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Stock-based compensation
 9 Months Ended
Sep. 30, 2025
Share-Based Payment Arrangement [Abstract]  
Stock-based compensation Stock-based compensation
The Company grants stock options, restricted stock units, and stock appreciation rights (“SARs”) under the 2021 Stock Option and Incentive Plan (“2021 Plan”) and the 2023 Inducement Plan (the “2023 Inducement Plan”). On January 1, 2025, the number of shares of common stock reserved for future issuance under the 2021 Plan was increased by 5,768,113 shares pursuant to an automatic annual increase. As of September 30, 2025, 5,483,484 shares were available for future grant under the 2021 Plan. As of September 30, 2025, 1,724,200 shares were available for future grant under the 2023 Inducement Plan.
Total stock-based compensation expense related to all of the Company’s stock-based awards was recorded in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands):
For the Three Months Ended September 30,For the Nine Months Ended September 30,
2025202420252024
Research and development1,982 2,010 $6,020 $5,577 
Selling, general and administrative2,414 3,498 8,073 8,824 
Total stock-based compensation expense$4,396 $5,508 $14,093 $14,401 
Stock options
Activity for stock options is shown below:
Number of OptionsWeighted Average Exercise Price per ShareWeighted Average Remaining Contractual Term (in years)Aggregate Intrinsic Value (in thousands $)
Outstanding at December 31, 202419,177,571 $3.39 7.6$7,317 
Granted6,512,400 3.16 
Exercised(864,563)2.26 1,738
Canceled/Forfeited(2,293,910)3.05 
Expired(626,082)7.33 
Outstanding at September 30, 202521,905,416 3.29 7.7$9,804 
Exercisable at September 30, 202510,105,606 $3.41 6.6$6,621 
As of September 30, 2025, total unrecognized stock-based compensation related to stock options was $22.0 million, which the Company expects to recognize over a remaining weighted average period of 2.1 years.
Determination of fair value
The estimated grant-date fair value of all the Company’s stock options was calculated using the Black-Scholes option pricing model, based on the following assumptions:
For the Three Months Ended September 30,For the Nine Months Ended September 30,
2025202420252024
Expected term (in years)
5.8-6.1
6.0-6.1
5.5-6.1
5.5-6.1
Volatility
91%-91%
82%-84%
90%-92%
81%-84%
Risk-free interest rate
3.8%-4.0%
3.7%-4.4%
3.8%-4.4%
3.7%-4.6%
Dividend Yield—%—%—%—%
Restricted stock units
Activity for restricted stock units is shown below:
Number of SharesWeighted Average Grant Date Fair Value
Unvested as of December 31, 20243,711,710 $3.12 
Granted1,667,362 3.19 
Vested(469,008)3.93 
Forfeitures(489,704)2.56 
Unvested as of September 30, 20254,420,360 $3.12 
As of September 30, 2025, there was $5.9 million of unrecognized compensation expense related to the outstanding restricted stock units expected to be recognized over a remaining weighted-average period of 1.9 years.