Mavacamten sNDA Gets FDA Priority Review for Adolescent Obstructive HCM

The US Food and Drug Administration (FDA) has accepted a supplemental new drug application (sNDA) for mavacamten (Camzyos) for adolescents with symptomatic obstructive hypertrophic cardiomyopathy (oHCM).1

Announced by parent company Bristol Myers Squibb on June 1, 2026, the FDA has granted the sNDA Priority Review for patients aged 12 to <18. The FDA has also assigned a Prescription Drug User Fee Act (PDUFA) target action date of September 30, 2026. If approved, the application would expand the currently approved US indication for mavacamten beyond adults with symptomatic New York Heart Association class II-III oHCM.1,2

“The acceptance of this NDA allows us the potential to extend our leadership in oHCM to a younger patient population with a high unmet medical need,” Cristian Massacesi, MD, executive vice president, chief medical officer, and head of development at Bristol Myers Squibb, said in a statement. “We are encouraged by the possibility of bringing this potentially paradigm-shifting treatment to adolescents at a time when a condition like oHCM can significantly impact both physical and emotional aspects of their lives.”1

About Mavacamten

Mavacamten is a selective, reversible, allosteric inhibitor of cardiac myosin. In oHCM, the agent is intended to reduce excessive actin-myosin cross-bridge formation and myocardial contractility, with downstream effects on left ventricular outflow tract (LVOT) obstruction. The drug carries a boxed warning for risk of heart failure due to systolic dysfunction and is available in the United States only through the Camzyos Risk Evaluation and Mitigation Strategy program.2

The current US label is limited to adults with symptomatic NYHA class II-III oHCM to improve functional capacity and symptoms. In the announcement, Bristol Myers Squibb reported that mavacamten has been prescribed by >4500 clinicians to nearly 25,000 patients in the United States.1.2

The Phase 3 SCOUT-HCM Trial

The sNDA is supported by SCOUT-HCM, a phase 3, randomized, double-blind, placebo-controlled, international trial enrolling 44 adolescents aged 12 to >18 years with symptomatic oHCM. The trial included 3 treatment periods totaling up to 200 weeks: a 28-week placebo-controlled period, a 28-week active-treatment period in which participants initially assigned to placebo cross over to mavacamten, and an open-label long-term extension for ≤144 weeks.1,3

The primary endpoint was change from baseline to week 28 in Valsalva LVOT gradient. Secondary endpoints included resting and postexercise LVOT gradients, peak oxygen consumption, symptom and health status measures, and safety. SCOUT-HCM met its primary endpoint, with a clinically meaningful and statistically significant reduction from baseline in Valsalva LVOT gradient at week 28 for mavacamten compared with placebo.1,3

Bristol Myers Squibb stated that the safety profile in adolescents was similar to that in adults and that no participant had a left ventricular ejection fraction below 50% over the 28-week period. In adult labeling, reductions in LVEF below 50% occurred in 6% of patients receiving mavacamten and 2% receiving placebo in EXPLORER-HCM; dizziness and syncope were adverse reactions reported more often with mavacamten than placebo.1,2

Safety Considerations and Regulatory Next Steps

The proposed adolescent indication would enter a therapeutic area with limited pediatric-specific pharmacologic evidence. Hypertrophic cardiomyopathy (HCM) can be associated with pathogenic or suspected pathogenic sarcomeric variants, and obstructive physiology may contribute to exertional symptoms. Contemporary guidelines emphasize individualized evaluation of symptoms, obstruction, arrhythmia risk, family history, and treatment goals in patients with HCM, including referral to centers with disease-specific expertise when appropriate.4

For mavacamten, the key safety issue remains systolic dysfunction. The US prescribing information requires echocardiographic assessment of LVEF before and during treatment; initiation is not recommended in patients with LVEF <55%, and interruption is required if LVEF falls below 50% or if heart failure symptoms or worsening clinical status occur. The label also lists contraindications with strong CYP2C19 inhibitors and with moderate to strong CYP2C19 or moderate to strong CYP3A4 inducers because of potential effects on exposure and heart failure risk or reduced efficacy.2

References

1. Bristol Myers Squibb. U.S. Food and Drug Administration accepts for Priority Review Bristol Myers Squibb’s supplemental New Drug Application for Camzyos (mavacamten) to treat adolescents with symptomatic obstructive hypertrophic cardiomyopathy (oHCM). BusinessWire. Published June 1, 2026. Accessed June 1, 2026. https://www.businesswire.com/news/home/20260529154810/en/U.S.-Food-and-Drug-Administration-Accepts-for-Priority-Review-Bristol-Myers-Squibbs-Supplemental-New-Drug-Application-for-Camzyos-mavacamten-to-Treat-Adolescents-with-Symptomatic-Obstructive-Hypertrophic-Cardiomyopathy-oHCM

2. Bristol Myers Squibb. Camzyos (mavacamten) prescribing information. April 2025. Accessed June 1, 2026. https://packageinserts.bms.com/pi/pi_camzyos.pdf

3. Bristol-Myers Squibb. A study to evaluate mavacamten in adolescents with symptomatic obstructive hypertrophic cardiomyopathy. ClinicalTrials.gov Identifier: NCT06253221. Updated December 19, 2025. Accessed June 1, 2026. https://clinicaltrials.gov/study/NCT06253221

4. Ommen SR, Mital S, Burke MA, et al. 2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. J Am Coll Cardiol. 2020;76(25):3022-3055. doi:10.1016/j.jacc.2020.08.044