Note 9 - Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 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
Forfeited or expired		(7	)		319.69
Outstanding at March 31, 2023		71		$	376.68		7.1
Vested and exercisable at March 31, 2023		53		$	456.01		6.6
Vested and expected to vest at March 31, 2023		69		$	377.17		7.1

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
Vested		(3	)		51.00
Cancelled		(1	)		48.61
Outstanding at March 31, 2023		7		$	49.31

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

	Three Months Ended March 31,
(in thousands)	2023		2022
Research and development	$	129	$	235
General and administrative		156		535
Total	$	285	$	770

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

	Three Months Ended March 31,
	2022
Weighted average expected volatility		106%
Weighted average expected term (in years)		6.9
Weighted average risk-free interest rate		1.70%
Expected dividends		-