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Share-Based Compensation (Tables)
 12 Months Ended
Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]  
Summary of Share-Based Compensation Expense
The following table summarizes share-based compensation expense for the periods presented (in thousands):
Year Ended 
December 31,
202320222021
Research and development$19,211 $14,805 $9,514 
General and administrative21,703 16,517 15,144 
Total share-based compensation expense$40,914 $31,322 $24,658 
Fair Value of Options Granted
With the exception of the options granted on February 12, 2021 pursuant to an option exchange program, where no incremental share-based compensation expense was recognized, the fair value of the options granted to employees and non-employee directors during the years ended December 31, 2023, 2022 and 2021, respectively was estimated as of the grant date using the Black-Scholes option-pricing model assuming the weighted-average assumptions listed in the following table:
Year Ended 
December 31,
202320222021
Expected volatility81.2 %82.4 %81.7 %
Risk-free interest rate4.2 %2.2 %1.0 %
Expected dividend yield— %— %— %
Expected life (in years)4.86.06.0
Weighted average grant date fair value$37.32$23.43$21.39
Summary of Company's Share Option Activity
The following table summarizes the Company’s stock option activity during the year ended December 31, 2023:
OptionsWeighted
Average
Exercise
Price		Weighted
Average
Remaining
Contractual
Term (years)		Aggregate
Intrinsic
Value
(in thousands)
Outstanding at December 31, 2022
9,479,998 $23.16 6.82$354,856 
Granted
1,790,621 56.48 
Exercised(1,135,302)18.90 
Forfeited(246,064)44.28 
Expired(22,916)70.74 
Outstanding at December 31, 2023
9,866,337 $29.06 6.60$118,447 
Vested and expected to vest at December 31, 2023
9,558,866 $28.49 6.53$117,705 
Vested at December 31, 2023
6,371,511 $20.75 5.54$105,546 
Summary of RSU Activity
The following table summarizes the activity and related information for RSUs during the year ended December 31, 2023:
Number of UnitsWeighted Average
Grant-Date
Fair Value		Weighted
Average
Remaining
Contractual
Term (years)		Aggregate
Intrinsic
Value
(in thousands)
Unvested at December 31, 2022
23,000 $60.89 1.67$1,386 
Units Granted
8,000 51.80 
Units Vested(5,750)60.89 
Units Forfeited— — 
Unvested at December 31, 2023
25,250 $58.01 1.09$918 
Unvested and expected to vest at December 31, 2023
23,066 $58.19 1.08$838