Cardiac Myosin Inhibitors in the Treatment of Hypertrophic Cardiomyopathy: Clinical Trials and Future Challenges.

Hypertrophic cardiomyopathy (HCM) is a prevalent and often underdiagnosed genetic cardiac disorder characterized by left ventricular hypertrophy and, in many cases, dynamic left ventricular outflow tract obstruction (LVOTO). The development of cardiac myosin inhibitors (CMIs) represents an emerging therapeutic approach in the pharmacological management of obstructive HCM (oHCM). This review offers an integrated and up-to-date synthesis of the cardiac myosin inhibitor class, with a focus on mavacamten, aficamten, and the broader landscape of emerging agents. It also highlights recent clinical trial outcomes, pharmacokinetic and pharmacogenetic considerations, and potential future directions in therapy. Furthermore, we incorporate the most recent data up to May 2025, including late-breaking trial results and real-world safety findings, aiming to provide clinicians with a practical and comprehensive perspective on this evolving drug class. A narrative review was conducted by systematically searching PubMed, Scopus, Google Scholar, and ClinicalTrials.gov for English-language articles and trials published between January 2016 and May 2025. Keywords included "cardiac myosin inhibitor", mavacamten", "aficamten", "MYK-224", and "hypertrophic cardiomyopathy." Inclusion criteria encompassed clinical trials and comprehensive reviews specifically addressing CMIs in cardiac applications. CMIs such as mavacamten and aficamten have demonstrated significant clinical benefits in reducing LVOT gradients, improving exercise capacity, and alleviating symptoms in patients with oHCM. Mavacamten is currently approved for clinical use, while aficamten is in advanced regulatory review. Comparative data suggest potential advantages of aficamten in the onset of action, pharmacokinetic profile, and tolerability. Emerging evidence supports the exploration of CMIs in pediatric populations, heart failure with preserved ejection fraction (HFpEF), and non-obstructive HCM (nHCM), although results are still preliminary. Cardiac myosin inhibitors offer a novel, pathophysiology-targeted approach to managing oHCM. While mavacamten has established efficacy, next-generation agents like aficamten may offer improved safety and versatility. Further long-term studies are needed to clarify their role across broader patient populations.