Erasca (ERAS) 10-Q 10 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 04, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Registrant Name	ERASCA, INC.
Entity Central Index Key	0001761918
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity File Number	001-40602
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-1217027
Entity Address, Address Line One	10835 Road to the Cure
Entity Address, Address Line Two	Suite 140
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	465-6511
Entity Current Reporting Status	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Interactive Data Current	No
Entity Common Stock, Shares Outstanding		121,250,375
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	ERAS
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 445,811,000	$ 65,376,000
Short-term investments	40,834,000	53,325,000
Prepaid expenses and other current assets	5,668,000	1,289,000
Total current assets	492,313,000	119,990,000
Property and equipment, net	8,520,000	1,847,000
Operating lease assets	19,042,000	2,225,000
Restricted cash	408,000	312,000
Other assets	1,665,000	451,000
Total assets	521,948,000	124,825,000
Current liabilities:
Accounts payable	1,324,000	878,000
Accrued expenses and other current liabilities	17,400,000	11,925,000
Operating lease liabilities	864,000	877,000
Total current liabilities	19,588,000	13,680,000
Operating lease liabilities, net of current portion	19,369,000	2,109,000
Preferred stock purchase right liability		1,615,000
Total liabilities	38,957,000	17,404,000
Commitments and contingencies (Note 12)
Stockholders' equity (deficit):
Preferred stock, $0.0001 par value; 80,000,000 shares and no shares authorized as of September 30, 2021 and December 31, 2020, respectively; no shares issued and outstanding as of September 30, 2021 and December 31, 2020
Common stock, $0.0001 par value; 800,000,000 and 147,027,681 shares authorized as of September 30, 2021 and December 31, 2020, respectively; 121,250,375 and 25,189,673 shares issued at September 30, 2021 and December 31, 2020, respectively; 118,645,593 and 21,923,173 shares outstanding at September 30, 2021 and December 31, 2020, respectively	12,000	3,000
Additional paid-in capital	690,681,000	1,413,000
Accumulated other comprehensive income		2,000
Accumulated deficit	(207,702,000)	(115,402,000)
Total stockholders' equity (deficit)	482,991,000	(113,984,000)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 521,948,000	124,825,000
Convertible Preferred Stock
Current liabilities:
Convertible preferred stock (Series A, B-1 and B-2), $0.0001 par value; no shares and 97,622,409 shares authorized as of September 30, 2021 and December 31, 2020, respectively; no shares and 69,584,682 shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively; aggregate liquidation preference of $0 and $230,924 as of September 30, 2021 and December 31, 2020, respectively		$ 221,405,000

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	80,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	800,000,000	147,027,681
Common stock, shares issued	121,250,375	25,189,673
Common stock, shares outstanding	118,645,593	21,923,173
Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Temporary equity, shares authorized	0	97,622,409
Temporary equity, shares issued	0	69,584,682
Temporary equity, shares outstanding	0	69,584,682
Temporary equity, liquidation preference	$ 0	$ 230,924

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating expenses:
Research and development	$ 19,951	$ 9,068	$ 49,794	$ 19,485
In-process research and development	1,680	75	10,848	17,745
General and administrative	6,916	2,020	15,696	5,052
Contribution of common stock to Erasca Foundation	17,497		17,497
Total operating expenses	46,044	11,163	93,835	42,282
Loss from operations	(46,044)	(11,163)	(93,835)	(42,282)
Other income (expense)
Interest income	49	38	110	293
Other expense	(74)	(38)	(190)	(79)
Change in fair value of preferred stock purchase right liability		555	1,615	2,311
Total other income (expense), net	(25)	555	1,535	2,525
Net loss	$ (46,069)	$ (10,608)	$ (92,300)	$ (39,757)
Net loss per share, basic and diluted	$ (0.46)	$ (0.50)	$ (1.90)	$ (1.91)
Weighted-average shares of common stock used in computing net loss per share, basic and diluted	99,127,286	21,084,657	48,584,029	20,851,262
Other comprehensive income (loss):
Unrealized gain (loss) on investments, net	$ 1	$ 3	$ (2)	$ (11)
Comprehensive loss	$ (46,068)	$ (10,605)	$ (92,302)	$ (39,768)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	IPO	Erasca Foundation	Convertible Preferred Stock	Common Stock	Common StockIPO	Common StockErasca Foundation	Additional Paid-in Capital	Additional Paid-in CapitalIPO	Additional Paid-in CapitalErasca Foundation	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Convertible preferred stock, beginning balance, shares at Dec. 31, 2019				38,103,681
Convertible preferred stock, beginning balance, value at Dec. 31, 2019				$ 63,403
Beginning balance, shares at Dec. 31, 2019					22,629,158
Beginning balance at Dec. 31, 2019	$ (13,604)				$ 3			$ 124			$ 11	$ (13,742)
Exercise of stock options, shares					729,166
Stock-based compensation expense	105							105
Net loss	(23,658)											(23,658)
Unrealized gain (loss) on investments, net	(22)										(22)
Convertible preferred stock, ending balance, shares at Mar. 31, 2020				38,103,681
Convertible preferred stock,ending balance, value at Mar. 31, 2020				$ 63,403
Ending balance, shares at Mar. 31, 2020					23,358,324
Ending balance at Mar. 31, 2020	(37,179)				$ 3			229			(11)	(37,400)
Convertible preferred stock, beginning balance, shares at Dec. 31, 2019				38,103,681
Convertible preferred stock, beginning balance, value at Dec. 31, 2019				$ 63,403
Beginning balance, shares at Dec. 31, 2019					22,629,158
Beginning balance at Dec. 31, 2019	(13,604)				$ 3			124			11	(13,742)
Net loss	(39,757)
Convertible preferred stock, ending balance, shares at Sep. 30, 2020				65,584,682
Convertible preferred stock,ending balance, value at Sep. 30, 2020				$ 191,404
Ending balance, shares at Sep. 30, 2020					25,552,592
Ending balance at Sep. 30, 2020	(52,823)				$ 3			673				(53,499)
Convertible preferred stock, beginning balance, shares at Mar. 31, 2020				38,103,681
Convertible preferred stock, beginning balance, value at Mar. 31, 2020				$ 63,403
Beginning balance, shares at Mar. 31, 2020					23,358,324
Beginning balance at Mar. 31, 2020	(37,179)				$ 3			229			(11)	(37,400)
Issuance of Series B-1 and B-2 convertible preferred stock for cash, shares				25,081,001
Issuance of Series B-1 and B-2 convertible preferred stock for cash				$ 117,647
Stock-based compensation expense	109							109
Net loss	(5,491)											(5,491)
Unrealized gain (loss) on investments, net	8										8
Convertible preferred stock, ending balance, shares at Jun. 30, 2020				63,184,682
Convertible preferred stock,ending balance, value at Jun. 30, 2020				$ 181,050
Ending balance, shares at Jun. 30, 2020					23,358,324
Ending balance at Jun. 30, 2020	(42,553)				$ 3			338			(3)	(42,891)
Issuance of Series B-1 and B-2 convertible preferred stock for cash, shares				2,400,000
Issuance of Series B-1 and B-2 convertible preferred stock for cash				$ 10,354
Exercise of stock options, shares					2,194,268
Exercise of stock options	114							114
Vesting of early exercised stock options	45							45
Stock-based compensation expense	176							176
Net loss	(10,608)											(10,608)
Unrealized gain (loss) on investments, net	3										3
Convertible preferred stock, ending balance, shares at Sep. 30, 2020				65,584,682
Convertible preferred stock,ending balance, value at Sep. 30, 2020				$ 191,404
Ending balance, shares at Sep. 30, 2020					25,552,592
Ending balance at Sep. 30, 2020	$ (52,823)				$ 3			673				(53,499)
Convertible preferred stock, beginning balance, shares at Dec. 31, 2020				69,584,682
Convertible preferred stock, beginning balance, value at Dec. 31, 2020				$ 221,405
Beginning balance, shares at Dec. 31, 2020	25,189,673				25,189,673
Beginning balance at Dec. 31, 2020	$ (113,984)				$ 3			1,413			2	(115,402)
Issuance of Series B-1 and B-2 convertible preferred stock for cash, shares				15,931,772
Issuance of Series B-1 and B-2 convertible preferred stock for cash				$ 119,393
Issuance of common stock in connection with asset acquisition, shares					500,000
Issuance of common stock in connection with asset acquisition	1,680							1,680
Exercise of stock options, shares					439,610
Exercise of stock options	94							94
Vesting of early exercised stock options	174							174
Stock-based compensation expense	795							795
Net loss	(18,017)											(18,017)
Unrealized gain (loss) on investments, net	(1)										(1)
Convertible preferred stock, ending balance, shares at Mar. 31, 2021				85,516,454
Convertible preferred stock,ending balance, value at Mar. 31, 2021				$ 340,798
Ending balance, shares at Mar. 31, 2021					26,129,283
Ending balance at Mar. 31, 2021	$ (129,259)				$ 3			4,156			1	(133,419)
Convertible preferred stock, beginning balance, shares at Dec. 31, 2020				69,584,682
Convertible preferred stock, beginning balance, value at Dec. 31, 2020				$ 221,405
Beginning balance, shares at Dec. 31, 2020	25,189,673				25,189,673
Beginning balance at Dec. 31, 2020	$ (113,984)				$ 3			1,413			2	(115,402)
Net loss	$ (92,300)
Convertible preferred stock, ending balance, shares at Sep. 30, 2021				0
Ending balance, shares at Sep. 30, 2021	121,250,375				121,250,375
Ending balance at Sep. 30, 2021	$ 482,991				$ 12			690,681				(207,702)
Convertible preferred stock, beginning balance, shares at Mar. 31, 2021				85,516,454
Convertible preferred stock, beginning balance, value at Mar. 31, 2021				$ 340,798
Beginning balance, shares at Mar. 31, 2021					26,129,283
Beginning balance at Mar. 31, 2021	(129,259)				$ 3			4,156			1	(133,419)
Issuance of common stock in connection with license agreement, shares					944,945
Issuance of common stock in connection with license agreement	5,488							5,488
Exercise of stock options, shares					225,895
Exercise of stock options	180							180
Vesting of early exercised stock options	174							174
Stock-based compensation expense	1,636							1,636
Net loss	(28,214)											(28,214)
Unrealized gain (loss) on investments, net	(2)										(2)
Convertible preferred stock, ending balance, shares at Jun. 30, 2021				85,516,454
Convertible preferred stock,ending balance, value at Jun. 30, 2021				$ 340,798
Ending balance, shares at Jun. 30, 2021					27,300,123
Ending balance at Jun. 30, 2021	(149,997)				$ 3			11,634			(1)	(161,633)
Temporary equity stock issued during period shares conversion of convertible securities, shares				(85,516,454)
Temporary equity stock issued during period value conversion of convertible securities				$ (340,798)
Conversion of convertible preferred stock into common stock upon initial public offering, shares					71,263,685
Conversion of convertible preferred stock into common stock upon initial public offering	340,798				$ 7			340,791
Issuance of common stock, net of discounts and issuance costs, shares						21,562,500	1,093,557
Issuance of common stock, net of discounts and issuance costs		$ 316,999	$ 17,497			$ 2			$ 316,997	$ 17,497
Disgorgement of stockholder's short-swing profits	553							553
Exercise of stock options, shares					30,510
Exercise of stock options	21							21
Vesting of early exercised stock options	171							171
Stock-based compensation expense	3,017							3,017
Net loss	(46,069)											(46,069)
Unrealized gain (loss) on investments, net	$ 1										$ 1
Convertible preferred stock, ending balance, shares at Sep. 30, 2021				0
Ending balance, shares at Sep. 30, 2021	121,250,375				121,250,375
Ending balance at Sep. 30, 2021	$ 482,991				$ 12			$ 690,681				$ (207,702)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020
Convertible Preferred Stock
Stock issuance costs		$ 95	$ 27	$ 403
Preferred stock purchase right liability			$ 1,618	$ 7,355
Common Stock
Discounts and offering costs	$ 28,001

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net loss			$ (92,300,000)	$ (39,757,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	$ 191,000	$ 139,000	509,000	394,000
Stock-based compensation expense			5,448,000	390,000
In-process research and development expenses	1,680,000	75,000	10,848,000	17,745,000
Issuance of common stock to Erasca Foundation			17,497,000
Amortization (accretion) on investments, net			75,000	(36,000)
Change in fair value of preferred stock purchase right liability		(555,000)	(1,615,000)	(2,311,000)
Changes in operating assets and liabilities:
Prepaid expenses and other current and long-term assets			(5,592,000)	(415,000)
Accounts payable			409,000	1,012,000
Accrued expenses and other current liabilities			7,173,000	3,446,000
Operating lease assets and liabilities, net			430,000	(59,000)
Net cash used in operating activities			(57,118,000)	(19,591,000)
Cash flows from investing activities:
Purchases of investments			(41,696,000)	(97,392,000)
Maturities of investments			54,110,000	28,292,000
In-process research and development			(7,680,000)	(17,745,000)
Purchases of property and equipment			(5,375,000)	(922,000)
Net cash used in investing activities			(641,000)	(87,767,000)
Cash flows from financing activities:
Proceeds from the issuance of common stock in initial public offering, net of discounts and issuance costs			316,999,000
Proceeds from the issuance of convertible preferred stock, net of issuance costs			119,393,000	136,974,000
Proceeds from the exercise of stock options, net of repurchases			1,345,000	3,130,000
Proceeds from the disgorgement of stockholder's short-swing profits			553,000
Net cash provided by financing activities			438,290,000	140,104,000
Net increase in cash, cash equivalents and restricted cash			380,531,000	32,746,000
Cash, cash equivalents and restricted cash at beginning of the period			65,688,000	29,583,000	$ 29,583,000
Cash, cash equivalents and restricted cash at end of the period	$ 446,219,000	$ 62,329,000	446,219,000	62,329,000	$ 65,688,000
Supplemental disclosure of noncash investing and financing activity:
Issuance of common stock to Erasca Foundation			17,497,000
Issuance of common stock in connection with asset acquisition			1,680,000
Issuance of common stock in connection with license agreement			5,488,000
Amounts accrued for purchases of property and equipment			1,882,000
Conversion of preferred stock to common stock upon initial public offering			340,798,000
Vesting of early exercised options			519,000	45,000
Preferred stock purchase right liability				8,973,000
Supplemental Disclosure of Noncash Operating Activities [Abstract]
Operating lease assets obtained in exchange for lease obligation			17,498,000	$ 28,000
Tenant improvement allowance included in operating lease liabilities			$ 16,774,000

