Stock-Based Compensation - Stock-Based Compensation Expense, Net of Estimated Forfeitures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Stock-based compensation expense by condensed consolidated statement of operations and comprehensive loss
Total expense	$ 21	$ 217	$ 418	$ 624
Research and development
Stock-based compensation expense by condensed consolidated statement of operations and comprehensive loss
Total expense	(26)	134	167	380
General and administrative
Stock-based compensation expense by condensed consolidated statement of operations and comprehensive loss
Total expense	$ 47	$ 83	$ 251	$ 244