PROJECT SUMMARY – OVERALL This PPG is focused on developing safe and effective gene therapy approaches to treat sickle cell disease (SCD), Wiskott-Aldrich syndrome (WAS), and x-linked severe combined immunodeficiency (XSCID). Our overall approach is based on using self-inactivating lentiviral vectors as well as genome editing approaches to correct autologous CD34+ HSCs, which will be administered after busulfan-based conditioning and tested in a series of pre-clinical studies and human clinical trials. In Project 1, Dr. Weiss and his colleagues will validate a novel high-titer lentiviral vector for erythroid-specific expression of BCL11A shRNA and test this in a clinical trial for SCD gene therapy. In parallel, genome editing approaches will be developed to de-repress fetal hemoglobin (HbF) in adult red blood cells and tested in primary human CD34+ HSCs. In Project 2, Dr. Rawlings and his colleagues will perform multi-center trials to evaluate the safety, feasibility, and efficacy of lentiviral gene transfer in WAS patients. The second aim will be to develop efficient means to use genome editing to correct WAS either by targeting safe harbor loci or by correcting the endogenous WAS allele. In Project 3, Dr. Sorrentino and his colleagues will prove the effectiveness of using the first lentiviral vector for XSCID, along with subablative busulfan conditioning, to treat both newly diagnosed infants and older children with XSCID. These studies will complete enrollment on two open XSCID gene therapy trials and are expected to lead to commercialization of this approach. Core A will provide essential administrative support and coordination between the various projects and centers. Core B will provide scientific expertise for development and production of viral vectors for all three projects. Core C will provide GMP manufacturing for all lentiviral vectors used all planned clinical trials, and provide GMP cell processing to generate transduced CD34+ HSCs for the St. Jude-sponsored gene therapy trials. Altogether, this P01 brings together the necessary expertise to fully develop gene therapy for these selected disorders in the context of a multi-center consortium providing diverse and multidisciplinary expertise in all required aspects of this work. Realization of the aims of this PPG will provide new approaches for treating these severe monogenetic disorders of the hematopoietic and immune system and provide novel and high impact scientific data that will broadly inform human lentiviral/HSC gene therapy.