Peptide antagonists of the calcitonin CGRP family of peptide hormones and their use

A calcitonin gene-related peptide antagonist, or a pharmaceutically acceptable salt thereof, said antagonist having the structure of Formula I:

• X1—Y1—Z1 (I)
• wherein:
• X1 is a modified N-terminal fragment of calcitonin gene-related peptide comprising from five to seven amino acid residues, wherein exactly two amino acids of the N-terminal fragment are cysteine (Cys) residues, wherein the C-terminal amino acid residue of the N-terminal fragment is cysteine (Cys), wherein the residue immediately preceding the C-terminal Cys residue of the N-terminal fragment is a non-threonine substitution of threonine, wherein the two cysteine residues are separated by four, five or six amino acids and wherein the two cysteine residues can form a disulfide bond;
• Y1 is selected from the group consisting of Val-Leu-Gly-Arg-Leu-Ser-Gln-Glu-Leu-His-Arg-Leu-Gln-Thr-Tyr-Pro-Thr-Asn (SEQ ID NO:59) and Val-Leu-Gly-Arg-Leu-Ser-Gln-Glu-Leu-His-Arg-Leu-Gln-Thr-Tyr-Pro-Val-Asp (SEQ ID NO:60);
• and
• Z1 is selected from the group consisting of Thr-Gly-Ser-Gly-Thr-Pro-NH2 (SEQ ID NO:62), Pro-Ser-Ser-Pro-His-Ser-Tyr-NH2 (SEQ ID NO:63) and Val-Gly-Ser-Lys-Ala-Phe-NH2 (SEQ ID NO:46).