Note 4 - Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property and equipment, gross	$ 1,203	$ 1,170
Less accumulated depreciation	(1,039)	(1,025)
Property and equipment, net	164	145
Computer Equipment and Software [Member]
Property and equipment, gross	166	159
Laboratory and Manufacturing Equipment [Member]
Property and equipment, gross	574	550
Furniture and Fixtures [Member]
Property and equipment, gross	59	59
Leasehold Improvements [Member]
Property and equipment, gross	332	332
Construction in Progress [Member]
Property and equipment, gross	$ 72	$ 70

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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