Mavacamten Sustainably Reduces LVOT Gradient in Pediatric oHCM Over 56 Weeks

Mavacamten sustainably reduced left ventricular outflow tract (LVOT) obstruction in pediatric patients with obstructive hypertrophic cardiomyopathy (oHCM) with a favorable safety profile, according to long-term data from SCOUT-HCM.1

These data were presented at the American Heart Association (AHA) Scientific Sessions 2026 in Chicago, Illinois, by Joseph Rossano, MD, MS, co-director of the cardiac center, chief of the division of cardiology, and associate chair for external affairs at Children’s Hospital of Philadelphia. In an exclusive interview with HCPLive, Rossano explained his thoughts on mavacamten’s regulatory approval and the next steps for investigators to take.1

“I think that what mavacamten has done for hypertrophic cardiomyopathy in children is really foundational and paradigm-changing,” Rossano told HCPLive. “For the first time, we have a medication that’s really targeted for the underlying pathophysiology, and we have very good data from children with the disorder.”

SCOUT-HCM was a randomized, double-blind, placebo-controlled study evaluating mavacamten in patients aged 12 to <18 years with symptomatic oHCM. The only eligibility criteria for the trial were a diagnosis of HCM and presence of LVOT obstruction and symptoms. Patients with phenocopy diseases resulting in myocardial hypertrophy unrelated to sarcomere dysfunction, as well as left ventricular ejection fraction <50% in the 6 months prior to enrollment, were excluded.2

Patients were randomly assigned in a 1:1 ratio to receive either mavacamten or placebo, both at a range of 1 to 15 mg. The primary endpoint was change from baseline in Valsalva LVOT gradient at week 28, while secondary outcomes included change from baseline in resting LVOT gradient, maximal wall thickness, post-exercise peak LVOT gradient, and early mitral inflow velocity and mitral annular early diastolic velocity, among others.2,3

A total of 44 patients were enrolled in the study, of whom 23 were assigned to mavacamten and 21 to placebo. The mean age was 14.7 (+/- standard deviation [SD], 1.7) years in the mavacamten arm and 14.6 +/- 1.7 years in the placebo arm. By week 28, the least-squares mean change in Valsalva LVOT gradient was -48.5 mmHg in the mavacamten arm and -0.5 mmHg in the placebo arm (difference, -48 mmHg; 95% CI, -67.7 to -28.3; P <.001). The incidence of adverse events was similar between both groups.3

Rossano and colleagues then began the present active-treatment phase out to 56 weeks. Patients assigned to mavacamten initially continued treatment, while those assigned to placebo crossed over to 2.5 mg or 5 mg mavacamten daily, depending on body weight. The exploratory efficacy endpoints for this portion of the trial included changes from baseline or week 28 to week 56 in Valsalva and resting LVOT gradients and maximal wall thickness, among others.1

Of the 44 patients initially included, 43 completed the initial 28-week double-blind, placebo-controlled period and entered the active-treatment phase. Mean change from baseline to week 56 in Valsalva LVOT gradient was -48.1 mmHg in the treatment arm, while change from week 28 to 56 was -35.1 mmHg in the placebo-mavacamten arm. The team also recorded improvements in other efficacy endpoints, which were carried over from the placebo-controlled phase.1

Ultimately, Rossano and colleagues determined that mavacamten successfully and safely reduced LVOT gradient over a long period of time, with a favorable safety profile. Rossano went on to discuss the next steps for investigating mavacamten in a real-world setting following its earlier regulatory approval for this population.1

“We need to understand how the medication does in a larger group of patients, and I think that will be a very important part of the studies to come,” Rossano said. “We should get a very good sense of what the safety of the medication is, and somewhat of the efficacy of the medication, through the REMS program, but I think we really need other mechanisms to get more granular data to really understand the potential benefit and risks of the medication.”

Editors’ Note: Rossano reports disclosures with AskBio, Astellas, Bayer, Bristol Myers Squibb, CRI Biotech, and Merk.

References

1. Aronson R, Canter C, Desai M, et al. Outcomes of mavacamten treatment in pediatric patients with obstructive hypertrophic cardiomyopathy at 56 weeks: the SCOUT-HCM trial. Presented at the American Heart Association (AHA) Scientific Sessions 2026, Chicago, IL. November 6-9, 2026.

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 November 11, 2026. https://clinicaltrials.gov/study/NCT06253221

3. Rossano JW, Canter C, Wolf CM, et al. Mavacamten in Adolescents with Obstructive Hypertrophic Cardiomyopathy. N Engl J Med. 2026 Jul 23;395(4):362-373. doi: 10.1056/NEJMoa2601103