Annexon (ANNX) 10-Q 16 Nov 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 31, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Trading Symbol	ANNX
Entity Registrant Name	Annexon, Inc.
Entity Central Index Key	0001528115
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-39402
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-5414423
Entity Address, Address Line One	180 Kimball Way
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	822-5500
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		38,157,618

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 370,686	$ 43,931
Prepaid expenses and other current assets	2,889	1,475
Total current assets	373,575	45,406
Property and equipment, less accumulated depreciation of $1,695 and $1,304 as of September 30, 2020, and December 31, 2019, respectively	2,039	2,138
Other long-term assets		2,354
Total assets	375,614	49,898
Current liabilities:
Accounts payable	3,954	2,371
Accrued liabilities	4,649	2,194
Deferred rent, current	385	366
Total current liabilities	8,988	4,931
Deferred rent	1,147	1,437
Total liabilities	10,135	6,368
Commitments and contingencies (Note 6)
Stockholders’ Equity (Deficit):
Preferred stock, $0.001 par value; 5,000,000 and 0 shares authorized as of September 30, 2020, and December 31, 2019, respectively; 0 issued and outstanding as of September 30, 2020, and December 31, 2019, respectively
Common stock, $0.001 par value; 300,000,000 and 150,000,000 shares authorized as of September 30, 2020, and December 31, 2019, respectively; 38,157,618 and 433,749 shares issued and outstanding as of September 30, 2020, and December 31, 2019, respectively	38	4
Additional paid-in capital	508,318	2,202
Accumulated other comprehensive loss	(78)	(80)
Accumulated deficit	(142,799)	(102,580)
Total stockholders’ equity (deficit)	365,479	(100,454)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	$ 375,614	49,898
Redeemable Convertible Preferred Stock [Member]
Current liabilities:
Redeemable convertible preferred stock, $0.001 par value; 0 and 119,155,472 shares authorized as of September 30, 2020 and December 31, 2019, respectively; 0 and 111,748,065 shares issued and outstanding as of September 30, 2020 and December 31, 2019, respectively; liquidation preference of $0 and $137,814 as of September 30, 2020 and December 31, 2019, respectively		$ 143,984

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accumulated depreciation on property plant and equipment	$ 1,695	$ 1,304
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	300,000,000	150,000,000
Common stock, shares issued	38,157,618	433,749
Common stock, shares outstanding	38,157,618	433,749
Redeemable Convertible Preferred Stock [Member]
Temporary equity, par value per share	$ 0.001	$ 0.001
Temporary equity, shares authorized	0	119,155,472
Temporary equity, shares issued	0	111,748,065
Temporary equity, shares outstanding	0	111,748,065
Temporary equity, liquidation preference	$ 0	$ 137,814

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating expenses:
Research and development	$ 11,775	$ 7,089	$ 31,279	$ 17,729
General and administrative	3,810	1,981	8,999	5,660
Total operating expenses	15,585	9,070	40,278	23,389
Loss from operations	(15,585)	(9,070)	(40,278)	(23,389)
Loss on remeasurement of redeemable convertible preferred stock liability		(1,340)		(5,670)
Other (expense) income, net	(52)	224	64	821
Net loss before taxes	(15,637)	(10,186)	(40,214)	(28,238)
Provision for income taxes	1	2	5	3
Net loss	(15,638)	(10,188)	(40,219)	(28,241)
Accretion on redeemable convertible preferred stock	(145)	(281)	(705)	(815)
Deemed dividend – beneficial conversion feature on redeemable convertible preferred stock	(6,219)		(6,219)
Net loss attributable to common stockholders	$ (22,002)	$ (10,469)	$ (47,143)	$ (29,056)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.77)	$ (24.14)	$ (4.79)	$ (67.04)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted	28,465,156	433,749	9,845,754	433,406

