Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Balances at beginning at Dec. 31, 2018	$ 209,668
Balances at beginning (in shares) at Dec. 31, 2018	17,248,259
Balances at beginning at Dec. 31, 2018			$ 3,593	$ (4)	$ (96,622)	$ (93,033)
Balances at beginning (in shares) at Dec. 31, 2018		2,119,872
Conversion of convertible preferred stock	$ (209,668)					209,669
Conversion of convertible preferred stock (in shares)	(17,248,259)
Conversion of convertible preferred stock		$ 2	209,666			209,668
Conversion of convertible preferred stock (in shares)		17,248,259
Issuance of common stock upon initial public offering, net		$ 1	130,785			130,786
Issuance of common stock upon initial public offering, net (in shares)		8,452,500
Exercise of warrants (in shares)		62,936
Issuance of common stock upon exercise of options			241			241
Issuance of common stock upon exercise of options (in shares)		67,244
Vesting of early exercised stock options			8			8
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital			503			503
Issuance of common stock under the Employee Stock Purchase Plan			133			133
Issuance of common stock under the Employee Stock Purchase Plan (shares)		9,232
Stock-based compensation			4,013			4,013
Unrealized gain (loss) on fair value of investments				48		48
Unrealized currency exchange loss				(1)		(1)
Net loss					(47,371)	(47,371)
Balances at end at Sep. 30, 2019		$ 3	348,942	43	(143,993)	204,995
Balances at end (in shares) at Sep. 30, 2019		27,960,043
Balances at beginning at Jun. 30, 2019		$ 3	346,915	86	(128,122)	218,882
Balances at beginning (in shares) at Jun. 30, 2019		27,947,201
Issuance of common stock upon exercise of options			10			10
Issuance of common stock upon exercise of options (in shares)		3,610
Vesting of early exercised stock options			6			6
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital			133			133
Issuance of common stock under the Employee Stock Purchase Plan (shares)		9,232
Stock-based compensation			1,878			1,878
Unrealized gain (loss) on fair value of investments				(41)		(41)
Unrealized currency exchange loss				(2)		(2)
Net loss					(15,871)	(15,871)
Balances at end at Sep. 30, 2019		$ 3	348,942	43	(143,993)	204,995
Balances at end (in shares) at Sep. 30, 2019		27,960,043
Balances at beginning at Dec. 31, 2019		$ 3	351,039	16	(164,106)	186,952
Balances at beginning (in shares) at Dec. 31, 2019		27,970,167
Issuance of common stock upon initial public offering, net		$ 1	126,054			126,055
Issuance of common stock upon initial public offering, net (in shares)		8,423,375
Issuance of common stock upon exercise of options			1,131			1,131
Issuance of common stock upon exercise of options (in shares)		223,143
Vesting of early exercised stock options			4			4
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital						500
Issuance of common stock under the Employee Stock Purchase Plan			1,012			1,012
Issuance of common stock under the Employee Stock Purchase Plan (shares)		76,164
Stock-based compensation			9,353			9,353
Unrealized gain (loss) on fair value of investments				101		101
Net loss					(63,328)	(63,328)
Balances at end at Sep. 30, 2020		$ 4	488,593	117	(227,434)	261,280
Balances at end (in shares) at Sep. 30, 2020		36,692,849
Balances at beginning at Jun. 30, 2020		$ 3	358,401	216	(204,505)	154,115
Balances at beginning (in shares) at Jun. 30, 2020		28,192,733
Issuance of common stock upon initial public offering, net		$ 1	126,054			126,055
Issuance of common stock upon initial public offering, net (in shares)		8,423,375
Issuance of common stock upon exercise of options			172			172
Issuance of common stock upon exercise of options (in shares)		37,133
Issuance of common stock under the Employee Stock Purchase Plan			479			479
Issuance of common stock under the Employee Stock Purchase Plan (shares)		39,608
Stock-based compensation			3,487			3,487
Unrealized gain (loss) on fair value of investments				(99)		(99)
Net loss					(22,929)	(22,929)
Balances at end at Sep. 30, 2020		$ 4	$ 488,593	$ 117	$ (227,434)	$ 261,280
Balances at end (in shares) at Sep. 30, 2020		36,692,849