Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of stock option activity

The following table summarizes stock option activity during the year ended December 31, 2023:

	Shares	Weighted average exercise price		Weighted average remaining contractual life (years)	Aggregate intrinsic value (in thousands)
Outstanding at January 1, 2023	2,857,054	$	81.78
Options granted	31,111	190.91
Options exercised	(460,385)	88.83
Options cancelled	(72,001)	144.24
Outstanding at December 31, 2023	2,355,779	$	79.94	5.51	$	359,861
Exercisable at December 31, 2023	1,774,976	$	74.49	4.71	$	281,400

Stock-based compensation expense during the years ended December 31, 2023, 2022 and 2021 was as follows (in thousands):

	Year Ended December 31,
	2023		2022		2021
Stock-based compensation expense by type of award:
Stock options	$	30,613	$	31,625	$	26,873
Restricted stock units	14,974		—		—
Performance-based restricted stock units	4,148		—		—
Total stock-based compensation expense	$	49,735	$	31,625	$	26,873
Effect of stock-based compensation expense by line item:
Research and development	$	20,864	$	13,876	$	10,698
General and administrative	28,871		17,749		16,175
Total stock-based compensation expense included in net loss	$	49,735	$	31,625	$	26,873

Summary of restricted stock unit activity

The following table summarizes RSU activity, excluding performance-based RSUs, during the year ended December 31, 2023:

	Shares	Weighted average grant date fair value
Unvested at January 1, 2023	—	$	—
RSUs granted	398,600	243.81
RSUs vested	(356)	299.98
RSUs forfeited	(22,127)	283.05
Unvested at December 31, 2023	376,117	$	241.45