The present invention relates to a peptide derivative selected from the group consisting of PEG20k(AL)-&bgr-Ala-Tyr-Nal(1)-Leu-Phe-Arg-Pro-Arg-Asn-NH2, PEG20k(AL)-&bgr-Ala-Tyr-Nal(2)-Leu-Phe-Arg-Pro-Arg-Asn-NH2, PEG20k(AL)-NpipAc-Tyr-Nal(2)-Leu-Phe-Arg-Pro-Arg-Asn-NH2, PEG20k(AL)-NpipAc-Tyr-Nal(2)-Leu-Phe-Arg-Ala-Arg-Asn-NH2, PEG20k(AL)-PEG(2)-Tyr-Nal(2)-Leu-Phe-Arg-NMeAla-Arg-Asn-NH2, PEG20k(AL)-Pic(4)-Tyr-Nal(2)-Leu-Phe-Arg-NMeAla-Arg-Asn-NH2, PEG20k(AL)-Acp-Tyr-Nal(2)-Leu-Phe-Arg-NMeAla-Arg-Asn-NH2, and PEG20k(AL)-&bgr-Ala-Tyr-Nal(2)-Leu-Pya(4)-Arg-Pro-Arg-Asn-NH2 or a salt thereof.La presente invención se refiere a un derivado peptídico seleccionado del grupo que consiste en PEG 20k(AL)-ß-Ala-Tyr-Nal(1)-Leu-Phe-Arg-Pro-Arg-Asn-NH2, PEG20k(AL)-ß-Ala-Tyr-Nal(2)-Leu-Phe-Arg-Pro-Arg-Asn-NH2, PEG20k(AL)-NpipAc-Tyr-Nal(2)-Leu-Phe-Arg-Pro-Arg-Asn-NH2, PEG20k(AL)-NpipAc-Tyr-Nal(2)-Leu-Phe-Arg-Ala-Arg-Asn-NH2, PEG20k(AL)-PEG(2)-Tyr-Nal(2)-Leu-Phe-Arg-NMeAla-Arg-Asn-NH2, PEG20k(AL)-Pic(4)-Tyr-Nal(2)-Leu-Phe-Arg-NMeAla-Arg-Asn-NH2, PEG20k(AL)-Acp-Tyr-Nal(2)-Leu-Phe-Arg-NMeAla-Arg-Asn-NH2,and PEG20k(AL)-ß-Ala-Tyr-Nal(2)-Leu-P ya(4)-Arg-Pro-Arg-Asn-NH2 o una sal de los anteriores.
