Note 11 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]

	Year Ended December 31,
	2022			2021			2020
Domestic	$	(58,505	)	$	(63,660	)	$	(49,851	)
Foreign		—			—			—
	$	(58,505	)	$	(63,660	)	$	(49,851	)

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

	December 31,
	2022		2021		2020
Current
Federal	$	—	$	—	$	—
State		3		3		3
Foreign		—		—		—
Total current		3		3		3
Deferred
Federal		—		—		—
State		—		—		—
Foreign		—		—		—
Total deferred		—		—		—
Total provision for income taxes	$	3	$	3	$	3

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

	Year Ended December 31,
	2022			2021			2020
Federal tax at statutory rate		21.0	%		21.0	%		21.0	%
State tax at statutory rate		8.4			8.4			8.4
Research and development credits		0.9			1.9			2.1
Change in valuation allowance		(18.4	)		(26.8	)		(43.3	)
Deferred adjustment		(5.3	)		—			8.5
Change in tax rate		—			—			4.2
Uncertain Tax Position		(5.7	)		(2.3	)		—
Other		(0.9	)		(2.2	)		(0.8	)
Provision for income taxes		—	%		—	%		—	%

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

	December 31,
	2022			2021
Deferred tax assets
Accruals	$	3,404		$	1,034
Net operating loss carryforwards		56,447			49,246
Tax credit carryforwards		7,111			6,611
Stock-based compensation		8,784			12,188
R&D Capitalization		3,810			—
Lease liability under ASC 842		2,948			3,182
Gross deferred tax assets		82,504			72,261
Valuation allowance		(79,779	)		(69,006	)
Total deferred tax assets		2,725			3,255
Deferred tax liabilities
Intangibles		(117	)		(365	)
ROU asset under ASC 842		(2,593	)		(2,862	)
Fixed assets		(15	)		(28	)
Total deferred tax liabilities		(2,725	)		(3,255	)
Net deferred tax assets/(liabilities)	$	—		$	—

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

	December 31,
	2022		2021		2020
Unrecognized tax benefits at beginning of year	$	5,140	$	2,491	$	1,470
Increases related to current year tax positions		2,055		2,649		1,021
Increases related to prior year tax positions		1,730		—		—
Unrecognized tax benefits at end of year	$	8,925	$	5,140	$	2,491