French previously untreated patients with severe hemophilia A after exposure to recombinant factor VIII : incidence of inhibitor and evaluation of immune tolerance.

Fifty French previously untreated patients with severe hemophilia A (factor VIII < 1%), treated with only one brand of recombinant factor VIII (rFVIII), were evaluated for inhibitor development, assessment of risk factors and outcome of immune tolerance regimen. The median period on study was 32 months (range 9-74) since the first injection of rFVIII. Fourteen patients (28%) developed an inhibitor, four of whom (8%) with a high titer (> or = 10 BU).