PROBLEM TO BE SOLVED: To provide an insulinotropic peptide with its N-terminal amino acid modified and a pharmaceutical composition comprising the same.SOLUTION: This invention provides exendin-4 having R1-X-R2 structure [R1 is beta-hydroxy imidazopropionyl. R2 is -NH2 or -OH. X is Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Y-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Z-Asn-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser, or Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Y-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Z-Asn-Gly-Gly (Y and Z are Lys, Ser or Arg)].【課題】N末端アミノ酸が変性したインスリン分泌ペプチド及びこれを含む薬剤学的組成物の提供。【解決手段】R1-X-R2の構造を有するエキセンディン-4。[R1はベータ-ヒドロキシイミダゾプロピオニル。R2は-NH2又は-OH。XはGly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Y-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Z-Asn-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser、又はGly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Y-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Z-Asn-Gly-Gly(Y、ZはLys、Ser又はArg)]【選択図】なし