Note 6 - Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Notes Tables

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

	Three Months Ended March 31,
	2019		2018
Research and development	$	13,596	$	16,372
General and administrative		77,608		308,295
Total stock-based compensation expense	$	91,204	$	324,667

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)	Aggregate intrinsic value
Balance at January 1, 2019		203,736		$	88.14		$	143
Granted		59,670			2.10
Forfeited		(7,202	)		123.38
Expired		(147	)		276.00
Outstanding at March 31, 2019		256,057		$	66.99	7.19	$	96,716
Exercisable at March 31, 2019		175,720		$	93.36	6.19	$	8,651

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

Expected term (in years)	5.77
Risk-free interest rate	2.5	%
Expected volatility	114.4	%
Dividend yield	—