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (15,638)	$ (10,188)	$ (40,219)	$ (28,241)
Other comprehensive gain (loss):
Foreign currency translation adjustment	4	(7)	2	(17)
Comprehensive loss	$ (15,634)	$ (10,195)	$ (40,217)	$ (28,258)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning Balance, Shares at Dec. 31, 2018		89,525,848
Beginning Balance, Values at Dec. 31, 2018		$ 102,082
Beginning Balance, Shares at Dec. 31, 2018			432,309
Beginning Balance, Values at Dec. 31, 2018	$ (64,202)		$ 4	$ 1,257	$ (66)	$ (65,397)
Accretion on redeemable convertible preferred stock		$ 262
Accretion on redeemable convertible preferred stock	(262)			(262)
Stock option exercises, Shares			1,440
Stock option exercises, Values	3			3
Stock-based compensation	466			466
Foreign currency translation adjustment	(6)				(6)
Net loss	(8,652)					(8,652)
Ending Balance, Shares at Mar. 31, 2019		89,525,848
Ending Balance, Values at Mar. 31, 2019		$ 102,344
Ending Balance, Shares at Mar. 31, 2019			433,749
Ending Balance, Values at Mar. 31, 2019	(72,653)		$ 4	1,464	(72)	(74,049)
Beginning Balance, Shares at Dec. 31, 2018		89,525,848
Beginning Balance, Values at Dec. 31, 2018		$ 102,082
Beginning Balance, Shares at Dec. 31, 2018			432,309
Beginning Balance, Values at Dec. 31, 2018	(64,202)		$ 4	1,257	(66)	(65,397)
Foreign currency translation adjustment	(17)
Net loss	(28,241)
Ending Balance, Shares at Sep. 30, 2019		111,748,065
Ending Balance, Values at Sep. 30, 2019		$ 143,704
Ending Balance, Shares at Sep. 30, 2019			433,749
Ending Balance, Values at Sep. 30, 2019	(91,759)		$ 4	1,958	(83)	(93,638)
Beginning Balance, Shares at Mar. 31, 2019		89,525,848
Beginning Balance, Values at Mar. 31, 2019		$ 102,344
Beginning Balance, Shares at Mar. 31, 2019			433,749
Beginning Balance, Values at Mar. 31, 2019	(72,653)		$ 4	1,464	(72)	(74,049)
Accretion on redeemable convertible preferred stock		$ 272
Accretion on redeemable convertible preferred stock	(272)			(272)
Stock-based compensation	437			437
Foreign currency translation adjustment	(4)				(4)
Net loss	(9,401)					(9,401)
Ending Balance, Shares at Jun. 30, 2019		89,525,848
Ending Balance, Values at Jun. 30, 2019		$ 102,616
Ending Balance, Shares at Jun. 30, 2019			433,749
Ending Balance, Values at Jun. 30, 2019	(81,893)		$ 4	1,629	(76)	(83,450)
Issuance of redeemable convertible preferred stock, net of issuance costs, Shares		22,222,217
Issuance of redeemable convertible preferred stock, net of issuance costs, Values		$ 40,807
Accretion on redeemable convertible preferred stock		$ 281
Accretion on redeemable convertible preferred stock	(281)			(281)
Stock-based compensation	610			610
Foreign currency translation adjustment	(7)				(7)
Net loss	(10,188)					(10,188)
Ending Balance, Shares at Sep. 30, 2019		111,748,065
Ending Balance, Values at Sep. 30, 2019		$ 143,704
Ending Balance, Shares at Sep. 30, 2019			433,749
Ending Balance, Values at Sep. 30, 2019	(91,759)		$ 4	1,958	(83)	(93,638)
Beginning Balance, Shares at Dec. 31, 2019		111,748,065
Beginning Balance, Values at Dec. 31, 2019		$ 143,984
Beginning Balance, Shares at Dec. 31, 2019			433,749
Beginning Balance, Values at Dec. 31, 2019	(100,454)		$ 4	2,202	(80)	(102,580)
Accretion on redeemable convertible preferred stock		$ 279
Accretion on redeemable convertible preferred stock	(279)			(279)
Stock-based compensation	663			663
Foreign currency translation adjustment	(11)				(11)
Net loss	(12,341)					(12,341)
Ending Balance, Shares at Mar. 31, 2020		111,748,065
Ending Balance, Values at Mar. 31, 2020		$ 144,263
Ending Balance, Shares at Mar. 31, 2020			433,749
Ending Balance, Values at Mar. 31, 2020	(112,422)		$ 4	2,586	(91)	(114,921)
Beginning Balance, Shares at Dec. 31, 2019		111,748,065
Beginning Balance, Values at Dec. 31, 2019		$ 143,984
Beginning Balance, Shares at Dec. 31, 2019			433,749
Beginning Balance, Values at Dec. 31, 2019	(100,454)		$ 4	2,202	(80)	(102,580)
Beneficial conversion feature on Series D redeemable convertible preferred stock	$ 6,297
Stock option exercises, Shares	9,528
Foreign currency translation adjustment	$ 2
Net loss	(40,219)
Ending Balance, Shares at Sep. 30, 2020		0
Ending Balance, Shares at Sep. 30, 2020			38,157,618
Ending Balance, Values at Sep. 30, 2020	365,479		$ 38	508,318	(78)	(142,799)
Beginning Balance, Shares at Mar. 31, 2020		111,748,065
Beginning Balance, Values at Mar. 31, 2020		$ 144,263
Beginning Balance, Shares at Mar. 31, 2020			433,749
Beginning Balance, Values at Mar. 31, 2020	(112,422)		$ 4	2,586	(91)	(114,921)
Issuance of redeemable convertible preferred stock, net of issuance costs, Shares		71,719,859
Issuance of redeemable convertible preferred stock, net of issuance costs, Values		$ 96,807
Beneficial conversion feature on Series D redeemable convertible preferred stock		(6,297)
Beneficial conversion feature on Series D redeemable convertible preferred stock	6,297			6,297
Accretion on redeemable convertible preferred stock		$ 281
Accretion on redeemable convertible preferred stock	(281)			(281)
Stock-based compensation	763			763
Foreign currency translation adjustment	9				9
Net loss	(12,240)					(12,240)
Ending Balance, Shares at Jun. 30, 2020		183,467,924
Ending Balance, Values at Jun. 30, 2020		$ 235,054
Ending Balance, Shares at Jun. 30, 2020			433,749
Ending Balance, Values at Jun. 30, 2020	(117,874)		$ 4	9,365	(82)	(127,161)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering, Shares		(183,467,924)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering		$ (241,418)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	241,418		$ 21	241,397
Conversion of redeemable convertible preferred stock to common stock upon initial public offering, Shares			20,824,938
Deemed dividend of beneficial conversion feature on conversion of redeemable convertible preferred stock	(6,219)			(6,219)
Deemed dividend of beneficial conversion feature on conversion of redeemable convertible preferred stock		6,219
Accretion on redeemable convertible preferred stock		$ 145
Accretion on redeemable convertible preferred stock	(145)			(145)
Issuance of common stock in connection with initial public offering, net of issuance costs of $24.7 million, Shares			16,889,403
Issuance of common stock in connection with initial public offering, net of issuance costs of $24.7 million, Values	262,440		$ 13	262,427
Stock option exercises, Shares			9,528
Stock option exercises, Values	22			22
Stock-based compensation	1,471			1,471
Foreign currency translation adjustment	4				4
Net loss	(15,638)					(15,638)
Ending Balance, Shares at Sep. 30, 2020		0
Ending Balance, Shares at Sep. 30, 2020			38,157,618
Ending Balance, Values at Sep. 30, 2020	$ 365,479		$ 38	$ 508,318	$ (78)	$ (142,799)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended
	Jun. 30, 2020	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Payments of stock issuance costs					$ 2,974	$ 759
Common Stock [Member]
Payments of stock issuance costs		$ 24,700
Series D Redeemable Convertible Preferred Stock [Member]
Payments of stock issuance costs	$ 5,200		$ 5,193
Series C Redeemable Convertible Preferred Stock [Member]
Payments of stock issuance costs				$ 3
Redeemable convertible preferred stock liability				$ 10,810		$ 10,810

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net loss	$ (40,219)	$ (28,241)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	391	364
Stock-based compensation	2,897	1,513
Change in fair value of redeemable convertible preferred stock liability		5,670
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,414)	491
Other long-term assets	96
Accounts payable	1,733	885
Accrued liabilities	2,956	3
Deferred rent	(271)	(254)
Net cash used in operating activities	(33,831)	(19,569)
Investing activities:
Purchases of property and equipment	(292)	(168)
Net cash used in investing activities	(292)	(168)
Financing activities:
Proceeds from the exercise common stock options	22	3
Proceeds from Paycheck Protection Program loan	500
Repayments of Paycheck Protection Program loan	(500)
Proceeds from issuance of redeemable convertible preferred stock	102,000	29,997
Payments of issuance costs related to redeemable convertible preferred stock	(5,193)
Proceeds from issuance of common stock upon initial public offering, net of underwriting discounts and commissions	267,021
Payments of offering costs related to initial public offering	(2,974)	(759)
Net cash provided by financing activities	360,876	29,241
Net increase in cash and cash equivalents	326,753	9,504
Effect of exchange rate changes on cash and cash equivalents	2	(17)
Cash and cash equivalents at beginning of period	43,931	44,175
Cash and cash equivalents at end of period	370,686	53,662
Non-cash investing and financing activities:
Reclassification of redeemable convertible preferred stock to common stock upon initial public offering	241,418
Reclassification of redeemable convertible preferred stock liability to redeemable convertible preferred stock		10,810
Accretion on redeemable convertible preferred stock	705	815
Deferred offering costs included in accounts payable and accrued liabilities		837
Purchase of property and equipment included in accounts payable		$ 55
Beneficial conversion feature recognized upon issuance of redeemable convertible preferred stock	6,297
Deemed dividend arising from conversion of beneficial conversion feature	$ 6,219

