Vera Therapeutics (VERA) S-1 7 Feb 22 IPO registration Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2021
Document Information [Line Items]
Document Type	S-1
Amendment Flag	false
Entity Registrant Name	Vera Therapeutics, Inc.
Entity Central Index Key	0001831828
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false

Condensed Balance Sheet

Condensed Balance Sheet - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 86,191	$ 53,654	$ 3,195
Restricted cash, current		50
Prepaid expenses and other current assets	3,569	557	370
Total current assets	89,760	54,261	3,565
Restricted cash, noncurrent	293	293	363
Property and equipment, net			1,394
Non-marketable equity securities	1,114
Other assets			59
Total assets	91,167	54,554	5,381
Current liabilities:
Accounts payable	964	909	342
Capital lease payable, current		2	122
Restructuring liability, current	367	962	173
Accrued expenses and other current liabilities	2,711	535
Accrued expenses and other current liabilities		533	423
Total current liabilities	4,042	2,406	1,060
Capital lease payable, noncurrent			10
Restructuring liability, noncurrent	1,362	1,634
Accrued and other noncurrent liabilities	286	286	764
Total liabilities	5,690	4,326	1,834
Commitments and contingencies (Note 12)
Redeemable convertible preferred stock, $0.001 par value; 0 and 182,772,372 shares authorized, issued and outstanding as of September 30, 2021 and December 31, 2020, respectively		139,576	40,095
Stockholders' equity (deficit)
Preferred stock, $0.001 par value; 10,000,000 and 0 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
Additional paid-in capital	192,665	2,099	1,486
Accumulated deficit	(107,209)	(91,447)	(38,034)
Total stockholders' equity (deficit)	85,477	(89,348)	(36,548)
Total liabilities, redeemable convertible preferred stock, and stockholders' equity (deficit)	91,167	54,554	5,381
Common Class A [Member]
Stockholders' equity (deficit)
Common Stock	21	0
Common Class B Non Voting [Member]
Stockholders' equity (deficit)
Common Stock	$ 0	$ 0	$ 0

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Temporary equity par or stated value per share	$ 0.001	$ 0.001	$ 0.001
Temporary equity shares authorized	0	182,772,372	15,907,207
Temporary equity shares issued	0	182,772,372	14,015,773
Temporary equity shares outstanding	0	182,772,372	14,015,773
Preferred stock par or stated value per share	$ 0.001	$ 0.001
Preferred stock shares authorized	10,000,000	0
Preferred stock shares issued	0	0
Preferred stock shares outstanding	0	0
Common Class A [Member]
Common stock, Par value	$ 0.001	$ 0.001	$ 0.001
Common stock, Shares authorized	500,000,000	273,986,920	23,000,000
Common stock, Shares issued	20,968,376	355,296	322,007
Common stock, Shares outstanding	20,968,376	355,296	322,007
Common Class B [Member]
Common stock, Par value	$ 0.001	$ 0.001
Common stock, Shares authorized	14,600,000	21,593,607
Common stock, Shares issued	309,238	0
Common stock, Shares outstanding	309,238	0
Common Class B Non Voting [Member]
Common stock, Par value		$ 0.001	$ 0.001
Common stock, Shares authorized		21,593,607	0
Common stock, Shares issued		0	0
Common stock, Shares outstanding		0	0

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 9,731	$ 5,362	$ 45,206	$ 7,290
General and administrative	8,086	2,903	4,039	4,410
Restructuring costs	116	1,416	2,996	261
Total operating expenses	17,817	9,681	52,241	11,961
Loss from operations	(17,817)	(9,681)	(52,241)	(11,961)
Other income (expense):
Interest income	9	6	8	159
Interest expense		(151)	(166)	(51)
Gain on issuance of convertible notes		63	63
Change in fair value of convertible notes		(775)	(1,076)
Change in fair value of non-marketable equity securities	(645)
Gain on sale of PNAi technology	2,691
Total other income (expense)	2,055	(857)	(1,171)	108
Loss before provision for income taxes			(53,412)	(11,853)
Provision for income taxes	0	0	(1)	(1)
Net loss and comprehensive loss	$ (15,762)	$ (10,538)	$ (53,413)	$ (11,854)
Net loss per share attributable to common stockholders, basic and diluted	$ (1.46)	$ (32.64)	$ (166.93)	$ (40.14)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted	10,793,436	322,811	319,963	295,328

Condensed Statements of Redeema

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common stock [Member]	Additional paid-in capital [Member]	Accumulated deficit [Member]	Redeemable convertible preferred stock [Member]	Class A common stock [Member]Common stock [Member]	Class B common stock [Member]Common stock [Member]	Series C Redeemable Convertible Preferred Stock [Member]	Previously Reported [Member]Additional paid-in capital [Member]
Beginning Balance, Temporary Equity, shares at Dec. 31, 2018					14,015,773
Beginning Balance, Temporary Equity Value at Dec. 31, 2018					$ 40,095
Beginning balance, shares at Dec. 31, 2018		312,082
Beginning Balance, Value at Dec. 31, 2018	$ (25,008)	$ 0	$ 1,172	$ (26,180)
Issuance of Class A common stock upon exercise of options	51		51
Issuance of Class A common stock upon exercise of options, shares		9,925
Stock-based compensation	263		263
Net loss	(11,854)			(11,854)
Ending Balance, shares at Dec. 31, 2019		322,007
Ending Balance, Value at Dec. 31, 2019	$ (36,548)		1,486	(38,034)					$ 1,486
Ending Balance, Temporary Equity , shares at Dec. 31, 2019	14,015,773				14,015,773
Ending Balance, Temporary Equity Value at Dec. 31, 2019					$ 40,095
Issuance of Class A common stock upon exercise of options	$ 23		23
Issuance of Class A common stock upon exercise of options, shares		4,045
Stock-based compensation	188		188
Net loss	(10,538)			(10,538)
Ending Balance, shares at Sep. 30, 2020		326,052
Ending Balance, Value at Sep. 30, 2020	$ (46,875)		1,697	(48,572)
Ending Balance, Temporary Equity , shares at Sep. 30, 2020					14,015,773
Ending Balance, Temporary Equity Value at Sep. 30, 2020					$ 40,095
Beginning Balance, Temporary Equity, shares at Dec. 31, 2019	14,015,773				14,015,773
Beginning Balance, Temporary Equity Value at Dec. 31, 2019					$ 40,095
Beginning balance, shares at Dec. 31, 2019		322,007
Beginning Balance, Value at Dec. 31, 2019	$ (36,548)		1,486	(38,034)					$ 1,486
Conversion of preferred stock into common stock, Shares								135,180,800
Conversion of preferred stock into common stock								$ 79,611
Issuance of Class A common stock upon exercise of options	282		282
Issuance of Class A common stock upon exercise of options, shares		33,289
Issuance of Series C redeemable convertible preferred stock upon extinguishment of convertible notes, Shares								11,404,246
Issuance of Series C redeemable convertible preferred stock upon extinguishment of convertible notes								$ 6,749
Issuance of Series C redeemable convertible preferred stock for license, Shares								22,171,553
Issuance of Series C redeemable convertible preferred stock for license								$ 13,121
Stock-based compensation	331		331
Net loss	(53,413)			(53,413)
Ending Balance, shares at Dec. 31, 2020		355,296				355,296	0
Ending Balance, Value at Dec. 31, 2020	$ (89,348)	$ 0	2,099	(91,447)		$ 0	$ 0
Ending Balance, Temporary Equity , shares at Dec. 31, 2020	182,772,372				182,772,372			168,756,599
Ending Balance, Temporary Equity Value at Dec. 31, 2020					$ 139,576
Common stock issued pursuant to initial public offering, net of issuance costs, Shares						5,002,500
Common stock issued pursuant to initial public offering, net of issuance costs	$ 48,411		48,406			$ 5
Conversion of preferred stock into common stock, Shares					(182,772,372)	15,464,775	309,238
Conversion of preferred stock into common stock	139,576		139,560		$ (139,576)	$ 16
Issuance of Class A common stock upon exercise of options	550		550
Issuance of Class A common stock upon exercise of options, shares						145,805
Stock-based compensation	2,050		2,050
Net loss	(15,762)			(15,762)
Ending Balance, shares at Sep. 30, 2021						20,968,376	309,238
Ending Balance, Value at Sep. 30, 2021	$ 85,477		$ 192,665	$ (107,209)		$ 21
Ending Balance, Temporary Equity , shares at Sep. 30, 2021	0				0
Ending Balance, Temporary Equity Value at Sep. 30, 2021					$ 0

Condensed Statements of Redee_2

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Series C Redeemable Convertible Preferred Stock [Member]
Stock issuance Costs	$ 389

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (15,762)	$ (10,538)	$ (53,413)	$ (11,854)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation, amortization and accretion	144	893	251	509
Impairment loss on property and equipment and intangible asset		1,185	1,185	10
Loss on disposal of property and equipment				94
Stock-based compensation	2,050	188	331	263
Issuance of Series C redeemable convertible preferred stock for license			13,121
Restructuring costs, net of cash paid	28		2,423	173
Restructuring payments	(875)	(88)
Non-cash interest expense on convertible notes		125	134
Issuance costs for convertible notes		24	23
Gain on issuance of convertible notes		(63)	(63)
Gain on sale of PNAi technology	(2,691)
Change in fair value of convertible notes		775	1,076
Change in fair value of non-marketable equity securities	645
Changes in operating assets and liabilities:
Prepaid expense and other current assets	(3,012)	(6)	(135)	320
Other assets			59	(19)
Grants receivable				159
Accounts payable	55	(3)	567	(291)
Accrued and other current liabilities	2,176	264	110	60
Other liabilities		(183)	(478)	287
Net cash used in operating activities	(17,270)	(7,427)	(34,809)	(10,289)
Cash flows from investing activities
Proceeds from sale of PNAi technology	796
Purchase of property and equipment		(99)	(99)	(125)
Proceeds from the sale of property and equipment			57
Net cash provided by (used in) investing activities	796	(99)	(42)	(125)
Cash flows from financing activities
Proceeds from exercise of stock options	550	23	230	51
Proceeds from issuance of Series C redeemable convertible preferred stock			80,000
Proceeds from issuance of convertible notes		5,602	5,602
Proceeds from issuance of Class A common stock upon initial public offering, net of underwriting discounts and commissions	51,176
Payment of offering costs related to initial public offering	(2,765)		(389)
Payment issuance costs related to convertible promissory notes		(24)	(23)
Payment on capital lease obligations		(112)	(130)	(188)
Net cash provided by financing activities	48,961	5,489	85,290	(137)
Net increase (decrease) in cash and cash equivalents and restricted cash	32,487	(2,037)	50,439	(10,551)
Cash, cash equivalents and restricted cash, beginning of period	53,997	3,558	3,558	14,109
Cash, cash equivalents and restricted cash, end of period	86,484	1,521	53,997	3,558
Supplemental disclosure of cash flow information
Cash paid for interest		21	32	51
Purchases of property and equipment through capital leases				18
Issuance of Series C redeemable convertible preferred stock for license			13,121
Issuance of Series C redeemable convertible preferred stock upon extinguishment of convertible notes			5,736
Reclassification of redeemable convertible preferred stock into common stock upon initial public offering	139,576
Non-marketable equity securities received as partial proceeds from sale of PNAi technology	1,759
Lease assignment	136
Receivables on exercise of stock options			52
Cash and cash equivalents [Member]
Cash flows from financing activities
Cash, cash equivalents and restricted cash, beginning of period	53,654	3,195	3,195
Cash, cash equivalents and restricted cash, end of period	86,191	1,451	53,654	3,195
Restricted cash [Member]
Cash flows from financing activities
Cash, cash equivalents and restricted cash, beginning of period	343	363	363
Cash, cash equivalents and restricted cash, end of period	$ 293	$ 70	$ 343	$ 363

