Bristol Myers Squibb (NYSE: BMY), headquartered in Princeton, New Jersey, announced receipt of US FDA Priority Review for a supplemental New Drug Application (sNDA) covering Camzyos (mavacamten) in adolescents aged 12 to under 18 with symptomatic obstructive hypertrophic cardiomyopathy (oHCM). The FDA assigned a Prescription Drug User Fee Act (PDUFA) date of September 30, 2026. Mavacamten is a selective, reversible, allosteric inhibitor of cardiac myosin — a small molecule that targets the sarcomeric protein driving hypercontractility in oHCM.
Priority Review compresses the FDA’s standard ten-month review window to six months and is reserved for therapies that, if approved, would offer a material improvement over available options for serious conditions. No pharmacological therapy is currently approved for adolescents with oHCM, making this sNDA the first attempt to establish a drug-based standard of care in this age group.
The sNDA rests on data from the Phase III SCOUT-HCM trial (NCT06253221), a randomized, double-blind, placebo-controlled international study enrolling 44 adolescent patients with symptomatic oHCM. The primary endpoint — change from baseline to Week 28 in Valsalva left ventricular outflow tract (LVOT) gradient — was met with a least-squares mean reduction of 48.5 mmHg in the mavacamten arm versus 0.5 mmHg with placebo, a between-group difference of −48.0 mmHg (95% CI: −67.7 to −28.3; p < 0.001). These figures were published simultaneously in the New England Journal of Medicine and presented at the American College of Cardiology Annual Scientific Session in March 2026; the BMS announcement of Priority Review acceptance in June 2026 cited the same dataset without reproducing the full numeric detail.
On safety, no patient in either arm experienced a left ventricular ejection fraction (LVEF) below 50% during the 28-week placebo-controlled period. Overall adverse event rates were comparable across arms — 78% with mavacamten versus 81% with placebo — and serious adverse events occurred in two patients per arm. One mavacamten patient experienced two episodes of syncope considered drug-related. The enrolled population had high baseline disease severity, with mean maximal left ventricular wall thickness of 28.3 mm in the mavacamten arm and 24.7 mm in the placebo arm.
The clean LVEF signal carries particular weight given that the existing adult label for Camzyos carries a Boxed Warning for heart failure risk and operates under a Risk Evaluation and Mitigation Strategy (REMS) program requiring certified prescribers, enrolled patients, and certified pharmacies. Demonstrating that the same safety thresholds hold in adolescents — a population with potentially different pharmacokinetics, as weight-based dosing of 2 or 5 mg per day was used in SCOUT-HCM — was central to the regulatory case.
Mavacamten received its original FDA approval in April 2022 for adults with symptomatic New York Heart Association (NYHA) class II–III oHCM. It is now approved in more than 60 countries and has been prescribed by over 4,500 healthcare providers to approximately 25,000 patients in the US. The current sNDA represents a label extension rather than a de novo approval, but the adolescent population presents distinct clinical and regulatory considerations: no prior controlled trial in this age group had generated the LVOT gradient data required for a pharmacological approval.
Research context
Hypertrophic cardiomyopathy (HCM) arises from genetic defects in sarcomeric proteins or from idiopathic causes and produces a spectrum of obstructive and non-obstructive phenotypes. In adolescents, the obstructive form generates substantial morbidity through reduced exertional tolerance at a stage of life when physical activity and emotional development are closely linked. Current management relies on beta-blockers, which carry tolerability limitations in younger patients, or invasive septal reduction procedures — surgical myectomy or alcohol septal ablation — that carry procedural risk profiles poorly suited to first-line use in this age group.
Mavacamten’s mechanism — direct allosteric inhibition of cardiac myosin to reduce hypercontractility and LVOT obstruction — differentiates it from the rate-control and symptom-management approach of beta-blockers, and from the structural intervention of septal reduction. Its only approved competitor in the cardiac myosin inhibitor class is aficamten, developed by Cytokinetics, which completed the Phase III SEQUOIA-HCM trial in adults with non-obstructive HCM and is under FDA review for that indication; aficamten has not yet generated adolescent-specific controlled data. If the mavacamten sNDA clears the September 30 PDUFA date, Bristol Myers Squibb would hold the only approved pharmacological option for oHCM across both adult and adolescent populations.