Imago BioSciences (IMGO) 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. 05, 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	Imago BioSciences, Inc.
Entity Central Index Key	0001623715
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity File Number	001-40604
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	45-4915810
Entity Address, Address Line One	329 Oyster Point Blvd.
Entity Address, Address Line Two	3rd Floor
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	415
Local Phone Number	529-5055
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		33,528,718
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	IMGO
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 85,209	$ 19,266
Short-term investments	145,144	57,375
Prepaid expenses and other current assets	4,245	1,181
Total current assets	234,598	77,822
Property and equipment, net	7	8
Long-term investments		19,689
Other long-term assets	2,670	1,414
Total assets	237,275	98,933
Current liabilities:
Accounts payable	1,905	1,379
Accrued and other current liabilities	7,006	3,726
Total current liabilities	8,911	5,105
Commitments and contingencies (Note 6)
Convertible preferred stock, $0.0001 par value; 0 and 180,059,639 shares authorized, as of September 30, 2021 and December 31, 2020, respectively; 0 and 21,435,632 issued and outstanding as of September 30, 2021 and December 31, 2020, respectively; aggregate liquidation preference of $0 and $165,500 as of September 30, 2021 and December 31, 2020, respectively	0	162,612
Stockholders' equity (deficit):
Preferred stock, $0.0001 par value; 10,000,000 and 0 shares authorized as of September 30, 2021, and December 31, 2020, respectively; 0 issued and outstanding as of September 30, 2021, and December 31, 2020, respectively	0	0
Common stock, $0.0001 par value; 300,000,000 and 228,300,000 shares authorized as of September 30, 2021 and December 31, 2020, respectively; 33,457,029 and 1,030,023 shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively	3	0
Additional paid-in capital	326,272	1,561
Accumulated other comprehensive income (loss)	16	(3)
Accumulated deficit	(97,927)	(70,342)
Total stockholders' equity (deficit)	228,364	(68,784)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 237,275	$ 98,933

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Convertible preferred stock, par value per share	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	0	180,059,639
Convertible preferred stock, shares issued	0	21,435,632
Convertible preferred stock, shares outstanding	0	21,435,632
Convertible preferred stock, liquidation preference	$ 0	$ 165,500
Preferred stock, par value per share	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	0
Preferred stock shares issued	0	0
Preferred stock shares outstanding	0	0
Common stock, par value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	228,300,000
Common stock shares issued	33,457,029	1,030,023
Common stock shares outstanding	33,457,029	1,030,023

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (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	$ 8,680	$ 3,576	$ 20,551	$ 10,622
General and administrative	3,040	734	7,159	1,884
Total operating expenses	11,720	4,310	27,710	12,506
Loss from operations	(11,720)	(4,310)	(27,710)	(12,506)
Other income (expense), net:
Interest income	72		241	14
Change in fair value of convertible preferred stock tranche liability				214
Other expense, net	(22)	(6)	(116)	(5)
Total other income, net	50	2	125	223
Net loss	$ (11,670)	$ (4,308)	$ (27,585)	$ (12,283)
Net loss per share, basic and diluted	$ (0.44)	$ (4.23)	$ (2.85)	$ (12.06)
Weighted-average shares used in computing net loss per share, basic and diluted	26,671,511	1,018,119	9,688,747	1,018,119

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (11,670)	$ (4,308)	$ (27,585)	$ (12,283)
Other comprehensive income (loss):
Unrealized (loss) gain on available-for-sale securities	(1)	1	19	7
Comprehensive loss	$ (11,671)	$ (4,307)	$ (27,566)	$ (12,276)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Convertible Preferred Stock	Series B Convertible Preferred Stock	Initial Public Offering	Initial Public OfferingCommon Stock	Initial Public OfferingAdditional Paid-in Capital	Initial Public OfferingConvertible Preferred Stock	Private Placement	Private PlacementCommon Stock	Private PlacementAdditional Paid-in Capital
Temporary equity, beginning balance, shares at Dec. 31, 2019						9,020,460
Temporary equity, beginning balance at Dec. 31, 2019						$ 54,771
Beginning balance, shares at Dec. 31, 2019		1,018,119
Beginning balance at Dec. 31, 2019	$ (51,402)		$ 1,106	$ 1	$ (52,509)
Stock-based compensation	84		84
Other comprehensive income (loss)	8			8
Net loss	(4,245)				(4,245)
Temporary equity, ending balance, shares at Mar. 31, 2020						9,020,460
Temporary equity, ending balance at Mar. 31, 2020						$ 54,771
Ending balance, shares at Mar. 31, 2020		1,018,119
Ending balance at Mar. 31, 2020	(55,555)		1,190	9	(56,754)
Temporary equity, beginning balance, shares at Dec. 31, 2019						9,020,460
Temporary equity, beginning balance at Dec. 31, 2019						$ 54,771
Beginning balance, shares at Dec. 31, 2019		1,018,119
Beginning balance at Dec. 31, 2019	(51,402)		1,106	1	(52,509)
Other comprehensive income (loss)	7
Net loss	(12,283)
Temporary equity, ending balance, shares at Sep. 30, 2020						13,550,391
Temporary equity, ending balance at Sep. 30, 2020						$ 82,910
Ending balance, shares at Sep. 30, 2020		1,018,119
Ending balance at Sep. 30, 2020	(63,389)		1,395	8	(64,792)
Temporary equity, beginning balance, shares at Mar. 31, 2020						9,020,460
Temporary equity, beginning balance at Mar. 31, 2020						$ 54,771
Beginning balance, shares at Mar. 31, 2020		1,018,119
Beginning balance at Mar. 31, 2020	(55,555)		1,190	9	(56,754)
Stock-based compensation	98		98
Other comprehensive income (loss)	(2)			(2)
Net loss	(3,730)				(3,730)
Temporary equity, ending balance, shares at Jun. 30, 2020						9,020,460
Temporary equity, ending balance at Jun. 30, 2020						$ 54,771
Ending balance, shares at Jun. 30, 2020		1,018,119
Ending balance at Jun. 30, 2020	(59,189)		1,288	7	(60,484)
Issuance of Series B convertible preferred stock, net of issuance costs of $17 and the settlement of preferred stock tranche liability of $2,281, shares							4,529,931
Issuance of Series B convertible preferred stock, net of issuance costs of $17 and the settlement of preferred stock tranche liability of $2,281							$ 28,139
Stock-based compensation	107		107
Other comprehensive income (loss)	1			1
Net loss	(4,308)				(4,308)
Temporary equity, ending balance, shares at Sep. 30, 2020						13,550,391
Temporary equity, ending balance at Sep. 30, 2020						$ 82,910
Ending balance, shares at Sep. 30, 2020		1,018,119
Ending balance at Sep. 30, 2020	$ (63,389)		1,395	8	(64,792)
Temporary equity, beginning balance, shares at Dec. 31, 2020	21,435,632					21,435,632	7,878,135
Temporary equity, beginning balance at Dec. 31, 2020	$ 162,612					$ 162,612	$ 44,895
Beginning balance, shares at Dec. 31, 2020	1,030,023	1,030,023
Beginning balance at Dec. 31, 2020	$ (68,784)		1,561	(3)	(70,342)
Stock-based compensation	319		319
Other comprehensive income (loss)	12			12
Net loss	(7,109)				(7,109)
Temporary equity, ending balance, shares at Mar. 31, 2021						21,435,632
Temporary equity, ending balance at Mar. 31, 2021						$ 162,612
Ending balance, shares at Mar. 31, 2021		1,030,023
Ending balance at Mar. 31, 2021	$ (75,562)		1,880	9	(77,451)
Temporary equity, beginning balance, shares at Dec. 31, 2020	21,435,632					21,435,632	7,878,135
Temporary equity, beginning balance at Dec. 31, 2020	$ 162,612					$ 162,612	$ 44,895
Beginning balance, shares at Dec. 31, 2020	1,030,023	1,030,023
Beginning balance at Dec. 31, 2020	$ (68,784)		1,561	(3)	(70,342)
Exercise of stock options, shares	0
Other comprehensive income (loss)	$ 19
Net loss	$ (27,585)
Temporary equity, ending balance, shares at Sep. 30, 2021	0
Temporary equity, ending balance at Sep. 30, 2021	$ 0
Ending balance, shares at Sep. 30, 2021	33,457,029	33,457,029
Ending balance at Sep. 30, 2021	$ 228,364	$ 3	326,272	16	(97,927)
Temporary equity, beginning balance, shares at Mar. 31, 2021						21,435,632
Temporary equity, beginning balance at Mar. 31, 2021						$ 162,612
Beginning balance, shares at Mar. 31, 2021		1,030,023
Beginning balance at Mar. 31, 2021	(75,562)		1,880	9	(77,451)
Exercise of stock options, shares		57,036
Exercise of stock options	107		107
Stock-based compensation	434		434
Other comprehensive income (loss)	8			8
Net loss	(8,806)				(8,806)
Temporary equity, ending balance, shares at Jun. 30, 2021						21,435,632
Temporary equity, ending balance at Jun. 30, 2021						$ 162,612
Ending balance, shares at Jun. 30, 2021		1,087,059
Ending balance at Jun. 30, 2021	(83,819)		2,421	17	(86,257)
Conversion of convertible preferred stock to common stock upon initial public offering, shares									21,435,632		(21,435,632)
Conversion of convertible preferred stock to common stock upon initial public offering								$ 162,612	$ 2	$ 162,610	$ (162,612)
Issuance of common stock, shares									9,660,000				1,250,000
Issuance of common stock								$ 140,486	$ 1	$ 140,485		$ 20,000		$ 20,000
Exercise of stock options, shares		24,338
Exercise of stock options	93		93
Stock-based compensation	663		663
Other comprehensive income (loss)	(1)			(1)
Net loss	$ (11,670)				(11,670)
Temporary equity, ending balance, shares at Sep. 30, 2021	0
Temporary equity, ending balance at Sep. 30, 2021	$ 0
Ending balance, shares at Sep. 30, 2021	33,457,029	33,457,029
Ending balance at Sep. 30, 2021	$ 228,364	$ 3	$ 326,272	$ 16	$ (97,927)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Settlement of preferred stock tranche liability		$ 2,281
Initial Public Offering | Common Stock
Stock issuance costs	$ 3,255
Series B Convertible Preferred Stock
Temporary equity, stock issuance costs		$ 17

