Effect of Mavacamten on Echocardiographic Features in Symptomatic Patients With Obstructive Hypertrophic Cardiomyopathy

J Am Coll Cardiol. 2021 Dec 21;78(25):2518-2532. doi: 10.1016/j.jacc.2021.09.1381.

Abstract

Background: EXPLORER-HCM (Clinical Study to Evaluate Mavacamten [MYK-461] in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy) demonstrated that mavacamten, a cardiac myosin inhibitor, improves symptoms, exercise capacity, and left ventricular outflow tract (LVOT) obstruction in patients with obstructive hypertrophic cardiomyopathy (oHCM).

Objectives: The purpose of this study was to evaluate mavacamten's effect on measures of cardiac structure and function and its association with changes in other clinical measures.

Methods: Key echocardiographic parameters from serial echocardiograms over 30 weeks from 251 symptomatic oHCM patients (mavacamten [n = 123], placebo [n = 128]) were assessed in a core laboratory.

Results: More patients on mavacamten (80.9%; n = 76 of 94) vs placebo (34.0%; n = 33 of 97) showed complete resolution of mitral valve systolic anterior motion after 30 weeks (difference, 46.8%; P < 0.0001). Mavacamten also improved measures of diastolic function vs placebo, including left atrial volume index (LAVI) (mean ± SD baseline: 40 ± 12 mL/m2 vs 41 ± 14 mL/m2; mean change from baseline of -7.5 mL/m2 [95% CI: -9.0 to -6.1 mL/m2] vs -0.09 mL/m2 [95% CI: -1.6 to 1.5 mL/m2]; P < 0.0001) and lateral E/e' (baseline, 15 ± 6 vs 15 ± 8; change of -3.8 [95% CI: -4.7 to -2.8] vs 0.04 [95% CI: -0.9 to 1.0]; P < 0.0001). Among mavacamten-treated patients, improvement in resting, Valsalva, and post-exercise LVOT gradients, LAVI, and lateral E/e' was associated with reduction in N-terminal pro-B-type natriuretic peptide (P ≤ 0.03 for all). Reduction in LAVI was associated with improved peak exercise oxygen consumption (P = 0.04).

Conclusions: Mavacamten significantly improved measures of left ventricular diastolic function and systolic anterior motion. Improvement in LVOT obstruction, LAVI, and E/e' was associated with reduction in a biomarker of myocardial wall stress (N-terminal pro-B-type natriuretic peptide). These findings demonstrate improvement in important markers of the pathophysiology of oHCM with mavacamten. (Clinical Study to Evaluate Mavacamten [MYK-461] in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy; NCT03470545).

Keywords: N-terminal pro–B-type natriuretic peptide; diastolic function; hypertrophic cardiomyopathy; mavacamten.

Publication types

  • Clinical Trial, Phase III
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Benzylamines / pharmacology
  • Benzylamines / therapeutic use*
  • Biomarkers / blood
  • Cardiac Myosins / antagonists & inhibitors
  • Cardiomyopathy, Hypertrophic / blood
  • Cardiomyopathy, Hypertrophic / diagnostic imaging
  • Cardiomyopathy, Hypertrophic / drug therapy*
  • Double-Blind Method
  • Echocardiography
  • Exercise Tolerance / drug effects
  • Female
  • Heart / drug effects*
  • Humans
  • Male
  • Middle Aged
  • Uracil / analogs & derivatives*
  • Uracil / pharmacology
  • Uracil / therapeutic use

Substances

  • Benzylamines
  • Biomarkers
  • MYK-461
  • Uracil
  • Cardiac Myosins

Associated data

  • ClinicalTrials.gov/NCT03470545