FDA Expands Mavacamten Indication to Pediatric Obstructive HCM Patients

Mavacamten (Camzyos) is now approved by the US Food and Drug Administration for use not only in adults, but also in pediatric patients with obstructive hypertrophic cardiomyopathy (HCM) who weigh at least 30 kg, Bristol Myers Squibb announced yesterday.

“The FDA approval of Camzyos for pediatric patients with symptomatic obstructive hypertrophic cardiomyopathy represents a landmark moment for pediatric cardiology. For the first time, children with this serious condition have a therapy that is FDA-approved to reduce left ventricular outflow tract obstruction,” Joseph Rossano, MD (Children’s Hospital of Philadelphia, PA), principal investigator of SCOUT-HCM, said in a press release.

The SCOUT-HCM trial formed the basis for the regulatory decision. The trial enrolled 44 symptomatic adolescents (ages 12 to < 18 years) with NYHA class II or III obstructive HCM, randomizing them to receive mavacamten (2 or 5 mg daily based on body weight) or placebo. Mean Valsalva left ventricular outflow tract (LVOT) gradient at baseline was similar in the two groups. Change in LVOT gradient between baseline and week 28, the study’s primary endpoint, was greater in the mavacamten versus placebo group, with a least-squares mean difference of −48.0 (P < 0.0001).

Data also indicated improvements in resting and postexercise LVOT gradients, maximal LV wall thickness, and average E/e’. An exploratory analysis looking at biomarker changes with mavacamten found reductions in NT-proBNP as well as troponin I and T. Safety measures did not differ between the study arms. 

Kenneth B. Margulies, MD (Penn Medicine, Philadelphia, PA), who served as the discussant for SCOUT-HCM when it was presented by Rossano at this year’s American College of Cardiology meeting, told attendees that the “results will surely change clinical practice.”

While there have been several trials of cardiac myosin inhibitors in this disease state, SCOUT-HCM stands out for its adolescent participants, said Margulies. “Your presentation and your study remind us that there’s a whole other world of individuals who need their own studies in these broader areas, and that’s our pediatric populations.”

In 2022, the FDA approved the cardiac myosin inhibitor for use in adults with NYHA class II or III obstructive HCM based on the EXPLORER-HCM trial. Since then, a second cardiac myosin inhibitor, aficamten (Myqorzo; Cytokinetics) also got the FDA’s green light for the condition, but the drug has not yet received an expanded indication in younger patients. Aficamten also has shown promise in the setting of nonobstructive HCM, as reported by TCTMD.