Note 6 - Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Research and development	$	13,519	$	16,202	$	40,692	$	48,848
General and administrative		131,802		311,194		344,913		922,984
Total stock-based compensation expense	$	145,321	$	327,396	$	385,605	$	971,832

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of Options			Weighted average exercise price per share		Weighted average remaining contractual life (in years)
Balance at January 1, 2019		203,736		$	88.14
Granted		117,270			2.62
Forfeited		(11,583	)		83.81
Expired		(147	)		276.00
Outstanding at September 30, 2019		309,276		$	55.78	7.23
Exercisable at September 30, 2019		211,867		$	78.92	6.30

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

	2019			2018
Expected term (in years)		5.52			5.57
Risk-free interest rate		2.2	%		2.4	%
Expected volatility		113.4	%		114.7	%
Dividend yield		—	%		—	%