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (27,585)	$ (12,283)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of premium and discounts on available-for-sale investments	124	(4)
Depreciation and amortization	3
Change in fair value of convertible preferred stock tranche liability		(214)
Stock-based compensation	1,416	289
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,980)	(419)
Other long-term assets	(1,231)	(1,452)
Accounts payable	501	(335)
Accrued expenses and other current liabilities	3,280	2,328
Net cash used in operating activities	(26,472)	(12,090)
Cash flows from investing activities:
Purchases of property and equipment	(2)	(4)
Purchases of available-for-sale investments	(131,088)	(13,018)
Proceeds from maturities of available-for-sale investments	62,903	2,750
Net cash used in investing activities	(68,187)	(10,272)
Cash flows from financing activities:
Proceeds from exercise of stock options	116
Payments of offering costs related to initial public offering	(3,255)
Proceeds from issuance of Series B convertible preferred stock, net of issuance costs		25,858
Net cash provided by financing activities	160,602	25,858
Net increase in cash and cash equivalents	65,943	3,496
Cash and cash equivalents at beginning of period	19,266	4,961
Cash and cash equivalents at end of period	85,209	8,457
Supplemental cash flow disclosure:
Cash paid for taxes	61	11
Supplemental disclosure of non-cash investing and financing activities:
Other long term assets in accounts payable	25
Proceeds from exercise of stock options in prepaid expenses and other current assets	84
Settlement of Convertible preferred stock liability in connection with the issuance of Series B convertible preferred stock		$ 2,281
Conversion of convertible preferred stock to common stock upon initial public offering	162,612
IPO
Cash flows from financing activities:
Proceeds from issuance of common stock	143,741
Private Placement
Cash flows from financing activities:
Proceeds from issuance of common stock	$ 20,000

