Pfizer’s Gene Therapy for Hemophilia B Achieves Promising Results in Clinical Study!

Pfizer Inc. (NYSE: PFE) announced today the positive top-line results from the Phase 3 BENEGENE-2 study (NCT03861273) of its investigational gene therapy, fidanacogene elaparvovec, for the treatment of adult males with moderately severe to severe hemophilia B. This breakthrough therapy could have a potentially transformative impact on the lives of those affected by this debilitating blood disorder.

The BENEGENE-2 study proved to be a remarkable success, with a single dose of 5e11 vg/kg of fidanacogene elaparvovec resulting in a 71% reduction in annualized bleeding rate (ABR) (p<0.0001) and a 78% reduction in treated ABR (p=0.0001). Furthermore, the mean steady-state FIX:C was found to be significantly higher than the pre-specified threshold of 5% (p<0.0001). The impressive results of this study showed a mean ABR of 1.3 for the 12 months from week 12 to month 15, compared to an ABR of 4.43 during the lead-in pre-treatment period of at least six months, as well as a 92% reduction in annualized infusion rate (p<0.0001). Mean FIX activity was 27% at 15 months by one-stage SynthASil assay and 25% at 24 months. This study has successfully demonstrated the superiority of fidanacogene elaparvovec infusion over prophylaxis regimen with Factor IX (FIX).

Fidanacogene elaparvovec proved to be a generally safe and well-tolerated treatment, with its safety profile in line with earlier Phase 1/2 results. Despite this, seven (16%) patients reported fourteen serious adverse events, two of which were attributed to the treatment itself, namely a duodenal ulcer hemorrhage and an elevation of liver aminotransferase levels due to an immune response. Thankfully, no deaths, infusion reactions, thrombotic events, or FIX inhibitors were reported.

Fidanacogene elaparvovec is an exciting investigational gene therapy with the potential to revolutionize treatment for people living with hemophilia B. This one-time intravenous treatment of a bio-engineered adeno-associated virus (AAV) capsid and high-activity human coagulation FIX gene could provide a long-term solution to the need for regular exogenous FIX prophylaxis therapy. A total of 45 participants were enrolled in the BENEGENE-2 study, where they underwent a six-month lead-in period before receiving the one-time dose of fidanacogene elaparvovec at 5e11 vg/kg. A validated assay was used to screen for the presence of neutralizing antibodies to the gene therapy vector. The long-term study will monitor participants for 15 years to assess the safety and efficacy of the gene therapy.

Pfizer is proud to be advancing the latest innovation for people living with hemophilia B with the potential of an investigational gene therapy. With over 30 years of experience in developing and commercializing therapies for hematological disorders, and a deep understanding of the challenges faced by people living with hemophilia, Pfizer is committed to unlocking the full potential of gene therapies for those affected. We are incredibly grateful to the participants and investigators who are contributing to this innovative research.

Pfizer is currently in the midst of revolutionary research to develop gene therapies for hemophilia B, hemophilia A, and Duchenne muscular dystrophy – three populations with a significant unmet medical need. Additionally, the company is studying marstacimab, a potential subcutaneous therapy for hemophilia A and B, with and without inhibitors, through an ongoing Phase 3 trial. This innovative approach could be a game-changer in the fight against these debilitating conditions.

The burden of living with hemophilia B can be overwhelming, with many people having to receive routine infusions or injections that can get in the way of participating in everyday activities that others take for granted. However, the BENEGENE-2 data offers a glimmer of hope for those living with the condition, providing evidence of the potential of gene therapy as a one-time option for reducing the clinical and treatment burden in the long run. Adam Cuker, M.D., M.S., Director of Penn Comprehensive and Hemophilia Thrombosis Program, commented on the exciting findings.

Fidanacogene elaparvovec has been granted a number of prestigious designations from both the US Food and Drug Administration and the European Medicines Agency, including breakthrough, regenerative medicines advance therapy (RMAT), PRIority MEdicines (PRIME), and orphan drug designations. Pfizer is looking forward to engaging in discussions with regulatory authorities in the coming year of 2023.

We look forward to presenting additional key data at a scientific conference in early 2023, providing a deeper insight into our findings and progress.

About fidanacogene elaparvovec

Fidanacogene elaparvovec holds the potential to revolutionize the lives of people living with hemophilia B. This novel gene therapy contains a bio-engineered AAV capsid and a high-activity human coagulation FIX gene, and if successful, could provide a one-time treatment that would allow people with hemophilia B to produce their own FIX. This groundbreaking therapy could potentially change the lives of countless individuals around the world.

Pfizer and Spark Therapeutics joined forces in December 2014 to develop SPK-9001 (fidanacogene elaparvovec), an investigational gene therapy. Spark Therapeutics took the lead on Phase 1/2 studies, while Pfizer was responsible for conducting pivotal studies, handling all regulatory activities, and preparing for potential global commercialization.

About Hemophilia B

Hemophilia is a rare and life-threatening genetic disorder that primarily affects males. Those with the disorder have a deficiency in one or more of their blood clotting factors, meaning they experience excessive and recurrent bleeding even from minor injuries. Severe cases of hemophilia can also cause spontaneous bleeding into the muscles, joints, and even into the brain, which can be fatal if left untreated.

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