Human recombinant DNA-derived antihemophilic factor in the treatment of previously untreated patients with hemophilia A: final report on a hallmark clinical investigation

Background: Development of recombinant factor VIII (rFVIII) replacement therapy represents a milestone in the treatment of hemophilia A.Objective: The objective of this long-term, multicenter study was to assess the safety, efficacy and rate of inhibitor formation of rFVIII (Kogenate®) in the treatment of hemophilia A in a group of previously untreated patients (PUPs).Patients and methods: Between January 1989 and October 1997, 102 evaluable patients (mean age 3.9 years) were treated with rFVIII as sole therapy for prophylaxis against bleeding or for hemorrhage. Patients with mild hemophilia were treated for ≥2 years, while those with moderate or severe hemophilia were treated for ≥5 years or 100 exposure days.Results: All patients responded well to therapy, so that 82% of bleeding episodes required a single infusion for treatment. Only four mild drug-related adverse events were recorded during the study for an overall rate of 0.03% (4/13 464 infusions). No viral seroconversions were observed. The inhibitor incidence in PUPs with severe hemophilia was 29% (19/65). Overall, inhibitory antibodies developed in 21 patients (20.6%). Inhibitor titers were low (<10 Bethesda Units) in nine of the 21 patients despite continued episodic treatment with rFVIII and transient in eight patients receiving episodic treatment (seven low titer, one high titer). Eight high-titer inhibitor patients were treated with immune-tolerance induction therapy; five had successful outcomes.Conclusions: The observed incidence of inhibitor formation is similar to studies of PUPs receiving plasma-derived FVIII. These results demonstrate the safety and efficacy of rFVIII in long-term treatment of hemophilia A.