CONDENSED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		28,796,371	29,967
Beginning 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
Exercises of stock options (in shares)		14,236
Exercise of stock options	17			17
Stock-based compensation	471			471
Net loss	(14,905)				(14,905)
Ending balance (in shares) at Mar. 31, 2020		28,810,607	29,967
Ending balance at Mar. 31, 2020	$ 53,486	$ 29	$ (24)	230,544	(177,063)
Beginning balance (in shares) at Dec. 31, 2020	29,441,887	29,471,854	29,967
Beginning balance at Dec. 31, 2020	$ (25,202)	$ 29	$ (24)	235,516	(260,723)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net (in shares)		18,400,000
Issuance of common stock in public offering, net	60,084	$ 19		60,065
Exercises of stock options (in shares)		110,146
Exercise of stock options	217			217
Stock-based compensation	670			670
Net loss	$ (27,358)				(27,358)
Ending balance (in shares) at Mar. 31, 2021	47,952,033	47,982,000	29,967
Ending balance at Mar. 31, 2021	$ 8,411	$ 48	$ (24)	$ 296,468	$ (288,081)