Praxis Precision Medicines (PRAX) 10-Q 23 Nov 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Nov. 13, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Registrant Name	Praxis Precision Medicines, Inc.
Entity Central Index Key	0001689548
Entity Address, State or Province	MA
Current Fiscal Year End Date	--12-31
Title of 12(b) Security	Common Stock
Trading Symbol	PRAX
Security Exchange Name	NASDAQ
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Small Business	true
Entity Common Stock, Shares Outstanding		38,261,893

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 114,772	$ 44,815
Prepaid expenses and other current assets	1,079	681
Total current assets	115,851	45,496
Property and equipment, net	98	128
Restricted cash	600	600
Operating lease right-of-use assets	933	1,450
Other assets	2,066	20
Total assets	119,548	47,694
Current liabilities:
Accounts payable	3,452	2,667
Accrued expenses	6,186	3,455
Operating lease liabilities	746	696
Total current liabilities	10,384	6,818
Long-term liabilities:
Non-current portion of operating lease liabilities	198	763
Total liabilities	10,582	7,581
Commitments and contingencies (Note 5)
Stockholders' deficit:
Common stock, $0.0001 par value; 70,500,000 shares authorized as of September 30, 2020 and 46,000,000 shares authorized as of December 31, 2019; 1,681,698 shares issued and 1,672,935 shares outstanding as of September 30, 2020 and 1,670,070 shares issued and 1,621,880 shares outstanding as of December 31, 2019	1	1
Accumulated deficit	(123,264)	(81,009)
Total stockholders' deficit	(123,263)	(81,008)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	119,548	47,694
Series A redeemable convertible preferred stock [Member]
Liabilities, redeemable convertible preferred stock and stockholders' deficit
Redeemable convertible preferred stock	10,416	9,932
Series B redeemable convertible preferred stock [Member]
Liabilities, redeemable convertible preferred stock and stockholders' deficit
Redeemable convertible preferred stock	52,648	49,969
Series B-1 redeemable convertible preferred stock [Member]
Liabilities, redeemable convertible preferred stock and stockholders' deficit
Redeemable convertible preferred stock	11,029	10,431
Series C redeemable convertible preferred stock [Member]
Liabilities, redeemable convertible preferred stock and stockholders' deficit
Redeemable convertible preferred stock	46,244	$ 50,789
Series C-1 redeemable convertible preferred stock [Member]
Liabilities, redeemable convertible preferred stock and stockholders' deficit
Redeemable convertible preferred stock	$ 111,892

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Redeemable convertible preferred stock, shares authorized	53,644,314	36,724,132
Redeemable convertible preferred stock, shares issued	53,644,314	35,461,996
Redeemable convertible preferred stock, shares outstanding	53,644,314	35,461,996
Redeemable convertible preferred stock, liquidation preference	$ 232,229	$ 121,121
Common stock, par value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	70,500,000	46,000,000
Common stock, shares, issued	1,681,698	1,670,070
Common stock, shares, outstanding	1,672,935	1,621,880
Series A redeemable convertible preferred stock [Member]
Redeemable convertible preferred stock, par value per share	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	8,075,799	8,075,799
Redeemable convertible preferred stock, shares issued	8,075,799	8,075,799
Redeemable convertible preferred stock, shares outstanding	8,075,799	8,075,799
Redeemable convertible preferred stock, liquidation preference	$ 10,416	$ 9,932
Series B redeemable convertible preferred stock [Member]
Redeemable convertible preferred stock, par value per share	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	14,913,704	14,913,704
Redeemable convertible preferred stock, shares issued	14,913,704	14,913,704
Redeemable convertible preferred stock, shares outstanding	14,913,704	14,913,704
Redeemable convertible preferred stock, liquidation preference	$ 52,648	$ 49,969
Series B-1 redeemable convertible preferred stock [Member]
Redeemable convertible preferred stock, par value per share	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	2,666,666	2,666,666
Redeemable convertible preferred stock, shares issued	2,666,666	2,666,666
Redeemable convertible preferred stock, shares outstanding	2,666,666	2,666,666
Redeemable convertible preferred stock, liquidation preference	$ 11,029	$ 10,431
Series C redeemable convertible preferred stock [Member]
Redeemable convertible preferred stock, par value per share	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	8,543,692	11,067,963
Redeemable convertible preferred stock, shares issued	8,543,692	9,805,827
Redeemable convertible preferred stock, shares outstanding	8,543,692	9,805,827
Redeemable convertible preferred stock, liquidation preference	$ 46,244	$ 50,789
Series C-1 redeemable convertible preferred stock [Member]
Redeemable convertible preferred stock, par value per share	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	19,444,453	0
Redeemable convertible preferred stock, shares issued	19,444,453	0
Redeemable convertible preferred stock, shares outstanding	19,444,453	0
Redeemable convertible preferred stock, liquidation preference	$ 111,892	$ 0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating expenses:
Research and development	$ 12,786	$ 9,346	$ 28,704	$ 23,858
General and administrative	3,431	1,308	7,552	4,437
Total operating expenses	16,217	10,654	36,256	28,295
Loss from operations	(16,217)	(10,654)	(36,256)	(28,295)
Other income:
Interest income	1	48	134	171
Total other income	1	48	134	171
Loss before benefit from income taxes	(16,216)	(10,606)	(36,122)	(28,124)
Benefit from income taxes			(8)
Net loss and comprehensive loss	(16,216)	(10,606)	(36,114)	(28,124)
Accretion and cumulative dividends on redeemable convertible preferred stock	(3,943)	(1,267)	(8,046)	(3,450)
Gain on repurchase of redeemable convertible preferred stock			493
Net loss attributable to common stockholders	$ (20,159)	$ (11,873)	$ (43,667)	$ (31,574)
Net loss per share attributable to common stockholders, basic and diluted	$ (12.10)	$ (7.61)	$ (26.53)	$ (21.02)
Weighted average common shares outstanding, basic and diluted	1,665,902	1,559,800	1,645,982	1,501,908

