Note 9 - Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2023

Notes Tables

Disclosure of Share-Based Compensation Arrangements by Share-Based Payment Award [Table Text Block]

(in thousands, except for weighted-average data)
Stock Options	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (In Yrs)
Outstanding at January 1, 2023		78		$	381.00
Granted		213			1.21
Forfeited or expired		(12	)		259.02
Outstanding at September 30, 2023		279		$	93.29		9.0
Vested and exercisable at September 30, 2023		57		$	434.41		6.0
Vested and expected to vest at September 30, 2023		259		$	94.61		9.0

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

(in thousands, except for weighted-average data)
Restricted Stock Units	Shares			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2023		11		$	49.50
Awarded		142			1.21
Vested		(3	)		48.55
Cancelled		(3	)		49.57
Outstanding at September 30, 2023		147		$	2.94

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

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2023		2022		2023		2022
Research and development	$	93	$	198	$	280	$	580
General and administrative		212		546		692		1,715
Total	$	305	$	744	$	972	$	2,295

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

	Nine Months Ended September 30,
	2023			2022
Weighted average expected volatility		112	%		106	%
Weighted average expected term (in years)		6.0			6.9
Weighted average risk-free interest rate		4.33	%		1.70	%
Expected dividends		-			-