Mavacamten reduced left ventricular outflow tract obstruction more than placebo in adolescents with symptomatic obstructive hypertrophic cardiomyopathy

1. Mavacamten reduced the Valsalva left ventricular outflow tract (LVOT) gradient more than placebo at week 28 in adolescents with symptomatic obstructive hypertrophic cardiomyopathy.

2. Adverse event incidence was similar between groups; no patient had a left ventricular ejection fraction below 50%, and no deaths occurred.

Evidence Rating Level: 1 (Excellent)

2MM Brief: Rossano and colleagues evaluated mavacamten, a cardiac myosin inhibitor available for adults, in adolescents with symptomatic obstructive hypertrophic cardiomyopathy, for which approved pharmacologic therapies are lacking. The phase 3 SCOUT-HCM trial was a double-blind, randomized, placebo-controlled study of patients 12 to less than 18 years of age with New York Heart Association (NYHA) class II or III disease. Forty-four patients were randomized in a 1:1 ratio: 23 received mavacamten and 21 received placebo. The primary end point was the change from baseline to week 28 in the LVOT pressure gradient provoked by the Valsalva maneuver. At week 28, the least-squares mean change in the Valsalva LVOT gradient was -48.5 mm Hg with mavacamten and -0.5 mm Hg with placebo, for a between-group difference of -48.0 mm Hg (95% confidence interval, -67.7 to -28.3; P<0.001). Mean age was 14.7±1.7 years in the mavacamten group and 14.6±1.7 years in the placebo group. Adverse events occurred at similar incidence in the 2 groups. Two patients in each group had serious adverse events: in the mavacamten group, 1 patient had 2 episodes of syncope and another had an inappropriate implantable cardioverter-defibrillator shock; in the placebo group, 1 patient had chest pain and another had depression with suicidal ideation. No patient had a reduction in left ventricular ejection fraction to less than 50%, and no deaths occurred during the trial. The study was small and evaluated the primary outcome over 28 weeks; the supplied company announcement described 56-week data, but the journal abstract reported results through week 28. These findings indicate that mavacamten reduced LVOT obstruction more than placebo in this adolescent population, although longer-term safety and efficacy require further evaluation.

Click here to read the study in the NEJM (New England Journal of Medicine)

Citation: Rossano JW, Canter C, Wolf CM, Papez A, Gambra M, Bryant RM, et al. Mavacamten in Adolescents with Obstructive Hypertrophic Cardiomyopathy. N Engl J Med. 2026 Jul 23;395(4):362-373. doi: 10.1056/nejmoa2601103. Epub 2026 Mar 29. PMID: 41910394.

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