On February 22, 2024, 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 240,000,000 shares to 360,000,000 shares, (the “Share Increase Amendment”). At the Company’s annual meeting of stockholders held on April 4, 2024, the Company’s stockholders approved the Share Increase Amendment. On April 5, 2024, 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 three and six months ended June 30, 2024, the Company sold 0 and 15,366,630 shares, respectively, of common stock under the Sales Agreement, at an average price of $0 and approximately $1.23 per share, respectively, raising aggregate net proceeds of approximately $0 and $18,409, after deducting an aggregate commission of approximately 3% and other issuance costs. During the three and six months ended June 30, 2023, the Company sold 1,218,377 and 2,005,547 shares, respectively, of common stock under the Sales Agreement, at an average price of approximately $6.40 and $6.11 per share, respectively, raising aggregate net proceeds of approximately $7,491 and $11,730, respectively, after deducting an aggregate commission of approximately 3% and other issuance costs.

The following table summarizes the Company’s stock option activity since December 31, 2023:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding as of December 31, 2023		14,844,112		$	9.64		5.71	$	—
Granted		7,173,731		$	1.05
Exercised		—		$	—
Forfeited		(2,710,547	)	$	8.56
Outstanding as of June 30, 2024		19,307,296		$	6.60		7.39	$	—
Vested or expected to vest as of June 30, 2024		19,307,296		$	6.60		7.39	$	—
Options exercisable as of June 30, 2024		9,715,178		$	10.07		5.62	$	—

The weighted average grant date fair value of stock options granted during the three and six months ended June 30, 2024 and 2023 was $0.65, $0.93, $4.54 and $4.56 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 $(37), $8, $2,373 and $2,373 of compensation expense during the three and six months ended June 30, 2024 and 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 was recognized as of April 2024, for all such options for which ongoing performance targets were achieved and service requirements were met.

During the three months ended March 31, 2024, the Company granted stock options to certain executives for the purchase of an aggregate of 2,550,010 shares of common stock. These awards will vest only to the extent that the 30-day trailing simple average public market closing price of the Company's common stock reaches certain price thresholds. These awards have an exercise price of $1.10 and vest and become exercisable when the market conditions are satisfied or, if later, on the first anniversary of the grant date. These awards expire 10 years from the date of grant. The fair value of these market-based stock options was estimated using a Monte Carlo valuation method. During the three and six months ended June 30, 2024, the Company recognized $284 and $426 of compensation expense related to these awards, respectively.

The Company has granted restricted stock units with service-based vesting conditions (“RSUs”) and restricted stock units with performance-based vesting conditions (“PSUs”). RSUs and PSUs represent the right to receive shares of common stock upon meeting specified vesting requirements. Restricted stock units may not be sold or transferred by the holder and vest according to the vesting conditions of each award. The following table summarizes the Company’s RSU and PSU activity since December 31, 2023:


	Number of Shares			Weighted Average Grant Date Fair Value
Unvested restricted stock units as of December 31, 2023		3,377,804		$	4.26
Granted		1,288,127		$	1.09
Vested		(521,869	)	$	5.73
Forfeited		(336,619	)	$	3.24
Unvested restricted stock units as of June 30, 2024		3,807,443		$	3.07

During the three and six months ended June 30, 2024 and 2023, the Company granted 5,186, 1,288,127, 28,700 and 1,720,795 RSUs, respectively. During the three and six months ended June 30, 2024 and 2023, the Company granted 0, 0, 0 and 1,322,715 PSUs, respectively. 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.

In November 2023, as part of the corporate restructuring described in Note 12, Restructuring, the Company issued retention awards to employees of the Company in the form of RSUs which vest in two tranches on August 15, 2024, and May 15, 2025, subject to remaining actively employed with the Company through such date. The compensation expense associated with these awards will be recognized ratably over the vesting period. For the three and six months ended June 30, 2024, the Company recognized $173 and $358, respectively, in compensation expense with respect to the retention awards.

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 $267, $527, $2,768 and $2,768 in compensation expense during the three and six months ended June 30, 2024 and 2023, respectively, with respect to these PSUs. The remaining $398 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 June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development expenses	$	2,835	$	7,851	$	6,445	$	11,582
General and administrative expenses		2,699		5,641		5,578		8,760
	$	5,534	$	13,492	$	12,023	$	20,342