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Series A redeemable convertible preferred stock [Member]	Series B redeemable convertible preferred stock [Member]	Series B-1 redeemable convertible preferred stock [Member]	Series C redeemable convertible preferred stock [Member]	Series C redeemable convertible preferred stock [Member]Accumulated Deficit [Member]	Series C-1 redeemable convertible preferred stock [Member]
Beginning balance at Dec. 31, 2018					$ 9,284	$ 46,436
Beginning balance, Shares at Dec. 31, 2018					8,075,799	14,913,704
Beginning balance at Dec. 31, 2018	$ (41,038)	$ 1	$ 326	$ (41,365)
Beginning balance, Shares at Dec. 31, 2018		1,408,677
Issuance of redeemable convertible preferred stock, net of issuance costs							$ 9,939
Issuance of redeemable convertible preferred stock, net of issuance costs, shares							2,666,666
Stock-based compensation expense	510		510
Accretion of redeemable convertible preferred stock to redemption value	3,405		836	2,569	$ 485	$ 2,630	$ 290
Vesting of restricted stock awards		175,233
Net loss	(28,124)			(28,124)
Ending balance at Sep. 30, 2019					$ 9,769	$ 49,066	$ 10,229
Ending balance, shares at Sep. 30, 2019					8,075,799	14,913,704	2,666,666
Ending balance at Sep. 30, 2019	(72,057)	$ 1		(72,058)
Ending balance, shares at Sep. 30, 2019		1,583,910
Beginning balance at Jun. 30, 2019					$ 9,606	$ 48,164	$ 10,027
Beginning balance, Shares at Jun. 30, 2019					8,075,799	14,913,704	2,666,666
Beginning balance at Jun. 30, 2019	(60,460)	$ 1		(60,461)
Beginning balance, Shares at Jun. 30, 2019		1,525,500
Stock-based compensation expense	276		276
Accretion of redeemable convertible preferred stock to redemption value	1,267		276	991	$ 163	$ 902	$ 202
Vesting of restricted stock awards		58,410
Net loss	(10,606)			(10,606)
Ending balance at Sep. 30, 2019					$ 9,769	$ 49,066	$ 10,229
Ending balance, shares at Sep. 30, 2019					8,075,799	14,913,704	2,666,666
Ending balance at Sep. 30, 2019	$ (72,057)	$ 1		(72,058)
Ending balance, shares at Sep. 30, 2019		1,583,910
Beginning balance at Dec. 31, 2019					$ 9,932	$ 49,969	$ 10,431	$ 50,789
Beginning balance, Shares at Dec. 31, 2019	35,461,996				8,075,799	14,913,704	2,666,666	9,805,827		0
Beginning balance at Dec. 31, 2019	$ (81,008)	$ 1		(81,009)
Beginning balance, Shares at Dec. 31, 2019	1,621,880	1,621,880
Repurchase of redeemable convertible preferred stock								$ (30,493)
Repurchase of redeemable convertible preferred stock, shares								(5,825,243)
Repurchase of Series C redeemable convertible preferred stock	$ 493			493					$ 500
Issuance of redeemable convertible preferred stock, net of issuance costs								$ 23,459		$ 110,096
Issuance of redeemable convertible preferred stock, net of issuance costs, shares								4,563,108		19,444,453
Stock-based compensation expense	1,385		1,385
Issuance of common stock upon exercise of stock options	$ 27		27
Issuance of common stock upon exercise of stock options, shares	11,628	11,628
Accretion of redeemable convertible preferred stock to redemption value	$ 8,046		1,412	6,634	$ 484	$ 2,679	$ 598	$ 2,489		$ 1,796
Vesting of restricted stock awards		39,427
Net loss	$ (36,114)			(36,114)
Ending balance at Sep. 30, 2020					$ 10,416	$ 52,648	$ 11,029	$ 46,244		$ 111,892
Ending balance, shares at Sep. 30, 2020	53,644,314				8,075,799	14,913,704	2,666,666	8,543,692		19,444,453
Ending balance at Sep. 30, 2020	$ (123,263)	$ 1		(123,264)
Ending balance, shares at Sep. 30, 2020	1,672,935	1,672,935
Beginning balance at Jun. 30, 2020					$ 10,254	$ 51,749	$ 10,828	$ 45,359
Beginning balance, Shares at Jun. 30, 2020					8,075,799	14,913,704	2,666,666	8,543,692
Beginning balance at Jun. 30, 2020	$ (104,084)	$ 1		(104,085)
Beginning balance, Shares at Jun. 30, 2020		1,648,165
Issuance of redeemable convertible preferred stock, net of issuance costs										$ 110,096
Issuance of redeemable convertible preferred stock, net of issuance costs, shares										19,444,453
Stock-based compensation expense	953		953
Issuance of common stock upon exercise of stock options	27		27
Issuance of common stock upon exercise of stock options, shares		11,628
Accretion of redeemable convertible preferred stock to redemption value	3,943		$ 980	2,963	$ 162	$ 899	$ 201	$ 885		$ 1,796
Vesting of restricted stock awards		13,142
Net loss	$ (16,216)			(16,216)
Ending balance at Sep. 30, 2020					$ 10,416	$ 52,648	$ 11,029	$ 46,244		$ 111,892
Ending balance, shares at Sep. 30, 2020	53,644,314				8,075,799	14,913,704	2,666,666	8,543,692		19,444,453
Ending balance at Sep. 30, 2020	$ (123,263)	$ 1		$ (123,264)
Ending balance, shares at Sep. 30, 2020	1,672,935	1,672,935

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Payments Of Stock Issuance Costs		$ 1,117
Series C-1 redeemable convertible preferred stock [Member]
Payments Of Stock Issuance Costs	$ 154	154
Series C redeemable convertible preferred stock [Member]
Payments Of Stock Issuance Costs		$ 41
Series B-1 redeemable convertible preferred stock [Member]
Payments Of Stock Issuance Costs			$ 61

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (36,114)	$ (28,124)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	30	27
Stock-based compensation expense	1,385	510
Non-cash operating lease expense	517	477
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(398)	829
Accounts payable	544	(356)
Accrued expenses	2,160	3,664
Operating lease liabilities	(515)	(468)
Other	(4)	(25)
Net cash used in operating activities	(32,395)	(23,466)
Cash flows from investing activities:
Purchases of property and equipment		(103)
Net cash used in investing activities		(103)
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	133,442	9,939
Repurchase of Series C redeemable convertible preferred stock	(30,000)
Payment of deferred offering costs	(1,117)
Proceeds from exercise of options to purchase common stock	27
Net cash provided by financing activities	102,352	9,939
Increase (decrease) in cash, cash equivalents and restricted cash	69,957	(13,630)
Cash, cash equivalents and restricted cash, beginning of period	45,415	18,550
Cash, cash equivalents and restricted cash, end of period	115,372	4,920
Supplemental disclosures of non-cash activities:
Accretion of redeemable convertible preferred stock to redemption value	8,046	3,405
Operating lease liabilities recorded upon adoption of ASC 842		$ 2,092
Deferred offering costs included in accounts payable and accrued expenses	$ 925

