The present invention relates to derivates of an insulinotropic peptideExendin-4 andpharmaceutically acceptable salts produced thereof, which are useful for thetreatment of type IIdiabetes. Exendin-4 has the chemical structure as shown below:His-Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Lys-Gln-X-Glu-Glu-Glu-Ala-Val-Y-Leu-Phe-Ile-Glu-Trp-Leu-Lys-Asn-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser-ZIn which:X represents Arg, Leu or Ile, Y represents His, Arg or Lys and Z representsArg-OH, -OH,-NH2 or Lys-OH.The derivates of this invention may be prepared by synthetic chemical means,and moreeasily, by the recombinant techniques, which makes it possible to commercialproduction.