Compstatin, a cyclic tridecapeptide, discovered from a phage-display library, is a highly potent and selective complement component 3 (C3) inhibitor, binding to C3, C3b, and C3c, but not to C3d. Compstatin binds to C3 in a reversible manner and inhibits proteolytic cleavage by C3 convertase to the proteins C3a and C3b and consequent activation of classical and alternative complement pathways. Compstatin accordingly acts as a complement inhibitor and prolongs graft survival and reduces hyperacute rejection of pig kidneys perfused with human blood, and inhibits in vivo heparin/protamine induced complement activation in primates.