Nature of the Business

Nature of the Business	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business	1. Nature of the Business Praxis Precision Medicines, Inc. (“Praxis” or the “Company”) is a clinical-stage biopharmaceutical company translating genetic insights into the development of therapies for central nervous system (“CNS”) disorders characterized by neuronal imbalance. The Company has established a broad portfolio, including five disclosed programs across multiple CNS disorders, including depression, epilepsy, movement disorders and pain syndromes, with three clinical-stage product candidates. The Company’s most advanced programs, PRAX-114 PRAX-944, Phase 2 PRAX-114 PRAX-944 T-type plans Praxis was incorporated in 2015 and commenced operations in 2016. The Company has funded its operations primarily with proceeds from the issuance of convertible debt, Series A redeemable convertible preferred stock (the “Series A Preferred Stock”), Series B redeemable convertible preferred stock (the “Series B Preferred Stock”), Series B-1 B-1 C-1 C-1 B-1 C-1 On October 8, 2020, the board of directors and the Company’s stockholders approved a one-for-2.14 paid-in On October 20, 2020, the Company completed its initial public offering (“IPO”), in which the Company issued and sold 11,500,000 shares of its common stock at a public offering price of $19.00 per share, including 1,500,000 shares of common stock sold pursuant to the underwriters’ exercise of their option to purchase additional shares of common stock, for aggregate gross proceeds of $218.5 million. The Company raised approximately $199.9 million in net proceeds after deducting underwriting discounts and commissions and offering expenses payable by the Company. Upon the closing of the IPO, all of the outstanding shares of the Company’s Preferred Stock automatically converted into 25,067,977 shares of common stock. On October 20, 2020, in connection with the closing of the IPO, the Company filed its which provides that The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including but not limited to, risks associated with completing preclinical studies and clinical trials, receiving regulatory approvals for product candidates, development by competitors of new biopharmaceutical products, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Programs currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize revenue from product sales. Liquidity In accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40) The Company has incurred recurring losses since its inception, including net losses of $36.1 million and $28.1 million for the nine months ended September 30, 2020 and 2019, respectively. In addition, as of September 30, 2020, the Company had an accumulated deficit of $123.3 million. The Company expects to continue to generate operating losses for the foreseeable future. The Company previously identified conditions and events that raised substantial doubt about its ability to continue as a going concern. As a result of the completion of its IPO, the Company expects that its cash and cash equivalents as of September 30, 2020 of $114.8 million, in addition to the net proceeds of $199.9 million from its IPO, will be sufficient to fund the operating expenses and capital expenditure requirements necessary to advance its research efforts and clinical trials for at least one year from the date of issuance of these condensed consolidated financial statements. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations. The Company’s inability to raise capital as and when needed could have a negative impact on its financial condition and ability to pursue its business strategies. There can be no assurance that the current operating plan will be achieved or that additional funding will be available on terms acceptable to the Company, or at all.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and ASUs of the FASB. The Company’s significant accounting policies are disclosed in the audited consolidated financial statements included in the Company’s final prospectus filed with the Securities and Exchange Commission (“SEC”) pursuant to Rule 424(b)(4) on October 16, 2020. Since the date of those audited consolidated financial statements, there have been no changes to the Company’s significant accounting policies except as noted below. Unaudited Interim Condensed Consolidated Financial Information The accompanying condensed consolidated balance sheet as of September 30, 2020, the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019, the condensed consolidated statements of cash flows for the nine months ended September 30, 2020 and 2019 and the condensed consolidated statements of redeemable convertible preferred stock and stockholders’ deficit for the three and nine months ended September 30, 2020 and 2019 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual consolidated financial statements, and in the opinion of management reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the Company’s financial position as of September 30, 2020, the results of its operations for the three and nine months ended September 30, 2020 and 2019 and its cash flows for the nine months ended September 30, 2020 and 2019. Financial statement disclosures for the three and nine months ended September 30, 2020 and 2019 are condensed and do not include all disclosures required for an annual set of financial statements in accordance with GAAP. The results for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ended December 31, 2020, any other interim periods, or any future year or period. Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual for research and development expenses, stock-based compensation expense, and the valuation of equity awards . Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ materially from those estimates. Cash, Cash Equivalents and Restricted Cash The following table reconciles cash, cash equivalents and restricted cash to the total amounts on the condensed consolidated statements of cash flows (in thousands): September 30, 2020 2019 Cash and cash equivalents $ 114,772 $ 4,320 Restricted cash 600 600 Total cash, cash equivalents and restricted cash as shown in the condensed consolidated statement of cash flows $ 115,372 $ 4,920 Deferred Offering Costs The Company capitalizes certain legal, accounting and other third-party fees that are directly associated with in-process equity additional paid-in capital Stock-Based Compensation The Company utilizes significant estimates and assumptions in determining the fair value of its equity and equity-based awards. Beginning in the nine months ended September 30, 2020, the Company determined the fair value of shares of its common stock underlying stock-based awards granted using a hybrid probability-weighted expected return method (“PWERM”). The fair value of the Company’s common stock was calibrated to contemporaneous transactions in the Series C Preferred Stock and Series C-1 Other than as noted herein, there were no other changes to the Company’s stock-based compensation policy since the date of the audited consolidated financial statements included in the Company’s final prospectus filed pursuant to Rule 424(b)(4) on October 16, 2020. Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ deficit that are excluded from net loss. The Company’s comprehensive loss was equal to net loss for the three and nine months ended September 30, 2020 and 2019. Net Loss per Share The Company follows the two-class two-class two-class two-class Net loss attributable to common stockholders is equal to the net loss for the period, as adjusted for: (i) cumulative dividends accrued for redeemable convertible preferred stock, whether or not declared, (ii) increases in carrying value recorded for redeemable convertible preferred stock, including accretion on redeemable convertible preferred stock to redemption value for amounts other than cumulative dividends and (iii) gains on the redemptions of redeemable convertible preferred stock. Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, which excludes shares of restricted common stock that are not vested. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, after giving consideration to the dilutive effect of potentially dilutive common shares. For purposes of this calculation, outstanding options to purchase shares of common stock, unvested shares of restricted common stock and shares of redeemable convertible preferred stock are considered potentially dilutive common shares. The Company has generated a net loss in all periods presented so the basic and diluted net loss per share attributable to common stockholders are the same as the inclusion of the potentially dilutive securities would be anti-dilutive.

Fair Value of Financial Assets

Fair Value of Financial Assets	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets	3. Fair Value of Financial Assets The following tables present information about the Company’s financial assets measured at fair value on a recurring ba s hierarchy As of September 30, 2020 Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 114,386 $ — $ — $ 114,386 $ 114,386 $ — $ — $ 114,386 As of December 31, 2019 Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 44,429 $ — $ — $ 44,429 $ 44,429 $ — $ — $ 44,429

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2020
Payables and Accruals [Abstract]
Accounts Payable and Accrued Liabilities Disclosure [Text Block]	4. Accrued Expenses Accrued expenses consisted of the following (in thousands): September 30, 2020 December 31, 2019 Accrued external research and development expenses $ 3,370 $ 1,552 Accrued personnel-related expenses 1,606 1,059 Accrued license fees — 363 Accrued professional services 1,135 110 Accrued other 75 371 Total accrued expenses $ 6,186 $ 3,455

