Note 12 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	Year Ended December 31,
	2022			2021
Tax at federal statutory rate	$	(3,701	)	$	(3,657	)
State taxes, net of federal benefit		(916	)		(711	)
Permanent differences		(484	)		(445	)
Change in valuation allowance		5,084			5,104
Research credits		(273	)		(286	)
Nondeductible interest expense		290			—
Other		—			(5	)
Provision for taxes	$	—		$	—

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

	As of December 31,
	2022			2021
Deferred tax assets:
Federal, state and foreign net operating losses	$	85,547		$	83,211
Research and other credits		5,343			4,892
Operating lease liability		544			752
Fixed assets		471			—
Accruals and other		3,628			2,845
Capitalized research and development		1,019			—
Total deferred tax assets		96,552			91,700
Less: Valuation allowance		(95,992	)		(90,908	)
Total net deferred tax assets		560			792
Deferred liabilities:
Property and equipment		—			(2	)
Operating lease right of use asset		(560	)		(790	)
Total deferred tax liabilities		(560	)		(792	)
Net deferred tax assets (liabilities)	$	—		$	—

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

	As of December 31,
	2022		2021
Balance at beginning of year	$	2,366	$	2,307
Increase based on the tax positions in the current year		203		228
Increase (Decrease) for tax positions of prior year		12		(169	)
Balance at end of year	$	2,581	$	2,366