Organization

Organization	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Organization	1. Organization Annexon, Inc., or the Company, is a clinical-stage biopharmaceutical company targeting C1q and initiating molecules of the classical complement pathway to develop transformative therapies for autoimmune and neurodegenerative disorders of the brain, body and eye. The Company is located in South San Francisco, California and was incorporated in Delaware in March 2011. The Company’s wholly-owned subsidiary, Annexon Biosciences Australia Pty Ltd, or the Subsidiary, is a proprietary limited company incorporated in 2016 and domiciled in Australia. The Subsidiary is also engaged in research and development activities in support of its parent company. Initial Public Offering On July 23 14,750,000 2,139,403 262.4 Reverse Stock Split On July 17, 2020, the Company’s board of directors approved an amendment to the Company’s certificate of incorporation to effect a reverse split of shares of the Company’s common stock on a one-for-8.81 basis, or the Reverse Stock Split. The number of authorized shares and the par values of the common stock and redeemable convertible preferred stock were not adjusted as a result of the Reverse Stock Split. In connection with the Reverse Stock Split, the conversion ratio for the Company’s outstanding redeemable convertible preferred stock was proportionately adjusted such that the common stock issuable upon conversion of such preferred stock was decreased in proportion to the Reverse Stock Split. All references to common stock and options to purchase common stock share data, per share data and related information contained in the consolidated financial statements have been retroactively adjusted to reflect the effect of the Reverse Stock Split for all periods presented. Liquidity Since inception, the Company has been involved primarily in performing research and development activities, conducting clinical trials, hiring personnel, and raising capital to support and expand these activities. The Company has experienced losses and negative cash flows from operations since its inception and, as of September 30, 2020, had an accumulated deficit of $142.8 million and cash and cash equivalents of $370.7 million. The Company has historically funded its operations through the issuance of shares of its redeemable convertible preferred stock and common stock. Based on projected activities, management projects that cash on hand is sufficient to support operations for at least the next 12 months following issuance of these condensed consolidated financial statements. Management expects to continue to incur losses and negative cash flows from operations for at least the next several years.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 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 consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States, or GAAP, and applicable rules and regulations of the SEC regarding interim financial reporting. The condensed consolidated balance sheet as of September 30, 2020, the condensed consolidated statements of operations, comprehensive loss, changes in redeemable convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2020 and 2019 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2020 and 2019 are unaudited. These unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position as of September 30, 2020 and its results of operations and cash flows for the nine months ended September 30, 2020 and 2019. The financial data and the other financial information contained in these notes to the condensed consolidated financial statements related to the three- and nine-month periods are also unaudited. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results to be expected for the year ending December 31, 2020 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2019 included herein was derived from the audited financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in the prospectus dated July 23, 2020 that forms a part of the Company's Registration Statement on Form S-1 (File No. 333-239647), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including but not limited to the fair value of common stock, redeemable convertible preferred stock, redeemable convertible preferred stock liability, stock options, income taxes and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates. Principles of Consolidation The consolidated financial statements include the operations of Annexon, Inc. and its wholly-owned subsidiary and include the results of operations and cash flows of these entities. All intercompany balances and transactions have been eliminated in consolidation. Deferred Offering Costs Deferred offering costs, consisting of legal, accounting, audit and filing fees relating to an IPO, are capitalized. As of December 31, 2019, $2.3 million of deferred offering costs were capitalized, which are included in other long-term assets in the accompanying consolidated balance sheets. In July 2020, upon the closing of the IPO, all deferred offering costs were offset against the Company’s IPO proceeds. Redeemable Convertible Preferred Stock Liability The obligation to issue additional shares of the Company’s Series C redeemable convertible preferred stock at a future date was determined to be a freestanding financial instrument that should be accounted for as a liability. At initial recognition, the Company recorded the redeemable convertible preferred stock liability on the balance sheet at its estimated fair value. The liability was subject to remeasurement at each balance sheet date, with changes in fair value recognized as gain (loss) on remeasurement of redeemable convertible preferred stock liability on the consolidated statement of operations. Upon settlement of the redeemable convertible preferred stock liability in August 2019, the Company remeasured the liability and reclassified the final value associated with the redeemable convertible preferred stock liability to the carrying value of the Series C redeemable convertible preferred stock. Foreign Currencies The Company’s reporting currency is the U.S. dollar. The functional currency of the Company’s subsidiary located in Australia is the Australian Dollar. Balance sheets prepared in the functional currencies are translated to the reporting currency at exchange rates in effect at the end of the accounting period, except for stockholders’ equity accounts, which are translated at rates in effect when these balances were originally recorded. Revenue and expense accounts are translated using a weighted-average rate during the year. The resulting foreign currency translation adjustments are recorded as a separate component of accumulated other comprehensive loss in the accompanying consolidated balance sheets. Foreign exchange translation gain (loss) for the three and nine months ended September 30, 2020 and 2019 were not material. Gains and losses resulting from exchange rate changes on transactions denominated in a currency other than the local currency are included in earnings as incurred. Research and Development Expense Research and development expenses consist primarily of direct and indirect costs incurred for the development of the Company’s product candidates. Direct expenses include (i) preclinical and clinical outside service costs associated with discovery, preclinical and clinical testing of the Company’s product candidates; (ii) professional services agreements with third-party contract organizations, investigative clinical trial sites and consultants that conduct research and development activities on the Company’s behalf; (iii) contract manufacturing costs to produce clinical trial materials; and (iv) laboratory supplies and materials. Indirect expenses include (A) compensation and personnel-related expenses (including stock-based compensation), (B) allocated expenses for facilities and depreciation; and (C) other indirect costs. Research and development costs are expensed as incurred. Payments made to third parties are under agreements that are generally cancelable by the Company. Advance payments for research and development activities are deferred as prepaid expenses. The prepaid amounts are expensed as the related services are performed. The Company estimates preclinical studies and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on the Company’s behalf. In accruing service fees, the Company estimates the period over which services will be performed and the level of effort to be expended in each period. These estimates are based on the Company’s communications with the third-party service providers and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies significantly from the estimate, the Company will adjust the accrual accordingly to reflect the best information available at the time of the financial statement issuance. The Company has not experienced any material differences between accrued costs and actual costs incurred since its inception. Stock-Based Compensation The Company accounts for stock-based compensation arrangements using a fair value method which requires the recognition of compensation expense for costs related to all stock-based payments, including stock options. The fair value method requires the Company to estimate the fair value of stock-based payment awards to employees on the date of grant using the Black-Scholes option pricing model. The Company grants certain employees performance-based stock options. For awards that include performance conditions, no compensation cost is recognized until the performance goals are probable of being met, at which time the cumulative compensation expense from the service inception date would be recognized. Stock-based compensation costs are based on the fair value of the underlying option calculated using the Black-Scholes option pricing model and recognized as expense on a straight-line basis (for all but performance based awards for which the accelerated method is used) over the requisite service period, which is the vesting period. Determining the appropriate fair value model and related assumptions requires judgment, including estimating the fair value of the underlying common stock, expected term, expected stock price volatility, risk-free interest rate and dividend yield. The Company accounts for forfeitures as they occur. Net Loss Per Share Attributable to Common Stockholders 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 for the period, without consideration for potential dilutive shares of common stock. As the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share attributable to common stockholders because the effects of potentially dilutive securities are antidilutive. Recently Adopted Accounting Pronouncements In June 2018, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2018-07, 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), , Leases Financial Instruments — Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) In June 2020, the FASB issued ASU No. 2020-05 in response to the ongoing impacts to businesses in response to the COVID-19 pandemic. ASU No. 2020-05, Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842), provides a limited deferral of the effective dates for implementing previously issued Topic 606 and Topic 842 to give some relief to businesses and the difficulties they are facing during the pandemic. The leasing standard’s effective dates are fiscal years beginning after December 15, 2019 as originally issued (ASU 2016-02) and fiscal years beginning after December 15, 2020 as amended by ASU 2019-10. As amended by ASU No. 2020-05, the leasing standard’s effective date for the Company is the fiscal years beginning after December 15, 2021. In August 2018, the FASB issued ASU No. 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines fair value based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels: • Level 1 Inputs: Unadjusted quoted prices in active markets for identical assets or liabilities accessible to the reporting entity at the measurement date. • Level 2 Inputs: Other than quoted prices included in Level 1 inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the asset or liability. • Level 3 Inputs: Unobservable inputs for the asset or liability used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at measurement date. On a recurring basis, the Company measures certain financial assets and liabilities at fair value. The following tables summarize the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): September 30, 2020 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 370,093 $ — $ — $ 370,093 Total assets $ 370,093 $ — $ — $ 370,093 December 31, 2019 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 43,621 $ — $ — $ 43,621 Total assets $ 43,621 $ — $ — $ 43,621 For the three months ended September 30, 2020 and 2019 and for the nine months ended September 30, 2020 and 2019, the Company recognized no material realized gains or losses on financial instruments. In August 2019, the redeemable convertible preferred stock liability was settled upon the completion of the second closing of the Company’s Series C redeemable convertible preferred stock financing. In light of the Company’s progress towards an IPO, the liability was remeasured at the settlement date using a probability-weighted expected return method, or PWERM, whereby the Company’s total equity value was estimated under various exit scenarios and allocated to the Company’s different classes of equity. The PWERM included two scenarios, IPO or staying private, that considered an estimate of the timing of each scenario and were weighted based on the Company’s estimate of the probability of each event occurring. The equity value under the IPO scenario was based on recent IPO values of comparable companies and weighted 50%. The equity value under the staying private scenario was based on the recent Series C redeemable convertible preferred stock financing and was weighted 50%. The liability was remeasured to its fair value of $10.8 million upon settlement and the carrying value of the liability was reclassified to the carrying value of the Series C redeemable convertible preferred stock. The Company recorded a loss of $1.3 million and $5.7 million in the condensed consolidated statements of operations for the three and nine months ended September 30, 2019, respectively, for the change in the fair value of the liability. The changes in the carrying value of the liability were as follows (in thousands): Fair value as of December 31, 2018 $ 5,140 Change in fair value 5,670 Reclassification to redeemable convertible preferred stock upon settlement (10,810 ) Fair value as of September 30, 2019 $ — There were no transfers between Levels 1, 2 or 3 for the periods presented.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2020
Disclosure Of Balance Sheet Components [Abstract]
Balance Sheet Components	4. Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): September 30, 2020 December 31, 2019 Prepaid research and development costs $ 510 $ 1,086 Prepaid expenses 2,375 310 Other receivables 4 79 Total prepaid expenses and other current assets $ 2,889 $ 1,475 Accrued Liabilities Accrued liabilities consisted of the following (in thousands): September 30, 2020 December 31, 2019 Accrued research and development expenses $ 2,630 $ 459 Accrued professional services 168 733 Accrued compensation 1,514 926 Other accrued expenses 337 76 Total accrued liabilities $ 4,649 $ 2,194

