1088. Stem Cell Gene Therapy with No Pre-Conditioning for the ADA-Deficiency Patients Leads to Generalized Detoxification and Delayed, but Steady Hematological Reconstitution

In the previous meeting, we reported the initial follow-up of the two patients with adenosine deaminase (ADA)-deficiency whom we had treated in a clinical trial of retroviral-mediated stem cell gene therapy (SCGT). Our protocol is unique in that patients do not receive any kinds of marrow-preparative conditioning prior to infusion of gene-corrected autologous bone marrow (BM) cells. Since the successful cases of ADA gene therapy reported from Italy used low-dose busulfan to enhance the engraftment of gene-transduced BM cells, it is intriguing to see how the lack of conditioning affects the hematological and immunological reconstitution in our patients.