Note 5 - Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

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

	Year Ended December 31,
	2016		2015
Research and development costs	$	1,767,732	$	1,394,194
General and administrative expenses		1,677,807		1,557,173
Total	$	3,445,539	$	2,951,367

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

	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at January 1, 2016		1,315,666		$	27.09		5.0	$	550,000
Granted		436,347		$	7.91
Exercised		-			-
Forfeited/Expired		(60,026	)	$	14.05
Outstanding at December 31, 2016		1,691,987		$	22.60		5.1	$	-
Exercisable at December 31, 2016		1,303,198		$	26.42		4.1	$	-
Vested and expected to vest at December 31, 2016		1,685,187		$	22.67		5.1	$	-

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

Range of Exercise Prices			Number of Options Outstanding		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
$3.50	-	$13.00		718,072	$	9.72		7.3	$	-
$13.01	-	$26.00		379,774	$	15.30		5.1		-
$26.01	-	$39.00		163,032	$	32.35		2.5		-
$39.01	-	$65.00		431,109	$	46.77		2.4		-
				1,691,987	$	22.60		5.1	$	-

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

	Year Ended December 31,
	2016			2015
Annual dividend		-			-
Expected life (in years)	5.8	-	7.3	4.0	-	6.0
Risk free interest rate	1.34%	-	1.75%	1.39%	-	1.78%
Expected volatility	69.0%	-	80.2%	68.6%	-	71.8%

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

	Number of RSU's			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2016		11,615		$	27.69
Granted		-
Exercised and converted to common shares		(4,250	)	$	22.96
Forfeited		(502	)	$	26.26
Outstanding at December 31, 2016		6,863		$	30.70
Exercisable at December 31, 2016		6,863		$	30.70

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

	Number of Warrants			Weighted- Average Exercised Price		Weighted-Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at January 1, 2016		1,511,763		$	30.36		3.1	$	309,724
Granted		1,757,712		$	3.25		4.4
Exercised		-		$	-
Forfeited		(110,771	)	$	50.10
Outstanding at December 31, 2016		3,158,704		$	14.58		3.4	$	454,000
Exercisable at December 31, 2016		3,152,920		$	14.60		3.5	$	454,000

Restricted Stock [Member]

Notes Tables

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

	Shares of Restricted Stock			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2016		16,455		$	24.31
Granted		-
Vested		(16,455	)	$	24.31
Forfeited		-
Outstanding at December 31, 2016		-