N Engl J Med

ACC 2026: Mavacamten shows promise in adolescents with obstructive hypertrophic cardiomyopathy

March 31, 2026

Clinical takeaway: Mavacamten represents the first cardiac myosin inhibitor evaluated in adolescents with obstructive hypertrophic cardiomyopathy and may offer a pharmacologic alternative to surgical intervention in this population with significant unmet need.

The phase 3 SCOUT-HCM trial, published in NEJM and presented at ACC.26, demonstrated that mavacamten significantly reduced left ventricular outflow tract obstruction in symptomatic adolescents aged 12 to 17 years with NYHA Class II-III obstructive hypertrophic cardiomyopathy. In this randomized, double-blind, placebo-controlled study of 44 patients, mavacamten reduced the Valsalva left ventricular outflow tract gradient by 48.5 mm Hg compared with 0.5 mm Hg with placebo at 28 weeks (difference −48.0 mm Hg; 95% CI, −67.7 to −28.3; p<0.001).

Secondary analyses suggested improvements in multiple cardiac parameters, including resting and post-exercise gradients, diastolic function, left ventricular wall thickness, NYHA functional class, and biomarkers of cardiac stress. The safety profile was similar to that observed in adult trials, with no patients experiencing a reduction in left ventricular ejection fraction below 50% and no deaths during the trial. Adolescent participants had more severe disease at baseline than adults in the EXPLORER-HCM trial, with higher outflow tract gradients and greater left ventricular wall thickness.

Source:

Rossano JW, et al; SCOUT-HCM Investigators. (2026, March 29). N Engl J Med. Mavacamten in Adolescents with Obstructive Hypertrophic Cardiomyopathy. https://www.nejm.org/doi/full/10.1056/NEJMoa2601103