Note 8 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Notes Tables

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
	(000’s)				(000’s)
Research and development	$	174	$	139	$	548	$	298
General and administrative		1,270		809		2,470		1,558
Total	$	1,444	$	948	$	3,018	$	1,856

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		(136	)	$	1.82
Forfeited or canceled		(20	)	$	1.77
Unvested, June 30, 2022		315		$	1.74

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		2,229		$	2.29		9.53
Exercised		—
Forfeited/cancelled		(244	)	$	4.06
Outstanding at June 30, 2022		5,644		$	3.97		8.94	$	839
Vested at June 30, 2022		2,182		$	4.86		9.29	$	47

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

	Six Months Ended June 30,
	2022			2021
Expected term (in years)		5.8			6.1
Risk-free rate		1.93	%		0.76	%
Expected volatility		90.3	%		89.3	%
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, June 30, 2022		1,200	$	3.83	$	4,596