Organization and Description of

Organization and Description of the Business	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of the Business	1. Organization and Description of the Business Description of the Business Imago BioSciences, Inc. (“Imago” or the “Company”) was incorporated on March 28, 2012 as a Delaware corporation and is headquartered in South San Francisco, California. The Company is a clinical-stage biopharmaceutical company discovering and developing small molecule product candidates that target lysine-specific demethylase 1 (“LSD1”), an enzyme that plays a central role in the production of blood cells in the bone marrow. The Company is focused on improving the quality of life of patients with cancer and bone marrow diseases in addition to prolonging their lives. The Company’s lead product candidate is bomedemstat for the treatment of myeloproliferative neoplasms (“MPNs”), a family of related, chronic cancers of the bone marrow. The three most common MPNs are myelofibrosis (“MF”), essential thrombocythemia (“ET”) and polycythemia vera ("PV"). The Company is pursuing the development of bomedemstat as a potentially disease-modifying therapy in ET and MF to address the limitations of currently approved therapies. The Company is currently enrolling patients in two Phase 2 clinical trials of bomedemstat for the treatment of ET and MF. Initial public offering On July 15, 2021, the Company’s registration statement on Form S-1 (File No. 333-257419) (the “Prospectus”) relating to its initial public offering (the “IPO”) of common stock became effective. The IPO closed on July 20, 2021 at which time the Company issued an aggregate of 8,400,000 shares of its common stock at a price of $ 16.00 per share. Within 30 days following the close, 1,260,000 shares were issued in connection with the full exercise by the underwriters of their option to purchase additional shares of common stock. In connection with the completion of its IPO, on July 20, 2021 the Company’s certificate of incorporation was amended and restated to provide for 300,000,000 authorized shares of common stock with a par value of $ 0.0001 per share and 10,000,000 authorized shares of preferred stock with a par value of $ 0.0001 per share. The Company received net proceeds of approximately $ 143.7 million from the IPO, after deducting underwriting discounts and commissions. Concurrent with the IPO, the Company issued 1,250,000 shares of common stock in a private placement (the “Private Placement”) for net proceeds of $ 20.0 million. Immediately prior to the completion of the IPO, all shares of convertible preferred stock then outstanding were converted into 21,435,632 shares of common stock. Liquidity and capital resources The Company has incurred net losses and cash out flows from operations since inception and as of September 30, 2021 has an accumulated deficit of $ 97.9 million. As of September 30, 2021, the Company had cash, cash equivalents and short-term investments of $ 230.4 million, which are available to fund future operations. Management expects to incur additional losses in the future to conduct research and development and recognizes the need to raise capital to fully implement its business plan. The Company has historically financed its operations primarily with the proceeds from the issuance of its convertible preferred stock and to a lesser extent debt financing. The Company may raise additional capital through additional equity financings, debt financings or other sources. Based on projected activities, management believes that its existing cash, cash equivalents and short-term investments as of September 30, 2021 and the proceeds from the IPO and private placement will be sufficient to support operations for at least the next 12 months following issuance of these unaudited condensed consolidated financial statements. Reverse stock split On July 13, 2021, the Company effected a reverse stock split of the Company’s common stock on an 8.4 -for-1 basis (the “Reverse Stock Split”) . In connection with the Reverse Stock Split, all common stock and convertible preferred stock share and per share amounts for all periods presented in these unaudited condensed consolidated financial statements have been retroactively adjusted, to reflect this Reverse Stock Split. Authorized shares and par values were not adjusted. Coronavirus pandemic On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus originating in Wuhan, China (the “COVID-19 outbreak”) and the risks to the international community as the virus spreads globally beyond its point of origin. In March 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. The full impact of the COVID-19 outbreak continues to evolve as of the date of these unaudited condensed consolidated financial statements. As such, it is uncertain as to the full magnitude that the pandemic will have on the Company’s financial condition, liquidity, and future results of operations. Management is actively monitoring the global situation on its financial condition, liquidity, operations, suppliers, industry, and workforce. Given the daily evolution of the COVID-19 outbreak and the global responses to curb its spread, the Company is not able to estimate the effects of the COVID-19 outbreak on its results of operations, financial condition, or liquidity. Although the Company cannot estimate the length or gravity of the impact of the COVID-19 outbreak at this time, if the pandemic continues, it may have a material adverse effect on the Company’s results of future operations, financial position, and liquidity in 2021.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated. Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the unaudited condensed consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying unaudited condensed consolidated financial statements include, but are not limited to, certain accrued liabilities for research and development activities, valuation of deferred tax assets, the fair values of common and convertible preferred stock, the fair value of stock options and the fair value of the convertible preferred stock tranche liability. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates. Unaudited Condensed Consolidated Financial Statements The unaudited condensed consolidated balance sheet as of September 30, 2021, and the interim condensed consolidated statements of operations, comprehensive loss, and convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2021 and 2020 and interim condensed consolidated statements cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for the fair statement of the Company’s financial position, results of operations and cash flows for the interim periods presented. The financial data and the other financial information disclosed in these notes to the unaudited condensed consolidated financial statements related to the three and nine-month periods are also unaudited. The condensed results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2020 included herein was derived from the audited consolidated financial statements as of that date. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements included in the P rospectus dated July 16, 2021 that forms a part of the Company’s Registration Statement on Form S-1 (File No. 333-257419), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended. Deferred Offering Costs Deferred offering costs, consisting of legal, accounting, audit and filing fees relating to an IPO, are capitalized. In July 2021, upon the closing of the IPO, all deferred offering costs which were included in other long-term assets in the accompanying condensed consolidated balance sheets were offset against the Company’s IPO proceeds. Convertible Preferred Stock Tranche Liability The Company’s obligation to issue additional shares of its Series B convertible preferred stock at a fixed price in a future closing represents a freestanding financial instrument that is accounted for as a liability. The liability is measured at fair value from the original issuance date of its Series B convertible preferred stock in March 2019 and is subject to remeasurement at each reporting period with changes in fair value recognized in the condensed consolidated statements of operations until settlement or extinguishment. The convertible preferred stock tranche liability was settled on the closing of the Company’s Series B convertible preferred stock financing in July 2020. Research and Development Expenses Research and development costs are expensed as incurred. Research and development costs consist of salaries, benefits, and other personnel related costs, including stock-based compensation, laboratory supplies, clinical studies and related clinical manufacturing costs, fees paid to other entities to conduct certain research and development activities on the Company’s behalf, as well as allocated facility and other related costs. 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. The Company estimates preclinical and clinical study research expenses based on the services performed, pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical and clinical studies and research services on its behalf. The Company records the costs of research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued and other current liabilities in the condensed consolidated balance sheets. These costs are a component of the Company’s research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers under the service agreements. The Company makes significant judgments and estimates in determining the accrued and other current liabilities balance. As actual costs become known, the Company adjusts its accrued expenses. The Company has not experienced any material differences between accrued costs and actual costs incurred. However, the status and timing of actual services performed may vary from the Company’s estimates, resulting in adjustments to expense in future periods. Changes in these estimates that result in material changes to the Company’s accrued costs could materially affect the Company’s results of operations. Stock-Based Compensation Stock-based compensation is measured at the grant date for all equity awards granted to employees and non-employees based on the fair value of the awards, including stock options and restricted shares. The Company estimates the fair value of stock-based awards on the date of grant using the Black-Scholes option-pricing model. For stock-based awards that vest subject to the satisfaction of a service requirement, the expense is recognized using the straight-line method over the requisite service period, which is generally the vesting period. Forfeitures are accounted for when they occur. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of the Company’s common stock outstanding for the period, without consideration for potential dilutive shares of common stock. As the Company is in a loss position for the periods presented, diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive. Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ equity (deficit) that are excluded from net loss. The Company’s comprehensive loss is comprised of unrealized gains and losses on the Company’s available-for-sale investments. Recently Adopted Accounting Pronouncements In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-15 , Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (a consensus of the FASB Emerging Issues Task Force) (“ASU 2018-15”). The ASU clarified that implementation, setup and other upfront costs related to cloud computing agreements (“CCA”) should be accounted for under ASC 350-40. ASU 2018-15 requires companies to capitalize certain costs incurred when purchasing a CCA that is a service. Under the new guidance, companies should apply the same criteria for capitalizing implementation costs in a CCA service as they would for internal-use software. The capitalized implementation costs should be generally expensed over the term of the service agreement and the related assets should be assessed for impairment using the same model applied to long-lived assets. As an emerging growth company, this new standard is effective for annual periods beginning after December 15, 2020. T he Company adopted this standard prospectively on January 1, 2021 . The adoption did no t have a material impact on the Company’s consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments— Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which replaces the existing incurred loss impairment model with an expected credit loss model and requires a financial asset measured at amortized cost to be presented at the net amount expected to be collected. As an emerging growth company, this new standard is effective for the Company in the fiscal year beginning January 1, 2023 and must be adopted using a modified retrospective approach, with certain exceptions. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify the accounting for income taxes. The guidance eliminates certain exceptions to the approach for intra period tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. As an emerging growth company, this new standard is effective for the Company for fiscal year beginning January 1, 2022. The Company is evaluating the impact of this standard on its consolidated financial statements and related disclosures.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines fair value based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels:  Level 1 Inputs: Unadjusted quoted prices in active markets for identical assets or liabilities accessible to the reporting entity at the measurement date.  Level 2 Inputs: Other than quoted prices included in Level 1 inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the asset or liability.  Level 3 Inputs: Unobservable inputs for the asset or liability used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at measurement date. Fair value accounting is applied for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis (at least annually). As of September 30, 2021 and December 31, 2020, the carrying amount of prepaid expenses and other current assets, accounts payable and accrued liabilities approximated their estimate fair value due to their relatively short maturities. The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values: September 30, 2021 Level 1 Level 2 Level 3 Fair Value (in thousands) Assets: Money market funds $ 13,627 $ — $ — $ 13,627 Corporate bonds — 3,434 — 3,434 Commercial paper — 196,107 — 196,107 U.S. treasury securities — 16,073 — 16,073 Total financial assets $ 13,627 $ 215,614 $ — $ 229,241 December 31, 2020 Level 1 Level 2 Level 3 Fair Value (in thousands) Assets: Money market funds $ 11,938 $ — $ — $ 11,938 Corporate bonds — 5,671 — 5,671 Commercial paper — 57,195 — 57,195 U.S. treasury securities — 20,196 — 20,196 Total financial assets $ 11,938 $ 83,062 $ — $ 95,000 Money market funds are highly liquid investments and are actively traded. The pricing information on the Company’s money market funds is readily available and can be independently validated as of the measurement date. This approach results in the classification of these securities as Level 1 of the fair value hierarchy. The Company’s short-term investments are classified as cash equivalents if their original maturities are less than three months. The Company’s short-term investments are considered Level 2 financial instruments as their fair values are determined using inputs that are observable in the market or can be derived principally from recently executed transactions, cash flow models with yield curves, and benchmark securities. There were no transfers in or out of Level 3 of the fair value hierarchy during the periods presented. Convertible Preferred Stock Tranche Liability The Company’s convertible preferred stock tranche liability was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. In determining the fair value of the convertible preferred stock tranche liability, the Company used the Hybrid Tranche Model pricing model to estimate the fair value using unobservable inputs. On the closing of the Company’s Series B convertible preferred stock financing in July 2020, the convertible preferred stock tranche liability was settled and recorded to Series B convertible preferred stock. Accordingly, there is no convertible preferred stock tranche liability as of September 30, 2021 and December 31, 2020. A summary of the significant unobservable inputs used in measuring the Company’s convertible preferred stock tranche liability as of September 30, 2020 is as follows: July 2, 2020 Time to liquidity (years) 0.01 Probability of second closing 100 % Discount rate 20 % The following table provides a summary of changes in the estimated fair value of the Company’s convertible preferred stock tranche liability measured on a recurring basis using significant Level 3 inputs: Nine Months Ended 2020 (in thousands) Beginning balance December 31, 2019 $ 2,495 Change in fair value $ ( 214 ) Settlement of convertible preferred stock tranche liability ( 2,281 ) Ending balance September 30, 2020 $ —

