31, 2019, the Company received consulting and management services from Third Rock Ventures LLP (“TRV”), an entity affiliated with certain of the Company’s investors. There were no amounts incurred for these services in the three and nine months ended September 30, 2020 and no amount was due for these services as of September 30, 2020. The Company incurred approximately $121 for these services during the three months ended September 30, 2019 and $171 for the nine months ended September 30, 2019. At December 31, 2019, $80 was due to TRV for these services.

Subsequent Events

9 Months Ended

Sep. 30, 2020

Subsequent Events [Abstract]

Subsequent Events

11. Subsequent Events

In preparing the consolidated interim financial statements as of September 30, 2020 and for the three and nine month periods then ended

(unaudited),

the Company evaluated subsequent events for recognition and measurement purposes

through the filing date of this Quarterly Report on Form 10-Q

. The Company concluded that no events or transactions have occurred that require disclosure in the accompanying consolidated financial statements.

Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2020

Accounting Policies [Abstract]

Basis of presentation

10-Q.

Unaudited Interim Financial Information

Use of Estimates

The full extent to which the

COVID-19

and the actions taken to contain or treat

COVID-19,

as well as the economic impact on local, regional, national and international markets. The Company has made estimates of the impact of

COVID-19

within its financial statements and there may be changes to those estimates in future periods. Actual results could differ from the Company’s estimates.

Recently Adopted Accounting Pronouncements

The Company adopted ASU

No. 2018-13,

Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement

on January 1, 2020. This standard modifies certain disclosure requirements on fair value measurements. The adoption of this standard did not have a material impact on the Company’s disclosures.

Recently Issued Accounting Pronouncements Not Yet Adopted

In June 2016, the

Financial Accounting Standards Board

(“FASB”)

issued ASU No.

2016-13,

Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

available-for-sale

2019-10,

Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging

(Topic 815), and Leases (Topic 842): Effective Dates

In August 2020, the FASB issued ASU No. 2020-06,

Debt – Debt with Conversion and Other

Options

(Subtopic

470-20)

and Derivatives and Hedging—Contracts in Entity

’

s Own Equity

(Subtopic

815-40).

2020-06 on

the condensed consolidated financial statements and does not expect it to have a material impact.

In December 2019, the FASB

issued ASU 2019-12,

Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

(“ASU 2019-12”),

which is intended to simplify the accounting for income

taxes. ASU 2019-12 removes

impact ASU 2019-12 may

have on its financial position and results of operations upon adoption.

Fair Value of Financial Assets (Tables)

9 Months Ended

Sep. 30, 2020

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on a Recurring Basis and Level of the Fair Value Hierarchy


	Fair Value Measurements as of September 30, 2020:
	Level 1		Level 2		Level 3		Total
Assets
Cash equivalents:
Money market funds	$	558,782	$	—	$	—	$	558,782
Investments:
US treasury bills		—		57,172		—		57,172
US agency securities		—		97,012		—		97,012

Total investments		—		154,184		—		154,184

Total	$	558,782	$	154,184	$	—	$	712,966


	Fair Value Measurements as of December 31, 2019:
	Level 1		Level 2		Level 3		Total
Assets
Cash equivalents:
Money market funds	$	41,658	$	—	$	—	$	41,658
Investments:
US treasury bills		—		232,604		—		232,604
US agency securities		—		81,258		—		81,258

Total investments		—		313,862		—		313,862

Total	$	41,658	$	313,862	$	—	$	355,520

Investments (Tables)

9 Months Ended

Sep. 30, 2020

Schedule of Investments [Abstract]

Summary of Fair Value of Available-for-Sale Investments by Type of Security

The fair value of

available-for-sale

investments by type of security was as follows:


	September 30, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Investments:
U.S treasury bills	$	57,009	$	163	$	—	$	57,172
U.S agency securities		96,999		13		—		97,012

Total investments	$	154,008	$	176	$	—	$	154,184


	December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Investments:
U.S treasury bills	$	232,336	$	268	$	—	$	232,604
U.S agency securities		81,201		57		—		81,258

Total investments	$	313,537	$	325	$	—	$	313,862

Common Stock (Tables)

9 Months Ended

Sep. 30, 2020

Stockholders' Equity Note [Abstract]

Summary Of The Restricted Stock Activity

The following table summarizes the restricted stock activity for the nine months ended September 30, 2020:


