SCOUT-HCM: Mavacamten Achieves Positive Results in Adolescents with Obstructive HCM

On January 12, 2026, Bristol Myers Squibb announced positive topline results from the phase 3 SCOUT-HCM trial evaluating mavacamten for adolescent patients ages 12 to <18 with symptomatic obstructive hypertrophic cardiomyopathy (oHCM).1

The trial, which is the first study of a cardiac myosin inhibitor (CMI) in this patient group, demonstrated a statistically significant reduction in baseline Valsalva left ventricular outflow tract (LVOT) gradient by week 28 versus placebo. Additionally, the trial saw statistical significance for several secondary endpoints.1

“Adolescent oHCM is a serious, rare disease associated with substantial morbidity and mortality,” Cristian Massacesi, MD, executive vice president, chief medical officer, and head of development at Bristol Myers Squibb, said in a statement. “The SCOUT-HCM topline results highlight the potential for [mavacamten] to be the first cardiac myosin inhibitor for adolescent patients with oHCM. [Mavacamten] has redefined the treatment paradigm for symptomatic oHCM in adults, with over 20,000 patients started in the US alone, and we look forward to the potential opportunity to transform clinical care in the adolescent patient population.”1

SCOUT-HCM was a randomized, double-blind, placebo-controlled study conducted at 47 locations internationally. Patients were eligible for enrollment if they had a diagnosis of HCM and exhibited LVOT obstruction or other symptoms. Patients were excluded if they exhibited phenocopy diseases resulting in myocardial hypertrophy unrelated to sarcomere dysfunction or had evidence of LVEF <50% in the 6 months prior to the study, among other criteria.2

The primary endpoint for SCOUT-HCM was change from baseline in Valsalva LVOT gradient by week 28. Secondary outcomes included change from baseline in resting LVOT gradient, change from baseline in post-exercise peak LVOT gradient, change from baseline in maximal wall thickness, and change from baseline in the ratio between early mitral inflow velocity and mitral annular early diastolic velocity, among others.2

The study consisted of 5 main periods: screening, a double-blind, placebo-controlled period, an active-treatment period, a long-term extension period, and a follow-up period. Patients initiated mavacamten treatment at 2.5 or 5 mg, depending on body weight at visit, which was then titrated to 1, 2.5, 5, 10, or 15 mg based on echocardiographic assessments of Valsalva LVOT gradient and LVEF. Patients who completed the active-treatment period would continue to the long-term extension period for ≤144 weeks, during which they would continue to receive the same dose of mavacamten or matching placebo.3

In addition to a statistically significant reduction in Valsalva LVOT, mavacamten also exhibited safety results consistent with the drug’s established safety profile. No new safety signals were recorded in this younger population.1

“The SCOUT-HCM study is important for patients and the field of pediatric cardiology, being one of the very few pediatric cardiology randomized and placebo-controlled clinical trials that has generated positive Phase 3 results,” Joseph Rossano, MD, principal investigator and chief of the division of cardiology at the Children’s Hospital of Philadelphia, said in a statement. “Treatment options for adolescents with oHCM are currently limited to medical symptom management or invasive surgery.”1

SCOUT-HCM is still ongoing, continuing both active treatment and long-term extension periods. In the statement, Bristol Myers Squibb also announced plans to present detailed results from SCOUT-HCM at an upcoming medical congress.1

References

1. Bristol Myers Squibb. Bristol Myers Squibb Announces Positive Topline Results from Phase 3 SCOUT-HCM Trial Evaluating Camzyos (mavacamten) in Adolescents with Symptomatic Obstructive Hypertrophic Cardiomyopathy (oHCM). January 12, 2026. Accessed January 12, 2026. https://news.bms.com/news/details/2026/Bristol-Myers-Squibb-Announces-Positive-Topline-Results-from-Phase-3-SCOUT-HCM-Trial-Evaluating-Camzyos-mavacamten-in-Adolescents-with-Symptomatic-Obstructive-Hypertrophic-Cardiomyopathy-oHCM/default.aspx

2. Bristol Myers Squibb. A Study to Evaluate Mavacamten in Adolescents With Symptomatic Obstructive Hypertrophic Cardiomyopathy. ClinicalTrials.gov Identifier: NCT06253221. Updated December 19, 2025. Accessed January 12, 2026. https://www.clinicaltrials.gov/study/NCT06253221

3. Rossano J, Canter C, Wolf C, et al. Mavacamten in symptomatic adolescent patients with obstructive hypertrophic cardiomyopathy: Design of the phase 3 scout-HCM trial. American Heart Journal. 2025;292:107283. doi:10.1016/j.ahj.2025.107283