Note 9 - Stock Based Awards (Tables)

12 Months Ended

Dec. 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		2,888,641			1.61
Options cancelled		(757,462	)		3.81
Options exercised		—			—
Balances, December 31, 2022		4,570,432		$	2.50		7.2	$	1,239
Outstanding and expected to vest as of December 31, 2022		4,100,681		$	2.54		7.1	$	1,184
Exercisable as of December 31, 2022		2,348,015		$	2.89		5.3	$	877

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

	December 31,			December 31,
	2022			2021
Expected volatility		113.0	%		114.2	%
Risk-free interest rate		2.2	%		0.8	%
Dividend yield		0.0	%		0.0	%
Expected life (in years)		6.0			6.0

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

	Year Ended
	December 31,
	2022		2021
Operating Expenses
Research and development	$	889	$	932
General and administrative		1,671		1,325
Total	$	2,560	$	2,257