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License, Clinical Trial and Sponsored Research Agreements (Other - Sponsored Research and Clinical Trial Agreements) (Narrative) (Details) - USD ($) $ in Thousands |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Sep. 08, 2021 | Jul. 03, 2017 | Oct. 31, 2022 | Jan. 31, 2022 | Jun. 30, 2021 | Nov. 30, 2020 | Jun. 30, 2020 | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023 | Dec. 31, 2022
License, Clinical Trial and Sponsored Research Agreements |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  | $ 57 | $ 9,527 | $ 8,221 | $ 34,363 | $ 40,513 | $ 62,475
Sponsored research and clinical trial agreements |  |  |  |  |  |  |  |  |  |  |  |  |
License, Clinical Trial and Sponsored Research Agreements |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  |  |  |  |  | 4,162 | 6,989
Fred Hutchinson Cancer Center | Sponsored research and clinical trial agreements | CD20 (MB-106) |  |  |  |  |  |  |  |  |  |  |  |  |
License, Clinical Trial and Sponsored Research Agreements |  |  |  |  |  |  |  |  |  |  |  |  |
Milestones payable |  | $ 5,300 |  |  |  |  |  |  |  |  |  |  |
Additional milestone payments |  |  |  | $ 2,200 |  | $ 1,800 |  |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  |  |  |  |  | 1,254 | 1,987
Fred Hutchinson Cancer Center | Clinical Trial Agreement | CD20 (MB-106) |  |  |  |  |  |  |  |  |  |  |  |  |
License, Clinical Trial and Sponsored Research Agreements |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  |  |  |  |  | 1,300 | 2,000
St. Jude Children's Research Hospital | Sponsored research and clinical trial agreements | ST. Jude - XSCID |  |  |  |  |  |  |  |  |  |  |  |  |
License, Clinical Trial and Sponsored Research Agreements |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  |  |  |  |  | 637 | 508
St. Jude Children's Research Hospital | Data Transfer Agreement | ST. Jude - XSCID |  |  |  |  |  |  |  |  |  |  |  |  |
License, Clinical Trial and Sponsored Research Agreements |  |  |  |  |  |  |  |  |  |  |  |  |
Upfront fees paid |  |  |  |  |  |  | $ 1,100 |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  |  |  |  |  | 600 | 500
Mayo Clinic | Sponsored research and clinical trial agreements |  |  |  |  |  |  |  |  |  |  |  |  |
License, Clinical Trial and Sponsored Research Agreements |  |  |  |  |  |  |  |  |  |  |  |  |
Milestones payable |  |  |  |  | $ 2,100 |  |  |  |  |  |  |  |
Additional milestone payments |  |  | $ 100 |  |  |  |  |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  |  |  |  |  | 551 | 968
Agreement term |  |  |  |  | 2 years |  |  |  |  |  |  |  |
Leiden University Medical Center | Sponsored research and clinical trial agreements | RAG1 SCID (MB-110) |  |  |  |  |  |  |  |  |  |  |  |  |
License, Clinical Trial and Sponsored Research Agreements |  |  |  |  |  |  |  |  |  |  |  |  |
Milestones payable | $ 500 |  |  |  |  |  |  |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  |  |  |  |  | $ 350 | $ 505
Agreement term | 5 years |  |  |  |  |  |  |  |  |  |  |  |

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