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation	Note 1. Organization and basis of presentation Organization and nature of operations Erasca, Inc. (Erasca or the Company) is a clinical-stage precision oncology company singularly focused on discovering, developing, and commercializing therapies for RAS/MAPK pathway-driven cancers. The Company has assembled a wholly-owned or controlled RAS/MAPK pathway-focused pipeline comprising 11 modality-agnostic programs aligned with its three therapeutic strategies of: (i) targeting key upstream and downstream signaling nodes in the RAS/MAPK pathway; (ii) targeting RAS directly; and (iii) targeting escape routes that emerge in response to treatment. The Company was incorporated under the laws of the State of Delaware on July 2, 2018, as Erasca, Inc., and is headquartered in San Diego, California. In September 2020, the Company established a wholly-owned Australian subsidiary, Erasca Australia Pty Ltd (Erasca Australia), in order to conduct clinical activities in Australia for its development candidates. In November 2020, the Company entered into an agreement and plan of merger with Asana BioSciences, LLC (Asana) and ASN Product Development, Inc. (ASN) (the Asana Merger Agreement), pursuant to which ASN became the Company's wholly-owned subsidiary. In March 2021, the Company established a wholly-owned subsidiary, Erasca Ventures, LLC (Erasca Ventures), to potentially make equity investments in early-stage biotechnology companies that are aligned with the Company’s mission and strategy. Since inception, the Company has devoted substantially all of its efforts and resources to organizing and staffing the Company, business planning, raising capital, identifying, acquiring and in-licensing the Company’s product candidates, establishing its intellectual property portfolio, conducting research, preclinical studies, and clinical trials, establishing arrangements with third parties for the manufacture of its product candidates and related raw materials, and providing general and administrative support for these operations. As of September 30, 2021, the Company had $ 486.6 million in cash, cash equivalents, and short-term investments. As of September 30, 2021, the Company had an accumulated deficit of $ 207.7 million. The Company has incurred significant operating losses and negative cash flows from operations. From its inception through September 30, 2021, the Company’s financial support has primarily been provided from the sale of its convertible preferred stock and the sale of its common stock in its initial public offering (IPO). As the Company continues its expansion, it expects to use its cash, cash equivalents, and short-term investments to fund research and development, working capital, and other general corporate purposes. The Company does not expect to generate any revenues from product sales unless and until the Company successfully completes development and obtains regulatory approval for any of its product candidates, which will not be for at least the next several years, if ever. Accordingly, until such time as the Company can generate significant revenue from sales of its product candidates, if ever, the Company expects to finance its cash needs through equity offerings, debt financings, or other capital sources, including potential collaborations, licenses or other similar arrangements. However, the Company may not be able to secure additional financing or enter into such other arrangements in a timely manner or on favorable terms, if at all. The Company’s failure to raise capital or enter into such other arrangements when needed would have a negative impact on the Company’s financial condition and could force the Company to delay, limit, reduce or terminate its research and development programs or other operations, or grant rights to develop and market product candidates that the Company would otherwise prefer to develop and market itself. The Company believes its cash, cash equivalents, and short-term investments as of September 30, 2021 will be sufficient for the Company to fund operations for at least one year from the issuance date of these condensed consolidated financial statements. Initial public offering On July 20, 2021, the Company completed its IPO in which the Company issued and sold 21,562,500 shares of its common stock, including the exercise in full by the underwriters of their option to purchase 2,812,500 shares of common stock, at a price to the public of $ 16.00 per share. Proceeds from the IPO, net of underwriting discounts and commissions of $ 24.2 million and offering costs of $ 3.8 million, were $ 317.0 million. In connection with the completion of the IPO, all outstanding shares of convertible preferred stock were converted into 71,263,685 shares of common stock. Reverse stock split On July 9, 2021, the Company effected a one-for- 1.2 reverse stock split of its issued and outstanding shares of common stock (the Reverse Stock Split). The par value and the number of authorized shares of the convertible preferred stock and common stock were not adjusted as a result of the Reverse Stock Split. All issued and outstanding common stock and the conversion prices and ratio of the convertible preferred stock have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented. Basis of presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with US generally accepted accounting principles (US GAAP). Any reference in these notes to applicable guidance is meant to refer to US GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Updates (ASU) promulgated by the Financial Accounting Standards Board (FASB). Principles of consolidation and foreign currency transactions The Company’s consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Erasca Australia, ASN, and Erasca Ventures. Erasca Australia was registered under the laws of Australia on September 1, 2020, ASN was incorporated under the laws of the State of Delaware on November 23, 2020, and Erasca Ventures was formed under the laws of the State of Delaware on March 30, 2021. All intercompany balances and transactions have been eliminated. The functional currency of the Company and its wholly-owned subsidiaries is the US dollar. Assets and liabilities that are not denominated in the functional currency are remeasured into US dollars at foreign currency exchange rates in effect at the balance sheet date except for nonmonetary assets, which are remeasured at historical foreign currency exchange rates in effect at the date of transaction. Net realized and unrealized gains and losses from foreign currency transactions and remeasurement are reported in other income (expense), in the consolidated statements of operations and comprehensive loss and were not material for all periods presented.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2. Summary of significant accounting policies Use of estimates The preparation of the Company’s consolidated financial statements in conformity with US GAAP requires the Company to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the consolidated financial statements and accompanying notes. Accounting estimates and management judgments reflected in the consolidated financial statements include, but are not limited to, the accrual of research and development expenses, fair value of common stock, preferred stock and freestanding instruments, stock-based compensation expense, and the incremental borrowing rate for determining the operating lease asset and liability. Management evaluates its estimates on an ongoing basis. Although estimates are based on the Company’s historical experience, knowledge of current events, and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions. Unaudited interim financial information The accompanying condensed consolidated balance sheet as of September 30, 2021, the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020, the condensed consolidated statements of convertible preferred stock and stockholders’ deficit for the three and nine months ended September 30, 2021 and 2020 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. The unaudited condensed 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 statement of the Company’s condensed consolidated financial position as of September 30, 2021 and the condensed consolidated results of its operations and cash flows for the three and nine months ended September 30, 2021 and 2020. The condensed consolidated financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2021 and 2020 are unaudited. The condensed consolidated results for the three and nine months ended September 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period. Concentration of credit risk and off-balance sheet risk Financial instruments which potentially subject the Company to significant concentration of credit risk consist of cash and cash equivalents and investments. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts, and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. The Company’s investment policy includes guidelines for the quality of the related institutions and financial instruments and defines allowable investments that the Company may invest in, which the Company believes minimizes the exposure to concentration of credit risk. Cash, cash equivalents and restricted cash Cash and cash equivalents include cash in readily available checking and savings accounts, money market funds, commercial paper, and corporate debt securities. The Company considers all highly liquid investments with an original maturity of three months or less from the date of purchase to be cash equivalents. The Company had deposited cash of $ 408,000 and $ 312,000 as of September 30, 2021 and December 31, 2020, respectively, to secure a letter of credit in connection with the lease of the Company’s facilities (see Note 11). The Company has classified the restricted cash as a noncurrent asset on its condensed consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2021 2020 Cash and cash equivalents $ 445,811 $ 62,017 Restricted cash 408 312 Total cash, cash equivalents and restricted cash as shown on the condensed $ 446,219 $ 62,329 Investments The Company classifies all marketable securities as available-for-sale, as the sale of such securities may be required prior to maturity. Management determines the appropriate classification of its investments in debt securities at the time of purchase. Investments with original maturities beyond three months at the date of purchase and which mature at, or less than 12 months from, the balance sheet date are classified as short-term investments. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported as accumulated other comprehensive income (loss) until realized. The amortized cost of available-for-sale debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in interest income. The Company regularly reviews all its investments for other-than-temporary declines in fair value. The review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. When the Company determines that the decline in fair value of an investment is below its accounting basis and the decline is other-than-temporary, the Company reduces the carrying value of the security it holds and records a loss for the amount of such decline. Realized gains and losses and declines in value judged to be other than temporary, if any, on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income. Fair value measurements Certain assets and liabilities are carried at fair value under US GAAP. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Financial assets and liabilities carried at fair value are classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: Level 1—Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2—Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. Level 3—Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Property and equipment, net Property and equipment are stated at cost less accumulated depreciation. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the respective assets, generally three to seven years . Leasehold improvements are amortized over the shorter of the estimated useful lives of the assets or the remaining lease term. Impairment of long-lived assets The Company continually evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book values of the assets exceed their fair value. The Company did no t recognize any impairment losses for the three and nine months ended September 30, 2021 and 2020 . Leases The Company leases real estate facilities and equipment under non-cancelable and cancelable operating leases with various expiration dates through fiscal year 2032. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present, the existence of an identified asset(s), if any, and the Company’s control over the use of the identified asset(s), if applicable. Operating leases are included in operating lease assets and in operating lease liabilities in the accompanying condensed consolidated balance sheets. Operating lease assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term discounted based on the more readily determinable of (i) the rate implicit in the lease or (ii) the Company’s incremental borrowing rate (which is the estimated rate the Company would be required to pay for a collateralized borrowing equal to the total lease payments over the term of the lease). Because the Company’s operating leases generally do not provide an implicit rate, the Company estimates its incremental borrowing rate based on the information available at lease commencement date for borrowings with a similar term. The Company’s operating lease assets are measured based on the corresponding operating lease liability adjusted for (i) payments made to the lessor at or before the commencement date, (ii) initial direct costs incurred and (iii) tenant incentives under the lease. The Company does not assume renewals or early terminations unless it is reasonably certain to exercise these options at commencement. The Company elected the practical expedient which allows the Company to not allocate consideration between lease and non-lease components. Variable lease payments are recognized in the period in which the obligations for those payments are incurred. In addition, the Company elected the practical expedient such that it does not recognize lease assets or lease liabilities for leases with a term of 12 months or less of all asset classes. Operating lease expense is recognized on a straight-line basis over the lease term. Certain of the Company's real estate leases include tenant improvement allowances, which are recognized as lease incentives and amortized on a straight-line basis over the lease term as an offset to rent expense. Research and development expense Research and development expenses consist of external and internal costs associated with the Company’s research and development activities, including its discovery and research efforts and the preclinical and clinical development of its product candidates. Research and development costs are expensed as incurred. The Company’s research and development expenses include external costs, consisting of expenses incurred under arrangements with third parties, such as contract research organizations (CROs), contract manufacturing organizations (CMOs), consultants and its scientific advisors; and internal costs, consisting of employee-related expenses, including salaries, benefits, and stock-based compensation for those individuals involved in research and development efforts, the costs of laboratory supplies and acquiring, developing and manufacturing preclinical study materials, and facilities and depreciation, which include direct and allocated expenses for rent of facilities and depreciation of equipment. The Company records accruals for estimated research and development costs, comprising payments for work performed by third party contractors, laboratories, and others. Some of these contractors bill monthly based on actual services performed, while others bill periodically based upon achieving certain contractual milestones. For the latter, the Company accrues the expenses as goods or services are used or rendered. Non-refundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized as prepaid expenses until the related goods are delivered or services are performed. In-process research and development expense The Company has acquired rights as part of asset acquisitions or in-licenses to develop and commercialize product candidates. Upfront payments that relate to the acquisition of a new drug compound, as well as pre-commercial milestone payments, are immediately expensed as in-process research and development (IPR&D) in the period in which they are incurred, provided that the new drug compound did not also include processes or activities that would constitute a “business” as defined under US GAAP, the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no established alternative future use. The Company accounts for contingent consideration payable upon achievement of certain regulatory, development or sales milestones in such asset acquisitions when the underlying contingency is resolved. Milestone payments made to third parties subsequent to regulatory approval will be capitalized as intangible assets and amortized over the estimated remaining useful life of the related product. Patent costs The Company expenses all costs as incurred in connection with patent applications (including direct application fees, and the legal and consulting expenses related to making such applications) and such costs are included in general and administrative expenses in the consolidated statements of operations and comprehensive loss. Deferred offering costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ deficit as a reduction of proceeds generated as a result of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. There were no deferred offering costs as of September 30, 2021 and December 31, 2020 . Common stock valuation Due to the absence of an active market for the Company’s common stock prior to the IPO, the Company utilized methodologies, approaches and assumptions consistent with the American Institute of Certified Public Accountants’ Audit and Accounting Practice Guide: Valuation of Privately-Held Company Equity Securities Issued as Compensation to estimate the fair value of its common stock. In determining the exercise prices for options granted, the Company has considered the fair value of the common stock as of the grant date. Prior to the IPO, the fair value of the common stock was determined based upon a variety of factors, including valuations of the Company’s common stock performed with the assistance of independent third-party valuation specialists; the Company’s stage of development and business strategy, including the status of research and development efforts of its product candidates, and the material risks related to its business and industry; the Company’s business conditions and projections; the Company’s results of operations and financial position, including its levels of available capital resources; the valuation of publicly traded companies in the life sciences and biotechnology sectors, as well as recently completed mergers and acquisitions of peer companies; the lack of marketability of the Company’s common stock as a private company; the prices of the Company’s convertible preferred stock sold to investors in arm’s length transactions and the rights, preferences and privileges of its convertible preferred stock relative to those of its common stock; the likelihood of achieving a liquidity event for the holders of the Company’s common stock, such as an initial public offering or a sale of the Company given prevailing market conditions; trends and developments in its industry; the hiring of key personnel and the experience of management; and external market conditions affecting the life sciences and biotechnology industry sectors. Significant changes to the key assumptions underlying the factors used could result in different fair values of common stock at each valuation date. After the completion of the IPO, the fair value of each share of common stock is based on the closing price of the Company’s common stock as reported by the Nasdaq Global Select Market (Nasdaq). Stock-based compensation The Company measures employee and nonemployee stock-based awards based on the fair value on the date of grant and records compensation expense on a straight-line basis over the requisite service period of the award. The Company records the expense for stock-based awards subject to performance-based milestone vesting over the implied service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions at each reporting date. All stock-based compensation costs are recorded in the consolidated statements of operations and comprehensive loss based upon the underlying employees or nonemployee’s roles within the Company. Forfeitures are accounted for as they occur. The fair value of stock option grants and shares purchasable under the Company's 2021 Employee Stock Purchase Plan (ESPP) is estimated on the date of grant using the Black-Scholes options-pricing model, which requires inputs based on certain subjective assumptions, including the: • Fair value of common stock. As there was no active market for the Company’s common stock prior to the IPO, the Company estimated the fair value of common stock on the date of grant based on the then current facts and circumstances. • Risk-free interest rate. The risk-free interest rate is based on the US Treasury zero-coupon issues in effect at the time of grant for periods corresponding with the expected term of the stock-based awards. • Expected volatility. Given that the Company’s common stock was privately held prior to the IPO, there was no active trading market for its common stock. The Company derived the expected volatility from the average historical volatilities over a period approximately equal to the expected term of comparable publicly traded companies within its peer group that were deemed to be representative of future stock price trends. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. • Expected term. The expected term represents the period that the stock-based awards are expected to be outstanding. The expected term of stock options issued is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term) as the Company has concluded that its stock option exercise history does not provide a reasonable basis upon which to estimate expected term. • Expected dividend yield. The Company has never paid dividends on its common stock and does not anticipate paying any dividends in the foreseeable future. Therefore, the Company used an expected dividend yield of zero . The fair value of each restricted common stock award is estimated on the date of grant based on the fair value of the Company’s common stock on that same date. Classification and accretion of convertible preferred stock The Company’s convertible preferred stock is classified outside of stockholders’ deficit on the consolidated balance sheets because the holders of such shares have liquidation rights in the event of a deemed liquidation that, in certain situations, are not solely within the control of the Company and would require the redemption of the then-outstanding convertible preferred stock. The convertible preferred stock is not redeemable, except in the event of a deemed liquidation. Because the occurrence of a deemed liquidation event is not currently probable, the carrying values of the convertible preferred stock are not being accreted to their redemption values. Subsequent adjustments to the carrying values of the convertible preferred stock would be made only when a deemed liquidation event becomes probable. Preferred stock purchase right liabilities The Company has entered into convertible preferred stock financings where, in addition to the initial closing, investors agree to buy, and the Company agrees to sell, additional shares of that convertible preferred stock at a fixed price in the event that certain conditions are met or agreed upon milestones are achieved. The Company evaluates this purchase right and assesses whether it meets the definition of a freestanding instrument and, if so, determines the fair value of the purchase right liability and records it on the balance sheet with the remainder of the proceeds raised allocated to convertible preferred stock. The preferred stock purchase right liability is revalued at each reporting period with changes in the fair value of the liability recorded as change in fair value of preferred stock purchase right liability in the consolidated statements of operations and comprehensive loss. The preferred stock purchase right liability is revalued at settlement and the resultant fair value, if any, is then reclassified to convertible preferred stock at that time. Income taxes The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the Company’s consolidated financial statements or tax returns. Under this method, deferred tax assets and liabilities are determined based on differences between the financial statement carrying amounts and the tax bases of the assets and liabilities using the enacted tax rates in effect in the years in which the differences are expected to reverse. A valuation allowance against deferred tax assets is recorded if, based on the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. As of September 30, 2021 , the Company’s tax years since inception are subject to examination by taxing authorities due to the Company’s unutilized net operating losses and tax credits. Comprehensive income (loss) The Company reports all components of comprehensive income (loss), including net loss, in the consolidated financial statements in the period in which they are recognized. Comprehensive income (loss) is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on investments. Other comprehensive income includes unrealized gains and losses on investments, which was the only difference between net loss and comprehensive loss for the applicable periods. Net loss per share The Company’s net loss is equivalent to net loss attributable to common stockholders for all periods presented. Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, the convertible preferred stock, options to purchase common stock, shares purchasable under the ESPP and common stock subject to repurchase related to unvested restricted stock and options early exercised are considered to be potentially dilutive securities. Basic and diluted net loss per share is presented in conformity with the two-class method required for participating securities as the convertible preferred stock is considered a participating security because it participates in dividends with common stock. The Company also considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. The Company’s participating securities do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. As the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Segments The Company has determined that its chief executive officer is the chief operating decision maker (CODM). The Company operates and manages the business as one reporting and one operating segment, which is the business of discovering and developing precision medicines for the benefit of patients with cancer. The Company’s CODM reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. All of the Company’s assets are located in the United States. Recently adopted accounting pronouncements In August 2018, the FASB issued ASU 2018-13, Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement. The primary focus of the standard is to improve the effectiveness of the disclosure requirements for fair value measurements. The Company adopted this guidance on January 1, 2020 , with no material impact on its consolidated financial statements or related disclosures. In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). The new standard will align the requirements for capitalizing implementation costs for hosting arrangements (services) with costs for internal-use software (assets). As a result, certain implementation costs incurred in hosting arrangements will be deferred and amortized. The Company adopted ASU 2018-15 on January 1, 2021 , and the adoption had an immaterial impact on its consolidated financial statements and related disclosures. Recently issued accounting pronouncements not yet adopted 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 (JOBS Act) and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application 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. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13) and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The 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. The Company is currently evaluating the potential impact ASU 2016-13, and related updates, will have on its consolidated financial statements and related disclosures upon adoption. In August 2020, the FASB issued ASU 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) (ASU 2020-06), which simplifies the accounting for convertible instruments and contracts in an entity’s own equity. This guidance is effective for the Company in its annual reporting period beginning after December 15, 2023, including interim periods within that reporting period, with early adoption permitted only as of annual reporting periods beginning after December 15, 2020. The Company is currently assessing the impact this standard will have on its consolidated financial statements and related disclosures upon adoption.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair value measurements	Note 3. Fair value measurements The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis and their respective input levels based on the fair value hierarchy (in thousands): Fair value measurements as of September 30, 2021 using Quoted prices in Significant Significant active markets other unobservable September 30, for identical observable inputs 2021 assets (level 1) inputs (level 2) (level 3) Assets: Money market funds (1) $ 436,727 $ 436,727 $ — $ — US government securities (2) 10,031 — 10,031 — Corporate debt securities (2) 1,517 — 1,517 — Commercial paper (2) 27,776 — 27,776 — Supranational debt securities (2) 1,510 — 1,510 — Total fair value of assets $ 477,561 $ 436,727 $ 40,834 $ — (1) Included as cash and cash equivalents on the condensed consolidated balance sheets. (2) Included as short-term investments on the condensed consolidated balance sheets. As of September 30, 2021 , there were no financial liabilities measured at fair value on a recurring basis. Fair value measurements as of December 31, 2020 using Quoted prices in Significant Significant active markets other unobservable December 31, for identical observable inputs 2020 assets (level 1) inputs (level 2) (level 3) Assets: Money market funds (1) $ 57,238 $ 57,238 $ — $ — Commercial paper (1) 900 — 900 — US treasury securities (2) 38,492 38,492 — — Corporate debt securities (2) 3,793 — 3,793 — Commercial paper (2) 11,040 — 11,040 — Total fair value of assets $ 111,463 $ 95,730 $ 15,733 $ — Liabilities: Preferred stock purchase right liability 1,615 — — 1,615 Total fair value of liabilities $ 1,615 $ — $ — $ 1,615 (1) Included as cash and cash equivalents on the consolidated balance sheets. (2) Included as short-term investments on the consolidated balance sheets. The carrying amounts of the Company’s financial instruments, including cash, prepaid and other current assets, accounts payable, and accrued expenses and other current liabilities, approximate fair value due to their short maturities. None of the Company’s non-financial assets or liabilities are recorded at fair value on a non-recurring basis. No transfers between levels have occurred during the periods presented. There are uncertainties on the fair value measurement of the instrument classified under Level 3 due to the use of unobservable inputs and interrelationships between these unobservable inputs, which could result in higher or lower fair value measurements. Cash equivalents consist of money market funds and commercial paper, and short-term investments consist of US treasury and government securities, corporate debt securities, commercial paper and supranational debt securities. The Company obtains pricing information from its investment manager and generally determines the fair value of investment securities using standard observable inputs, including reported trades, broker/dealer quotes, and bid and/or offers. Preferred stock purchase right liability As of December 31, 2020, the quantitative elements associated with the Company’s Level 3 inputs impacting the fair value measurement of the preferred stock purchase right liability include the fair value per share of the underlying Series B-1 Preferred Stock, the expected term of the purchase right liability, risk-free interest rate, expected dividend yield and expected volatility of the price of the underlying preferred stock. The most significant assumption in the Black-Scholes option-pricing model impacting the fair value of the preferred stock purchase right liability was the fair value of the Company’s convertible preferred stock as of each measurement date. The Company determined the fair value per share of the underlying preferred stock by taking into consideration its most recent sales of its convertible preferred stock as well as additional factors that the Company deemed relevant. The Company lacks company-specific historical and implied volatility information of its stock. Therefore, it estimated its expected preferred stock volatility based on the historical volatility of publicly traded peer companies for a term equal to the expected term of the purchase right liability. The risk-free interest rate was determined by reference to the US Treasury yield curve for time periods approximately equal to the expected term of the purchase right liability. The Company estimated a 0% dividend yield based on the expected dividend yield and the fact that the Company never paid or declared dividends. The change in fair value of the purchase right liability was a gain of $ 555,000 and $ 2.3 million for the three and nine months ended September 30, 2020 , respectively, included in other income (expense) within the condensed consolidated statements of operations and comprehensive loss. Upon the issuance of the shares of the Company’s Series B-2 convertible preferred stock in January 2021, the purchase right liability was revalued with the gain of $ 1.6 million recorded in change in fair value of the purchase right liability for the nine months ended September 30, 2021 within the condensed consolidated statements of operations and comprehensive loss. Significant changes in the assumptions could have a material impact on the value of the preferred stock purchase right liability. The assumptions used in the Black-Scholes option pricing model to determine the fair value of the preferred stock purchase right liability at settlement date and December 31, 2020 were as follows: Settlement Date December 31, 2020 Fair value of underlying preferred stock $ 6.11 $ 6.11 Risk-free interest rate 0.07 % 0.08 % Expected volatility 74.4 % 71.8 % Expected term (in years) 0.00 0.08 Expected dividend yield — % — %