Investments

Investments	9 Months Ended
	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Investments	4. Investments The following tables summarize the fair value and amortized cost of the Company’s available-for-sale debt securities by major security type: September 30, 2021 Amortized Gross Gross Aggregate (in thousands) Assets: Money market funds $ 13,627 $ — $ — $ 13,627 Corporate bonds 3,434 — — 3,434 Commercial paper 196,096 13 ( 2 ) 196,107 U.S. treasury securities 16,068 5 — 16,073 Total financial assets $ 229,225 $ 18 $ ( 2 ) $ 229,241 December 31, 2020 Amortized Gross Gross Aggregate (in thousands) Assets: Money market funds $ 11,938 $ — $ — $ 11,938 Corporate bonds 5,672 1 ( 2 ) 5,671 Commercial paper 57,197 3 ( 5 ) 57,195 U.S. treasury securities 20,196 2 ( 2 ) 20,196 Total financial assets $ 95,003 $ 6 $ ( 9 ) $ 95,000 The following table summarizes the classification of the Company’s available-for-sale debt securities on the condensed consolidated balance sheets: September 30, December 31, 2021 2020 (in thousands) Cash equivalents $ 84,097 $ 17,936 Short-term investments 145,144 57,375 Long-term investments — 19,689 Total cash equivalents and investments $ 229,241 $ 95,000 The following table summarizes the fair values of the Company’s available-for-sale debt securities by contractual maturity: September 30, December 31, 2021 2020 (in thousands) Within one year $ 229,241 $ 75,311 After one year through two years — 19,689 Total cash equivalents and investments $ 229,241 $ 95,000 There were no impairments of available-for-sale debt securities considered “other-than-temporary” during the nine months ended September 30, 2021 as it was more likely than not the Company would hold the securities until maturity or a recovery of the cost basis.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2021
Payables and Accruals [Abstract]
Balance Sheet Components	5. Balance Sheet Components Accrued and Other Current Liabilities Accrued and other current liabilities consist of the following: September 30, December 31, 2021 2020 (in thousands) Accrued research and development $ 4,911 $ 2,670 Compensation and related benefits 1,585 854 Accrued professional service expenses 252 — Other 258 202 Total accrued and other current liabilities $ 7,006 $ 3,726

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Operating Leases As of September 30, 2021 and December 31, 2020, the Company has two cancellable operating lease agreements with lease terms of less than 12 months. For the three months ended September 30, 2021 and 2020, rent expense was $ 21,000 and $ 28,000 , respectively. For the nine months ended September 30, 2021 and 2020, rent expense was $ 71,000 and $ 76,000 , respectively. Guarantees and Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of September 30, 2021 and December 31, 2020, the Company does not have any material indemnification claims that were probable or reasonably possible and, consequently, has not recorded related liabilities.

Equity

Equity	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Equity	7. Equity Convertible Preferred Stock Convertible preferred stock at December 31, 2020 consisted of the following: Shares Shares Issued and Outstanding Net Carrying Value Liquidation (in thousands, except shares) Convertible Preferred Stock Series A 47,647,051 5,672,256 $ 38,015 $ 40,500 Series B 66,176,463 7,878,135 44,895 45,000 Series C 66,236,125 7,885,241 79,702 80,000 Total 180,059,639 21,435,632 $ 162,612 $ 165,500 The Company classifies its convertible preferred stock outside of total stockholders’ equity (deficit) because, in the event of certain “liquidation events” that are not solely within the control of the Company (including a merger, acquisition or sale of all or substantially all of the Company’s assets), the shares would become redeemable at the option of the holders. The Company did not adjust the carrying values of the convertible preferred stock to the deemed liquidation values of such shares since a liquidation event as of December 31, 2020 was not probable of occurring. Upon completion of the Company’s IPO in July 2021, all outstanding shares of convertible preferred stock were converted into 21,435,632 shares of common stock. Common Stock The holders of the Company’s common stock have one vote for each share of common stock. Common stockholders are entitled to dividends when, as, and if declared by the board of directors, subject to the prior rights of the convertible preferred stockholders. The holders have no preemptive or other subscription rights and there is no redemption or sinking fund provisions with respect to such shares. As of September 30, 2021, no such dividends were declared or accrued. The Company reserved the following shares of common stock, on an as-if converted basis, for issuance as follows: September 30, December 31, 2021 2020 Conversion of outstanding shares of convertible preferred stock — 21,435,632 Options outstanding under the 2021 Equity Incentive plan 3,117,338 1,729,843 Options available for future grant 3,659,419 1,678,228 Total 6,776,757 24,843,703