	Shares			Weighted- Average Purchase Price
Unvested at December 31, 2019		679,158		$	0.21
Vested		(490,496	)		0.30
Cancelled		(14,844	)		0.03

Unvested at September 30, 2020		173,818		$	0.04

Share-Based Payments (Tables)

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

The following table summarizes the stock option activity under the 2016 Stock Plan and the 2020 Stock Plan for the nine months ended September 30, 2020:


	Number of Stock Options			Weighted- Average Exercise Price		Weighted- Average Remaining Term (years)		Aggregate Intrinsic Value
Outstanding at December 31, 2019		5,306,176		$	4.62		8.99	$	3,214
Granted		2,649,713			7.67
Exercised		(283,275	)		4.09
Cancelled		(210,835	)		4.91

Outstanding at September 30, 2020		7,461,779		$	5.71		8.71	$	275,178

Vested at September 30, 2020		1,696,242		$	4.42		8.06	$	64,744

Schedule of Stock-Based Compensation Expense Included In The Company's Consolidated Statements of Operations And Comprehensive Loss

Stock-based compensation expense included in the Company’s consolidated statements of operations and comprehensive loss is as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Research and development expenses	$	5,367	$	734	$	8,205	$	1,935
General and administrative expenses		6,562		514		9,211		1,215

	$	11,929	$	1,248	$	17,416	$	3,150

Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2020

Earnings Per Share [Abstract]

Summary of Computation of Basic and Diluted Net Loss Per Share

The following table summarizes the computation of basic and diluted net loss per share of the Company:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2020			2019			2020			2019
Net loss	$	(36,078	)	$	(19,673	)	$	(87,688	)	$	(51,392	)

Deemed dividend resulting from extinguishment upon modification of series C preferred stock	$	(177,789	)		—		$	(177,789	)		—
Net loss attributable to common shareholders	$	(213,867	)	$	(19,673	)	$	(265,477	)	$	(51,392	)

Net loss per share attributable to common shareholders, basic and diluted	$	(3.00	)	$	(5.53	)	$	(9.92	)	$	(15.46	)

Weighted average shares of common stock, basic and diluted		71,248,846			3,556,303			26,766,687			3,323,456

Summary of Antidilutive Securities Excluded From Computation of Earnings Per Share


	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Convertible preferred stock		—		59,883,877		—		59,883,877
Options to purchase common stock		7,461,779		5,007,344		7,461,779		5,007,344
Unvested restricted stock		173,818		876,456		173,818		876,456

		7,635,597		65,767,677		7,635,597		65,767,677

Nature of Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended	9 Months Ended
	Jul. 20, 2020	Jul. 08, 2020	Sep. 30, 2020	Sep. 30, 2020	Jul. 07, 2020	Dec. 31, 2019
Accumulated deficit			$ 439,504	$ 439,504		$ 189,482
Issuance of common stock in public offering	$ 425,293		$ 425,293
Proceeds from initial public offering	$ 2,507			$ 427,800
Number of shares issued in transaction	23,000,000
Sale price of stock	$ 20.00
Underwriting discounts and commissions	$ 32,200
Conversion of stock shares converted	61,992,534
Common Stock, Shares Authorized		150,000,000	150,000,000	150,000,000	260,000,000	260,000,000
Stockholders' Equity, Reverse Stock Split		one-for-3.55092

Fair Value of Financial Assets - Summary of Financial Assets Measured at Fair Value on a Recurring Basis and Level of the Fair Value Hierarchy (Detail) - Fair value on a recurring basis [Member] - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Investments:
Total	$ 712,966	$ 355,520
Investments [Member]
Investments:
Total investments	154,184	313,862
Money market funds [Member] \| Cash equivalents [Member]
Cash equivalents:
Assets, fair value	558,782	41,658
US treasury bills [Member] \| Investments [Member]
Cash equivalents:
Assets, fair value	57,172	232,604
US agency securities [Member] \| Investments [Member]
Cash equivalents:
Assets, fair value	97,012	81,258
Level 1 [Member]
Investments:
Total	558,782	41,658
Level 1 [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Cash equivalents:
Assets, fair value	558,782	41,658
Level 2 [Member]
Investments:
Total	154,184	313,862
Level 2 [Member] \| Investments [Member]
Investments:
Total investments	154,184	313,862
Level 2 [Member] \| US treasury bills [Member] \| Investments [Member]
Cash equivalents:
Assets, fair value	57,172	232,604
Level 2 [Member] \| US agency securities [Member] \| Investments [Member]
Cash equivalents:
Assets, fair value	$ 97,012	$ 81,258