Investments

Investments	9 Months Ended
	Sep. 30, 2021
Investments Debt And Equity Securities [Abstract]
Investments	Note 4. Investments The following tables summarize the Company’s investments accounted for as available-for-sale securities (in thousands, except years): September 30, 2021 Maturity Amortized Unrealized Unrealized Estimated (in years) cost losses gains fair value US government securities 1 or less $ 10,031 $ — $ — 10,031 Corporate debt securities 1 or less 1,517 — — 1,517 Commercial paper 1 or less 27,776 — — 27,776 Supranational debt securities 1 or less 1,510 — — 1,510 Total $ 40,834 $ — $ — $ 40,834 December 31, 2020 Maturity Amortized Unrealized Unrealized Estimated (in years) cost losses gains fair value US treasury securities 1 or less $ 38,489 $ — $ 3 $ 38,492 Corporate debt securities 1 or less 3,794 ( 1 ) — 3,793 Commercial paper 1 or less 11,040 — — 11,040 Total $ 53,323 $ ( 1 ) $ 3 $ 53,325 As of September 30, 2021, there were two av ailable-for-sale securities with an estimated fair value of $ 3.0 million i n gross unrealized loss positions. None had been in such position for greater than 12 months. As of December 31, 2020, there were six available-for-sale securities with an estimated fair value of $ 15.8 million in gross unrealized loss positions. Based on the Company’s review of its investments, the Company believes that the unrealized losses were not other-than-temporary as of September 30, 2021 and December 31, 2020 .

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	Note 5. Property and equipment, net Property and equipment, net consisted of the following (in thousands): September 30, December 31, 2021 2020 Leasehold improvements $ 795 $ 795 Construction in progress 4,712 — Laboratory equipment 2,186 1,380 Furniture and fixtures 1,598 165 Office equipment 61 61 Software 87 70 Computer equipment 488 278 Property and equipment 9,927 2,749 Less accumulated depreciation and amortization ( 1,407 ) ( 902 ) Property and equipment, net $ 8,520 $ 1,847 Depreciation and amortization expense related to property and equipment was $ 191,000 and $ 509,000 for the three and nine months ended September 30, 2021 , respectively, and $ 139,000 and $ 394,000 for the three and nine months ended September 30, 2020 , respectively.

Accrued expenses and other curr

Accrued expenses and other current liabilities	9 Months Ended
	Sep. 30, 2021
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Note 6. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, December 31, 2021 2020 Accrued research and development expenses $ 6,647 $ 6,649 Accrued compensation 4,711 2,416 Unvested early exercised stock option liability 3,057 2,526 Accrued construction in progress 1,834 — Accrued legal 174 194 Other accruals 977 140 Total $ 17,400 $ 11,925

Asset Acquisitions

Asset Acquisitions	9 Months Ended
	Sep. 30, 2021
Asset Acquisitions [Abstract]
Asset Acquisitions	Note 7. Asset acquisitions The following purchased assets were accounted for as asset acquisitions as substantially all of the fair value of the assets acquired were concentrated in a group of similar assets, and the acquired assets did not have outputs or employees. Because the assets had not yet received regulatory approval, the fair value attributable to these assets was recorded as in-process research and development expenses in the Company’s consolidated statements of operations and comprehensive loss. Asana BioSciences, LLC In November 2020, the Company entered into the Asana Merger Agreement, pursuant to which ASN became its wholly-owned subsidiary. Asana and ASN had previously entered into a license agreement, which was amended and restated prior to the closing of the merger transaction (the Asana License Agreement, and collectively with the Asana Merger Agreement, the Asana Agreements), pursuant to which ASN acquired an exclusive, worldwide license to certain intellectual property rights relating to inhibitors of ERK1 and ERK2 owned or controlled by Asana to develop and commercialize ERAS-007 and certain other related compounds for all applications. The Company has the right to sublicense (through multiple tiers) the licensed rights under the Asana Agreements, subject to certain conditions. The foregoing license is subject to Asana’s non-exclusive right to practice the licensed rights to research and conduct preclinical pharmacology activities with a specified combination of compounds, subject to certain specified conditions. Pursuant to the Asana License Agreement, neither Asana nor ASN can directly or indirectly exploit certain classes of competing products, subject to specified exceptions. In addition, the Company is required to use commercially reasonable efforts to develop and obtain regulatory approval for ERAS-007 in the United States, at least one major market country in Europe, and either China or Japan. Under the Asana Merger Agreement, the Company made an upfront payment of $ 20.0 million and issued 4,000,000 shares of its Series B-2 convertible preferred stock to Asana at a value of $ 7.50 per share or a total fair value of $ 30.0 million. The Company is obligated to make future development and regulatory milestone cash payments for a licensed product in an amount of up to $ 90.0 million. Additionally, upon achieving a development milestone related to demonstration of successful proof-of-concept in a specified clinical trial, the Company will also be required to issue 3,888,889 shares of its common stock to Asana. The Company is not obligated to pay royalties on the net sales of licensed products. The Company recorded IPR&D expense of $ 50.0 million during the year ended December 31, 2020 in connection with the asset acquisition. No IPR&D expense was recorded during the three and nine months ended September 30, 2021 and 2020. As of September 30, 2021 and December 31, 2020 , no milestones had been accrued as the underlying contingencies had not yet been resolved. Upon the Company’s payment to Asana of all merger consideration, including upfront cash and equity payments, the equity payment related to the proof-of-concept development milestone, and all other development milestone payments, with the exception of a specific milestone that does not need to be achieved at such time and will remain subject to payment in the event that such milestone is achieved at a later time, all licensed rights will become fully paid-up, perpetual, and irrevocable. The Asana License Agreement may be terminated by either Asana or the Company in the event of an uncured material breach by the other party. Asana also has the right to terminate the Asana License Agreement if the Company fails to engage in material activities in support of clinical development and commercialization of ERAS-007 for a period of 12 consecutive months, excluding reasons outside of its reasonable control and subject to certain limitations. However, Asana’s right to terminate the Asana License Agreement for any reason ends once the Company has paid to Asana all merger consideration, or if Asana’s equity interest in the Company becomes publicly traded and exceeds a certain threshold value. The Company may terminate the Asana License Agreement at any time upon the provision of prior written notice to Asana. Emerge Life Sciences, Pte. Ltd. In March 2021, the Company entered into an asset purchase agreement (ELS Purchase Agreement) with Emerge Life Sciences, Pte. Ltd. (ELS) wherein it purchased all rights, title, and interest (including all patent and other intellectual property rights) to EGFR antibodies directed against the EGFR domain II (EGFR-D2) and domain III (EGFR-D3) as well as a bispecific antibody where one arm is directed against EGFR-D2 and the other is directed against EGFR-D3 (the Antibodies). Under the terms of the ELS Purchase Agreement, the Company made an upfront payment of $ 2.0 million and issued to ELS 500,000 shares of the Company’s common stock at a value of $ 3.36 per share or a total fair value of $ 1.7 million. Under the ELS Purchase Agreement, ELS is committed to performing certain studies on the applicable antibodies to assist in development activities, the costs of which shall be mutually agreed upon and for which the Company will be responsible. The Company recorded IPR&D expense of $ 0 and $ 3.7 million during the three and nine months ended September 30, 2021 in connection with the asset acquisition. Pursuant to the ELS Purchase Agreement, at any time between 12 months and 36 months after the effective date of the ELS Purchase Agreement, if the Company reasonably determines that none of the Antibodies should be taken into human clinical trials due to safety, efficacy or chemistry, manufacturing and controls (CMC) issues, then the Company has the option to select another antibody developed and solely owned by ELS that is not the subject of a license, collaboration, or option to a third party (the Option). If the Company elects to exercise the Option, then ELS will provide to the Company a list of all available antibodies that meet the aforementioned requirements, and the Company has the right to select one antibody from the list. Upon the Company’s selection of an antibody, ELS will assign it all rights, title and interest to such antibody (including patent and other intellectual property rights) subject to any pre-existing obligations or restrictions. In the event that the Company wishes to have ELS conduct any studies on such optioned antibody, then after mutual agreement as to the scope of the studies, the Company will be responsible for the cost for such studies.