Organization and Description of

Organization and Description of the Business	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of the Business	1. Organization and description of the business Description of business Vera Therapeutics, Inc., (the “Company”) is a late-stage biotechnology Reverse stock split On May 7, 2021, the Company filed a certificate of amendment to its fourth amended and restated certificate of incorporation to effect a 11.5869-for-one Initial public offering On May 13, 2021, the Company’s registration statement on Form S-1 Liquidity Since inception, the Company has been primarily performing research and development activities, establishing and maintaining its intellectual property, hiring personnel and raising capital to support and expand these operations. The Company has incurred recurring net operating losses since its inception and had an accumulated deficit of $107,209 as of September 30, 2021. The Company had cash and cash equivalents of $86,191 as of September 30, 2021, and has not generated positive cash flow from operations. The Company has funded its operations primarily through the issuance of common stock, redeemable convertible preferred stock and convertible notes. Management believes that the Company’s cash and cash equivalents as of September 30, 2021, will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of these unaudited condensed financial statements. While the Company believes that its current cash and cash equivalents are adequate to meet its needs for the next 12 months, the Company will need to raise additional capital in order to achieve its longer-term business objectives.	1. Organization and description of the business Description of business Vera Therapeutics, Inc., (the “Company”) is a clinical stage biotechnology company focused on developing and commercializing transformative treatments for patients with serious immunological diseases. The Company is headquartered in South San Francisco, California and was incorporated in May 2016 in Delaware. In 2017, the Company acquired all of the outstanding shares of PNA Innovations, Inc. (“PNAi”), which was based in Woburn, Massachusetts. Liquidity The accompanying financial statements have been prepared assuming the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business, and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or amounts and classification of liabilities that may result from the outcome of this uncertainty. The Company has incurred recurring net operating losses since its inception and had an accumulated deficit of $91,447 as of December 31, 2020. The Company had cash and cash equivalents of $53,654 as of December 31, 2020 and has not generated positive cash flow from operations. To date, the Company has been able to fund its operation primarily through the issuance of redeemable convertible preferred stock and convertible notes. The Company expects to continue to generate operating losses for the foreseeable future. There can be no assurance that the Company will ever earn revenues or achieve profitability or, if achieved, that they will be sustained on a continuing basis. If the Company is unable to obtain funding, the Company will be forced to delay or reduce some or all of its product development programs, which could adversely affect its business prospects, or the Company may be unable to continue operations. Although the Company continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient future funding on terms acceptable to the Company to fund continuing operations, if at all. The Company believes that it has sufficient resources to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of these financial statements. While the Company believes that its current cash and cash equivalents are adequate to meet its needs for the next 12 months, the Company may need to raise additional equity or borrow funds in order to achieve its longer-term business objectives.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	2. Basis of presentation and significant accounting policies Basis of presentation The accompanying unaudited condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. The U.S. dollar is the Company’s functional and reporting currency. Unaudited interim condensed financial statements The accompanying condensed balance sheet as of September 30, 2021, and condensed statements of operations and comprehensive loss, condensed statements of cash flows, and condensed statements of redeemable convertible preferred stock and stockholders’ equity (deficit) for the nine months ended September 30, 2021 and 2020, are unaudited. The balance sheet as of December 31, 2020, was derived from the audited financial statements as of and for the year ended December 31, 2020. The unaudited condensed financial statements have been prepared on a basis consistent with the audited annual financial statements as of and for the year ended December 31, 2020 and in the opinion of management, reflect all adjustments consisting solely of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2021, and the condensed results of its operations and its cash flows for the nine months ended September 30, 2021. The financial data and other information disclosed in these notes related to the nine months ended September 30, 2021, are also unaudited. The condensed results of operations for the nine months ended September 30, 2021, are not necessarily indicative of the results to be expected for the full year ending December 31, 2021, or any other period. These unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2020, included in the Company’s final prospectus dated May 13, 2021, for the IPO filed with the SEC on May 17, 2021, pursuant to Rule 424(b)(4) relating to the Company’s Registration Statement on Form S-1, No. 333-255492). Emerging growth company status The Company is an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with certain new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (1) is no longer an emerging growth company or (2) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these unaudited condensed financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. Use of estimates The preparation of the Company’s unaudited condensed financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the unaudited condensed financial statements and the reported amounts of expenses during the reporting period. Management estimates that affect the reported amounts of assets and liabilities include the accrual of research and development expenses, restructuring liabilities, fair value of common stock and stock-based compensation expense, and the valuation allowance for deferred tax assets. The Company evaluates and adjusts its estimates and assumptions on an ongoing basis using historical experience and other factors. Actual results could differ materially from those estimates. Deferred offering costs Deferred offering costs consisting of legal, accounting and filing fees relating to the IPO are capitalized. The deferred offering costs were offset against the Company’s IPO proceeds upon the closing of the IPO. Concentrations of credit risk and other risks and uncertainties Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains bank deposits in a federally insured financial institution and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of default by the financial institution holding its cash and cash equivalents to the extent recorded in the balance sheet. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s current and potential future product candidates, uncertainty of market acceptance of the Company’s product candidates, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals or sole-source suppliers. The Company’s product candidates require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed, or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. Impact of the COVID-19 The COVID-19 COVID-19 COVID-19 COVID-19 COVID-19 operations and development timelines and plans, including the resulting impact on expenditures and capital needs, remains uncertain. Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Cash equivalents consist of money market funds and are stated at fair value. Restricted cash Restricted cash represents cash held by a financial institution as collateral for a letter of credit securing its operating lease for office and laboratory space and as collateral for a credit card, which are classified within current and non-current Comprehensive loss Comprehensive loss consists of net loss and other gains and losses affecting redeemable convertible preferred stock and stockholders’ equity (deficit) that, under U.S. GAAP, are excluded from net loss. The Company has no items of other comprehensive loss for the nine months ended September 30, 2021 and 2020. As such, net loss equals comprehensive loss. Research and development costs Research and development costs are expensed as incurred and consist primarily of employees’ salaries and related benefits, including stock-based compensation and termination expenses for employees engaged in research and development efforts, allocated overhead including rent, depreciation, information technology and utilities, contracted services, license fees, and external expenses to conduct and support the Company’s operations that are directly attributable to the Company’s research and development efforts. Payments made to third parties under these arrangements in advance of the performance of the related services by the third parties are recorded as prepaid expenses until the services are rendered. Costs incurred in obtaining technology licenses including upfront and milestone payments incurred under the Company’s licensing agreements are recorded as expense in the period in which they are incurred, provided that the licensed technology, method or process has no alternative future uses other than for the Company’s research and development activities. Research contract costs and accruals The Company enters into various research and development and other agreements with commercial firms, researchers, and others for provisions of goods and services from time to time. These agreements are generally cancellable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company’s estimates. Redeemable convertible preferred stock The Company records all shares of redeemable convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The carrying value of the Company’s redeemable convertible preferred stock is adjusted to reflect dividends if and when declared by the Company’s board of directors. No dividends have been declared by the board of directors since inception. The Company classifies its redeemable convertible preferred stock separate from total stockholders’ equity (deficit), as the redemption of such stock is not solely under the control of the Company. Stock-based compensation The Company recognizes compensation expense based on estimated fair values for all stock-based payment awards made to the Company’s employees, nonemployee directors and consultants that are expected to vest. The valuation of stock option awards is determined at the date of grant using the Black-Scholes option pricing model. The Black-Scholes option pricing model requires the Company to make assumptions and judgements about the inputs used in the calculations, such as the fair value of the common stock, expected term, expected volatility of the Company’s common stock, risk-free interest rate and expected dividend yield. The valuation of restricted stock awards is measured by the fair value of the Company’s common stock on the date of the grant. For all stock options granted, the Company calculated the expected term using the simplified method (derived from the average midpoint between the weighted average vesting period and the contractual term of the award) for “plain vanilla” stock option awards, as the Company has limited historical information to develop expectations about future exercise patterns and post vesting employment termination behavior. The estimate of expected volatility is based on comparative companies’ volatility. The risk-free rate is based on the yield available on United States Treasury zero-coupon The fair value of the shares of common stock underlying the stock options has historically been determined by the board of directors with the assistance of management and input from an independent third-party valuation firm, as there was no public market for the common stock. The board of directors determined the fair value of the Company’s common stock by considering a number of objective and subjective factors, including the valuation of comparable companies, sales of redeemable convertible preferred stock, the Company’s operating and financial performance, the lack of liquidity of common stock, and general and industry specific economic outlook, amongst other factors. The Company records compensation expense for service-based awards on a straight-line basis over the requisite service period, which is generally the vesting period of the award. The amount of stock-based compensation expense recognized during a period is based on the value of the portion of the awards that are ultimately expected to vest. Income taxes The Company did not record an income tax provision for the nine months ended September 30, 2021 and 2020 as net operating losses have been incurred since inception. The net deferred tax assets generated from net operating losses are fully offset by a valuation allowance. Net loss per share attributable to common stockholders Net loss per share of common stock is computed using the two-class The Company’s participating securities include the Company’s redeemable convertible preferred stock, as the holders were entitled to receive noncumulative dividends on a pari passu basis in the event that a dividend is paid on common stock. The Company also considers any shares issued on the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable two-class Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, adjusted for outstanding shares that are subject to repurchase. Diluted net loss per share is computed by giving effect to all potentially dilutive securities outstanding for the period using the treasury stock method or the if-converted Leases The Company leases office and laboratory space under operating leases and laboratory equipment under capital leases. Leases for which the Company assumes substantially all risks and rewards incidental to ownership of the leased assets are classified as capital leases. The leased assets and the corresponding lease liabilities (net of interest charges) are recognized on the balance sheet as property and equipment, based on the cost of the equipment, and borrowings, respectively, at the inception of the related lease. Each lease payment is apportioned between the reduction of the outstanding lease liability and the related interest expense. The interest expense is recorded on a basis that reflects a constant periodic rate of interest on the outstanding finance lease liability. Leases for which substantially all risks and rewards incidental to ownership are retained by the lessors are classified as operating leases. Payments made under operating leases (net of any incentive received from the lessors) are recorded on a straight-line basis over the period of the lease. Restructuring costs Restructuring costs primarily consist of contract termination costs related to leases and employee termination costs. The Company recognizes restructuring charges when the liability has been incurred. Key assumptions in determining the restructuring costs include the terms and payments that may be negotiated to terminate certain contractual obligations, cease use date of leased property and equipment, and the timing of employees leaving the Company. Accretion expenses related to restructuring costs are included in general and administrative expenses. Fair value option The convertible notes issued in 2020, for which the Company elected the fair value option, are accounted for at fair value on a recurring basis with changes in fair value recognized in the statement of operations and comprehensive loss. Interest accrued on the convertible notes was recorded to interest expense during the periods in which the convertible notes were outstanding. Fair value measurements Fair value is defined as the exchange price to sell an asset or transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Fair value should be based on the assumptions market participants would use when pricing the asset or liability. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. Fair value measurements are classified and disclosed in one of the following three categories: Level 1—Quoted unadjusted prices for identical instruments in active markets. Level 2—Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all observable inputs and significant value drivers are observable in active markets. Level 3—Model derived valuations in which one or more significant inputs or significant value drivers are unobservable, including assumptions developed by the Company. The carrying amounts of the Company’s cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair value due to their short-term nature. Money market funds are highly liquid investments that are actively traded. The pricing information for the Company’s money market funds are 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 non-marketable non-marketable There were no transfers between Levels 1, 2, or 3 for any of the periods presented. As of September 30, 2021, and December 31, 2020, the Company held $84,810 and $52,301, respectively, in money market funds with no unrealized gains or losses. Recently adopted accounting pronouncements In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. On June 20, 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting earlier than under current guidance for nonemployee awards. The Company adopted this standard as of January 1, 2020 on a retrospective basis. The adoption of this standard did not have a material impact on its unaudited condensed financial statements. In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to Recently issued accounting pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2018-10, 2018-11, 2018-20, 2019-01 2019-10, right-of-use In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In August 2020, the FASB issued ASU No. 2020-06, 470-20) 815-40). 470-20 2020-06	2. Basis of presentation and significant accounting policies Basis of presentation The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The U.S. dollar is the Company’s functional and reporting currency. Reclassification Certain reclassification of prior period amounts related to restructuring activities has been made to conform to the current year presentation. Emerging growth company status The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with certain new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (1) is no longer an emerging growth company or (2) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. Use of estimates The preparation of the Company’s financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Management estimates that affect the reported amounts of assets and liabilities include useful lives of fixed and intangible assets, the accrual of research and development expenses, restructuring liabilities, fair value of common stock and stock-based compensation expense, and the valuation allowance for deferred tax assets. The Company evaluates and adjusts its estimates and assumptions on an ongoing basis using historical experience and other factors. Actual results could differ materially from those estimates. Segment information The Company operates as a single operating segment. The Company’s chief operating decisionmaker, its Chief Executive Officer, manages the Company’s entire operations as a whole for the purposes of allocating resources, making operating decisions and evaluating financial performance. Concentrations of credit risk and other risks and uncertainties Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains bank deposits in a federally insured financial institution and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of default by the financial institution holding its cash and cash equivalents to the extent recorded in the balance sheet. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s current and potential future product candidates, uncertainty of market acceptance of the Company’s product candidates, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals or sole-source suppliers. The Company’s product candidates require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed, or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. Impact of the COVID-19 The COVID-19 COVID-19 COVID-19 COVID-19 COVID-19 Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Cash equivalents consist of money market funds and are stated at fair value. Restricted cash Restricted cash represents cash held by a financial institution as collateral for a letter of credit securing its operating lease for office and laboratory space and as collateral for a credit card, which are classified within current and non-current Comprehensive loss Comprehensive loss consists of net loss and other gains and losses affecting redeemable convertible preferred stock and stockholders’ deficit that, under U.S. GAAP, are excluded from net loss. The Company has no items of other comprehensive loss for the years ended December 31, 2019 and 2020. As such, net loss equals comprehensive loss. Property and equipment, net Property and equipment are recorded at cost, less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset category, for which each category the useful life is estimated at five years. Leasehold improvements are capitalized and amortized over the shorter of the lease term or the estimated useful life of the related asset. Expenditures for repairs and maintenance of assets are charged to expense as incurred, whereas major improvements are capitalized as additions to property and equipment. Amortization of assets under capital leases is included in depreciation expense. Upon retirement or sale, the cost and related accumulated depreciation of assets disposed of are removed from the accounts and any resulting gain or loss is reflected in the statement of operations and comprehensive loss. Impairment of long-lived assets The Company reviews its long-lived assets, including property and equipment and intangible assets, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount. The impairment loss, if recognized, would be based on the excess of the carrying value of the impaired asset over its respective fair value. During the years ended December 31, 2019 and 2020, the Company recorded asset impairments totaling $10 and $1,185, respectively, on certain intangible assets and certain laboratory and office equipment (see Note 3). Research and development costs Research and development costs are expensed as incurred and consist primarily of employees’ salaries and related benefits, including stock-based compensation and termination expenses for employees engaged in research and development efforts, allocated overhead including rent, depreciation, information technology and utilities, contracted services, license fees, and external expenses to conduct and support the Company’s operations that are directly attributable to the Company’s research and development efforts. Payments made to third parties under these arrangements in advance of the performance of the related services by the third parties are recorded as prepaid expenses until the services are rendered. Costs incurred in obtaining technology licenses including upfront and milestone payments incurred under the Company’s licensing agreements are recorded as expense in the period in which they are incurred, provided that the licensed technology, method or process has no alternative future uses other than for the Company’s research and development activities. Research contract costs and accruals The Company enters into various research and development and other agreements with commercial firms, researchers, and others for provisions of goods and services from time to time. These agreements are generally cancellable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company’s estimates. Redeemable convertible preferred stock The Company records all shares of redeemable convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The carrying value of the Company’s redeemable convertible preferred stock is adjusted to reflect dividends if and when declared by the Company’s board of directors. No dividends have been declared by the board of directors since inception. The Company classifies its redeemable convertible preferred stock separate from total stockholders’ deficit, as the redemption of such stock is not solely under the control of the Company. Stock-Based compensation The Company recognizes compensation expense based on estimated fair values for all stock-based payment awards made to the Company’s employees, nonemployee directors and consultants that are expected to vest. The valuation of stock option awards is determined at the date of grant using the Black-Scholes option pricing model. The Black-Scholes option pricing model requires the Company to make assumptions and judgements about the inputs used in the calculations, such as the fair value of the common stock, expected term, expected volatility of the Company’s common stock, risk-free interest rate and expected dividend yield. The valuation of restricted stock awards is measured by the fair value of the Company’s common stock on the date of the grant. For all stock options granted, the Company calculated the expected term using the simplified method (derived from the average midpoint between the weighted average vesting period and the contractual term of the award) for “plain vanilla” stock option awards, as the Company has limited historical information to develop expectations about future exercise patterns and post vesting employment termination behavior. The estimate of expected volatility is based on comparative companies’ volatility. The risk-free rate is based on the yield available on United States Treasury zero-coupon The fair value of the shares of common stock underlying the stock options has historically been determined by the board of directors with the assistance of management and input from an independent third-party valuation firm, as there was no public market for the common stock. The board of directors determines the fair value of the Company’s common stock by considering a number of objective and subjective factors, including the valuation of comparable companies, sales of redeemable convertible preferred stock, the Company’s operating and financial performance, the lack of liquidity of common stock, and general and industry specific economic outlook, amongst other factors. The Company records compensation expense for service-based awards on a straight-line basis over the requisite service period, which is generally the vesting period of the award. The amount of stock-based compensation expense recognized during a period is based on the value of the portion of the awards that are ultimately expected to vest. Income taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step more-likely-than-not be recognized is the largest amount that is more likely than not of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax allowance, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Net loss per share attributable to common stockholders Net loss per share of common stock is computed using the two-class The Company’s participating securities include the Company’s redeemable convertible preferred stock, as the holders are entitled to receive noncumulative dividends on a pari passu basis in the event that a dividend is paid on common stock. The Company also considers any shares issued on the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable two-class Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, adjusted for outstanding shares that are subject to repurchase. Diluted net loss per share is computed by giving effect to all potentially dilutive securities outstanding for the period using the treasury stock method or the if-converted Leases The Company leases office and laboratory space under operating leases and laboratory equipment under capital leases. Leases for which the Company assumes substantially all risks and rewards incidental to ownership of the leased assets are classified as capital leases. The leased assets and the corresponding lease liabilities (net of interest charges) are recognized on the balance sheet as property and equipment, based on the cost of the equipment, and borrowings, respectively, at the inception of the related lease. Each lease payment is apportioned between the reduction of the outstanding lease liability and the related interest expense. The interest expense is recorded on a basis that reflects a constant periodic rate of interest on the outstanding finance lease liability. Leases for which substantially all risks and rewards incidental to ownership are retained by the lessors are classified as operating leases. Payments made under operating leases (net of any incentive received from the lessors) are recorded on a straight-line basis over the period of the lease. Restructuring costs Restructuring costs primarily consist of contract termination costs related to leases and employee termination costs. The Company recognizes restructuring charges when the liability has been incurred. Key assumptions in determining the restructuring costs include the terms and payments that may be negotiated to terminate certain contractual obligations, cease use date of leased property and equipment, and the timing of employees leaving the Company. Accretion expenses related to restructuring costs are included in general and administrative expenses. Fair value option The convertible notes issued in 2020, for which the Company elected the fair value option, are accounted for at fair value on a recurring basis with changes in fair value recognized in the statement of operations and comprehensive loss. Interest accrued on the convertible notes is recorded to interest expense. Fair value measurements Fair value is defined as the exchange price to sell an asset or transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Fair value should be based on the assumptions market participants would use when pricing the asset or liability. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. Fair value measurements are classified and disclosed in one of the following three categories: Level 1—Quoted unadjusted prices for identical instruments in active markets. Level 2—Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all observable inputs and significant value drivers are observable in active markets. Level 3—Model derived valuations in which one or more significant inputs or significant value drivers are unobservable, including assumptions developed by the Company. The carrying amounts of the Company’s cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair value due to their short-term nature. Money market funds are highly liquid investments that are actively traded. The pricing information for the Company’s money market funds are 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. There were no transfers between Levels 1, 2, or 3 for any of the periods presented. As of December 31, 2019, and 2020, the Company held $2,470 and $52,301, respectively, in money market funds with no unrealized gains or losses. The estimated fair value of the convertible notes, which is classified as Level 3 of the fair value hierarchy, is determined by using a scenario-based analysis that estimates the fair value of the convertible notes based on the probability-weighted present value of expected future investment returns, considering possible outcomes available to the noteholder, including conversions in subsequent equity financings, change of control transactions, settlement and dissolution. Recently adopted accounting pronouncements In November 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-18, Statement of Cash Flows – Restricted Cash (Topic 230) beginning-of-period end-of-period On June 20, 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement Recently issued accounting pronouncements In February 2016, the FASB issued ASU No. 2016-02 , Leases (Topic 842) 2018-10, 2018-11, 2018-20, 2019-01 2019-10, right-of-use In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In August 2020, the FASB issued ASU No. 2020-06, 470-20) 815-40). 470-20 2020-06 periods, beginning after December 15, 2023, and early adoption is permitted. The Company is currently evaluating the impact this standard will have on its financial statements.

