Note 10 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

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

	Year Ended December 31,
	2018			2017			2016
Domestic	$	(17,855	)	$	(24,803	)	$	(15,860	)
Foreign		(2,874	)		(5,161	)		(12,666	)
Total	$	(20,729	)	$	(29,964	)	$	(28,526	)

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

	Year Ended December 31,
	2018			2017			2016
Income tax benefit computed at federal statutory tax rate	$	(4,348	)	$	(10,186	)	$	(9,696	)
Permanent differences		6			4			430
Stock compensation - permanent items		325			689			-
R&D credit - permanent items		-			1,751			1,437
State income taxes, net of federal benefit		(958	)		(853	)		(498	)
Tax credits		(1,466	)		(5,495	)		(4,846	)
Change in valuation allowance		5,409			(54,319	)		8,804
Foreign rate differential		602			1,752			4,304
Rate change		-			2,202			-
382 limitation		-			64,975			-
Other		430			(520	)		65
Total	$	-		$	-		$	-

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

	Year Ended December 31,
	2018			2017			2016
Deferred tax assets:
Net operating loss carryforwards	$	6,742		$	2,651		$	37,237
Federal and state tax credits		3,122			2,244			21,223
Accrued expenses		411			399			544
Patents		132			191			360
Stock-based compensation		1,782			1,262			1,353
Other		169			202			321
Total deferred tax assets		12,358			6,949			61,038
Valuation allowance		(12,358	)		(6,949	)		(61,038	)
Net deferred assets	$	-		$	-		$	-