The invention relates to a C5a receptor antagonist of structure (I), wherein X1 is a radical having a mass of about 1-300 and stands for R5-, R5-CO—, R5-N(R6)-CO—, R5-O—CO—, R5-SO2—, R5-N(R6)-SO2—, R5-N(R6)-, R5-N(R6)-CS—, R5-N(R6)-C(NH)—, R5-CS—, R5-P(O)OH—, R5-B(OH)— or R5-CH═N—O—CH2—CO—, wherein R5/R6 represent H, F, hydroxy, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, heterocyclyl, substituted heterocyclyl, arylalkyl, substituted arylalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, acyl, substituted acyl, alkoxy, alkoxyalkyl, substituted alkoxyalkyl, aryloxyalkyl or substituted aryloxyalkyl; X2=radical (biological bonding properties of a mimicrying phenylalanine unit); X3/X4=spacer (amino acids, amino-acid analogs and amino-acid derivatives); X5=radical (biological bonding properties of a mimicrying cyclohexylalanine or homoleucine unit); X6=radical (biological bonding properties of a mimicrying tryptophan unit); X7=radical (biological bonding properties of a mimicrying norleucine or phenylalanine unit), a chemical bond being formed between X3 and X7.