The Company grants stock-based incentive awards pursuant to the 2021 Equity and Incentive Plan (the ‘2021 Plan’), 2019 Equity Incentive Plan (the ‘2019 Plan’), Apexigen Equity Incentive Plans (the ‘Apexigen Plan’) and the 2022 Equity Inducement Plan (the ‘2022 Inducement Plan’). As of March 31, 2025, there were 4,072,703 shares, 132,435 shares, 764,154 shares and 413,537 shares available for future issuance under the 2021 Plan, 2019 Plan, Apexigen Plan and 2022 Inducement Plan, respectively.

The following table summarizes stock option activity for the three months ended March 31, 2025 (in thousands, except share and per share amounts):


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding at January 1, 2025		9,711,075		$	5.04		8.2	$	44
Granted		3,104,372			0.98
Forfeited		(587,279	)		2.01
Outstanding at March 31, 2025		12,228,168		$	4.16		8.2	$	21
Options exercisable March 31, 2025		4,379,232		$	7.00		6.2	$	21

The aggregate intrinsic value is calculated as the difference between the exercise price of all outstanding and exercisable stock options and the fair value of the Company’s common stock of $0.98 per share as of March 31, 2025. The aggregate intrinsic value of stock options exercised during the three months ended March 31, 2025 and 2024 was $0 and $0.2 million, respectively, as no stock options were exercised during the three months ended March 31, 2025.

The Company has an aggregate $11.0 million of gross unrecognized stock-based compensation expense as of March 31, 2025, remaining to be amortized over a weighted average period of 1.94 years.

The weighted-average grant-date fair value of options granted during the three months ended March 31, 2025 and 2024, was $0.78 and $2.32 per share, respectively, and was calculated using the following key input assumptions in the Black-Scholes option-pricing model:


	Three Months Ended March 31,
	2025	2024
Expected volatility	93.920% - 99.910%	99.41% - 102.27%
Risk-free interest rate	3.960% - 4.450%	4.06% - 4.23%
Expected dividend yield	0.00%	0.00%
Expected term (in years)	5.00 - 6.08	5.00 - 6.08

The following table summarizes restricted stock units activity for the three months ended March 31, 2025:


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding at January 1, 2025		2,533,650		$	3.26
Forfeited		(80,804	)		3.18
Vested and settled		(30,892	)		3.73
Outstanding at March 31, 2025(1)		2,421,954		$	3.26

(1) Includes 361,263 RSUs which are vested but not settled at March 31, 2025.

During the three months ended March 31, 2025, the Company issued 22,728 shares of its common stock from the settlement of 30,892 restricted common units, with the remaining shares withheld for taxes. The Company has an aggregate $5.04 million of gross unrecognized restricted stock-based compensation expense as of March 31, 2025, remaining to be amortized over a weighted average period of 2.4 years.

The following table summarizes the total stock-based compensation expense for the three months ended March 31, 2025 and 2024, respectively (in thousands):


	Three Months Ended March 31,
	2025		2024
General and administrative	$	2,509	$	3,642
Research and development		1,122		678
Total	$	3,631	$	4,320

The Company has the 2021 ESPP in force. The Company issued 29,619 shares under the 2021 ESPP during the three months ended March 31, 2025. The company did not issue any shares during the three months ended March 31, 2024. As of March 31, 2025, 653,777 shares are available for issuance under the 2021 ESPP.