The evidence behind inhibitor treatment with porcine factor VIII.

Factor VIII auto- and alloantibodies neutralise porcine factor VIII to a lesser extent than factor VIII of human origin. The reduced reactivity of the porcine molecule, predominantly due to sequence variation in the A2 and C2 domains, has been the rationale for using porcine factor VIII to secure haemostasis for patients with factor VIII inhibitors. Porcine factor VIII has been shown to provide effective haemostatic control particularly for patients with intermediate inhibitor titres with limited porcine cross-reactivity. Small studies have indicated porcine factor VIII can be associated with desensitisation of some factor VIII inhibitor patients. Porcine factor VIII has been shown to produce mild platelet agglutination, an effect that may enhance its efficacy. Adverse reactions are dose-related and do not preclude safe and effective long-term home use for the subgroup of inhibitor patients with modest or absent anamnestic response. Efforts to secure source plasma free of viral markers, particularly porcine parvovirus, have limited the supply of this therapeutic product.