Note 8 - Stock Based Awards (Tables)

3 Months Ended

Mar. 31, 2022

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, 2022		2,439,253		$	3.96
Options granted		1,543,200			2.14
Options cancelled		(305,378	)		3.70
Options exercised		—			—
Balances, March 31, 2022		3,677,075		$	3.22		7.8	$	1,379
Outstanding and expected to vest as of March 31, 2022		3,176,415		$	3.23		7.5	$	1,377
Exercisable as of March 31, 2022		1,647,359		$	2.89		5.7	$	1,371

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

	March 31,			March 31,
	2022			2021
Expected volatility		112.0	%		113.5	%
Risk-free interest rate		1.7	%		0.6	%
Dividend yield		0.0	%		0.0	%
Expected life (in years)		6.1			6.1