CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	ATM Facility	Common Stock	Common Stock ATM Facility	Additional Paid-in Capital	Additional Paid-in Capital ATM Facility	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2020			140,449,647
Beginning balance at Dec. 31, 2020	$ (9,227)		$ 140		$ 306,554		$ (315,921)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(55,512)						(55,512)
Share-based compensation	958				958
Exercise of stock options (in shares)			30,610
Exercises of stock options	39				39
Exercise of common stock warrants (in shares)			852,840
Exercises of common stock warrants	469		$ 1		468
Issuance of common stock under ATM Offering, net of issuance costs of $2.2 million (in shares)				30,645,702
Issuance of common stock under ATM Offering, net of issuance costs of $2.2 million		$ 72,543		$ 31		$ 72,512
Ending balance (in shares) at Mar. 31, 2021			171,978,799
Ending balance at Mar. 31, 2021	9,270		$ 172		380,531		(371,433)
Beginning balance (in shares) at Dec. 31, 2021			199,463,645
Beginning balance at Dec. 31, 2021	171,710		$ 199		487,768		(316,257)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(807)						(807)
Share-based compensation	$ 1,894				1,894
Exercise of stock options (in shares)	0
Exercise of common stock warrants (in shares)	0
Ending balance (in shares) at Mar. 31, 2022			199,463,645
Ending balance at Mar. 31, 2022	$ 172,797		$ 199		$ 489,662		$ (317,064)