Fitusiran Prophylaxis Reduces Bleeds Versus Prior Factor or Bypassing Agent Prophylaxis in Hemophilia A and B Patients

Prophylaxis with fitusiran, Sanofi’s investigational small interference RNA (siRNA) therapeutic, significantly reduced bleeding in a Phase III multinational study in adults and adolescents with hemophilia A or B, with or without inhibitors, compared to their previous factor or bypassing agent (BPA) prophylaxis. Fitusiran targets antithrombin to rebalance hemostasis in people with hemophilia A or B, regardless of inhibitor status.

Of 65 study participants eligible for annualized bleeding rate (ABR) analyses, 50 had hemophilia A and 15 had hemophilia B; 19 participants had an inhibitor and 46 did not have an inhibitor. Median observed ABRs (interquartile range) were 4.4 (2.2; 10.9) with prior factor or BPA prophylaxis, and 0.0 (0.0; 2.3) with fitusiran prophylaxis. Fitusiran prophylaxis resulted in a 61.1 percent reduction in the estimated ABR versus factor or BPA prophylaxis

Forty-one of the 65 participants (63.1%) treated with 80 mg of subcutaneous fitusiran over a period of seven months experienced zero treated bleeds, compared to 11 (16.9%) of these participants on prior factor or BPA prophylaxis. Fitusiran also significantly improved health-related quality of life (HRQoL) in relation to prior factor or BPA, as measured by the Haem-A-QOL total score. Serious adverse events occurred in five of 65 participants (7.7%) during factor/BPA prophylaxis and nine of 67 (13.4%) during fitusiran prophylaxis. Two participants experienced suspected or confirmed thromboembolic events with fitusiran.