Note 11 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2023

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 (Millions)
Outstanding at December 31, 2022		7,584,967		$	4.22		5.31
Granted		3,047,615		$	0.71
Exercised		(13,300	)	$	0.38
Cancelled		(16,762	)	$	27.89
Forfeited		(106	)	$	15.86
Outstanding at June 30, 2023		10,602,414		$	3.18		5.34	$	0.2
Vested or expected to vest at June 30, 2023		10,028,804		$	3.32		5.29	$	0.2
Exercisable at June 30, 2023		5,411,149		$	5.31		4.58	$	0.2

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

	Six Months Ended June 30,
	2023				2022
Expected volatility		124%	-	130%		128%	-	133%
Risk-free interest rate		3.53%	-	4.14%		1.25%	-	2.98%
Expected life (in years)		3.8	-	4.5		4.3	-	4.5
Expected dividend yield			0%				0%
Weighted average grant date fair value	$			0.59	$			0.61

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

	Number of Shares			Weighted- Average Grant Date Fair Value
Outstanding at December 31, 2022		8,483,491		$	1.04
Granted		8,163,060		$	0.72
Vested		(3,355,753	)	$	1.13
Forfeited		(352,110	)	$	0.82
Outstanding at June 30, 2023		12,938,688		$	0.82

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
	(in thousands)				(in thousands)
Stock options	$	591	$	924	$	1,256	$	1,901
Restricted stock units		977		822		1,836		1,707
Performance restricted stock units		410		337		802		720
	$	1,978	$	2,083	$	3,894	$	4,328