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Pfizer and Sangamo's haemophilia A gene therapy shows promise at Phase 1/2

Published on 08/07/19 at 11:01am

Pfizer and Sangamo Therapeutics have shared new Phase 1/2 data for their investigational SB-525 gene therapy in the treatment of haemophilia A, showing that it was “generally well-tolerated and demonstrated a dose-dependent increase in Factor VIII (FVIII) activity levels.”

The shared data was drawn from research conducted in 10 participants and was presented at the 27th Congress of the International Society on Thrombosis and Haemostasis (ISTH), in Melbourne, Australia. The patients were treated across four ascending dose cohorts: 9e11 vg/kg (2 patients), 2e12 vg/kg (2 patients), 1e13 vg/kg (2 patients) and 3e13 vg/kg (4 patients). Across these cohorts, it was observed that patients “demonstrated a dose-dependent increase in FVIII levels and a dose-dependent reduction in the use of FVIII replacement therapy”.

“The initial results with SB-525 gene therapy for patients with severe haemophilia A continue to look very promising,” commented Dr Barbara Konkle, Professor of Medicine at University of Washington and a Principal Investigator of the Alta study. “It is encouraging that patients in the 3e13 vg/kg cohort have attained normal Factor VIII levels within five-to-seven weeks of treatment with SB-525 gene therapy and have sustained Factor VIII activity with no bleeding episodes. It will be important to continue to follow these patients to understand the potential long-term durability of this gene therapy.”

The therapy is currently under accelerated review by the FDA, with the US regulator awarding regenerative medicine advanced therapy (RMAT) designation based on the back of data from the Alta study.

“The initial results of the Alta study presented at ISTH demonstrate that SB-525 has the potential to be a predictable and reliable treatment that may bring clinical benefit to patients with haemophilia A,” said Dr Adrian Woolfson, Executive Vice President of Research and Development, San. “The results show that SB-525 is well tolerated, that Factor VIII levels in the first two patients in the 3e13 vg/kg cohort reached normal, sustained levels as measured using a chromogenic assay, and that variability of Factor VIII activity is low, both within each patient and within each dose cohort. We look forward to continuing to follow these patients to further understand the durability of response to SB-525 gene therapy and to working with Pfizer to potentially advance a registrational study.”

Seng Cheng, Senior Vice President and Chief Scientific Officer of Pfizer’s Rare Diseases Research Unit, also remarked: “We are encouraged by the initial clinical data suggesting safety, tolerability, and efficacy of SB-525 and are beginning preparations, including manufacturing, to potentially advance into a registrational study. We are also encouraged by our interactions with regulators and by the FDA’s recent RMAT designation. If FVIII levels are sustained, and patients continue to have no bleeding episodes and remain off factor replacement therapy, we believe that this gene therapy may potentially represent a transformative treatment paradigm for severe haemophilia A.”

Matt Fellows

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