Note 11 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Year Ended December 31,
	2014		2013		2012
Research and development	$	114	$	106	$	46
General and administrative		345		49		64
Total	$	459	$	155	$	110

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year Ended December 31,
	2014			2013
Weighted average expected volatility		79.5	%		91.1	%
Expected term (in years)		6.00			5.95
Risk free interest rate		1.88	%		1.03	%
Expected dividend yield		0	%		0	%

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Outstanding at December 31, 2013		607,017		$	2.22		5.2	$	1,627
Granted		659,865		$	5.94
Exercised		(31,356	)	$	1.89
Cancelled or forfeited		-		$	-
Outstanding at December 31, 2014		1,235,526		$	4.19		7.1	$	7,709
Exercisable at December 31, 2014		572,184		$	2.36		4.5	$	4,615
Vested or expected to vest at December 31, 2014 (1)		1,163,249		$	4.13		7.0	$	7,327