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure [Text Block]	5. Commitments and Contingencies In October 2018, the Company entered into a sublease agreement for office space located in Cambridge, Massachusetts that expires on December 30, 2021, with no option to renew or terminate early. The base rent increases by approximately 1% annually. The Company issued a letter of credit to the landlord related to the security deposit, secured by restricted cash, which is reflected as a non-current asset on the accompanying condensed consolidated balance sheets. This lease qualifies as an operating lease. In January 2019, the Company entered into an arrangement with a third party to sublease a portion of its Cambridge, Massachusetts office space. This sublease was terminated in November 2019.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2020
Temporary Equity [Abstract]
Redeemable Convertible Preferred Stock	6. Redeemable Convertible Preferred Stock As of September 30, 2020, the authorized capital stock of the Company included 53,644,314 shares of $0.0001 par value Preferred Stock, of which 8,075,799 shares were designated as Series A Preferred Stock, 14,913,704 shares were designated as Series B Preferred Stock, 2,666,666 shares were designated as Series B-1 C-1 B-1 B-1 On January 20, 2020, the Company granted two investors holding 5,825,243 shares of Series C Preferred Stock that were purchased in December 2019 the option to put their shares back to the Company at the original issuance price. On February 19, 2020 and March 3, 2020, the investors exercised their put option in full via the execution of Stock Redemption and Release Agreements in order to effect the repurchase. Pursuant to the Stock Redemption and Release Agreements, the Company agreed to repurchase a total of 5,825,243 shares of Series C Preferred Stock at the original issuance price of $5.15 per share, for an aggregate cash repurchase price of $30.0 million. Under the terms of the Stock Redemption and Release Agreements, the investors waived their right to cumulative dividends that had accumulated from the original issuance date through the date of repurchase. The 5,825,243 shares of Series C Preferred Stock were retired upon repurchase, and subsequently authorized for reissuance pursuant to a waiver to the Company’s Amended and Restated Certificate of Incorporation entered into by the Company and the holders of the Preferred Stock. The Company determined that the additional put right that was granted to the investors represented a modification of the affected shares of Series C Preferred Stock, but that it did not result in incremental value to the shareholders. As there was no incremental value associated with the modification, there was no impact to the accounting for the Series C Preferred Stock. The Company also determined that the put right did not require bifurcation, as it does not contain the characteristics of a derivative instrument. Further, the Company determined that the shares of Series C Preferred Stock that were subject to repurchase did not become mandatorily redeemable until the execution of the Stock Redemption and Release Agreements because the parties did not have an unconditional legal obligation to complete the redemptions until the associated agreements were finalized. Such determination was made in consultation with legal counsel. Accordingly, the Company recorded each of the redemptions on the respective date of repurchase and recognized a gain on repurchase equal to the difference between the repurchase price and the carrying value of the Series C Preferred Stock on the respective date of repurchase. The aggregate gain of $0.5 million was recorded upon repurchase as an adjustment to accumulated deficit in the statement of redeemable convertible preferred stock and stockholders’ deficit. The gain relates exclusively to the dividends accrued on the repurchased shares, which were waived by the investors as part of the Stock Redemption and Release Agreements. On April 15, 2020 and May 8, 2020, the Company completed additional closings for the sale and issuance of its Series C Preferred Stock for a total of 4,563,108 shares at $5.15 per share for aggregate cash proceeds of $23.5 million, less an immaterial amount of issuance costs. On July 24, 2020, the Company entered into the Series C-1 , C-1 C-1 C-1 C-1 C-1 C-1 C-1 B-1 B-1 The Preferred Stock consisted of the following (in thousands, except share amounts): As of September 30, 2020 Shares Authorized Preferred Stock Issued and Outstanding Carrying Value Liquidation Preference Redemption Value Common Stock Issuable Upon Conversion Series A Preferred Stock 8,075,799 8,075,799 $ 10,416 $ 10,416 $ 10,416 3,773,820 Series B Preferred Stock 14,913,704 14,913,704 52,648 52,648 52,648 6,969,173 Series B-1 2,666,666 2,666,666 11,029 11,029 11,029 1,246,133 Series C Preferred Stock 8,543,692 8,543,692 46,244 46,244 46,244 3,992,463 Series C-1 19,444,453 19,444,453 111,892 111,892 111,892 9,086,388 53,644,314 53,644,314 $ 232,229 $ 232,229 $ 232,229 25,067,977 As of December 31, 2019 Shares Authorized Preferred Stock Issued and Outstanding Carrying Value Liquidation Preference Redemption Value Common Stock Issuable Upon Conversion Series A Preferred Stock 8,075,799 8,075,799 $ 9,932 $ 9,932 $ 9,932 3,773,820 Series B Preferred Stock 14,913,704 14,913,704 49,969 49,969 49,969 6,969,173 Series B-1 2,666,666 2,666,666 10,431 10,431 10,431 1,246,133 Series C Preferred Stock 11,067,963 9,805,827 50,789 50,789 50,789 4,582,257 36,724,132 35,461,996 $ 121,121 $ 121,121 $ 121,121 16,571,383 Common stock issuable upon conversion in the tables above represents shares of common stock issuable upon an automatic conversion in the event of a qualified public offering, pursuant to the Company’s Amended and Restated Certificate of Incorporation. As of September 30, 2020, the applicable conversion price for the Series A Preferred Stock, Series B Preferred Stock, Series B-1 C-1 The Company’s cumulative dividends on its Preferred Stock were as follows (in thousands): As of September 30, As of December 31, Series A Preferred Stock $ 2,340 $ 1,857 Series B Preferred Stock 7,907 5,228 Series B-1 1,029 431 Series C Preferred Stock 2,244 289 Series C-1 1,642 — $ 15,162 $ 7,805

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2020
Stockholders' Equity Note [Abstract]
Common Stock	7. Common Stock As of September 30, 2020 and December 31, 2019, the authorized capital stock of the Company included 70,500,000 and 46,000,000 shares of common stock, $0.0001 par value, respectively. Shares Reserved for Future Issuance The Company has reserved the following shares of common stock for future issuance: September 30, December 31, Series A Preferred Stock 3,773,820 3,773,820 Series B Preferred Stock 6,969,173 6,969,173 Series B-1 1,246,133 1,246,133 Series C Preferred Stock 3,992,463 4,582,257 Series C-1 9,086,388 — Shares reserved for vesting of restricted common stock 8,763 48,190 Shares reserved for exercise of outstanding stock options 5,814,944 1,634,686 Shares reserved for future awards under the 2017 Stock Incentive Plan 6,051 617,101 Total shares of authorized common stock reserved for future issuance 30,897,735 18,871,360

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation 2017 Stock Incentive Plan The total number of shares of common stock authorized for issuance under the 2017 Stock Incentive Plan (“the 2017 Plan”) as of September 30, 2020 and December 31, 2019 was 5,937,763 shares and 2,356,927 shares, respectively. As of September 30, 2020, the Company did not hold any treasury shares. Restricted Common Stock The following table summarizes all of the Company’s restricted common stock activity: Shares Weighted Unvested as of December 31, 2019 48,190 $ 0.06 Issued — — Vested (39,427 ) 0.05 Repurchased — — Unvested as of September 30, 2020 8,763 $ 0.08 The total fair value of restricted common stock that vested during the three months ended September 30, 2020 and 2019 was $0.1 million and $0.2 million, respectively. The total fair value of restricted common stock that vested during the nine months ended September 30, 2020 and 2019 was $0.2 million and $0.5 million, respectively. Stock Options The following table summarizes the Company’s stock option activity: Number of Weighted Weighted Aggregate (In years) (In thousands) Outstanding as of December 31, 2019 1,634,686 $ 2.46 Granted 4,295,618 7.54 Exercised (11,628 ) 2.32 $ 40 Cancelled or Forfeited (103,732 ) 3.26 Outstanding as of September 30, 2020 5,814,944 $ 6.20 9.41 $ 15,761 Exercisable as of September 30, 2020 959,256 $ 2.29 8.10 $ 6,350 Vested and expected to vest as of September 30, 2020 5,814,944 $ 6.20 9.41 $ 15,761 The aggregate intrinsic value of stock options outstanding, exercisable, and vested and expected to vest is calculated as the difference between the exercise price of the underlying stock options and the estimated fair value of the Company’s common stock for those stock options that had exercise prices lower than the estimated fair value of the Company’s common stock at September 30, 2020. The aggregate intrinsic value of stock options exercised is calculated as the difference between the exercise price of the underlying stock options and the estimated fair value of the Company’s common stock on the date of exercise for those stock options that had exercise prices lower than the estimated fair value of the Company’s common stock on the exercise date. Stock Option Valuation The assumptions that the Company used in the Black-Scholes option pricing model to determine the grant-date fair value of stock options granted to employees, members of the board of directors and non-employees Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Risk-free interest rate 0.37 – 0.68 % 1.55 % 0.37 – 0.91 % 1.55 % Expected term (in years) 6.00 – 10.00 6.00 6.00 – 10.00 6.00 Expected volatility 85.74 – 87.30 % 79.09 % 85.74 – 88.11 % 79.09 % Expected dividend yield 0.00 % 0.00 % 0.00 % 0.00 % Fair value per share of common stock $ 8.27 – 8.91 $ 3.30 $ 5.59 – 8.91 $ 3.30 The weighted-average grant-date fair value of the Company’s stock options granted during the three months ended September 30, 2020 and 2019 was $6.30 per share and $2.25 per share, respectively. The weighted-average grant-date fair value of the Company’s stock options granted during the nine months ended September 30, 2020 and 2019 was $5.41 per share and $2.25 per share, respectively. Stock-Based Compensation Stock-based compensation expense was allocated as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 384 $ 175 $ 639 $ 316 General and administrative 569 101 746 194 Total stock-based compensation expense $ 953 $ 276 $ 1,385 $ 510 As of September 30, 2020, total unrecognized compensation cost related to unvested stock-based awards was $23.3 million, which is expected to be recognized over a weighted-average period of 3.74 years.

