Gene therapy for PNP deficiency protocol

Purine nucleoside phosphorylase (PNP) is a key enzyme required for the degradation of purine nucleosides into uric acid or their salvage into nucleic acids. Patients who are deficient in PNP suffer from progressive T cell immunodeficiency, with increased susceptibility to infections, autoimmunity, and neurologic abnormalities. In the absence of successful treatment to restore immune function, these patients rarely survive to adulthood. Hematopoietic stem cell transplantation is the only known cure for PNP deficiency. Use of an HLA-matched donor is preferable as the outcome with alternative donors have been variable; however, this option is rarely available. Gene therapy represents a therapeutic option that bypasses the need for a donor, and thus associated complications. Although first generation γ-retroviral vectors have been successful in some immunodeficiencies, in others, evidence of insertional mutagenesis prompted a halt in their use. More recently, the introduction of safer lentiviral vectors holds promise in offering a viable option to treat immunodeficiency. Here, we present a clinical trial protocol utilizing self-inactivating lentiviral vectors to treat PNP deficiency. Patients will be evaluated up to 3 years post-transplantation to determine the safety of lentiviral-treated stem cell infusion, as well as the extent of immune reconstitution. Statement of novelty: This protocol describes the novel treatment of PNP deficiency using lentiviral-based gene therapy.