Promissory Note

Promissory Note	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Promissory Note	5. Promissory Note Pursuant to the Coronavirus Aid, Relief, and Economic Security Act, the Company obtained a $0.5 million promissory note from the U.S. Small Business Administration on April 21, 2020, which was repaid in full on May 1, 2020 .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Leases The Company leases its offices and laboratory in South San Francisco, California under a 7-year noncancelable lease agreement that ends in June 2024 with a 5-year renewal option. Rent expense is recognized on a straight-line basis over the non-cancelable term of the lease and, accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability on the accompanying condensed consolidated balance sheet. Rent expense for each of the three months ended September 30, 2020 and 2019 was $88,000. Rent expense for each of the nine months ended September 30, 2020 and 2019 was $264,000. License and Other Agreements In November 2011, the Company entered into an exclusive licensing agreement, or the Stanford Agreement, with The Board of Trustees of the Leland Stanford Junior University, or Stanford, whereby the Company was granted an exclusive, worldwide, royalty-bearing, sublicensable license, under certain patent rights, or the Licensed Patents, to make, use, offer for sale, sell, import and otherwise commercialize products covered by the Licensed Patents for human or animal diseases, disorders or conditions. Under the Stanford Agreement, the Company made an upfront payment and is obligated to pay Stanford annual license maintenance fees, potential future milestone payments totaling up to $600,000, and royalty payments at a rate equal to a low single-digit percentage of worldwide net sales of licensed products. In December 2016, the Company entered into a Sponsored Research Agreement with a not-for-profit entity to perform research on multiple sclerosis. The Sponsored Research Agreement was amended in March 2019. Under the terms of the Sponsored Research Agreement, the Company may receive up to $651,000, which was amended from $693,000, in funding. If within 15 years of the end of the Sponsored Research Agreement the Company files a marketing authorization application for a product treating multiple sclerosis, the Company will be obligated to pay milestone payments up to four times the amounts received under the Sponsored Research Agreement. The Company has received $455,000 in funding to date. The Company received $190,000 representing the final amount received under the Sponsored Research Agreement, which was recorded as other income for the nine months ended September 30, 2019. No funding was received for the three and nine months ended September 30, 2020 and the three months ended September 30, 2019. Guarantees and Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of September 30, 2020, the Company did not have any material indemnification claims that were probable or reasonably possible and consequently has not recorded related liabilities.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock and Stockholder's Equity (Deficit)	9 Months Ended
	Sep. 30, 2020
Temporary Equity [Abstract]
Redeemable Convertible Preferred Stock and Stockholder's Equity (Deficit)	7. Redeemable Convertible Preferred Stock and Stockholder’s Equity (Deficit) Redeemable Convertible Preferred Stock As of December 31, 2019, redeemable convertible preferred stock consisted of the following: Shares Authorized Shares Outstanding Net Carrying Value (in thousands) Liquidation Preference (in thousands) Series A 1,015,434 1,015,434 $ 1,000 $ 1,000 Series A-1 16,398,995 16,398,995 17,144 17,219 Series B 38,778,091 38,778,090 44,505 44,595 Series C 62,962,952 55,555,546 81,335 75,000 Total 119,155,472 111,748,065 $ 143,984 $ 137,814 In June 2020, the Company completed its financing of Series D redeemable convertible preferred stock, which resulted in the Company issuing 71,719,859 shares of Series D redeemable convertible preferred stock, including 9,773,587 shares issued to related parties who were 10% or greater holders of the Company, at a price per share of $1.4222 for aggregate proceeds of $96.8 million, net of issuance costs of $5.2 million. The shares of Series D redeemable convertible preferred stock are convertible at any time, at the holders’ option, into shares of common stock. In connection with the issuance and sale of the Series D redeemable convertible preferred stock, the Company recognized a beneficial conversion feature of approximately $6.3 million. A beneficial conversion feature represents the intrinsic value of the conversion feature, as determined by comparing the effective conversion price at the commitment date with the estimated fair value of the Company’s common stock. The beneficial conversion feature was recorded in additional paid-in capital on the issuance date resulting in a discount to the carrying value of the Series D redeemable convertible preferred stock. In July 2020, immediately prior to the completion of the IPO (see Note 1), all outstanding shares of redeemable convertible preferred stock were automatically converted into 20,824,938 shares of common stock. Common Stock The Company has reserved the following shares of common stock for issuance as follows: September 30, 2020 December 31, 2019 Redeemable convertible preferred stock outstanding on an as- converted basis — 12,684,214 Options issued and outstanding 3,514,773 2,007,222 Options available for future grant 3,103,047 454,110 Total common stock reserved 6,617,820 15,145,546