Other Financial Statement Infor

Other Financial Statement Information	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Other Financial Statement Information [Abstract]
Other Financial Statement Information	3. Other financial statement information Prepaid expense and other current assets Prepaid expenses and other current assets consist of the following. September 30, December 31, Prepaid insurance $ 1,837 $ 27 Prepaid contract costs 889 — Deposits 57 86 Receivables on exercise of options — 52 Other 786 392 Total prepaid expenses and other current assets $ 3,569 $ 557 Accrued expenses and other current liabilities Accrued expenses and other current liabilities consist of the following. September 30, December 31, Accrued payroll $ 1,051 $ 405 Related party payable 994 — Accrued expenses and other 666 130 Total accrued expenses and other current liabilities $ 2,711 $ 535 Related party payable represents amounts due to Ares Trading S.A. (“Ares”), an affiliate of Merck KGaA, Darmstadt, Germany, related to manufacturing technology and know-how	3. Other financial statement information Prepaid expense and other current assets Prepaid expenses and other current assets consist of the following. December 31, 2019 2020 Prepaid expenses $ 332 $ 336 Deposits 34 86 Receivables on exercise of options — 52 Other 4 83 Total prepaid expenses and other current assets $ 370 $ 557 Property and equipment, net Property and equipment, net consists of the following as of December 31, 2019. Equipment under capital lease $ 929 Laboratory equipment 734 Leasehold improvements 421 Furniture and fixtures 269 Office equipmen t 61 Total property and equipment 2,414 Accumulated depreciation and amortization (1,020 ) Total property and equipment, net $ 1,394 Depreciation and amortization expense for the years ended December 31, 2019 and 2020 was $432 and $251, respectively, including amortization expense related to capital leases of $184 and $108 for the years ended December 31, 2019 and 2020, respectively. During the year ended December 31, 2019, the Company disposed of certain laboratory equipment, incurring a loss on disposal of $94, which is included in research and development expense in the Company’s statement of operations and comprehensive loss. During the year ended December 31, 2020, the Company determined that its property and equipment had no future alternative use and recorded an impairment charge of $1,185. The Company recorded an impairment charge of $1,039 for laboratory equipment and furniture and $146 for office equipment to research and development and general and administrative expense, respectively. Accrued and other current liabilities Accrued and other current liabilities consist of the following. December 31, 2019 2020 Accrued expenses $ 318 $ 128 Accrued payroll 58 405 Other 47 — Total accrued expenses and other current liabilities $ 423 $ 533

Neubase Asset Sale

Neubase Asset Sale	9 Months Ended
	Sep. 30, 2021
Neubase Asset Sale [Abstract]
Neubase Asset Sale	4. Neubase asset sale On January 27, 2021, the Company entered into an asset purchase agreement with NeuBase Therapeutics, Inc. (“NeuBase”), whereby the Company agreed to sell all assets relating to its investment in PNAi, including all inventory, machinery, intellectual property, goodwill, and licenses, and NeuBase agreed to assume certain related liabilities. The sale of the Company’s investment in PNAi closed on April 26, 2021. The Company received $796 in cash and 308,635 shares of NeuBase common stock, with a fair market value of $1,759 based on the closing price reported on the Nasdaq Capital Market on the date the sale closed. Of the total NeuBase shares issued to the Company, 162,260 were placed in escrow to secure certain obligations under the asset purchase agreement. In connection with the sale, the Company also assigned certain leases for research and laboratory equipment to NeuBase (see Note 13). The Company recognized a gain of $2,691 on the sale of assets to NeuBase. As of September 30, 2021, there were 54,070 shares eligible for release from escrow. Per the terms of the agreement, the shares may be released from escrow upon the execution of a joint instruction letter.

Non-Marketable Equity Securitie

Non-Marketable Equity Securities	9 Months Ended
	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Non-Marketable Equity Securities	5. Non-marketable The Company has an investment in NeuBase common stock with restrictions on the sale or transfer of the shares. Fair value is determined using alternative pricing sources and models utilizing market observable inputs. The Company reports the restricted equity securities as non-marketable non-current The Company recorded a cumulative net unrealized loss of nine non-marketable Initial cost as of April 26, 2021 $ 1,759 Change in fair value (645 ) Balance as of September 30, 2021 $ 1,114

Convertible Notes

Convertible Notes	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Convertible Notes	6. Convertible notes In March 2020, the Company issued convertible notes to certain existing investors of the Company for cash. The principal amount of the convertible notes was $5,000 in the aggregate with a fixed accrued interest rate of 4% per annum. The convertible notes were either due on or after December 31, 2020, or upon a change of control of the Company, unless earlier converted. No principal or interest was payable prior to maturity as the convertible notes and any accrued interest would automatically convert upon a qualified financing event at a conversion price equal to 85% of the price per share of the qualified financing. Holders also had the option to convert their notes to shares of Series B redeemable convertible stock at a conversion price equal to $4.2926 per share on the maturity date or upon a change of control of the Company, if no qualified financing occurred prior to such date. Due to certain embedded features within the convertible notes, the Company elected to account for the convertible notes under the fair value option. In April and May 2020, the Company issued additional convertible notes to certain existing investors of the Company for cash. The principal amount of the convertible notes was $602 in the aggregate with the same terms as the convertible notes issued in March 2020. In October 2020, the outstanding principal and accrued interest of $134, were automatically converted into 11,404,246 shares of the Company’s Series C redeemable convertible preferred stock in connection with the closing of the Company’s Series C redeemable convertible preferred stock financing (see Note 7) at a conversion price of $0.5030 per share, which was 85% of the $0.5918 original issuance price of the Series C redeemable convertible preferred stock.	4. Convertible notes In March, April, and May 2020, the Company issued convertible notes to certain existing investors of the Company for cash. The principal amount of the convertible notes was $5,602 in the aggregate with a fixed accrued interest rate of 4% per annum. The convertible notes were either due on or after December 31, 2020 or upon a change of control of the Company, unless earlier converted. No principal or interest was payable prior to maturity as the convertible notes and any accrued interest would automatically convert upon a qualified financing event at a conversion price equal to 85% of the price per share of the qualified financing. Holders also had the option to convert their notes to shares of Series B redeemable convertible stock at a conversion price equal to $4.2926 per share on the maturity date or upon a change of control of the Company, if no qualified financing occurred prior to such date. Due to certain embedded features within the convertible notes, the Company elected to account for the convertible notes under the fair value option. The following table provides the changes in the fair value of the convertible notes for the year ended December 31, 2020. Issuance of convertible note s $ 5,539 Change in fair value of convertible notes 1,210 Conversion into Series C redeemable convertible preferred stock (6,749 ) Balance as of December 31, 2020 $ — In October 2020, the outstanding principal, and accrued interest of $134, were automatically converted into 11,404,246 shares of the Company’s Series C redeemable convertible preferred stock in connection with the closing of the Company’s Series C redeemable convertible preferred stock financing (see Note 5) at a conversion price of $0.5030 per share, which was 85% of the $0.5918 original issuance price of the Series C redeemable convertible preferred stock.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Temporary Equity [Abstract]
Redeemable Convertible Preferred Stock	7. Redeemable convertible preferred stock As of December 31, 2020, the Company’s redeemable convertible preferred stock consisted of the following balances. Issue price share Shares Shares issued Carrying Aggregate Series Seed $ 1.01 1,010,456 1,010,456 $ 1,789 $ 1,020 Series Seed-1 1.92 1,787,640 1,787,640 3,718 3,430 Series A 2.15 6,120,111 6,120,111 12,851 13,136 Series B 4.29 5,097,566 5,097,566 21,737 21,882 Series C 0.59 168,756,599 168,756,599 99,481 99,870 Total 182,772,372 182,772,372 $ 139,576 $ 139,338 In October 2020, the Company issued 135,180,800 shares of Series C redeemable convertible preferred stock for a purchase price of $0.5918 per share, payable in cash. Gross proceeds to the Company were $80,000. The In May 2021, immediately prior to the completion of the IPO (see Note 1), all outstanding shares of redeemable convertible preferred stock were automatically converted into 15,774,014 shares of common stock.	5. Redeemable convertible preferred stock As of December 31, 2020, the Company’s redeemable convertible preferred stock consisted of the following balances (in thousands, except share amounts). Issue price Shares authorized Shares outstanding Carrying value Aggregate liquidation preference Series Seed $ 1.01 1,010,456 1,010,456 $ 1,789 $ 1,020 Series Seed-1 1.92 1,787,640 1,787,640 3,718 3,430 Series A 2.15 6,120,111 6,120,111 12,851 13,136 Series B 4.29 5,097,566 5,097,566 21,737 21,882 Series C 0.59 168,756,599 168,756,599 99,481 99,870 Total 182,772,372 182,772,372 $ 139,576 $ 139,338 In October 2020, the Company issued 135,180,800 shares of Series C redeemable convertible preferred stock for a purchase price of $0.5918 per share, payable in cash. Gross proceeds to the Company were $80,000. The Series C redeemable convertible preferred stock financing triggered the automatic conversion of the Company’s outstanding convertible notes into 11,404,246 shares of Series C redeemable convertible preferred stock based on price of $0.5030 per share (85% of the $0.5918 original issuance price of the Series C redeemable convertible preferred stock). In addition, the Company issued 22,171,553 shares of Series C redeemable convertible preferred stock to Ares Trading S.A. (“Ares”), an affiliate of Merck KGaA, Darmstadt, Germany, as the initial payment for the Company’s license of atacicept from Ares (see Note 9). The holders of the Series Seed, Seed-1, Voting On any matter presented to the stockholders of the Company for their action or consideration at any meeting of stockholders of the Company (or by written consent of stockholders in lieu of meeting), each holder of outstanding shares of redeemable convertible preferred stock is entitled to cast the number of votes equal to the number of whole shares of common stock into which the shares of redeemable convertible preferred stock held by such holder are convertible as of the record date for determining stockholders entitled to vote on such matter. Holders of redeemable convertible preferred stock may vote, on an as-converted Dividends Through December 31, 2020, no dividends have been authorized, declared, or paid. The Company may not declare, pay or set aside any dividends on any other class or series of capital stock (other than dividends on shares of common stock payable in shares of common stock) unless the holders of redeemable convertible preferred stock then outstanding first or simultaneously receive a dividend on each outstanding share of redeemable convertible preferred stock in an amount at least equal to (a) in the case of a dividend on common stock or any class or series that is convertible into common stock, that dividend per share to equal the product of (i) the dividend payable on each share of such class or series determined, if applicable, as if all shares of such class or series had been converted into common stock and (ii) the number of shares of common stock issuable upon conversion of such share of redeemable convertible preferred stock, in each case calculated on the record date for determination of holders entitled to receive such dividend or (b) in the case of a dividend on any class or series that is not convertible into common stock, at a rate per share determined by (i) dividing the amount of the dividend payable on each share of such class or series of capital stock by the Original Issuance Price of such class or series of capital stock (subject to appropriate adjustment in the event of any stock dividend, stock split, combination or other similar recapitalization with respect to such class or series) and (ii) multiplying this fraction by an amount equal to the applicable original issue price; provided that, if the Company declares, pays or sets aside, on the same date, a dividend payable to the holders of redeemable convertible preferred stock is calculated based on the dividend on the class or series of capital stock that would result in the highest preferred stock dividend. Conversion Each share of redeemable convertible preferred stock is convertible, at the option of the holder, at any time and from time to time, and without the payment of additional consideration by the holder, into such number of fully paid and nonassessable shares of common stock as is determined by dividing the applicable original issue price by the applicable preferred stock conversion price in effect at the time of conversion. The preferred stock conversion price for each share of redeemable convertible preferred stock is initially equal to the original issue price applicable to such share. Each such initial preferred stock conversion price, and the rate at which shares of redeemable convertible preferred stock may be converted into shares of common stock, is subject to adjustment. No fractional shares of common stock will be issued upon conversion of redeemable convertible preferred stock. In lieu of any fractional shares, the Company will pay cash equal to the fraction multiplied by the fair market value of a share of common stock. Liquidation preference In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company, the holders of shares of Series C redeemable convertible preferred stock then outstanding are entitled to be paid out of the assets of the Company available for distribution to its stockholders, before any payment shall be made to the holders of Series Seed, Series Seed-1, Thereafter, the holders of Series Seed, Series Seed-1, Seed-1, After the payment of all preferential amounts required to be paid to the holders of shares of redeemable convertible preferred stock, the remaining assets of the Company available for distribution to its stockholders will be distributed among the holders of shares of Series C redeemable convertible preferred stock and common stock, pro rata based on the number of shares held by each such holder on an as-converted Redemption The holders of the Company’s redeemable convertible preferred stock have no rights to cause the redemption of their shares outside of a liquidation or winding up of the Company, a change in control, or a sale of substantially all of the Company’s assets (a “deemed liquidation event”). A deemed liquidation event would constitute a redemption event that may be outside of the Company’s control as a result of the preferred stockholders’ control of the Company’s board of directors. Accordingly, the redeemable convertible preferred shares are considered contingently redeemable and are classified as temporary equity on the balance sheets. The carrying value of the redeemable convertible preferred stock has not been adjusted to its redemption value as redemption was not probable as of the balance sheet dates presented. The carrying value of the redeemable convertible preferred stock will be adjusted to its redemption value in the future, if redemption becomes probable. Classification The Company has classified its redeemable convertible preferred stock separate from total stockholders’ deficit in the balance sheets as the redeemable convertible preferred shares are contingently redeemable upon a deemed liquidation event and in that event there is no guarantee that all stockholders would be entitled to receive the same form of consideration. No accretion to redemption value was recorded during the years ended December 31, 2019 and 2020 as a deemed liquidation event was not considered probable.

Common Stock

Common Stock	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Stockholders' Equity Note [Abstract]
Common Stock	8. Common stock As of September 30, 2021, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue 500,000,000 shares of Class A common stock and 14,600,000 shares of Class B common stock, each with a par value of $0.001 per share. Each share of Class A common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Class B common stock is non-voting.	6. Common stock As of December 31, 2020, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue 273,986,920 shares of Class A common stock and 21,593,607 shares of Class B common stock, each with a par value of $0.001 per share. Each share of Class A common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Class B common stock is non-voting.

Stock Compensation

Stock Compensation	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock Compensation	9. Stock compensation In April 2021, the Company adopted the 2021 Employee Stock Purchase Plan (“ESPP”) and the 2021 Equity Incentive Plan (“2021 EIP”), each of which became effective in connection with the IPO. The Company has reserved 220,251 and 2,213,773 shares of Class A common stock for future issuance under the ESPP and 2021 EIP, respectively. The Company may not grant any additional awards under the 2017 Equity Incentive Plan (“2017 EIP”). The 2017 EIP will continue to govern outstanding equity awards granted thereunder. As of September 30, 2021, there were 1,510,665 shares available for issuance under the 2021 EIP. 2017 EIP and 2021 EIP Stock option activity under the 2017 EIP and 2021 EIP was as follows: Number of Weighted- Weighted- (years) Aggregate Balance—December 31, 2020 1,855,507 $ 2.99 9.79 $ 8 Granted 1,188,064 8.98 Exercised (145,805 ) 3.77 Cancelled and forfeited (3,095 ) 9.38 Balance—September 30, 2021 2,894,671 5.43 9.35 $ 34,521 Options exercisable—September 30, 2021 82,944 3.42 8.96 $ 1,155 Vested and expected to vest—September 30, 2021 2,894,671 $ 5.43 9.35 $ 34,521 The aggregate intrinsic value of stock options exercised during the nine months ended September 30, 2021, was $206. The weighted-average grant date fair value of options granted during the nine months ended September 30, 2021, was $6.66 per share. ESPP The ESPP enables eligible employees to purchase shares of the Company’s common stock at the end of each offering period at a price equal to 85% of the fair market value of the shares on the first trading day or the last trading day of the offering period, whichever is lower. Eligible employees generally include all employees. Share purchases are funded through payroll deductions of at least 1% and up to 15% of an employee’s eligible compensation for each payroll period. The number of shares reserved for issuance under the ESPP increase automatically on the first day of each fiscal year, beginning on January 1, 2022, by a number equal to the lesser of 440,502 shares, 1% of the total number of shares of the Company’s capital stock (including all classes of the Company’s common stock) outstanding on the last day of the calendar month prior to the date of the increase, or such lower number of shares. (including no shares) approved by the Company’s board of directors. As of September 30, 2021, no shares have been issued pursuant to the ESPP. The ESPP generally provides for six-month Stock-based compensation expense The following tables summarize the stock-based compensation expense for stock options and restricted stock awards granted to employees and nonemployees that was recorded in the Company’s statements of operations and comprehensive loss for the nine months ended September 30, 2021 and 2020. Nine months ended 2021 2020 Research and development $ 606 $ 4 General and administrative 1,444 184 Total stock-based compensation expense $ 2,050 $ 188 Nine months ended 2021 2020 Employees $ 1,878 $ 182 Nonemployees 172 6 Total stock-based compensation expense $ 2,050 $ 188 As of September 30, 2021, the Company had $10,348 of unrecognized stock-based compensation expense related to unvested stock options and restricted stock awards, which is expected to be recognized over a weighted-average period of approximately 3.15 years. The fair value of stock options granted during the nine months ended September 30, 2021 and 2020 was estimated using the Black-Scholes option pricing model based on the following weighted average assumptions. Nine months ended 2021 2020 Expected term (in years) 5.5 – 6.1 5.5 – 6.1 Expected volatility 75.4% – 76.6% 74.0% – 75.7% Risk-free rate 0.6% – 1.1% 0.4% – 1.7% Dividend yield — — Restricted stock awards In October 2020, in conjunction with the Series C redeemable convertible preferred stock issuance, the Company restricted 49,636 shares of fully issued and outstanding Class A common stock held by the Company’s Chief Executive Officer and founder. The restriction allows the Company to repurchase shares that have not vested. The vesting term of restricted stock is one year. The grant date fair value of the restricted shares was $6.37. The following table summarizes the activity for the Company’s restricted stock for the nine months ended September 30, 2021. Number of Unvested as of December 31, 2020 41,363 Vested (37,226 ) Unvested as of September 30, 2021 4,137 For the nine months ended September 30, 2021, the Company recognized $236 of stock-based compensation expense related to restricted stock awards that vested during the period.	7. Stock compensation 2017 Equity Incentive Plan In 2017, the Company’s Board of Directors adopted the Vera Therapeutics, Inc. 2017 Equity Incentive Plan, which provides for the grant of qualified stock options, nonqualified stock options and other awards, including restricted stock awards, to the Company’s employees, directors, and consultants to purchase up to 286,578 shares of the Company’s Class A common stock. The grants of stock options and restricted stock awards generally vest either (i) over a four-year period, with 25% vesting on the first anniversary of the grant date and on a ratable monthly basis thereafter for the following three years, or (ii) on a ratable monthly basis over a three-year period and expire ten In 2020, the Company’s Board of Directors voted to amend the 2017 Equity Incentive Plan to increase the aggregate authorized number of Class A common stock to be 3,052,169 shares. No other changes were made to the 2017 Equity Incentive Plan. As of December 31, 2020, there were 1,150,088 shares available for future grant under the 2017 Equity Incentive Plan. Stock-based compensation expense The following tables summarize the stock-based compensation expense for stock options and restricted stock awards granted to employees and nonemployees that was recorded in the Company’s statements of operations and comprehensive loss for the years ended December 31, 2019 and 2020. Year ended 2019 2020 Research and development $ 40 $ 4 General and administrative 223 327 Total stock-based compensation expense $ 263 $ 331 Year ended 2019 2020 Employees $ 233 $ 321 Nonemployees 30 10 Total stock-based compensation expense $ 263 $ 331 As of December 31, 2020, the Company had $4,219 of unrecognized stock-based compensation expense related to unvested stock options and restricted stock awards, which is expected to be recognized over a weighted-average period of approximately two years. The fair value of stock options granted during the years ended December 31, 2019 and 2020, was estimated using the Black-Scholes option pricing model based on the following weighted average assumptions. Year ended December 31, 2019 2020 Expected term (in years) 5.5 – 6.0 5.5 – 6.1 Expected volatility 74.0% – 74.3% 86.1% – 92.5% Risk-free rate 2.19% – 2.22% 0.41% – 1.67% Dividend yield — — The following table summarizes the Company’s option activity for the year ended December 31, 2020. Number of options Weighted- average exercise price per share Weighted- average remaining contractual life (years) Aggregate intrinsic value (000s) Balance—December 31, 2019 158,599 $ 7.88 8.19 $ 10 Granted 1,865,091 2.98 Exercised (33,291 ) 8.45 Cancelled and forfeited (134,892 ) 6.75 Balance—December 31, 2020 1,855,507 $ 2.99 9.79 $ 8 Options exercisable—December 31, 2020 146,830 $ 3.84 8.17 $ 1 Unvested and expected to vest—December 31, 2020 1,818,708 $ 2.96 9.92 $ — The aggregate intrinsic value of stock options exercised during the year ended December 31, 2019 and 2020 was $ 6 1 4.06 2.24 Restricted stock awards In October 2020, in conjunction with the Series C redeemable convertible preferred stock issuance, the Company restricted 49,636 one 6.37 Number of Unvested as of December 31, 2019 10,340 Granted 49,636 Vested (18,613 ) Unvested as of December 31, 2020 41,363 For each of the years ended December 31, 2019 and 2020, the Company recognized $ 1 55

