Pfizer, Sangamo Re-Opens Enrolment For Hemophilia A Gene Therapy

Pfizer and Sangamo Therapeutics have re-opened recruitment of patients for the Phase 3 Affine study of their gene therapy, giroctocogene fitelparvovec, for severe hemophilia A. Patient dosing is expected to resume in October. The trial was previously suspended last November due to safety concerns. 

Readout for the trial, originally slated for 2023, is now expected in the first half of 2024, said Pfizer. 

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Gene Therapy for Hemophilia A 

Hemophilia A is a rare inherited blood disorder caused by a gene mutation that leads to the insufficient activity of Factor VIII, a blood clotting protein. Patients with this disorder bleed longer than normal people. There are an estimated 16,000 patients in the US and more than 150,000 patients worldwide with hemophilia A. 

Giroctocogene fitelparvovec is a gene therapy consisting of an rAAV vector with a Factor VIII gene construct driven by a synthetic, liver-specific promoter that is intended to restore the activity of the clotting factor. 

The gene therapy has been granted Orphan Drug, Fast Track, and regenerative medicine advanced (RMAT) designations by the US FDA. In Europe, the EMA has granted the drug Orphan Medicinal Product designation. 

A clinical hold was imposed on the drug by the US FDA after the treatment led to higher-than-normal levels of Factor VIII in some patients, with one patient experiencing deep vein thrombosis in the leg. The clinical hold was later lifted this May after Pfizer and Sangamo adjusted their study protocol. 

Sangamo began its collaboration with Pfizer in 2017 to develop giroctocogene fitelparvovec, then known as SB-525. Under the terms of the deal, Sangamo received a $70 million upfront payment, and could receive up to $300 million in milestone payments as well as tiered double-digit royalties on net sales. The collaboration included developing other hemophilia A gene therapy candidates, which could net Sangamo up to $175 million in milestones. 

Author

Joy Lin

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