Pfizer reports positive late-stage results for haemophilia A gene therapy

Pfizer has announced promising results from a late-stage clinical trial of its experimental gene therapy for adults with moderately severe-to-severe haemophilia A. This rare bleeding disorder affects approximately 25 in every 100,000 male births worldwide and is characterized by insufficient levels of factor VIII, a protein crucial for blood clotting.

The investigational therapy, giroctocogene fitelparvovec, is being developed in collaboration with Sangamo Therapeutics. The treatment is designed to enable patients to produce factor VIII on their own for an extended duration after a single intravenous infusion.

The phase 3 AFFINE study, which evaluated the candidate, successfully met its primary objective by demonstrating non-inferiority and superiority in the total annualized bleeding rate from week 12 to at least 15 months post-infusion, compared to routine factor VIII replacement prophylaxis treatment. The study also achieved key secondary endpoints, with 84% of patients maintaining factor VIII activity above 5% at 15 months post-infusion, and the majority of participants achieving factor VIII activity of at least 15%.

The therapy was generally well tolerated, with 13 serious treatment-related adverse events reported by ten patients, which were largely resolved through clinical management, according to Pfizer.

Professor Andrew Leavitt, the lead investigator from the University of California, highlighted the transformative potential of the gene therapy, noting its superior bleed protection compared to routine factor VIII prophylaxis and its potential to reduce the treatment burden for those living with haemophilia A.

James Rusnak, Pfizer's senior vice president and chief development officer for internal medicine and infectious diseases research and development, expressed the company's enthusiasm about advancing the candidate. He emphasized the importance of addressing the medical and treatment challenges associated with frequent and time-consuming intravenous infusions or injections.

Giroctocogene fitelparvovec has received fast track and regenerative medicine advanced therapy designations from the US Food and Drug Administration (FDA), as well as orphan drug designations in both the US and the European Union.

This development follows closely on the heels of another significant milestone for Pfizer. Just three months prior, the FDA approved Pfizer's haemophilia B gene therapy, Beqvez (fidanacogene elaparvovec-dzkt), for treating adults with moderate-to-severe cases of the condition.