Mavacamten Benefit Holds at 56 Weeks in Adolescents With oHCM

Adolescents with symptomatic obstructive hypertrophic cardiomyopathy (oHCM) who received mavacamten (Camzyos; Bristol Myers Squibb) maintained reductions in left ventricular outflow tract (LVOT) obstruction through 56 weeks, according to new data from the phase 3 SCOUT-HCM trial (NCT06253221). No patient had a left ventricular ejection fraction (LVEF) below 50% over the 56-week period, a finding relevant to pharmacists dispensing the cardiac myosin inhibitor under its Risk Evaluation and Mitigation Strategy (REMS) program.¹

The data were presented as a late-breaker at the Hypertrophic Cardiomyopathy Medical Society (HCMS) Scientific Sessions on November 6, 2026, in Chicago, Illinois. They build on 28-week results that supported the FDA's September 2026 approval of mavacamten for pediatric patients weighing 30 kg (66 lbs) or more with symptomatic oHCM.^1,2

"We were really happy with the 56-week results," Joseph Rossano, MD, MS, FAAP, FACC, chief of cardiology at Children's Hospital of Philadelphia and principal investigator of SCOUT-HCM, told Pharmacy Times. "Basically, we saw that the effects at 28 weeks for mavacamten were sustained at 56 weeks."

Durable Gradient Reductions Through Week 56

SCOUT-HCM randomly assigned 44 patients aged 12 to younger than 18 years to once-daily mavacamten or placebo for 28 weeks. Starting doses were 2.5 mg for patients weighing 35 to less than 45 kg and 5 mg for those weighing 45 kg or more, adjusted based on echocardiogram parameters. At baseline, approximately 83% and 86% of patients in the mavacamten and placebo groups, respectively, were receiving β-blockers.^1,3

Of the 44 randomized participants, 43 (23 mavacamten, 20 placebo) completed the placebo-controlled period, and all 43 received mavacamten from week 28 through week 56. Patients who received mavacamten throughout the trial had a mean change from baseline in Valsalva LVOT gradient of −48.1 mmHg at week 56, and a similar degree of gradient reduction was observed among patients who switched from placebo.¹

"Fundamentally, I think that just provides nice, reassuring information that what we saw in the first 28 weeks wasn't a fluke—that this was replicated in an additional cohort," Rossano said of the crossover results.

Safety Findings and REMS Monitoring

Treatment-related treatment-emergent adverse events (TEAEs) and serious TEAEs numbered 5 and 2, respectively, in the mavacamten-mavacamten arm over 56 weeks, and 1 and 0, respectively, in the placebo-mavacamten arm over 28 weeks of active treatment. No new safety signals were reported.¹

Mavacamten carries a boxed warning for heart failure due to systolic dysfunction and is available only through the Camzyos REMS Program, which requires pharmacies to be certified and to dispense only to authorized patients. Labeling calls for echocardiographic LVEF assessment before and during treatment and for interrupting therapy if LVEF falls below 50% at any visit.¹

"Part of the REMS program is to make sure that ventricular function continues to be preserved, which it was in the SCOUT-HCM study," Rossano said. "But doses may need to be adjusted over time, and the medication can interact with other medications, so I think those are areas where pharmacists play a very important role."

Drug Interactions Pharmacists Should Watch

Mavacamten is primarily metabolized by CYP2C19 and, to a lesser extent, CYP3A4. It is contraindicated with strong CYP2C19 inhibitors and with moderate to strong CYP2C19 or CYP3A4 inducers. Labeling advises to reduce the dose by 1 level down to 1 mg in pediatric dosing when patients taking it start certain CYP2C19 or CYP3A4 inhibitors, and counseling patients about over-the-counter products such as omeprazole, esomeprazole, and cimetidine. Additionally, because mavacamten may reduce exposure to certain progestins, females of reproductive potential using combined hormonal contraceptives other than ethinyl estradiol/norethindrone should add nonhormonal contraception during treatment and for 4 months after the last dose.¹

Long-Term Questions Remain

Rossano pointed to encouraging signs, including improvements in diastolic function, reductions in troponin and natriuretic peptides, and reduced heart wall thickness. "Well, we don't know how the medication will behave in the very long term," he said. "I think we've seen some exciting signals that the heart may be favorably remodeling."

SCOUT-HCM continues with an open-label long-term extension period of up to 144 weeks.¹

"This is great for patients who have oHCM, and I think it's great for the field of pediatric cardiology," Rossano said.

REFERENCES

1. Bristol Myers Squibb presents 56-week phase 3 data in pediatric patients with symptomatic obstructive hypertrophic cardiomyopathy (oHCM) for Camzyos (mavacamten) at the Hypertrophic Cardiomyopathy Medical Society (HCMS) Scientific Sessions. News release. Bristol Myers Squibb. November 6, 2026. Accessed November 10, 2026. https://news.bms.com/news/details/2026/Bristol-Myers-Squibb-Presents-56-Week-Phase-3-Data-in-Pediatric-Patients-with-Symptomatic-Obstructive-Hypertrophic-Cardiomyopathy-oHCM-for-Camzyos-mavacamten-at-the-Hypertrophic-Cardiomyopathy-Medical-Society-HCMS-Scientific-Sessions/default.aspx

2. Rossano JW, Canter C, Wolf CM, et al; SCOUT-HCM investigators. Mavacamten in adolescents with obstructive hypertrophic cardiomyopathy. N Engl J Med. 2026;395(4):362-373. doi:10.1056/NEJMoa2601103

3. Rossano J, Canter C, Wolf C, et al. Mavacamten in symptomatic adolescent patients with obstructive hypertrophic cardiomyopathy: design of the phase 3 SCOUT-HCM trial. Am Heart J. 2026;292:107283. doi:10.1016/j.ahj.2025.107283