Treatments for gastrointestinal disorders

A peptide or a pharmaceutically acceptable salt thereof, wherein the peptide comprises the amino acid sequence

• Xaa1 Xaa2 Xaa3 Xaa4 Cys5 Xaa6 Xaa7 Xaa8 Cys9 Asn10 Pro11 Ala12 Cys13 Xaa14 Gly15 Xaa16 Xaa17 (SEQ ID NO:1), or a pharmaceutically acceptable salt thereof;
• wherein
• Xaa1 is Asn, D-Asn, Gln, D-Gln, Pro, Ala, β-Ala, D-Ala, Val, D-Val, Gly, Thr, D-Thr, Asp, D-Asp, γ-carboxylated Asp, Glu, D-Glu, γ-carboxylated Glu, α-aminosuberic acid (Asu), α-aminoadipic acid (Aad), α-aminopimelic acid (Apm), or is absent;
• Xaa2 is Asp, γ-carboxylated Asp, Glu, γ-carboxylated Glu, Asu, Aad, Apm, or is absent;
• Xaa3 is Asp, γ-carboxylated Asp, Glu, γ-carboxylated Glu, Asu, Aad, Apm, or is absent;
• Xaa4 is Cys or D-Cys;
• Xaa6 is P-Ser, P-Thr, P-homo-Ser, 4-hydroxyvaline phosphate, P-homo-Thr, P-Cys or P-Tyr;
• Xaa7 is Tyr, Leu, Phe or Ile;
• Xaa8 is Cys or D-Cys;
• Xaa14 is Thr, Ala or Phe;
• Xaa16 is Cys or D-Cys;
• and
• Xaa17 is Tyr, D-Tyr, or is absent;
• wherein:
• if Xaa1 is present, Xaa1 may be modified on its amino group by methyl, ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid or octanedioic acid;
• if Xaa1 is absent and Xaa2 is present, then Xaa2 may be modified on its amino group by methyl, ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid or octanedioic acid;
• or
• if both Xaa1 and Xaa2 are absent, then Xaa3 may be modified on its amino group by methyl, ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid or octanedioic acid.