PMX205 is a cyclic hexapeptide (c[Arg-Trp-D-Cha-Pro-Orn]-Hca), which is an antagonist of the C5a complement receptor. Human C5a, a complement-derived anaphylatoxin, is a potent mediator of human leukocyte chemotaxis. C5a in particular is a potent inflammatory mediator and signalling through CD88 mediates chemotaxis of leukocytes, vascular permeability could be increased, mast cells release inflammatory mediator and smooth muscle cell contracts and other activities, but all the activities contribute to inflammation and potent tissue damage. C5a-mediated leukocyte chemotaxis release from cytochalasin B-treated cells closely paralleled uptake of the ligand, clearly indicating that it is a receptor-C5a interaction that leads to stimulation of these cellular responses. PMX205 have been shown to be effective in causing a significant reduction in fibrillar amyloid deposits and activated glia in two mouse models of Alzheimer’s disease. PMX205 -treated rats exhibited reduced striatal lesion size, apoptosis, neutrophil infiltration, and hemorrhage. PMX205 is used as anti-inflammatory drug. PMX205 significantly prevented DSS-induced colon inflammation, and dealed with PMX205, subjected rats had lower pro-inflammatory. Additionally, the levels of anti-inflammatory cytokines IL-4 and IL-10 were increased. PMX205 did not affect C5a’s levels. The positive effect of PMX205 was seen in two strains of mice of differing sensitivities to DSS inflammation. Pharmacological inhibition of C5a activity by PMX205 is efficacious in preventing DSS-induced colitis.