Note 7 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

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

	Year ended December 31,
	2021		2020
Research and development	$	154,041	$	164,791
General and administrative		743,219		571,328
Total stock-based compensation expense	$	897,260	$	736,119

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, 2020		309,276		$	55.78
Granted		1,931,100			0.68
Expired		(172	)		142.50
Balance at December 31, 2020		2,240,204		$	8.28			$	289,067
Granted		1,815,767			0.89
Forfeited		(429,748	)		1.37
Outstanding at December 31, 2021		3,626,223			5.40		8.52		—
Exercisable at December 31, 2021		2,140,524		$	8.58		8.09		—
Vested and expected to vest at December 31, 2021		3,626,223		$	5.40		8.52		—

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

	2021			2020
Expected term (in years)		10		5.31	—	10
Risk-free interest rate	1.3%	—	1.7%	0.4%	—	1.7%
Expected volatility	122.6%	—	125.8%	113.4%	—	124.8%
Dividend yield		0%			0%

Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]

	Number of Units			Weighted average grant date fair value
Balance at January 1, 2021		153,000		$	0.65
Granted		138,800			0.72
Vested(1)		(16,350	)		0.51
Outstanding at December 31, 2021		275,450		$	0.70