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plans	10. Employee benefit plans The Company sponsors a qualified 401(k) defined contribution plan covering eligible employees. Participants may contribute a portion of their annual compensation limited to a maximum annual amount set by the Internal Revenue Service. There were no employer contributions under this plan for the nine months ended September 30, 2021.	8. Employee benefit plans The Company sponsors a qualified 401(k) defined contribution plan covering eligible employees. Participants may contribute a portion of their annual compensation limited to a maximum annual amount set by the Internal Revenue Service. There were no employer contributions under this plan for fiscal 2019 and 2020.

Licenses and Collaborations

Licenses and Collaborations	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Licenses And Collaborations [Abstract]
Licenses and Collaborations	11. Licenses and collaborations Yale University In 2017, PNAi entered into a collaborative research agreement (the “Yale CRA”) and license agreement (the “Yale License Agreement”) with Yale University, which were assigned to the Company upon the closing of the acquisition of PNAi by the Company in 2017. The purpose of the agreements was to fund the Yale University research program in the field of nanoparticle-sized The Yale CRA required funding the labs of collaborators with $1,500 per year for a minimum of two years. The Yale CRA expired in 2019. No payments were made to Yale University pursuant to the Yale CRA during the year ended December 31, 2019 with no future obligation under this commitment. As consideration for the Yale License Agreement, PNAi paid an initial fee of $37 and had the option to issue 5% of the company’s common stock on a fully diluted, as converted basis. If the shares were not issued, the agreement could be terminated at Yale University’s option. After the completion of the merger with PNAi, the Company exercised the option and issued 264,301 shares of common stock to Yale University with a fair value of $100. Under the Yale License Agreement, the Company reimbursed Yale University for patent related expenses. The Company reimbursed Yale University $45 for patent related expenses for the year ended December 31, 2019. The Company and Yale agreed to terminate the Yale License Agreement in 2020 and there are no future payment obligations under the Yale License Agreement. Ares trading S.A. In October 2020, the Company entered into a license agreement with Ares (the “Ares Agreement”), pursuant to which the Company obtained an exclusive worldwide license to certain patents and related know-how As consideration for the Ares Agreement, the Company issued to Ares a non-refundable In December 2020, the Company paid Ares $25,000 in milestone payments upon delivery and initiation of the transfer of specified information and materials. The Company is obligated to pay Ares aggregate milestone payments of up to $176,500 upon the achievement of specified BLA filing or regulatory approval milestones and up to $515,000 upon the achievement of specified commercial milestones. The non-refundable Ares is performing manufacturing technology and know-how Commencing on the first commercial sale of licensed products, the Company is obligated to pay Ares tiered royalties of low double-digit to mid-teen product-by- country-by-country	9. Licenses and collaborations Carnegie Mellon University In 2012, PNAi entered into a license agreement with Carnegie Mellon University (as amended, the “CMU License Agreement”), which was assigned to the Company upon the closing of the Company’s acquisition of PNA in 2017. The CMU License Agreement provided exclusive, worldwide rights to certain patents and know-how If the Company were to sublicense the technology licensed pursuant to the CMU License Agreement, the Company would be obligated to pay CMU a percentage ranging in the low double-digits of specified sublicensing income received, subject to reduction for a specified percentage of sublicensing income payments above a specified threshold that the Company may be obligated to pay other third parties. The Company did not achieve any of the development or sales milestones. Accordingly, no royalty or development milestone payments were made nor required to be made under this agreement. Yale university In 2017, PNAi entered into a collaborative research agreement (the “Yale CRA”) and license agreement (the “Yale License Agreement”) with Yale University, which were assigned to the Company upon the closing of the acquisition of PNAi by the Company in 2017. The purpose of the agreements was to fund the Yale University research program in the field of nanoparticle-sized The Yale CRA required funding the labs of collaborators with $1,500 per year for a minimum of two years. The Yale CRA expired in 2019. No payments were made to Yale University pursuant to the Yale CRA during the year ended December 31, 2019, with no future obligation under this commitment. As consideration for the Yale License Agreement, PNAi paid an initial fee of $37 and had the option to issue 5% of the company’s common stock on a fully diluted, as converted basis. If the shares were not issued, the agreement could be terminated at Yale University’s option. After the completion of the merger with PNAi, the Company exercised the option and issued 264,301 shares of common stock to Yale University with a fair value of $100. Under the Yale License Agreement, the Company reimbursed Yale University for patent related expenses. The Company reimbursed Yale University $45 for patent related expenses for the year ended December 31, 2019. The Company and Yale agreed to terminate the Yale License Agreement in 2020 and there are no future payment obligations under the Yale License Agreement. Ares trading S.A. In October 2020, the Company entered into a license agreement with Ares (the “Ares Agreement”), pursuant to which the Company obtained an exclusive worldwide license to certain patents and related know-how As consideration for the Ares Agreement, the Company issued to Ares a non-refundable As of December 31, 2020, the Company has paid Ares $25,000 in milestone payments upon delivery and initiation of the transfer of specified information and materials. The Company is obligated to pay Ares aggregate milestone payments of up to $176,500 upon the achievement of specified BLA filing or regulatory approval milestones and up to $515,000 upon the achievement of specified commercial milestones. The non-refundable Commencing on the first commercial sale of licensed products, the Company is obligated to pay Ares tiered royalties of low double-digit to mid-teen product-by- country-by-country

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income taxes	10. Income taxes The provision for income taxes for the years ended December 31, 2019 and 2020 consisted of the following. December 31, 2019 2020 Current: Federal $ — $ — State 1 1 Total current provision 1 1 Total deferred provision — — Total provision for income taxes $ 1 $ 1 A reconciliation of the provision for income taxes computed using the U.S. statutory federal income tax rate compared to the income tax provision included in the statement of operations and comprehensive loss is as follows. Year ended 2019 2020 Tax at U.S. statutory rate on income before income taxes $ (2,409 ) $ (11,217 ) Change in valuation allowanc e 2,999 10,986 Research and development credits (635 ) 122 State taxes 1 1 Other 45 109 Total provision for income taxes $ 1 $ 1 Deferred tax assets and liabilities are determined based on the differences between financial reporting and income tax bases of assets and liabilities, as well as net operating loss carryforwards and are measured using the enacted tax rates and laws in effect when the differences are expected to reverse. The significant components of the Company’s deferred tax assets and liabilities are as follows. December 31, 2019 2020 Deferred tax assets: Net operating loss carryforwards $ 7,267 $ 9,681 Research and other tax credits 2,603 2,652 Property and equipment — 25 Intangible asset s 27 8,019 Stock-based compensation 63 119 Reserves and accruals 108 554 Total deferred tax assets 10,068 21,050 Valuation allowance (10,002 ) (21,050 ) Total deferred tax assets, net of valuation allowance $ 66 $ — Deferred tax liabilities: Property and equipment (66 ) — Total deferred tax liabilities (66 ) — Net deferred tax assets $ — $ — As of December 31, 2020, the Company has federal and state net operating loss carryforwards of $44,007 and $3,531, respectively, of which $10,246 of federal net operating loss carryforwards and $3,531 of state net operating carryforwards will begin expiring in the year 2032 and 2036, respectively, if not utilized. The Company also has $33,761 of federal net operating loss carryforwards as of December 31, 2020 that does not expire as a result of recent tax law changes. The Company has $2,159 and $1,156 of federal and state research and development tax credit carryforwards, which will begin to expire in the year of 2037 and 2033, respectively. Utilization of the federal and state net operating loss and tax credit carryforwards may be subject to a substantial annual limitation due to the “change in ownership” provisions of the Internal Revenue Code of 1986. The annual limitation may result in the expiration of net operating losses and credits before utilization. The Company has not performed an analysis to determine if such ownership changes have occurred. An analysis will be performed prior to recognizing the benefits of any losses or credits in the financial statements. Management assesses the available positive and negative evidence to estimate if sufficient future taxable income will be generated to use the existing deferred tax assets. Based on the weight of all evidence including a history of operating losses, management has determined that it is not more likely than not that the net deferred tax assets will be realized. A valuation allowance of $10,002 and $21,050 for the year ended December 31, 2019 and 2020 has been established to offset the deferred tax assets as realization of such assets is uncertain. The Company accounts for income taxes in accordance with authoritative accounting guidance which states the impact of an uncertain income tax position is recognized at the largest amount that is “more likely than not” to be sustained upon audit by the relevant taxing authority. An uncertain tax position will not be recognized if it has less than a 50% likelihood of being sustained. As of December 31, 2019 and 2020, the Company had no material unrecognized tax benefits. No significant interest or penalties were recorded during the years ended December 31, 2019 and 2020. We are currently unaware of any uncertain tax positions that could result in significant additional payments, accruals, or other material deviation in this estimate over the next 12 months. The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by the United States and state jurisdictions where applicable. There are currently no pending income tax examinations. The Company’s tax years from inception to 2020 are subject to examination by the federal and various state tax authorities due to the carryforward of unutilized net operating losses. The Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was enacted March 27, 2020. The CARES Act provided for various payroll tax incentives, changes to net operating loss carryback and carryforward rules, business interest expense limitation increases, and bonus depreciation on qualified improvement property. Additionally, the Consolidated Appropriations Act of 2021, which was signed on December 27, 2020, provided additional COVID relief provisions for businesses. The Company has evaluated the impact of both statutes and has determined that any impact is not material to its financial statements.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. Commitments and contingencies The aggregate future minimum lease payments for operating leases as of September 30, 2021, are as follows. Operating Sublease 2021 (remaining 3 months) $ 587 $ (462 ) 2022 2,381 (1,901 ) 2023 2,458 (1,964 ) 2024 2,537 (2,029 ) 2025 1,953 (1,569 ) Total payments $ 9,916 $ (7,925 ) (1) Future minimum lease payments include repayment of outstanding restructuring liabilities. Facilities leases In April 2015, PNAi entered a lease for approximately 3,800 square feet of office and laboratory space for a term of 39 months in Woburn, Massachusetts. In January 2018, the Company elected to renew this lease for three years, beginning in August 2018. This lease expired in July 2021. In April 2018, the Company entered into a lease for approximately 24,606 square feet of office and life science research space, which commenced on October 1, 2018, when the Company obtained control of the rented space for a term of 84 months in South San Francisco, California (“the South San Francisco Lease”). In connection with the South San Francisco Lease, the Company maintains a letter of credit issued to the lessor in the amount of $293, which is secured by restricted cash that is classified as noncurrent based on the term of the underlying lease. The Company’s total future minimum commitment due pursuant to the South San Francisco Lease is $9,916 as of September 30, 2021. In November 2020, the Company entered into a non-cancellable The Company recorded rent expense totaling $1,605 for the nine months ended September 30, 2020. No rent expense was recorded for the nine months ended September 30, 2021. Equipment lease The Company had certain leases on research and laboratory equipment which were assigned to a certain third party as of September 30, 2021. The Company recorded rent expense totaling $256 for the nine months ended September 30, 2020. No rent expense was recorded for the nine months ended September 30, 2021.	11. Commitments and contingencies The aggregate future minimum lease payments for operating leases as of December 31, 2020, are as follows. Year ending December 31, Operating leases(1) Sublease income 2021 $ 2,838 $ (1,746 ) 2022 2,295 (1,804 ) 2023 2,351 (1,864 ) 2024 2,221 (1,926 ) 2025 2,075 (1,483 ) Total payments $ 11,780 $ (8,823 ) (1) Future minimum lease payments include repayment of outstanding restructuring liabilities Facilities leases In April 2015, PNAi entered a lease for approximately 3,800 square feet of office and laboratory space for a term of 39 months in Woburn, Massachusetts. In January 2018, the Company elected to renew this lease for three years, beginning in August 2018. In connection with the lease, the Company maintains a letter of credit issued to the lessor in the amount of $50, which is secured by restricted cash that is classified as noncurrent based on the term of the underlying lease. In April 2018, the Company entered into a lease for approximately 24,606 square feet of office and life science research space, which commenced on October 1, 2018, when the Company obtained control of the rented space for a term of 84 months in South San Francisco, California (the South San Francisco Lease). In connection with the lease, the Company maintains a letter of credit issued to the lessor in the amount of $293, which is secured by restricted cash that is classified as noncurrent based on the term of the underlying lease. The Company’s total future minimum commitment due pursuant to the South San Francisco Lease is $11,128 as of December 31, 2020. In November 2020, the Company entered into a non-cancellable The Company recorded rent expense totaling $1,726 and $2,089 for the years ended December 31, 2019 and 2020, respectively. Equipment lease The Company has certain leases on research and laboratory equipment with total future minimum commitments of $581 as of December 31, 2020.