License Agreements

License Agreements	9 Months Ended
	Sep. 30, 2021
License Agreements [Abstract]
License Agreements	Note 8. License agreements NiKang Therapeutics, Inc. In February 2020, the Company entered into a license agreement (the NiKang Agreement) with NiKang Therapeutics, Inc. (NiKang) under which the Company was granted an exclusive, worldwide license to certain intellectual property rights owned or controlled by NiKang related to certain SHP2 inhibitors to develop and commercialize ERAS-601 and certain other related compounds for all applications. The Company has the right to sublicense (through multiple tiers) its rights under the NiKang Agreement, subject to certain conditions, and is required to use commercially reasonable efforts to develop and commercialize licensed products. The parties are obligated to negotiate in good faith for a certain period of time to grant NiKang the exclusive commercial distribution rights in greater China once a licensed product reaches a certain development stage. Under the NiKang Agreement, the Company made an upfront payment of $ 5.0 million to NiKang and reimbursed NiKang $ 0.4 million for certain initial manufacturing costs. In addition, the Company paid $ 7.0 million in April 2020 related to the publication of a US patent application that covered the composition of matter of ERAS-601. The Company is also obligated to pay (i) development and regulatory milestone payments in an aggregate amount of up to $ 16.0 million for the first licensed product and $ 12.0 million for a second licensed product, and (ii) commercial milestone payments in an aggregate amount of up to $ 157.0 million for the first licensed product and $ 151.0 million for a second licensed product. The Company is also obligated to: (i) pay tiered royalties on net sales of all licensed products in the mid-single digit percentages, subject to certain reductions; and (ii) equally split all net sublicensing revenues earned under sublicense agreements that the Company enters into with any third party before commencement of the first Phase I clinical trial for a licensed product. As of September 30, 2021 and December 31, 2020 , the Company had accrued $ 0 and $ 4.0 million related to a development milestone, respectively. The Company recorded IPR&D expense of $ 0 during the three and nine months ended September 30, 2021 and $ 0 and $ 12.0 million during the three and nine months ended September 30, 2020, respectively, related to the upfront and milestone payments. The NiKang Agreement will expire upon the last to expire royalty term, which is determined on a licensed product-by-licensed product and country-by-country basis, and is the later of (i) ten years from the date of first commercial sale, (ii) the last to expire valid claim within the licensed patent rights covering such licensed product, or (iii) the expiration of all regulatory exclusivity for the licensed product in such country. Upon expiration of the NiKang Agreement, on a licensed product-by-licensed product and country-by-country basis, the Company will have a fully paid-up, non-exclusive license to conduct research and to develop and commercialize the licensed products. The NiKang Agreement may be terminated in its entirety by NiKang in the event of the Company’s uncured material breach, which includes its failure to use commercially reasonable efforts to satisfy certain specified clinical development diligence milestones. In addition, NiKang may terminate if the Company, directly or indirectly, commences a legal action challenging the validity or enforceability of any licensed patents. Further, if the Company acquires more than 50 % of the equity or assets of a company that owns a competing small molecule that is designed to prevent the same target as set forth in the NiKang Agreement from switching to an enzymatically active state, then the Company must either divest such competing product or terminate the NiKang Agreement. The Company may terminate the NiKang Agreement at any time upon the provision of prior written notice to NiKang. Upon termination of the NiKang Agreement for any reason, all rights and licenses granted to the Company, as well as any sublicenses that the Company granted thereunder, will terminate. In addition, upon any termination (but not expiration) of the NiKang Agreement and upon NiKang’s request, the parties are obligated to meet and negotiate in good faith the terms of a license from the Company to NiKang to allow NiKang’s continued development, manufacture, and commercialization of the licensed products. Katmai Pharmaceuticals, Inc. In March 2020, the Company entered into a license agreement (the Katmai Agreement) with Katmai Pharmaceuticals, Inc. (Katmai) under which the Company was granted an exclusive, worldwide, royalty-bearing license to certain patent rights and know-how controlled by Katmai related to the development of small molecule therapeutic and diagnostic products that modulate EGFR and enable the identification, diagnosis, selection, treatment, and/or monitoring of patients for neuro-oncological applications to develop, manufacture, use, and commercialize ERAS-801 and certain other related compounds in all fields of use. The Company has the right to sublicense (through multiple tiers) its rights under the Katmai Agreement, subject to certain limitations and conditions, and is required to use commercially reasonable efforts to develop, manufacture, and commercialize licensed products and to meet certain specified development and launch milestones by certain dates. The Company is obligated to use commercially reasonable efforts to develop the licensed products first for use within the neuro-oncology field before expanding its development efforts to include other indications in the oncology field. Following the first achievement of a clinical proof-of-concept for any indication, the Company has the right to submit a non-binding offer to Katmai for (i) the purchase of all licensed patent rights, know-how, and other assets owned by Katmai that are necessary or useful for the exploitation of the licensed products or (ii) for the purchase of Katmai. Pursuant to the Katmai Agreement, neither Katmai nor the Company can directly or indirectly exploit certain specified classes of competing products. The license granted under the Katmai Agreement is subject to The Regents of the University of California’s reserved right to (i) use the licensed patent rights and know-how for educational and non-commercial research purposes, and to publish results arising therefrom, and (ii) grant licenses to the licensed know-how to third parties without notice because the licensed know-how is non-exclusively licensed to Katmai by The Regents of the University of California. Further, the license granted under the Katmai Agreement is subject to the rights of the United States government under the Bayh-Dole Act, including (i) a non-exclusive, non-transferable, irrevocable, paid-up license to practice or have practiced the invention claimed by the licensed patent rights throughout the world and (ii) the obligation that any licensed products used or sold in the United States be manufactured substantially in the United States. Under the Katmai Agreement, the Company made an upfront payment of $ 5.7 million and Katmai agreed to purchase shares of the Company’s Series B-1 convertible preferred stock and Series B-2 convertible preferred stock having an aggregate value of $ 2.7 million. In April 2020, Katmai purchased 356,000 shares of the Company’s Series B-1 convertible preferred stock for $ 1.8 million, and in January 2021, Katmai purchased 118,666 shares of the Company’s Series B-2 convertible preferred stock for $ 0.9 million. The Company is obligated to make future development and regulatory milestone payments of up to $ 26.0 million and commercial milestone payments of up to $ 101.0 million. The Company is also obligated to pay tiered royalties on net sales of each licensed product, at rates ranging from the mid- to high-single digit percentages, subject to a minimum annual royalty payment in the low six figures and certain permitted deductions. No IPR&D expense was recorded for the three and nine months ended September 30, 2021 . The Company recorded IPR&D expense of $ 0 and $ 5.7 million in connection with the upfront payment during the three and nine months ended September 30, 2020, respectively. The Company’s royalty obligations and the Katmai Agreement will expire, on a licensed product-by-licensed product and country-by-country basis, on the earlier of (i) the ten-year anniversary of the expiration of all valid claims included in the licensed patents covering the composition of matter or method of use of such licensed product in such country or (ii) the twentieth anniversary of the first commercial sale of such licensed product in such country. Upon the expiration of the Katmai Agreement, the Company will have a fully paid-up and irrevocable license. The Katmai Agreement may be terminated in its entirety by either party (i) in the event of an uncured material breach by the other party or (ii) in the event the other party becomes subject to specified bankruptcy, insolvency, or similar circumstances. Provided that the Company is in full compliance with the Katmai Agreement, the Company may terminate the Katmai Agreement upon written notice to Katmai. Upon termination of the Katmai Agreement for any reason, all rights and licenses granted to the Company thereunder will terminate. Upon termination of the Katmai Agreement, the Company is obligated, among other things, to (i) grant an exclusive license to Katmai under all of the Company’s right, title and interest in all inventions and know-how developed under the Katmai Agreement existing at the time of termination that are specific to the licensed compounds or products, including without limitation all data and results related to Katmai’s exploitation and (ii) transfer to Katmai ownership and possession of all regulatory filings related to the licensed compounds and products. Unless the Katmai Agreement is terminated for the Company’s material breach, the parties will negotiate in good faith the financial terms pursuant to which the foregoing actions will be conducted, provided that the Company’s performance of such actions may not be conditioned upon the conduct or completion of such negotiations. If the parties are unable to agree upon such terms within the specified time period, then the parties will submit all unresolved matters for resolution by arbitration. LifeArc In April 2020, the Company entered into a license agreement with LifeArc (the LifeArc Agreement) under which the Company was granted an exclusive, worldwide license to certain materials, know-how, and intellectual property rights owned or controlled by LifeArc to develop, manufacture, use, and commercialize certain ULK inhibitors for all applications. The Company also has the right to sublicense (through multiple tiers) its rights under the LifeArc Agreement, subject to certain conditions. The foregoing license is subject to LifeArc’s retained non-exclusive, irrevocable, worldwide, sublicensable (to its academic collaborators), royalty-free right to use the licensed intellectual property rights within all fields of use for LifeArc’s own non-commercial, non-clinical academic research. Notwithstanding its retained rights, LifeArc will not seek to develop or undertake any other ULK1/2 therapeutic development programs either in-house or via third parties until April 2025. The Company is required to use diligent efforts to achieve certain development and regulatory milestones with respect to submission of an IND, initiation of clinical trials, submission of an NDA, and commencement of commercial sales. Under the LifeArc Agreement, the Company was granted the license at no upfront cost and a period of three months after the effective date to conduct experiments on LifeArc’s compounds. Upon completion of this initial testing period, the Company had the option to continue the license and make a one-time license payment of $ 75,000 to LifeArc, which payment was subsequently made. The Company is obligated to make future development milestone payments for a licensed product of up to $ 11.0 million and sales milestone payments of up to $ 50.0 million. The Company is also obligated to pay royalties on net sales of all licensed products, in the low-single digit percentages, subject to certain reductions. No IPR&D expense was recorded during the three and nine months ended September 30, 2021 . The Company recorded IPR&D expense of $ 75,000 for the three and nine months ended September 30, 2020. The Company’s royalty obligations and the LifeArc Agreement will expire, on a licensed product-by-licensed product and country-by-country basis, on the later of (i) ten years from the date of first commercial sale, (ii) when there is no longer a valid patent claim covering such licensed product, or (iii) expiration of regulatory exclusivity for the licensed product in such country. Upon expiration of the LifeArc Agreement, all rights and licenses granted to the Company and under the LifeArc Agreement will continue on a fully paid-up basis. The LifeArc Agreement may be terminated in its entirety by either LifeArc or the Company in (i) the event of an uncured material breach by the other party or (ii) in the event the other party becomes subject to an order by a court of competent jurisdiction for winding-up or dissolution or similar circumstances. Further, LifeArc may terminate the LifeArc Agreement by giving written notice to the Company if (i) the Company fails to comply with its diligence obligations and fails to take remedial actions, (ii) the Company fails to agree on a mechanism to cure a persistent breach, or (iii) the Company fails to provide proof of the insurance coverage as required under the LifeArc Agreement. The Company may terminate the agreement at any time upon the provision of written notice to LifeArc. Upon termination of the LifeArc Agreement for any reason, all rights and licenses granted to the Company, as well as any sublicenses the Company granted thereunder, will terminate. In addition, upon termination of the LifeArc Agreement for any reason other than its natural expiration or termination by the Company for LifeArc’s material breach, LifeArc has an option to negotiate an exclusive, worldwide, sublicensable license to commercialize any patent rights, technical and clinical data, and any development results relating to the licensed products that are owned or controlled by the Company for the purpose of developing, manufacturing and commercializing the licensed products on terms to be negotiated between the parties. University of California, San Francisco In December 2018, the Company entered into a license agreement, as amended (the UCSF Agreement), with The Regents of the University of California, San Francisco (the Regents), under which the Company was granted an exclusive, worldwide, royalty-bearing license under certain patent rights claiming novel covalent inhibitors of GTP- and GDP-bound RAS for the development and commercialization of products covered by such patent rights for the prevention, treatment and amelioration of human cancers and other diseases and conditions. The UCSF Agreement was amended in May 2021. The Company has the right to sublicense (through multiple tiers) its rights under the UCSF Agreement, subject to certain conditions. The foregoing license is subject to various retained rights and restrictions, including (i) the Regents’ reserved right to make, use and practice the licensed patent rights and any technology relating thereto for educational and research purposes, (ii) Howard Hughes Medical Institute’s non-exclusive, fully paid-up, irrevocable worldwide license to use the licensed patent rights for research purposes, (iii) Howard Hughes Medical Institute’s statement of policy on research tools, and (iv) the obligations to the US government under the Bayh-Dole Act, including the obligation to report on the utilization of the invention covered by the licensed patent rights and a non-exclusive, non-transferable, irrevocable, paid-up license to practice or have practiced such invention throughout the world. The Company is required to use diligent efforts to proceed with the development and commercialization of licensed products including by achieving certain milestone events within the specified time periods. Under the UCSF Agreement, the Company made upfront payments of $ 50,000 to the Regents and pays the Regents an annual license maintenance fee during the term of the license, but such fee will not be due on any anniversary if, on that date, the Company is making royalty payments to the Regents. The Company is obligated to make future development and regulatory milestone payments of up to $ 6.4 million and a sales milestone payment of $ 2.0 million for either of the first two licensed products. The Company is also obligated to pay royalties on net sales of all licensed products in the low-single digit percentages, subject to a minimum annual royalty payment in the low six figures, commencing on the year of the first sale of a licensed product and continuing, on a licensed product-by-licensed product and country-by-country basis, until there are no valid claims of the licensed patent rights covering the licensed product in such country. Additionally, the Company is obligated to pay tiered sublicensing fees, with the first two tiers in the low-to-mid teen percentages and the third tier at 30 %, on certain fees the Company receives from any sublicense that the Company grants, depending on the stage of development of a licensed product when such sublicense is granted. Prior to the execution of the amendment, the Company was obligated to make a cash payment to the Regents in the event of the Company’s initial public offering, a change of control transaction or a reverse merger (the Corporate Milestone). In the amendment, the amount of the cash payment payable upon the Company’s achievement of a Corporate Milestone was reduced and the Company agreed to issue the Regents 944,945 shares of the Company’s common stock, which issuance was not contingent upon the achievement of a Corporate Milestone and occurred in May 2021. In August 2021, following the achievement of the Corporate Milestone, the Company made a cash payment to the Regents in the amount of $ 1.7 million. The Company recorded IPR&D expense of $ 1.7 million and $ 7.2 million during the three and nine months ended September 30, 2021 , respectively, related to the issuance of these 944,945 common stock shares and the Corporate Milestone cash payment. No IPR&D expense was recorded during the three and nine months ended September 30, 2020. The UCSF Agreement will expire upon the expiration of the last of the licensed patent rights. The UCSF Agreement may be terminated in its entirety by the Regents (i) for the Company’s uncured breach; (ii) for the Company’s bankruptcy; or (iii) if the Company challenges, directly or indirectly, the validity or enforceability of any licensed patents. Further, if the Company fails to satisfy any diligence milestones, the Regents has the right and option to either terminate the UCSF Agreement or modify the exclusive license granted thereunder to a non-exclusive license. The Company may terminate the UCSF Agreement in its entirety or on a country-by-country basis at any time upon the provision of written notice to the Regents. Upon termination of the UCSF Agreement for any reason, all rights and licenses granted to the Company thereunder will terminate.

Stockholders' Deficit

Stockholders' Deficit	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Stockholders' Deficit	Note 9. Stockholders’ deficit Under its Amended and Restated Certificate of Incorporation dated April 15, 2020, the Company was authorized to issue 147,027,681 shares of its common stock, par value of $ 0.0001 per share. In February 2021, the Company’s Board of Directors increased the authorized number of shares of its common stock to 156,000,000 shares. In connection with the IPO, on July 20, 2021, the Company amended and restated its certificate of incorporation to, among other things, (i) increase the number of authorized shares of common stock from 156,000,000 to 800,000,000 and (ii) authorize 80,000,000 shares of undesignated preferred stock with a par value of $ 0.0001 per share. Convertible preferred stock In 2018 and 2019, the Company issued a total of 38,103,681 shares of its Series A convertible preferred stock at $ 1.667 per share. The Company received proceeds of approximately $ 63.4 million, net of issuance costs. In April 2020, the Company entered into a Series B convertible preferred stock purchase agreement (the Series B Agreement) under which it issued 27,481,001 shares of its Series B-1 convertible preferred stock at various closing dates in 2020, for cash, at a price of $ 5.00 per share, for net proceeds of $ 137.0 million (the Series B-1 Closing). The Series B Agreement contained provisions that potentially obligates the Company to issue 13,175,191 shares of Series B-2 convertible preferred stock at $ 7.50 per share in an additional closing to certain Series B-1 Closing purchasers, upon the achievement of certain milestones as defined in the Series B Agreement, which purchase right terminates on September 30, 2022 or at certain specified events, including an initial public offering of the Company, if any (the Series B-2 Closing). In the event that a Series B-1 Closing purchaser fails to purchase all of its required shares in the subsequent Series B-2 Closing, each of the Series B-1 convertible preferred shares held by such purchaser will automatically be converted into one -tenth of a share of the Company’s common stock. The Company determined its obligation to issue additional shares of its Series B-2 convertible preferred stock in the Series B-1 Closing represented a freestanding financial instrument that required liability accounting. This freestanding preferred stock purchase right liability for the Series B-2 Closing was recorded at fair value and is remeasured at each reporting period. As of the Series B-1 Closing, the estimated fair value of the preferred stock purchase right liability was $ 9.0 million. The Company records any changes in the fair value of the Series B-2 convertible preferred stock purchase right liability as changes in the fair value of convertible preferred stock purchase right liability in the accompanying consolidated statements of operations and comprehensive loss, and recorded a gain of $ 7.4 million for the year ended December 31, 2020. To satisfy its obligation, in January 2021, the Company sold 13,175,191 shares of its Series B-2 convertible preferred stock and an additional 2,756,581 shares of its Series B-2 convertible preferred stock at a price of $ 7.50 per share and received aggregate net proceeds of $ 119.4 million. Also in 2020, the Company issued 4,000,000 shares of its Series B-2 convertible preferred stock at $ 7.50 per share in connection with an asset acquisition (see Note 7). Convertible preferred stock consisted of the following as of December 31, 2020 (in thousands, except share data): December 31, 2020 Preferred Preferred shares Common stock shares issued and Carrying Liquidation issuable upon authorized outstanding value preference conversion Series A preferred stock 38,103,681 38,103,681 $ 63,403 $ 63,519 31,753,064 Series B-1 preferred stock 28,741,400 27,481,001 128,002 137,405 22,900,819 Series B-2 preferred stock 30,777,328 4,000,000 30,000 30,000 3,333,333 Total 97,622,409 69,584,682 $ 221,405 $ 230,924 57,987,216 Upon the closing of the IPO in July 2021, all shares of convertible preferred stock then outstanding converted into 71,263,685 shares of common stock. There were no shares of convertible preferred stock outstanding as of September 30, 2021. Convertible preferred stock rights and preferences The rights and preferences for convertible preferred stock are detailed in the Company’s final prospectus (the Prospectus) filed with the Securities and Exchange Commission (the SEC) pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the Securities Act), on July 16, 2021. Common stock The Company had 800,000,000 and 147,027,681 shares of its common stock authorized as of September 30, 2021 and December 31, 2020 , respectively. The Company had 121,250,375 and 25,189,673 shares of its common stock issued and 118,645,593 and 21,923,173 shares of common stock outstanding as of September 30, 2021 and December 31, 2020, respectively. Shares of common stock subject to repurchase During 2018, the Company issued 1,458,332 shares of restricted stock for cash at a price of $ 0.0001 per share. The restricted stock vests 25 % one year from the vesting commencement date and monthly thereafter over a three-year period and is subject to repurchase by the Company in the event of any voluntary or involuntary termination of services to the Company prior to vesting. Any shares subject to repurchase by the Company are not deemed, for accounting purposes, to be outstanding until those shares vest. As of September 30, 2021 and December 31, 2020 , 303,820 shares and 577,259 shares of common stock, respectively, were subject to repurchase by the Company. The unvested stock liability related to these awards is immaterial for all periods presented. For the three and nine months ended September 30, 2021 , 91,146 and 273,439 shares vested, respectively. For the three and nine months ended September 30, 2020 , 91,146 and 273,438 shares vested, respectively.

