600818 Disclosed is a cyclic organic compound, comprising the amino acid sequence GQRETPEGAEAKPWY in addition to one or two further amino acids, characterized in that it has no carboxyl group C-terminally and/or no amino group N-terminally, wherein the ring closure is formed between a side chain of one amino acid and the C-terminus of another amino acid, or the ring closure is effected with the aid of a nonnatural amino acid, and wherein one of the amino acids is a nonnatural amino acid, selected from ornithine or an omega-amino acid, or the cyclic organic compound is a compound of SEQ ID NO: 1.