Restructuring and Related Activ

Restructuring and Related Activities	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Restructuring and Related Activities [Abstract]
Restructuring and Related Activities	13. Restructuring and related activities During the year ended December 31, 2019, the Company completely vacated its leased facilities in Woburn, Massachusetts. In connection with vacating the leased spaces, the Company recorded a discounted lease-related restructuring liability, which was calculated as the present value of the estimated future facility costs for which the Company would obtain no future economic benefit over the term of the lease, reduced for actual or estimated sublease rentals. In July 2020, the Company initiated a restructuring plan to reduce operating expense as a result of the disposal of PNAi technology. The restructuring plan included reducing the number of employees, vacating leased facilities, and ceasing use of leased equipment. As a result of this restructuring plan, the Company completely vacated its leased facilities in South San Francisco, California, which was subleased to a third party in November 2020, and returned certain leased equipment to the lessor. The Company recorded a discounted lease-related restructuring liability of $2,228 and $768 for the abandonment of the leased facilities and equipment, which was calculated as the present value of the estimated future lease costs for which the Company would obtain no future economic benefit over the term of the leases. In addition, the Company recognized restructuring liability of $321 related to severance and other employee termination costs related to the reduction in the number of employees. The activity related to the restructuring liabilities for the nine months ended September 30, 2021, is as follows. Lease-related Employee Total Balance as of December 31, 2020 2,584 12 2,596 Accretion 116 — 116 Provision 28 — 28 Cash payments (863 ) (12 ) (875 ) Lease assignment to NeuBase (136 ) — (136 ) Balance as of September 30, 2021 $ 1,729 $ — $ 1,729	12. Restructuring and related activities During the year ended December 31, 2019, the Company completely vacated its leased facilities in Woburn, Massachusetts. In connection with vacating the leased spaces, the Company recorded a discounted lease-related restructuring liability, which was calculated as the present value of the estimated future facility costs for which the Company would obtain no future economic benefit over the term of the lease, reduced for actual or estimated sublease rentals. In July 2020, the Company initiated a restructuring plan to reduce operating expense as a result of the disposal of PNAi technology. The restructuring plan included reducing the number of employees, vacating leased facilities, and ceasing use of leased equipment. As a result of this restructuring plan, the Company completely vacated its leased facilities in South San Francisco, California, which was subleased to a third party in November 2020, and returned certain leased equipment to the lessor. The Company recorded a discounted lease-related restructuring liability of $2,228 and $768 for the abandonment of the leased facilities and equipment, which was calculated as the present value of the estimated future lease costs for which the Company would obtain with no future economic benefit over the term of the leases. In addition, the Company recognized restructuring liability of $321 related to severance and other employee termination costs related to the reduction in the number of employees. The Company expects this restructuring plan to be completed in 2021. The activity related to the restructuring liabilities for the years ended December 31, 2019 and 2020 are as follows. Lease-related exit costs Employee termination Total Restructuring costs $ 261 $ — $ 261 Accretion 14 — 14 Cash payments (102 ) — (102 ) Balance as of December 31, 2019 173 — 173 Restructuring costs 2,996 321 3,317 Accretion 24 — 24 Cash payments (609 ) (309 ) (918 ) Balance as of December 31, 2020 $ 2,584 $ 12 $ 2,596

Net Loss Per Share Attributable

Net Loss Per Share Attributable To Common Stockholders	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
Net Loss Per Share Attributable To Common Stockholders	14. Net loss per share attributable to common stockholders The following outstanding potentially dilutive shares were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented, because including them would have been anti-dilutive (on an as-converted Nine months ended 2021 2020 Redeemable convertible preferred stock — 1,209,599 Class A common stock options issued and outstanding 2,894,671 164,588 Unvested restricted stock awards 4,137 — Total 2,898,808 1,374,187	13. Net loss per common share The following outstanding potentially dilutive shares were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented, because including them would have been anti-dilutive (on an as-converted December 31, 2019 2020 Redeemable convertible preferred stock 1,209,599 15,774,014 Class A common stock options issued and outstanding 158,599 1,855,507 Unvested restricted stock awards 10,340 41,363 Total 1,378,538 17,670,884

Related Party Transactions

Related Party Transactions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	1 In October 2018, the Company entered into a sublease agreement for a portion of its South San Francisco office space, the term for which commenced on December 7, 2018. The Chief Executive Officer of the sublessor is a member of the Company’s board of directors. The initial sublease was established for approximately 400 square feet of space. Prior to the initial expiration of the sublease in April 2019, the space was expanded to approximately 3,700 square feet with the term of the lease extended for an additional two years. The monthly rent charged by the Company to the subtenant is subject to escalating rent payments according to the terms of the Company’s lease agreement, and the subtenant is required to reimburse the Company for monthly facility operating expenses based on its proportionate share of total square footage pursuant to the lease. The Company’s lease agreement provides that 50% of any profit resulting from the excess of the amount collected from the subtenant less the sum of monthly rent, operating expenses and reimbursement of direct expenditures made by the Company in order to arrange and maintain the sublease is to be shared with the lessor. To date, no profit has been realized on the sublease arrangement as the monthly collections from the subtenant are equivalent to the Company’s cost of rent, operating expense and recovery of professional fees to arrange the sublease. In June 2020, the sublease agreement was terminated. During the nine months ended September 30, 2020, the Company recognized $160 of sublease income under this agreement, which was recorded as a reduction to the Company’s rent expense. In October 2020, the Company entered into the Ares Agreement with Ares, pursuant to which the Company obtained an exclusive worldwide license to certain patents and related know-how	14. Related party transactions In October 2018, the Company entered into a sublease agreement for a portion of its South San Francisco office space, the term for which commenced on December 7, 2018. The Chief Executive Officer of the sublessor is a member of the Company’s board of directors. The initial sublease was established for approximately 400 square feet of space. Prior to the initial expiration of the sublease in April 2019, the space was expanded to approximately 3,700 square feet with the term of the lease extended for an additional two years. The monthly rent charged by the Company to the subtenant is subject to escalating rent payments according to the terms of the Company’s lease agreement, and the subtenant is required to reimburse the Company for monthly facility operating expenses based on its proportionate share of total square footage pursuant to the lease. The Company’s lease agreement provides that 50% of any profit resulting from the excess of the amount collected from the subtenant less the sum of monthly rent, operating expenses and reimbursement of direct expenditures made by the Company in order to arrange and maintain the sublease is to be shared with the lessor. To date, no profit has been realized on the sublease arrangement as the monthly collections from the subtenant are equivalent to the Company’s cost of rent, operating expense and recovery of professional fees to arrange the sublease. In June 2020, the sublease agreement was terminated. During the years ended December 31, 2019 and 2020, the Company recognized $279 and $160, respectively, of sublease income under this agreement, which was recorded as a reduction to the Company’s rent expense. In October 2020, the Company entered into the Ares Agreement with Ares, pursuant to which the Company obtained an exclusive worldwide license to certain patents and related know-how

Subsequent Events

Subsequent Events	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent events In November 2021, the Company entered into a lease agreement for approximately 5,000 square feet of office space in Brisbane, California. The term of the lease is three years, and rent will be approximately $288 for the first year with scheduled annual 3% increases. The lease includes renewal options for the Company. In December 2021, the Company entered into an asset purchase agreement (the “Amplyx Agreement”) with Amplyx Pharmaceuticals, Inc. (“Amplyx”), a wholly owned subsidiary of Pfizer Inc. (“Pfizer”), under which it acquired MAU868, a monoclonal antibody that was under development by Amplyx for the treatment of BK virus infections. MAU868 is subject to a license agreement between Amplyx and Novartis Pharma AG, as successor in interest to Novartis International Pharmaceutical AG (“Novartis”). Under the Amplyx Agreement, the Company obtained a worldwide, exclusive license from Novartis to develop, manufacture and commercialize MAU868. The Company also assumed certain liabilities of Amplyx. In partial consideration for the Amplyx Agreement, the Company made an upfront initial payment of $5.0 million to Amplyx. The Company may also be obligated to make certain milestone payments to Amplyx in an aggregate amount up to $7.0 million based on certain regulatory milestones, and may be required to pay Amplyx low-single mid- In December 2021, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with Oxford Finance LLC (the “Lender”) as lender and collateral agent. The Loan Agreement provides for a term loan in an aggregate maximum principal amount of $50.0 million (the “Loan”), of which $5.0 million was funded in December 2021, and the balance of which is available to be drawn at the Company’s option in minimum draws of $5.0 million during 2022. The Loan matures in December 2026, which may be extended by 12 months subject to certain clinical data milestones. The Company is required to make monthly interest-only payments for 48 months, which may be extended to 60 months if the final maturity date is extended. Initially, the Loan bears interest at 8.254%, with a floating interest rate tied to LIBOR. The Company is permitted to prepay the loan, subject to certain conditions. Upon the maturity date or prepayment of the Loan, the Company is required to make a final payment equal to 5.0% (or 7.0% if the maturity date is extended) of the aggregate principal amount of the Loan. The Loan Agreement does not contain any financial covenants and the Loan is secured by the Company’s assets.	15A. Subsequent events On January 27, 2021, the Company entered into an asset purchase agreement with Neubase Therapeutics, Inc. (“Neubase”), whereby the Company agreed to sell all assets relating to its investment in PNAi, including all inventory, machinery, intellectual property, goodwill and licenses, including the CMU License Agreement, and Neubase agreed to assume certain related liabilities. 15B. Subsequent events On May 7, 2021, the Company filed a certificate of amendment to its fourth amended and restated certificate of incorporation to effect a 11.5869-for-one stock. Adjustments corresponding to the reverse stock split were made to the ratio at which the Company’s redeemable convertible preferred stock will convert into Class A common stock. Accordingly, all share and per share amounts related to Class A common stock, stock options and restricted stock awards for all periods presented in the accompanying financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect the reverse stock split.

Events (unaudited) subsequent t

Events (unaudited) subsequent to the date of the report of the independent registered public accounting firm	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Events (unaudited) subsequent to the date of the report of the independent registered public accounting firm	16. Events (unaudited) subsequent to the date of the report of the independent registered public accounting firm The sale relating to the Company’s investment in PNAi closed on April 26, 2021. The Company received $796 in cash and 308,635 shares of Neubase common stock, with a fair market value of $1,759 based on the closing price reported on Nasdaq on the date the sale closed. Of the total Neubase shares issued to the Company, 162,260 were placed in escrow to secure certain obligations under the agreement.