Equity Incentive Plan

Equity Incentive Plan	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plan	8. Equity Incentive Plan On July 23, 2020, the Company adopted the 2020 Incentive Award Plan, or the 2020 Plan, and the Employee Stock Purchase Plan, or the ESPP, which became effective in connection with the IPO. The Company has reserved 3,600,868 shares of common stock for future issuance under the 2020 Plan and 360,086 shares under the ESPP, respectively. As a result, the Company may not grant any additional awards under the 2011 Equity Incentive Plan (the 2011 Plan). The 2011 Plan will continue to govern outstanding equity awards granted thereunder. In addition, the number of shares of common stock reserved for issuance under the 2020 Plan will automatically increase on the first day of January, commencing on January 1, 2021 and ending in 2030, in an amount equal to 4% of the total number of shares of the Company’s capital stock outstanding on the last day of the preceding year, or a lesser number of shares determined by the Company’s board of directors. As of September 30, 2020, there were 3,103,047 shares available for issuance under the 2020 Plan. Stock option activity under the 2011 Plan and the 2020 Plan was as follows: Shares Available for Grant Number of Shares Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Balances as of December 31, 2019 454,110 2,007,222 $ 4.91 8.26 $ 21,623 Additional shares authorized 4,166,016 — Stock options granted (1,519,719 ) 1,519,719 $ 14.77 Stock options exercised — (9,528 ) $ 2.33 Stock options cancelled 2,640 (2,640 ) $ 4.67 Balances as of September 30, 2020 3,103,047 3,514,773 $ 9.18 8.48 $ 73,985 Exercisable as of September 30, 2020 1,179,057 $ 4.15 6.91 $ 30,746 There were 9,528 options exercised during the nine months ended September 30, 2020. The total intrinsic value of options exercised during the three and nine months ended September 30, 2019 was $0 and $8,000, respectively. The total intrinsic value of options exercised during each of the three and nine months ended September 30, 2020 was $0.2 million. The intrinsic value is the difference between the fair value of the Company’s common stock at the time of exercise and the exercise price of the stock option. Stock-Based Compensation Expense The total stock-based compensation expense recognized for options granted was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 624 $ 159 $ 1,284 $ 391 General and administrative 847 451 1,613 1,122 Total stock-based compensation expense $ 1,471 $ 610 $ 2,897 $ 1,513 As of September 30, 2020, the total unrecognized stock-based compensation cost related to outstanding unvested stock options that are expected to vest was $20.2 million, which the Company expects to recognize over an estimated weighted-average period of 3.21 years. To determine the value of stock option awards for stock-based compensation purposes, the Company uses the Black-Scholes option pricing model and the assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment. Expected Term —The Company’s expected term represents the period that the Company’s stock-based awards are expected to be outstanding. The Company’s historical share option exercise information is limited due to a lack of sufficient data points, and did not provide a reasonable basis upon which to estimate an expected term. The expected term for option grants is therefore determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term). Expected Volatility —Because the Company does not have sufficient trading history for its common stock, the expected volatility was estimated based on the average volatility for comparable publicly traded life science companies over a period equal to the expected term of the stock option grants. The comparable companies were chosen based on the similar size, stage in the life cycle, or area of specialty. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of the option. Dividend Yield —The Company has never paid dividends on its common stock and has no plans to pay dividends on its common stock. Therefore, the Company used an expected dividend yield of zero. The fair value of each award issued was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Expected term (in years) 6.02 - 6.08 — 5.00 - 6.08 6.02 - 6.08 Expected volatility 91% - 93% — 85% - 93% 76% -77% Risk-free interest rate 0.36% - 0.38% — 0.33% - 1.45% 1.87% - 2.61% Dividend yield — — — —

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes For the three and nine months ended September 30, 2020 and 2019, the Company incurred insignificant amounts for an income tax provision. The U.S. federal and California deferred tax assets generated from the Company’s net operating losses have been fully reserved, as the Company believes it is not more likely than not that the benefit will be realized.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	10. Net Loss Per Share Attributable to Common Stockholders The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Redeemable convertible preferred stock on an as-converted basis — 12,684,214 — 12,684,214 Stock options to purchase common stock 3,514,773 2,081,291 3,514,773 2,081,291 Total 3,514,773 14,765,505 3,514,773 14,765,505

