Note 12 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Notes Tables

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

	Number of Shares			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (thousands)
Outstanding at December 31, 2023		10,444,679		$	3.20		4.80
Granted		5,552,790			0.26
Cancelled		(110,980	)		15.61
Outstanding at June 30, 2024		15,886,489		$	2.07		5.14	$	389
Vested or expected to vest at June 30, 2024		14,894,960		$	2.18		5.06	$	334
Exercisable at June 30, 2024		7,919,713		$	3.74		4.04	$	-

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

	Six Months Ended June 30,
	2024					2023
Expected volatility		126%	-	127%		124%	-	126%
Risk-free interest rate		4.06%	-	4.07%		3.73%	-	4.14%
Expected life (in years)		4.3	-	4.5		4.3	-	4.5
Expected dividend yield		0			%		0		%

Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]

	Number of Shares			Weighted-Average Grant Date Fair Value
Unvested at December 31, 2023		12,326,177		$	0.81
Granted		14,953,974		$	0.26
Vested		(5,455,413	)	$	0.91
Forfeited		(1,396,905	)	$	0.66
Unvested at June 30, 2024		20,427,833		$	0.39

Share-Based Payment Arrangement, Cost by Plan [Table Text Block]

	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
	(in thousands)
Stock options	$	341	$	591	$	766	$	1,256
Restricted stock units		844		977		1,800		1,836
Performance restricted stock units		343		410		707		802
	$	1,528	$	1,978	$	3,273	$	3,894