Mavacamten in Adolescents with Obstructive Hypertrophic Cardiomyopathy

Mavacamten in Adolescents with Obstructive Hypertrophic Cardiomyopathy Published March 29, 2026 N Engl J Med 2026;395:362-373 DOI: 10.1056/NEJMoa2601103 Abstract Background Approved pharmacologic therapies for pediatric hypertrophic cardiomyopathy are lacking, and surgical intervention may be indicated in patients with left ventricular outflow tract obstruction. The efficacy and safety of mavacamten, a cardiac myosin inhibitor that is available for adults, warrant evaluation in adolescents. Methods We conducted a phase 3, double-blind, randomized, placebo-controlled trial involving symptomatic adolescents (12 to <18 years of age) with New York Heart Association class II or III obstructive hypertrophic cardiomyopathy. The patients were randomly assigned in a 1:1 ratio to receive mavacamten or placebo. The primary end point was the change from baseline to week 28 in left ventricular outflow tract pressure gradient provoked by the Valsalva maneuver. Results A total of 44 patients underwent randomization; 23 patients (8 [35%] of whom were female) were assigned to mavacamten group, and 21 (5 [24%] of whom were female) were assigned to the placebo group. The mean (±SD) age of the patients was 14.7±1.7 years in the mavacamten group and 14.6±1.7 years in the placebo group, and the mean Valsalva left ventricular outflow tract gradient at baseline was similar in the two groups (78.4±34.1 mm Hg and 80.8±47.4 mm Hg, respectively). At week 28, the least-squares mean change in the Valsalva left ventricular outflow tract gradient was −48.5 mm Hg in the mavacamten group and −0.5 mm Hg in the placebo group (difference, −48.0 mm Hg; 95% confidence interval, −67.7 to −28.3; P<0.001). The incidence of adverse events was similar in the two groups. Two patients in each group had serious adverse events; in the mavacamten group, 1 patient had two episodes of syncope, and another had an inappropriate shock delivered by an implantable cardioverter–defibrillator; in the placebo group, 1 patient had chest pain, and another had depression with suicidal ideation. No patient had a reduction in the left ventricular ejection fraction to less than 50%. No deaths occurred during the trial. Conclusions Among adolescent patients with obstructive hypertrophic cardiomyopathy, the reduction in left ventricular outflow tract obstruction was significantly greater with mavacamten than with placebo over a 28-week period. (Funded by Bristol Myers Squibb; SCOUT-HCM ClinicalTrials.gov number, NCT06253221.) Are you a member of an institution such as a university or hospital?Learn more about Institutional Access Notes This article was published on March 29, 2026, at NEJM.org. A data sharing statement provided by the authors is available with the full text of this article at NEJM.org. Supported by Bristol Myers Squibb. Disclosure forms provided by the authors are available with the full text of this article at NEJM.org. We thank the patients and families who made this trial possible, the trial teams from the participating sites, and Thomas Crighton, Ph.D., of Oxford PharmaGenesis for medical writing and editorial support (funded by Bristol Myers Squibb) on earlier versions of the manuscript. Supplementary Material Information & Authors Information Published In Copyright Copyright © 2026 Massachusetts Medical Society. All rights reserved. For personal use only. Any commercial reuse of NEJM Group content requires permission. History Published online: March 29, 2026 Published in issue: July 23, 2026 Topics Authors Metrics & Citations Metrics Altmetrics Citations Export citation Select the format you want to export the citation of this publication. Cited by - Mavacamten in adolescent obstructive hypertrophic cardiomyopathy: SCOUTing a way forward, Heart Failure Reviews, 31, 1, (2026).https://doi.org/10.1007/s10741-026-10655-x - Significance of the Echocardiographic Assessment of Longitudinal Left Ventricular Systolic Function in Children and Adolescents with Hypertrophic Cardiomyopathy, Journal of Clinical Medicine, 15, 13, (4911), (2026).https://doi.org/10.3390/jcm15134911 - Medical management of hypertrophic cardiomyopathy, Indian Heart Journal, (2026).https://doi.org/10.1016/j.ihj.2026.06.005 - What Are Heart Failure With Preserved Ejection Fraction Mimics and What Are They Mimicking? Insights Into Our Conceptualization of Heart Failure With Preserved Ejection Fraction as a Disease, Journal of Cardiac Failure, (2026).https://doi.org/10.1016/j.cardfail.2026.05.016 Loading...