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Share-Based Compensation | 3 Months Ended
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Mar. 31, 2025
Share-Based Compensation |
Share-Based Compensation | 5. Share-Based Compensation Equity Incentive Plans The Company’s 2018 Incentive Award Plan and 2016 Equity Incentive Plan (collectively, the “Plans”) were adopted by the Company’s board of directors and shareholders. Under the Plans, the Company has granted share options and restricted share units (“RSUs”) to selected officers, employees, non-employee members of the board of directors and non-employee consultants. The Company’s board of directors or a committee thereof administers the Plans. Upon the adoption of the 2018 Incentive Award Plan, the Company ceased issuing awards under the 2016 Equity Incentive Plan. Options ​ A summary of the Company’s share option activity related to employees, non-employee members of the board of directors and non-employee consultants as of December 31, 2024 and for the three-month period ended March 31, 2025 is as follows (in thousands, except share and per share amounts): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Weighted- | ​
​ | ​ |  | ​ |  | Weighted- |  | ​ | Average | ​
​ | ​ | ​ | ​ | ​ | Average | ​ | ​ | Remaining | ​
​ | ​ | ​ | Number of | ​ | Exercise | ​ | ​ | Contractual | ​
​ | ​ | ​ | Options | ​ | Price | ​ | ​ | Term (years) | ​
Outstanding at December 31, 2024 | ​ |  | 8,232,587 | ​ | $ | 12.57 |  | ​ | 5.35 | years
Granted | ​ |  | — | ​ | $ | — |  | ​ | ​ | ​
Exercised | ​ |  | (638) | ​ | $ | 5.73 |  | ​ | ​ | ​
Forfeited | ​ |  | (208,960) | ​ | $ | 16.39 |  | ​ | ​ | ​
Outstanding at March 31, 2025 | ​ |  | 8,022,989 | ​ | $ | 12.48 | ​ | ​ | 5.18 | years
Options exercisable at March 31, 2025 | ​ |  | 6,956,612 | ​ | $ | 12.85 | ​ |  | 4.79 | years
Options vested and expected to vest at March 31, 2025 | ​ | ​ | 8,022,989 | ​ | $ | 12.48 | ​ | ​ | 5.18 | years
Aggregate intrinsic value of options outstanding as of March 31, 2025 | ​ | $ | 2,228 | ​ |  |  | ​ |  |  | ​
Aggregate intrinsic value of options exercisable as of March 31, 2025 | ​ | $ | 2,079 | ​ |  |  | ​ |  |  | ​
​ Options granted under the Plans have a maximum contractual term of ten years. Options granted generally vest 25% on the first anniversary of the date of grant and the balance ratably over the next 36 months. Options granted to directors when they join the board generally vest in 36 equal monthly installments following the date of grant, and annual options granted to directors generally vest on the earlier of the first anniversary of the date of grant or the day before the Company’s annual meeting of shareholders after the date of grant. The Company recorded the following share-based compensation expense in connection with the options for the three-month periods ended March 31, 2025 and 2024 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three-Month Periods Ended March 31,
​ |  | 2025 |  | 2024
Research and development | ​ | $ | 939 | ​ | $ | 1,635
General and administrative | ​ | ​ | 597 | ​ | ​ | 1,053
Total share-based compensation | ​ | $ | 1,536 | ​ | $ | 2,688
​ The total fair value of options vested during the three-month periods ended March 31, 2025 and 2024 was $2.0 million and $4.3 million, respectively. There were no options granted during the three-month period ended March 31, 2025. The weighted-average grant date fair value of options granted during the three-month period ended March 31, 2024 was $3.91 per share. The grant date fair values of the share options granted were estimated using the Black-Scholes option valuation model with the following ranges of assumptions: ​
​ | ​ | ​ | ​ | ​
​ |  | 2025 |  | 2024
Risk-free interest rate |  | - |  | 4.04 - 4.17%
Expected volatility |  | - |  | 67%
Expected dividend yield |  | - |  | 0%
Expected term (in years) |  | - |  | 3.6 - 6.1
