Long-Term Real-World Outcomes of Mavacamten in Symptomatic Obstructive Hypertrophic Cardiomyopathy up to 108 Weeks.

Background/Objectives: Mavacamten is a first-in-class cardiac myosin inhibitor approved for the treatment of symptomatic obstructive hypertrophic cardiomyopathy (HCM). Long-term data regarding its real-world safety and effectiveness are limited. We aimed to describe the real-world experience of mavacamten in a large obstructive HCM cohort at a high-volume HCM center in the United States. Methods: Adult patients initiated on mavacamten between 29 April 2022 and 19 January 2025 at a single HCM center (n = 163) were retrospectively identified. Clinical effectiveness and safety data were collected through 108 weeks of treatment. Results: Rapid and sustained reductions in resting (baseline mean 53.0 ± 36.7 mm Hg to 10.0 ± 11.0 mm Hg) and Valsalva left ventricular outflow tract gradients (baseline mean 79.7 ± 33.2 mm Hg to 16.6 ± 15.4 mm Hg) were observed during treatment throughout the study period along with substantial improvements in New York Heart Association (NYHA) class (75% with >1 NYHA class improvement by Week 12). Mean maximal left ventricular wall thickness significantly decreased (β = 0.01 mm per week). Ten patients (6.1%) required temporary drug interruption due to decrement in left ventricular ejection fraction, and mavacamten was discontinued in six patients (3.7%). Doses of background beta blocker and nondihydropyridine calcium channel blocker were significantly reduced during the study period (p < 0.001). Conclusions: In this large single-center real-world experience of mavacamten therapy, mavacamten was highly effective and maintained an acceptable safety profile, comparable to the clinical trial long-term extension experience.