Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Convertible preferred stock (as converted)	Total
Balances at beginning at Dec. 31, 2017					$ 89,362
Balances at beginning (in shares) at Dec. 31, 2017					8,306,934
Balances at beginning at Dec. 31, 2017		$ 2,130	$ (14)	$ (58,682)		$ (56,566)
Balances at beginning (in shares) at Dec. 31, 2017	2,092,040
Issuance of convertible preferred stock					$ 120,306
Issuance of convertible preferred stock (in shares)					8,941,325
Issuance of common stock upon exercise of options		44				44
Issuance of common stock upon exercise of options (in shares)	27,832
Stock-based compensation		1,419				1,419
Unrealized gain on fair value of investments			26			26
Unrealized currency exchange gain (loss)			(16)			(16)
Net loss				(37,940)		(37,940)
Balances at end at Dec. 31, 2018					$ 209,668
Balances at end (in shares) at Dec. 31, 2018					17,248,259
Balances at end at Dec. 31, 2018		3,593	(4)	(96,622)		(93,033)
Balances at end (in shares) at Dec. 31, 2018	2,119,872
Conversion of convertible preferred stock					$ (209,668)	209,668
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		288				288
Issuance of common stock upon exercise of options (in shares)	77,368
Vesting of early exercised stock options		15				15
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		6,056				6,056
Unrealized gain on fair value of investments			16			16
Unrealized currency exchange gain (loss)			4			4
Net loss				(67,484)		(67,484)
Balances at end at Dec. 31, 2019	$ 3	$ 351,039	$ 16	$ (164,106)		$ 186,952
Balances at end (in shares) at Dec. 31, 2019	27,970,167