Note 8 - Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2025

Notes Tables

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2025		2024		2025		2024
Research and development	$	852	$	244	$	2,516	$	1,626
General and administrative		386		1,954		4,027		4,696
Total	$	1,238	$	2,198	$	6,543	$	6,322

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, 2024		14,062		$	2.83		6.23	$	579
Granted		4,592		$	3.61		9.29		2
Exercised		—		$	—		—		—
Forfeited/canceled		(1,491	)	$	2.32		—		1,842
Outstanding at September 30, 2025		17,163		$	3.08		6.87	$	12,890
Vested at September 30, 2025		9,228		$	3.39		5.16	$	5,977

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

	Nine Months Ended September 30,
	2025			2024
Expected term (in years)		6.0			6.0
Risk-free rate		4.3	%		3.9	%
Expected volatility		86	%		81	%
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, 2024		3,766		$	2.41	$	9,076
Granted		—			—		—
Vested		(823	)		2.48		(2,041	)
Forfeited or canceled		(1,665	)		2.34		(3,891	)
Unvested, September 30, 2025		1,278		$	2.46	$	3,144