Additionally, clinical trials of HDAC inhibitors have revealed numerous adverse reactions in patients, including thrombocytopenia-induced bleeding, neutropenia-induced susceptibility to infections, anemia due to hemoglobin reduction, arrhythmias, myocardial hypertrophy, and neurotoxicity, which also pose major limitations in the development of HDAC inhibitors (262). Here, HDAC9 is linked to cardiac hypertrophy.