Stockholders' Equity and Stock Options (Tables)

9 Months Ended

Sep. 30, 2024

Stockholders' Equity Note [Abstract]

Assumptions used to Determine Fair Value of Stock Options Granted

The following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted to employees:

	September 30,
	2024
Risk-free interest rate	4.12%
Expected term (in years)	6.22
Expected volatility	96%
Dividend yield	0.00%

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity for the nine months ended September 30, 2024 (amounts in millions, except for share, contractual term, and per share data):

				Weighted		Weighted Average		Aggregate
				Average		Remaining		Intrinsic
	Number of			Exercise		Contractual		Value (a)
	Shares			Price		Term (in years)		(in millions)
Outstanding as of December 31, 2023		4,273,502		$	9.06		7.8
Options granted		2,082,377			5.22
Options exercised		(6,967	)		5.92
Options forfeited/expired		(57,088	)		10.08
Outstanding as of September 30, 2024		6,291,824		$	7.79		7.8	$	7.4
Exercisable as of September 30, 2024		2,921,508		$	10.63		6.5	$	1.7
Vested and expected to vest as of September 30, 2024		6,291,824		$	7.79		7.8	$	7.4

(a)The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for the options that were "in the money" at September 30, 2024.

Summary of Restricted Stock Units

Activity with respect to the Company's RSUs during the nine months ended September 30, 2024 was as follows (in millions, except share, contractual term, and per share data):

				Weighted		Weighted Average		Aggregate
				Average		Remaining		Intrinsic
	Number of			Grant Date		Contractual		Value (a)
	Shares			Fair Value		Term (in years)		(in millions)
Outstanding as of December 31, 2023		615,000		$	4.94		1.6
Restricted stock units granted		245,372			4.21
Restricted stock units vested		(153,750	)		4.94
Restricted stock units forfeited		(7,619	)		4.64
Outstanding as of September 30, 2024		699,003		$	4.69		1.5	$	4.6
Unvested and expected to vest as of September 30, 2024		699,003		$	4.69		1.5	$	4.6

Summary of Stock-Based Compensation Expense

Stock-based compensation expense was classified in the condensed consolidated statements of operations as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development	$	918	$	697	$	2,816	$	2,304
General and administrative		1,039		1,124		3,570		3,393
	$	1,957	$	1,821	$	6,386	$	5,697