STATEMENTS OF STOCKHOLDERS’ (DEFICIT) EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		24,528,242	29,967
Beginning balance at Dec. 31, 2018	$ 50,927	$ 25	$ (24)	$ 173,837	$ (122,911)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock warrants	355			355
Issuance of common stock in initial public offering, net (in shares)		4,124,475
Issuance of common stock in 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)
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock warrants	7,925			7,925
Issuance of common stock in initial public offering, net (in shares)		561,848
Issuance of common stock in public offering, net	2,942			2,942
Issuance of common stock through employee share purchase plan (in shares)		62,063
Issuance of common stock through employee share purchase plan	186			186
Exercises of stock options (in shares)		51,572
Exercises of stock options	95			95
Stock-based compensation	2,237			2,237
Net loss	$ (98,565)				(98,565)
Ending balance (in shares) at Dec. 31, 2020	29,441,887	29,471,854	29,967
Ending balance at Dec. 31, 2020	$ (25,202)	$ 29	$ (24)	$ 235,516	$ (260,723)