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The FDA approved mavacamten (Camzyos) for the treatment of obstructive hypertrophic cardiomyopathy (HCM) in people with New York Heart Association class II-III symptoms -- but on the condition it would only be available through a restricted program.

The cardiac myosin inhibitor's label includes a boxed warning that the drug reduces left ventricular ejection fraction (LVEF) and can cause heart failure due to systolic dysfunction.

Because of this risk, patients can only get mavacamten through a restricted program under a risk evaluation and mitigation strategy (REMS). Among other requirements, the REMS program requires prescribers to be certified and patients to comply with ongoing monitoring of LVEF and other clinical status before and during mavacamten treatment, .

Mavacamten is not recommended as a new therapy for people with LVEF below 55%, nor as a continued therapy for users who experience LVEF dipping below 50% or heart failure symptoms while taking the medication.

In EXPLORER-HCM, the double-blind randomized trial from 2020 that was the basis of mavacamten's FDA approval, a 4% absolute drop in LVEF from baseline to week 30 was observed with the therapy. LVEF recovered after withdrawal of mavacamten.

The main finding of the 251-person study was that mavacamten conferred better functional capacity and had left ventricular outflow tract gradients reduced for people with symptomatic obstructive HCM and LVEFs of at least 55% at baseline.

A secondary analysis of the trial showed that the drug also improved quality of life, according to Kansas City Cardiomyopathy Questionnaire scores.

"This is a first-in-class medicine specifically for patients living with symptomatic obstructive HCM," said HCM specialist and cardiac imager Milind Desai, MD, MBA, of the Cleveland Clinic in Ohio, in a statement included in the drugmaker's announcement. "With this FDA approval, U.S. cardiologists now have a new pharmacological option for eligible patients that targets the underlying pathophysiology of the disease."

Mavacamten works as an allosteric and reversible inhibitor selective for cardiac myosin. The product will be available in capsules ranging from 2.5- to 15-mg doses.

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