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Clinical Trial and Sponsored Research Agreements (Tables) | 9 Months Ended | 12 Months Ended
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Sep. 30, 2024 | Dec. 31, 2023
License agreements |  |
License, Clinical Trial and Sponsored Research Agreements |  |
Schedule of Clinical Trial and Sponsored Research Agreements |  | For the years ended December 31, 2023 and 2022, the Company recorded the following expense in research and development for licenses acquired: ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the year ended December 31,
($ in thousands) |  | 2023 |  | 2022
City of Hope National Medical Center | ​ | ​ | ​ | ​ | ​ | ​
IV/ICV | ​ | ​ | — | ​ | ​ | 125
HER2 | ​ | ​ | — | ​ | ​ | 200
CSL Behring (Calimmune) | ​ | ​ | 50 | ​ | ​ | 40
Fortress Annual Stock Dividend | ​ | ​ | 477 | ​ | ​ | 1,109
Total | ​ | $ | 527 | ​ | $ | 1,474
Clinical trial and sponsored research agreements |  |
License, Clinical Trial and Sponsored Research Agreements |  |
Schedule of Clinical Trial and Sponsored Research Agreements | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the three months ended September 30, | ​ | For the nine months ended September 30,
($ in thousands) |  | 2024 |  | 2023 |  | 2024 |  | 2023
City of Hope National Medical Center | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
CD123 | ​ | $ | — | ​ | $ | 23 | ​ | $ | — | ​ | $ | 23
IL13Rα2 | ​ | ​ | 66 | ​ | ​ | 180 | ​ | ​ | 457 | ​ | ​ | 817
CS1(1) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 188
PSCA(1) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 44
Fred Hutchinson Cancer Center - CD20 | ​ | ​ | — | ​ | ​ | 142 | ​ | ​ | 312 | ​ | ​ | 1,239
St. Jude Children’s Research Hospital - XSCID(2) | ​ | ​ | — | ​ | ​ | (106) | ​ | ​ | (434) | ​ | ​ | 528
Leiden University Medical Center - RAG1 SCID | ​ | ​ | — | ​ | ​ | 125 | ​ | ​ | 241 | ​ | ​ | 349
Mayo Clinic(3) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (275) | ​ | ​ | 551
Total | ​ | $ | 66 | ​ | $ | 364 | ​ | $ | 301 | ​ | $ | 3,739
(1) Licenses and associated sponsored research agreements were terminated in May 2023. (2) License and associated Data Transfer Agreement were terminated in April 2024. (3) License and associated sponsored research agreement were terminated in June 2024. |

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