Pfizer Taking over Development of Potential Gene Therapy SB-525, Advancing into Phase 3 Trials

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by Patricia Inacio PhD |

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Sangamo Therapeutics has handed over the development of SB-525, a gene therapy for hemophilia A, to Pfizer, which will now advance the therapy into Phase 3 clinical trials.

Pfizer has already started recruiting participants for the lead-in Phase 3 trial (NCT03587116). which will support SB-525’s advancement to a Phase 3 registrational clinical trial. The six-month study is evaluating the current effectiveness and safety of preventive replacement therapy in the usual care setting. The study will also support the advancement of fidanacogene elaparvovec, an investigational gene therapy previously known as SPK-9001, into a Phase 3 trial for hemophilia B.

SB-525 was originally developed by Sangamo Therapeutics in collaboration with Pfizer, with Sangamo leading a Phase 1/2 trial (NCT03061201) to test the therapy’s safety and efficacy. Sangamo has now transferred the investigational new drug application (IND) for SB-525 ahead of schedule to Pfizer, which will lead its clinical development. Sangamo received a $25 million milestone payment.

“I want to congratulate our team for their success in developing SB-525 through to this important milestone where we have handed over the IND to Pfizer for Phase 3 development,” Sandy Macrae, CEO of Sangamo, said in a press release.

“We are thrilled to be in a partnership where both parties have cooperated to accelerate study timelines, resulting in completion of the IND transfer ahead of schedule. Pfizer and Sangamo are united in our common interest to help patients with Hemophilia A and will do everything that we can to safely and expeditiously advance this promising gene therapy candidate for patients in need,” Macrae added.

SB-525 was created specifically as a one-time treatment to help with the continuous production of a working factor VIII (FVIII) — the clotting factor missing in hemophilia A. The gene therapy delivers genetic information for the production of FVIII to liver cells, where clotting factors are produced, using a harmless adeno-associated viral (AAV) vector. As such, SB-525 is intended to help cells naturally produce FVIII, which reduces or removes the need for replacement therapy.

The Phase 3 trial is being launched after promising results of the open-label Phase 1/2 Alta trial (NCT03061201) presented at the 61stAnnual Meeting of the American Society of Hematology, held recently in Orlando, Florida. Sangamo also presented the results at its Research and Development Day in December, where it provided updates on its pipeline.

The study is testing a single intravenous (into the vein) infusion of one of four ascending doses of SB-525: 9×1011 vector genomes per kilogram of body weight (vg/kg);  2×1012 vg/kg; 1×1013 vg/kg; and 3×1013 vg/kg. Two people have been dosed per group, except for the highest dose group, which was expanded to five patients.

Patients receiving the highest dose of SB-525 (3×1013 vg/kg) showed normal FVIII activity. Furthermore, following a short preventive course after dosing, the patients no longer required replacement therapy.

SB-525 has been granted orphan drug, fast track, and regenerative medicine advanced therapy designations by the U.S. Food and Drug Administration and orphan medicinal product designation by the European Medicines Agency. These designations are intended to speed up and support the therapy’s clinical development and marketing approval.