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Stock award plan | 9 Months Ended
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Sep. 30, 2025
Stock award plan |
Stock award plan | 8. Stock award plan In May 2013, the Company’s Board of Directors and stockholders approved the 2013 Long-Term Incentive Plan, which became effective upon the closing of the Company’s initial public offering. On June 8, 2022 (the “Restatement Effective Date”), the Company’s stockholders approved the Amended and Restated 2013 Long-Term Incentive Plan (the “Amended 2013 LTIP”). The Amended 2013 LTIP provides for the grant of incentive stock options, nonstatutory stock options, restricted stock units and other stock-based awards. The number of shares of common stock reserved for issuance under the Amended 2013 LTIP is the sum of (A) the number of shares of the Company’s common stock (up to 16,724,212 shares) that is equal to the sum of (1) the number of shares issued under the 2013 Long-Term Incentive Plan prior to the Restatement Effective Date, (2) the number of shares that remain available for issuance under the 2013 Long-Term Incentive Plan immediately prior to the Restatement Effective Date and (3) the number of shares subject to awards granted under the 2013 Long-Term Incentive Plan prior to the Restatement Effective Date that are outstanding as of the Restatement Effective Date, plus (B) from and after the Restatement Effective Date, an additional 8,475,000 shares of Common Stock. As of September 30, 2025, awards for 5,204,816 shares of common stock are available for issuance under the Amended 2013 LTIP. In January 2020, the Company’s Board of Directors approved the 2020 Inducement Stock Incentive Plan. The 2020 Inducement Stock Incentive Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards and other stock-based awards for, initially, up to at the time, an aggregate of 1,000,000 shares of common stock. Any grants made under the 2020 Inducement Stock Incentive Plan must be made pursuant to the Nasdaq Listing Rule 5635(c)(4) inducement grant exception as a material component of the Company’s new hires’ employment compensation. In December 2020, the Company’s Board of Directors approved an additional 1,000,000 shares of common stock that may be issued under the 2020 Inducement Stock Incentive Plan. In April 2022, the Company’s Board of Directors approved a reduction in the total number of shares of common stock that may be issued under the 2020 Inducement Stock Incentive Plan to 1,300,000 shares. In December 2022, the Company’s Board of Directors approved an additional 1,700,000 shares of common stock that may be issued under the 2020 Inducement Stock Incentive Plan. As of September 30, 2025, awards for 1,802,161 shares of common stock were available for issuance under the 2020 Inducement Stock Incentive Plan. The Board of Directors has the authority to select the individuals to whom options are granted and determine the terms of each option, including (i) the number of shares of common stock subject to the option; (ii) the date on which the option becomes exercisable; (iii) the option exercise price, which, in the case of incentive stock options, must be at least 100% (110% in the case of incentive stock options granted to a stockholder owning in excess of 10% of the Company’s stock) of the fair market value of the common stock as of the date of grant; and (iv) the duration of the option (which, in the case of incentive stock options, may not exceed ten years). Options typically vest over a four-year period. Inducement stock option awards From January 1, 2025 through September 30, 2025, the Company issued a total of 841,945 stock options to various employees. Of those, 51,200 were inducement grants for non-statutory stock options, all of which were made pursuant to the 2020 Inducement Stock Incentive Plan. ​ Stock option activity—A summary of stock option activity is as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Weighted- |  |  | ​ | ​
​ | ​ | ​ | ​ | Weighted- | ​ | average | ​ | ​ | Aggregate
​ | ​ | ​ | ​ | average | ​ | remaining | ​ | ​ | intrinsic
​ | ​ | Number of | ​ | exercise | ​ | contractual | ​ | ​ | value(in
​ | ​ | options | ​ | price | ​ | term | ​ | ​ | thousands)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |  | ​ | ​ | ​
Outstanding at December 31, 2024 |  | 8,482,489 | ​ | $ | 42.29 |  |  |  | ​ | ​ |
Granted |  | 841,945 | ​ | $ | 47.12 |  |  |  | ​ | ​ |
Exercised |  | (953,414) | ​ | $ | 35.75 |  |  |  | ​ | ​ |
Forfeited/Cancelled |  | (564,709) | ​ | $ | 53.91 |  |  |  | ​ | ​ |
Outstanding at September 30, 2025 |  | 7,806,311 | ​ | $ | 42.77 |  | 5.66 | years | ​ | $ | 151,190
Expected to vest at September 30, 2025 |  | 1,524,459 | ​ | $ | 39.30 |  | 8.53 | years | ​ | $ | 33,651
Exercisable at September 30, 2025 |  | 6,126,727 | ​ | $ | 43.71 |  | 4.86 | years | ​ | $ | 114,211
​ The fair value of grants made in the nine months ended September 30, 2025, was contemporaneously estimated on the date of grant using the following assumptions: ​
​ | ​ | ​ | ​
​ |  | Nine months ended |
​ |  | September 30, 2025 |
Risk-free interest rate |  | 3.81% - 4.44% |
Expected volatility |  | 55% - 56% |
Expected term |  | 5.5 years |
