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)		308,356
Issuance of common stock under employee stock purchase plan	195		195
Issuance of common stock for services (in shares)		711,675
Issuance of common stock for services	390		390
Issuance of common stock upon vesting of restricted stock units (in shares)		3,091,697
Issuance of common stock in at the market offering (in shares)		53,105,382
Issuance of common stock in at the market offering	52,845	$ 6	52,839
Stock-based compensation	8,824		8,824
Unrealized gains (losses) on available-for-sale securities	(108)				(108)
Net income (loss)	(77,902)			(77,902)
Ending balance (in shares) at Sep. 30, 2022		187,399,645
Ending balance at Sep. 30, 2022	66,861	$ 19	857,788	(790,832)	(114)
Beginning balance (in shares) at Jun. 30, 2022		153,797,834
Beginning balance at Jun. 30, 2022	53,042	$ 15	821,075	(767,939)	(109)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock purchase plan (in shares)		181,256
Issuance of common stock under employee stock purchase plan	112		112
Issuance of common stock for services (in shares)		711,675
Issuance of common stock for services	390		390
Issuance of common stock upon vesting of restricted stock units (in shares)		95,555
Issuance of common stock in at the market offering (in shares)		32,613,325
Issuance of common stock in at the market offering	34,367	$ 4	34,363
Stock-based compensation	1,848		1,848
Unrealized gains (losses) on available-for-sale securities	(5)				(5)
Net income (loss)	(22,893)			(22,893)
Ending balance (in shares) at Sep. 30, 2022		187,399,645
Ending balance at Sep. 30, 2022	66,861	$ 19	857,788	(790,832)	(114)
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)		435,708
Issuance of common stock under employee stock purchase plan	808		808
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)	127,000	127,221
Issuance of common stock upon exercise of options	$ 251		251
Issuance of common stock upon vesting of restricted stock units (in shares)		634,351
Issuance of common stock in at the market offering (in shares)		32,274,741
Issuance of common stock in at the market offering	119,248	$ 3	119,245
Stock-based compensation	9,600		9,600
Unrealized gains (losses) on available-for-sale securities	(147)				(147)
Net income (loss)	(37,265)			(37,265)
Ending balance (in shares) at Sep. 30, 2023		232,133,132
Ending balance at Sep. 30, 2023	191,161	$ 23	1,008,741	(817,402)	(201)
Beginning balance (in shares) at Jun. 30, 2023		217,862,921
Beginning balance at Jun. 30, 2023	123,161	$ 22	947,380	(824,031)	(210)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock purchase plan (in shares)		269,739
Issuance of common stock under employee stock purchase plan	670		670
Issuance of common stock upon exercise of options (in shares)		28,227
Issuance of common stock upon exercise of options	40		40
Issuance of common stock upon vesting of restricted stock units (in shares)		211,277
Issuance of common stock in at the market offering (in shares)		13,760,968
Issuance of common stock in at the market offering	57,163	$ 1	57,162
Stock-based compensation	3,489		3,489
Unrealized gains (losses) on available-for-sale securities	9				9
Net income (loss)	6,629			6,629
Ending balance (in shares) at Sep. 30, 2023		232,133,132
Ending balance at Sep. 30, 2023	$ 191,161	$ 23	$ 1,008,741	$ (817,402)	$ (201)