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation 2012 Equity Incentive Plan In October 2012, the Company adopted the 2012 Equity Incentive Plan (the “2012 Plan”) under which 238,095 shares of the Company’s common stock were initially reserved for issuance to employees, directors and consultants. 2021 Equity Incentive Plan In July 2021, the Company adopted the 2021 Incentive Award Plan, (the “2021 Plan”) which became effective in connection with the IPO. As a result of the 2021 Plan, the Company may not grant any additional awards under the 2012 Plan. The 2012 Plan will continue to govern outstanding equity awards granted thereunder. Under the terms of the 2021 Plan, the Company may grant stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance bonus awards, performance stock unit awards, dividend equivalents awards or other stock or cash based awards to individuals who are then employees, consultants or directors of the Company. Under the terms of the Plan, options may be granted at an exercise price not less than fair market value. For employees holding more than 10 % of the voting rights of all classes of stock, the exercise prices for incentive and non-statutory stock options may not be less than 110 % of fair market value, as determined by the Board of Directors. The terms of options granted under the 2021 Plan may not exceed ten years . The vesting schedule of newly issued option grants is generally four years . The Company initially reserved 3,450,000 shares of common stock for issuance under the 2021 Plan. The number of shares initially reserved will be increased by (i) any shares available for issuance under the 2012 Plan as of the day before the IPO, (ii) any shares that are subject to the 2012 Plan that become available for issuance under the 2012 Plan and (iii) the annual increase on January 1 of each year, beginning January 1, 2022 , and continuing through and including January 1, 2031 , by 5 % of the shares of common stock outstanding on the last day of the immediately preceding fiscal year, or a lesser number of shares determined by the Company's board of directors. As of September 30, 2021, there were 3,659,419 shares available for issuance under the 2021 Plan. 2021 Employee Stock Purchase Plan In July 2021, the Company adopted the Employee Stock Purchase Plan, (the “ESPP”), which became effective in connection with the IPO. The purpose of the ESPP is to assist employees of the Company in acquiring a stock ownership interest in the Company, and to help such employees provide for their future security and to encourage them to remain in the employment of the Company. The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the Code. The compensation committee of the board of directors will administer the Company’s ESPP. The maximum aggregate number of shares of common stock that may be issued pursuant to the exercise of purchase rights under the Company’s ESPP that are granted to employees is 4,703,469 shares. Additionally, the number of shares of common stock reserved for issuance under the Company’s ESPP will increase automatically each year, beginning on January 1, 2022 , and continuing through and including January 1, 2031 , by 1 % of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number as determined by the board of directors. Shares subject to purchase rights granted under the Company’s ESPP that terminate without having been exercised in full will not reduce the number of shares available for issuance under the Company’s ESPP. As of September 30, 2021, the Company has reserved 350,000 shares of common stock under the ESPP. There were no shares issued under the ESPP during the three months ended September 30, 2021. Stock Option Activity Stock option activity under the 2012 and 2021 Plan was as follows: Options Available for Grant Number of Options Outstanding Weighted-Average Exercise Price Per Share Weighted-Average Aggregate Intrinsic Value (in thousands) Outstanding as of January 1, 2021 1,678,228 1,729,843 $ 2.08 7.75 $ 3,666 Authorized 3,450,000 — — Share rounding difference as a result of the 60 — — Options granted ( 1,872,306 ) 1,872,306 5.84 Options exercised — ( 81,374 ) 2.46 Options cancelled 403,437 ( 403,437 ) 3.30 Outstanding as of September 30, 2021 3,659,419 3,117,338 $ 4.19 8.00 $ 49,387 Exercisable as of September 30, 2021 1,288,031 $ 2.64 6.25 $ 22,404 The aggregate intrinsic values of options outstanding and exercisable were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock of $ 20.03 as of September 30, 2021. The total intrinsic value of options exercised during the three and nine months ended September 30, 2021 was $ 0.4 million and $ 0.7 million, respectively. There were no options exercised during the nine months ended September 30, 2020. The intrinsic value is the difference between the fair value of Company’s common stock at the time of exercise and the exercise price of the stock option. The weighted-average grant-date fair value per share for stock options granted during the three months ended September 30, 2021 and 2020 was $ 9.66 and $ 1.29 , respectively. The weighted-average grant-date fair value per share for stock options granted during the nine months ended September 30, 2021 and 2020 was $ 3.71 and $ 1.20 , respectively. Determining Fair Value The estimated grant-date fair value of the Company’s stock-based awards was calculated using the Black-Scholes option pricing model, based on the following assumptions: Three Months Ended Nine Months Ended, 2021 2020 2021 2020 Expected term (in years) 5.8 - 6.1 6.0 5.8 - 6.1 6.0 – 6.1 Expected volatility 66.0 % - 66.7 % 70.4 % 66.0 % - 69.9 % 67.1 % - 70.4 % Risk-free interest rate 0.9 % - 1.0 % 0.4 % 0.6 % - 1.1 % 0.4 % - 1.7 % Expected dividend yield —% —% —% —% Each of these inputs is subjective and generally requires significant judgment. Expected Term —The expected term represents the period that the Company’s stock-based awards are expected to be outstanding and is determined using the simplified method, which is based on the mid-point between the contractual term and vesting period. Volatility —The Company determines volatility based on the historical volatilities of comparable publicly traded life science companies over a period equal to the expected term because it does not have sufficient trading history for its common stock price. The comparable companies were chosen based on the similar size, stage in the life cycle, or area of specialty. The Company will continue to apply this process until a sufficient amount of historical information regarding volatility on its own stock becomes available. Risk-Free Interest Rate —The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Dividend Yield —The Company has never paid and has no plans to pay any dividends on its common stock. Therefore, the Company has used an expected dividend yield of zero . Stock-Based Compensation Total stock-based compensation recognized in the condensed consolidated statements of operations is as follows: Three Months Ended September 30, Nine Months Ended 2021 2020 2021 2020 (in thousands) Research and development $ 206 $ 35 $ 394 $ 98 General and administrative 457 72 1,022 191 Total stock-based compensation expense $ 663 $ 107 $ 1,416 $ 289 As of September 30, 2021, total unrecognized stock-based compensation expense is approximately $ 6.1 million, related to unvested stock options to be recognized over the remaining weighted-average vesting period of 3.0 years.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes For the nine months ended September 30, 2021 and 2020, the Company did no t record any income tax expense. The U.S. federal and state deferred tax assets generated from the Company’s net operating losses have been fully reserved, as the Company believes it is not more likely than not that the benefit will be realized.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	10. Net Loss Per Share The following potentially dilutive shares, including all outstanding stock options, were not included in the calculation of diluted shares outstanding for the period presented as the effect would have been anti-dilutive: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Convertible preferred stock — 13,550,391 — 13,550,391 Outstanding stock options 3,117,338 1,708,416 3,117,338 1,708,416 Total 3,117,338 15,258,807 3,117,338 15,258,807

