[Trp63, 64]-C3a (63-77)

[Trp63, 64]-C3a (63-77), synthetic superagonist analog of complement 3a, exhibited the greatest biological potency of all peptides tested. The peptide was 12-15 times more active than natural C3a. Such an optimal potency was obtained by introducing a bulky hydrophobic group such as Trp-Trp which binds more strongly to the hydrophobic site on the receptor than does the corresponding site on the natural ligand.