ATLANTA, Dec. 11, 2024 /PRNewswire/ -- Expression Therapeutics, Inc., has presented the results of a Phase 1 clinical trial for its novel lentiviral vector-based gene therapy — ET3 — for hemophilia A at the Annual Meeting of the American Society of Hematology (ASH) in San Diego, California. The results of the study, "Lentiviral Gene Therapy with CD34+ Hematopoietic Cells for Hemophilia A" (Srivastava et al), were published by the New England Journal of Medicine, timed for release with the ASH presentation.

Hemophilia A results from a deficiency in blood coagulation Factor VIII (FVIII). It is the most common severe congenital bleeding disorder, with an incidence of approximately 1 in 5,000 live male births. Without treatment, severe hemophilia A is crippling and fatal by late adolescence to early adulthood. The average annual cost per patient of managing hemophilia A in the United States ranges from over $200,000 to $850,000, making it one of the most expensive treatments over a lifetime for any genetic disorder. As a result, a curative gene therapy for hemophilia A can lead to significant long-term cost savings for healthcare systems compared to current prophylaxis treatments, in addition to improved quality of life for patients.

The clinical trial, conducted at the Christian Medical College, Vellore, India, recruited five participants 22 to 41 years of age with severe hemophilia A. Autologous hematopoietic stem cells (HSCs) were transduced with CD68-ET3-LV — a lentiviral vector including a novel FVIII transgene (ET3) with a myeloid-directed CD68 promoter. Before gene therapy, all participants reported annualized bleeding rates of at least 20 events. No spontaneous bleeding events occurred in any participant on study. These results were consistent with measured FVIII levels, which in all five participants increased from undetectable to levels predicted to produce therapeutic efficacy. The median follow-up was 14 months (range, 9 to 27 months). Except for neutropenia and thrombocytopenia (which were expected), no adverse events greater than grade 2 occurred in any participant. Inhibitors to FVIII did not develop in any participant after drug-product infusion. Integration-site analysis performed at 4 to 22 months after drug-product infusion showed no safety concerns.

The results of this Phase 1 clinical trial validate a new approach to gene therapy for hemophilia A that can provide lifelong durability of expression. The candidate CD68-ET3-LV-CD34+ gene therapy product overcomes the limitations of the AAV gene therapy approaches to hemophilia A, including lack of durability of expression, ineligibility of patients on the basis of age, and preexisting anti-AAV antibody related conditions. Expression Therapeutics lentiviral gene therapy is currently the only approach that offers the possibility of a permanent cure for hemophilia A and provides an opportunity to reach both pediatric and adult populations.

"This Phase I clinical trial produced no unexpected safety issues and remarkable clinical efficacy. Lentiviral vector hematopoietic stem cell therapy offers the hope of permanent cure of hemophilia A patients that ultimately may be extended to the pediatric population," said Pete Lollar, MD, Chairman of the Board of Expression Therapeutics and Hemophilia of Georgia Professor at Emory University School of Medicine.

"We are grateful to Dr. Alok Srivastava, Christian Medical College/Centre for Stem Cell Research/inSTEM, and, most importantly, the participants and their families for collaborating on this unique therapeutic development program with curative potential. We have demonstrated safety and efficacy in our Phase 1 trial and look forward to continued development of a lentiviral mediated hematopoietic stem cell gene therapy for the benefit of hemophilia A patients worldwide," said Mohan Rao, Ph.D., the Chief Executive Officer of Expression Therapeutics.

About Expression Therapeutics, Inc.:

Expression Therapeutics, Inc., headquartered in Atlanta, Georgia, with a state-of-the-art GMP manufacturing facility in Cincinnati, Ohio, is a clinical-stage gene and cell therapy company advancing curative therapies for hemophilia A and developing innovative oncology solutions targeting neuroendocrine tumors and neuroblastoma.

For inquiries, please contact:

Kim Nearing
Chief Business Officer
Expression Therapeutics, Inc.
1860 Montreal Road
Tucker, Georgia 30084
knearing@expressiontherapeutics.com
+1 650.743.4993

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SOURCE Expression Therapeutics, Inc.