FDA Approves Camzyos for Teens With Obstructive HCM

FDA on 30 September 2026 approved an expanded indication for Camzyos (mavacamten), Bristol Myers Squibb’s cardiac myosin inhibitor, covering adolescents aged 12 to under 18 with symptomatic obstructive hypertrophic cardiomyopathy. It is the first cardiac myosin inhibitor, and by the company’s account the first drug of any class, approved to treat the disease in pediatric patients — a population that until now had no FDA-approved pharmacologic option beyond off-label use of adult heart-failure drugs or septal reduction surgery.

What changed

Obstructive hypertrophic cardiomyopathy is a genetic heart-muscle disease in which thickened tissue, most often in the septum, narrows the left ventricular outflow tract and obstructs blood leaving the heart. Mavacamten works upstream of that mechanical problem: it is an oral, allosteric inhibitor of cardiac myosin that reduces the excess actin-myosin cross-bridge formation responsible for the heart muscle’s hypercontractility, lowering the outflow obstruction rather than simply slowing the heart or relaxing it with a beta-blocker or calcium-channel blocker.

BMS first won approval for mavacamten in adults with symptomatic NYHA class II–III obstructive HCM in April 2022, the first cardiac myosin inhibitor FDA had cleared for any population. The adolescent supplemental application was accepted for priority review earlier this year, carrying a 30 September 2026 PDUFA target action date — the date on which FDA, in the event, approved it.

The trial behind the approval

The expanded indication rests on SCOUT-HCM, a randomized, double-blind, placebo-controlled Phase 3 trial enrolling 44 adolescents with obstructive HCM. The trial met its primary endpoint: a statistically significant reduction in Valsalva left ventricular outflow tract gradient — the pressure difference measured during a provocative breathing maneuver that is the standard way of quantifying obstruction — at week 28, compared with placebo.

• Reduction in resting LVOT gradient, not just the provoked (Valsalva) measurement.
• Improvement in diastolic function, the heart’s ability to relax and fill between beats.
• Reduction in maximum left ventricular wall thickness.
• Improvement in NYHA functional class, the standard symptom-severity scale.
• Reduced mitral valve dysfunction (systolic anterior motion of the mitral valve), a common secondary feature of obstructive HCM.

On safety, the companies reported no patient falling below a left ventricular ejection fraction of 50% during the trial — the threshold that triggers mavacamten’s core safety concern, drug-induced systolic dysfunction — and no new safety signals relative to the adult trials that supported the original 2022 approval.

Dosing threshold and the REMS

The approved label does not simply extend adult dosing downward by age. It sets a weight floor: patients must weigh at least 30 kilograms (66 pounds) to be eligible, a threshold that in practice will exclude some smaller or younger adolescents within the 12-to-17 age band even though they fall inside the approved age range. Prescribers will need to confirm weight, not just age, before initiating therapy.

Camzyos carries a boxed warning for heart failure due to systolic dysfunction and is available only through the CAMZYOS REMS program, which requires echocardiographic monitoring of left ventricular ejection fraction before starting treatment and at intervals afterward, along with monitoring for interacting drugs metabolized through the same liver enzyme pathway. Coverage of the adolescent approval indicates that framework carries over unchanged to the new population, meaning pediatric cardiology practices prescribing Camzyos will need the same REMS certification and monitoring infrastructure already required for adult prescribers.

Why it matters beyond this label

Pediatric obstructive HCM has historically been managed with drugs developed and labeled for adults — beta-blockers, calcium-channel blockers, disopyramide — used off-label, or with septal reduction procedures (surgical myectomy or alcohol septal ablation) when medical therapy fails to control symptoms. An on-label pharmacologic option carries weight for pediatric cardiologists beyond Camzyos itself: it is a test of whether a mechanism-targeted small molecule, developed and proven first in adults, can be extended to a pediatric population through a comparatively small, single pivotal trial, and it will likely inform how other cardiac myosin inhibitors now in development pursue pediatric indications of their own.

Frequently asked questions

What did FDA approve?

A supplemental New Drug Application expanding the label for Camzyos (mavacamten), Bristol Myers Squibb's cardiac myosin inhibitor, to adolescents aged 12 to under 18 with symptomatic NYHA class II–III obstructive hypertrophic cardiomyopathy. FDA approved the expanded indication on 30 September 2026, the drug's priority-review target action date.

Which adolescent patients are eligible?

Patients aged 12 to under 18 years who weigh at least 30 kilograms (66 pounds) and have symptomatic, NYHA class II or III obstructive hypertrophic cardiomyopathy.

What evidence supported the approval?

The Phase 3 SCOUT-HCM trial, a randomized, double-blind, placebo-controlled study in 44 adolescents with obstructive HCM, which met its primary endpoint of a statistically significant reduction in Valsalva LVOT gradient at week 28 versus placebo.

What safety requirements apply?

Camzyos keeps its boxed warning for heart-failure risk due to systolic dysfunction and is dispensed only through the CAMZYOS REMS program, which requires echocardiographic monitoring before and during treatment.