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 greater than or equal to 50 Bethesda units/micromilligrams 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/micromilligrams). One of these patients, with a titer of 53 Bethesda units/micromilligrams 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.