Compstatin TFA, a 13-residue cyclic peptide, is a potent inhibitor of the complement system C3 with species specificity. Compstatin TFA binds to baboon C3 and is resistant to proteolytic cleavage in baboon blood (similar to humans). Compstatin TFA inhibits only the activation of primates’ complement system. Compstatin TFA exhibits IC50 values of 63 μM and 12 μM for classical and alterative complement pathway, respectively.