A cyclic peptide of forumula (I) X1-GQRETPEGAEAKPWY-X2, wherein X1 comprises an amino acid (sequence) with 1 to 4 members, including natural or unnatural amino acids, and X2 comprises a natural amino acid, and wherein X1 contains the N-terminal amino acid on the left in position 1, and X2 contains the C-terminal amino acid in the last position on the right, in the form of a lyophilisate without additives and/or stabilizers and the use thereof.