​ As of March 31, 2025, the total compensation expense relating to unvested options granted that had not yet been recognized was $6.8 million, which is expected to be realized over a period of 2.9 years. The Company will issue shares upon exercise of options from ordinary shares reserved under the Plans. Restricted Share Units A summary of the Company’s RSU activity related to employees, non-employee members of the board of directors and non-employee consultants as of December 31, 2024 and for the three-month period ended March 31, 2025 is as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ |  | ​ |  | Weighted-
​ | ​ | Number of | ​ | Average
​ | ​ | Restricted | ​ | Grant Date
​ | ​ | Share Units | ​ | Fair Value
Outstanding at December 31, 2024 | ​ |  | 4,252,250 | ​ | $ | 8.91
Granted | ​ |  | — | ​ | $ | —
Vested | ​ | ​ | (862,500) | ​ | $ | 13.70
Forfeited | ​ | ​ | — | ​ | $ | —
Outstanding at March 31, 2025 | ​ |  | 3,389,750 | ​ | $ | 7.69
​ RSUs granted generally vest 50% on the second anniversary of the date of grant and 25% on the third and fourth anniversaries of the date of grant. Annual RSUs granted to directors generally vest in a single installment on the earliest to occur of the first anniversary of the grant date or the day immediately prior to the date of the next annual meeting of the Company’s shareholders occurring after the date of grant. The RSUs granted to the directors in June 2021 will be paid on or within 30 days after the date a director ceases to serve on the board. For RSUs granted in June 2022 and future years, the directors may annually elect whether to defer the payment of their annual RSU awards under the Deferred Compensation Plan for Non-Employee Directors, which was adopted by the board on December 17, 2021. As of March 31, 2025, there were 272,500 vested shares that have been deferred. The related share-based compensation expense, which is recognized ratably over the requisite service period, is included in general and administrative and research and development expenses, as applicable, in the condensed consolidated statements of operations and comprehensive loss. The Company recorded the following share-based compensation expense in connection with the RSUs for the three-month periods ended March 31, 2025 and 2024 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three-Month Periods Ended March 31,
​ |  | 2025 |  | 2024
Research and development | ​ | $ | 1,107 | ​ | $ | 1,240
General and administrative | ​ | ​ | 2,244 | ​ | ​ | 3,032
Total share-based compensation | ​ | $ | 3,351 | ​ | $ | 4,272
​ As of March 31, 2025, the total compensation expense relating to unvested RSUs granted that had not yet been recognized was $18.5 million, which is expected to be realized over a period of 3.1 years. To satisfy employee minimum statutory tax withholding requirements for restricted share units that vest, the Company withholds a portion of the vesting ordinary shares. During the three months ended March 31, 2025 and 2024, the Company withheld 405,459 and 348,652 ordinary shares with a total value of approximately $2.8 million and $2.2 million, respectively. These amounts are presented as a cash outflow from financing activities in the accompanying condensed consolidated statement of cash flows. During the three-month periods ended March 31, 2025 and 2024, the Company recognized total share-based compensation expense in the accompanying condensed consolidated statements of operations and comprehensive loss as follows (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three-Month Periods Ended March 31,
​ |  | 2025 |  | 2024
Research and development | ​ | $ | 2,046 | ​ | $ | 2,875
General and administrative | ​ |  | 2,841 | ​ | ​ | 4,085
Total share-based compensation | ​ | $ | 4,887 | ​ | $ | 6,960
​ The Company does not expect to realize any tax benefits from its share option activity or the recognition of share-based compensation expense because the Company currently has net operating losses and has a full valuation allowance against its deferred tax assets. Accordingly, no amounts related to excess tax benefits have been reported in cash flows from operations or cash flows from financing activities for the three-month periods ended March 31, 2025 and 2024.

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