CONDENSED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Preferred stock Convertible preferred stock	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance, preferred stock shares (in shares) at Dec. 31, 2021		5,571,959
Beginning balance, common stock shares (in shares) at Dec. 31, 2021			14,597,118
Beginning balance at Dec. 31, 2021	$ 54,958	$ 5	$ 15	$ 509,791	$ 0	$ (454,853)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Employee Stock Purchase Plan (in shares)			996
Issuance of common stock under Employee Stock Purchase Plan	2			2
Stock-based compensation expense	1,000			1,000
Gain on short-term investments	0
Net loss	(6,719)					(6,719)
Ending balance, preferred stock shares (in shares) at Mar. 31, 2022		5,571,959
Ending balance, common stock shares (in shares) at Mar. 31, 2022			14,598,114
Ending balance at Mar. 31, 2022	$ 49,241	$ 5	$ 15	510,793	0	(461,572)
Beginning balance, preferred stock shares (in shares) at Dec. 31, 2022		5,571,959
Beginning balance, common stock shares (in shares) at Dec. 31, 2022	16,840,261		16,840,261
Beginning balance at Dec. 31, 2022	$ 33,291	$ 5	$ 17	516,457	(12)	(483,176)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Employee Stock Purchase Plan (in shares)			19,472
Issuance of common stock under Employee Stock Purchase Plan	21			21
Stock-based compensation expense	410			410
Gain on short-term investments	12				12
Net loss	$ (7,139)					(7,139)
Ending balance, preferred stock shares (in shares) at Mar. 31, 2023		5,571,959
Ending balance, common stock shares (in shares) at Mar. 31, 2023	16,859,733		16,859,733
Ending balance at Mar. 31, 2023	$ 26,595	$ 5	$ 17	$ 516,888	$ 0	$ (490,315)