Note 10 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

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

	Years ended December 31,
	2016			2015			2014
Domestic	$	(15,860	)	$	(21,377	)	$	(3,342	)
Foreign		(12,666	)		-			-
Loss before income taxes	$	(28,526	)	$	(21,377	)	$	(3,342	)

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

	Year Ended December 31,
	2016			2015			2014
Income tax benefit using U.S. federal statutory rate	$	(9,696	)	$	(7,315	)	$	(1,136	)
Permanent differences		430			260			124
Orphan Drug credit permanent addback		1,437			1,310			674
State income taxes, net of federal benefit		(498	)		(808	)		(303	)
Tax credits		(4,846	)		(4,219	)		(2,176	)
Expired net operating losses and tax credits		-			-			312
Change in valuation allowance		8,804			9,782			4,394
Mark-to-market derivative liability		-			-			(1,779	)
Foreign rate differential		4,304			-			-
Other		65			990			(110	)
		-		$	-		$	-

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

	Year Ended December 31,
	2016			2015			2014
Net operating loss carryforwards	$	37,237		$	34,488		$	29,217
Federal and state tax credits		21,223			16,404			12,126
Accrued expenses		544			27			478
Patents		360			443			531
Stock-based compensation		1,353			596			92
Other		321			276			8
		61,038			52,234			42,452
Valuation allowance		(61,038	)		(52,234	)		(42,452	)
Net deferred tax asset	$	-		$	-		$	-