Pfizer and Sangamo Therapeutics have reported positive follow-up data from the Phase I/II Alta study of giroctocogene fitelparvovec (PF-07055480) to treat patients with severe hemophilia A.

The investigational gene therapy Giroctocogene fitelparvovec consists of a recombinant adeno-associated virus serotype 6 vector (AAV6) encoding the complementary deoxyribonucleic acid for B domain deleted human FVIII.

The open-label, dose-ranging, multi-centre Alta clinical trial has been designed to assess the safety and tolerability of the therapy in severe hemophilia A patients.

Across four dose cohorts, the mean age of the 11 patients assessed is 30 years and all are male.

All five patients with severe hemophilia A were given the 3e13 vg/kg dose and they showed sustained factor VIII (FVIII) activity levels, with a median of 64.2% via chromogenic assay.

No patients experienced bleeding events or required FVIII infusions during the trial.

Pfizer Rare Disease Research Unit senior vice-president and chief scientific officer Seng Cheng said: “We are excited that these data affirm previous findings from this Phase I/II study, and that all five patients have sustained levels of factor VIII activity with no bleeding events or use of factor replacement therapy.

“The Phase III lead in study is ongoing, and we look forward to dosing patients with this investigational gene therapy in the pivotal Phase III trial later this year.”

Giroctocogene fitelparvovec received orphan drug, fast track, and regenerative medicine advanced therapy (RMAT) designations from the US Food and Drug Administration and Orphan Medicinal Product designation from the European Medicines Agency.

The therapy is being developed as part of a collaboration agreement between Sangamo and Pfizer for the global development and commercialisation of gene therapies for hemophilia A.

Sangamo chief medical officer Bettina Cockroft said: “These follow-up data indicate that treatment with giroctocogene fitelparvovec resulted in sustained factor levels up to 14 months following treatment and suggests the potential of this investigational gene therapy to alleviate the treatment burden of current hemophilia disease management.”