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the unaudited condensed consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying unaudited condensed consolidated financial statements include, but are not limited to, certain accrued liabilities for research and development activities, valuation of deferred tax assets, the fair values of common and convertible preferred stock, the fair value of stock options and the fair value of the convertible preferred stock tranche liability. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates.
Unaudited Condensed Consolidated Financial Statements	Unaudited Condensed Consolidated Financial Statements The unaudited condensed consolidated balance sheet as of September 30, 2021, and the interim condensed consolidated statements of operations, comprehensive loss, and convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2021 and 2020 and interim condensed consolidated statements cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for the fair statement of the Company’s financial position, results of operations and cash flows for the interim periods presented. The financial data and the other financial information disclosed in these notes to the unaudited condensed consolidated financial statements related to the three and nine-month periods are also unaudited. The condensed results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2020 included herein was derived from the audited consolidated financial statements as of that date. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements included in the P rospectus dated July 16, 2021 that forms a part of the Company’s Registration Statement on Form S-1 (File No. 333-257419), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, consisting of legal, accounting, audit and filing fees relating to an IPO, are capitalized. In July 2021, upon the closing of the IPO, all deferred offering costs which were included in other long-term assets in the accompanying condensed consolidated balance sheets were offset against the Company’s IPO proceeds.
Convertible Preferred Stock Tranche Liability	Convertible Preferred Stock Tranche Liability The Company’s obligation to issue additional shares of its Series B convertible preferred stock at a fixed price in a future closing represents a freestanding financial instrument that is accounted for as a liability. The liability is measured at fair value from the original issuance date of its Series B convertible preferred stock in March 2019 and is subject to remeasurement at each reporting period with changes in fair value recognized in the condensed consolidated statements of operations until settlement or extinguishment. The convertible preferred stock tranche liability was settled on the closing of the Company’s Series B convertible preferred stock financing in July 2020.
Research and Development Expenses	Research and Development Expenses Research and development costs are expensed as incurred. Research and development costs consist of salaries, benefits, and other personnel related costs, including stock-based compensation, laboratory supplies, clinical studies and related clinical manufacturing costs, fees paid to other entities to conduct certain research and development activities on the Company’s behalf, as well as allocated facility and other related costs. 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. The Company estimates preclinical and clinical study research expenses based on the services performed, pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical and clinical studies and research services on its behalf. The Company records the costs of research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued and other current liabilities in the condensed consolidated balance sheets. These costs are a component of the Company’s research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers under the service agreements. The Company makes significant judgments and estimates in determining the accrued and other current liabilities balance. As actual costs become known, the Company adjusts its accrued expenses. The Company has not experienced any material differences between accrued costs and actual costs incurred. However, the status and timing of actual services performed may vary from the Company’s estimates, resulting in adjustments to expense in future periods. Changes in these estimates that result in material changes to the Company’s accrued costs could materially affect the Company’s results of operations.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation is measured at the grant date for all equity awards granted to employees and non-employees based on the fair value of the awards, including stock options and restricted shares. The Company estimates the fair value of stock-based awards on the date of grant using the Black-Scholes option-pricing model. For stock-based awards that vest subject to the satisfaction of a service requirement, the expense is recognized using the straight-line method over the requisite service period, which is generally the vesting period. Forfeitures are accounted for when they occur.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of the Company’s common stock outstanding for the period, without consideration for potential dilutive shares of common stock. As the Company is in a loss position for the periods presented, diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ equity (deficit) that are excluded from net loss. The Company’s comprehensive loss is comprised of unrealized gains and losses on the Company’s available-for-sale investments.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-15 , Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (a consensus of the FASB Emerging Issues Task Force) (“ASU 2018-15”). The ASU clarified that implementation, setup and other upfront costs related to cloud computing agreements (“CCA”) should be accounted for under ASC 350-40. ASU 2018-15 requires companies to capitalize certain costs incurred when purchasing a CCA that is a service. Under the new guidance, companies should apply the same criteria for capitalizing implementation costs in a CCA service as they would for internal-use software. The capitalized implementation costs should be generally expensed over the term of the service agreement and the related assets should be assessed for impairment using the same model applied to long-lived assets. As an emerging growth company, this new standard is effective for annual periods beginning after December 15, 2020. T he Company adopted this standard prospectively on January 1, 2021 . The adoption did no t have a material impact on the Company’s consolidated financial statements.
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments— Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which replaces the existing incurred loss impairment model with an expected credit loss model and requires a financial asset measured at amortized cost to be presented at the net amount expected to be collected. As an emerging growth company, this new standard is effective for the Company in the fiscal year beginning January 1, 2023 and must be adopted using a modified retrospective approach, with certain exceptions. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify the accounting for income taxes. The guidance eliminates certain exceptions to the approach for intra period tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. As an emerging growth company, this new standard is effective for the Company for fiscal year beginning January 1, 2022. The Company is evaluating the impact of this standard on its consolidated financial statements and related disclosures.

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 present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values: September 30, 2021 Level 1 Level 2 Level 3 Fair Value (in thousands) Assets: Money market funds $ 13,627 $ — $ — $ 13,627 Corporate bonds — 3,434 — 3,434 Commercial paper — 196,107 — 196,107 U.S. treasury securities — 16,073 — 16,073 Total financial assets $ 13,627 $ 215,614 $ — $ 229,241 December 31, 2020 Level 1 Level 2 Level 3 Fair Value (in thousands) Assets: Money market funds $ 11,938 $ — $ — $ 11,938 Corporate bonds — 5,671 — 5,671 Commercial paper — 57,195 — 57,195 U.S. treasury securities — 20,196 — 20,196 Total financial assets $ 11,938 $ 83,062 $ — $ 95,000
Summary of Significant Unobservable Inputs Used in Measuring Convertible Preferred Stock Tranche Liability	A summary of the significant unobservable inputs used in measuring the Company’s convertible preferred stock tranche liability as of September 30, 2020 is as follows: July 2, 2020 Time to liquidity (years) 0.01 Probability of second closing 100 % Discount rate 20 %
Summary of Changes in Estimated Fair Value of Convertible Preferred Stock Tranche Liability Measured on Recurring Basis	The following table provides a summary of changes in the estimated fair value of the Company’s convertible preferred stock tranche liability measured on a recurring basis using significant Level 3 inputs: Nine Months Ended 2020 (in thousands) Beginning balance December 31, 2019 $ 2,495 Change in fair value $ ( 214 ) Settlement of convertible preferred stock tranche liability ( 2,281 ) Ending balance September 30, 2020 $ —

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Summary of Available-For-Sale Debt Securities	The following tables summarize the fair value and amortized cost of the Company’s available-for-sale debt securities by major security type: September 30, 2021 Amortized Gross Gross Aggregate (in thousands) Assets: Money market funds $ 13,627 $ — $ — $ 13,627 Corporate bonds 3,434 — — 3,434 Commercial paper 196,096 13 ( 2 ) 196,107 U.S. treasury securities 16,068 5 — 16,073 Total financial assets $ 229,225 $ 18 $ ( 2 ) $ 229,241 December 31, 2020 Amortized Gross Gross Aggregate (in thousands) Assets: Money market funds $ 11,938 $ — $ — $ 11,938 Corporate bonds 5,672 1 ( 2 ) 5,671 Commercial paper 57,197 3 ( 5 ) 57,195 U.S. treasury securities 20,196 2 ( 2 ) 20,196 Total financial assets $ 95,003 $ 6 $ ( 9 ) $ 95,000
Summary of Available-For-Sale Debt Securities On Condensed Consolidated Balance Sheets	The following table summarizes the classification of the Company’s available-for-sale debt securities on the condensed consolidated balance sheets: September 30, December 31, 2021 2020 (in thousands) Cash equivalents $ 84,097 $ 17,936 Short-term investments 145,144 57,375 Long-term investments — 19,689 Total cash equivalents and investments $ 229,241 $ 95,000
Summary of Fair Value of Available-For-Sale Debt Securities by Contractual Maturity	The following table summarizes the fair values of the Company’s available-for-sale debt securities by contractual maturity: September 30, December 31, 2021 2020 (in thousands) Within one year $ 229,241 $ 75,311 After one year through two years — 19,689 Total cash equivalents and investments $ 229,241 $ 95,000

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2021
Payables and Accruals [Abstract]
Summary of Accrued and Other Current Liabilities	Accrued and other current liabilities consist of the following: September 30, December 31, 2021 2020 (in thousands) Accrued research and development $ 4,911 $ 2,670 Compensation and related benefits 1,585 854 Accrued professional service expenses 252 — Other 258 202 Total accrued and other current liabilities $ 7,006 $ 3,726

