Note 8 - Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2022

Notes Tables

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
	(000’s)				(000’s)
Research and development	$	170	$	178	$	718	$	476
General and administrative		1,117		809		3,587		2,367
Total	$	1,287	$	987	$	4,305	$	2,843

Nonvested Restricted Stock Shares Activity [Table Text Block]

	Shares			Fair Value
Weighted Average Fair Value	(000's)			Per Share
Unvested, December 31, 2021		471		$	1.76
Granted		—		$	—
Vested		(198	)	$	1.79
Forfeited or canceled		(20	)	$	1.77
Unvested, September 30, 2022		253		$	1.73

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

				Weighted		Weighted
	Number of			Average		Average		Aggregate
	Unvested			Exercise		Remaining		Intrinsic
	Options			Price		Contractual		Value
	(000's)			Per Share		Term (in years)		($000's)
Outstanding at December 31, 2021		3,659		$	4.99		8.67
Granted		2,277		$	2.30		9.38
Exercised		(2	)	$	1.56
Forfeited/canceled		(334	)	$	4.07
Outstanding at September 30, 2022		5,600		$	3.97		8.70	$	277
Vested at September 30, 2022		2,472		$	4.74		8.22	$	19

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

	Nine Months Ended September 30,
	2022			2021
Expected term (in years)		6.0			6.1
Risk-free rate		2.02	%		0.76	%
Expected volatility		94	%		90	%
Expected dividend yield		—			—

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

	Shares (000's)		Weighted Average Price Per Share		Weighted Average Fair Value ($000's)
Unvested, December 31, 2021		1,200	$	3.83	$	4,596
Granted		—		—		—
Vested		—		—		—
Forfeited or canceled		—		—		—
Unvested, September 30, 2022		1,200	$	3.83	$	4,596