Abstract Body: Background and aims: Set7 can affect gene expression and activity of proteins. We demonstrated that Set7 deletion attenuates isoproterenol-induced cardiac fibrosis and dysfunction. However, the biological mechanisms by which the loss of Set7 mediates these effects are unknown. Here, we investigated the effect of a pharmacological inhibitor targeting Set7 (sinefungin) in cardiac disorders caused by isoproterenol. Additionally, we used an AAV9-delivered CRISPR/Cas9-mediated somatic mutagenesis approach to deplete Set7 specifically in cardiomyocytes. Methods: Male C56BL/6 mice were injected with vehicle (Veh), isoproterenol (Iso) for 14 days, or isoproterenol for 7 days followed by combined treatment with isoproterenol and sinefungin for additional 7 days (Iso+Sine). AAV-cTNT-Cre or AAV-U6gRNA1-U6gRNA2-cTNT-Cre vectors were produced and injected into P1 RosaCas9GFP mice. After 8 weeks, mice were injected with vehicle or isoproterenol. Results: Sinefungin prevented the increase in heart weight to tibia length (HW/TL) ratio, cardiomyocyte area and myocardial fibrosis induced by isoproterenol. Iso mice showed a reduced ejection fraction and fractional shortening compared to Veh mice. Interestingly, Iso+Sine mice displayed an increase in ejection fraction and fractional shortening compared to Iso mice, suggesting that sinefungin prevented systolic dysfunction elicited by isoproterenol. qPCR analysis evidenced that Set7 mRNA expression was 70% reduced in the heart of AAV-Set7 mice. AAV9-control mice injected with isoproterenol displayed an increased HW/TL ratio and reduced ejection fraction; similar results were found in AAV9-Set7 mice, suggesting that cardiomyocyte-specific Set7 depletion does not influence cardiac hypertrophy and systolic dysfunction in response to isoproterenol. Conclusion: Our data suggest that Set7 pharmacological inhibition prevents isoproterenol-induced cardiac remodeling and systolic dysfunction. In addition, Set7 depletion specifically in cardiomyocytes does not affect cardiac hypertrophy and dysfunction in response to isoproterenol. Further experiments are required to determine by which biological mechanisms Set7 influences isoproterenol-induced cardiac disorders.