Note 9 - Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

Schedule of Share-based Compensation, Expense [Table Text Block]

	Years ended
	December 31,
	2022		2021
Research and development	$	528	$	795
Selling, general and administrative		655		866
Total share-based compensation	$	1,183	$	1,661

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

	Options outstanding
	Number of shares			Weighted average exercise price		Weighted average remaining contractual term (years)		Aggregate intrinsic value (in thousands)
Balance, December 31, 2021		1,649,686		$	5.00		7.6	$	-
Stock options granted		644,853			1.55
Stock options exercised		—			—
Stock options forfeited		(108,720	)		3.77
Stock options expired		(3,111	)		9.55
Balance, December 31, 2022		2,182,708		$	4.04		7.5	$	343
Exercisable, December 31, 2022		1,144,240		$	5.48		6.4	$	47
Options vested and expected to vest		2,182,708		$	4.04		7.5	$	343

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

	Years ended
	December 31,
	2022			2021
Risk-free interest rate	1.8	-	3.8%	0.4	-	1.6%
Volatility	116	-	122%	107	-	112%
Dividend yield		None			None
Expected term (in years)	6.25	-	10.0	6.25	-	10.0

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

				Weighted
				average
				grant date
	Number of			fair value
	shares			per share
Balance, December 31, 2021		200,271		$	4.13
RSUs granted		287,839			1.51
RSUs released		(371,980	)		2.75
RSUs forfeited		(94,604	)		1.52
Balance, December 31, 2022		21,526		$	4.33