Note 4 - Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property and equipment, gross	$ 788	$ 788
Less accumulated depreciation	(713)	(694)
Property and equipment, net	75	94
Computer Equipment and Software [Member]
Property and equipment, gross	161	161
Laboratory and Manufacturing Equipment [Member]
Property and equipment, gross	574	574
Furniture and Fixtures [Member]
Property and equipment, gross	27	27
Leasehold Improvements [Member]
Property and equipment, gross	$ 26	$ 26