CONDENSED STATEMENTS OF STOCKHOLDERS’ EQUITY (DEFICIT) - 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, 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]
Net loss	(68,190)
Ending balance (in shares) at Sep. 30, 2020		29,389,288	(29,967)
Ending balance at Sep. 30, 2020	4,352	$ 29	$ (24)	234,695	(230,348)
Beginning balance (in shares) at Mar. 31, 2020		28,810,607	(29,967)
Beginning balance at Mar. 31, 2020	53,486	$ 29	$ (24)	230,544	(177,063)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net (in shares)		80,523
Issuance of common stock in public offering, net	473			473
Exercises of stock options (in shares)		404
Exercise of stock options	1			1
Stock-based compensation	575			575
Net loss	(28,142)				(28,142)
Ending balance (in shares) at Jun. 30, 2020		28,891,534	(29,967)
Ending balance at Jun. 30, 2020	26,393	$ 29	$ (24)	231,593	(205,205)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net (in shares)		481,325
Issuance of common stock in public offering, net	2,469			2,469
Exercises of stock options (in shares)		16,429
Exercise of stock options	24			24
Stock-based compensation	609			609
Net loss	(25,143)				(25,143)
Ending balance (in shares) at Sep. 30, 2020		29,389,288	(29,967)
Ending balance at Sep. 30, 2020	$ 4,352	$ 29	$ (24)	234,695	(230,348)
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		47,982,000	(29,967)
Ending balance at Mar. 31, 2021	$ 8,411	$ 48	$ (24)	296,468	(288,081)
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
Net loss	$ (87,961)
Ending balance (in shares) at Sep. 30, 2021	48,062,483	48,092,450	(29,967)
Ending balance at Sep. 30, 2021	$ (50,329)	$ 48	$ (24)	298,331	(348,684)
Beginning balance (in shares) at Mar. 31, 2021		47,982,000	(29,967)
Beginning balance at Mar. 31, 2021	8,411	$ 48	$ (24)	296,468	(288,081)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net	157			157
Exercises of stock options (in shares)		3,615
Exercise of stock options	6			6
Issuance of common stock through employee share purchase plan (in shares)		72,105
Issuance of common stock under employee stock purchase plan	202			202
Stock-based compensation	728			728
Net loss	(28,679)				(28,679)
Ending balance (in shares) at Jun. 30, 2021		48,057,720	(29,967)
Ending balance at Jun. 30, 2021	(19,175)	$ 48	$ (24)	297,561	(316,760)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercises of stock options (in shares)		34,730
Exercise of stock options	50			50
Stock-based compensation	720			720
Net loss	$ (31,924)				(31,924)
Ending balance (in shares) at Sep. 30, 2021	48,062,483	48,092,450	(29,967)
Ending balance at Sep. 30, 2021	$ (50,329)	$ 48	$ (24)	$ 298,331	$ (348,684)