Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	2021 Sales Agreement [Member]	Common Stock [Member]	Common Stock [Member] 2021 Sales Agreement [Member]	Common Stock [Member] February 2023 Registered Direct Offering [Member]	Additional paid-in capital [Member]	Additional paid-in capital [Member] 2021 Sales Agreement [Member]	Accumulated other comprehensive loss [Member]	Accumulated deficit [Member]
Beginning balance at Dec. 31, 2022	$ 24,985		$ 23			$ 586,357		$ (13)	$ (561,382)
Beginning balance, shares at Dec. 31, 2022			22,785,000
Issuance of common stock in the February 2023 registered direct offering/pursuant to the 2021 Sales Agreement, shares					1,700,000
Stock-based compensation expense from stock options and ESPP shares	2,338					2,338
Net loss	(11,987)								(11,987)
Net change in unrealized loss on available-for-sale securities, net of reclassification adjustments and taxes	6							6
Ending balance at Mar. 31, 2023	15,342		$ 23			588,695		(7)	(573,369)
Ending balance, shares at Mar. 31, 2023			24,485,000
Beginning balance at Dec. 31, 2022	24,985		$ 23			586,357		(13)	(561,382)
Beginning balance, shares at Dec. 31, 2022			22,785,000
Net loss	(23,168)
Ending balance at Jun. 30, 2023	5,500		$ 23			590,033		(6)	(584,550)
Ending balance, shares at Jun. 30, 2023			24,609,000
Beginning balance at Mar. 31, 2023	15,342		$ 23			588,695		(7)	(573,369)
Beginning balance, shares at Mar. 31, 2023			24,485,000
Issuance of common stock in the February 2023 registered direct offering/pursuant to the 2021 Sales Agreement		$ 658					$ 658
Issuance of common stock in the February 2023 registered direct offering/pursuant to the 2021 Sales Agreement, shares				118,000
Issuance of common stock upon exercise of stock options and from the ESPP	23					23
Issuance of common stock upon exercise of stock options and from the ESPP, shares			6,000
Stock-based compensation expense from stock options and ESPP shares	657					657
Net loss	(11,181)								(11,181)
Net change in unrealized loss on available-for-sale securities, net of reclassification adjustments and taxes	1							1
Ending balance at Jun. 30, 2023	5,500		$ 23			590,033		(6)	(584,550)
Ending balance, shares at Jun. 30, 2023			24,609,000
Beginning balance at Dec. 31, 2023	14,783		$ 23			603,780		(14)	(589,006)
Beginning balance, shares at Dec. 31, 2023			30,334,000
Issuance of common stock in the February 2023 registered direct offering/pursuant to the 2021 Sales Agreement		$ 648					$ 648
Issuance of common stock in the February 2023 registered direct offering/pursuant to the 2021 Sales Agreement, shares				702,000
Stock-based compensation expense from stock options and ESPP shares	508					508
Net loss	(7,643)								(7,643)
Net change in unrealized loss on available-for-sale securities, net of reclassification adjustments and taxes	4							4
Ending balance at Mar. 31, 2024	8,300		$ 23			604,936		(10)	(596,649)
Ending balance, shares at Mar. 31, 2024			31,036,000
Beginning balance at Dec. 31, 2023	14,783		$ 23			603,780		(14)	(589,006)
Beginning balance, shares at Dec. 31, 2023			30,334,000
Net loss	(11,343)
Ending balance at Jun. 30, 2024	5,037		$ 23			605,370		(7)	(600,349)
Ending balance, shares at Jun. 30, 2024			31,039,000
Beginning balance at Mar. 31, 2024	8,300		$ 23			604,936		(10)	(596,649)
Beginning balance, shares at Mar. 31, 2024			31,036,000
Issuance of common stock upon exercise of stock options and from the ESPP	3					3
Issuance of common stock upon exercise of stock options and from the ESPP, shares			3,000
Stock-based compensation expense from stock options and ESPP shares	431					431
Net loss	(3,700)								(3,700)
Net change in unrealized loss on available-for-sale securities, net of reclassification adjustments and taxes	3							3
Ending balance at Jun. 30, 2024	$ 5,037		$ 23			$ 605,370		$ (7)	$ (600,349)
Ending balance, shares at Jun. 30, 2024			31,039,000