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	9. Net Loss per Share Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Numerator: Net loss $ (16,216 ) $ (10,606 ) $ (36,114 ) $ (28,124 ) Accretion and cumulative dividends on redeemable convertible preferred stock (3,943 ) (1,267 ) (8,046 ) (3,450 ) Gain on repurchase of redeemable convertible preferred stock — — 493 — Net loss attributable to common stockholders $ (20,159 ) $ (11,873 ) $ (43,667 ) $ (31,574 ) Denominator: Weighted average common shares outstanding, basic and diluted 1,665,902 1,559,800 1,645,982 1,501,908 Net loss per share attributable to common stockholders, basic and diluted $ (12.10 ) $ (7.61 ) $ (26.53 ) $ (21.02 ) The following potential shares of common stock, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have been anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Series A Preferred Stock 3,773,820 3,773,820 3,773,820 3,773,820 Series B Preferred Stock 6,969,173 6,969,173 6,969,173 6,969,173 Series B-1 1,246,133 1,246,133 1,246,133 1,246,133 Series C Preferred Stock 3,992,463 — 3,992,463 — Series C-1 9,086,388 — 9,086,388 — Outstanding stock options 5,814,944 1,634,686 5,814,944 1,634,686 Unvested restricted common stock 8,763 86,160 8,763 86,160 30,891,684 13,709,972 30,891,684 13,709,972 The shares of common stock issuable upon conversion of the Preferred Stock assume automatic conversion in the event of a qualified public offering.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2020
Related Party Transactions [Abstract]
Related Party Transactions	10. Related Party Transactions On September 11, 2019, the Company entered into a Cooperation and License Agreement (the “License Agreement”) with RogCon Inc. (“RogCon”). Under the License Agreement, RogCon granted to the Company an exclusive, worldwide license under RogCon’s intellectual property to research, develop and commercialize products for the treatment of all forms of epilepsy and/or neurodevelopmental disorders in each case caused by any mutation of the SCN2A gene. Pursuant to the terms of the License Agreement, the Company will conduct, at its own cost and expense, the research and development activities assigned to it under the associated research plan. In addition, the Company is responsible for reimbursing RogCon for any costs associated with research and development activities RogCon performs at the request of the Company. One of the founders of RogCon became the Company’s General Counsel in June 2020. The Company continues to reimburse RogCon for its out-of-pocket out-of-pocket out-of-pocket

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	11. Subsequent Events The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the condensed consolidated financial statements to provide additional evidence for certain estimates or to identify matters that require additional disclosure. In addition to those subsequent events disclosed previously, the Company has identified the following subsequent events: 2020 Stock Option and Incentive Plan and 2020 Employee Stock Purchase Plan The Company’s 2020 Stock Option and Incentive Plan (the “2020 Plan”) and 2020 Employee Stock Purchase Plan (the “2020 ESPP”) were adopted by the board of directors on September 9, 2020 and approved by the Company’s stockholders on October 8, 2020. Both the 2020 Plan and the 2020 ESPP became effective upon the date immediately preceding the date on which the Company’s registration statement filed with the SEC pursuant to Rule 424(b)(4) was declared effective by the SEC, which was October 15, 2020. The 2020 Plan replaced the 2017 Plan. However, the 2017 Plan will continue to govern outstanding equity awards granted thereunder. Under the 2020 Plan, the Company may make equity-based and cash-based incentive awards to its officers, employees, directors and consultants. The Company has initially reserved 3,271,028 shares and 327,102 shares of common stock for issuance under the 2020 Plan and the 2020 ESPP, respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and ASUs of the FASB. The Company’s significant accounting policies are disclosed in the audited consolidated financial statements included in the Company’s final prospectus filed with the Securities and Exchange Commission (“SEC”) pursuant to Rule 424(b)(4) on October 16, 2020. Since the date of those audited consolidated financial statements, there have been no changes to the Company’s significant accounting policies except as noted below.
Unaudited Interim Condensed Consolidated Financial Information	Unaudited Interim Condensed Consolidated Financial Information The accompanying condensed consolidated balance sheet as of September 30, 2020, the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019, the condensed consolidated statements of cash flows for the nine months ended September 30, 2020 and 2019 and the condensed consolidated statements of redeemable convertible preferred stock and stockholders’ deficit for the three and nine months ended September 30, 2020 and 2019 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual consolidated financial statements, and in the opinion of management reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the Company’s financial position as of September 30, 2020, the results of its operations for the three and nine months ended September 30, 2020 and 2019 and its cash flows for the nine months ended September 30, 2020 and 2019. Financial statement disclosures for the three and nine months ended September 30, 2020 and 2019 are condensed and do not include all disclosures required for an annual set of financial statements in accordance with GAAP. The results for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ended December 31, 2020, any other interim periods, or any future year or period.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, the accrual for research and development expenses, stock-based compensation expense, and the valuation of equity awards . Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ materially from those estimates.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The following table reconciles cash, cash equivalents and restricted cash to the total amounts on the condensed consolidated statements of cash flows (in thousands): September 30, 2020 2019 Cash and cash equivalents $ 114,772 $ 4,320 Restricted cash 600 600 Total cash, cash equivalents and restricted cash as shown in the condensed consolidated statement of cash flows $ 115,372 $ 4,920
Deferred Offering Costs	Deferred Offering Costs The Company capitalizes certain legal, accounting and other third-party fees that are directly associated with in-process equity additional paid-in capital
Stock-Based Compensation	Stock-Based Compensation The Company utilizes significant estimates and assumptions in determining the fair value of its equity and equity-based awards. Beginning in the nine months ended September 30, 2020, the Company determined the fair value of shares of its common stock underlying stock-based awards granted using a hybrid probability-weighted expected return method (“PWERM”). The fair value of the Company’s common stock was calibrated to contemporaneous transactions in the Series C Preferred Stock and Series C-1 Other than as noted herein, there were no other changes to the Company’s stock-based compensation policy since the date of the audited consolidated financial statements included in the Company’s final prospectus filed pursuant to Rule 424(b)(4) on October 16, 2020.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ deficit that are excluded from net loss. The Company’s comprehensive loss was equal to net loss for the three and nine months ended September 30, 2020 and 2019.
Net Loss per Share	Net Loss per Share The Company follows the two-class two-class two-class two-class Net loss attributable to common stockholders is equal to the net loss for the period, as adjusted for: (i) cumulative dividends accrued for redeemable convertible preferred stock, whether or not declared, (ii) increases in carrying value recorded for redeemable convertible preferred stock, including accretion on redeemable convertible preferred stock to redemption value for amounts other than cumulative dividends and (iii) gains on the redemptions of redeemable convertible preferred stock. Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, which excludes shares of restricted common stock that are not vested. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, after giving consideration to the dilutive effect of potentially dilutive common shares. For purposes of this calculation, outstanding options to purchase shares of common stock, unvested shares of restricted common stock and shares of redeemable convertible preferred stock are considered potentially dilutive common shares. The Company has generated a net loss in all periods presented so the basic and diluted net loss per share attributable to common stockholders are the same as the inclusion of the potentially dilutive securities would be anti-dilutive.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Summary of cash, cash equivalents and restricted cash	The following table reconciles cash, cash equivalents and restricted cash to the total amounts on the condensed consolidated statements of cash flows (in thousands): September 30, 2020 2019 Cash and cash equivalents $ 114,772 $ 4,320 Restricted cash 600 600 Total cash, cash equivalents and restricted cash as shown in the condensed consolidated statement of cash flows $ 115,372 $ 4,920