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The accompanying unaudited condensed financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. The U.S. dollar is the Company’s functional and reporting currency.	Basis of presentation The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The U.S. dollar is the Company’s functional and reporting currency.
Unaudited interim condensed financial statements	Unaudited interim condensed financial statements The accompanying condensed balance sheet as of September 30, 2021, and condensed statements of operations and comprehensive loss, condensed statements of cash flows, and condensed statements of redeemable convertible preferred stock and stockholders’ equity (deficit) for the nine months ended September 30, 2021 and 2020, are unaudited. The balance sheet as of December 31, 2020, was derived from the audited financial statements as of and for the year ended December 31, 2020. The unaudited condensed financial statements have been prepared on a basis consistent with the audited annual financial statements as of and for the year ended December 31, 2020 and in the opinion of management, reflect all adjustments consisting solely of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2021, and the condensed results of its operations and its cash flows for the nine months ended September 30, 2021. The financial data and other information disclosed in these notes related to the nine months ended September 30, 2021, are also unaudited. The condensed results of operations for the nine months ended September 30, 2021, are not necessarily indicative of the results to be expected for the full year ending December 31, 2021, or any other period. These unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2020, included in the Company’s final prospectus dated May 13, 2021, for the IPO filed with the SEC on May 17, 2021, pursuant to Rule 424(b)(4) relating to the Company’s Registration Statement on Form S-1, No. 333-255492).
Reclassification		Reclassification Certain reclassification of prior period amounts related to restructuring activities has been made to conform to the current year presentation.
Emerging growth company status	Emerging growth company status The Company is an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with certain new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (1) is no longer an emerging growth company or (2) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these unaudited condensed financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.	Emerging growth company status The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with certain new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (1) is no longer an emerging growth company or (2) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.
Use of estimates	Use of estimates The preparation of the Company’s unaudited condensed financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the unaudited condensed financial statements and the reported amounts of expenses during the reporting period. Management estimates that affect the reported amounts of assets and liabilities include the accrual of research and development expenses, restructuring liabilities, fair value of common stock and stock-based compensation expense, and the valuation allowance for deferred tax assets. The Company evaluates and adjusts its estimates and assumptions on an ongoing basis using historical experience and other factors. Actual results could differ materially from those estimates.	Use of estimates The preparation of the Company’s financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Management estimates that affect the reported amounts of assets and liabilities include useful lives of fixed and intangible assets, the accrual of research and development expenses, restructuring liabilities, fair value of common stock and stock-based compensation expense, and the valuation allowance for deferred tax assets. The Company evaluates and adjusts its estimates and assumptions on an ongoing basis using historical experience and other factors. Actual results could differ materially from those estimates.
Segment information		Segment information The Company operates as a single operating segment. The Company’s chief operating decisionmaker, its Chief Executive Officer, manages the Company’s entire operations as a whole for the purposes of allocating resources, making operating decisions and evaluating financial performance.
Deferred offering costs	Deferred offering costs Deferred offering costs consisting of legal, accounting and filing fees relating to the IPO are capitalized. The deferred offering costs were offset against the Company’s IPO proceeds upon the closing of the IPO.
Concentrations of credit risk and other risks and uncertainties	Concentrations of credit risk and other risks and uncertainties Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains bank deposits in a federally insured financial institution and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of default by the financial institution holding its cash and cash equivalents to the extent recorded in the balance sheet. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s current and potential future product candidates, uncertainty of market acceptance of the Company’s product candidates, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals or sole-source suppliers. The Company’s product candidates require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed, or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.	Concentrations of credit risk and other risks and uncertainties Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains bank deposits in a federally insured financial institution and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of default by the financial institution holding its cash and cash equivalents to the extent recorded in the balance sheet. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty of results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s current and potential future product candidates, uncertainty of market acceptance of the Company’s product candidates, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals or sole-source suppliers. The Company’s product candidates require approvals from the U.S. Food and Drug Administration and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed, or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.
Impact of the COVID-19 pandemic	Impact of the COVID-19 The COVID-19 COVID-19 COVID-19 COVID-19 COVID-19 operations and development timelines and plans, including the resulting impact on expenditures and capital needs, remains uncertain.	Impact of the COVID-19 The COVID-19 COVID-19 COVID-19 COVID-19 COVID-19
Cash and cash equivalents	Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Cash equivalents consist of money market funds and are stated at fair value.	Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Cash equivalents consist of money market funds and are stated at fair value.
Restricted cash	Restricted cash Restricted cash represents cash held by a financial institution as collateral for a letter of credit securing its operating lease for office and laboratory space and as collateral for a credit card, which are classified within current and non-current	Restricted cash Restricted cash represents cash held by a financial institution as collateral for a letter of credit securing its operating lease for office and laboratory space and as collateral for a credit card, which are classified within current and non-current
Comprehensive loss	Comprehensive loss Comprehensive loss consists of net loss and other gains and losses affecting redeemable convertible preferred stock and stockholders’ equity (deficit) that, under U.S. GAAP, are excluded from net loss. The Company has no items of other comprehensive loss for the nine months ended September 30, 2021 and 2020. As such, net loss equals comprehensive loss.	Comprehensive loss Comprehensive loss consists of net loss and other gains and losses affecting redeemable convertible preferred stock and stockholders’ deficit that, under U.S. GAAP, are excluded from net loss. The Company has no items of other comprehensive loss for the years ended December 31, 2019 and 2020. As such, net loss equals comprehensive loss.
Property and equipment, net		Property and equipment, net Property and equipment are recorded at cost, less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset category, for which each category the useful life is estimated at five years. Leasehold improvements are capitalized and amortized over the shorter of the lease term or the estimated useful life of the related asset. Expenditures for repairs and maintenance of assets are charged to expense as incurred, whereas major improvements are capitalized as additions to property and equipment. Amortization of assets under capital leases is included in depreciation expense. Upon retirement or sale, the cost and related accumulated depreciation of assets disposed of are removed from the accounts and any resulting gain or loss is reflected in the statement of operations and comprehensive loss.
Impairment of long-lived assets		Impairment of long-lived assets The Company reviews its long-lived assets, including property and equipment and intangible assets, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount. The impairment loss, if recognized, would be based on the excess of the carrying value of the impaired asset over its respective fair value. During the years ended December 31, 2019 and 2020, the Company recorded asset impairments totaling $10 and $1,185, respectively, on certain intangible assets and certain laboratory and office equipment (see Note 3).
Research and development costs	Research and development costs Research and development costs are expensed as incurred and consist primarily of employees’ salaries and related benefits, including stock-based compensation and termination expenses for employees engaged in research and development efforts, allocated overhead including rent, depreciation, information technology and utilities, contracted services, license fees, and external expenses to conduct and support the Company’s operations that are directly attributable to the Company’s research and development efforts. Payments made to third parties under these arrangements in advance of the performance of the related services by the third parties are recorded as prepaid expenses until the services are rendered. Costs incurred in obtaining technology licenses including upfront and milestone payments incurred under the Company’s licensing agreements are recorded as expense in the period in which they are incurred, provided that the licensed technology, method or process has no alternative future uses other than for the Company’s research and development activities.	Research and development costs Research and development costs are expensed as incurred and consist primarily of employees’ salaries and related benefits, including stock-based compensation and termination expenses for employees engaged in research and development efforts, allocated overhead including rent, depreciation, information technology and utilities, contracted services, license fees, and external expenses to conduct and support the Company’s operations that are directly attributable to the Company’s research and development efforts. Payments made to third parties under these arrangements in advance of the performance of the related services by the third parties are recorded as prepaid expenses until the services are rendered. Costs incurred in obtaining technology licenses including upfront and milestone payments incurred under the Company’s licensing agreements are recorded as expense in the period in which they are incurred, provided that the licensed technology, method or process has no alternative future uses other than for the Company’s research and development activities.
Research contract costs and accruals	Research contract costs and accruals The Company enters into various research and development and other agreements with commercial firms, researchers, and others for provisions of goods and services from time to time. These agreements are generally cancellable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company’s estimates.	Research contract costs and accruals The Company enters into various research and development and other agreements with commercial firms, researchers, and others for provisions of goods and services from time to time. These agreements are generally cancellable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company’s estimates.
Redeemable convertible preferred stock	Redeemable convertible preferred stock The Company records all shares of redeemable convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The carrying value of the Company’s redeemable convertible preferred stock is adjusted to reflect dividends if and when declared by the Company’s board of directors. No dividends have been declared by the board of directors since inception. The Company classifies its redeemable convertible preferred stock separate from total stockholders’ equity (deficit), as the redemption of such stock is not solely under the control of the Company.	Redeemable convertible preferred stock The Company records all shares of redeemable convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The carrying value of the Company’s redeemable convertible preferred stock is adjusted to reflect dividends if and when declared by the Company’s board of directors. No dividends have been declared by the board of directors since inception. The Company classifies its redeemable convertible preferred stock separate from total stockholders’ deficit, as the redemption of such stock is not solely under the control of the Company.
Stock-based compensation	Stock-based compensation The Company recognizes compensation expense based on estimated fair values for all stock-based payment awards made to the Company’s employees, nonemployee directors and consultants that are expected to vest. The valuation of stock option awards is determined at the date of grant using the Black-Scholes option pricing model. The Black-Scholes option pricing model requires the Company to make assumptions and judgements about the inputs used in the calculations, such as the fair value of the common stock, expected term, expected volatility of the Company’s common stock, risk-free interest rate and expected dividend yield. The valuation of restricted stock awards is measured by the fair value of the Company’s common stock on the date of the grant. For all stock options granted, the Company calculated the expected term using the simplified method (derived from the average midpoint between the weighted average vesting period and the contractual term of the award) for “plain vanilla” stock option awards, as the Company has limited historical information to develop expectations about future exercise patterns and post vesting employment termination behavior. The estimate of expected volatility is based on comparative companies’ volatility. The risk-free rate is based on the yield available on United States Treasury zero-coupon The fair value of the shares of common stock underlying the stock options has historically been determined by the board of directors with the assistance of management and input from an independent third-party valuation firm, as there was no public market for the common stock. The board of directors determined the fair value of the Company’s common stock by considering a number of objective and subjective factors, including the valuation of comparable companies, sales of redeemable convertible preferred stock, the Company’s operating and financial performance, the lack of liquidity of common stock, and general and industry specific economic outlook, amongst other factors. The Company records compensation expense for service-based awards on a straight-line basis over the requisite service period, which is generally the vesting period of the award. The amount of stock-based compensation expense recognized during a period is based on the value of the portion of the awards that are ultimately expected to vest.	Stock-Based compensation The Company recognizes compensation expense based on estimated fair values for all stock-based payment awards made to the Company’s employees, nonemployee directors and consultants that are expected to vest. The valuation of stock option awards is determined at the date of grant using the Black-Scholes option pricing model. The Black-Scholes option pricing model requires the Company to make assumptions and judgements about the inputs used in the calculations, such as the fair value of the common stock, expected term, expected volatility of the Company’s common stock, risk-free interest rate and expected dividend yield. The valuation of restricted stock awards is measured by the fair value of the Company’s common stock on the date of the grant. For all stock options granted, the Company calculated the expected term using the simplified method (derived from the average midpoint between the weighted average vesting period and the contractual term of the award) for “plain vanilla” stock option awards, as the Company has limited historical information to develop expectations about future exercise patterns and post vesting employment termination behavior. The estimate of expected volatility is based on comparative companies’ volatility. The risk-free rate is based on the yield available on United States Treasury zero-coupon The fair value of the shares of common stock underlying the stock options has historically been determined by the board of directors with the assistance of management and input from an independent third-party valuation firm, as there was no public market for the common stock. The board of directors determines the fair value of the Company’s common stock by considering a number of objective and subjective factors, including the valuation of comparable companies, sales of redeemable convertible preferred stock, the Company’s operating and financial performance, the lack of liquidity of common stock, and general and industry specific economic outlook, amongst other factors. The Company records compensation expense for service-based awards on a straight-line basis over the requisite service period, which is generally the vesting period of the award. The amount of stock-based compensation expense recognized during a period is based on the value of the portion of the awards that are ultimately expected to vest.
Income taxes	Income taxes The Company did not record an income tax provision for the nine months ended September 30, 2021 and 2020 as net operating losses have been incurred since inception. The net deferred tax assets generated from net operating losses are fully offset by a valuation allowance.	Income taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step more-likely-than-not be recognized is the largest amount that is more likely than not of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax allowance, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Net loss per share attributable to common stockholders	Net loss per share attributable to common stockholders Net loss per share of common stock is computed using the two-class The Company’s participating securities include the Company’s redeemable convertible preferred stock, as the holders were entitled to receive noncumulative dividends on a pari passu basis in the event that a dividend is paid on common stock. The Company also considers any shares issued on the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable two-class Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, adjusted for outstanding shares that are subject to repurchase. Diluted net loss per share is computed by giving effect to all potentially dilutive securities outstanding for the period using the treasury stock method or the if-converted	Net loss per share attributable to common stockholders Net loss per share of common stock is computed using the two-class The Company’s participating securities include the Company’s redeemable convertible preferred stock, as the holders are entitled to receive noncumulative dividends on a pari passu basis in the event that a dividend is paid on common stock. The Company also considers any shares issued on the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable two-class Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, adjusted for outstanding shares that are subject to repurchase. Diluted net loss per share is computed by giving effect to all potentially dilutive securities outstanding for the period using the treasury stock method or the if-converted
Leases	Leases The Company leases office and laboratory space under operating leases and laboratory equipment under capital leases. Leases for which the Company assumes substantially all risks and rewards incidental to ownership of the leased assets are classified as capital leases. The leased assets and the corresponding lease liabilities (net of interest charges) are recognized on the balance sheet as property and equipment, based on the cost of the equipment, and borrowings, respectively, at the inception of the related lease. Each lease payment is apportioned between the reduction of the outstanding lease liability and the related interest expense. The interest expense is recorded on a basis that reflects a constant periodic rate of interest on the outstanding finance lease liability. Leases for which substantially all risks and rewards incidental to ownership are retained by the lessors are classified as operating leases. Payments made under operating leases (net of any incentive received from the lessors) are recorded on a straight-line basis over the period of the lease.	Leases The Company leases office and laboratory space under operating leases and laboratory equipment under capital leases. Leases for which the Company assumes substantially all risks and rewards incidental to ownership of the leased assets are classified as capital leases. The leased assets and the corresponding lease liabilities (net of interest charges) are recognized on the balance sheet as property and equipment, based on the cost of the equipment, and borrowings, respectively, at the inception of the related lease. Each lease payment is apportioned between the reduction of the outstanding lease liability and the related interest expense. The interest expense is recorded on a basis that reflects a constant periodic rate of interest on the outstanding finance lease liability. Leases for which substantially all risks and rewards incidental to ownership are retained by the lessors are classified as operating leases. Payments made under operating leases (net of any incentive received from the lessors) are recorded on a straight-line basis over the period of the lease.
Restructuring costs	Restructuring costs Restructuring costs primarily consist of contract termination costs related to leases and employee termination costs. The Company recognizes restructuring charges when the liability has been incurred. Key assumptions in determining the restructuring costs include the terms and payments that may be negotiated to terminate certain contractual obligations, cease use date of leased property and equipment, and the timing of employees leaving the Company. Accretion expenses related to restructuring costs are included in general and administrative expenses.	Restructuring costs Restructuring costs primarily consist of contract termination costs related to leases and employee termination costs. The Company recognizes restructuring charges when the liability has been incurred. Key assumptions in determining the restructuring costs include the terms and payments that may be negotiated to terminate certain contractual obligations, cease use date of leased property and equipment, and the timing of employees leaving the Company. Accretion expenses related to restructuring costs are included in general and administrative expenses.
Fair value option	Fair value option The convertible notes issued in 2020, for which the Company elected the fair value option, are accounted for at fair value on a recurring basis with changes in fair value recognized in the statement of operations and comprehensive loss. Interest accrued on the convertible notes was recorded to interest expense during the periods in which the convertible notes were outstanding.	Fair value option The convertible notes issued in 2020, for which the Company elected the fair value option, are accounted for at fair value on a recurring basis with changes in fair value recognized in the statement of operations and comprehensive loss. Interest accrued on the convertible notes is recorded to interest expense.
Fair value measurements	Fair value measurements Fair value is defined as the exchange price to sell an asset or transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Fair value should be based on the assumptions market participants would use when pricing the asset or liability. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. Fair value measurements are classified and disclosed in one of the following three categories: Level 1—Quoted unadjusted prices for identical instruments in active markets. Level 2—Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all observable inputs and significant value drivers are observable in active markets. Level 3—Model derived valuations in which one or more significant inputs or significant value drivers are unobservable, including assumptions developed by the Company. The carrying amounts of the Company’s cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair value due to their short-term nature. Money market funds are highly liquid investments that are actively traded. The pricing information for the Company’s money market funds are 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 non-marketable non-marketable There were no transfers between Levels 1, 2, or 3 for any of the periods presented. As of September 30, 2021, and December 31, 2020, the Company held $84,810 and $52,301, respectively, in money market funds with no unrealized gains or losses.	Fair value measurements Fair value is defined as the exchange price to sell an asset or transfer a liability (exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Fair value should be based on the assumptions market participants would use when pricing the asset or liability. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. Fair value measurements are classified and disclosed in one of the following three categories: Level 1—Quoted unadjusted prices for identical instruments in active markets. Level 2—Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all observable inputs and significant value drivers are observable in active markets. Level 3—Model derived valuations in which one or more significant inputs or significant value drivers are unobservable, including assumptions developed by the Company. The carrying amounts of the Company’s cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair value due to their short-term nature. Money market funds are highly liquid investments that are actively traded. The pricing information for the Company’s money market funds are 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. There were no transfers between Levels 1, 2, or 3 for any of the periods presented. As of December 31, 2019, and 2020, the Company held $2,470 and $52,301, respectively, in money market funds with no unrealized gains or losses. The estimated fair value of the convertible notes, which is classified as Level 3 of the fair value hierarchy, is determined by using a scenario-based analysis that estimates the fair value of the convertible notes based on the probability-weighted present value of expected future investment returns, considering possible outcomes available to the noteholder, including conversions in subsequent equity financings, change of control transactions, settlement and dissolution.
Recently adopted accounting pronouncements	Recently adopted accounting pronouncements In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. On June 20, 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting earlier than under current guidance for nonemployee awards. The Company adopted this standard as of January 1, 2020 on a retrospective basis. The adoption of this standard did not have a material impact on its unaudited condensed financial statements. In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to	Recently adopted accounting pronouncements In November 2016, the FASB issued Accounting Standards Update (“ASU”) 2016-18, Statement of Cash Flows – Restricted Cash (Topic 230) beginning-of-period end-of-period On June 20, 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement
Recently issued accounting pronouncements	Recently issued accounting pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2018-10, 2018-11, 2018-20, 2019-01 2019-10, right-of-use In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In August 2020, the FASB issued ASU No. 2020-06, 470-20) 815-40). 470-20 2020-06	Recently issued accounting pronouncements In February 2016, the FASB issued ASU No. 2016-02 , Leases (Topic 842) 2018-10, 2018-11, 2018-20, 2019-01 2019-10, right-of-use In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In August 2020, the FASB issued ASU No. 2020-06, 470-20) 815-40). 470-20 2020-06 periods, beginning after December 15, 2023, and early adoption is permitted. The Company is currently evaluating the impact this standard will have on its financial statements.
Non-marketable equity securities	The Company reports the restricted equity securities as non-marketable non-current

Other Financial Statement Inf_2

Other Financial Statement Information (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Other Financial Statement Information [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following. September 30, December 31, Prepaid insurance $ 1,837 $ 27 Prepaid contract costs 889 — Deposits 57 86 Receivables on exercise of options — 52 Other 786 392 Total prepaid expenses and other current assets $ 3,569 $ 557	Prepaid expenses and other current assets consist of the following. December 31, 2019 2020 Prepaid expenses $ 332 $ 336 Deposits 34 86 Receivables on exercise of options — 52 Other 4 83 Total prepaid expenses and other current assets $ 370 $ 557
Property, Plant and Equipment		Property and equipment, net consists of the following as of December 31, 2019. Equipment under capital lease $ 929 Laboratory equipment 734 Leasehold improvements 421 Furniture and fixtures 269 Office equipmen t 61 Total property and equipment 2,414 Accumulated depreciation and amortization (1,020 ) Total property and equipment, net $ 1,394
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following. September 30, December 31, Accrued payroll $ 1,051 $ 405 Related party payable 994 — Accrued expenses and other 666 130 Total accrued expenses and other current liabilities $ 2,711 $ 535	Accrued and other current liabilities consist of the following. December 31, 2019 2020 Accrued expenses $ 318 $ 128 Accrued payroll 58 405 Other 47 — Total accrued expenses and other current liabilities $ 423 $ 533

Non-Marketable Equity Securit_2

Non-Marketable Equity Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Summary of Carrying Value of the Non-marketable Equity Securities	The carrying value of the non-marketable Initial cost as of April 26, 2021 $ 1,759 Change in fair value (645 ) Balance as of September 30, 2021 $ 1,114

Convertible Notes (Tables)

Convertible Notes (Tables)	12 Months Ended
	Dec. 31, 2020
Schedule of changes in fair value of convertible notes [Abstract]
Schedule of Changes in Fair Value of Convertible Notes	The following table provides the changes in the fair value of the convertible notes for the year ended December 31, 2020. Issuance of convertible note s $ 5,539 Change in fair value of convertible notes 1,210 Conversion into Series C redeemable convertible preferred stock (6,749 ) Balance as of December 31, 2020 $ —

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Temporary Equity [Abstract]
Summary of Redeemable Convertible Preferred Stock	As of December 31, 2020, the Company’s redeemable convertible preferred stock consisted of the following balances. Issue price share Shares Shares issued Carrying Aggregate Series Seed $ 1.01 1,010,456 1,010,456 $ 1,789 $ 1,020 Series Seed-1 1.92 1,787,640 1,787,640 3,718 3,430 Series A 2.15 6,120,111 6,120,111 12,851 13,136 Series B 4.29 5,097,566 5,097,566 21,737 21,882 Series C 0.59 168,756,599 168,756,599 99,481 99,870 Total 182,772,372 182,772,372 $ 139,576 $ 139,338	As of December 31, 2020, the Company’s redeemable convertible preferred stock consisted of the following balances (in thousands, except share amounts). Issue price Shares authorized Shares outstanding Carrying value Aggregate liquidation preference Series Seed $ 1.01 1,010,456 1,010,456 $ 1,789 $ 1,020 Series Seed-1 1.92 1,787,640 1,787,640 3,718 3,430 Series A 2.15 6,120,111 6,120,111 12,851 13,136 Series B 4.29 5,097,566 5,097,566 21,737 21,882 Series C 0.59 168,756,599 168,756,599 99,481 99,870 Total 182,772,372 182,772,372 $ 139,576 $ 139,338

Stock Compensation (Tables)

