Note 13 - Stock-based Compensation

9 Months Ended

Sep. 30, 2022

Notes to Financial Statements

Share-Based Payment Arrangement [Text Block]

13. Stock-Based Compensation

The Company recorded total stock-based compensation expense for stock options, restricted stock units, or RSUs, and the Amended and Restated 2011 Employee Stock Purchase Plan, or the Amended ESPP, as follows (in thousands):

		Three Months Ended September 30,								Nine Months Ended September 30,
		2022				2021				2022				2021
Cost of goods sold		$	13			$	24			$	48			$	67
Research and development			139				216				466				597
Selling, general and administrative			549				981				1,723				2,818
Total		$	701			$	1,221			$	2,237			$	3,482

The following table summarizes restricted stock unit activity under the Company’s equity incentive plans:

						Weighted
		Number of				*Average*
		*Restricted*				Grant Date
		Stock Units				Fair Value
Restricted stock units outstanding, January 1, 2022			88,718			$	34.20
Granted			58,516				7.80
Vested			(44,232	)			35.60
Forfeited			(16,324	)			25.40
Restricted stock units outstanding, September 30, 2022			86,678			$	17.20

Upon vesting, certain of the Company’s RSUs may be settled on a net-exercise basis to cover any required withholding tax with the remaining amount converted into an equivalent number of shares of common stock. There were 0 and 7,098 shares of common stock underlying vested RSUs that were withheld during the three and nine months ended September 30, 2022, respectively, based on the value of the RSUs as determined by the Company’s closing stock price on the applicable vesting date.

The following table summarizes stock option activity under the Company’s equity incentive plans:

		Number of Stock Options Outstanding				Weighted- Average Exercise Price				Weighted- Average Remaining Contractual Life (Years)				Aggregate Intrinsic Value
														(in thousands)
January 1, 2022			714,202			$	59.80
Granted			117,032				7.80
Forfeited			(29,034	)			27.20
Expired			(68,892	)			60.80
Exercised			—				—
September 30, 2022			733,308			$	52.60				5.8			$	—

Vested and exercisable options—September 30, 2022			505,825			$	66.40				4.5			$	—
Vested and expected to vest—September 30, 2022			733,308			$	52.60				5.8			$	—

The per-share weighted average grant date fair value of the options granted for the nine months ended September 30, 2022 was estimated at $5.80 per share on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions:

		Nine months ended September 30, 2022
Expected term (in years)				6.3
Risk-free interest rate			1.6%	-	3.0%
Expected volatility				88%
Expected dividend rate				0%

As of September 30, 2022, there were 331,649 shares available for grant under the Company’s equity incentive plans and 211,876 shares available for grant under the Amended ESPP.