Emerging treatments

Gene therapy

Gene therapy has been used successfully for both adenosine deaminase deficient SCID (ADA-SCID) and X-linked SCID.[56][57][58] In 2016, a gene therapy treatment protocol that modifies autologous stem cells to produce ADA (Strimvelis®) was approved in Europe for the treatment of ADA-SCID in those with no matching donor for stem cell transplant.[59] This recommendation was based on a study of 12 patients who received Strimvelis® gene therapy, all of whom were alive at an average follow-up period of 7 years. The first successful trial of gene therapy for X-linked SCID was reported in 2000.[56] Ten patients were treated; 8 patients had reconstitution of T-cell counts with normalised function and diversity. In addition, normal immunoglobulin levels were seen in most of the patients. Long-term follow-up (8 to 11 years) did not show genotoxicity.[60] Several patients with X-linked SCID developed leukaemia after gene therapy due to retroviral insertion and subsequent activation of proto-oncogenes.[56] By contrast, there have been no reports to date of leukaemia with gene therapy for ADA-SCID. New approaches using alternative delivery ways, such as lentiviral vectors and gene editing, are being investigated for X-linked SCID, Artemis-SCID, IL7R-SCID, RAG1-SCID, and RAG2-SCID.[61]

JSP191

JSP191, a novel monoclonal antibody, is being studied in patients with SCID undergoing haematopoietic stem cell transplant (HSCT).[62] JSP191 binds to CD117, which in turn blocks CD117 from binding to stem cell factor. Without this binding, haematopoietic stem cells are cleared from the bone marrow, allowing an empty space for donor or gene-corrected transplanted cells to engraft. JSP191 has received fast track designation from the US Food and Drug Administration for the treatment of patients with SCID undergoing HSCT.

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