Effects of long-term administration of recombinant human protein C in xenografted primates.

Background. The role potential of recombinant human activated protein C (rhaPC), a recently developed molecule with anticoagulant and antiinflammatory properties, in prolonging survival in immunosuppressed primate recipients of porcine renal xenografts has been evaluated. Methods. rhaPC was administered daily for 5 days (24 μg/kg/hr; group A; n=3) or throughout the postoperative period (8–24 μg/kg/hr; group B; n=2; or 24–48 μg/kg/hr; group C; n=4). Animals in group D (n=2) received rhaPC daily (24 μg/kg/hr) combined with recombinant human antithrombin (84 U/kg every 8 hr). Two animals served as control (group E). Results. The results indicate that rhaPC is protective against fibrin deposition early after transplantation but does not prevent fibrin deposition and the occurrence of acute humoral xenograft rejection (AHXR) later on. Animals in the study survived between 8 and 55 days. At the dose used, rhaPC is able to prevent fibrin deposition in the graft in the first 2 weeks after xenotransplantation, except when it is administered in conjunction with antithrombin. However, rhaPC did not prevent the eventual occurrence of AHXR in primate recipients of porcine xenografts. Conclusions. In this pig to primate model, rhaPC confers a short advantage in the prevention of early perioperative xenograft damage but does not represent an effective strategy for preventing AHXR.