Bristol Myers Releases Five-Year Camzyos Data in Obstructive HCM

Bristol Myers Squibb released up-to-five-year Camzyos data on August 29 showing that patients with symptomatic obstructive hypertrophic cardiomyopathy continued to have lower left ventricular outflow tract gradients and improved symptom status during long-term treatment. The findings extend the follow-up for mavacamten well beyond the 30-week randomized EXPLORER-HCM trial that supported the drug’s clinical development.

The new results come from the EXPLORER-LTE cohort of MAVA-LTE, a long-term extension study that enrolled 231 patients who had completed EXPLORER-HCM. The extension is single-arm and open-label, with dose blinding, so the five-year results describe outcomes among patients continuing treatment rather than a new randomized comparison against placebo.

Five-year extension shows sustained reductions in obstruction

At 252 weeks, Bristol Myers reported a mean change from the extension-study baseline of minus 38.7 mm Hg in resting left ventricular outflow tract, or LVOT, gradient and minus 55.6 mm Hg in Valsalva LVOT gradient. The company said 97.4% of patients assessed at that time had a Valsalva gradient of 30 mm Hg or less, the threshold it cited for obstruction in obstructive HCM.

Symptoms also remained improved in the long-term cohort. Bristol Myers said 69.6% of patients improved by at least one New York Heart Association functional class at week 252, while 59.2% were asymptomatic. NYHA class is a clinical measure of how much heart-disease symptoms limit physical activity, so a shift to a lower class indicates less functional limitation.

The extension also tracked left ventricular ejection fraction, an important measure for a drug that reduces cardiac contractility. Mean LVEF was 10.2 percentage points lower than the extension baseline at 252 weeks but remained in the normal range on average, according to Bristol Myers. The company said no new safety signals were observed beyond those seen in the original EXPLORER-HCM study.

Camzyos is a cardiac myosin inhibitor designed to reduce the excessive interaction of actin and myosin that contributes to cardiac hypercontractility in hypertrophic cardiomyopathy. In the United States, the drug is approved for adults with symptomatic NYHA class II or III obstructive HCM to improve functional capacity and symptoms. By reducing contractility, treatment can lower the pressure gradient across the outflow tract, but that same mechanism makes ventricular-function monitoring central to its use.

Long follow-up does not remove Camzyos safety constraints

The five-year follow-up adds information about durability, but the study design limits what can be concluded from the later years. Everyone in EXPLORER-LTE had already completed the earlier EXPLORER-HCM trial and then entered an extension in which there was no concurrent placebo group. That makes the data useful for describing longer-term outcomes and safety exposure, but it does not provide a five-year randomized estimate of Camzyos’ effect compared with no Camzyos treatment.

Safety monitoring remains particularly important because Camzyos carries a U.S. boxed warning for heart failure due to systolic dysfunction. Bristol Myers’ prescribing information says echocardiographic assessments of LVEF are required before and during treatment. Starting Camzyos in a patient with LVEF below 55% is not recommended, and treatment should be interrupted if LVEF falls below 50% at any visit or if heart-failure symptoms or worsening clinical status occur.

The original EXPLORER-HCM safety results provide context for that warning. In the 30-week randomized study, dizziness occurred in 27% of Camzyos patients compared with 18% on placebo, and syncope occurred in 6% compared with 2%. Seven Camzyos patients, or 6%, experienced reversible reductions in LVEF below 50%, versus two placebo patients, or 2%; Bristol Myers said LVEF recovered in all seven Camzyos patients after treatment interruption.

Camzyos is also distributed in the United States through a restricted Risk Evaluation and Mitigation Strategy program. Prescribers, patients and pharmacies have enrollment or certification requirements, and patients must comply with ongoing monitoring. Certain CYP2C19 and CYP3A4 inhibitors or inducers are contraindicated because drug interactions can increase the risk of systolic dysfunction or reduce treatment effectiveness.

Those restrictions are important when interpreting Bristol Myers’ statement that no new safety signals emerged in the long-term extension. The result indicates that investigators did not identify a new category of risk compared with the earlier trial experience. It does not mean the existing heart-failure risk, monitoring requirements or drug-interaction constraints have disappeared.

Camzyos is becoming a larger part of Bristol Myers’ growth portfolio

The clinical update arrives as Camzyos contributes more revenue to Bristol Myers. In its second-quarter results, the company reported $416 million in worldwide Camzyos revenue for the three months ended June 30, up 60% from $260 million a year earlier. U.S. revenue was $310 million and international revenue was $105 million, with small differences in the worldwide total reflecting rounding.

For the first six months of 2026, Camzyos generated $729 million worldwide, up 74% from $419 million in the comparable 2025 period. Bristol Myers listed Camzyos among the products driving a 15% increase in second-quarter Growth Portfolio revenue to $7.6 billion. The latest five-year evidence therefore matters not only as a clinical follow-up but also as support for a medicine that is taking a larger place in the company’s newer-product mix.

Bristol Myers said on August 29 that more than 25,000 U.S. patients had been prescribed Camzyos by more than 5,000 healthcare providers. Those figures are company-reported adoption measures rather than independent estimates, but they show that the long-term evidence is being released after the product has moved well beyond its initial launch period.

The next U.S. regulatory milestone is already scheduled. The Food and Drug Administration has accepted a supplemental application seeking to extend Camzyos to adolescents ages 12 to under 18 with symptomatic obstructive HCM, and Bristol Myers’ latest quarterly filing lists a September 30, 2026 PDUFA date. The application is based on the Phase 3 SCOUT-HCM trial. FDA acceptance for review does not establish that the adolescent indication will be approved, making the September decision the next concrete event for the franchise after the five-year ESC update.