Investments - Summary of Fair Value of Available-for-Sale Investments by Type of Security (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 154,008	$ 313,537
Unrealized Gains	176	325
Fair Value	154,184	313,862
U.S treasury bills [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	57,009	232,336
Unrealized Gains	163	268
Fair Value	57,172	232,604
U.S agency securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	96,999	81,201
Unrealized Gains	13	57
Fair Value	$ 97,012	$ 81,258

Convertible Preferred Stock - Additional Information (Detail) - $ / shares		9 Months Ended
	Jul. 08, 2020	Sep. 30, 2020	Jul. 31, 2020	Jul. 20, 2020
Outstanding convertible preferred stock automatically converted into common shares	37,206,604
Sale price of stock				$ 20.00
Series C preferred stock were convertible into common stock, Shares	37,206,604
Maximum [Member]
Sale price of stock	$ 22.80
Series C Preferred Stock [Member]
Preferred stock convertible conversion price	$ 3.027603	$ 3.21
IPO [Member]
Outstanding convertible preferred stock automatically converted into common shares		0	61,992,534
Series C preferred stock were convertible into common stock, Shares		0	61,992,534

Common Stock - Additional Information (Detail) - shares	9 Months Ended
Common Stock - Additional Information (Detail) - shares	Sep. 30, 2020	Jul. 08, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Restriction Period	4 years
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based awards, authorized for issuance	0	1,092,532

Common Stock - Summary Of The Restricted Stock Activity (Detail) - Restricted Stock [Member]	9 Months Ended
	Sep. 30, 2020 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares - Beginning \| shares	679,158
Shares - Vested \| shares	(490,496)
Shares - Cancelled \| shares	(14,844)
Shares - Ending \| shares	173,818
Weighted- Average Purchase Price - Beginning \| $ / shares	$ 0.21
Weighted- Average Purchase Price - Vested \| $ / shares	0.30
Weighted- Average Purchase Price - Cancelled \| $ / shares	0.03
Weighted- Average Purchase Price - Ending \| $ / shares	$ 0.04

Share-Based Payments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jul. 08, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 11,929		$ 1,248	$ 17,416	$ 3,150
Total unrecognized compensation cost related to the unvested stock-based awards, Value	55,762			$ 55,762
Total unrecognized compensation cost related to the unvested stock-based awards, Weighted average period				2 years 7 months 20 days
Operating Income (Loss) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 10,324			$ 12,947
2020 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Award, Number of Shares Authorized	8,275,722			8,275,722		8,376,080
2016 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award		1,960,547
Share-based Payment Award, Award Vesting Rights				The commencement of vesting is based on the achievement of certain scientific and operational milestones during a two-year period, for which the achievement is discretionary and subject to the approval of the Company's board of directors.

Share-Based Payments - Schedule of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Share-based Payment Arrangement [Abstract]
Options and Warrants Outstanding, Number of Shares Beginning Balance \| shares	5,306,176
Granted, Number of Shares \| shares	2,649,713
Exercised, Number of Shares \| shares	(283,275)
Cancelled, Number of Shares \| shares	(210,835)
Options and Warrants Outstanding, Number of Shares Ending Balance \| shares	7,461,779	5,306,176
Shares, Vested \| shares	1,696,242
Weighted Average Exercise Price Per Share, Outstanding Beginning Balance \| $ / shares	$ 4.62
Weighted Average Exercise Price Per Share, Granted \| $ / shares	7.67
Weighted Average Exercise Price Per Share, Exercised \| $ / shares	4.09
Weighted Average Exercise Price Per Share, Cancelled \| $ / shares	4.91
Weighted Average Exercise Price Per Share, Outstanding Ending Balance \| $ / shares	5.71	$ 4.62
Weighted Average Exercise Price Per Share, Vested \| $ / shares	$ 4.42
Weighted Average Remaining Contractual Life, Outstanding	8 years 8 months 15 days	8 years 11 months 26 days
Weighted Average Remaining Contractual Life, Vested	8 years 21 days
Aggregate Intrinsic Value, Outstanding Value \| $	$ 3,214
Aggregate Intrinsic Value, Outstanding Value \| $	275,178	$ 3,214
Aggregate Intrinsic Value, Vested Value \| $	$ 64,744

