Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Summary of the Company's Stock Option Activity

The following is a summary of the Company’s stock option activity for the six months ended June 30, 2024:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (thousands)
Balance at January 1, 2024		14,909,912		$	6.84
Granted		3,720,292			3.84
Exercised		(12,823	)		2.49
Forfeited/Cancelled		(695,931	)		4.94
Balance at June 30, 2024		17,921,450		$	6.30		7.53	$	823
Options vested and expected to vest as of    June 30, 2024		17,921,450		$	6.30		7.53	$	823
Options vested and exercisable as of    June 30, 2024		9,611,809		$	7.69		6.48	$	551

Schedule of Assumptions Used to Determine the Fair Value of Options Granted

The fair value of options granted is estimated at the date of grant using the Black-Scholes option pricing model. Forfeitures are accounted for as incurred as a reversal of any share-based compensation expense related to options that will not vest. The assumptions that the Company used to determine the fair value of options granted to employees, non-employees and directors were as follows:

	Six Months Ended June 30,
	2024	2023
Risk-free interest rate	4.0%	4.0%
Expected volatility	80.5%	82.6%
Expected term (years)	5.7	6.0
Dividend yield	—	—

Summary of Restricted Stock Unit (RSU) Activity

The following is a summary of the Company’s restricted stock unit (“RSU”) activity for the six months ended June 30, 2024:

	Shares			Weighted Average Grant Date Fair Value
Balance at January 1, 2024		4,555,099		$	4.35
Granted		2,674,001			3.54
Vested		(1,272,842	)		4.36
Forfeited/Cancelled		(428,852	)		4.12
Balance at June 30, 2024		5,527,406		$	3.98

Schedule of Assumptions Used to Determine the Fair Value of Purchase Rights Issued Under ESPP

The assumptions that the Company used to determine the fair value of the purchase rights issued to employees were as follows:

	Six Months Ended June 30,
	2024	2023
Risk-free interest rate	5.4%	5.0%
Expected volatility	95.3%	73.2%
Expected term (years)	0.5	0.5
Dividend yield	—	—

Schedule of Stock-Based Compensation Expense

The Company recorded total stock-based compensation expense related to stock options, RSUs and the ESPP in the following expense categories of the accompanying condensed consolidated statements of operations and comprehensive income (loss) (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	3,161	$	3,412	$	6,168	$	6,161
General and administrative		4,468		2,062		6,844		6,793
Total stock-based compensation expense	$	7,629	$	5,474	$	13,012	$	12,954