Note 8 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

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

	Year ended December 31,
	2020		2019
Research and development	$	164,791	$	54,155
General and administrative		571,328		461,607
Total stock-based compensation expense	$	736,119	$	515,762

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
Granted		117,270			2.62
Forfeited		(11,583	)		83.81
Expired		(147	)		276.00
Balance at December 31, 2019		309,276		$	55.78		6.98		—
Granted		1,931,100			0.68
Expired		(172	)		142.50
Outstanding at December 31, 2020		2,240,204		$	8.28		8.90	$	289,067
Exercisable at December 31, 2020		1,129,733		$	15.64		8.28	$	219,010
Vested and expected to vest at December 31, 2020		2,240,204		$	8.28		8.90	$	289,067

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

	2020			2019
Expected term (in years)	5.31	—	10.00	5.25	—	5.77
Risk-free interest rate	0.4%	—	1.7%	1.9%	—	2.5%
Expected volatility	113.4%	—	124.8%	112.4%	—	114.4%
Dividend yield	—	—	—	—	—	—