The use of polyelectrolyte-fractionated porcine factor VIII in the treatment of a spontaneously acquired inhibitor to factor VIII

Polyelectrolyte-fractionated porcine factor VIII concentrate is a recent addition to the therapeutic choices for treatment of factor VIII inhibitor patients, but cross-reactivity of the inhibitor with porcine factor VIII limits its usefulness in some cases. Hemophilic patients with inhibitor titers ≥50 Bethesda units/ml often demonstrate sufficient cross-reactivity (10–20%) to prevent the achievement of a satisfactory plasma factor VIII level and a therapeutic response with porcine factor VIII. We have studied plasma from five women with high-titer, spontaneously acquired factor VIII inhibitors to determine the degree of cross-reactivity with porcine factor VIII. Four of the five had little or no detectable inhibitor to porcine factor VIII despite high titers to human factor VIII (26–143 Bethesda units/ml). One of these patients, with a titer of 53 Bethesda units/ml against human factor VIII, was treated successfully with porcine factor VIII concentrate, given for serious hemorrhagic complications. These studies and other reports support the conclusion that the majority of high-titer spontaneous factor VIII inhibitors exhibit little cross-reactivity with porcine factor VIII and can be treated successfully with this product.