Note 10 - Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2024

Notes Tables

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

	Number of shares			Weighted average exercise price		Weighted average remaining contractual life (in years)		Aggregate intrinsic value (in thousands)
Outstanding as of December 31, 2023		264,983		$	18.30		7.7	$	75
Expired/Forfeited		(89,546	)
Outstanding as of March 31, 2024		175,437		$	18.60		8.4	$	40
Expired/Forfeited		(14,000	)
Outstanding as of June 30, 2024		161,437		$	21.18		7.5	$	—
Expired/Forfeited		(29,604	)
Outstanding as of September 30, 2024		131,833		$	21.01		7.4	$	—
Options vested and exercisable as of September 30, 2024		109,399		$	24.13		7.1	$	—

Nonvested Restricted Stock Shares Activity [Table Text Block]

	Awards			Weighted Average Grant Date Fair Value
Balance as of December 31, 2023 (unvested)		124,166		$	5.20
Vested		(57,500	)		4.64
Balance as of March 31, 2024 (unvested)		66,666			5.66
Vested		—			—
Balance as of June 30, 2024 (unvested)		66,666			5.66
Vested		(33,333	)		2.08
Balance as of September 30, 2024 (unvested)		33,333		$	5.66

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

	Three months ended September 30,				Nine months ended September 30,
	2024		2023		2024		2023
	(Unaudited)
Stock-based compensation expense
General and administrative	$	82	$	261	$	365	$	1,295
Research and development		22		90		78		295
Total stock-based compensation expense	$	104	$	351	$	443	$	1,590