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States, or GAAP, and applicable rules and regulations of the SEC regarding interim financial reporting. The condensed consolidated balance sheet as of September 30, 2020, the condensed consolidated statements of operations, comprehensive loss, changes in redeemable convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2020 and 2019 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2020 and 2019 are unaudited. These unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position as of September 30, 2020 and its results of operations and cash flows for the nine months ended September 30, 2020 and 2019. The financial data and the other financial information contained in these notes to the condensed consolidated financial statements related to the three- and nine-month periods are also unaudited. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results to be expected for the year ending December 31, 2020 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2019 included herein was derived from the audited financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in the prospectus dated July 23, 2020 that forms a part of the Company's Registration Statement on Form S-1 (File No. 333-239647), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including but not limited to the fair value of common stock, redeemable convertible preferred stock, redeemable convertible preferred stock liability, stock options, income taxes and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the operations of Annexon, Inc. and its wholly-owned subsidiary and include the results of operations and cash flows of these entities. All intercompany balances and transactions have been eliminated in consolidation.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, consisting of legal, accounting, audit and filing fees relating to an IPO, are capitalized. As of December 31, 2019, $2.3 million of deferred offering costs were capitalized, which are included in other long-term assets in the accompanying consolidated balance sheets. In July 2020, upon the closing of the IPO, all deferred offering costs were offset against the Company’s IPO proceeds.
Redeemable Convertible Preferred Stock Liability	Redeemable Convertible Preferred Stock Liability The obligation to issue additional shares of the Company’s Series C redeemable convertible preferred stock at a future date was determined to be a freestanding financial instrument that should be accounted for as a liability. At initial recognition, the Company recorded the redeemable convertible preferred stock liability on the balance sheet at its estimated fair value. The liability was subject to remeasurement at each balance sheet date, with changes in fair value recognized as gain (loss) on remeasurement of redeemable convertible preferred stock liability on the consolidated statement of operations. Upon settlement of the redeemable convertible preferred stock liability in August 2019, the Company remeasured the liability and reclassified the final value associated with the redeemable convertible preferred stock liability to the carrying value of the Series C redeemable convertible preferred stock.
Foreign Currencies	Foreign Currencies The Company’s reporting currency is the U.S. dollar. The functional currency of the Company’s subsidiary located in Australia is the Australian Dollar. Balance sheets prepared in the functional currencies are translated to the reporting currency at exchange rates in effect at the end of the accounting period, except for stockholders’ equity accounts, which are translated at rates in effect when these balances were originally recorded. Revenue and expense accounts are translated using a weighted-average rate during the year. The resulting foreign currency translation adjustments are recorded as a separate component of accumulated other comprehensive loss in the accompanying consolidated balance sheets. Foreign exchange translation gain (loss) for the three and nine months ended September 30, 2020 and 2019 were not material. Gains and losses resulting from exchange rate changes on transactions denominated in a currency other than the local currency are included in earnings as incurred.
Research and Development Expense	Research and Development Expense Research and development expenses consist primarily of direct and indirect costs incurred for the development of the Company’s product candidates. Direct expenses include (i) preclinical and clinical outside service costs associated with discovery, preclinical and clinical testing of the Company’s product candidates; (ii) professional services agreements with third-party contract organizations, investigative clinical trial sites and consultants that conduct research and development activities on the Company’s behalf; (iii) contract manufacturing costs to produce clinical trial materials; and (iv) laboratory supplies and materials. Indirect expenses include (A) compensation and personnel-related expenses (including stock-based compensation), (B) allocated expenses for facilities and depreciation; and (C) other indirect costs. Research and development costs are expensed as incurred. Payments made to third parties are under agreements that are generally cancelable by the Company. Advance payments for research and development activities are deferred as prepaid expenses. The prepaid amounts are expensed as the related services are performed. The Company estimates preclinical studies and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on the Company’s behalf. In accruing service fees, the Company estimates the period over which services will be performed and the level of effort to be expended in each period. These estimates are based on the Company’s communications with the third-party service providers and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies significantly from the estimate, the Company will adjust the accrual accordingly to reflect the best information available at the time of the financial statement issuance. The Company has not experienced any material differences between accrued costs and actual costs incurred since its inception.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation arrangements using a fair value method which requires the recognition of compensation expense for costs related to all stock-based payments, including stock options. The fair value method requires the Company to estimate the fair value of stock-based payment awards to employees on the date of grant using the Black-Scholes option pricing model. The Company grants certain employees performance-based stock options. For awards that include performance conditions, no compensation cost is recognized until the performance goals are probable of being met, at which time the cumulative compensation expense from the service inception date would be recognized. Stock-based compensation costs are based on the fair value of the underlying option calculated using the Black-Scholes option pricing model and recognized as expense on a straight-line basis (for all but performance based awards for which the accelerated method is used) over the requisite service period, which is the vesting period. Determining the appropriate fair value model and related assumptions requires judgment, including estimating the fair value of the underlying common stock, expected term, expected stock price volatility, risk-free interest rate and dividend yield. The Company accounts for forfeitures as they occur.
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders 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 for the period, without consideration for potential dilutive shares of common stock. As the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share attributable to common stockholders because the effects of potentially dilutive securities are antidilutive.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2018, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2018-07, 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), , Leases Financial Instruments — Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) In June 2020, the FASB issued ASU No. 2020-05 in response to the ongoing impacts to businesses in response to the COVID-19 pandemic. ASU No. 2020-05, Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842), provides a limited deferral of the effective dates for implementing previously issued Topic 606 and Topic 842 to give some relief to businesses and the difficulties they are facing during the pandemic. The leasing standard’s effective dates are fiscal years beginning after December 15, 2019 as originally issued (ASU 2016-02) and fiscal years beginning after December 15, 2020 as amended by ASU 2019-10. As amended by ASU No. 2020-05, the leasing standard’s effective date for the Company is the fiscal years beginning after December 15, 2021. In August 2018, the FASB issued ASU No. 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables summarize the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): September 30, 2020 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 370,093 $ — $ — $ 370,093 Total assets $ 370,093 $ — $ — $ 370,093 December 31, 2019 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 43,621 $ — $ — $ 43,621 Total assets $ 43,621 $ — $ — $ 43,621
Summary of Changes in the Carrying Value of the Liability	The changes in the carrying value of the liability were as follows (in thousands): Fair value as of December 31, 2018 $ 5,140 Change in fair value 5,670 Reclassification to redeemable convertible preferred stock upon settlement (10,810 ) Fair value as of September 30, 2019 $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2020
Disclosure Of Balance Sheet Components [Abstract]
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): September 30, 2020 December 31, 2019 Prepaid research and development costs $ 510 $ 1,086 Prepaid expenses 2,375 310 Other receivables 4 79 Total prepaid expenses and other current assets $ 2,889 $ 1,475
Summary of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): September 30, 2020 December 31, 2019 Accrued research and development expenses $ 2,630 $ 459 Accrued professional services 168 733 Accrued compensation 1,514 926 Other accrued expenses 337 76 Total accrued liabilities $ 4,649 $ 2,194

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock and Stockholder's Equity (Deficit) (Tables)	9 Months Ended
	Sep. 30, 2020
Temporary Equity [Abstract]
Summary of Redeemable Convertible Preferred Stock	As of December 31, 2019, redeemable convertible preferred stock consisted of the following: Shares Authorized Shares Outstanding Net Carrying Value (in thousands) Liquidation Preference (in thousands) Series A 1,015,434 1,015,434 $ 1,000 $ 1,000 Series A-1 16,398,995 16,398,995 17,144 17,219 Series B 38,778,091 38,778,090 44,505 44,595 Series C 62,962,952 55,555,546 81,335 75,000 Total 119,155,472 111,748,065 $ 143,984 $ 137,814
Schedule of Common Stock Reserved for Future Issuance	The Company has reserved the following shares of common stock for issuance as follows: September 30, 2020 December 31, 2019 Redeemable convertible preferred stock outstanding on an as- converted basis — 12,684,214 Options issued and outstanding 3,514,773 2,007,222 Options available for future grant 3,103,047 454,110 Total common stock reserved 6,617,820 15,145,546