Fair Value of Financial Assets

Fair Value of Financial Assets (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Summary of financial assets measured at fair value on a recurring basis	The following tables present information about the Company’s financial assets measured at fair value on a recurring ba s hierarchy As of September 30, 2020 Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 114,386 $ — $ — $ 114,386 $ 114,386 $ — $ — $ 114,386 As of December 31, 2019 Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 44,429 $ — $ — $ 44,429 $ 44,429 $ — $ — $ 44,429

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2020
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities [Table Text Block]	Accrued expenses consisted of the following (in thousands): September 30, 2020 December 31, 2019 Accrued external research and development expenses $ 3,370 $ 1,552 Accrued personnel-related expenses 1,606 1,059 Accrued license fees — 363 Accrued professional services 1,135 110 Accrued other 75 371 Total accrued expenses $ 6,186 $ 3,455

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2020
Temporary Equity [Abstract]
Summary Of preferred stock	The Preferred Stock consisted of the following (in thousands, except share amounts): As of September 30, 2020 Shares Authorized Preferred Stock Issued and Outstanding Carrying Value Liquidation Preference Redemption Value Common Stock Issuable Upon Conversion Series A Preferred Stock 8,075,799 8,075,799 $ 10,416 $ 10,416 $ 10,416 3,773,820 Series B Preferred Stock 14,913,704 14,913,704 52,648 52,648 52,648 6,969,173 Series B-1 2,666,666 2,666,666 11,029 11,029 11,029 1,246,133 Series C Preferred Stock 8,543,692 8,543,692 46,244 46,244 46,244 3,992,463 Series C-1 19,444,453 19,444,453 111,892 111,892 111,892 9,086,388 53,644,314 53,644,314 $ 232,229 $ 232,229 $ 232,229 25,067,977 As of December 31, 2019 Shares Authorized Preferred Stock Issued and Outstanding Carrying Value Liquidation Preference Redemption Value Common Stock Issuable Upon Conversion Series A Preferred Stock 8,075,799 8,075,799 $ 9,932 $ 9,932 $ 9,932 3,773,820 Series B Preferred Stock 14,913,704 14,913,704 49,969 49,969 49,969 6,969,173 Series B-1 2,666,666 2,666,666 10,431 10,431 10,431 1,246,133 Series C Preferred Stock 11,067,963 9,805,827 50,789 50,789 50,789 4,582,257 36,724,132 35,461,996 $ 121,121 $ 121,121 $ 121,121 16,571,383
Schedule of cumulative dividends on Preferred Stock	The Company’s cumulative dividends on its Preferred Stock were as follows (in thousands): As of September 30, As of December 31, Series A Preferred Stock $ 2,340 $ 1,857 Series B Preferred Stock 7,907 5,228 Series B-1 1,029 431 Series C Preferred Stock 2,244 289 Series C-1 1,642 — $ 15,162 $ 7,805

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2020
Stockholders' Equity Note [Abstract]
Summary of common stock reserved for future issuance	The Company has reserved the following shares of common stock for future issuance: September 30, December 31, Series A Preferred Stock 3,773,820 3,773,820 Series B Preferred Stock 6,969,173 6,969,173 Series B-1 1,246,133 1,246,133 Series C Preferred Stock 3,992,463 4,582,257 Series C-1 9,086,388 — Shares reserved for vesting of restricted common stock 8,763 48,190 Shares reserved for exercise of outstanding stock options 5,814,944 1,634,686 Shares reserved for future awards under the 2017 Stock Incentive Plan 6,051 617,101 Total shares of authorized common stock reserved for future issuance 30,897,735 18,871,360

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of stock option activity	The following table summarizes the Company’s stock option activity: Number of Weighted Weighted Aggregate (In years) (In thousands) Outstanding as of December 31, 2019 1,634,686 $ 2.46 Granted 4,295,618 7.54 Exercised (11,628 ) 2.32 $ 40 Cancelled or Forfeited (103,732 ) 3.26 Outstanding as of September 30, 2020 5,814,944 $ 6.20 9.41 $ 15,761 Exercisable as of September 30, 2020 959,256 $ 2.29 8.10 $ 6,350 Vested and expected to vest as of September 30, 2020 5,814,944 $ 6.20 9.41 $ 15,761
Schedule of fair value of stock option awards on the grant date using the Black-Scholes option valuation model	The assumptions that the Company used in the Black-Scholes option pricing model to determine the grant-date fair value of stock options granted to employees, members of the board of directors and non-employees Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Risk-free interest rate 0.37 – 0.68 % 1.55 % 0.37 – 0.91 % 1.55 % Expected term (in years) 6.00 – 10.00 6.00 6.00 – 10.00 6.00 Expected volatility 85.74 – 87.30 % 79.09 % 85.74 – 88.11 % 79.09 % Expected dividend yield 0.00 % 0.00 % 0.00 % 0.00 % Fair value per share of common stock $ 8.27 – 8.91 $ 3.30 $ 5.59 – 8.91 $ 3.30
Summary of stock-based compensation expense	Stock-based compensation expense was allocated as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 384 $ 175 $ 639 $ 316 General and administrative 569 101 746 194 Total stock-based compensation expense $ 953 $ 276 $ 1,385 $ 510
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of restricted stock activity	The following table summarizes all of the Company’s restricted common stock activity: Shares Weighted Unvested as of December 31, 2019 48,190 $ 0.06 Issued — — Vested (39,427 ) 0.05 Repurchased — — Unvested as of September 30, 2020 8,763 $ 0.08

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Summary of basic and diluted net loss per share attributable to common stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Numerator: Net loss $ (16,216 ) $ (10,606 ) $ (36,114 ) $ (28,124 ) Accretion and cumulative dividends on redeemable convertible preferred stock (3,943 ) (1,267 ) (8,046 ) (3,450 ) Gain on repurchase of redeemable convertible preferred stock — — 493 — Net loss attributable to common stockholders $ (20,159 ) $ (11,873 ) $ (43,667 ) $ (31,574 ) Denominator: Weighted average common shares outstanding, basic and diluted 1,665,902 1,559,800 1,645,982 1,501,908 Net loss per share attributable to common stockholders, basic and diluted $ (12.10 ) $ (7.61 ) $ (26.53 ) $ (21.02 )
Summary of antidilutive securities excluded from computation of earnings per share	The following potential shares of common stock, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have been anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Series A Preferred Stock 3,773,820 3,773,820 3,773,820 3,773,820 Series B Preferred Stock 6,969,173 6,969,173 6,969,173 6,969,173 Series B-1 1,246,133 1,246,133 1,246,133 1,246,133 Series C Preferred Stock 3,992,463 — 3,992,463 — Series C-1 9,086,388 — 9,086,388 — Outstanding stock options 5,814,944 1,634,686 5,814,944 1,634,686 Unvested restricted common stock 8,763 86,160 8,763 86,160 30,891,684 13,709,972 30,891,684 13,709,972