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Schedule of Convertible Preferred Stock	Convertible preferred stock at December 31, 2020 consisted of the following: Shares Shares Issued and Outstanding Net Carrying Value Liquidation (in thousands, except shares) Convertible Preferred Stock Series A 47,647,051 5,672,256 $ 38,015 $ 40,500 Series B 66,176,463 7,878,135 44,895 45,000 Series C 66,236,125 7,885,241 79,702 80,000 Total 180,059,639 21,435,632 $ 162,612 $ 165,500
Schedule of Common Stock Shares Reserved for Issuance	The Company reserved the following shares of common stock, on an as-if converted basis, for issuance as follows: September 30, December 31, 2021 2020 Conversion of outstanding shares of convertible preferred stock — 21,435,632 Options outstanding under the 2021 Equity Incentive plan 3,117,338 1,729,843 Options available for future grant 3,659,419 1,678,228 Total 6,776,757 24,843,703

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	The estimated grant-date fair value of the Company’s stock-based awards was calculated using the Black-Scholes option pricing model, based on the following assumptions: Three Months Ended Nine Months Ended, 2021 2020 2021 2020 Expected term (in years) 5.8 - 6.1 6.0 5.8 - 6.1 6.0 – 6.1 Expected volatility 66.0 % - 66.7 % 70.4 % 66.0 % - 69.9 % 67.1 % - 70.4 % Risk-free interest rate 0.9 % - 1.0 % 0.4 % 0.6 % - 1.1 % 0.4 % - 1.7 % Expected dividend yield —% —% —% —%
Schedule of Stock-based Compensation Expense	Total stock-based compensation recognized in the condensed consolidated statements of operations is as follows: Three Months Ended September 30, Nine Months Ended 2021 2020 2021 2020 (in thousands) Research and development $ 206 $ 35 $ 394 $ 98 General and administrative 457 72 1,022 191 Total stock-based compensation expense $ 663 $ 107 $ 1,416 $ 289
2012 and 2021 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Stock Option Activity	Stock option activity under the 2012 and 2021 Plan was as follows: Options Available for Grant Number of Options Outstanding Weighted-Average Exercise Price Per Share Weighted-Average Aggregate Intrinsic Value (in thousands) Outstanding as of January 1, 2021 1,678,228 1,729,843 $ 2.08 7.75 $ 3,666 Authorized 3,450,000 — — Share rounding difference as a result of the 60 — — Options granted ( 1,872,306 ) 1,872,306 5.84 Options exercised — ( 81,374 ) 2.46 Options cancelled 403,437 ( 403,437 ) 3.30 Outstanding as of September 30, 2021 3,659,419 3,117,338 $ 4.19 8.00 $ 49,387 Exercisable as of September 30, 2021 1,288,031 $ 2.64 6.25 $ 22,404

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Shares Including All Outstanding Stock Options Were Not Included in Calculation of Diluted Shares Outstanding	The following potentially dilutive shares, including all outstanding stock options, were not included in the calculation of diluted shares outstanding for the period presented as the effect would have been anti-dilutive: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Convertible preferred stock — 13,550,391 — 13,550,391 Outstanding stock options 3,117,338 1,708,416 3,117,338 1,708,416 Total 3,117,338 15,258,807 3,117,338 15,258,807

Organization and Description _2

Organization and Description of the Business - Additional Information (Details) $ / shares in Units, $ in Thousands	Jul. 20, 2021USD ($)$ / sharesshares	Jul. 13, 2021	Sep. 30, 2021USD ($)$ / sharesshares	Aug. 20, 2021shares	Dec. 31, 2020USD ($)$ / sharesshares
Organization And Description Of Business [Line Items]
Common stock shares issued			33,457,029		1,030,023
Sale of stock price per share | $ / shares			$ 20.03
Common stock shares authorized			300,000,000		228,300,000
Common stock, par value per share | $ / shares			$ 0.0001		$ 0.0001
Preferred stock, authorized			10,000,000		0
Preferred stock, par value per share | $ / shares			$ 0.0001		$ 0.0001
Accumulated deficit | $			$ 97,927		$ 70,342
Cash, cash equivalents and short-term investments | $			$ 230,400
Reverse stock split			common stock on an 8.4-for-1 basis (the “Reverse Stock Split”)
Reverse stock split conversion ratio		0.119048
IPO
Organization And Description Of Business [Line Items]
Common stock shares issued	8,400,000
Sale of stock price per share | $ / shares	$ 16
Proceeds from issuance of common stock | $	$ 143,700		$ 143,741
Common stock shares authorized	300,000,000
Common stock, par value per share | $ / shares	$ 0.0001
Preferred stock, authorized	10,000,000
Preferred stock, par value per share | $ / shares	$ 0.0001
IPO | Common Stock
Organization And Description Of Business [Line Items]
Convertible preferred stock converted into shares of common stock	21,435,632
Private Placement
Organization And Description Of Business [Line Items]
Common stock shares issued	1,250,000
Proceeds from issuance of common stock | $	$ 20,000		$ 20,000
Underwriters Option to Purchase Additional Shares
Organization And Description Of Business [Line Items]
Common stock shares issued				1,260,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details)	9 Months Ended
	Sep. 30, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update [Extensible Enumeration]	ASC 2018-15
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2021
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update immaterial effect [true false]	true

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:
Financial assets	$ 229,241	$ 95,000
Corporate Bonds
Assets:
Financial assets	3,434	5,671
Money Market Funds
Assets:
Financial assets	13,627	11,938
Commercial Paper
Assets:
Financial assets	196,107	57,195
U.S. Treasury Securities
Assets:
Financial assets	16,073	20,196
Level 1
Assets:
Financial assets	13,627	11,938
Level 1 | Money Market Funds
Assets:
Financial assets	13,627	11,938
Level 2
Assets:
Financial assets	215,614	83,062
Level 2 | Corporate Bonds
Assets:
Financial assets	3,434	5,671
Level 2 | Commercial Paper
Assets:
Financial assets	196,107	57,195
Level 2 | U.S. Treasury Securities
Assets:
Financial assets	$ 16,073	$ 20,196

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, transfers into level 3	$ 0	$ 0
Fair value, transfers out of level 3	0	0
Convertible Preferred Stock Tranche Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Convertible preferred stock tranche liability	$ 0	$ 0	$ 2,495,000

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Significant Unobservable Inputs Used in Measuring Convertible Preferred Stock Tranche Liability (Details) - Level 3	Jul. 02, 2020
Time to Liquidity
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Time to liquidity (years)	3 days
Probability of Second Closing
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Convertible preferred stock tranche liability	1
Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Convertible preferred stock tranche liability	0.20

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Changes in Estimated Fair Value of Convertible Preferred Stock Tranche Liability Measured on Recurring Basis (Details) - Convertible Preferred Stock Tranche Liability $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance December 31, 2019	$ 2,495
Change in fair value	(214)
Settlement of convertible preferred stock tranche liability	$ (2,281)

Investments - Summary of Availa

Investments - Summary of Available-For-Sale Debt Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 229,225	$ 95,003
Gross Unrealized Gains	18	6
Gross Unrealized Losses	(2)	(9)
Aggregate Fair Value	229,241	95,000
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	13,627	11,938
Aggregate Fair Value	13,627	11,938
Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,434	5,672
Gross Unrealized Gains		1
Gross Unrealized Losses		(2)
Aggregate Fair Value	3,434	5,671
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	196,096	57,197
Gross Unrealized Gains	13	3
Gross Unrealized Losses	(2)	(5)
Aggregate Fair Value	196,107	57,195
U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	16,068	20,196
Gross Unrealized Gains	5	2
Gross Unrealized Losses		(2)
Aggregate Fair Value	$ 16,073	$ 20,196

