STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in	Accumulated Deficit	Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, beginning balance (in shares) at Dec. 31, 2017						9,131,999
Redeemable convertible preferred stock, beginning balance at Dec. 31, 2017						$ 89,634
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of redeemable preferred stock (in shares)						1,842,959
Issuance of redeemable preferred stock						$ 14,890
Issuance of redeemable preferred stock upon conversion of promissory notes (in shares)						2,080,209
Issuance of redeemable preferred stock upon conversion of promissory notes						$ 19,778
Exercises of warrants (in shares)						144,948
Exercises of warrants for preferred stock						$ 1,212
Accretion of redeemable preferred stock to redemption value						$ 95
Conversion of redeemable convertible preferred stock into common stock (in shares)						(13,200,115)
Conversion of redeemable convertible preferred stock into common stock						$ (125,609)
Redeemable convertible preferred stock, ending balance (in shares) at Dec. 31, 2018						0
Redeemable convertible preferred stock, ending balance at Dec. 31, 2018						$ 0
Beginning balance (in shares) at Dec. 31, 2017		775,755	(29,967)
Beginning balance at Dec. 31, 2017	$ (97,416)	$ 1	$ (24)	$ 1,672	$ (99,065)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of redeemable preferred stock to redemption value	(95)			(95)
Conversion of redeemable convertible preferred stock warrants into common stock warrants	3,346			3,346
Conversion of redeemable convertible preferred stock into common stock (in shares)		13,225,048
Conversion of redeemable convertible preferred stock into common stock	125,609	$ 13		125,596
Issuance of common stock in initial public offering, net (in shares)		9,864,666
Issuance of common stock in initial public offering, net	42,974	$ 10		42,964
Exercises of warrants for common stock, net (in shares)		619,086
Exercises of warrants for common stock, net	(69)	$ 1		(70)
Exercises of stock options (in shares)		43,687
Exercises of stock options	92			92
Stock-based compensation	332			332
Net loss	$ (23,846)				(23,846)
Ending balance (in shares) at Dec. 31, 2018	24,498,275	24,528,242	(29,967)
Ending balance at Dec. 31, 2018	$ 50,927	$ 25	$ (24)	173,837	(122,911)
Redeemable convertible preferred stock, ending balance (in shares) at Dec. 31, 2019						0
Redeemable convertible preferred stock, ending balance at Dec. 31, 2019						$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of redeemable convertible preferred stock warrants into common stock warrants	0
Issuance of common stock in initial public offering, net (in shares)		4,124,475
Issuance of common stock in initial public offering, net	46,277	$ 4		46,273
Exercises of stock options (in shares)		143,654
Exercises of stock options	245			245
Stock-based compensation	1,421			1,421
Net loss	(39,247)				(39,247)
Issuance of common stock warrants	$ 355			355
Ending balance (in shares) at Dec. 31, 2019	28,766,404	28,796,371	(29,967)
Ending balance at Dec. 31, 2019	$ 59,978	$ 29	$ (24)	$ 222,131	$ (162,158)