​ The Company assumed no expected dividends for all grants. The weighted average grant date fair value of options granted during the nine months ended September 30, 2025 was $25.44 per share. The expected term of options was estimated based on the Company’s historical exercise data and the expected volatility of options was estimated based on the Company’s historical stock volatility. The risk-free rate of the options was based on U.S. Government Securities Treasury Constant Maturities yields at the date of grant for a term similar to the expected term of the option. Restricted Stock Units—Restricted stock units are granted subject to certain restrictions, including in some cases service or time conditions (restricted stock). The grant-date fair value of restricted stock units, which have been determined based upon the market value of the Company’s shares on the grant date, are expensed over the vesting period. From January 1, 2025, through September 30, 2025, the Company issued a total of 1,615,305 restricted stock units to various employees. Of those, 107,050 were inducement grants for restricted stock units, all of which were made pursuant to the 2020 Inducement Stock Incentive Plan. The following table summarizes information on the Company’s restricted stock units, including performance-based restricted stock units (“PSUs”) for which the performance conditions were satisfied: ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Restricted Stock Units
​ | ​ | ​ | ​ | Weighted
​ | ​ | ​ | ​ | Average
​ | ​ | ​ | ​ | Grant
​ | ​ | Number of | ​ | Date
​ |  | Shares |  | Fair Value
Unvested at December 31, 2024 | ​ | 3,527,575 | ​ | $ | 33.39
Granted |  | 1,615,305 | ​ | ​ | 47.16
PSUs with conditions satisfied |  | 75,000 | ​ | ​ | 28.58
Vested | ​ | (1,201,681) | ​ | ​ | 36.79
Forfeited |  | (227,396) | ​ | ​ | 35.27
Unvested at September 30, 2025 |  | 3,788,803 | ​ | $ | 37.98
​ Performance-based Restricted Stock Units—In December 2023, the Company granted 150,000 PSUs to its Chief Executive Officer, Dr. Matthew Klein, which will vest only if certain regulatory milestones are achieved over an approximately two-year performance period. In December 2024, the Company granted 25,000 PSUs to Dr. Matthew Klein, which will vest only if challenging performance goals relating to development, regulatory, or commercial goals are achieved over an approximately five-year performance period. An additional 31,250 PSUs with market conditions were granted to Dr. Matthew Klein in December 2024. During the quarter ended September 30, 2025, the performance conditions for 75,000 of these PSUs granted to Dr. Klein in December 2023 were satisfied due to the Company’s achievement of a regulatory milestone and are included in the restricted stock units table above. The expense related to these PSUs was $1.0 million for the three and nine months ended September 30, 2025. The achievement of the remaining performance goals for the PSU’s granted to Dr. Klein has not yet been deemed probable and therefore no expense has been recognized to date. The expense related to the PSUs with market conditions was $0.1 million and $0.5 million for the three and nine months ended September 30, 2025, respectively. The following table summarizes information regarding the Company’s PSUs: ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Performance-based Restricted Stock Units
​ |  | Performance based |  | Market Conditions | ​ | Total
Total PSUs granted for which the performance or market conditions were not yet satisfied at December 31, 2024 | ​ | 175,000 | ​ | 31,250 | ​ | 206,250
PSUs with performance or market conditions satisfied during the period |  | (75,000) | ​ | — | ​ | (75,000)
Total PSUs granted for which the performance or market conditions were not yet satisfied at September 30, 2025 |  | 100,000 | ​ | 31,250 | ​ | 131,250
​ Employee Stock Purchase Plan—In June 2016, the Company established an Employee Stock Purchase Plan (as amended, the “ESPP” or the “Plan”), for certain eligible employees. The Plan is administered by the Company’s Board of Directors or a committee appointed by the Company’s Board of Directors. In June 2021, the Plan was amended to increase the total number of shares available for purchase under the Plan from one million shares to two million shares of the Company’s common stock. Employees may participate over a six month period through payroll withholdings and may purchase, at the end of the six month period, the Company’s common stock at a purchase price of at least 85% of the closing price of a share of the Company’s common stock on the first business day of the offering period or the closing price of a share of the Company’s common stock on the last business day of the offering period, whichever is lower. No participant will be granted a right to purchase the Company’s common stock under the Plan if such participant would own more than 5% of the total combined voting power of the Company or any subsidiary of the Company after such purchase. For the three and nine months ended September 30, 2025, the Company recorded $0.6 million and $1.6 million, respectively, in compensation expense related to the ESPP. The Company recorded share-based compensation expense in the statement of operations related to incentive stock options, nonstatutory stock options, restricted stock units, performance-based restricted stock units and the ESPP as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended September 30, | ​ | Nine Months Ended September 30,
​ |  | 2025 |  | 2024 |  | 2025 |  | 2024
Research and development | ​ | $ | 9,133 | ​ | $ | 9,416 | ​ | $ | 26,827 | ​ | $ | 27,810
Selling, general and administrative | ​ |  | 10,293 | ​ |  | 10,339 | ​ |  | 29,202 | ​ |  | 29,566
Total | ​ | $ | 19,426 | ​ | $ | 19,755 | ​ | $ | 56,029 | ​ | $ | 57,376
​ As of September 30, 2025, there was approximately $137.2 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the Company’s equity award plans. This cost is expected to be recognized as share-based compensation expense over the weighted average remaining service period of approximately 2.7 years.

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