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Stock-based compensation (Tables)
 6 Months Ended
Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]  
Schedule of Stock Option Activity Under Plan A summary of stock option activity is as follows:
Number
of Shares		Weighted-
Average
Exercise Price
Outstanding at January 1, 202310,051,283 $9.84 
Granted2,864,451 $6.11 
Exercised(97,596)$4.37 
Cancelled(458,953)$11.15 
Outstanding at June 30, 202312,359,185 $8.97 
Exercisable at June 30, 20236,591,352 $9.21 
Schedule of Restricted Stock Activity A summary of the RSU activity is as follows:
Number of Shares
Unvested at January 1, 20231,870,791 
Granted2,380,136 
Vested(460,981)
Forfeited(118,793)
Unvested at June 30, 20233,671,153 
Schedule of Stock-Based Compensation Expense by Award Type The following table presents stock-based compensation expense by award type included within the Company’s condensed consolidated statements of operations and comprehensive loss:
Three Months Ended June 30,Six Months Ended June 30,
(in thousands)2023202220232022
Stock options$4,288 $3,933 $8,507 $8,051 
Restricted stock units2,060 1,258 3,953 2,467 
Employee stock purchase plan295 157 590 315 
Stock-based compensation expense included in total operating expenses$6,643 $5,348 $13,050 $10,833 
Schedule of Stock-Based Compensation Expense as Reflected in the Company's Condensed Consolidated Statements of Operations and Comprehensive Loss The following table presents stock-based compensation expense as reflected in the Company’s condensed consolidated statements of operations and comprehensive loss:
Three Months Ended June 30,Six Months Ended June 30,
(in thousands)2023202220232022
Research and development$3,396 $2,746 $6,728 $5,679 
General and administrative3,247 2,602 6,322 5,154 
Stock-based compensation expense included in total operating expenses$6,643 $5,348 $13,050 $10,833 
Schedule of Weighted Average Assumptions for Estimating Fair Value of Option Awards The fair value of each option award is estimated on the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions:
Three Months Ended
June 30,		Six Months Ended June 30,
2023202220232022
Risk-free interest rate3.7 %2.9 %3.6 %2.0 %
Expected dividend yield— %— %— %— %
Expected term (years)5.845.846.045.99
Expected stock price volatility100 %90 %99 %87 %