Note 14 - Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

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

	Period ended June 30,
	2021			2020
Risk-free interest rate		0.89%-1.08	%		0.28%-0.47	%
Expected term	5.31-6.17 years			4.50-6.18 years
Dividend yield		-			-
Expected volatility		122%-130%			103%-125%

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

	Number of Underlying Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Contractual Life Remaining in Years		Aggregate Intrinsic Value
Outstanding as of January 1, 2021		7,067,436		$	2.74		-
Granted		3,643,921			2.97		-		96,050
Exercised		-			-		-
Forfeited		(75,000	)		3.05		-
Expired		-			-		-		-
Outstanding as of June 30, 2021		10,636,357			2.82		8.71	$	44,150,423
Exercisable as of June 30, 2021		5,552,436			2.96		7.91	$	25,562,663
Vested and expected to vest		10,636,357		$	2.82		8.71	$	44,150,423

Share-based Payment Arrangement, Option [Member]

Notes Tables

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
General and administrative	$	852,583	$	702,561	$	1,302,527	$	1,185,561
Research and development		361,527		333,923		551,334		538,675
Total stock compensation expense	$	1,214,110	$	1,036,484	$	1,853,861	$	1,724,236