Note 11 - Stock Option Plans (Tables)

6 Months Ended

Jun. 30, 2023

Notes Tables

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

	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)		Aggregate Intrinsic Value
Outstanding options, December 31, 2022		7,095,462		$	1.99		5.79	$	109,891
Granted		2,911,750		$	0.57
Forfeited		(33,847	)	$	2.26
Exercised		(3,500	)	$	0.54
Expired		(32,076	)	$	4.90
Outstanding options, June 30, 2023		9,937,789		$	1.56		6.59	$	1,660,330
Options vested and exercisable, June 30, 2023		4,539,909		$	2.01		3.23	$	637,770

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

	Three Months Ended June 30,						Six Months Ended June 30,
	2023			2022			2023			2022
Expected volatility		80.2 - 81.5	%		85.4	%		80.2 - 81.9	%		78.0 - 85.4	%
Weighted-average volatility		80.9	%		85.4	%		81.7	%		79.0	%
Expected dividends		—	%		—	%		—	%		—	%
Expected term (in years)		5.77 - 6.08			5.89			5.77 - 6.08			5.50 - 6.08
Risk-free rate		3.50 - 3.90	%		3.03	%		3.50 - 3.90	%		1.38 - 3.03	%

Nonvested Restricted Stock Shares Activity [Table Text Block]

	Number of shares			Weighted Average Grant Date Fair Value
Unvested as of December 31, 2022		350,000		$	1.72
Granted		318,875		$	0.54
Vested		(75,000	)	$	1.72
Unvested as of June 30, 2023		593,875		$	1.06

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
Research and development	$	166,534	$	149,814	$	314,225	$	518,039
General and administrative		478,281		420,047		933,370		949,422
Total	$	644,815	$	569,861	$	1,247,595	$	1,467,461