Note 12 - Stock-based Compensation

3 Months Ended

Mar. 31, 2026

Notes to Financial Statements

Share-Based Payment Arrangement [Text Block]

Note 12—Stock-Based Compensation

Our equity incentive plans provide for the grant of incentive and non-qualified stock options, restricted stock awards, restricted stock units, and other stock awards to employees, non-employee directors, and consultants.

Stock-based compensation is as follows:

		Three Months Ended
		March 31,
		2026				2025
		(In thousands)

Research and development		$	801			$	1,036
Selling, general and administrative			1,088				1,417
Total stock-based compensation		$	1,889			$	2,453

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The following assumptions were applied to all stock option grants:

		Three Months Ended
		March 31, 2026
Estimated weighted-average fair value		$	11.15
Weighted-average assumptions:
Expected volatility			102	%
Expected life, in years			7.0
Risk-free interest rate			3.96	%
Expected dividend yield			—	%

Expected volatility is based on the historical volatility of our stock price weighted by grant issuances over the reporting period. We estimated the expected life of the stock options granted using the historical exercise behavior of option holders. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Forfeiture expense is estimated at the time of grant and revised in subsequent periods if actual forfeitures differ from those estimates.

Stock option activity for all stock plans and related information is as follows:

						Weighted-
						Average								Aggregate
						Exercise				Remaining				Intrinsic
		Options				Price per				Contractual Life				Value
		Outstanding				Share				(In years)				(In thousands)
Balance at December 31, 2025			18,273,105			$	7.27
Granted			116,500				13.21
Exercised			(1,039,990	)			8.05
Forfeited			(142,534	)			5.70
Balance at March 31, 2026			17,207,081			$	7.28				6.1			$	76,045
Vested and expected to vest at March 31, 2026			16,711,585			$	7.39				6.0			$	72,523
Exercisable at March 31, 2026			12,266,686			$	8.84				5.0			$	40,423

Of the 17.2 million common stock options outstanding as of March 31, 2026, options to purchase 6.0 million shares have an exercise price per share above $10.56, which was the closing price of our stock on the Nasdaq Global Market on March 31, 2026.

As of March 31, 2026, there were 4.9 million unvested options outstanding that will vest over a weighted-average period of 2.5 years. The total estimated compensation expense yet to be recognized on outstanding options is $11.4 million.

As of March 31, 2026, the total number of shares of common stock available for grant was 3.9 million.