Busulfan is a chemotherapy drug used to “make space” in the bone marrow to facilitate engraftment of gene-modified blood-forming stem cells.
Results of using busulfan in a series of clinical trials of hematopoietic stem cell gene therapy for adenosine deaminase deficient severe combined immune deficiency (ADA SCID) are reported. Measruing each individual patients levels of busulfan and adjusting subsequent doses leads to more consistent drug levels and engraftment of stem cells.