CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive income (loss)	Accumulated Deficit
Balance at Dec. 31, 2020	$ 6,118	$ 25	$ 241,649	$ 12	$ (235,568)
Balance (in shares) at Dec. 31, 2020		24,976,142
Share-based compensation expense	1,791		1,791
Exercise of stock options	235		235
Exercise of stock options, shares		217,015
Unrealized loss on short-term investments	(2)			(2)
Net loss	(18,715)				(18,715)
Balance at Mar. 31, 2021	(10,573)	$ 25	243,675	10	(254,283)
Balance (in shares) at Mar. 31, 2021		25,193,157
Balance at Dec. 31, 2021	$ (58,004)	$ 26	258,086	(14)	(316,102)
Balance (in shares) at Dec. 31, 2021	26,458,767	26,458,767
Share-based compensation expense	$ 1,848		1,848
Exercise of stock options	$ 58		58
Exercise of stock options, shares	46,358	46,358
Sale of shares under Open Market Sale Agreement, net	$ (1,117)	$ (1)	(1,116)
Sale of shares under open market sale agreement, shares		(314,296)
Unrealized loss on short-term investments	(47)			(47)
Net loss	(15,443)				(15,443)
Balance at Mar. 31, 2022	$ (70,471)	$ 27	$ 261,108	$ (61)	$ (331,545)
Balance (in shares) at Mar. 31, 2022	26,819,421	26,819,421