Incidence of immune responses following 102 infusions of autoplex in 18 hemophilic patients with antibody to factor VIII.

An activated prothrombin complex concentrate (Autoplex) was infused for the treatment of 102 bleeding episodes in 18 hemophilia A patients with antibody to factor VIII who were previously known as high responders. Among 95 bleeding episodes treated with a single infusion of the concentrate [43-107 factor VIII correcting units (FECU)/kg], only 1 anamnestic response was observed. On the contrary, a significant rise in antibody titer occurred following 2 of 4 double (at 8-12 hr interval) and all 3 multiple (over 3-10 days) infusions of Autoplex. The occurrence of immune responses may be explained by the presence of factor VIII coagulant antigen (VIII:CAg) in the 26 batches of Autoplex tested by two-site immunoradiometric assay (10-36 U/vial). The anamnestic response was not correlated to the batch used nor to the amount (0.6-7.8 U/kg/day) of VIII:CAg infused per day. However, exposure to the concentrate over several days appeared to be the major predisposing factor for an immune response.