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	Note 10. Stock-based compensation In July 2021, the Company’s board of directors adopted and the Company’s stockholders approved the Company’s 2021 Incentive Award Plan (the 2021 Plan), which became effective in connection with the IPO. Upon the adoption of the 2021 Plan, the Company ceased making equity grants under its 2018 Equity Incentive Plan (the Prior Plan). Under the 2021 Plan, the Company may grant stock options, restricted stock, restricted stock units, stock appreciation rights, and other stock or cash-based awards to individuals who are then employees, officers, directors or non-entity consultants of the Company. A total of 15,150,000 shares of common stock were initially reserved for issuance under the 2021 Plan. In addition, the number of shares of common stock available for issuance under the 2021 Plan will be increased annually on the first day of each fiscal year during the term of the 2021 Plan, beginning with the 2022 fiscal year, by an amount equal to the lesser of (i) 5 % of the shares of common stock outstanding on the final day of the immediately preceding calendar year or (ii) such smaller number of shares as determined by the Company’s board of directors. As of September 30, 2021 , there were 14,775,660 stock-based awards available for future grant under the 2021 Plan. Subsequent to July 2021, no further awards will be granted under the Prior Plan and all future stock-based awards will be granted under the 2021 Plan. To the extent outstanding options granted under the Prior Plan are cancelled, forfeited or otherwise terminated without being exercised and would otherwise have been returned to the share reserve under the Prior Plan, the number of shares underlying such awards will be available for future grant under the 2021 Plan. Options granted are exercisable at various dates as determined upon grant and will expire no more than ten years from their date of grant. Stock options generally vest over a four-year term. The exercise price of each option shall be determined by the Company’s Board of Directors based on the estimated fair value of the Company’s stock on the date of the option grant. The exercise price shall not be less than 100 % of the fair market value of the Company’s common stock at the time the option is granted. For holders of more than 10% of the Company’s total combined voting power of all classes of stock, incentive stock options may not be granted at less than 110 % of the fair market value of the Company’s common stock on the date of grant and for a term that exceeds five years . Early exercise is permitted for certain grants under the Prior Plan. Stock options A summary of the Company’s stock option activity under the 2021 Plan and Prior Plan is as follows (in thousands, except share and per share data and years): Weighted- Weighted- average remaining Aggregate average contractual intrinsic Shares exercise price term (years) value Outstanding at December 31, 2020 6,541,422 $ 0.98 9.23 $ 15,571 Granted 8,129,187 5.65 Exercised ( 696,015 ) 1.93 2,545 Canceled ( 192,427 ) 3.70 Outstanding at September 30, 2021 13,782,167 $ 3.65 9.05 $ 242,214 Options exercisable at September 30, 2021 2,614,566 $ 1.68 8.50 $ 51,079 The weighted-average grant date fair value of options granted for the three and nine months ended September 30, 2021 was $ 12.29 and $ 3.96 , respectively, and for the three and nine months ended September 30, 2020 was $ 0.83 and $ 0.81 , respectively. As of September 30, 2021, the unrecognized compensation cost related to unvested stock option grants was $ 32.3 million and is expected to be recognized as expense over approximately 3.11 years. The aggregate fair value of stock options that vested for the three and nine months ended September 30, 2021 was $ 0.4 million and $ 1.0 million, respectively, and for the three and nine months ended September 30, 2020 was $ 0.1 million and $ 0.2 million, respectively. Certain individuals were granted the ability to early exercise their stock options. The shares of common stock issued from the early exercise of unvested stock options are restricted and continue to vest in accordance with the original vesting schedule. The Company has the option to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. The shares purchased by the employees and non-employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be outstanding until those shares vest. The cash received in exchange for exercised and unvested shares related to stock options granted is recorded as a liability for the early exercise of stock options on the accompanying consolidated balance sheets and will be transferred into common stock and additional paid-in capital as the shares vest. As of September 30, 2021 and December 31, 2020 , there were 2,001,823 shares and 2,131,510 shares subject to repurchase by the Company, respectively. As of September 30, 2021 and December 31, 2020 , the Company recorded $ 3.1 million and $ 2.5 million of liabilities associated with shares issued with repurchase rights, respectively, which is recorded in accrued expenses and other current liabilities. In January 2019, the Company granted 250,000 options that vest based on a performance milestone. For the three and nine months ended September 30, 2021 , the Company recognized $ 0 and $ 115,000 of stock-based compensation associated with the performance-based options as the performance milestone was determined to be probable as of March 31, 2021. As of December 31, 2020, the milestone for the performance-based options was not probable of achievement, and therefore, no compensation expense for performance-based options had been recognized. The assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee and nonemployee stock option grants were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Risk-free interest rate 0.91 %- 0.97 % 0.37 %- 0.40 % 0.59 %- 1.09 % 0.37 %- 1.22 % Expected volatility 81.93 %- 84.98 % 77.58 %- 77.81 % 81.93 %- 84.98 % 74.72 %- 77.81 % Expected term (in years) 6.08 6.02 - 6.08 6.08 6.02 - 6.25 Expected dividend yield - -% - -% - -% - -% Employee stock purchase plan In July 2021, the Company’s board of directors adopted and the Company’s stockholders approved the ESPP, which became effective in connection with the IPO. The ESPP permits participants to contribute up to a specified percentage of their eligible compensation during a series of offering periods of 24 months , each comprised of four six-month purchase periods, to purchase the Company’s common stock. The purchase price of the shares will be 85 % of the fair market value of the Company’s common stock on the first day of trading of the applicable offering period or on the applicable purchase date, whichever is lower. A total of 1,260,000 shares of common stock was initially reserved for issuance under the ESPP. The Company recognized $ 278,000 of stock-based compensation expense related to the ESPP during the three and nine months ended September 30, 2021. As of September 30, 2021, the unrecognized compensation cost related to the ESPP was $ 2.6 million and is expected to be recognized as expense over approximately 1.12 years. As of September 30, 2021, $ 604,000 has been withheld on behalf of employees for future purchase under the ESPP and is included in accrued expenses and other current liabilities on the condensed consolidated balance sheet. As of September 30, 2021, no shares have been issued under the ESPP. Restricted stock The Company granted 1,795,827 shares of its restricted stock in 2018, which vest 25 % one year from the vesting commencement date and monthly thereafter over a three-year period. The weighted-average grant date fair value of restricted stock granted in 2018 was $ 0 . No shares of restricted stock were granted during the three and nine months ended September 30, 2021 and 2020. The restricted stock shares are subject to forfeiture upon the stockholders’ termination of employment or service to the Company. Any shares subject to forfeiture are not deemed, for accounting purposes, to be outstanding until those shares vest. As such, the Company recognizes the measurement date fair value of the restricted stock over the vesting period as compensation expense. As of September 30, 2021 and December 31, 2020 , 299,139 shares and 557,731 shares of common stock, respectively, were subject to forfeiture. The summary of the Company’s restricted stock activity during the nine months ended September 30, 2021 is as follows: Number of Weighted- restricted average stock shares grant date outstanding fair Value Nonvested at December 31, 2020 557,731 $ 0.001 Vested ( 258,592 ) 0.001 Nonvested at September 30, 2021 299,139 $ 0.001 At September 30, 2021 , the total unrecognized compensation related to unvested restricted stock awards granted was $ 0 . Stock-based compensation expense The allocation of stock-based compensation for all stock awards was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development 1,665 $ 91 $ 3,080 $ 191 General and administrative 1,352 85 2,368 199 Total $ 3,017 $ 176 $ 5,448 $ 390 Common stock reserved for future issuance Common stock reserved for future issuance consisted of the following as of September 30, 2021 and December 31, 2020: September 30, December 31, 2021 2020 Conversion of preferred stock outstanding — 57,987,216 Conversion of preferred stock in future issuance (B-2) — 10,979,319 Stock options issued and outstanding 13,782,167 6,541,422 Awards available for future grant 14,775,660 2,314,746 Shares available for purchase under the ESPP 1,260,000 — Total 29,817,827 77,822,703

Leases

Leases	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Leases	Note 11. Leases Operating leases The Company has facility leases for office space under non-cancellable and cancelable operating leases with various expiration dates through 2032 and equipment under a non-cancellable operating lease with a term expiring in 2022 . Operating lease cost was approximately $ 905,000 and $ 1.6 million, including variable lease costs of $ 96,000 and $ 324,000 , and short-term lease costs of $ 30,000 and $ 89,000 during the three and nine months ended September 30, 2021 , respectively. Operating lease cost was approximately $ 342,000 and $ 1.0 million, including variable lease costs of $ 94,000 and $ 269,000 , and short-term lease costs of $ 26,000 and $ 67,000 during the three and nine months ended September 30, 2020 , respectively. The Company paid $ 803,000 and $ 726,000 in ca sh for operating leases that were included in the operating activities section of the consolidated statements of cash flows for the nine months ended September 30, 2021 and 2020, respectively. The weighted-average remaining lease term and the weighted-average discount rate of the Company’s operating leases was 9 .36 years and 7.1 % a t September 30, 2021 , respectively. The weighted-average remaining lease term and the weighted-average discount rate of the Company’s operating leases was 3.16 years and 7.8 % at December 31, 2020, respectively. The weighted-average remaining lease term does not include any renewal options at the election of the Company. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. Facility leases In 2018, the Company entered into a lease agreement for approximately 11,000 square feet of office space in San Diego, California which was subsequently amended resulting in a total of approximately 16,153 square feet of office space leased. The amended space is accounted for as a separate lease. The non-cancellable operating leases expire in May 2024 . The Company’s lease payments consist primarily of fixed rental payments for the right to use the underlying leased assets over the lease terms. The Company is responsible for operating expenses over base operating expenses as defined in the original lease agreement. In September 2020, the Company entered into a lease agreement for 59,407 square feet of laboratory and office space in San Diego, California (2020 Lease), which represented a portion of a new facility that is under construction. The construction and design of the asset is the primary responsibility of the lessor. The Company is involved in certain aspects of construction and design for certain interior features and leasehold improvements that will be beneficial to the Company to better suit its business needs and intended purpose of the space. The lease is accounted for as an operating lease and commenced in August 2021 . The lease has an initial term of 10.5 years and includes aggregate monthly payments to the lessor of approximately $ 39.5 million beginning in January 2023 with a rent escalation clause, and a tenant improvement allowance of approximately $ 13.4 million. The lease is cancellable at the Company’s request after the 84 th month with 12 months written notice and a lump-sum cancellation payment of $ 1.9 million. As discussed in Note 2, the Company provided a letter of credit to the lessor for $ 312,000 , which expires October 31, 2031 . In March 2021, the Company entered into the first amendment to the 2020 Lease to expand the rented premises by 18,421 square feet for additional consideration of $ 96,000 per month starting in January 2023 with a rent escalation clause and to receive an additional $ 3.4 million tenant improvement allowance. The payment associated with the option to cancel the lease after the 84 th month was increased to $ 2.5 million, and the letter of credit provided to the lessor was increased to $ 408,000 . Future minimum lease payments under the operating leases with initial lease terms in excess of one year as of September 30, 2021 are as follows (in thousands): Year ending December 31, 2021 (three months remaining) $ 270 2022 969 2023 5,963 2024 5,578 2025 5,333 Thereafter 36,061 Total lease payments $ 54,174 Less: Amount representing interest ( 17,167 ) Less: Tenant improvement allowance receivable ( 16,774 ) Operating lease liabilities $ 20,233

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 12. Commitments and contingencies As of September 30, 2021 and December 31, 2020 , there was no litigation against the Company.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Note 13. Income taxes No provision for federal, state or foreign income taxes has been recorded for the three and nine months ended September 30, 2 0 21 and 2 0 20 . The Company has incurred net operating losses for all the periods presented and has not reflected any benefit of such net operating loss carryforwards in the accompanying consolidated financial statements due to uncertainty around utilizing these tax attributes within their respective carryforward periods. The Company has recorded a full valuation allowance against all of its deferred tax assets as it is not more likely than not that such assets will be realized in the near future. The Company’s policy is to recognize interest expense and penalties related to income tax matters as tax expense. For the three and nine months ended September 30, 2021 and 2020 , the Company has no t recognized any interest or penalties related to income taxes.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	Note 14. Net loss per share The following table summarizes the computation of basic and diluted net loss per share of the Company (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Net loss $ ( 46,069 ) $ ( 10,608 ) $ ( 92,300 ) $ ( 39,757 ) Weighted-average shares of common stock used in computing net loss per share, basic and diluted 99,127,286 21,084,657 48,584,029 20,851,262 Net loss per share, basic and diluted $ ( 0.46 ) $ ( 0.50 ) $ ( 1.90 ) $ ( 1.91 ) The Company’s potentially dilutive securities, which include its convertible preferred stock, options to purchase common stock, shares purchasable under the ESPP and common stock subject to repurchase related to unvested restricted stock and options early exercised, 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, 2021 2020 2021 2020 Convertible preferred stock issued — 54,653,883 — 54,653,883 Conversion of convertible preferred stock in future issuance (B-2) — 10,979,319 — 10,979,319 Options to purchase common stock 13,782,167 6,666,515 13,782,167 6,666,515 Restricted stock subject to future vesting 602,959 1,503,303 602,959 1,503,303 Options early exercised subject to future vesting 2,001,823 2,686,456 2,001,823 2,686,456 Estimated shares purchasable under the ESPP 299,092 — 299,092 — Total potentially dilutive shares 16,686,041 76,489,476 16,686,041 76,489,476

Retirement Plan

Retirement Plan	9 Months Ended
	Sep. 30, 2021
Compensation And Retirement Disclosure [Abstract]
Retirement Plan	Note 15. Retirement plan The Company sponsors an employee savings plan that qualifies as a deferred salary arrangement under Section 401(k) of the US Internal Revenue Code (IRC). Participating employees may defer up to the Internal Revenue Service (IRS) annual contribution limit. Beginning in 2021, the Company provides a safe harbor contribution of 3.0 % of the employee’s compensation, not to exceed eligible limits. For the three and nine months ended September 30, 2021, the Company incurre d $ 146,000 and $ 378,000 in expenses related to the safe harbor contribution, respectively. No expenses were incurred for the three and nine months ended September 30, 2020 related to the safe harbor contribution.

