Note 8 - Stock Based Awards (Tables)

3 Months Ended

Mar. 31, 2023

Notes Tables

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

						Weighted
						Average
				Weighted		Remaining		Aggregate
				Average		Contractual		Intrinsic
	Number of			Exercise		Life		Value
	Shares			Price		(in years)		(in thousands)
Balances, January 1, 2023		4,570,432		$	2.50
Options granted		2,707,654			1.67
Options expired		(43,838	)		6.18
Balances, March 31, 2023		7,234,248		$	2.17		8.1	$	3,677
Outstanding and expected to vest as of March 31, 2023		6,286,788		$	2.22		7.9	$	3,328
Exercisable as of March 31, 2023		2,619,503		$	2.74		5.6	$	1,814

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

	March 31,			March 31,
	2023			2022
Expected volatility		115.9	%		112.0	%
Risk-free interest rate		3.5	%		1.7	%
Dividend yield		0.0	%		0.0	%
Expected life (in years)		6.0			6.1