Stock Compensation (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Share-based Payment Arrangement, Expensed and Capitalized, Amount	The following tables summarize the stock-based compensation expense for stock options and restricted stock awards granted to employees and nonemployees that was recorded in the Company’s statements of operations and comprehensive loss for the nine months ended September 30, 2021 and 2020. Nine months ended 2021 2020 Research and development $ 606 $ 4 General and administrative 1,444 184 Total stock-based compensation expense $ 2,050 $ 188 Nine months ended 2021 2020 Employees $ 1,878 $ 182 Nonemployees 172 6 Total stock-based compensation expense $ 2,050 $ 188	The following tables summarize the stock-based compensation expense for stock options and restricted stock awards granted to employees and nonemployees that was recorded in the Company’s statements of operations and comprehensive loss for the years ended December 31, 2019 and 2020. Year ended 2019 2020 Research and development $ 40 $ 4 General and administrative 223 327 Total stock-based compensation expense $ 263 $ 331 Year ended 2019 2020 Employees $ 233 $ 321 Nonemployees 30 10 Total stock-based compensation expense $ 263 $ 331
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The fair value of stock options granted during the nine months ended September 30, 2021 and 2020 was estimated using the Black-Scholes option pricing model based on the following weighted average assumptions. Nine months ended 2021 2020 Expected term (in years) 5.5 – 6.1 5.5 – 6.1 Expected volatility 75.4% – 76.6% 74.0% – 75.7% Risk-free rate 0.6% – 1.1% 0.4% – 1.7% Dividend yield — —	The fair value of stock options granted during the years ended December 31, 2019 and 2020, was estimated using the Black-Scholes option pricing model based on the following weighted average assumptions. Year ended December 31, 2019 2020 Expected term (in years) 5.5 – 6.0 5.5 – 6.1 Expected volatility 74.0% – 74.3% 86.1% – 92.5% Risk-free rate 2.19% – 2.22% 0.41% – 1.67% Dividend yield — —
Summary of Share-based Compensation Arrangements by Share-based Payment Award	Stock option activity under the 2017 EIP and 2021 EIP was as follows: Number of Weighted- Weighted- (years) Aggregate Balance—December 31, 2020 1,855,507 $ 2.99 9.79 $ 8 Granted 1,188,064 8.98 Exercised (145,805 ) 3.77 Cancelled and forfeited (3,095 ) 9.38 Balance—September 30, 2021 2,894,671 5.43 9.35 $ 34,521 Options exercisable—September 30, 2021 82,944 3.42 8.96 $ 1,155 Vested and expected to vest—September 30, 2021 2,894,671 $ 5.43 9.35 $ 34,521	The following table summarizes the Company’s option activity for the year ended December 31, 2020. Number of options Weighted- average exercise price per share Weighted- average remaining contractual life (years) Aggregate intrinsic value (000s) Balance—December 31, 2019 158,599 $ 7.88 8.19 $ 10 Granted 1,865,091 2.98 Exercised (33,291 ) 8.45 Cancelled and forfeited (134,892 ) 6.75 Balance—December 31, 2020 1,855,507 $ 2.99 9.79 $ 8 Options exercisable—December 31, 2020 146,830 $ 3.84 8.17 $ 1 Unvested and expected to vest—December 31, 2020 1,818,708 $ 2.96 9.92 $ —
Summary of Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity	The following table summarizes the activity for the Company’s restricted stock for the nine months ended September 30, 2021. Number of Unvested as of December 31, 2020 41,363 Vested (37,226 ) Unvested as of September 30, 2021 4,137	The following table summarizes the activity for the Company’s restricted stock for the year ended December 31, 2020. Number of Unvested as of December 31, 2019 10,340 Granted 49,636 Vested (18,613 ) Unvested as of December 31, 2020 41,363

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Summary Of Provision for Income Taxes	The provision for income taxes for the years ended December 31, 2019 and 2020 consisted of the following. December 31, 2019 2020 Current: Federal $ — $ — State 1 1 Total current provision 1 1 Total deferred provision — — Total provision for income taxes $ 1 $ 1
Schedule Of Reconciliation Of The Provision For Incomes Taxes	A reconciliation of the provision for income taxes computed using the U.S. statutory federal income tax rate compared to the income tax provision included in the statement of operations and comprehensive loss is as follows. Year ended 2019 2020 Tax at U.S. statutory rate on income before income taxes $ (2,409 ) $ (11,217 ) Change in valuation allowanc e 2,999 10,986 Research and development credits (635 ) 122 State taxes 1 1 Other 45 109 Total provision for income taxes $ 1 $ 1
Schedule Of Components Of the Deferred Tax Assets And Liabilities	The significant components of the Company’s deferred tax assets and liabilities are as follows. December 31, 2019 2020 Deferred tax assets: Net operating loss carryforwards $ 7,267 $ 9,681 Research and other tax credits 2,603 2,652 Property and equipment — 25 Intangible asset s 27 8,019 Stock-based compensation 63 119 Reserves and accruals 108 554 Total deferred tax assets 10,068 21,050 Valuation allowance (10,002 ) (21,050 ) Total deferred tax assets, net of valuation allowance $ 66 $ — Deferred tax liabilities: Property and equipment (66 ) — Total deferred tax liabilities (66 ) — Net deferred tax assets $ — $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Summary of Future Minimum Lease Payments For Operating Leases	The aggregate future minimum lease payments for operating leases as of September 30, 2021, are as follows. Operating Sublease 2021 (remaining 3 months) $ 587 $ (462 ) 2022 2,381 (1,901 ) 2023 2,458 (1,964 ) 2024 2,537 (2,029 ) 2025 1,953 (1,569 ) Total payments $ 9,916 $ (7,925 ) (1) Future minimum lease payments include repayment of outstanding restructuring liabilities.	The aggregate future minimum lease payments for operating leases as of December 31, 2020, are as follows. Year ending December 31, Operating leases(1) Sublease income 2021 $ 2,838 $ (1,746 ) 2022 2,295 (1,804 ) 2023 2,351 (1,864 ) 2024 2,221 (1,926 ) 2025 2,075 (1,483 ) Total payments $ 11,780 $ (8,823 ) (1) Future minimum lease payments include repayment of outstanding restructuring liabilities

Restructuring and Related Act_2

Restructuring and Related Activities (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Restructuring and Related Activities [Abstract]
Summary of Activity Related To The Restructuring Liabilities	The activity related to the restructuring liabilities for the nine months ended September 30, 2021, is as follows. Lease-related Employee Total Balance as of December 31, 2020 2,584 12 2,596 Accretion 116 — 116 Provision 28 — 28 Cash payments (863 ) (12 ) (875 ) Lease assignment to NeuBase (136 ) — (136 ) Balance as of September 30, 2021 $ 1,729 $ — $ 1,729	The activity related to the restructuring liabilities for the years ended December 31, 2019 and 2020 are as follows. Lease-related exit costs Employee termination Total Restructuring costs $ 261 $ — $ 261 Accretion 14 — 14 Cash payments (102 ) — (102 ) Balance as of December 31, 2019 173 — 173 Restructuring costs 2,996 321 3,317 Accretion 24 — 24 Cash payments (609 ) (309 ) (918 ) Balance as of December 31, 2020 $ 2,584 $ 12 $ 2,596

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable To Common Stockholders (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
Summary of Dilutive Shares Excluded From Computation of Diluted Net Loss Per Share	The following outstanding potentially dilutive shares were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented, because including them would have been anti-dilutive (on an as-converted Nine months ended 2021 2020 Redeemable convertible preferred stock — 1,209,599 Class A common stock options issued and outstanding 2,894,671 164,588 Unvested restricted stock awards 4,137 — Total 2,898,808 1,374,187	The following outstanding potentially dilutive shares were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented, because including them would have been anti-dilutive (on an as-converted December 31, 2019 2020 Redeemable convertible preferred stock 1,209,599 15,774,014 Class A common stock options issued and outstanding 158,599 1,855,507 Unvested restricted stock awards 10,340 41,363 Total 1,378,538 17,670,884

Organization and Description _2

Organization and Description of the Business - Additional Information (Detail) $ / shares in Units, $ in Thousands	May 20, 2021USD ($)shares	May 13, 2021$ / sharesshares	May 07, 2021	May 31, 2021shares	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Accumulated deficit					$ 107,209	$ 91,447	$ 38,034
Cash and cash equivalents					$ 86,191	$ 53,654	$ 3,195
Stock split ratio			11.5869
Underwriting discounts and commissions	$ 3,852
Offering costs	2,765
Common Class A [Member] | IPO [Member]
Stock shares issued during the period new issues shares | shares		4,350,000
Sale of stock, price per share | $ / shares		$ 11
Sale of stock net consideration received on the transaction	$ 48,411
Common Class A [Member] | Over-Allotment Option [Member]
Stock shares issued during the period new issues shares | shares	652,500
Common Class A [Member] | Conversion Of Redeemable Preferred Stock Into Common Stock [Member]
Conversion of redeemable convertible preferred stock to common stock | shares				15,464,775
Common Class B [Member] | Conversion Of Redeemable Preferred Stock Into Common Stock [Member]
Conversion of redeemable convertible preferred stock to common stock | shares				309,238

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Line Items]
Income tax provision	$ 0	$ 0	$ 1	$ 1
Property, plant and equipment, useful life			5 years
Asset impairments			$ 1,185	10
Money Market Funds [Member]
Accounting Policies [Line Items]
Money market funds	84,810		52,301	2,470
Unrealized gains or losses on securities	$ 0		$ 0	$ 0

Other Financial Statement Inf_3

Other Financial Statement Information - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Other Financial Statement Information [Abstract]
Prepaid Expense		$ 336	$ 332
Prepaid insurance	$ 1,837	27
Prepaid contract costs	889
Deposits	57	86	34
Receivables on exercise of options		52
Other	786	392
Other		83	4
Total Prepaid expenses and other current assets	$ 3,569	$ 557	$ 370

Other Financial Statement Inf_4

Other Financial Statement Information - Schedule of Property and Equipment (Details) $ in Thousands	Dec. 31, 2019USD ($)
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,414
Accumulated depreciation and amortization	(1,020)
Total property and equipment, net	1,394
Equipment Under Capital Lease [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	929
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	734
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	421
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	269
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 61

Other Financial Statement Inf_5

Other Financial Statement Information - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Other Financial Statement Information [Abstract]
Accrued expenses		$ 128	$ 318
Accrued payroll	$ 1,051	405	58
Related party payable	994
Other	666	130	47
Total accrued expenses and other current liabilities	$ 2,711	535
Total accrued expenses and other current liabilities		$ 533	$ 423

Other Financial Statement Inf_6

Other Financial Statement Information - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Depreciation and amortization expense	$ 251	$ 432
Capital Leases, income statement, amortization expense	108	184
Gain (loss) on disposition of Property plant equipment		(94)
Impairment charge	1,185
Laboratory Equipment [Member] | Research and Development Expense [Member]
Gain (loss) on disposition of Property plant equipment		$ 94
Impairment charge	1,039
Office Equipment [Member] | General and Administrative Expense [Member]
Impairment charge	$ 146

Neubase asset sale - Additional

Neubase asset sale - Additional Information (Detail) - USD ($) $ in Thousands	Apr. 26, 2021	Sep. 30, 2021
Proceeds received from the disposal of business		$ 796
Gain (Loss) on Disposition of Assets		2,691
Neubase Therapeutics Inc [Member]
Investment owned number of shares placed in escrow account	162,260
Escrow Deposit Disbursements Related to Property Acquisition		$ 54,070
Neubase Therapeutics Inc [Member] | Investment In PNAI [Member]
Proceeds received from the disposal of business	$ 796
Disposal group including discontinued operations shares received for disposal	308,635
Investments owned market value	$ 1,759

Non-Marketable Equity Securit_3

Non-Marketable Equity Securities - Additional Information (Detail) - USD ($) $ in Thousands	5 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Net unrealized loss	$ (645)	$ (645)
Other Expense [Member]
Net unrealized loss		$ 645

Non-Marketable Equity Securit_4

Non-Marketable Equity Securities - Summary of Carrying Value of the Non-marketable Equity Securities (Detail) - USD ($) $ in Thousands	5 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Initial cost as of April 26, 2021	$ 1,759
Change in fair value	(645)	$ (645)
Balance as of June 30, 2021	$ 1,114	$ 1,114

Convertible Notes - Schedule o

Convertible Notes - Schedule of Changes in Fair Value of Convertible Notes (Detail) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Oct. 31, 2020	Sep. 30, 2020	Dec. 31, 2020
Issuance of convertible notes		$ 5,602	$ 5,602
Change in fair value of convertible notes		$ 775	1,076
Balance as of December 31, 2020			0
Convertible Notes [Member]
Issuance of convertible notes			5,539
Change in fair value of convertible notes			1,210
Series C [Member]
Conversion into Series C redeemable convertible preferred stock			$ (6,749)
Series C [Member] | Convertible Notes [Member]
Conversion into Series C redeemable convertible preferred stock	$ (134)

Convertible Notes - Additional

Convertible Notes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Dec. 31, 2020	May 31, 2020	Mar. 31, 2020
Series C [Member]
Debt Instrument [Line Items]
Debt outstanding converted instrument amount		$ 6,749
Debt instrument converted shares issued		11,404,246
Temporary equity original issuance price		$ 0.59
Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument Principal amount			$ 5,602	$ 5,000
Debt instrument fixed interest rate percentage			4.00%	4.00%
Convertible Notes [Member] | Additional Convertible Notes Issued [Member]
Debt Instrument [Line Items]
Debt instrument Principal amount			$ 602
Convertible Notes [Member] | Series B redeemable convertible stock [Member]
Debt Instrument [Line Items]
Debt conversion convertible instrument percent			85.00%	85.00%
Debt instrument convertible price per share			$ 4.2926	$ 4.2926
Convertible Notes [Member] | Series C [Member]
Debt Instrument [Line Items]
Debt conversion convertible instrument percent	85.00%
Debt instrument convertible price per share	$ 0.5030
Debt outstanding converted instrument amount	$ 134
Debt instrument converted shares issued	11,404,246
Temporary equity original issuance price	$ 0.5918

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Shares Authorized	0	182,772,372	15,907,207
Shares Issued	0	182,772,372	14,015,773
Shares Outstanding	0	182,772,372	14,015,773
Carrying Value		$ 139,576	$ 40,095
Aggregate Liquidation Preference		$ 139,338
Series Seed [Member]
Temporary Equity [Line Items]
Issue Price Per Share		$ 1.01
Shares Authorized		1,010,456
Shares Issued		1,010,456
Shares Outstanding		1,010,456
Carrying Value		$ 1,789
Aggregate Liquidation Preference		$ 1,020
Series Seed-1 [Member]
Temporary Equity [Line Items]
Issue Price Per Share		$ 1.92
Shares Authorized		1,787,640
Shares Issued		1,787,640
Shares Outstanding		1,787,640
Carrying Value		$ 3,718
Aggregate Liquidation Preference		$ 3,430
Series A [Member]
Temporary Equity [Line Items]
Issue Price Per Share		$ 2.15
Shares Authorized		6,120,111
Shares Issued		6,120,111
Shares Outstanding		6,120,111
Carrying Value		$ 12,851
Aggregate Liquidation Preference		$ 13,136
Series B [Member]
Temporary Equity [Line Items]
Issue Price Per Share		$ 4.29
Shares Authorized		5,097,566
Shares Issued		5,097,566
Shares Outstanding		5,097,566
Carrying Value		$ 21,737
Aggregate Liquidation Preference		$ 21,882
Series C [Member]
Temporary Equity [Line Items]
Issue Price Per Share		$ 0.59
Shares Authorized		168,756,599
Shares Issued		168,756,599
Shares Outstanding		168,756,599
Carrying Value		$ 99,481
Aggregate Liquidation Preference		$ 99,870

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	May 31, 2021	Oct. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Proceeds from redeemable convertible preferred stock			$ 80,000,000
Temporary equity accretion to redemption value			$ 0	$ 0
Common Stock [Member] | Covertible Preferred Stock [Member]
Temporary Equity [Line Items]
Stock issued during period for conversion of convertible securities	15,774,014
Series C [Member]
Temporary Equity [Line Items]
Number of redeemable convertible preferred stock shares issued		135,180,800
Temporary equity purchase price per share		$ 0.5918
Proceeds from redeemable convertible preferred stock		$ 80,000
Debt conversion converted instrument shares issued			11,404,246
Stock issued during period for conversion of convertible securities			135,180,800
Series C [Member] | Ares [Member]
Temporary Equity [Line Items]
Number of redeemable convertible preferred stock shares issued		22,171,553
Series C [Member] | Convertible Notes [Member]
Temporary Equity [Line Items]
Temporary equity purchase price per share		$ 0.5918
Debt conversion converted instrument shares issued		11,404,246
Debt instrument convertible price per share		$ 0.5030
Debt conversion convertible instrument percent		85.00%

Common Stock - Additional Infor

Common Stock - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Common Class A [Member]
Class of Stock [Line Items]
Common stock shares authorized	500,000,000	273,986,920	23,000,000
Common stock par or stated value per share	$ 0.001	$ 0.001	$ 0.001
Common stock conversion basis	one	one
Cash dividends	$ 0	$ 0
Common Class B [Member]
Class of Stock [Line Items]
Common stock shares authorized	14,600,000	21,593,607
Common stock par or stated value per share	$ 0.001	$ 0.001
Cash dividends	$ 0	$ 0

Stock compensation - Summary of

Stock compensation - Summary of Share-based Payment Arrangement, Expensed and Capitalized, Amount (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Payment Arrangement, Expense	$ 2,050	$ 188	$ 331	$ 263
Employees [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Payment Arrangement, Expense	1,878	182	321	233
Nonemployees [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Payment Arrangement, Expense	172	6	10	30
Research and development [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Payment Arrangement, Expense	606	4	4	40
General and administrative [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based Payment Arrangement, Expense	$ 1,444	$ 184	$ 327	$ 223

Stock Compensation - Schedule o

Stock Compensation - Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions (Detail)	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected volatility, Minimum	75.40%	74.00%	86.10%	74.00%
Expected volatility, Maximum	76.60%	75.70%	92.50%	74.30%
Risk-free rate, Minimum	0.60%	0.40%	0.41%	2.19%
Risk-free rate, Maximum	1.10%	1.70%	1.67%	2.22%
Dividend yield			0.00%	0.00%
Minimum [Member]
Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected term (in years)	5 years 6 months	5 years 6 months	5 years 6 months	5 years 6 months
Maximum [Member]
Schedule Of Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days	6 years