Nature of the Business - Additi

Nature of the Business - Additional Information (Details) $ / shares in Units, $ in Thousands	Oct. 20, 2020USD ($)$ / sharesshares	Oct. 08, 2020	Sep. 30, 2020USD ($)ProgramsProduct$ / sharesshares	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)ProgramsProduct$ / sharesshares	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)ProgramsProduct$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Number of Programs | Programs			5		5		5
Number of product candidates | Product			3		3		3
Proceeds From Issuance Of Redeemable Convertible Preferred Stock | $					$ 133,442	$ 9,939	$ 210,700
Convertible Preferred Stock Shares Issued Upon Conversion | shares			25,067,977		25,067,977		25,067,977	16,571,383
Common Stock, Shares Authorized | shares			70,500,000		70,500,000		70,500,000	46,000,000
Common Stock, Par Value Per Share | $ / shares			$ 0.0001		$ 0.0001		$ 0.0001	$ 0.0001
Net loss and comprehensive loss | $			$ (16,216)	$ (10,606)	$ (36,114)	(28,124)
Accumulated deficit | $			(123,264)		(123,264)		$ (123,264)	$ (81,009)
Cash and cash equivalents | $			114,772	$ 4,320	114,772	$ 4,320	114,772	$ 44,815
IPO [Member]
Cash and cash equivalents | $			$ 114,800		$ 114,800		$ 114,800
Subsequent Event [Member]
Reverse Stock Split Description		one-for-2.14
Common Stock, Shares Authorized | shares	150,000,000
Preferred Stock, Shares Authorized | shares	10,000,000
Common Stock, Par Value Per Share | $ / shares	$ 0.0001
Preferred Stock, Par Value Per Share | $ / shares	$ 0.0001
Subsequent Event [Member] | Common Stock [Member]
Proceeds From Issuance Initial Public Offering Gross | $	$ 218,500
Proceeds From Issuance Initial Public Offering | $	$ 199,900
Convertible Preferred Stock Shares Issued Upon Conversion | shares	25,067,977
Subsequent Event [Member] | IPO [Member] | Common Stock [Member]
Stock Issued During Period, Shares, New Issues | shares	11,500,000
Share Price | $ / shares	$ 19
Subsequent Event [Member] | Over-Allotment Option [Member] | Common Stock [Member]
Stock Issued During Period, Shares, New Issues | shares	1,500,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Other Assets [Member]
Deferred Offering Costs	$ 2	$ 0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 114,772	$ 44,815	$ 4,320
Restricted cash	600	600	600
Total cash, cash equivalents and restricted cash as shown in the condensed consolidated statement of cash flows	$ 115,372	$ 45,415	$ 4,920	$ 18,550

Fair Value of Financial Asset_2

Fair Value of Financial Assets - Summary of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 114,386	$ 44,429
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	114,386	44,429
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	114,386	44,429
Money Market Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	114,386	44,429
Money Market Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure
Money Market Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure

Accrued Expenses - Summary of A

Accrued Expenses - Summary of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued external research and development expenses	$ 3,370	$ 1,552
Accrued personnel-related expenses	1,606	1,059
Accrued license fees		363
Accrued professional services	1,135	110
Accrued other	75	371
Total accrued expenses	$ 6,186	$ 3,455

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - Office Space in Cambridge Massachusetts [Member]	9 Months Ended
	Sep. 30, 2020
Loss Contingencies [Line Items]
Lease Expiration Date	Dec. 30, 2021
Percentage Increase In Annual Base Rent	1.00%

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 24, 2020	May 08, 2020	Apr. 15, 2020	Jan. 20, 2020	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Shares Authorized					53,644,314	53,644,314		36,724,132
Repurchase of Series C redeemable convertible preferred stock						$ 493
Payments Of Stock Issuance Costs						1,117
Accumulated Deficit [Member]
Class of Stock [Line Items]
Repurchase of Series C redeemable convertible preferred stock						$ 493
Series A Preferred Stock
Class of Stock [Line Items]
Shares Authorized					8,075,799	8,075,799		8,075,799
Preferred stock applicable conversion price						2.14
Series B Preferred Stock
Class of Stock [Line Items]
Shares Authorized					14,913,704	14,913,704		14,913,704
Preferred stock applicable conversion price						6.42
Series B-1 Preferred Stock
Class of Stock [Line Items]
Shares Authorized					2,666,666	2,666,666		2,666,666
Preferred stock applicable conversion price						8.03
Issuance of preferred stock, shares							2,666,666
Issuance of preferred stock							$ 9,939
Payments Of Stock Issuance Costs							$ 61
Series C Preferred Stock
Class of Stock [Line Items]
Shares Authorized					8,543,692	8,543,692		11,067,963
Repurchase of shares				5,825,243
Stock retired upon repurchase				5,825,243
Preferred stock applicable conversion price						11.02
Issuance of preferred stock, shares		4,563,108	4,563,108			4,563,108
Issuance of preferred stock		$ 23,500	$ 23,500			$ 23,459
Temporary Equity Value Acquired				$ 30,000		$ (30,493)
Share Price		$ 5.15	$ 5.15	$ 5.15
Temporary Equity Shares Acquired				5,825,243		(5,825,243)
Payments Of Stock Issuance Costs						$ 41
Series C Preferred Stock | Accumulated Deficit [Member]
Class of Stock [Line Items]
Repurchase of Series C redeemable convertible preferred stock						$ 500
Series C-1 Preferred Stock
Class of Stock [Line Items]
Shares Authorized	19,444,453				19,444,453	19,444,453		0
Preferred stock applicable conversion price						12.13
Issuance of preferred stock, shares	19,444,453				19,444,453	19,444,453
Issuance of preferred stock	$ 110,300				$ 110,096	$ 110,096
Share Price	$ 5.67
Payments Of Stock Issuance Costs					$ 154	$ 154
Per Share Amounts Of Preferred Dividends In Arrears	$ 0.4536

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock - Summary of Preferred Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jul. 24, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
Shares Authorized	53,644,314			36,724,132
Preferred Stock Issued	53,644,314			35,461,996
Preferred Stock outstanding	53,644,314			35,461,996
Carrying Value	$ 232,229			$ 121,121
Liquidation Preference	232,229			121,121
Redemption Value	$ 232,229			$ 121,121
Common Stock Issuable Upon Conversion	25,067,977			16,571,383
Series A Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	8,075,799			8,075,799
Preferred Stock Issued	8,075,799			8,075,799
Preferred Stock outstanding	8,075,799		8,075,799	8,075,799	8,075,799	8,075,799	8,075,799
Carrying Value	$ 10,416			$ 9,932
Liquidation Preference	10,416			9,932
Redemption Value	$ 10,416			$ 9,932
Common Stock Issuable Upon Conversion	3,773,820			3,773,820
Series B Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	14,913,704			14,913,704
Preferred Stock Issued	14,913,704			14,913,704
Preferred Stock outstanding	14,913,704		14,913,704	14,913,704	14,913,704	14,913,704	14,913,704
Carrying Value	$ 52,648			$ 49,969
Liquidation Preference	52,648			49,969
Redemption Value	$ 52,648			$ 49,969
Common Stock Issuable Upon Conversion	6,969,173			6,969,173
Series B-1 Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	2,666,666			2,666,666
Preferred Stock Issued	2,666,666			2,666,666
Preferred Stock outstanding	2,666,666		2,666,666	2,666,666	2,666,666	2,666,666
Carrying Value	$ 11,029			$ 10,431
Liquidation Preference	11,029			10,431
Redemption Value	$ 11,029			$ 10,431
Common Stock Issuable Upon Conversion	1,246,133			1,246,133
Series C Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	8,543,692			11,067,963
Preferred Stock Issued	8,543,692			9,805,827
Preferred Stock outstanding	8,543,692		8,543,692	9,805,827
Carrying Value	$ 46,244			$ 50,789
Liquidation Preference	46,244			50,789
Redemption Value	$ 46,244			$ 50,789
Common Stock Issuable Upon Conversion	3,992,463			4,582,257
Series C-1 Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	19,444,453	19,444,453		0
Preferred Stock Issued	19,444,453			0
Preferred Stock outstanding	19,444,453			0
Carrying Value	$ 111,892
Liquidation Preference	111,892			$ 0
Redemption Value	$ 111,892
Common Stock Issuable Upon Conversion	9,086,388

