The present inventors have found that HMGB1 fragment peptides having a particular amino acid sequence exhibit the effects of improvement of cardiac function, inhibition of cardiomyocyte hypertrophy, inhibition of myocardial fibrosis, and promotion of angiogenesis in an animal model of dilated cardiomyopathy, that the particular HMGB1 fragment peptides also exhibit the effects of improvement of cardiac function, inhibition of cardiomegaly, inhibition of cardiomyocyte hypertrophy, inhibition of myocardial fibrosis, and promotion of angiogenesis in an animal model of ischemic cardiomyopathy caused by old myocardial infarction, and that the particular HMGB1 fragment peptides exhibit the effects of inhibition of cardiomyocyte hypertrophy and inhibition of myocardial fibrosis in an animal model of hypertensive cardiomyopathy. Based on these findings, pharmaceutical compositions are provided for the prevention and/or treatment of cardiomyopathy and old myocardial infarction and chronic heart failure resulting therefrom, which comprise an HMGB1 fragment peptide having a particular amino acid sequence.
