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)		2,996,142
Issuance of common stock in at the market offering (in shares)		20,492,057
Issuance of common stock in at the market offering	18,478	$ 2	18,476
Stock-based compensation	6,976		6,976
Unrealized losses on available-for-sale securities	(103)				(103)
Net loss	(55,009)			(55,009)
Ending balance (in shares) at Jun. 30, 2022		153,797,834
Ending balance at Jun. 30, 2022	53,042	$ 15	821,075	(767,939)	(109)
Beginning balance (in shares) at Mar. 31, 2022		136,330,360
Beginning balance at Mar. 31, 2022	64,190	$ 14	805,265	(741,001)	(88)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon vesting of restricted stock units (in shares)		2,882,673
Issuance of common stock in at the market offering (in shares)		14,584,801
Issuance of common stock in at the market offering	12,557	$ 1	12,556
Stock-based compensation	3,254		3,254
Unrealized losses on available-for-sale securities	(21)				(21)
Net loss	(26,938)			(26,938)
Ending balance (in shares) at Jun. 30, 2022		153,797,834
Ending balance at Jun. 30, 2022	53,042	$ 15	821,075	(767,939)	(109)
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 for services (in shares)		86,095
Issuance of common stock for services	$ 337		337
Issuance of common stock upon exercise of options (in shares)	99,000	98,994
Issuance of common stock upon exercise of options	$ 211		211
Issuance of common stock upon vesting of restricted stock units (in shares)		423,074
Issuance of common stock in at the market offering (in shares)		18,513,773
Issuance of common stock in at the market offering	62,085	$ 2	62,083
Stock-based compensation	6,111		6,111
Unrealized losses on available-for-sale securities	(156)				(156)
Net loss	(43,894)			(43,894)
Ending balance (in shares) at Jun. 30, 2023		217,862,921
Ending balance at Jun. 30, 2023	123,161	$ 22	947,380	(824,031)	(210)
Beginning balance (in shares) at Mar. 31, 2023		214,462,050
Beginning balance at Mar. 31, 2023	125,421	$ 21	932,330	(806,910)	(20)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for services (in shares)		86,095
Issuance of common stock for services	337		337
Issuance of common stock upon exercise of options (in shares)		62,993
Issuance of common stock upon exercise of options	149		149
Issuance of common stock upon vesting of restricted stock units (in shares)		215,301
Issuance of common stock in at the market offering (in shares)		3,036,482
Issuance of common stock in at the market offering	11,366	$ 1	11,365
Stock-based compensation	3,199		3,199
Unrealized losses on available-for-sale securities	(190)				(190)
Net loss	(17,121)			(17,121)
Ending balance (in shares) at Jun. 30, 2023		217,862,921
Ending balance at Jun. 30, 2023	$ 123,161	$ 22	$ 947,380	$ (824,031)	$ (210)