Note 12 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	December 31,
	201 9			201 8
Deferred tax assets, net:
Net operating loss carryforwards	$	109,813		$	103,612
Research and other credits		3,482			3,482
Operating lease assets		(170	)		—
Operating lease liabilities		198			—
Other temporary differences		4,851			3,760
Deferred tax assets		118,175			110,854
Valuation allowance		(118,175	)		(110,854	)
Net deferred tax assets	$	—		$	—

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

	Year Ended December 31,
	201 9			201 8
Federal income tax at statutory rate		21.0	%		21.0	%
State income taxes, net of federal benefits		7.0	%		6.2	%
Impact of change in statutory tax rates		(0.2	%)		(8.8	%)
Permanent deductions		(0.1	%)		(3.7	%)
Valuation allowance		(27.7	%)		(14.7	%)
Effective tax rate		—	%		—	%