Myosin-ATPase inhibitor in real-world patients with obstructive HCM: a report by the cardiomyopathies and pericardial diseases WG of the Italian Society of Cardiology

Introduction: Approximately two-thirds of patients suffering from hypertrophic cardiomyopathy present with an obstructive (HOCM) physiology. For years, medical therapy has been limited to beta blockers, verapamil and/or disopyramide. Recently, a novel class of drugs, the allosteric inhibitors of the cardiac-specific myosin head adenosine triphosphatase (ATPase), have been demonstrated to be effective in relieving the dynamic obstruction and related clinical condition. In July 2024 the Cardiomyopathies and Pericardial Diseases WG of the Italian Society of Cardiology started with a nationwide multicentre registry aimed at investigating the pathophysiology of dynamic obstruction in real-world patients with HOCM. Based on the medical records, this brief report deals with the proportion of patients who were eligible for Mavacamten based on the Explorer-HCM entry criteria, and then admitted for compassionate use by the end of 2024. Methods and results: The Hypertrophic Obstructive Physiology Study (HOPS) was designed as a registry on consecutive adult patients admitted to 19 tertiary Cardiac Centres in Italy until June 2024. A total of 424 patients, 53% males, aged 64 ± 13 years, were included. We retrospectively recognized 200 Mavacamten-eligible patients (47.2%) on 5 Explorer-HCM requirements. Forty out of this latter group, along with 15 more patients on 4 criteria, were admitted to the compassionate use programme (n = 55, 13% of the whole population). Forty-three showed subaortic obstruction and 12 a mid-ventricular variant. Ethical committee approval items varied among centres and regions. Discussion: This study confirmed our recent demonstration that approximately half of real-world HOCM patients are suitable for Mavacamten therapy based on the full Explorer-HCM trial entry criteria. Due to the current limitation of compassionate use programmes in Italy, only one in four patients was admitted for treatment.