Note 4 - Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property and equipment, gross	$ 848	$ 669
Less: accumulated depreciation	(503)	(459)
Property and equipment, net	345	210
Laboratory Equipment [Member]
Property and equipment, gross	706	537
Office Equipment [Member]
Property and equipment, gross	$ 142	$ 132

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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