A fragment peptide having an appropriate length composed of a part of the HMGB1 protein was synthesized, and it was confirmed that the peptide exhibited a myocardial infarction therapeutic effect.HMGB1タンパク質の一部からなる適切な長さを持つ断片ペプチドを合成し、当該ペプチドが心筋梗塞治療効果を示すことを確認した。