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.