Equity Incentive Plan (Tables)

Equity Incentive Plan (Tables)	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	Stock option activity under the 2011 Plan and the 2020 Plan was as follows: Shares Available for Grant Number of Shares Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Balances as of December 31, 2019 454,110 2,007,222 $ 4.91 8.26 $ 21,623 Additional shares authorized 4,166,016 — Stock options granted (1,519,719 ) 1,519,719 $ 14.77 Stock options exercised — (9,528 ) $ 2.33 Stock options cancelled 2,640 (2,640 ) $ 4.67 Balances as of September 30, 2020 3,103,047 3,514,773 $ 9.18 8.48 $ 73,985 Exercisable as of September 30, 2020 1,179,057 $ 4.15 6.91 $ 30,746
Summary of Stock-Based Compensation Expense	The total stock-based compensation expense recognized for options granted was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 624 $ 159 $ 1,284 $ 391 General and administrative 847 451 1,613 1,122 Total stock-based compensation expense $ 1,471 $ 610 $ 2,897 $ 1,513
Summary of Fair Value of Each Award Issued Estimated on the Date of Grant Using the Black-Scholes Option Pricing Model	The fair value of each award issued was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Expected term (in years) 6.02 - 6.08 — 5.00 - 6.08 6.02 - 6.08 Expected volatility 91% - 93% — 85% - 93% 76% -77% Risk-free interest rate 0.36% - 0.38% — 0.33% - 1.45% 1.87% - 2.61% Dividend yield — — — —

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Summary of Outstanding Potentially Dilutive Shares Excluded From Calculation of Diluted Net Loss Per Share	The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Redeemable convertible preferred stock on an as-converted basis — 12,684,214 — 12,684,214 Stock options to purchase common stock 3,514,773 2,081,291 3,514,773 2,081,291 Total 3,514,773 14,765,505 3,514,773 14,765,505

Organization - Additional Infor

Organization - Additional Information (Detail) $ / shares in Units, $ in Thousands	Aug. 04, 2020shares	Jul. 24, 2020USD ($)$ / sharesshares	Jul. 17, 2020	Sep. 30, 2020USD ($)shares	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Proceeds from issuance of common stock upon initial public offering, net of underwriting discounts and commissions		$ 262,400			$ 267,021
Payment of deferred offering costs					2,974	$ 759
Redeemable convertible preferred stock, shares issued upon conversion | shares		20,824,938
Accumulated deficit				$ (142,799)	(142,799)		$ (102,580)
Cash and cash equivalents				$ 370,686	$ 370,686	$ 53,662	$ 43,931	$ 44,175
Common Stock [Member]
Shares issued during the period | shares				16,889,403
Payment of deferred offering costs				$ 24,700
Description of reverse stock split			one-for-8.81 basis
Reverse stock split, conversion ratio			0.113507378
IPO [Member]
Shares issued during the period | shares		14,750,000
Shares issued price per share | $ / shares		$ 17
Payments for underwriting expense		$ 20,100
Payment of deferred offering costs		$ 4,600
Over-Allotment Option [Member]
Shares issued during the period | shares	2,139,403

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Basis Of Presentation And Significant Accounting Policies [Line Items]
Deferred offering costs		$ 2.3
ASU 2018-07 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Change in accounting principle, ASU adopted	true
Change in accounting principle, ASU, adoption date	Jan. 1, 2020
Change in accounting principle, ASU, Immaterial effect	true
ASU 2018-13 [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Change in accounting principle, ASU adopted	true
Change in accounting principle, ASU, adoption date	Jan. 1, 2020
Change in accounting principle, ASU, Immaterial effect	true

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Total assets	$ 370,093	$ 43,621
Level 1 [Member]
Assets:
Total assets	370,093	43,621
Money Market Funds [Member]
Assets:
Total assets	370,093	43,621
Money Market Funds [Member] | Level 1 [Member]
Assets:
Total assets	$ 370,093	$ 43,621

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liability remeasured to its fair value					$ 5,140,000
Operational loss	$ 1,300,000		$ 5,670,000
Fair value assets, level 1 to level 2 transfers amount		$ 0		$ 0
Fair value assets, level 2 to level 1 transfers amount		0		0
Fair value asset, transfers into level 3		0		0
Fair value asset, transfers out of level 3		0		0
Fair value liabilities, level 1 to level 2 transfers amount		0		0
Fair value liabilities, level 2 to level 1 transfers amount		0		0
Fair value liabilities, transfers into level 3		0		0
Fair value liabilities, transfers out of level 3		0		$ 0
Redeemable Convertible Preferred Stock Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liability remeasured to its fair value		$ 10,800,000
IPO Scenario [Member] | Redeemable Convertible Preferred Stock Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Weighted average equity value percentage		50.00%
Staying Private Scenario [Member] | Redeemable Convertible Preferred Stock Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Weighted average equity value percentage		50.00%

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Changes in the Carrying Value of the Liability (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Fair value as of December 31, 2018		$ 5,140
Change in fair value	$ 1,300	5,670
Reclassification to redeemable convertible preferred stock upon settlement		$ (10,810)

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Prepaid Expense And Other Assets Current [Abstract]
Prepaid research and development costs	$ 510	$ 1,086
Prepaid expenses	2,375	310
Other receivables	4	79
Total prepaid expenses and other current assets	$ 2,889	$ 1,475

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities Current [Abstract]
Accrued research and development expenses	$ 2,630	$ 459
Accrued professional services	168	733
Accrued compensation	1,514	926
Other accrued expenses	337	76
Total accrued liabilities	$ 4,649	$ 2,194

Promissory Note - Additional In

Promissory Note - Additional Information (Detail) - USD ($) $ in Thousands	May 01, 2020	Apr. 21, 2020	Sep. 30, 2020
Short Term Debt [Line Items]
Proceeds from short term notes payable			$ 500
Repayment of short term notes payable			$ 500
U S Small Business Administration Loan [Member]
Short Term Debt [Line Items]
Proceeds from short term notes payable		$ 500
Repayment of short term notes payable	$ 500