Investments - Summary of Avai_2

Investments - Summary of Available-For-Sale Debt Securities On Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Cash equivalents	$ 84,097	$ 17,936
Short-term investments	145,144	57,375
Long-term investments		19,689
Total cash equivalents and investments	$ 229,241	$ 95,000

Investments - Summary of Fair V

Investments - Summary of Fair Value of Available-For-Sale Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Within one year	$ 229,241	$ 75,311
After one year through two years		19,689
Total cash equivalents and investments	$ 229,241	$ 95,000

Investments - Additional Inform

Investments - Additional Information (Details)	9 Months Ended
	Sep. 30, 2021USD ($)
Investments, Debt and Equity Securities [Abstract]
Other-than-temporary, available-for-sale debt securities	$ 0

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued research and development	$ 4,911	$ 2,670
Accrued professional service expenses	252
Compensation and related benefits	1,585	854
Other	258	202
Total accrued and other current liabilities	$ 7,006	$ 3,726

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)Lease	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)Lease	Sep. 30, 2020USD ($)	Dec. 31, 2020Lease
Commitments and Contingencies Disclosure [Abstract]
Number of cancellable operating lease agreements | Lease	2		2		2
Rent expense | $	$ 21,000	$ 28,000	$ 71,000	$ 76,000

Equity - Schedule of Convertibl

Equity - Schedule of Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Temporary Equity [Line Items]
Shares Authorized	0	180,059,639
Shares Issued	0	21,435,632
Shares Outstanding	0	21,435,632
Net Carrying Value	$ 0	$ 162,612
Liquidation Preference	$ 0	$ 165,500
Series A
Temporary Equity [Line Items]
Shares Authorized		47,647,051
Shares Issued		5,672,256
Shares Outstanding		5,672,256
Net Carrying Value		$ 38,015
Liquidation Preference		$ 40,500
Series B
Temporary Equity [Line Items]
Shares Authorized		66,176,463
Shares Issued		7,878,135
Shares Outstanding		7,878,135
Net Carrying Value		$ 44,895
Liquidation Preference		$ 45,000
Series C
Temporary Equity [Line Items]
Shares Authorized		66,236,125
Shares Issued		7,885,241
Shares Outstanding		7,885,241
Net Carrying Value		$ 79,702
Liquidation Preference		$ 80,000

Equity - Additional Information

Equity - Additional Information (Details) - USD ($)	Jul. 20, 2021	Sep. 30, 2021
Class Of Stock [Line Items]
Common stock voting rights		common stock have one vote for each share of common stock.
Dividends declared or accrued		$ 0
Common Stock | IPO
Class Of Stock [Line Items]
Convertible preferred stock converted into shares of common stock	21,435,632

Equity - Schedule of Common Sto

Equity - Schedule of Common Stock Shares Reserved for Issuance (Details) - shares	Sep. 30, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock, initially reserved for issuance	6,776,757	24,843,703
Conversion of Outstanding Shares of Convertible Preferred Stock
Class Of Stock [Line Items]
Common stock, initially reserved for issuance		21,435,632
Options Available for Future Grant
Class Of Stock [Line Items]
Common stock, initially reserved for issuance	3,659,419	1,678,228
Options Outstanding under 2021 Equity Incentive plan
Class Of Stock [Line Items]
Common stock, initially reserved for issuance	3,117,338	1,729,843

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Oct. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, initially reserved for issuance		6,776,757		6,776,757		24,843,703
Common stock price per share		$ 20.03		$ 20.03
Total intrinsic value of options exercised		$ 0.4		$ 0.7
Options exercised				0
Weighted average grant date fair value for stock options granted		$ 9.66	$ 1.29	$ 3.71	$ 1.20
Expected dividend yield				0.00%
Total unrecognized stock-based compensation expense		$ 6.1		$ 6.1
Weighted-average vesting period of unvested stock options				3 years
2012 Plan | Employees, Directors and Consultants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, initially reserved for issuance							238,095
2021 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, initially reserved for issuance	3,450,000
Minimum percentage of voting rights	10.00%
Minimum percentage of fair market value of exercise price for incentive and non-statutory stock options	110.00%
Vesting period	4 years
Common stock reserved for issuance, annual increase, beginning date	Jan. 1, 2022
Common stock reserved for issuance, annual increase, end date	Jan. 1, 2031
Percentage of annual increase in shares reserved for issuance based on common stock outstanding	5.00%
Number of shares available for issuance		3,659,419		3,659,419
2021 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration term	10 years
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, initially reserved for issuance		350,000		350,000
Common stock reserved for issuance, annual increase, beginning date	Jan. 1, 2022
Common stock reserved for issuance, annual increase, end date	Jan. 1, 2031
Percentage of annual increase in shares reserved for issuance based on common stock outstanding	1.00%
Shares authorized	4,703,469
Shares issued		0

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Number of Options Outstanding
Options exercised	0
2012 and 2021 Plan
Options Available for Grant
Outstanding at beginning of period	1,678,228
Authorized	3,450,000
Share rounding difference as a result of the reverse stock split	60
Options granted	(1,872,306)
Options cancelled	403,437
Outstanding at end of period	3,659,419	1,678,228
Number of Options Outstanding
Outstanding at beginning of period	1,729,843
Options granted	1,872,306
Options exercised	(81,374)
Options cancelled	(403,437)
Outstanding at end of period	3,117,338	1,729,843
Exercisable at end of period	1,288,031
Weighted-Average Exercise Price Per Share
Outstanding at beginning of period | $ / shares	$ 2.08
Options granted | $ / shares	5.84
Options exercised | $ / shares	2.46
Options cancelled | $ / shares	3.30
Outstanding at end of period | $ / shares	4.19	$ 2.08
Exercisable at end of period | $ / shares	$ 2.64
Weighted-Average Remaining Contractual Life (years)
Outstanding	8 years	7 years 9 months
Exercisable	6 years 3 months
Aggregate Intrinsic Value
Aggregate Intrinsic Value Outstanding | $	$ 49,387	$ 3,666
Exercisable at end of period | $	$ 22,404

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Estimated Grant-Date Fair Value of Stock-Based Awards Calculated Using Black-Scholes Option Pricing Model (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]
Expected term (in years)		6 years
Expected volatility		70.40%
Expected volatility, minimum	66.00%		66.00%	67.10%
Expected volatility, maximum	66.70%		69.90%	70.40%
Risk-free interest rate		0.40%
Risk-free interest rate, minimum	0.90%		0.60%	0.40%
Risk-free interest rate, maximum	1.00%		1.10%	1.70%
Expected dividend yield			0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 9 months 18 days		5 years 9 months 18 days	6 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days		6 years 1 month 6 days	6 years 1 month 6 days

Stock-Based Compensation - Sc_3

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 expense	$ 663	$ 107	$ 1,416	$ 289
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	206	35	394	98
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 457	$ 72	$ 1,022	$ 191

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 0	$ 0

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Potentially Dilutive Shares Including All Outstanding Stock Options Were Not Included in Calculation of Diluted Shares Outstanding (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]
Potentially dilutive shares	3,117,338	15,258,807	3,117,338	15,258,807
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive shares		13,550,391		13,550,391
Outstanding Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive shares	3,117,338	1,708,416	3,117,338	1,708,416