The present invention refers to muteins of the C5a anaphylatoxin (C5a) which are C5a receptor antagonists, to nucleic acid molecules comprising a nucleotide sequence encoding such muteins of C5a anaphylatoxin, to host cells containing a nucleic acid molecule comprising a nucleotide sequence encoding such muteins of the C5a anaphylatoxin as well as to a pharmaceutical composition comprising a mutein of the C5a anaphylatoxin acting as a C5a receptor antagonists. A mutein of the invention is a C5a receptor antagonist wherein the amino acid residue naturally occurring at sequence position 69 is mutated.