Gradual Tapering or Discontinuation of Beta-Blockers After Stabilization With Mavacamten Therapy

Inclusion Criteria: 1. Age 18 to 75 years. 2. Diagnosis of obstructive hypertrophic cardiomyopathy (oHCM). 3. Receiving mavacamten for ≥12 weeks at screening, with the current maintenance dose stable for ≥8 weeks; after completion of the 4-week run-in period, the total duration of mavacamten treatment at randomization should generally be ≥16 weeks. 4. Receiving one and only one beta-blocker continuously for at least 4 weeks before randomization, with the beta-blocker type, dosing frequency, and daily dose remaining stable, and without concomitant use of a non-dihydropyridine calcium channel blocker. 5. The last qualified echocardiographic assessment before randomization shows a resting left ventricular outflow tract (LVOT) peak gradient \<30 mmHg and a Valsalva-provoked LVOT peak gradient \<50 mmHg. 6. Left ventricular ejection fraction (LVEF) ≥55% at randomization baseline. 7. Clinically stable and considered by the investigator to be suitable for sequential tapering and discontinuation of beta-blocker therapy. Exclusion Criteria: 1. Previous LVEF \<50% during mavacamten treatment, or previous interruption or discontinuation of mavacamten because of reduced left ventricular systolic function. 2. Heart failure decompensation requiring an emergency department visit, hospitalization, or intravenous treatment within 3 months before randomization; or, within 6 months before randomization, syncope not attributable to a clearly reversible cause, sustained ventricular tachycardia/ventricular fibrillation, or other clinically significant unstable arrhythmia. 3. Septal reduction therapy within 6 months before randomization, or anticipated need for surgical septal myectomy, alcohol septal ablation, or other septal reduction therapy during the 24-week study period. 4. A definite indication for beta-blocker therapy other than oHCM for which the investigator considers dose reduction or discontinuation unsafe. 5. An HCM phenocopy or another disease clearly responsible for left ventricular hypertrophy, including cardiac amyloidosis, Fabry disease, or other infiltrative, storage, or metabolic cardiomyopathies. 6. Moderate-to-severe valvular heart disease, fixed left ventricular outflow tract obstruction, or another structural heart disease that may substantially affect LVOT gradients or assessment of the primary outcome. 7. Severe renal impairment (estimated glomerular filtration rate \[eGFR\] \<30 mL/min/1.73 m²), end-stage renal disease, or ongoing dialysis. 8. Severe hepatic impairment (Child-Pugh class C), decompensated liver disease, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥3 times the upper limit of normal at screening, or other severe hepatic dysfunction considered by the investigator to potentially affect the safe use of mavacamten. 9. Active malignancy, ongoing systemic anticancer therapy that may substantially interfere with study assessments, or an anticipated life expectancy \<1 year because of a serious comorbid condition. 10. Pregnancy or breastfeeding, planned pregnancy during the study, or, for participants of childbearing potential, inability or unwillingness to use effective contraception. 11. A drug interaction that cannot be adequately modified or avoided and may substantially affect mavacamten exposure, or anticipated need for continued use of a protocol-prohibited medication during the study. 12. Other serious systemic disease, inability to complete the required follow-up or comply with the study protocol, or any other condition that, in the investigator's judgment, makes the participant unsuitable for the study.