FDA records a Camzyos efficacy approval for obstructive hypertrophic cardiomyopathy

The Food and Drug Administration has logged a new efficacy approval for Camzyos, Bristol Myers Squibb's heart drug mavacamten. The action was recorded in the agency's Drugs@FDA database on 30 September 2026 under new drug application 214998 as an efficacy supplement; the product is a 2.5 mg oral capsule, one of several strengths [s2]. Camzyos is labelled for adults with symptomatic New York Heart Association (NYHA) class II-III obstructive hypertrophic cardiomyopathy (HCM), to improve functional capacity and symptoms [s3]. The specific labelling change tied to the 30 September supplement had not yet posted to the agency's public label file at the time of writing, so the account below rests on the drug's trial record.

Mavacamten is a first-in-class cardiac myosin inhibitor [s1]. Hypertrophic cardiomyopathy involves excessive contraction of the heart muscle, and in the obstructive form that hypercontractility narrows the outflow of the left ventricle. Rather than borrowing drugs developed for other conditions, mavacamten targets that mechanism directly, dialling down the overactive contraction.

What the pivotal trial tested

The drug's registrational evidence is EXPLORER-HCM, a phase 3, randomised, double-blind, placebo-controlled trial at 68 cardiovascular centres in 13 countries [s1]. It enrolled patients with a left ventricular outflow tract (LVOT) gradient of 50 mm Hg or greater and NYHA class II-III symptoms, assigning them 1:1 to mavacamten, started at 5 mg, or placebo for 30 weeks [s1]. In all, 251 patients were randomised — 123 to mavacamten and 128 to placebo [s1].

The primary endpoint was a composite that required either a meaningful gain in exercise capacity, measured as peak oxygen uptake, together with no worsening of symptom class, or a larger gain in oxygen uptake with an improvement in class [s1].

What it found

The endpoint was met by 45 of 123 patients (37%) on mavacamten versus 22 of 128 (17%) on placebo — a difference of 19.4 percentage points (95% confidence interval 8.7 to 30.1; P=0.0005) [s1]. The mechanistic measures moved further: post-exercise LVOT gradient fell by 36 mm Hg more on the drug than on placebo (95% CI −43.2 to −28.1; P<0.0001), and peak oxygen uptake rose by 1.4 mL/kg/min more (0.6 to 2.1; P=0.0006) [s1]. Thirty-four percent more patients on mavacamten improved by at least one NYHA class — 80 of 123 versus 40 of 128 on placebo [s1]. Safety and tolerability were similar to placebo, and treatment-emergent adverse events were generally mild [s1].

A more recent integrated analysis of four phase 3 studies examined mavacamten used without background beta-blockers or calcium-channel blockers; it reported that monotherapy was associated with improvements in LVOT gradient and symptoms broadly similar to combination use, with reductions in left ventricular ejection fraction from baseline to week 128 of 8.8% or less across groups [s4].

How to read it

The endpoint is a composite, and the symptom portion is subjective, so the firmer evidence is in the objective measures — the fall in outflow gradient and the rise in oxygen uptake, both of which separated clearly from placebo [s1]. The known cost is on the other side of the same mechanism: a drug that reduces contraction can lower the ejection fraction, which is why ejection-fraction monitoring defines how the drug is used [s4].

EXPLORER-HCM was also a 30-week trial, so it speaks to a few months of treatment rather than to the years over which obstructive HCM is actually managed [s1]. That is part of why the longer follow-up matters. The integrated monotherapy analysis extended observation to week 128 and reported ejection-fraction reductions of 8.8% or less across the treatment groups — a figure that frames the magnitude of the trade-off clinicians are monitoring for, rather than resolving it [s4]. Most patients in the original phase 3 studies took mavacamten alongside a beta-blocker or calcium-channel blocker, so evidence on the drug used by itself is a more recent and still-maturing part of the picture [s4].

What to watch

The near-term question is exactly how the new supplement refines the label — for instance around dosing or monitoring — once the updated text posts [s2][s3]. The broader one is whether the monotherapy evidence changes who starts the drug and with what background therapy [s4].

Red flags: a person on mavacamten with new or worsening breathlessness, swelling, fainting or palpitations should seek medical review, as these can signal a fall in heart function [s1][s4]. This article describes research and regulatory news and is not medical advice. HCM treatment is a decision for patients and their treating cardiologists.

Sources

• Mavacamten for treatment of symptomatic obstructive hypertrophic cardiomyopathy (EXPLORER-HCM) — The Lancet, 29 August 2020
• Drugs@FDA: Camzyos (mavacamten), NDA 214998 — efficacy supplement approval record — U.S. Food and Drug Administration, approved 30 September 2026
• Label: Camzyos (mavacamten) — indications and usage — U.S. Food and Drug Administration, effective 17 April 2025
• Mavacamten monotherapy in obstructive hypertrophic cardiomyopathy: an integrated analysis of four phase 3 studies — American Heart Journal, 24 August 2026