Note 8 - Share-based Compensation

6 Months Ended

Jun. 30, 2023

Notes to Financial Statements

Share-Based Payment Arrangement [Text Block]

(8) Share-Based Compensation

The share-based compensation expense is recorded in research and development, and selling, general and administrative expenses based on the employee's or non-employee’s respective function. No share-based compensation was capitalized during the periods presented. Share-based compensation expense for the three and six months ended June 30, 2023 and 2022 was recorded as follows (in thousands):

	Three months ended				Six months ended
	June 30,				June 30,
	2023		2022		2023		2022
Research and development	$	134	$	130	$	273	$	257
Selling, general and administrative		183		174		322		366
Total share-based compensation	$	317	$	304	$	595	$	623

The following table summarizes the activity of stock options and related information:

	Options outstanding
	Number of shares			Weighted average exercise price		Weighted average remaining contractual term (years)		Aggregate intrinsic value (in thousands)
Balance, December 31, 2022		2,182,708		$	4.04		7.5	$	343
Stock options granted		543,513			1.69
Stock options exercised		(199	)		1.49
Stock options forfeited		(119,941	)		2.36
Balance, June 30, 2023		2,606,081		$	3.63		7.3	$	1,189
Exercisable, June 30, 2023		1,443,515		$	4.83		6.0	$	315

Unrecognized share-based compensation for employee and nonemployee options granted through June 30, 2023 is approximately $2.1 million to be recognized over a remaining weighted average service period of 2.7 years.

Share-Based Compensation (RSUs)

The following summarizes the activity of non-vested RSUs:

				Weighted
				average
				grant date
	Number of			fair value
	shares			per share
Balance, December 31, 2022		21,526		$	4.33
RSUs granted		331,552			1.70
RSUs released		(241,197	)		1.93
RSUs forfeited		(111,881	)		1.70
Balance, June 30, 2023		—		$	n/a

RSUs vested and settled are converted into our common stock on a one-for-one basis. RSUs are generally subject to forfeiture if employment terminates prior to the release of vesting restrictions. The related compensation expense, which is based on the grant date fair value of our common stock multiplied by the number of units granted, is recognized ratably over the period during which the vesting restrictions lapse. Unrecognized share-based compensation for employee and nonemployee RSUs granted through June 30, 2023 was $0.