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended		3 Months Ended		9 Months Ended		46 Months Ended
	Mar. 31, 2019USD ($)	Nov. 30, 2011USD ($)	Sep. 30, 2020USD ($)Claim	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)Claim	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)Claim	Dec. 31, 2016USD ($)
Gain Contingencies [Line Items]
Operating lease, term of contract			7 years		7 years		7 years
Operating lease, expiration month and year					Jun. 30, 2024
Operating lease, renewal term			5 years		5 years		5 years
Operating leases, rent expense			$ 88,000	$ 88,000	$ 264,000	$ 264,000
Loss contingency accrual			$ 0		$ 0		$ 0
Indemnification Agreement [Member]
Gain Contingencies [Line Items]
Loss contingency pending claims | Claim			0		0		0
Stanford Agreement [Member] | Research and Development Arrangement [Member]
Gain Contingencies [Line Items]
Sponsor research agreements, commitment amount		$ 600,000
Sponsored Research Agreement [Member]
Gain Contingencies [Line Items]
Maximum threshold period allowed for filing market authorization	15 years
Proceeds from funding							$ 455,000
Sponsored Research Agreement [Member] | Other Income [Member]
Gain Contingencies [Line Items]
Proceeds from funding			$ 0	$ 0	$ 0	$ 190,000
Sponsored Research Agreement [Member] | Research and Development Arrangement [Member]
Gain Contingencies [Line Items]
Maximum expected research funding	$ 651,000							$ 693,000

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock and Stockholder's Equity (Deficit) - Summary of Redeemable Convertible Preferred Stock (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Series A [Member]
Temporary Equity [Line Items]
Shares Authorized				1,015,434
Shares Outstanding				1,015,434
Net Carrying Value				$ 1,000
Liquidation Preference				$ 1,000
Series A-1 [Member]
Temporary Equity [Line Items]
Shares Authorized				16,398,995
Shares Outstanding				16,398,995
Net Carrying Value				$ 17,144
Liquidation Preference				$ 17,219
Series B [Member]
Temporary Equity [Line Items]
Shares Authorized				38,778,091
Shares Outstanding				38,778,090
Net Carrying Value				$ 44,505
Liquidation Preference				$ 44,595
Series C [Member]
Temporary Equity [Line Items]
Shares Authorized				62,962,952
Shares Outstanding				55,555,546
Net Carrying Value				$ 81,335
Liquidation Preference				$ 75,000
Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	0			119,155,472
Shares Outstanding	0	183,467,924	111,748,065	111,748,065	111,748,065	89,525,848	89,525,848	89,525,848
Net Carrying Value				$ 143,984
Liquidation Preference	$ 0			$ 137,814

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock and Stockholder's Equity (Deficit) - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jul. 24, 2020	Jun. 30, 2020	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Temporary Equity [Line Items]
Aggregate proceeds from redeemable convertible preferred stock						$ 102,000	$ 29,997
Net issuance cost						2,974	759
Recognized a beneficial conversion feature			$ 145		$ 281	705	$ 815
Conversion of redeemable preferred stock into common shares	20,824,938
Increase in the carrying value of redeemable convertible preferred stock	$ 6,200
Carrying value of the redeemable convertible preferred stock reclassified to equity	$ 241,400					$ 6,297
Series D Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock issued		71,719,859
Redeemable convertible preferred stock issue price per share		$ 1.4222		$ 1.4222
Aggregate proceeds from redeemable convertible preferred stock		$ 96,800
Net issuance cost		5,200		$ 5,193
Recognized a beneficial conversion feature		$ 6,300
Series D Preferred Stock [Member] | Principal Owner [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock issued		9,773,587

Redeemable Convertible Prefer_5

Redeemable Convertible Preferred Stock and Stockholder's Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Detail) - shares	Sep. 30, 2020	Jul. 24, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Redeemable convertible preferred stock outstanding on an as- converted basis		20,824,938
Options issued and outstanding	3,514,773		2,007,222
Options available for future grant	3,103,047		454,110
Total common stock reserved	6,617,820		15,145,546
Redeemable Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Redeemable convertible preferred stock outstanding on an as- converted basis			12,684,214
Options Issued and Outstanding [Member]
Class of Stock [Line Items]
Options issued and outstanding	3,514,773		2,007,222
Options Available for Future Grant [Member]
Class of Stock [Line Items]
Options available for future grant	3,103,047		454,110

Equity Incentive Plan - Additio

Equity Incentive Plan - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jul. 23, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock for future issuance	6,617,820		6,617,820			15,145,546
Percentage of number of shares of capital stock outstanding on last day of preceding year			4.00%
Options available for future grant	3,103,047		3,103,047			454,110
Options exercised			9,528
Intrinsic value of options exercised	$ 200,000	$ 0	$ 200,000	$ 8,000
Unrecognized stock-based compensation cost	$ 20,200,000		$ 20,200,000
Unrecognized stock-based compensation cost expected period for recognition			3 years 2 months 15 days
2020 Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock for future issuance					3,600,868
Options available for future grant	3,103,047		3,103,047
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock for future issuance					360,086

Equity Incentive Plan - Summary

Equity Incentive Plan - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares available for grant, Beginning balance	454,110
Shares available for grant, Additional shares authorized	4,166,016
Shares available for grant, Stock options granted	(1,519,719)
Shares available for grant, Stock options exercised	(9,528)
Shares available for grant, Stock options cancelled	2,640
Shares available for grant, Ending balance	3,103,047	454,110
Shares available for grant, Exercisable	1,179,057
Number of shares, Beginning balance	2,007,222
Number of shares, Stock options granted	1,519,719
Number of shares, Stock options cancelled	(2,640)
Number of shares, Ending balance	3,514,773	2,007,222
Weighted- average exercise price per share, Beginning balance | $ / shares	$ 4.91
Weighted- average exercise price per share, Stock options granted | $ / shares	14.77
Weighted- average exercise price per share, Stock options exercised | $ / shares	2.33
Weighted- average exercise price per share, Stock options cancelled | $ / shares	4.67
Weighted- average exercise price per share, Ending balance | $ / shares	9.18	$ 4.91
Weighted- average exercise price per share, Exercisable | $ / shares	$ 4.15
Weighted- average remaining contractual term	8 years 5 months 23 days	8 years 3 months 3 days
Weighted- average remaining contractual term, Exercisable	6 years 10 months 28 days
Aggregate intrinsic value | $	$ 73,985	$ 21,623
Aggregate intrinsic value, Exercisable | $	$ 30,746

Equity Incentive Plan - Summa_2

Equity Incentive Plan - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,471	$ 610	$ 2,897	$ 1,513
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	624	159	1,284	391
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 847	$ 451	$ 1,613	$ 1,122

Equity Incentive Plan - Summa_3

Equity Incentive Plan - Summary of Fair Value of Each Award Issued Estimated on the Date of Grant Using the Black-Scholes Option Pricing Model (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, Minimum	91.00%	85.00%	76.00%
Expected volatility, Maximum	93.00%	93.00%	77.00%
Risk-free interest rate, Minimum	0.36%	0.33%	1.87%
Risk-free interest rate, Maximum	0.38%	1.45%	2.61%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 7 days	5 years	6 years 7 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Summary of Outstanding Potentially Dilutive Shares Excluded From Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	3,514,773	14,765,505	3,514,773	14,765,505
Redeemable Convertible Preferred Stock on an as-converted Basis [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share		12,684,214		12,684,214
Stock Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	3,514,773	2,081,291	3,514,773	2,081,291