Redeemable Convertible Prefer_5

Redeemable Convertible Preferred Stock - Summary of Cumulative Dividends on Preferred Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Dividends preferred stock	$ 15,162	$ 7,805
Series A Preferred Stock
Class of Stock [Line Items]
Dividends preferred stock	2,340	1,857
Series B Preferred Stock
Class of Stock [Line Items]
Dividends preferred stock	7,907	5,228
Series B-1 Preferred Stock
Class of Stock [Line Items]
Dividends preferred stock	1,029	431
Series C Preferred Stock
Class of Stock [Line Items]
Dividends preferred stock	2,244	289
Series C-1 Preferred Stock
Class of Stock [Line Items]
Dividends preferred stock	$ 1,642	$ 0

Common Stock - Summary of Commo

Common Stock - Summary of Common Stock Reserved For Future Issuance (Details) - shares	Sep. 30, 2020	Dec. 31, 2019
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	30,897,735	18,871,360
Share-based Payment Arrangement [Member] | 2017 Stock Incentive Plan [Member]
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	6,051	617,101
Restricted Stock [Member]
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	8,763	48,190
Share-based Payment Arrangement, Option [Member]
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	5,814,944	1,634,686
Series A redeemable convertible preferred stock [Member]
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	3,773,820	3,773,820
Series B redeemable convertible preferred stock [Member]
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	6,969,173	6,969,173
Series B-1 redeemable convertible preferred stock [Member]
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	1,246,133	1,246,133
Series C redeemable convertible preferred stock [Member]
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	3,992,463	4,582,257
Series C-1 redeemable convertible preferred stock [Member]
Schedule Of Common Stock Reserved For Future Issuance [Line Items]
Common stock for future issuances	9,086,388

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value of stock options granted, Per share	$ 6.30	$ 2.25	$ 5.41	$ 2.25
Unrecognized compensation expense related to unvested stock based awards	$ 23.3		$ 23.3
Unrecognized compensation expense expected to be recognised			3 years 8 months 26 days
2017 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares authorized	5,937,763		5,937,763		2,356,927
Treasury shares	0		0
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of restricted common stock that vested	$ 0.1	$ 0.2	$ 0.2	$ 0.5

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Stock [Member]	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares beginning balance | shares	48,190
Shares vested | shares	(39,427)
Shares ending balance | shares	8,763
Weighted average grant date fair value beginning balance | $ / shares	$ 0.06
Weighted average grant date fair value vested | $ / shares	0.05
Weighted average grant date fair value ending balance | $ / shares	$ 0.08

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding beginning balance	1,634,686
Number of shares granted	4,295,618
Number of shares exercised	(11,628)
Number of shares canceled or forfeited	(103,732)
Number of shares outstanding ending balance	5,814,944
Number of shares exercisable	959,256
Number of shares vested and expected to vest	5,814,944
Weighted average exercise price beginning balance	$ 2.46
Weighted average exercise price granted	7.54
Weighted average exercise price exercised	2.32
Weighted average exercise price cancelled or forfeited	3.26
Weighted average exercise price ending balance	6.20
Weighted average exercise price exercisable	2.29
Weighted average exercise price vested and expected to vest	$ 6.20
Weighted average remaining contractual term outstanding	9 years 4 months 27 days
Weighted average remaining contractual term exercisable	8 years 1 month 6 days
Weighted average remaining contractual term vested and expected to vest	9 years 4 months 27 days
Aggregate intrinsic value exercised	$ 40
Aggregate intrinsic value outstanding	15,761
Aggregate intrinsic value exercisable	6,350
Aggregate intrinsic value vested and expected to vest	$ 15,761

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Fair Value of Stock Option Awards on the Grant Date Using the Black-Scholes Option Valuation Model (Details) - $ / shares	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]
Risk-free interest rate		1.55%		1.55%
Risk-free interest rate minimum	0.37%		0.37%
Risk-free interest rate maximum	0.68%		0.91%
Expected term (in years)		6 years		6 years
Expected volatility		79.09%		79.09%
Expected volatility minimum	85.74%		85.74%
Expected volatility maximum	87.30%		88.11%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Fair value per share of common stock		$ 3.30		$ 3.30
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years		6 years
Fair value per share of common stock	$ 8.27		$ 5.59
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	10 years		10 years
Fair value per share of common stock	$ 8.91		$ 8.91

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 953	$ 276	$ 1,385	$ 510
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	384	175	639	316
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 569	$ 101	$ 746	$ 194

Net Loss per Share - Summary of

Net Loss per Share - Summary of basic and diluted net loss per share attributable to common stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss	$ (16,216)	$ (10,606)	$ (36,114)	$ (28,124)
Accretion and cumulative dividends on redeemable convertible preferred stock	(3,943)	(1,267)	(8,046)	(3,450)
Gain on repurchase of redeemable convertible preferred stock			493
Net loss attributable to common stockholders	$ (20,159)	$ (11,873)	$ (43,667)	$ (31,574)
Denominator:
Weighted average common shares outstanding, basic and diluted	1,665,902	1,559,800	1,645,982	1,501,908
Net loss per share attributable to common stockholders, basic and diluted	$ (12.10)	$ (7.61)	$ (26.53)	$ (21.02)

Net Loss per Share - Summary _2

Net Loss per Share - Summary of antidilutive securities excluded from computation of earnings per share (Details) - 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]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	30,891,684	13,709,972	30,891,684	13,709,972
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	5,814,944	1,634,686	5,814,944	1,634,686
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	8,763	86,160	8,763	86,160
Series A Preferred Stock | Convertible Preferred Stocks [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	3,773,820	3,773,820	3,773,820	3,773,820
Series B Preferred Stock | Convertible Preferred Stocks [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	6,969,173	6,969,173	6,969,173	6,969,173
Series C Preferred Stock | Convertible Preferred Stocks [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	3,992,463		3,992,463
Series B-1 Preferred Stock | Convertible Preferred Stocks [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,246,133	1,246,133	1,246,133	1,246,133
Series C-1 Preferred Stock | Convertible Preferred Stocks [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	9,086,388		9,086,388

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - RogCon [Member] $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)
Related Party Transaction [Line Items]
Due To Affiliate Current	$ 0.3	$ 0.3
Reimbursement of Research And Development Expense [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 0.1	$ 0.1

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - shares	Oct. 08, 2020	Sep. 30, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Common Stock Shares Reserved Under Plan		30,897,735	18,871,360
Subsequent Event [Member] | 2020 Stock Option and Incentive Plan [Member]
Subsequent Event [Line Items]
Common Stock Shares Reserved Under Plan	3,271,028
Subsequent Event [Member] | 2020 Employee Stock Purchase Plan [Member]
Subsequent Event [Line Items]
Common Stock Shares Reserved Under Plan	327,102