Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2020	$ 66,266	$ 48	$ 570,841	$ 1	$ (504,624)
Beginning balance, shares at Dec. 31, 2020		48,318,970
Issuance of common stock and pre- funded warrants, net of issuance costs (unaudited)	32,207	$ 9	32,198
Issuance of common stock and prefunded warrants, net of issuance costs (unaudited), shares		8,298,890
Issuance of common stock upon exercise of stock options (unaudited)	6		6
Issuance of common stock upon exercise of stock options (unaudited), shares		2,836
Issuance of common stock under employee stock purchase plan (unaudited)	122		122
Issuance of common stock under employee stock purchase plan (unaudited), shares		60,619
Stock-based compensation expense (unaudited)	3,774		3,774
Net loss (unaudited)	(24,722)				(24,722)
Unrealized gain on available-for-sale securities (unaudited)	0
Ending balance at Jun. 30, 2021	77,653	$ 57	606,941	1	(529,346)
Ending balance (unaudited), shares at Jun. 30, 2021		56,681,315
Beginning balance at Mar. 31, 2021	56,024	$ 48	572,805	5	(516,834)
Beginning balance, shares at Mar. 31, 2021		48,319,202
Issuance of common stock and pre- funded warrants, net of issuance costs (unaudited)	32,207	$ 9	32,198
Issuance of common stock and prefunded warrants, net of issuance costs (unaudited), shares		8,298,890
Issuance of common stock upon exercise of stock options (unaudited)	5		5
Issuance of common stock upon exercise of stock options (unaudited), shares		2,604
Issuance of common stock under employee stock purchase plan (unaudited)	122		122
Issuance of common stock under employee stock purchase plan (unaudited), shares		60,619
Stock-based compensation expense (unaudited)	1,811		1,811
Net loss (unaudited)	(12,512)				(12,512)
Unrealized gain on available-for-sale securities (unaudited)	(4)			(4)
Ending balance at Jun. 30, 2021	77,653	$ 57	606,941	$ 1	(529,346)
Ending balance (unaudited), shares at Jun. 30, 2021		56,681,315
Beginning balance at Dec. 31, 2021	54,907	$ 57	610,655		(555,805)
Beginning balance, shares at Dec. 31, 2021		56,732,474
Issuance of common stock upon vesting of restricted stock units (unaudited)	$ 41		41
Issuance of common stock upon vesting of restricted stock units (unaudited), shares		212,596
Issuance of common stock upon exercise of stock options (unaudited), shares	23,000
Issuance of common stock under employee stock purchase plan (unaudited)	$ 74		74
Issuance of common stock under employee stock purchase plan (unaudited), shares		45,293
Stock-based compensation expense (unaudited)	3,688		3,688
Net loss (unaudited)	(26,633)				(26,633)
Unrealized gain on available-for-sale securities (unaudited)	0
Ending balance at Jun. 30, 2022	32,077	$ 57	614,458		(582,438)
Ending balance (unaudited), shares at Jun. 30, 2022		56,990,363
Beginning balance at Mar. 31, 2022	43,249	$ 57	612,549		(569,357)
Beginning balance, shares at Mar. 31, 2022		56,921,605
Issuance of common stock upon exercise of stock options (unaudited)	41		41
Issuance of common stock upon exercise of stock options (unaudited), shares		23,465
Issuance of common stock under employee stock purchase plan (unaudited)	$ 74		74
Issuance of common stock under employee stock purchase plan (unaudited), shares	45,293
Stock-based compensation expense (unaudited)	$ 1,794		1,794
Net loss (unaudited)	(13,081)				(13,081)
Unrealized gain on available-for-sale securities (unaudited)	0
Ending balance at Jun. 30, 2022	$ 32,077	$ 57	$ 614,458		$ (582,438)
Ending balance (unaudited), shares at Jun. 30, 2022		56,990,363