COVID-19 pandemic

COVID-19 pandemic	9 Months Ended
	Sep. 30, 2021
Risks and Uncertainties [Abstract]
COVID-19 Pandemic	Note 16. COVID-19 pandemic The current COVID-19 pandemic, which is impacting worldwide economic activity, poses the risk that the Company or its employees, contractors, suppliers, and other partners may be prevented from conducting business activities for an indefinite period of time, including due to shutdowns that may be requested or mandated by governmental authorities. During the three and nine months ended September 30, 2021 and 2020 , the Company has not experienced significant impact from the pandemic. The extent to which the COVID-19 pandemic will impact the Company’s business will depend on future developments that are highly uncertain and cannot be predicted at this time.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Note 17. Related party transactions Erasca Foundation In May 2021, the Company established the Erasca Foundation to provide support such as direct research grants, hardship grants, patient advocacy, patient education in underserved populations, and funding for other initiatives to positively impact society. The Company's chief executive officer and certain board members serve as directors of the Erasca Foundation and the Company's chief executive officer, chief financial officer, and general counsel are also officers of the Erasca Foundation. In July 2021, the Company issued 1,093,557 shares of its common stock to the Erasca Foundation as a contribution and recorded $ 17.5 million to contribution of common stock to Erasca Foundation in the condensed consolidated statements of operations and comprehensive loss. Disgorgement of stockholder's short-swing profits In August 2021, the Company received $ 553,000 related to the recovery of short-swing profits from a private investment fund affiliated with one of its board members, a related party, under Section 16(b) of the Securities Exchange Act of 1934, as amended (the Exchange Act). The Company recognized these proceeds as a capital contribution from a stockholder with an increase to additional paid-in-capital in its condensed consolidated balance sheet and as cash provided by financing activities in its condensed consolidated statement of cash flows.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Use of Estimates	Use of estimates The preparation of the Company’s consolidated financial statements in conformity with US GAAP requires the Company to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the consolidated financial statements and accompanying notes. Accounting estimates and management judgments reflected in the consolidated financial statements include, but are not limited to, the accrual of research and development expenses, fair value of common stock, preferred stock and freestanding instruments, stock-based compensation expense, and the incremental borrowing rate for determining the operating lease asset and liability. Management evaluates its estimates on an ongoing basis. Although estimates are based on the Company’s historical experience, knowledge of current events, and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
Unaudited Interim Financial Information	Unaudited interim financial information The accompanying condensed consolidated balance sheet as of September 30, 2021, the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020, the condensed consolidated statements of convertible preferred stock and stockholders’ deficit for the three and nine months ended September 30, 2021 and 2020 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. The unaudited condensed 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 statement of the Company’s condensed consolidated financial position as of September 30, 2021 and the condensed consolidated results of its operations and cash flows for the three and nine months ended September 30, 2021 and 2020. The condensed consolidated financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2021 and 2020 are unaudited. The condensed consolidated results for the three and nine months ended September 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period.
Concentration of Credit Risk and Off-Balance Sheet Risk	Concentration of credit risk and off-balance sheet risk Financial instruments which potentially subject the Company to significant concentration of credit risk consist of cash and cash equivalents and investments. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts, and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. The Company’s investment policy includes guidelines for the quality of the related institutions and financial instruments and defines allowable investments that the Company may invest in, which the Company believes minimizes the exposure to concentration of credit risk.
Cash, Cash Equivalents and Restricted Cash	Cash, cash equivalents and restricted cash Cash and cash equivalents include cash in readily available checking and savings accounts, money market funds, commercial paper, and corporate debt securities. The Company considers all highly liquid investments with an original maturity of three months or less from the date of purchase to be cash equivalents. The Company had deposited cash of $ 408,000 and $ 312,000 as of September 30, 2021 and December 31, 2020, respectively, to secure a letter of credit in connection with the lease of the Company’s facilities (see Note 11). The Company has classified the restricted cash as a noncurrent asset on its condensed consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2021 2020 Cash and cash equivalents $ 445,811 $ 62,017 Restricted cash 408 312 Total cash, cash equivalents and restricted cash as shown on the condensed $ 446,219 $ 62,329
Investments	Investments The Company classifies all marketable securities as available-for-sale, as the sale of such securities may be required prior to maturity. Management determines the appropriate classification of its investments in debt securities at the time of purchase. Investments with original maturities beyond three months at the date of purchase and which mature at, or less than 12 months from, the balance sheet date are classified as short-term investments. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported as accumulated other comprehensive income (loss) until realized. The amortized cost of available-for-sale debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in interest income. The Company regularly reviews all its investments for other-than-temporary declines in fair value. The review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. When the Company determines that the decline in fair value of an investment is below its accounting basis and the decline is other-than-temporary, the Company reduces the carrying value of the security it holds and records a loss for the amount of such decline. Realized gains and losses and declines in value judged to be other than temporary, if any, on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income.
Fair Value Measurements	Fair value measurements Certain assets and liabilities are carried at fair value under US GAAP. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Financial assets and liabilities carried at fair value are classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: Level 1—Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2—Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. Level 3—Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).
Property and Equipment, Net	Property and equipment, net Property and equipment are stated at cost less accumulated depreciation. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the respective assets, generally three to seven years . Leasehold improvements are amortized over the shorter of the estimated useful lives of the assets or the remaining lease term.
Impairment of Long-Lived Assets	Impairment of long-lived assets The Company continually evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book values of the assets exceed their fair value. The Company did no t recognize any impairment losses for the three and nine months ended September 30, 2021 and 2020 .
Leases	Leases The Company leases real estate facilities and equipment under non-cancelable and cancelable operating leases with various expiration dates through fiscal year 2032. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present, the existence of an identified asset(s), if any, and the Company’s control over the use of the identified asset(s), if applicable. Operating leases are included in operating lease assets and in operating lease liabilities in the accompanying condensed consolidated balance sheets. Operating lease assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term discounted based on the more readily determinable of (i) the rate implicit in the lease or (ii) the Company’s incremental borrowing rate (which is the estimated rate the Company would be required to pay for a collateralized borrowing equal to the total lease payments over the term of the lease). Because the Company’s operating leases generally do not provide an implicit rate, the Company estimates its incremental borrowing rate based on the information available at lease commencement date for borrowings with a similar term. The Company’s operating lease assets are measured based on the corresponding operating lease liability adjusted for (i) payments made to the lessor at or before the commencement date, (ii) initial direct costs incurred and (iii) tenant incentives under the lease. The Company does not assume renewals or early terminations unless it is reasonably certain to exercise these options at commencement. The Company elected the practical expedient which allows the Company to not allocate consideration between lease and non-lease components. Variable lease payments are recognized in the period in which the obligations for those payments are incurred. In addition, the Company elected the practical expedient such that it does not recognize lease assets or lease liabilities for leases with a term of 12 months or less of all asset classes. Operating lease expense is recognized on a straight-line basis over the lease term. Certain of the Company's real estate leases include tenant improvement allowances, which are recognized as lease incentives and amortized on a straight-line basis over the lease term as an offset to rent expense.
Research and Development Expense	Research and development expense Research and development expenses consist of external and internal costs associated with the Company’s research and development activities, including its discovery and research efforts and the preclinical and clinical development of its product candidates. Research and development costs are expensed as incurred. The Company’s research and development expenses include external costs, consisting of expenses incurred under arrangements with third parties, such as contract research organizations (CROs), contract manufacturing organizations (CMOs), consultants and its scientific advisors; and internal costs, consisting of employee-related expenses, including salaries, benefits, and stock-based compensation for those individuals involved in research and development efforts, the costs of laboratory supplies and acquiring, developing and manufacturing preclinical study materials, and facilities and depreciation, which include direct and allocated expenses for rent of facilities and depreciation of equipment. The Company records accruals for estimated research and development costs, comprising payments for work performed by third party contractors, laboratories, and others. Some of these contractors bill monthly based on actual services performed, while others bill periodically based upon achieving certain contractual milestones. For the latter, the Company accrues the expenses as goods or services are used or rendered. Non-refundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized as prepaid expenses until the related goods are delivered or services are performed.
In-Process Research and Development Expense	In-process research and development expense The Company has acquired rights as part of asset acquisitions or in-licenses to develop and commercialize product candidates. Upfront payments that relate to the acquisition of a new drug compound, as well as pre-commercial milestone payments, are immediately expensed as in-process research and development (IPR&D) in the period in which they are incurred, provided that the new drug compound did not also include processes or activities that would constitute a “business” as defined under US GAAP, the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no established alternative future use. The Company accounts for contingent consideration payable upon achievement of certain regulatory, development or sales milestones in such asset acquisitions when the underlying contingency is resolved. Milestone payments made to third parties subsequent to regulatory approval will be capitalized as intangible assets and amortized over the estimated remaining useful life of the related product.
Patent Costs	Patent costs The Company expenses all costs as incurred in connection with patent applications (including direct application fees, and the legal and consulting expenses related to making such applications) and such costs are included in general and administrative expenses in the consolidated statements of operations and comprehensive loss.
Deferred Offering Costs	Deferred offering costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ deficit as a reduction of proceeds generated as a result of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. There were no deferred offering costs as of September 30, 2021 and December 31, 2020 .
Common Stock Valuation	Common stock valuation Due to the absence of an active market for the Company’s common stock prior to the IPO, the Company utilized methodologies, approaches and assumptions consistent with the American Institute of Certified Public Accountants’ Audit and Accounting Practice Guide: Valuation of Privately-Held Company Equity Securities Issued as Compensation to estimate the fair value of its common stock. In determining the exercise prices for options granted, the Company has considered the fair value of the common stock as of the grant date. Prior to the IPO, the fair value of the common stock was determined based upon a variety of factors, including valuations of the Company’s common stock performed with the assistance of independent third-party valuation specialists; the Company’s stage of development and business strategy, including the status of research and development efforts of its product candidates, and the material risks related to its business and industry; the Company’s business conditions and projections; the Company’s results of operations and financial position, including its levels of available capital resources; the valuation of publicly traded companies in the life sciences and biotechnology sectors, as well as recently completed mergers and acquisitions of peer companies; the lack of marketability of the Company’s common stock as a private company; the prices of the Company’s convertible preferred stock sold to investors in arm’s length transactions and the rights, preferences and privileges of its convertible preferred stock relative to those of its common stock; the likelihood of achieving a liquidity event for the holders of the Company’s common stock, such as an initial public offering or a sale of the Company given prevailing market conditions; trends and developments in its industry; the hiring of key personnel and the experience of management; and external market conditions affecting the life sciences and biotechnology industry sectors. Significant changes to the key assumptions underlying the factors used could result in different fair values of common stock at each valuation date. After the completion of the IPO, the fair value of each share of common stock is based on the closing price of the Company’s common stock as reported by the Nasdaq Global Select Market (Nasdaq).
Share-based Compensation	Stock-based compensation The Company measures employee and nonemployee stock-based awards based on the fair value on the date of grant and records compensation expense on a straight-line basis over the requisite service period of the award. The Company records the expense for stock-based awards subject to performance-based milestone vesting over the implied service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the expected satisfaction of the performance conditions at each reporting date. All stock-based compensation costs are recorded in the consolidated statements of operations and comprehensive loss based upon the underlying employees or nonemployee’s roles within the Company. Forfeitures are accounted for as they occur. The fair value of stock option grants and shares purchasable under the Company's 2021 Employee Stock Purchase Plan (ESPP) is estimated on the date of grant using the Black-Scholes options-pricing model, which requires inputs based on certain subjective assumptions, including the: • Fair value of common stock. As there was no active market for the Company’s common stock prior to the IPO, the Company estimated the fair value of common stock on the date of grant based on the then current facts and circumstances. • Risk-free interest rate. The risk-free interest rate is based on the US Treasury zero-coupon issues in effect at the time of grant for periods corresponding with the expected term of the stock-based awards. • Expected volatility. Given that the Company’s common stock was privately held prior to the IPO, there was no active trading market for its common stock. The Company derived the expected volatility from the average historical volatilities over a period approximately equal to the expected term of comparable publicly traded companies within its peer group that were deemed to be representative of future stock price trends. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. • Expected term. The expected term represents the period that the stock-based awards are expected to be outstanding. The expected term of stock options issued is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term) as the Company has concluded that its stock option exercise history does not provide a reasonable basis upon which to estimate expected term. • Expected dividend yield. The Company has never paid dividends on its common stock and does not anticipate paying any dividends in the foreseeable future. Therefore, the Company used an expected dividend yield of zero . The fair value of each restricted common stock award is estimated on the date of grant based on the fair value of the Company’s common stock on that same date.
Classification and Accretion of Convertible Preferred Stock	Classification and accretion of convertible preferred stock The Company’s convertible preferred stock is classified outside of stockholders’ deficit on the consolidated balance sheets because the holders of such shares have liquidation rights in the event of a deemed liquidation that, in certain situations, are not solely within the control of the Company and would require the redemption of the then-outstanding convertible preferred stock. The convertible preferred stock is not redeemable, except in the event of a deemed liquidation. Because the occurrence of a deemed liquidation event is not currently probable, the carrying values of the convertible preferred stock are not being accreted to their redemption values. Subsequent adjustments to the carrying values of the convertible preferred stock would be made only when a deemed liquidation event becomes probable.
Preferred Stock Purchase Right Liabilities	Preferred stock purchase right liabilities The Company has entered into convertible preferred stock financings where, in addition to the initial closing, investors agree to buy, and the Company agrees to sell, additional shares of that convertible preferred stock at a fixed price in the event that certain conditions are met or agreed upon milestones are achieved. The Company evaluates this purchase right and assesses whether it meets the definition of a freestanding instrument and, if so, determines the fair value of the purchase right liability and records it on the balance sheet with the remainder of the proceeds raised allocated to convertible preferred stock. The preferred stock purchase right liability is revalued at each reporting period with changes in the fair value of the liability recorded as change in fair value of preferred stock purchase right liability in the consolidated statements of operations and comprehensive loss. The preferred stock purchase right liability is revalued at settlement and the resultant fair value, if any, is then reclassified to convertible preferred stock at that time.
Income Taxes	Income taxes The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the Company’s consolidated financial statements or tax returns. Under this method, deferred tax assets and liabilities are determined based on differences between the financial statement carrying amounts and the tax bases of the assets and liabilities using the enacted tax rates in effect in the years in which the differences are expected to reverse. A valuation allowance against deferred tax assets is recorded if, based on the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. As of September 30, 2021 , the Company’s tax years since inception are subject to examination by taxing authorities due to the Company’s unutilized net operating losses and tax credits.
Comprehensive Income (Loss)	Comprehensive income (loss) The Company reports all components of comprehensive income (loss), including net loss, in the consolidated financial statements in the period in which they are recognized. Comprehensive income (loss) is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on investments. Other comprehensive income includes unrealized gains and losses on investments, which was the only difference between net loss and comprehensive loss for the applicable periods.
Net Loss Per Share	Net loss per share The Company’s net loss is equivalent to net loss attributable to common stockholders for all periods presented. Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, the convertible preferred stock, options to purchase common stock, shares purchasable under the ESPP and common stock subject to repurchase related to unvested restricted stock and options early exercised are considered to be potentially dilutive securities. Basic and diluted net loss per share is presented in conformity with the two-class method required for participating securities as the convertible preferred stock is considered a participating security because it participates in dividends with common stock. The Company also considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. The Company’s participating securities do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. As the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.
Segments	Segments The Company has determined that its chief executive officer is the chief operating decision maker (CODM). The Company operates and manages the business as one reporting and one operating segment, which is the business of discovering and developing precision medicines for the benefit of patients with cancer. The Company’s CODM reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. All of the Company’s assets are located in the United States.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Adopted	Recently adopted accounting pronouncements In August 2018, the FASB issued ASU 2018-13, Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement. The primary focus of the standard is to improve the effectiveness of the disclosure requirements for fair value measurements. The Company adopted this guidance on January 1, 2020 , with no material impact on its consolidated financial statements or related disclosures. In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). The new standard will align the requirements for capitalizing implementation costs for hosting arrangements (services) with costs for internal-use software (assets). As a result, certain implementation costs incurred in hosting arrangements will be deferred and amortized. The Company adopted ASU 2018-15 on January 1, 2021 , and the adoption had an immaterial impact on its consolidated financial statements and related disclosures. Recently issued accounting pronouncements not yet adopted 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 (JOBS Act) and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application 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. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13) and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The 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. The Company is currently evaluating the potential impact ASU 2016-13, and related updates, will have on its consolidated financial statements and related disclosures upon adoption. In August 2020, the FASB issued ASU 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) (ASU 2020-06), which simplifies the accounting for convertible instruments and contracts in an entity’s own equity. This guidance is effective for the Company in its annual reporting period beginning after December 15, 2023, including interim periods within that reporting period, with early adoption permitted only as of annual reporting periods beginning after December 15, 2020. The Company is currently assessing the impact this standard will have on its consolidated financial statements and related disclosures upon adoption.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2021 2020 Cash and cash equivalents $ 445,811 $ 62,017 Restricted cash 408 312 Total cash, cash equivalents and restricted cash as shown on the condensed $ 446,219 $ 62,329

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis and their respective input levels based on the fair value hierarchy (in thousands): Fair value measurements as of September 30, 2021 using Quoted prices in Significant Significant active markets other unobservable September 30, for identical observable inputs 2021 assets (level 1) inputs (level 2) (level 3) Assets: Money market funds (1) $ 436,727 $ 436,727 $ — $ — US government securities (2) 10,031 — 10,031 — Corporate debt securities (2) 1,517 — 1,517 — Commercial paper (2) 27,776 — 27,776 — Supranational debt securities (2) 1,510 — 1,510 — Total fair value of assets $ 477,561 $ 436,727 $ 40,834 $ — (1) Included as cash and cash equivalents on the condensed consolidated balance sheets. (2) Included as short-term investments on the condensed consolidated balance sheets. As of September 30, 2021 , there were no financial liabilities measured at fair value on a recurring basis. Fair value measurements as of December 31, 2020 using Quoted prices in Significant Significant active markets other unobservable December 31, for identical observable inputs 2020 assets (level 1) inputs (level 2) (level 3) Assets: Money market funds (1) $ 57,238 $ 57,238 $ — $ — Commercial paper (1) 900 — 900 — US treasury securities (2) 38,492 38,492 — — Corporate debt securities (2) 3,793 — 3,793 — Commercial paper (2) 11,040 — 11,040 — Total fair value of assets $ 111,463 $ 95,730 $ 15,733 $ — Liabilities: Preferred stock purchase right liability 1,615 — — 1,615 Total fair value of liabilities $ 1,615 $ — $ — $ 1,615 (1) Included as cash and cash equivalents on the consolidated balance sheets. (2) Included as short-term investments on the consolidated balance sheets.
Summary of Assumptions Used to Determine Fair Value of Preferred Stock Purchase Right Liability	The assumptions used in the Black-Scholes option pricing model to determine the fair value of the preferred stock purchase right liability at settlement date and December 31, 2020 were as follows: Settlement Date December 31, 2020 Fair value of underlying preferred stock $ 6.11 $ 6.11 Risk-free interest rate 0.07 % 0.08 % Expected volatility 74.4 % 71.8 % Expected term (in years) 0.00 0.08 Expected dividend yield — % — %

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2021
Investments Debt And Equity Securities [Abstract]
Summary of Investments Accounted for Available-for-Sale-Securities	The following tables summarize the Company’s investments accounted for as available-for-sale securities (in thousands, except years): September 30, 2021 Maturity Amortized Unrealized Unrealized Estimated (in years) cost losses gains fair value US government securities 1 or less $ 10,031 $ — $ — 10,031 Corporate debt securities 1 or less 1,517 — — 1,517 Commercial paper 1 or less 27,776 — — 27,776 Supranational debt securities 1 or less 1,510 — — 1,510 Total $ 40,834 $ — $ — $ 40,834 December 31, 2020 Maturity Amortized Unrealized Unrealized Estimated (in years) cost losses gains fair value US treasury securities 1 or less $ 38,489 $ — $ 3 $ 38,492 Corporate debt securities 1 or less 3,794 ( 1 ) — 3,793 Commercial paper 1 or less 11,040 — — 11,040 Total $ 53,323 $ ( 1 ) $ 3 $ 53,325

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): September 30, December 31, 2021 2020 Leasehold improvements $ 795 $ 795 Construction in progress 4,712 — Laboratory equipment 2,186 1,380 Furniture and fixtures 1,598 165 Office equipment 61 61 Software 87 70 Computer equipment 488 278 Property and equipment 9,927 2,749 Less accumulated depreciation and amortization ( 1,407 ) ( 902 ) Property and equipment, net $ 8,520 $ 1,847

