A compound having the formula R1-X-Z-R2 in which R1 is hydrogen, C1-4 alkyl, acetyl, formyl, benzoyl or trifluoroacetyl； R2 is OH or NH2； X is a peptide having the formula I, His-Ser-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Arg-Ala-Arg-Ala-Asp- Asp-Phe-Val-Ala-Trp-Leu-Lys-Glu-Ala or differs from Formula I in up to 4 of the following positions, according to which, if it is different from Formula I: the residue in position 2 is select from: Aib, D-Ser； the residue in position 16 is: Lys, Asp, Glu； the residue in position 18 is selected from: Lys, His, Ala, Ser, Tyr； the residue in position 20 is selected from: Gin, His, Lys, Arg, Glu； the residue in position 21 is: Glu； the residue in position 24 is selected from: Gin, Leu, Glu, Lys, Arg, Asp； the residue in position 27 is selected from: Met, Cys, Arg, Glu, Leu； the residue in position 28 is selected from: Asn, Ser, Arg, Lys, Ala, Leu, Glu, Asp； and the residue at position 29 is selected from: Thr, Glu, Lys； and Z is absent or is a sequence of 1-20 amino acid units selected from the group consisting of Ala, Leu, Ser, Thr, Tyr, Cys, Glu, Lys, Arg, Dbu, Dpr and Orn； or a pharmaceutically acceptable salt thereof. with the proviso that X is not His-Ser-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Arg-Ala-Arg-Ala- Asp-Asp- Phe-Val-Ala-Trp-Leu-Lys-Ser-Thr.Un compuesto que tiene la fórmula R1-X-Z-R2 en la que R1 es hidrógeno, alquilo C1-4, acetilo, formilo, benzoílo o trifluoroacetilo； R2 es OH o NH2； X es un péptido que tiene la fórmula I, His-Ser-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Arg-Ala-Arg- Ala-Asp-Asp-Phe-Val-Ala-Trp-Leu-Lys-Glu-Ala o difiere de la Fórmula I en hasta 4 de las siguientes posiciones, según lo cual, si es diferente de la Fórmula I: el residuo en la posición 2 se selecciona de: Aib, D-Ser； el residuo en la posición 16 es: Lys, Asp, Glu； el residuo en la posición 18 se selecciona de: Lys, His, Ala, Ser, Tyr； el residuo en la posición 20 se selecciona de: Gin, His, Lys, Arg
