CONDENSED STATEMENTS OF REDEEMABLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Series B1 Redeemable Convertible Preferred Stock	Total
Beginning balance at Dec. 31, 2020	$ 38	$ 742,342	$ (833,552)		$ (91,172)
Beginning balance (in shares) at Dec. 31, 2020	38,291,000			24,000
Sale of common stock, net of issuance costs	$ 3	16,258			16,261
Sale of common stock, net of issuance costs (in shares)	3,195,000
Conversion of Series B1 preferred stock	$ 1	(1)
Conversion of Series B1 preferred stock (in shares)	1,415,000			(14,000)
Issuance of common stock under employee stock purchase plan		28			28
Issuance of common stock under employee stock purchase plan (in shares)	8,000
Issuance of common stock under equity incentive plan (vesting of restricted stock units) (in shares)	237,000
Issuance of common stock upon exercise of common stock options and warrants	$ 4	267			271
Issuance of common stock upon exercise of common stock options and warrants (in shares)	3,375,000
Issuance of common stock for services rendered		67			67
Issuance of common stock for services rendered (in shares)	16,000
Stock-based compensation expense		1,111			1,111
Net income (loss)			115,738		115,738
Ending balance at Mar. 31, 2021	$ 46	760,072	(717,814)		42,304
Ending balance (in shares) at Mar. 31, 2021	46,537,000			10,000
Beginning balance at Dec. 31, 2020	$ 38	742,342	(833,552)		(91,172)
Beginning balance (in shares) at Dec. 31, 2020	38,291,000			24,000
Conversion of Series B1 preferred stock (in shares)				(23,684)
Ending balance at Dec. 31, 2021	$ 53	764,861	(735,461)		$ 29,453
Ending balance (in shares) at Dec. 31, 2021	52,818,000				52,818,000
Sale of common stock, net of issuance costs		(15)			$ (15)
Issuance of common stock under employee stock purchase plan		16			16
Issuance of common stock under employee stock purchase plan (in shares)	42,000
Issuance of common stock under equity incentive plan (vesting of restricted stock units) (in shares)	27,000
Issuance of common stock for services rendered		22			22
Issuance of common stock for services rendered (in shares)	37,000
Stock-based compensation expense		545			545
Net income (loss)			(4,178)		(4,178)
Ending balance at Mar. 31, 2022	$ 53	$ 765,429	$ (739,639)		$ 25,843
Ending balance (in shares) at Mar. 31, 2022	52,924,000				52,924,000