Income Taxes - (Details - Components of Net Deferred Tax Assets) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 774	$ 11,808
Tax credit carryforwards	295	1,227
Stock-based compensation	80	435
Capitalized research and development expenses	1,384	1,662
License fees	3	1,680
Lease liability	9	46
Other timing differences	13	120
Deferred tax assets	2,558	16,978
Deferred tax liabilities:
Right of use asset	(9)	(43)
Deferred tax liability	(9)	(43)
Valuation allowance	(2,549)	(16,935)
Net deferred tax asset	$ 0	$ 0