Share-Based Payments - Schedule of Stock-Based Compensation Expense Included In The Company's Consolidated Statements of Operations And Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 11,929	$ 1,248	$ 17,416	$ 3,150
Research and development expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	5,367	734	8,205	1,935
General and administrative expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 6,562	$ 514	$ 9,211	$ 1,215

Net Loss Per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Net loss	$ (36,078)	$ (26,724)	$ (24,886)	$ (19,673)	$ (17,537)	$ (14,182)	$ (87,688)	$ (51,392)
Deemed dividend resulting from extinguishment upon modification of series C preferred stock	(177,789)						(177,789)
Net loss attributable to common shareholders	$ (213,867)			$ (19,673)			$ (265,477)	$ (51,392)
Net loss per share attributable to common shareholders, basic and diluted	$ (3.00)			$ (5.53)			$ (9.92)	$ (15.46)
Weighted average shares of common stock, basic and diluted	71,248,846			3,556,303			26,766,687	3,323,456

- Definition

Amount after tax of income (loss) from continuing operations attributable to the parent.

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- Definition

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

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+ Details

Net Loss Per Share - Additional Information (Detail) - $ / shares		9 Months Ended
	Jul. 08, 2020	Sep. 30, 2020
Series C Preferred Stock [Member]
Preferred stock convertible conversion price	$ 3.027603	$ 3.21

Net Loss Per Share - Summary of Antidilutive Securities Excluded From Computation of Earnings Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive effect	7,635,597	65,767,677	7,635,597	65,767,677
Convertible preferred stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive effect		59,883,877		59,883,877
Options to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive effect	7,461,779	5,007,344	7,461,779	5,007,344
Unvested restricted stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive effect	173,818	876,456	173,818	876,456

Commitments and Contingencies - Additional Information (Detail) $ in Thousands		3 Months Ended		9 Months Ended
	Aug. 16, 2020 USD ($)	Sep. 30, 2020 USD ($) ft² Targets	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) ft² Targets	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Research and development expense		$ 24,376	$ 18,256	$ 67,739	$ 47,899
Accrued expenses		9,680		9,680		$ 3,746
Lease Agreement [Member]
Commitments and Contingencies Disclosure [Line Items]
Other Commitment		$ 1,300		$ 1,300
Area of Land \| ft²		1,824		1,824
DE Shaw Research [Member]
Commitments and Contingencies Disclosure [Line Items]
Accrued expenses		$ 2,941		$ 2,941		372
DE Shaw Research [Member] \| License Agreement Terms [Member]
Commitments and Contingencies Disclosure [Line Items]
Research and development arrangement, term of contract				3 years
Research and development arrangement, annual fee	$ 7,900	1,000		$ 1,000
Research and development arrangement, expiration date	Aug. 16, 2025
Milestone payment Due		0		0		0
Research and development expense		1,845	250	$ 3,069	750
DE Shaw Research [Member] \| License Agreement Terms [Member] \| Maximum [Member]
Commitments and Contingencies Disclosure [Line Items]
Agreement renewal period				1 year
Potential development milestone payments				$ 7,300
Other Third Parties [Member]
Commitments and Contingencies Disclosure [Line Items]
Research and development expense		235	$ 245	1,665	$ 871
Other Third Parties [Member] \| License Agreement Terms [Member]
Commitments and Contingencies Disclosure [Line Items]
Milestone payment Due		$ 0		0		$ 0
Other Third Parties [Member] \| License Agreement Terms [Member] \| Maximum [Member]
Commitments and Contingencies Disclosure [Line Items]
Potential development milestone payments				$ 7,000
Number of milestone targets \| Targets		4		4
Other Third Parties [Member] \| License Agreement Terms [Member] \| Minimum [Member]
Commitments and Contingencies Disclosure [Line Items]
Potential development milestone payments				$ 4,000

Related Party Transactions - Additional Information (Detail) - Third Rock Venture [Member] - Consulting And Management Services [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Related Party Expense	$ 0	$ 121	$ 0	$ 171
Due To Related Parties	$ 0		$ 0		$ 80