Note 8 - Stock-based Compensation

9 Months Ended

Sep. 30, 2025

Notes to Financial Statements

Share-Based Payment Arrangement [Text Block]

8. Stock-Based Compensation

Stock-based compensation expense for the three and nine months ended September 30, 2025 and 2024 was classified in the condensed consolidated statement of operations as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2025		2024		2025		2024
Research and development	$	852	$	244	$	2,516	$	1,626
General and administrative		386		1,954		4,027		4,696
Total	$	1,238	$	2,198	$	6,543	$	6,322

As of September 30, 2025, the remaining unrecognized stock-based compensation cost from all plans to be recognized in future periods totaled $17.5 million.

2020 Plan

In September 2020, the Company’s board of directors adopted the 2020 Stock Option and Incentive Plan (the “2020 Plan”) and reserved 2.9 million shares of common stock for issuance under this plan. The 2020 Plan includes automatic annual increases. The increase on January 1, 2025 was 5.5 million shares. As of September 30, 2025, 5.0 million shares remain available for grant.

The 2020 Plan authorizes the board of directors or a committee of the board to grant incentive stock options, nonqualified stock options, restricted stock awards and restricted stock units ("RSUs") to eligible officers, employees, consultants and directors of the Company. Options generally vest over a period of four years and have a contractual life of ten years from the date of grant.

Stock Options:

The following table summarizes the stock option activity for the 2020 Plan:

				Weighted		Weighted
	Number of			Average		Average		Aggregate
	Unvested			Exercise		Remaining		Intrinsic
	Options			Price		Contractual		Value
	(000's)			Per Share		Term (in years)		($000's)
Outstanding at December 31, 2024		14,062		$	2.83		6.23	$	579
Granted		4,592		$	3.61		9.29		2
Exercised		—		$	—		—		—
Forfeited/canceled		(1,491	)	$	2.32		—		1,842
Outstanding at September 30, 2025		17,163		$	3.08		6.87	$	12,890
Vested at September 30, 2025		9,228		$	3.39		5.16	$	5,977

For the nine months ended September 30, 2025 and 2024, the weighted average grant date fair value for options granted was $2.68 and $1.13, respectively. The intrinsic value for options vested as of September 30, 2025 and 2024, was $6.0 million and $0.1 million, respectively. As of September 30, 2025, the total unrecognized compensation cost related to outstanding options was $15.5 million, to be recognized over a weighted average period of 1.4 years.

The weighted average assumptions used in the Black-Scholes pricing model to determine the fair value of stock options granted during the nine months ended September 30, 2025 and 2024 were as follows:

	Nine Months Ended September 30,
	2025			2024
Expected term (in years)		6.0			6.0
Risk-free rate		4.3	%		3.9	%
Expected volatility		86	%		81	%
Expected dividend yield		—			—

RSUs:

The following table summarizes the RSU activity for the 2020 Plan:

	Shares (000's)			Weighted Average Price Per Share		Weighted Average Fair Value ($000's)
Unvested, December 31, 2024		3,766		$	2.41	$	9,076
Granted		—			—		—
Vested		(823	)		2.48		(2,041	)
Forfeited or canceled		(1,665	)		2.34		(3,891	)
Unvested, September 30, 2025		1,278		$	2.46	$	3,144

As of September 30, 2025, the remaining unrecognized compensation cost related to RSUs to be recognized in future periods totaled $2.0 million, which is expected to be recognized over a weighted average period of 1.2 years.