On March 29, 2023, the Company’s board of directors adopted a resolution to amend the Restated Certificate of Incorporation, subject to stockholder approval, by increasing the number of authorized shares of the Company’s Common Stock from 200,000,000 shares to 240,000,000 shares (the “Share Increase Amendment”). At the Company’s annual meeting of stockholders held on June 22, 2023, the Company’s stockholders approved the Share Increase Amendment. On June 27, 2023, the Company amended its Restated Certificate of Incorporation to reflect the Share Increase Amendment.

On May 21, 2021, the Company entered into a Sales Agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”) to sell shares of the Company’s common stock, with aggregate gross sales proceeds of up to $150,000, from time to time, through an “at the market” equity offering program under which Cowen acts as sales agent. During the nine months ended September 30, 2023, the Company sold 2,005,547 shares of common stock under the Sales Agreement, at an average price of approximately $6.11 per share, raising aggregate net proceeds of approximately $11,730, after deducting an aggregate commission of approximately 3% and other issuance costs. During the three and nine months ended September 30, 2022, the Company did not sell any shares of common stock under the Sales Agreement.

The following table summarizes the Company’s stock option activity since December 31, 2022:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding as of December 31, 2022		14,940,034		$	10.03		7.25	$	11,608
Granted		2,507,053
Exercised		(260,640	)
Forfeited		(816,324	)
Outstanding as of September 30, 2023		16,370,123		$	9.47		6.78	$	135
Options exercisable as of September 30, 2023		10,000,136		$	10.05		5.67	$	—

The weighted average grant date fair value of stock options granted during the three and nine months ended September 30, 2023 and 2022 was $3.14, $4.52, $4.07, and $5.53 per share, respectively.

During the year ended December 31, 2021, the Company granted performance-based stock options to employees for the purchase of an aggregate of approximately 562,000 shares of common stock with a grant date fair value of $5.53 per share. These stock options are exercisable only upon achievement of specified performance targets. In April 2023, the performance target associated with 50% of the performance-based stock options was achieved. Accordingly, the Company recorded $109 and $2,481 of compensation expense during the three and nine months ended September 30, 2023, respectively, with respect to these performance-based stock options, which represents a cumulative catch-up from the grant date through the achievement of the performance targets, and vesting of the remaining 50% of the options beginning in April 2023. The remaining compensation expense associated with these performance-based stock options will be recognized ratably through April 2024, for all such options for which ongoing performance targets are achieved and service requirements are met.

The following table summarizes the Company’s restricted stock unit activity since December 31, 2022:


	Number of Shares			Weighted Average Grant Date Fair Value
Unvested restricted stock units as of December 31, 2022		1,549,540		$	9.37
Granted		3,128,818		$	5.45
Vested		(539,537	)	$	9.62
Forfeited		(312,126	)	$	8.13
Unvested restricted stock units as of September 30, 2023		3,826,695		$	6.23

The Company has granted restricted stock units with service-based vesting conditions (“RSUs”) and performance-based vesting conditions (“PSUs”). RSUs and PSUs represent the right to receive shares of common stock upon meeting specified vesting requirements. RSUs and PSUs may not be sold or transferred by the holder and vest according to the service-based or performance-based vesting conditions of the award. During the three and nine months ended September 30, 2023 and 2022, the Company granted 85,308, 1,806,103, 114,600, and 1,224,494 RSUs, respectively. During the three and nine months ended September 30, 2023, the Company granted 0 and 1,322,715 PSUs, respectively. The Company did not grant any PSUs during the three and nine months ended September 30, 2022. RSUs generally vest over four years, with 25% vesting after one year, and the remaining 75% vesting quarterly over the next 3 years, subject to continued service to the Company through the applicable vesting date. PSUs vest according to the performance requirements of the awards, generally when the Company has determined that the specified performance targets have been achieved.

During the year ended December 31, 2021, the Company granted PSUs to two employees for the purchase of an aggregate of 85,000 shares of common stock with a grant date fair value of $9.59 per share and 40,000 shares of common stock with a grant date fair value of $20.35 per share. These PSUs vest only upon achievement of specified performance targets. In October 2022, 42,500 of the PSUs with a grant date fair value of $9.59, and 20,000 of the PSUs with a grant date fair value of $20.35, vested fully, as the associated performance targets were achieved. Accordingly, the Company recorded $815 in compensation expense during the year ended December 31, 2022, with respect to these PSUs. In April 2023, the remaining PSUs underlying these awards vested because the associated targets were achieved. Accordingly, the Company recorded the remaining $815 in compensation expense during the nine months ended September 30, 2023, with respect to these PSUs.

During the three months ended March 31, 2023, the Company granted PSUs to employees for the purchase of an aggregate of 1,322,715 shares of common stock with a grant date fair value of $5.50. These PSUs begin to vest ratably only upon achievement of specified performance targets, which were achieved in April 2023. Accordingly, the Company recorded $1,610 and $4,378 in compensation expense during the three and nine months ended September 30, 2023, respectively, with respect to these PSUs. The remaining $2,459 in compensation expense associated with these PSUs will be recognized ratably through October 2024.

The Company recorded stock-based compensation expense in the following expense categories of its condensed consolidated statements of operations and comprehensive loss (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development expenses	$	4,744	$	3,474	$	16,326	$	9,500
General and administrative expenses		3,929		2,890		12,689		8,691
	$	8,673	$	6,364	$	29,015	$	18,191