Lentiviral-mediated Gene Therapy for Adults and Children with Severe Pyruvate Kinase Deficiency: Results from an Ongoing Global Phase 1 Study

Background: Pyruvate kinase deficiency (PKD) is a rare inherited hemolytic anemia caused by mutations in the PKLR gene. Manifestations include anemia, splenomegaly and iron overload, which may be life-threatening in severely affected individuals. Current treatments are limited to a recently-approved enzyme activator, and also blood transfusions, chelation therapy and splenectomy which are associated with significant side effects. Based on compelling preclinical data, a global Phase 1 clinical trial RP-L301-0119 (NCT04105166) is underway to evaluate lentiviral mediated hematopoietic stem and progenitor cell (HSPC)-targeted gene therapy for adults and children with severe PKD.

Methods: Splenectomized patients with severe PKD (severe and/or transfusion-dependent anemia) are eligible. Peripheral blood (PB) hematopoietic stem and progenitor cells (HSPCs) are collected on 2 consecutive days via apheresis after mobilization with granulocyte-colony stimulating factor (G-CSF) and plerixafor. Following apheresis, HSPCs are transduced with PGK-coRPK-WPRE lentiviral vector and cryopreserved. Myeloablative therapeutic drug monitoring-guided busulfan is administered over 4 days and the gene therapy product (RP-L301) is thawed and infused. Patients are followed for safety assessments, including replication competent lentivirus (RCL) and insertion site analysis (ISA) and for efficacy parameters including PB and BM genetic correction, decrease in transfusion requirements, clinically significant improvement in anemia, and reduction of hemolysis for 2 years post-infusion.

Results: As of April 2022, 2 adult patients (age 31 and 47 years at enrollment) with severe anemia have received RP-L301. Patient 1 (age 31 years) received 3.9x106 CD34+ cells/kg with mean vector copy number (VCN) of 2.73. Patient 2 (age 47 years) received 2.4x106 CD34+ cells/kg with mean VCN of 2.08. Despite baseline hemoglobin (Hb) levels in the 7.0-7.5 g/dL range, at 18 months post infusion both patients have normal-range hemoglobin (13.0 g/dL and 14.8 g/dL), improved hemolysis and no red blood cell transfusion requirements post-engraftment. Other parameters of hemolysis and anemia (LDH, bilirubin, erythropoietin) are improved. Peripheral blood mononuclear cell (PBMC) vector copy numbers (VCNs) were >1.5 at the 18-month evaluation. Both patients have anecdotally reported improved quality of life, also demonstrated by increases in both the FACT-An and SF-36 scores, with particularly marked improvement in SF-36 energy/fatigue, physical functioning, and general health components. No serious adverse events (SAEs) have been attributed to RP-L301. Hematopoietic reconstitution occurred within 2 weeks post-RP-L301 administration. Insertion site analyses in PB and BM for both adult patients up to 12 months following gene therapy indicate highly polyclonal patterns; no selection of common integration sites in proximity to proto-oncogenes was observed.

Conclusion: RP-L301 was successfully manufactured utilizing autologous HSPCs from patients with severe PKD. Robust and sustained efficacy in both patients at 18 months post-treatment was demonstrated by normalized hemoglobin, improved hemolysis parameters, and no red blood cell transfusion requirements following engraftment (transfusion independence). Both patients reported improved quality of life following treatment. Updated safety and efficacy will be presented.

Shah:Vertex Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Sevilla:Rocket Pharmaceuticals, Inc.: Consultancy, Patents & Royalties: J.Sevilla is an inventor on patents on lentiviral vectors filed by CIEMAT, CIBERER and Fundación Jiménez Díaz, and may be entitled to receive financial benefits from the licensing of such patents; licensed medical products from Rocket Pharma.; Amgen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Miltenyi: Consultancy, Honoraria; SOBI: Consultancy, Honoraria. Navarro:Rocket Pharmaceuticals, Inc.: Current equity holder in publicly-traded company, Patents & Royalties: Dr. Navarro has licensed medicinal products and receives research funding and equity from Rocket Pharmaceuticals, Inc., Research Funding. Zubicaray:Novartis: Consultancy. Glader:Agios: Consultancy. Quintana Bustamante:Rocket Pharmaceuticals, Inc.: Current equity holder in publicly-traded company. Zeini:Rocket Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Choi:Rocket Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Nicoletti:Rocket Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Rao:Rocket Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Bueren:Rocket Pharmaceuticals, Inc.: Consultancy, Patents & Royalties: J.Bueren is an inventor on patents on lentiviral vectors filed by CIEMAT, CIBERER and Fundación Jiménez Díaz, may be entitled to receive financial benefits from the licensing of such patents and receives funding for research., Research Funding. Schwartz:Rocket Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Segovia:Rocket Pharmaceuticals, Inc.: Consultancy, Research Funding.