CONDENSED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning balance (in shares) at Dec. 31, 2021		130,182,535
Beginning balance at Dec. 31, 2021	$ 82,617	$ 13	$ 795,540	$ (712,930)	$ (6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock purchase plan (in shares)		127,100
Issuance of common stock under employee stock purchase plan	83		83
Issuance of common stock upon vesting of restricted stock units (in shares)		113,469
Issuance of common stock in at the market offering (in shares)		5,907,256
Issuance of common stock in at the market offering	5,921	$ 1	5,920
Stock-based compensation	3,722		3,722
Unrealized gains (losses) on available-for-sale securities	(82)				(82)
Net loss	(28,071)			(28,071)
Ending balance (in shares) at Mar. 31, 2022		136,330,360
Ending balance at Mar. 31, 2022	64,190	$ 14	805,265	(741,001)	(88)
Beginning balance (in shares) at Dec. 31, 2022		198,575,016
Beginning balance at Dec. 31, 2022	98,329	$ 20	878,500	(780,137)	(54)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock purchase plan (in shares)		165,969
Issuance of common stock under employee stock purchase plan	$ 138		138
Issuance of common stock upon exercise of options (in shares)	36,000	36,001
Issuance of common stock upon exercise of options	$ 62		62
Issuance of common stock upon vesting of restricted stock units (in shares)		207,773
Issuance of common stock in at the market offering (in shares)		15,477,291
Issuance of common stock in at the market offering	50,719	$ 1	50,718
Stock-based compensation	2,912		2,912
Unrealized gains (losses) on available-for-sale securities	34				34
Net loss	(26,773)			(26,773)
Ending balance (in shares) at Mar. 31, 2023		214,462,050
Ending balance at Mar. 31, 2023	$ 125,421	$ 21	$ 932,330	$ (806,910)	$ (20)