Base Editing Hematopoietic Stem Cell and T Cell Gene Therapy for CD40L-HyperIgM Syndrome: Single Patient Study

Background: X-linked hyper-IgM (HIGM) syndrome is caused by a mutation in the CD40 ligand (CD40L) gene. People with this disease have white blood cells that do not work properly. These people are at risk of severe infections and autoimmune diseases. Researchers want to know if these base-edited stem cells and T cells can help people with CD40L-HIGM syndrome. Objective: To test base-edited stem cells and base-edited T cells in 1 person with CD40L-HIGM syndrome. Eligibility: A single male with CD40L-HIGM syndrome. Design: A single participant is planned to receive a single dose of edited stem cells and supportive treatment with edited T cells. Participant stem and T cells will undergo base editing to repair the mutation. In preparation for the gene therapy, the participant will receive busulfan chemotherapy and alemtuzumab. After treatment, the participant will have follow-up visits every few months in the first 2 years after treatment. Long-term visits will continue annually for 15 years.