Pfizer Announces Positive Results From Late-stage Study Of Hemophilia B Gene Therapy Candidate

(RTTNews) - Pfizer Inc. (PFE) announced positive results from the Phase 3 BENEGENE-2 study (NCT03861273) evaluating fidanacogene elaparvovec, an investigational gene therapy, for the treatment of adult males with moderately severe to severe hemophilia B.

According to the company, the study met its primary endpoint of non-inferiority and superiority in the annualized bleeding rate (ABR) of total bleeds post-fidanacogene elaparvovec infusion versus prophylaxis regimen with Factor IX (FIX), administered as part of usual care.

The results demonstrated superiority with a mean annualized bleeding rate for all bleeds of 1.3 for the 12 months from week 12 to month 15 compared to an annualized bleeding rate of 4.43 during the lead-in pre-treatment period of at least six months, resulting in a 71% reduction in annualized bleeding rate (p<0.0001) after a single dose of 5e11 vg/kg of fidanacogene elaparvovec.

Secondary endpoints demonstrated a 78% reduction in treated ABR (p=0.0001) and 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.

The mean steady-state FIX:C was significantly higher than the pre-specified threshold of 5% (p<0.0001).

Pfizer noted that it currently has three Phase 3 programs investigating gene therapy in populations where there is a high unmet need: hemophilia B, hemophilia A, and Duchenne muscular dystrophy. A Phase 3 trial is also ongoing investigating marstacimab, a potential novel subcutaneous therapy option being studied for the treatment of people with hemophilia A and B with and without inhibitors.

Fidanacogene elaparvovec has been granted breakthrough, regenerative medicines advance therapy (RMAT), and orphan drug designations from the US Food and Drug Administration, as well as PRIority MEdicines (PRIME) and orphan drug designation from the European Medicines Agency. Pfizer will discuss data with regulatory authorities in early 2023.

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