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, December 31, 2021 2020 Accrued research and development expenses $ 6,647 $ 6,649 Accrued compensation 4,711 2,416 Unvested early exercised stock option liability 3,057 2,526 Accrued construction in progress 1,834 — Accrued legal 174 194 Other accruals 977 140 Total $ 17,400 $ 11,925

Stockholders' Deficit (Tables)

Stockholders' Deficit (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Schedule of Convertible Preferred Stock	Convertible preferred stock consisted of the following as of December 31, 2020 (in thousands, except share data): December 31, 2020 Preferred Preferred shares Common stock shares issued and Carrying Liquidation issuable upon authorized outstanding value preference conversion Series A preferred stock 38,103,681 38,103,681 $ 63,403 $ 63,519 31,753,064 Series B-1 preferred stock 28,741,400 27,481,001 128,002 137,405 22,900,819 Series B-2 preferred stock 30,777,328 4,000,000 30,000 30,000 3,333,333 Total 97,622,409 69,584,682 $ 221,405 $ 230,924 57,987,216

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	A summary of the Company’s stock option activity under the 2021 Plan and Prior Plan is as follows (in thousands, except share and per share data and years): Weighted- Weighted- average remaining Aggregate average contractual intrinsic Shares exercise price term (years) value Outstanding at December 31, 2020 6,541,422 $ 0.98 9.23 $ 15,571 Granted 8,129,187 5.65 Exercised ( 696,015 ) 1.93 2,545 Canceled ( 192,427 ) 3.70 Outstanding at September 30, 2021 13,782,167 $ 3.65 9.05 $ 242,214 Options exercisable at September 30, 2021 2,614,566 $ 1.68 8.50 $ 51,079
Assumptions used to Determine Fair Value of Stock Option Grants	The assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee and nonemployee stock option grants were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Risk-free interest rate 0.91 %- 0.97 % 0.37 %- 0.40 % 0.59 %- 1.09 % 0.37 %- 1.22 % Expected volatility 81.93 %- 84.98 % 77.58 %- 77.81 % 81.93 %- 84.98 % 74.72 %- 77.81 % Expected term (in years) 6.08 6.02 - 6.08 6.08 6.02 - 6.25 Expected dividend yield - -% - -% - -% - -%
Summary of Restricted Stock Activity	The summary of the Company’s restricted stock activity during the nine months ended September 30, 2021 is as follows: Number of Weighted- restricted average stock shares grant date outstanding fair Value Nonvested at December 31, 2020 557,731 $ 0.001 Vested ( 258,592 ) 0.001 Nonvested at September 30, 2021 299,139 $ 0.001
Schedule of Stock-based Compensation Expense	The allocation of stock-based compensation for all stock awards was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development 1,665 $ 91 $ 3,080 $ 191 General and administrative 1,352 85 2,368 199 Total $ 3,017 $ 176 $ 5,448 $ 390
Summary of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance consisted of the following as of September 30, 2021 and December 31, 2020: September 30, December 31, 2021 2020 Conversion of preferred stock outstanding — 57,987,216 Conversion of preferred stock in future issuance (B-2) — 10,979,319 Stock options issued and outstanding 13,782,167 6,541,422 Awards available for future grant 14,775,660 2,314,746 Shares available for purchase under the ESPP 1,260,000 — Total 29,817,827 77,822,703

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Schedule of Future Minimum Lease Payments under Operating Leases	Future minimum lease payments under the operating leases with initial lease terms in excess of one year as of September 30, 2021 are as follows (in thousands): Year ending December 31, 2021 (three months remaining) $ 270 2022 969 2023 5,963 2024 5,578 2025 5,333 Thereafter 36,061 Total lease payments $ 54,174 Less: Amount representing interest ( 17,167 ) Less: Tenant improvement allowance receivable ( 16,774 ) Operating lease liabilities $ 20,233

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
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 (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Net loss $ ( 46,069 ) $ ( 10,608 ) $ ( 92,300 ) $ ( 39,757 ) Weighted-average shares of common stock used in computing net loss per share, basic and diluted 99,127,286 21,084,657 48,584,029 20,851,262 Net loss per share, basic and diluted $ ( 0.46 ) $ ( 0.50 ) $ ( 1.90 ) $ ( 1.91 )
Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share	The Company’s potentially dilutive securities, which include its convertible preferred stock, options to purchase common stock, shares purchasable under the ESPP and common stock subject to repurchase related to unvested restricted stock and options early exercised, 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, 2021 2020 2021 2020 Convertible preferred stock issued — 54,653,883 — 54,653,883 Conversion of convertible preferred stock in future issuance (B-2) — 10,979,319 — 10,979,319 Options to purchase common stock 13,782,167 6,666,515 13,782,167 6,666,515 Restricted stock subject to future vesting 602,959 1,503,303 602,959 1,503,303 Options early exercised subject to future vesting 2,001,823 2,686,456 2,001,823 2,686,456 Estimated shares purchasable under the ESPP 299,092 — 299,092 — Total potentially dilutive shares 16,686,041 76,489,476 16,686,041 76,489,476

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands	Jul. 20, 2021USD ($)$ / sharesshares	Jul. 09, 2021	Jul. 31, 2021shares	Sep. 30, 2021USD ($)shares	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)
Organization And Basis Of Presentation [Line Items]
Cash, cash equivalents, and short-term investments				$ 486,600	$ 486,600
Accumulated deficit				$ (207,702)	(207,702)	$ (115,402)
Net proceeds received from initial public offering (IPO)					$ 316,999
Reverse stock split ratio		1.2
Reverse stock split, description					On July 9, 2021, the Company effected a one-for-1.2 reverse stock split of its issued and outstanding shares of common stock (the Reverse Stock Split).
Common Stock
Organization And Basis Of Presentation [Line Items]
Convertible preferred stock converted into shares of common stock | shares				71,263,685
IPO | Common Stock
Organization And Basis Of Presentation [Line Items]
Net proceeds received from initial public offering (IPO)	$ 317,000
Stock issued and sold | shares	21,562,500			21,562,500
Price per share | $ / shares	$ 16
Convertible preferred stock converted into shares of common stock | shares	71,263,685		71,263,685
Underwriting discounts and commissions	$ 24,200
Offering costs	$ 3,800
Underwriters Option to Purchase Shares | Common Stock
Organization And Basis Of Presentation [Line Items]
Stock issued and sold | shares	2,812,500

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)Segment	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 408,000		$ 408,000		$ 312,000
Impairment losses	0	$ 0	0	$ 0
Deferred offering costs	$ 0		0		$ 0
Expected dividend yield			$ 0
Number of operating segment | Segment			1
Number of reporting segment | Segment			1
ASU 2018-13
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true		true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020		Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true		true
ASU 2018-15
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true		true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2021		Jan. 1, 2021
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true		true
Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets			3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets			7 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 445,811	$ 65,376	$ 62,017
Restricted cash	408		312
Total cash, cash equivalents and restricted cash as shown on the condensed consolidated statements of cash flows	$ 446,219		$ 62,329

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands		Sep. 30, 2021		Dec. 31, 2020
Assets:
Total fair value of assets		$ 477,561		$ 111,463
Liabilities:
Total fair value of liabilities				1,615
Preferred Stock Purchase Right Liability
Liabilities:
Total fair value of liabilities				1,615
Money Market Funds | Cash and Cash Equivalents
Assets:
Total fair value of assets		436,727	[1]	57,238	[2]
US Treasury Securities | Short-Term Investments
Assets:
Total fair value of assets	[3]			38,492
US Government Securities | Short-Term Investments
Assets:
Total fair value of assets	[4]	10,031
Corporate Debt Securities | Short-Term Investments
Assets:
Total fair value of assets		1,517	[4]	3,793	[3]
Commercial Paper | Cash and Cash Equivalents
Assets:
Total fair value of assets	[2]			900
Commercial Paper | Short-Term Investments
Assets:
Total fair value of assets		27,776	[4]	11,040	[3]
Supranational Debt Securities | Short-Term Investments
Assets:
Total fair value of assets	[4]	1,510
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total fair value of assets		436,727		95,730
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds | Cash and Cash Equivalents
Assets:
Total fair value of assets		436,727	[1]	57,238	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1) | US Treasury Securities | Short-Term Investments
Assets:
Total fair value of assets	[3]			38,492
Significant Other Observable Inputs (Level 2)
Assets:
Total fair value of assets		40,834		15,733
Significant Other Observable Inputs (Level 2) | US Government Securities | Short-Term Investments
Assets:
Total fair value of assets	[4]	10,031
Significant Other Observable Inputs (Level 2) | Corporate Debt Securities | Short-Term Investments
Assets:
Total fair value of assets		1,517	[4]	3,793	[3]
Significant Other Observable Inputs (Level 2) | Commercial Paper | Cash and Cash Equivalents
Assets:
Total fair value of assets	[2]			900
Significant Other Observable Inputs (Level 2) | Commercial Paper | Short-Term Investments
Assets:
Total fair value of assets		27,776	[4]	11,040	[3]
Significant Other Observable Inputs (Level 2) | Supranational Debt Securities | Short-Term Investments
Assets:
Total fair value of assets	[4]	$ 1,510
Significant Unobservable Inputs (Level 3)
Liabilities:
Total fair value of liabilities				1,615
Significant Unobservable Inputs (Level 3) | Preferred Stock Purchase Right Liability
Liabilities:
Total fair value of liabilities				$ 1,615
[1]	Included as cash and cash equivalents on the condensed consolidated balance sheets.
[2]	Included as cash and cash equivalents on the consolidated balance sheets.
[3]	Included as short-term investments on the consolidated balance sheets.
[4]	Included as short-term investments on the condensed consolidated balance sheets.

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Financial liabilities measured at fair value on recurring basis		$ 0
Measurement at fair value, transfers among Level 1, Level 2 or Level 3		0
Preferred Stock Purchase Right Liability
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in fair value of purchase right liability	$ 555,000	$ 1,600,000	$ 2,300,000

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Assumptions Used to Determine Fair Value of Preferred Stock Purchase Right Liability (Details) - Black-Scholes Option Pricing Model - Preferred Stock Purchase Right Liability	1 Months Ended	12 Months Ended
	Jan. 31, 2021	Dec. 31, 2020
Fair Value of Underlying Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.0611	0.0611
Risk-free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.0007	0.0008
Expected Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.744	0.718
Expected Term (in years)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term (in years)	0 years	29 days
Expected Dividend Yield
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0	0

Investments - Summary of Invest

Investments - Summary of Investments Accounted for Available-for-Sale-Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 40,834	$ 53,323
Available for sale securities, Unrealized losses		(1)
Available for sale securities, Unrealized gains		3
Available for sale securities, Estimated fair value	40,834	53,325
Short-Term Investments | US Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost		38,489
Available for sale securities, Unrealized gains		3
Available for sale securities, Estimated fair value		$ 38,492
Short-Term Investments | US Treasury Securities | Maximum
Schedule Of Available For Sale Securities [Line Items]
Maturity		1 year
Short-Term Investments | US Government Securities
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	10,031
Available for sale securities, Estimated fair value	$ 10,031
Short-Term Investments | US Government Securities | Maximum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year
Short-Term Investments | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 1,517	$ 3,794
Available for sale securities, Unrealized losses		(1)
Available for sale securities, Estimated fair value	$ 1,517	$ 3,793
Short-Term Investments | Corporate Debt Securities | Maximum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year	1 year
Short-Term Investments | Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 27,776	$ 11,040
Available for sale securities, Estimated fair value	$ 27,776	$ 11,040
Short-Term Investments | Commercial Paper | Maximum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year	1 year
Short-Term Investments | Supranational Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities, Amortized cost	$ 1,510
Available for sale securities, Estimated fair value	$ 1,510
Short-Term Investments | Supranational Debt Securities | Maximum
Schedule Of Available For Sale Securities [Line Items]
Maturity	1 year

Investments - Additional Inform

Investments - Additional Information (Details) $ in Millions	Sep. 30, 2021USD ($)Position	Dec. 31, 2020USD ($)Position
Investments Debt And Equity Securities [Abstract]
Available of sale securities, unrealized loss position, Number of positions	2	6
Available for sale securities, gross unrealized loss position | $	$ 3	$ 15.8
Available of sale securities, unrealized loss position, greater than 12 months, Number of positions	0

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment	$ 9,927	$ 2,749
Less accumulated depreciation and amortization	(1,407)	(902)
Property and equipment, net	8,520	1,847
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment	795	795
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment	4,712
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment	2,186	1,380
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment	1,598	165
Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment	61	61
Software
Property Plant And Equipment [Line Items]
Property and equipment	87	70
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment	$ 488	$ 278

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 191,000	$ 139,000	$ 509,000	$ 394,000

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued research and development expenses	$ 6,647	$ 6,649
Accrued compensation	4,711	2,416
Unvested early exercised stock option liability	3,057	2,526
Accrued construction in progress	1,834
Accrued legal	174	194
Other accruals	977	140
Total	$ 17,400	$ 11,925

Asset Acquisitions - Additional

Asset Acquisitions - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2021	Nov. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Asset Acquisitions [Line Items]
In-process research and development			$ 1,680,000	$ 75,000	$ 10,848,000	$ 17,745,000
Asana Merger Agreement
Asset Acquisitions [Line Items]
Upfront payment made		$ 20,000,000
Future development and regulatory milestone cash payments maximum		$ 90,000,000
Additional shares required to issue upon achieving development milestone		3,888,889
In-process research and development			0	$ 0	0	$ 0	$ 50,000,000
Milestones accrued			0		0		$ 0
Asana Merger Agreement | Series B-2 Convertible Preferred Stock
Asset Acquisitions [Line Items]
Shares issued		4,000,000
Value per share		$ 7.50
Total fair value		$ 30,000,000
ELS Purchase Agreement
Asset Acquisitions [Line Items]
Upfront payment made	$ 2,000,000
In-process research and development			$ 0		$ 3,700,000
ELS Purchase Agreement | Common Stock
Asset Acquisitions [Line Items]
Shares issued	500,000
Value per share	$ 3.36
Total fair value	$ 1,700,000

License Agreements - Additional

License Agreements - Additional Information (Details) - USD ($)	1 Months Ended						3 Months Ended		9 Months Ended
	Aug. 31, 2021	May 31, 2021	Jan. 31, 2021	Apr. 30, 2020	Mar. 31, 2020	Feb. 29, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
License Agreements [Line Items]
In-process research and development							$ 1,680,000	$ 75,000	$ 10,848,000	$ 17,745,000
License Agreement | NiKang Therapeutics, Inc.
License Agreements [Line Items]
Upfront payment						$ 5,000,000
Reimbursement of certain initial manufacturing costs						$ 400,000
Payment for US patent application				$ 7,000,000
Accrued development milestone payment							0		0		$ 4,000,000
In-process research and development							0	0	0	12,000,000
Ownership percentage of equity or assets						50.00%
License Agreement | NiKang Therapeutics, Inc. | First Licensed Product | Maximum
License Agreements [Line Items]
Development and regulatory milestone payments obligation						$ 16,000,000
Commercial milestone payments obligation						157,000,000
License Agreement | NiKang Therapeutics, Inc. | Second Licensed Product
License Agreements [Line Items]
Development and regulatory milestone payments obligation						12,000,000
Commercial milestone payments obligation						$ 151,000,000
License Agreement | Katmai Pharmaceuticals, Inc.
License Agreements [Line Items]
Upfront payment					$ 5,700,000
In-process research and development							0	0	0	5,700,000
License Agreement | Katmai Pharmaceuticals, Inc. | Series B-1 Convertible Preferred Stock and Series B-2 Convertible Preferred Stock
License Agreements [Line Items]
Stock issued, value					2,700,000
License Agreement | Katmai Pharmaceuticals, Inc. | Series B-1 Convertible Preferred Stock
License Agreements [Line Items]
Stock issued, value				$ 1,800,000
Stock issued and sold				356,000
License Agreement | Katmai Pharmaceuticals, Inc. | Series B-2 Convertible Preferred Stock
License Agreements [Line Items]
Stock issued, value			$ 900,000
Stock issued and sold			118,666
License Agreement | Katmai Pharmaceuticals, Inc. | Maximum
License Agreements [Line Items]
Development and regulatory milestone payments obligation					26,000,000
Commercial milestone payments obligation					101,000,000
License Agreement | LifeArc
License Agreements [Line Items]
Upfront payment					0
In-process research and development							0	75,000	0	75,000
One-time license payment					75,000
License Agreement | LifeArc | Maximum
License Agreements [Line Items]
Development and regulatory milestone payments obligation					11,000,000
Sales milestone payments obligation					$ 50,000,000
License Agreement | The Regents
License Agreements [Line Items]
Upfront payment		$ 50,000
In-process research and development							$ 1,700,000	$ 0	$ 7,200,000	$ 0
Sales milestone payments obligation		$ 2,000,000
Percentage of third tier sublicensing fees		30.00%
Cash payments in license agreement upon achievement of corporate milestone	$ 1,700,000
License Agreement | The Regents | Common Stock
License Agreements [Line Items]
Stock issued and sold		944,945
License Agreement | The Regents | Maximum
License Agreements [Line Items]
Development and regulatory milestone payments obligation		$ 6,400,000