Stock Compensation - Summary _2

Stock Compensation - Summary of Share-based Compensation Arrangements by Share-based Payment Award (Detail) - 2017 EIP And 2021 EIP [Member] - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, Beginning	1,855,507	158,599
Number of options, Granted	1,188,064	1,865,091
Number of options, Exercised	(145,805)	(33,291)
Number of options, Cancelled and forfeited	(3,095)	(134,892)
Number of options, Ending	2,894,671	1,855,507	158,599
Number of options, Options exercisable	82,944	146,830
Number of options, Unvested and expected to vest	2,894,671	1,818,708
Weighted average exercise price, Opening balance	$ 2.99	$ 7.88
Weighted average exercise price, Granted	8.98	2.98
Weighted average exercise price, Exercised	3.77	8.45
Weighted average exercise price, Cancelled and forfeited	9.38	6.75
Weighted average exercise price, Ending balance	5.43	2.99	$ 7.88
Weighted average exercise price, Option exercisable	3.42	3.84
Weighted average exercise price, Unvested and expected to vest	$ 5.43	$ 2.96
Weighted average remaining contractual term	9 years 4 months 6 days	9 years 9 months 14 days	8 years 2 months 8 days
Weighted average remaining contractual term, Options exercisable	8 years 11 months 15 days	8 months 5 days
Weighted average remaining contractual term, Unvested and expected to vest	9 years 4 months 6 days	9 months 28 days
Intrinsic Value	$ 34,521	$ 8	$ 10
Intrinsic Value, Options exercisable	1,155	1
Intrinsic Value, Unvested and expected to vest	$ 34,521	$ 0

Stock Compensation - Summary _3

Stock Compensation - Summary of Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity (Detail) - Restricted Stock [Member] - shares	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested Opening Balance	41,363	10,340
Granted		49,636
Vested	(37,226)	(18,613)
Unvested Ending balance	4,137	41,363

Stock Compensation - Additional

Stock Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended		12 Months Ended
	Oct. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Apr. 30, 2021
Share Based Payment Arrangement [Line Items]
Share based compensation arrangement by share based payment award, Options exercised in period, Total intrinsic value		$ 206		$ 1	$ 6
Stock-based compensation expense		$ 2,050	$ 188	331	$ 263
Employee Stock Purchase Plan ESPP [Member]
Share Based Payment Arrangement [Line Items]
Common stock capital, Shares reserved for future issuance							220,251
2021 Equity Incentive Plan [Member]
Share Based Payment Arrangement [Line Items]
Common stock capital, Shares reserved for future issuance							2,213,773
Share-based compensation arrangement by share-based payment award, Number of shares available for issuance		1,510,665
2017 and 2021 Amended Equity Incentive Plan [Member]
Share Based Payment Arrangement [Line Items]
Share based compensation arrangement by share based payment award, Options granted in period, Weighted average grant date fair value		$ 6.66
2017 and 2021 Amended Equity Incentive Plan [Member] | Unvested Stock Options And Restricted Stock Awards [Member]
Share Based Payment Arrangement [Line Items]
Share based compensation, Nonvested awards, Compensation cost not yet recognized Stock options and equity instruments other than options		$ 10,348		$ 4,219
Share based compensation, Nonvested awards, Compensation cost not yet recognized period of recognition stock options and equity instruments other than options		3 years 1 month 24 days		2 years
2017 Equity Incentive Plan [Member]
Share Based Payment Arrangement [Line Items]
Share based compensation arrangement by share based payment award, Number of shares authorized				3,052,169
Share based compensation arrangement by share based payment award, Vesting period						4 years
Share based compensation arrangement by share based payment award, Vesting percentage						25.00%
Share-based compensation arrangement by share-based payment award, Number of shares available for issuance				1,150,088
Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award						286,578
2017 Equity Incentive Plan [Member] | Maximum [Member]
Share Based Payment Arrangement [Line Items]
Share based compensation arrangement by share based payment award, Expiration period						10 years
2017 Equity Incentive Plan [Member] | Minimum [Member]
Share Based Payment Arrangement [Line Items]
Share based compensation arrangement by share based payment award, Expiration period						3 years
Restricted Stock [Member] | 2017 and 2021 Amended Equity Incentive Plan [Member]
Share Based Payment Arrangement [Line Items]
Share based compensation arrangement by share based payment award, Vesting period	1 year
Share based compensation arrangement by share based payment award, Equity instruments other than options nonvested, Weighted average Grant date fair value	$ 6.37
Stock-based compensation expense		$ 236
Employee Stock [Member]
Share Based Payment Arrangement [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent		85.00%
Share Based Compensation Arrangement By Share Based Payment Award Minimum Employee Subscription Rate		1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate		15.00%
Common Stock Capital Shares Minimum Increase In Shares Reserved For Future Issuance		440,502
Percentage Of Shares Of Company Common Stock Outstanding For Increase In Shares Reserved For Issuance Under Stock Plan		1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period		0
Common Class A [Member] | Restricted Stock [Member]
Share Based Payment Arrangement [Line Items]
Share based compensation arrangement by share based payment award, Restricted shares of fully issued and outstanding common stock	49,636

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Employer contributions	$ 0	$ 0	$ 0

License and Collaborations - Ad

License and Collaborations - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Oct. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
License and Collaborations [Line Items]
Stock shares issued during the period value			$ 48,411
CMU License Agreement [Member]
License and Collaborations [Line Items]
Contractual Obligation				$ 9,000
Ares Agreement [Member] | Ares Trading S A [Member]
License and Collaborations [Line Items]
Milestone payments paid				25,000
Due to related parties			$ 1,256
Payment for royalties on a licensed product, Term			2 years
Ares Agreement [Member] | Ares Trading S A [Member] | Research and Development Expense [Member]
License and Collaborations [Line Items]
Non-refundable license issue fee				13,121
Milestone payments recorded to research and development expense				25,000
Ares Agreement [Member] | Ares Trading S A [Member] | Achievement Of Specified BLA Filing Or Regulatory Approval Milestones [Member]
License and Collaborations [Line Items]
Milestone payments payable				176,500
Ares Agreement [Member] | Ares Trading S A [Member] | Achievement Of Specified Commercial Milestones [Member]
License and Collaborations [Line Items]
Milestone payments payable				$ 515,000
Series C [Member]
License and Collaborations [Line Items]
Temporary equity issue price per share	$ 0.5918
Series C [Member] | Ares Agreement [Member] | Ares Trading S A [Member]
License and Collaborations [Line Items]
Temporary equity stock shares issued during the period shares	22,171,553
Temporary equity issue price per share	$ 0.5918
Temporary equity shares issued during the period value	$ 13,121
Yale University [Member]
License and Collaborations [Line Items]
Stock shares issued during the period shares		264,301			264,301
Reimbursement for patent related expenses		$ 45			$ 45
Yale University [Member] | Portion at Fair Value Measurement [Member]
License and Collaborations [Line Items]
Stock shares issued during the period value					100
PNAI [Member] | Yale License Agreement [Member]
License and Collaborations [Line Items]
Initial fee paid as consideration		$ 37			$ 37
PNAI [Member] | Yale License Agreement [Member] | Common Stock [Member]
License and Collaborations [Line Items]
Percentage of common stock issuable on a fully diluted and converted basis		5.00%			5.00%

Income taxes - Summary Of Provi

Income taxes - Summary Of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal			$ 0	$ 0
State			1	1
Total current provision			1	1
Total deferred provision			0	0
Total provision for income taxes	$ 0	$ 0	$ 1	$ 1

Income taxes - Schedule Of Reco

Income taxes - Schedule Of Reconciliation Of The Provision For Incomes Taxes (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at U.S. statutory rate on income before income taxes			$ (11,217)	$ (2,409)
Change in valuation allowance			10,986	2,999
Research and development credits			122	(635)
State taxes			1	1
Other			109	45
Total provision for income taxes	$ 0	$ 0	$ 1	$ 1

Income taxes - Schedule Of Comp

Income taxes - Schedule Of Components Of the Deferred Tax Assets And Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 9,681	$ 7,267
Research and other tax credits	2,652	2,603
Property and equipment	25	0
Intangible assets	8,019	27
Stock-based compensation	119	63
Reserves and accruals	554	108
Total deferred tax assets	21,050	10,068
Valuation allowance	(21,050)	(10,002)
Total deferred tax assets, net of valuation allowance	0	66
Deferred tax liabilities:
Property and equipment	0	(66)
Total deferred tax liabilities	0	(66)
Net deferred tax assets	$ 0	$ 0

Income taxes - Additional Infor

Income taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Valuation allowance	$ 21,050	$ 10,002
Threshold percentage of tax benefit is reasonably possible to be recognised likelihood of being sustained	50.00%
Unrecognized tax benefits	$ 0	0
Unrecognized tax benefits income tax penalties and interest expense	0	$ 0
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	44,007
Domestic Tax Authority [Member] | Tax Period Two Thousand And Thirty Two [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	10,246
Domestic Tax Authority [Member] | Tax Period Indefinite [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	33,761
Domestic Tax Authority [Member] | Tax Period Two Thousand And Thirty Seven [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards amount	2,159
State and Local Jurisdiction [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	3,531
State and Local Jurisdiction [Member] | Tax Period Two Thousand And Thirty Six [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	3,531
State and Local Jurisdiction [Member] | Tax Period Two Thousand And Thirty Three [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards amount	$ 1,156

Commitments and Contingencies -

Commitments and Contingencies - Summary of Future Minimum Lease Payments for Operating Leases (Detail) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Operating Leases, 2021 (remaining 6 months)	[1]	$ 587	$ 2,838
Operating Leases 2022	[1]	2,381	2,295
Operating Leases 2023	[1]	2,458	2,351
Operating Leases 2024	[1]	2,537	2,221
Operating Leases 2025	[1]	1,953	2,075
Operating Leases, Total payments	[1]	9,916	11,780
Sublease Income, 2021 (remaining 6 months)		(462)	(1,746)
Sublease Income, 2022		(1,901)	(1,804)
Sublease Income, 2023		(1,964)	(1,864)
Sublease Income, 2024		(2,029)	(1,926)
Sublease Income, 2025		(1,569)	(1,483)
Sublease Income, Total payments		$ (7,925)	$ (8,823)
[1]	Future minimum lease payments include repayment of outstanding restructuring liabilities.

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Detail)		9 Months Ended		12 Months Ended
		Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Nov. 30, 2020USD ($)	Aug. 30, 2018ft²	Apr. 30, 2018USD ($)	Apr. 30, 2015ft²
Other Commitments [Line Items]
Operating lease future minimum payments due	[1]	$ 9,916,000		$ 11,780,000
Operating lease minimum future commitments		7,925,000		8,823,000
Office and Laboratory Space at Woborn Massauchets [Member]
Other Commitments [Line Items]
Area of real estate availed on lease | ft²									3,800
PNAI [Member]
Other Commitments [Line Items]
Operating lease minimum future commitments				581,000		$ 9,916,000
Operating lease, rent expense		0	$ 1,605,000	2,089,000	$ 1,726,000
PNAI [Member] | Previously Reported [Member]
Other Commitments [Line Items]
Operating lease minimum future commitments						11,128,000
PNAI [Member] | Research And Laboratory Equipment [Member]
Other Commitments [Line Items]
Operating lease, rent expense		0	$ 256,000	298,000	$ 416,000
PNAI [Member] | Office and Laboratory Space at Woborn Massauchets [Member]
Other Commitments [Line Items]
Area of real estate availed on lease | ft²							24,606		3,800
Operating lease term							84 months	84 months	39 months
Operating lease renewal term							3 years
Letters of credit outstanding								$ 293,000
Operating lease future minimum payments due		$ 9,916,000		$ 11,128,000
Operating lease minimum future commitments						7,925
PNAI [Member] | Office and Laboratory Space at Woborn Massauchets [Member] | Previously Reported [Member]
Other Commitments [Line Items]
Operating lease minimum future commitments						$ 8,823,000
PNAI [Member] | Office and Laboratory Space at Woborn Massauchets [Member] | Lease Agreements [Member]
Other Commitments [Line Items]
Letters of credit outstanding								$ 50,000
[1]	Future minimum lease payments include repayment of outstanding restructuring liabilities.

Restructuring and Related Act_3

Restructuring and Related Activities - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Nov. 30, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring liability	$ 1,729	$ 2,596
Employee Severance And Other Employee Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring liability			$ 321
Leased Facilities Abandoned [Member] | Discounted Lease Related Restructuring Liability [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring liability			2,228
Equipment Abondoned [Member] | Discounted Lease Related Restructuring Liability [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring liability			$ 768

Restructuring and Related Act_4

Restructuring and Related Activities - Summary of Activity Related to the Restructuring Liabilities (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Beginning balance	$ 2,596
Accretion	116	$ 1,416	$ 2,996	$ 261
Provision (Restructuring costs)	28		2,423	173
Cash payments	(875)	(88)
Lease assignment to NeuBase	(136)
Ending balance	1,729		2,596
Lease-related exit costs
Restructuring Cost and Reserve [Line Items]
Beginning balance	2,584	173	173
Accretion	116		24	14
Provision (Restructuring costs)	28		2,996	261
Cash payments	(863)		(609)	(102)
Lease assignment to NeuBase	(136)
Ending balance	1,729		2,584	173
Employee termination
Restructuring Cost and Reserve [Line Items]
Beginning balance	12	0	0
Accretion			0	0
Provision (Restructuring costs)			321	0
Cash payments	(12)		(309)	0
Ending balance			12	0
Restructuring Costs Total [Member]
Restructuring Cost and Reserve [Line Items]
Beginning balance	$ 2,596	$ 173	173
Accretion			24	14
Provision (Restructuring costs)			3,317	261
Cash payments			(918)	(102)
Ending balance			$ 2,596	$ 173

Net Loss Per Common Share - Sum

Net Loss Per Common Share - Summary of Dilutive Shares Excluded from Computation of Diluted Net Loss Per Share (Detail) - shares	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities	2,898,808	1,374,187	17,670,884	1,378,538
Redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities		1,209,599	15,774,014	1,209,599
Class A common stock options issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities	2,894,671	164,588	1,855,507	158,599
Unvested restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities	4,137		41,363	10,340

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - Lessee Company Where Ceo of the Lessor Company is the Member of Board of Directors [Member] $ in Thousands	Dec. 07, 2018ft²	Sep. 30, 2021	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Apr. 01, 2019ft²
Related Party Transaction [Line Items]
Area of space subleased	400
Revised area of space subleased						3,700
Sublease lease term extension		2 years		2 years
Percentage of profit arising on sublease due to excess amount collected from subtenant to be shared						50.00%
Operating lease rental expense sublease rentals | $			$ 160	$ 160	$ 279

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Thousands	May 07, 2021	Nov. 30, 2021USD ($)ft²	Dec. 31, 2021USD ($)
Subsequent Event [Line Items]
Stock split ratio	11.5869
California | Office Space | Scenario Forecast
Subsequent Event [Line Items]
Area of real estate availed on lease | ft²		5,000
Operating lease term		3 years
Operating lease, rent expense		$ 288
Percentage of increase in rent annually		3.00%
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock split ratio	11.5869
Subsequent Event [Member] | Amplyx Agreement [Member]
Subsequent Event [Line Items]
Upfront Initial Payment			$ 5,000
Aggregate milestone payments obligated to pay based on certain regulatory milestones as per agreement			7,000
Subsequent Event [Member] | Amplyx Agreement [Member] | Novarties [Member]
Subsequent Event [Line Items]
Aggregate milestone payments obligated to pay based on development,regulatory and sales milestones as per agreement			69,000
Subsequent Event [Member] | Loan Agreement [Member] | Term Loan [Member]
Subsequent Event [Line Items]
Debt instrument face amount			50,000
Proceeds from Issuance of Debt			5,000
Debt instrument balance amount available to be drawn at option under the agreement			$ 5,000
Debt instrument maturity date			December 2026
Debt instrument maturity date may be extended period based on certain clinical data milestones			12 months
Debt instrument monthly interest only payments required to pay for period			48 months
Debt instrument monthly interest only payments extension period if final maturity date is extended			60 months
Interest rate			8.254%
Percentage of final payment required to pay upon maturity date or prepayment of loan			5.00%
Percentage of final payment required to pay if maturity date is extended			7.00%

Events (unaudited) subsequent_2

Events (unaudited) subsequent to the date of the report of the independent registered public accounting firm - Additional Information (Detail) - USD ($) $ in Thousands	Apr. 26, 2021	Sep. 30, 2021
Subsequent Event [Line Items]
Proceeds received from the disposal of business		$ 796
Neubase Therapeutics Inc [Member]
Subsequent Event [Line Items]
Investment owned number of shares placed in escrow account	162,260
Neubase Therapeutics Inc [Member] | Investment In PNAI [Member]
Subsequent Event [Line Items]
Proceeds received from the disposal of business	$ 796
Disposal group including discontinued operations shares received for disposal	308,635
Investments owned market value	$ 1,759