In September 2019, the Company’s board of directors adopted the 2019 Equity Incentive Plan (the “2019 Plan”), which also became effective in September 2019. The Company initially reserved 2,844,193 shares of common stock for issuance under the 2019 Plan. In addition, the number of shares of common stock reserved for issuance under the 2019 Plan will automatically increase on the first day of January for a period of up to ten years in an amount equal to 4% of the total number of shares of the Company’s capital stock outstanding on the immediately preceding December 31, or a lesser number of shares determined by the Company’s board of directors.

In February 2023, the Company’s board of directors adopted the 2023 Inducement Plan (the “2023 Plan”), which also became effective in February 2023. The Company initially reserved 1,500,000 shares of common stock for issuance under the 2023 Plan. Under the 2023 Plan, new employees are eligible to receive equity awards as a material inducement to the commencement of employment with the Company. During the three and nine months ended September 30, 2023, options to purchase an aggregate of 279,600 and 417,700 shares, respectively, were granted to 14 and 20 new employees, respectively, under the 2023 Plan.

In October 2019, the Company’s board of directors adopted the 2019 Employee Stock Purchase Plan (“ESPP”), which became effective in November 2019. The Company initially reserved 225,188 shares of common stock for purchase under the ESPP. The number of shares of common stock reserved for issuance under the ESPP will automatically increase on the first day of January for a period of up to ten years in an amount equal to 1% of the total number of shares of the Company’s common stock outstanding on the immediately preceding December 31, or a lesser number of shares determined by the Company’s board of directors. Purchases are accomplished through the participation of discrete offering periods and each offering is expected to be six months in duration. For each offering period, ESPP participants will purchase shares of common stock at a price per share equal to 85% of the lesser of the fair

market value of the Company’s common stock on (1) the first trading day of the applicable offering period or (2) the last trading day of the applicable offering period.

The following table summarizes stock option activity under the Company's equity incentive plans for the nine months ended September 30, 2023:


						Weighted
				Weighted		Average
				Average		Remaining		Aggregate
	Number of			Exercise		Contractual		Intrinsic
	Options			Price		Term		Value
						(In years)		(In thousands)
Balance outstanding as of December 31, 2022		3,161,917		$	12.80		7.9	$	16,612
Granted		1,783,900			15.18
Exercised		(196,612	)		3.20
Cancelled and forfeited		(70,178	)		10.77
Balance outstanding as of September 30, 2023		4,679,027		$	14.14		8.0	$	19,912
Exercisable as of September 30, 2023		2,005,286		$	14.22		6.8	$	12,824

The Company has granted certain employees service-based RSUs that generally vest annually over a two or three-year period. The restrictions lapse over time for these service-based RSUs. In the event of termination of the holder’s continuous service to the Company, any unvested portion of the service-based RSUs is cancelled. For the three months ended September 30, 2023 and 2022, the Company recognized $0.9 million and $0.3 million, respectively, in expense related to the service-based RSUs. For the nine months ended September 30, 2023 and 2022, the Company recognized $2.4 million and $0.7 million, respectively, in expense related to the service-based RSUs.

In February 2021, the Company granted performance-based RSUs that vest as to one-third on each one-year anniversary date, subject to achievement of a development milestone and continued service to the Company. In each of February 2022 and 2023, a portion of the performance-based RSUs vested upon achievement of the development milestone and satisfaction of the continued service condition.

In February and September 2022, the Company granted performance-based RSUs that vest during the applicable performance period, subject to the achievement of certain corporate or department targets and continued service to the Company. In September 2022, March 2023 and June 2023, a portion of the performance-based RSUs that were granted in February 2022 vested upon achievement of specific targets and satisfaction of the continued service condition.

As of September 30, 2023, it was probable that the remaining performance conditions would be met for the Company’s performance-based RSUs and expense was recognized using the accelerated attribution method. For the three months ended September 30, 2023 and 2022, the Company recognized expense of $0.2 million and $0.3 million, respectively, related to performance-based RSUs. For the nine months ended September 30, 2023 and 2022, the Company recognized $0.8 million and $1.1 million, respectively, in expense related to the performance-based RSUs.

The following table summarizes RSU activity for the nine months ended September 30, 2023:


	Number of RSUs			Weighted Average Fair Value at Date of Grant per Unit
Balance outstanding as of December 31, 2022		1,095,738		$	5.77
Granted		379,075			15.02
Vested / released		(309,740	)		5.82
Cancelled / forfeited		(177,523	)	$	5.89
Balance outstanding as of September 30, 2023		987,550		$	9.28

The Company recorded stock-based compensation for the periods indicated as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	1,938	$	1,019	$	5,136	$	2,917
General and administrative		2,443		1,481		6,933		4,681
Total stock-based compensation	$	4,381	$	2,500	$	12,069	$	7,598