Stockholders' Deficit - Additio

Stockholders' Deficit - Additional Information (Details) $ / shares in Units, $ in Thousands	Jul. 20, 2021$ / sharesshares	Jul. 09, 2021	Jul. 31, 2021shares	Jan. 31, 2021USD ($)$ / sharesshares	Apr. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2021USD ($)$ / sharesshares	Mar. 31, 2021shares	Sep. 30, 2020USD ($)shares	Jun. 30, 2020USD ($)shares	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2018$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Jun. 30, 2021shares	Feb. 28, 2021shares	Apr. 15, 2020$ / sharesshares	Mar. 31, 2020shares
Class of Stock [Line Items]
Common stock, shares authorized						800,000,000				800,000,000		147,027,681				156,000,000	147,027,681
Common stock, par value | $ / shares						$ 0.0001				$ 0.0001		$ 0.0001					$ 0.0001
Undesignated preferred stock authorized						80,000,000				80,000,000		0
Undesignated preferred stock par value | $ / shares						$ 0.0001				$ 0.0001		$ 0.0001
Proceeds from issuance of convertible preferred stock | $										$ 119,393	$ 136,974
Series B-1 convertible preferred shares converted into common stock		1.2
Preferred stock purchase right liability | $												$ 1,615
Shares issued and sold						121,250,375				121,250,375		25,189,673
Common stock, shares outstanding						118,645,593				118,645,593		21,923,173
Shares of common stock subject to repurchase						303,820				303,820		577,259
Number of shares vested						91,146		91,146		273,439	273,438
Common stock, voting rights										The restricted stock vests 25% one year from the vesting commencement date and monthly thereafter over a three-year period and is subject to repurchase by the Company in the event of any voluntary or involuntary termination of services to the Company prior to vesting.
Common Stock
Class of Stock [Line Items]
Convertible preferred stock converted into shares of common stock						71,263,685
Shares issued and sold						121,250,375	26,129,283	25,552,592	23,358,324	121,250,375	25,552,592	25,189,673		22,629,158	27,300,123			23,358,324
IPO
Class of Stock [Line Items]
Common stock, shares authorized	800,000,000															156,000,000
Undesignated preferred stock authorized	80,000,000
Undesignated preferred stock par value | $ / shares	$ 0.0001
IPO | Common Stock
Class of Stock [Line Items]
Convertible preferred stock converted into shares of common stock	71,263,685		71,263,685
Restricted Stock
Class of Stock [Line Items]
Shares issued													1,458,332
Share price per share | $ / shares													$ 0.0001
Stock vesting period													3 years
Restricted Stock | One Year from the Vesting Commencement Date and Monthly Thereafter Over Three-year Vesting Period
Class of Stock [Line Items]
Stock vesting percentage													25.00%
Series B Agreement
Class of Stock [Line Items]
Purchase agreement termination date					Sep. 30, 2022
Series B-1 convertible preferred shares converted into common stock					0.1
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares issued												38,103,681	38,103,681	38,103,681
Convertible preferred stock, issue price per share | $ / shares													$ 1.667	$ 1.667
Proceeds from issuance of convertible preferred stock | $														$ 63,400
Preferred shares outstanding												38,103,681
Series B-1 Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares issued												27,481,001
Preferred shares outstanding												27,481,001
Series B-1 Convertible Preferred Stock | Series B Agreement
Class of Stock [Line Items]
Convertible preferred stock, shares issued					27,481,001
Convertible preferred stock, issue price per share | $ / shares					$ 5
Proceeds from issuance of convertible preferred stock | $					$ 137,000
Series B-2 Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares issued												4,000,000
Convertible preferred stock, issue price per share | $ / shares				$ 7.50								$ 7.50
Proceeds from issuance of convertible preferred stock | $				$ 119,400
Preferred stock purchase right liability | $						$ 9,000				$ 9,000
Gain (loss) for changes in fair value of convertible preferred stock purchase right liability | $												$ 7,400
Convertible preferred stock, shares issued during period				13,175,191
Convertible preferred stock, additional shares issued				2,756,581
Convertible preferred stock shares issued in connection with asset acquisition												4,000,000
Preferred shares outstanding												4,000,000
Series B-2 Convertible Preferred Stock | Series B Agreement
Class of Stock [Line Items]
Convertible preferred stock, shares issued					13,175,191
Convertible preferred stock, issue price per share | $ / shares					$ 7.50
Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares issued						0				0		69,584,682
Preferred stock purchase right liability | $								$ 1,618	$ 7,355		$ 1,618
Convertible preferred stock, shares issued during period							15,931,772	2,400,000	25,081,001
Preferred shares outstanding						0	85,516,454	65,584,682	63,184,682	0	65,584,682	69,584,682		38,103,681	85,516,454			38,103,681

Stockholders' Deficit - Schedul

Stockholders' Deficit - Schedule of Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
Common stock issuable upon conversion	29,817,827			77,822,703
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred shares authorized				38,103,681
Preferred shares issued				38,103,681				38,103,681	38,103,681
Preferred shares outstanding				38,103,681
Carrying value				$ 63,403
Liquidation preference				$ 63,519
Common stock issuable upon conversion				31,753,064
Series B-1 Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred shares authorized				28,741,400
Preferred shares issued				27,481,001
Preferred shares outstanding				27,481,001
Carrying value				$ 128,002
Liquidation preference				$ 137,405
Common stock issuable upon conversion				22,900,819
Series B-2 Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred shares authorized				30,777,328
Preferred shares issued				4,000,000
Preferred shares outstanding				4,000,000
Carrying value				$ 30,000
Liquidation preference				$ 30,000
Common stock issuable upon conversion				3,333,333
Convertible Preferred Stock
Temporary Equity [Line Items]
Preferred shares authorized	0			97,622,409
Preferred shares issued	0			69,584,682
Preferred shares outstanding	0	85,516,454	85,516,454	69,584,682	65,584,682	63,184,682	38,103,681	38,103,681
Carrying value		$ 340,798	$ 340,798	$ 221,405	$ 191,404	$ 181,050	$ 63,403	$ 63,403
Liquidation preference	$ 0			$ 230,924
Common stock issuable upon conversion	0			57,987,216

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($)	1 Months Ended		2 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2021	Jan. 31, 2021	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance			29,817,827	29,817,827		29,817,827		77,822,703
Share-based compensation, shares subject to repurchase			2,001,823	2,001,823		2,001,823		2,131,510
Stock-based compensation				$ 3,017,000	$ 176,000	$ 5,448,000	$ 390,000
Accrued Expenses and Other Current Liabilities
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, liabilities associated with shares issued with repurchase rights			$ 3,100,000	$ 3,100,000		$ 3,100,000		$ 2,500,000
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, common stock grant in period, term						5 years
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance			13,782,167	13,782,167		13,782,167		6,541,422
Stock vesting period						4 years
Weighted-average grant date fair value of options granted				$ 12.29	$ 0.83	$ 3.96	$ 0.81
Unrecognized compensation cost related to unvested stock option grants			$ 32,300,000	$ 32,300,000		$ 32,300,000
Unrecognized compensation cost expected to be recognized as expense, period						3 years 1 month 9 days
Aggregate fair value of stock options vested				400,000	$ 100,000	$ 1,000,000	$ 200,000
Share-based compensation, options granted that vest based on performance milestone		250,000				8,129,187
Stock Options | Minimum | At the Time Option is Granted
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair market value of common stock						100.00%
Stock Options | Minimum | For Holders of More Than 10% of Company's Total Combined Voting Power of All Classes of Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair market value of common stock						110.00%
Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, plan expiration period						10 years
Performance-based Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation				$ 0		$ 115,000		$ 0
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period									3 years
Restricted stock granted				0	0	0	0		1,795,827
Weighted-average grant date fair value of restricted stock granted									$ 0
Share-based Compensation, common stock shares subject to forfeiture			299,139	299,139		299,139		557,731
Total unrecognized compensation related to unvested restricted stock awards granted			$ 0	$ 0		$ 0
Restricted Stock | One Year from the Vesting Commencement Date and Monthly Thereafter Over Three-year Vesting Period
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting percentage									25.00%
Share-based compensation, vesting rights description						The Company granted 1,795,827 shares of its restricted stock in 2018, which vest 25% one year from the vesting commencement date and monthly thereafter over a three-year period.
Restricted Stock | 25% One Year from Vesting Commencement Date
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period									1 year
Restricted Stock | Monthly Thereafter Over Three-year Vesting Period
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period									3 years
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation, options granted that vest based on performance milestone			0
2021 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance			14,775,660	14,775,660		14,775,660
Shares of common stock, authorized for issuance	15,150,000
Percentage of outstanding common stock maximum	5.00%
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	1,260,000
Unrecognized compensation cost related to unvested stock option grants			$ 2,600,000	$ 2,600,000		$ 2,600,000
Unrecognized compensation cost expected to be recognized as expense, period						1 year 1 month 13 days
Stock-based compensation				278,000		$ 278,000
Share-based payment arrangement, withheld on behalf of employees for future purchase			$ 604,000	$ 604,000		$ 604,000
Offering period	24 months
Purchase period	6 months
Shares issued under ESPP						0
ESPP | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair market value of common stock	85.00%

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Details) - Stock Options $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2021USD ($)$ / sharesshares	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Outstanding at December 31, 2020 | shares	6,541,422	6,541,422
Shares Granted | shares	250,000	8,129,187
Shares Exercised | shares		(696,015)
Shares Canceled | shares		(192,427)
Shares Outstanding at September 30, 2021 | shares		13,782,167	6,541,422
Shares Options exercisable at September 30, 2021 | shares		2,614,566
Weighted-average exercise price, Outstanding at December 31, 2020 | $ / shares	$ 0.98	$ 0.98
Weighted-average exercise price, Granted | $ / shares		5.65
Weighted-average exercise price, Exercised | $ / shares		1.93
Weighted-average exercise price, Canceled | $ / shares		3.70
Weighted-average exercise price, Outstanding at September 30, 2021 | $ / shares		3.65	$ 0.98
Weighted-average exercise price, Options exercisable at September 30, 2021 | $ / shares		$ 1.68
Weighted-average remaining contractual term (years), Outstanding		9 years 18 days	9 years 2 months 23 days
Weighted-average remaining contractual term (years), Options exercisable at September 30, 2021		8 years 6 months
Aggregate intrinsic value, Outstanding at December 31, 2020 | $	$ 15,571	$ 15,571
Aggregate intrinsic value, Exercised | $		2,545
Aggregate intrinsic value, Outstanding at September 30, 2021 | $		242,214	$ 15,571
Aggregate intrinsic value, Options exercisable at September 30, 2021 | $		$ 51,079

Stock-based Compensation - Assu

Stock-based Compensation - Assumptions used to Determine Fair Value of Stock Option Grants (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	0.91%	0.37%	0.59%	0.37%
Risk-free interest rate, maximum	0.97%	0.40%	1.09%	1.22%
Expected volatility, minimum	81.93%	77.58%	81.93%	74.72%
Expected volatility, maximum	84.98%	77.81%	84.98%	77.81%
Expected term (in years)	6 years 29 days		6 years 29 days
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		6 years 7 days		6 years 7 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		6 years 29 days		6 years 3 months

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Stock	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock shares outstanding, Nonvested at December 31, 2020 | shares	557,731
Number of restricted stock shares outstanding, Vested | shares	(258,592)
Number of restricted stock shares outstanding, Nonvested at June 30, 2021 | shares	299,139
Weighted average grant date fair value, Nonvested at December 31, 2020 | $ / shares	$ 0.001
Weighted-average grant date fair value, Vested | $ / shares	0.001
Weighted-average grant date fair value, Nonvested at June 30, 2021 | $ / shares	$ 0.001

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 3,017	$ 176	$ 5,448	$ 390
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	1,665	91	3,080	191
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 1,352	$ 85	$ 2,368	$ 199

Stock-based Compensation - Su_3

Stock-based Compensation - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	29,817,827	77,822,703
Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	0	57,987,216
Conversion of Preferred Stock in Future Issuance (B-2)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	0	10,979,319
Stock Options Issued and Outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	13,782,167	6,541,422
Awards Available for Future Grant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	14,775,660	2,314,746
Shares Available for Purchase Under ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	1,260,000	0

Leases - Additional Information

Leases - Additional Information (Details)	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2021USD ($)ft²	Sep. 30, 2020USD ($)ft²	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)ft²	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)ft²	Dec. 31, 2020USD ($)	Dec. 31, 2018ft²
Lessee Lease Description [Line Items]
Operating leases cancelable expiration dates					2032
Operating leases Noncancelable expiration dates					2022
Operating lease cost			$ 905,000	$ 342,000	$ 1,600,000	$ 1,000,000
Variable lease costs			96,000	94,000	324,000	269,000
Short-term lease costs			$ 30,000	$ 26,000	89,000	67,000
Cash paid for operating leases					$ 803,000	$ 726,000
Operating lease, weighted-average remaining lease term			9 years 4 months 9 days		9 years 4 months 9 days		3 years 1 month 28 days
Operating lease, weighted-average discount rate			7.10%		7.10%		7.80%
Office space leases, in square feet | ft²								16,153
Lease expiration date					May 31, 2024
Operating lease, aggregate monthly payments to lessor			$ 54,174,000		$ 54,174,000
Letter of credit provided to lessor			$ 408,000		$ 408,000		$ 312,000
2020 Lease
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²		59,407		59,407		59,407
Lease commencement month and year		2021-08
Operating lease initial term		10 years 6 months		10 years 6 months		10 years 6 months
Operating lease, aggregate monthly payments to lessor		$ 39,500,000		$ 39,500,000		$ 39,500,000
Tenant improvement allowance		$ 13,400,000
Term for cancellation of lease		84 months
Notice period for cancellation of lease		12 months
Operating lease cancellation payment		$ 1,900,000		1,900,000		1,900,000
2020 Lease | Letter of Credit
Lessee Lease Description [Line Items]
Letter of credit provided to lessor		$ 312,000		$ 312,000		$ 312,000
Line of credit facility, expiration date		Oct. 31, 2031
First Amendment to 2020 Lease
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²	18,421
Operating lease, lease payments to lessor	$ 96,000
Tenant improvement allowance	$ 3,400,000
Term for cancellation of lease	84 months
Operating lease cancellation payment	$ 2,500,000
First Amendment to 2020 Lease | Letter of Credit
Lessee Lease Description [Line Items]
Letter of credit provided to lessor	$ 408,000
California
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²								11,000

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Lease Payments under Operating Leases (Details) $ in Thousands	Sep. 30, 2021USD ($)
Leases [Abstract]
2021 (three months remaining)	$ 270
2022	969
2023	5,963
2024	5,578
2025	5,333
Thereafter	36,061
Total lease payments	54,174
Less: Amount representing interest	(17,167)
Less: Tenant improvement allowance receivable	(16,774)
Operating lease liabilities	$ 20,233

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - Litigation	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Number of litigations filed	0	0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Taxes [Line Items]
Provision for federal income taxes	$ 0	$ 0	$ 0	$ 0
Provision for state income taxes	0	0	0	0
Provision for foreign income taxes	0	0	0	0
Interest or penalties related to income taxes	$ 0	$ 0	$ 0	$ 0

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net loss	$ (46,069)	$ (28,214)	$ (18,017)	$ (10,608)	$ (5,491)	$ (23,658)	$ (92,300)	$ (39,757)
Weighted-average shares of common stock used in computing net loss per share, basic and diluted	99,127,286			21,084,657			48,584,029	20,851,262
Net loss per share, basic and diluted	$ (0.46)			$ (0.50)			$ (1.90)	$ (1.91)

Net Loss Per Share - Anti-dilut

Net Loss Per Share - Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	16,686,041	76,489,476	16,686,041	76,489,476
Conversion of convertible preferred stock in future issuance (B-2)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		10,979,319		10,979,319
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	13,782,167	6,666,515	13,782,167	6,666,515
Restricted Stock Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	602,959	1,503,303	602,959	1,503,303
Options Early Exercised Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	2,001,823	2,686,456	2,001,823	2,686,456
Estimated Shares Purchasable Under the ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	299,092		299,092
Convertible Preferred Stock Issued
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		54,653,883		54,653,883

Retirement Plan - Additional In

Retirement Plan - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Compensation And Retirement Disclosure [Abstract]
Safe harbor contribution percentage			3.00%
Safe harbor contribution expense	$ 146,000	$ 0	$ 378,000	$ 0

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended
	Aug. 31, 2021	Jul. 31, 2021	Sep. 30, 2021
Related Party Transaction [Line Items]
Recovery of stockholder's short-swing profits	$ 553,000
Erasca Foundation
Related Party Transaction [Line Items]
Contribution of common stock			$ 17,497,000
Common Stock | Erasca Foundation
Related Party Transaction [Line Items]
Stock issued		1,093,557	1,093,557
Contribution of common stock		$ 17,500,000