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Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Tables) | 3 Months Ended
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Mar. 31, 2025
Summary of Significant Accounting Policies and Recent Accounting Pronouncements |
Schedule of Restricted Cash | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | March 31, | ​ | December 31,
​ | ​ | 2025 | ​ | 2024
Cash and cash equivalents |  | $ | 66,523 |  | $ | 103,659
Restricted cash | ​ |  | 2,087 | ​ |  | 2,009
Total cash, cash equivalents and restricted cash in the condensed consolidated statement of cash flows | ​ | $ | 68,610 | ​ | $ | 105,668
Schedule of Financial Assets and Liabilities Measured at Fair Value | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Fair Value Measurement Using:
​ |  | ​ | ​ |  | Significant |  | Significant Other |  | Significant
​ | ​ | March 31, | ​ | Observable Inputs | ​ | Observable Inputs | ​ | Unobservable
Description | ​ | 2025 | ​ | (Level 1) | ​ | (Level 2) | ​ | (Level 3)
Cash equivalents | ​ | $ | 57,020 | ​ | $ | 57,020 | ​ | $ | — | ​ | $ | —
Restricted cash | ​ | $ | 2,087 | ​ | $ | 2,087 | ​ | $ | — | ​ | $ | —
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Fair Value Measurement Using:
​ |  | ​ | ​ |  | Significant |  | Significant Other |  | Significant
​ | ​ | December 31, | ​ | Observable Inputs | ​ | Observable Inputs | ​ | Unobservable
Description | ​ | 2024 | ​ | (Level 1) | ​ | (Level 2) | ​ | (Level 3)
Cash equivalents | ​ | $ | 80,930 | ​ | $ | 80,930 | ​ | $ | — | ​ | $ | —
Restricted cash | ​ | $ | 2,009 | ​ | $ | 2,009 | ​ | $ | — | ​ | $ | —
Schedule of Change in Asset Retirement Obligations | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the Three-Month Periods Ended March 31,
​ | ​ | 2025 | ​ | 2024
Balance at beginning of period |  | $ | 2,821 |  | $ | 2,401
Change in estimate | ​ | ​ | (1,576) | ​ | ​ | —
Amortization of interest | ​ |  | 63 | ​ |  | 48
Effects of exchange rate changes | ​ |  | 36 | ​ |  | (9)
Balance at end of period | ​ | $ | 1,344 | ​ | $ | 2,440
Schedule of Securities Excluded from Computation of Diluted Net Loss per Share | ​
​ | ​ | ​ | ​ | ​
​ |  | March 31, |  | March 31,
​ |  | 2025 |  | 2024
Share options |  | 8,022,989 |  | 8,484,644
Restricted share units | ​ | 3,389,750 | ​ | 4,094,750
Deferred share units | ​ | — | ​ | 185,000
Warrants | ​ | 700,000 | ​ | 700,000
​ |  | 12,112,739 |  | 13,464,394
Schedule of net loss for the segment | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the Three-Month Periods Ended March 31,
​ | ​ | 2025 | ​ | 2024
Service revenue - related party |  | $ | 1,926 |  | $ | 697
Operating expenses: | ​ | ​ | ​ | ​ | ​ | ​
Cost of service revenue - related party | ​ | ​ | 1,378 | ​ | ​ | —
General and administrative | ​ |  | 6,348 | ​ |  | 8,864
Clinical programs: | ​ | ​ | ​ | ​ | ​ | ​
Botaretigene sparoparvovec | ​ | ​ | — | ​ | ​ | 3,957
AAV-hAQP1 | ​ | ​ | 4,852 | ​ | ​ | 1,663
AAV-CNGB3 / AAV-CNGA3 | ​ | ​ | — | ​ | ​ | (1,179)
AAV-GAD | ​ | ​ | 1,459 | ​ | ​ | 2,170
Other ocular diseases | ​ | ​ | 1,445 | ​ | ​ | 293
Manufacturing | ​ | ​ | 17,359 | ​ | ​ | 18,360
Preclinical programs: | ​ | ​ | ​ | ​ | ​ | ​
Gene regulation | ​ | ​ | 2,286 | ​ | ​ | 2,499
Neurodegenerative diseases | ​ | ​ | 426 | ​ | ​ | 391
Preclinical ocular diseases | ​ | ​ | 625 | ​ | ​ | 327
Other research and development1 | ​ | ​ | (624) | ​ | ​ | 541
Johnson & Johnson Innovative Medicine reimbursement | ​ | ​ | — | ​ | ​ | (652)
Share-based compensation | ​ | ​ | 4,887 | ​ | ​ | 6,960
Depreciation and amortization | ​ | ​ | 3,081 | ​ | ​ | 3,275
Total operating expenses | ​ | ​ | 43,522 | ​ | ​ | 47,469
Other segment items2 | ​ | ​ | 1,615 | ​ | ​ | 26,330
Segment net loss | ​ | $ | (39,981) | ​ | ​ | (20,442)
Adjustments or reconciling items | ​ | ​ | — | ​ | ​ | —
Net loss | ​ | $ | (39,981) | ​ | $ | (20,442)
​ 1 Other research and development is comprised of all other costs including payroll and payroll related costs, travel, rent and facilities costs and other non-program specific expenses. 2 Other segment items is comprised of foreign currency gain (loss), interest income, interest expense and gain on sale of nonfinancial assets.
Schedule of Long-lived Assets by Geographical Area | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | March 31, |  | December 31,
​ | ​ | 2025 | ​ | 2024
United States | ​ | $ | 2,515 | ​ | $ | 7,209
United Kingdom | ​ |  | 28,255 | ​ |  | 28,419
European Union | ​ | ​ | 103,487 | ​ | ​ | 100,845
​ | ​ | $ | 134,257 | ​ | $ | 136,473

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