Lentiviral Mediated Gene Therapy for Pyruvate Kinase Deficiency: A Global Phase 1 Study for Adult and Pediatric Patients

Abstract

Introduction: Pyruvate Kinase Deficiency (PKD) is a rare inherited hemolytic anemia that is caused by mutations in the PKLR gene leading to decreased red cell pyruvate kinase (RPK) activity and impaired erythrocyte metabolism. The disorder is characterized by anemia, reticulocytosis, splenomegaly and iron overload, and may be life-threatening in severely affected individuals. PKD represents a significant unmet medical need as current therapies are palliative and limited to chronic blood transfusions, iron chelation therapy, and splenectomy. The side effects of these supportive treatments include iron overload, end-organ damage and increased infection risks. AG-348, an allosteric activator of RPK, is under evaluation in clinical trials, predominantly in less severely-afflicted transfusion-independent patients. Allogeneic hematopoietic stem cell transplantation (HSCT) has been performed in selected cases and resulted in transfusion independence, suggesting that the disorder may be reversed when an adequate level of hematopoietic stem and progenitor cells (HSPCs) harboring a corrected PKLR gene engraft in the bone marrow (BM). The therapeutic efficacy of allogeneic transplant is limited by the availability of a suitable donor and transplant-associated toxicities. Preclinical studies conducted in a clinically relevant PKD murine model have demonstrated the safety and efficacy of Lin- BM cells transduced with the therapeutic lentiviral vector, PGK-coRPK-WPRE, in ameliorating the PKD phenotype. More specifically, transplantation of transduced cells resulted in increased erythrocyte survival, decreased reticulocytosis, and improvement in the secondary manifestations of hemolytic anemia, including splenomegaly and hepatic iron overload. Based on compelling preclinical data, a global Phase 1 clinical trial RP-L301-0119 (clinicaltrials.gov#NCT04105166) is underway to evaluate the feasibility and safety of lentiviral mediated gene therapy in adults and pediatric subjects with severe PKD. Methods: 6 subjects with severe PKD (defined as having a history of severe and/or transfusion-dependent anemia despite prior splenectomy) will be enrolled in the Phase 1 study; the first 2 subjects will be adults (age ≥18-<50 years), followed by 2 older pediatric subjects (age ≥12-17 years) once initial safety has been established. Subsequently, 2 younger pediatric subjects (age ≥8-11 years) will be enrolled. Peripheral blood (PB) hematopoietic stem cells are collected on two consecutive days via apheresis after mobilization with granulocyte-colony stimulating factor (G-CSF) and plerixafor. CD34+ HSPCs are enriched, transduced with PGK-coRPK-WPRE lentiviral vector (LV), and cryopreserved. Following final release testing of the investigational product (IP), RP-L301, myeloablative conditioning with therapeutic drug monitoring (TDM)-guided busulfan is administered over 4 days. RP-L301 is then 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. Results: An adult female PKD subject (age 31 years) with significant anemia and transfusion requirement has received treatment as of July 2020. Mobilization and apheresis procedures were performed successfully and busulfan conditioning was administered at the target area under the curve (AUC). IP consisted of 3.9×106 CD34+ cells/kg body weight, with a mean vector copy number (VCN) of 2.73. Safety and preliminary efficacy results will be available at the time of presentation. Conclusions: Efficacy in pre-clinical models indicates promising potential for clinical gene therapy in severe PKDHematopoietic stem cell mobilization using G-CSF and plerixafor appears feasible and effective in adult PKD patientsIP was successfully manufactured to meet the required specifications for the Phase 1 clinical study and administered without short-term infusion related complications Disclosures Navarro: Rocket Pharmaceuticals, Inc.: Current equity holder in publicly-traded company, Other: SN has licensed medicinal products and receives research funding and equity from Rocket Pharmaceuticals, Inc., Patents & Royalties, Research Funding. Sevilla:Rocket Pharmaceuticals, Inc.: Consultancy, Current equity holder in publicly-traded company. Glader:Agios Pharmaceuticals, Inc.: Consultancy. Beard:Rocket Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Law:Rocket Pharmaceuticals, Inc.: Current Employment, 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. Bueren:Rocket Pharmaceuticals, Inc.: Consultancy, Current equity holder in publicly-traded company, Other: Consultant for Rocket Pharmaceuticals, Inc. and has licensed medicinal products and receives research funding and equity from this company., Patents & Royalties, Research Funding. Rao:Rocket Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Schwartz:Rocket Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Segovia:Rocket Pharmaceuticals, Inc.: Consultancy, Current equity holder in publicly-traded company, Other: Consultant for Rocket Pharmaceuticals, Inc. and has licensed medicinal products and receives research funding and equity from the Company., Patents & Royalties, Research Funding.

Clinically relevant gene editing in hematopoietic stem cells for the treatment of pyruvate kinase deficiency

“…11 In fact, an international multicentric clinical trial for the treatment of PKD patients is currently on-going (NCT04105166), and has already shown first evidence of therapeutic efficacy. 19 Despite this promising therapy for PKD patients, the emergence of programmable nucleases has revolutionized the gene therapy field, making specific driven integration gene therapy an applicable clinical option. 34 The feasibility of knocking in a cDNA immediately after the start codon of the gene has been recently demonstrated.…”

“…18 This lentiviral-mediated gene therapy approach would offer a durable and curative clinical benefit with a single treatment, as shown by the preliminary results obtained in the first two patients already infused with transduced autologous hematopoietic stem cells (HSCs) (NCT04105166). 19 Despite the promising results of conventional gene therapy, the ideal gene therapy approach should lead to the specific correction of the mutated gene, maintaining the endogenous regulation and eliminating the integration of exogenous DNA material elsewhere. Gene editing can be used as a therapeutic approach to conduct precise homology directed repair (HDR).…”

Preclinical studies of efficacy thresholds and tolerability of a clinically ready lentiviral vector for pyruvate kinase deficiency treatment

“…In fact, a first-in-human gene therapy clinical trial for the treatment of PKD (ClinicalTrials.gov: NCT04105166) is currently active, and the initial patients have been treated as of mid-2020; preliminary clinical data were recently updated, and the efficacy and safety profile have, to date, been encouraging and consistent with our preclinical results. 22…”

Clinically Relevant Gene Editing in Hematopoietic Stem Cells for the Treatment of Pyruvate Kinase Deficiency Hemolytic Anemia

“…Additionally, as initially reported by García-Gómez et al (19) , the correction of the PKLR gene defect by means of lentiviral-mediated gene therapy is feasible and restores RPK functionality. In fact, an international multicentric clinical trial for the treatment of PKD patients is currently on-going (NCT04105166), and has already shown first evidences of therapeutic efficacy (20) . Despite this promising therapy for PKD patients, the emergence of programmable nucleases has revolutionized the gene therapy field, making specific driven integration gene therapy an applicable clinical option (36) .…”

“…We have recently developed a lentiviral vector to genetically correct PKD (19) , which has been granted orphan drug designation by the European and the American office regulators (EU/3/14/1330; FDA #DRU-2016-5168). This lentiviral-mediated gene therapy approach would offer a durable and curative clinical benefit with a single treatment, as shown by the preliminary results obtained in the first patient already infused with transduced autologous HSCs (NCT04105166) (20) .…”