Food and Drug Administration Office of Orphan Product Development award, RO1 FD003005; NHLBI awards, PO1 HL73104 and Z01 HG000122; UCLA Clinical and Translational Science Institute awards, UL1RR033176 and UL1TR000124.

Patients lacking functional adenosine deaminase activity suffer from severe combined immunodeficiency (ADA SCID), which can be treated with ADA enzyme replacement therapy (ERT), allogeneic hematopoietic stem cell transplantation (HSCT), or autologous HSCT with gene-corrected cells (gene therapy-GT). A cohort of 10 ADA SCID patients, aged 3 months to 15 years, underwent GT in a Phase II clinical trial between 2009 and 2012. Autologous bone marrow CD34+ cells were transduced ex vivo with the MND-ADA gamma-retroviral vector (gRV) and infused following busulfan reduced intensity conditioning. These patients were monitored in a long-term follow-up protocol over 8-11 years. Nine of ten patients have sufficient immune reconstitution to protect against serious infections, and have not needed to resume ERT or proceed to secondary allogeneic HSCT. ERT was restarted 6 months after GT in the oldest patient who had no evidence of benefit from GT. Four of nine evaluable patients with the highest gene marking and B cell numbers remain off immunoglobulin replacement therapy and responded to vaccines. There were broad ranges of responses in normalization of ADA enzyme activity and adenine metabolites in blood cells, and levels of cellular and humoral immune reconstitution. Outcomes were generally better in younger patients and those receiving higher doses of gene-marked CD34+ cells. No patient experienced a leukoproliferative event after GT, despite persisting prominent clones with vector integrations adjacent to proto-oncogenes. These long-term findings demonstrate enduring efficacy of GT for ADA SCID, but risks of genotoxicity with gRVs. (Clinicaltrials.gov #NCT00794508)

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Lentiviral vectors (LVs) are attractive vehicles for liver-directed gene therapy by virtue of their ability to stably integrate in the genome of target cells and the lack of pre-existing immunity against vector components in most humans. Over the past years, we have developed a LV platform that can achieve stable transgene expression in the liver, induce transgene-specific immune tolerance and establish correction of hemophilia in mouse models upon systemic administration. This LV is designed to stringently target transgene expression to hepatocytes through transcriptional and microRNA-mediated regulation. We then investigated the efficacy and safety profile of portal vein administration of LVs expressing wild-type, codon-optimized (c.o.) or c.o. and hyperactive factor IX (FIX) in a canine model of hemophilia B. We produced large-scale batches of LVs qualified for in vivo administration and treated adult hemophilia B dog by portal vein administration. We observed longterm stable reconstitution of canine FIX activity up to 1% of normal and significant amelioration of the clinical phenotype in 3 treated dogs (>9 years cumulative follow up). LV infusion was associated with transient signs of inflammation and mild hepatotoxicity, which could be abrogated by pretreatment with anti-inflammatory drugs. There was no detectable long-term toxicity or development of FIX inhibitors. In the perspective of clinical translation and to increase therapeutic efficacy, we next treated an 11-kg, hemophilia B dog by peripheral vein administration of LVs expressing the c.o. and hyperactive canine FIX at a 5-fold higher dose than those previously administered. At the current follow-up (3 months after gene therapy) FIX activity is 6-9% of normal. Intravenous LV administration, coupled with a 1-day antiinflammatory and anti-histamine pre-treatment, induced mild and selflimiting leukopenia and elevation of aminotransferases. Treatment of more hemophilia B dogs is underway to confirm and extend these results. Overall, our studies, which suggest comparable efficacy of LV by both portal and peripheral vein administration, position LVmediated liver gene therapy for further pre-clinical development and clinical translation. LVs may thus complement other available vectors to address some of the outstanding challenges posed by liver gene therapy of hemophilia and conceivably other diseases. Recombinant human EPO (rHuEPO) along with iron supplementation corrects anemia in most patients with End StageRenal Disease (ESRD) but is associated with supra-physiological peak serum concentration (C max ) of EPO and may cause thromboembolic complications.The Transduced Autologous Restorative Gene Therapy system (TARGT™) is an ex-vivo gene therapy that provides autologous, continuous proteins or peptide therapy in the physiological range. The system consists of several 2 x 30 mm pieces of dermal tissue (Micro-Organ, MO), extracted under local anesthetic in which its fibroblasts cells are transduced with a Helper-Dependent Adenoviral Vector (HDAd) containing...