Note 6 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2020

Notes Tables

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Research and development	$	91,896	$	13,577	$	188,426	$	27,173
General and administrative		21,548		135,503		116,398		213,111
Total stock-based compensation expense	$	113,444	$	149,080	$	304,824	$	240,284

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, 2020		309,276		$	55.78
Granted		1,118,700			0.58
Expired		(147	)		142.50
Outstanding at June 30, 2020		1,427,829		$	12.53		8.9
Exercisable at June 30, 2020		660,504		$	26.17		8.2

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

	2020
Expected term (in years)		5.59
Risk-free interest rate		1.3	%
Expected volatility		115.1	%
Dividend yield		—	%