Property and Equipment - Net Property and Equipment at Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment
Total property and equipment, at cost	$ 819	$ 819
Less: Accumulated depreciation and amortization	812	797
Property and equipment, net	7	22
Leasehold improvements
Property, Plant and Equipment
Total property and equipment, at cost	107	107
Laboratory equipment and other
Property, Plant and Equipment
Total property and equipment, at cost	$ 712	$ 712