Real-world experience with mavacamten in obstructive hypertrophic cardiomyopathy: observations from a tertiary care center

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Abstract Background In symptomatic obstructive hypertrophic cardiomyopathy (oHCM) patients, mavacamten is commercially approved to help improve left ventricular (LV) outflow tract (LVOT) gradients, symptoms, and reduce eligibility for septal reduction therapy (SRT) under the risk evaluation and mitigation strategy (REMS) program. We sought to prospectively report the initial real-world clinical experience with the use of commercially available mavacamten in a multi-hospital tertiary healthcare system. Methods We studied the first 150 consecutive oHCM patients (mean age 65 years, 53% women, 83% on betablockers and 61% in New York Heart Association [NYHA] class III) who were initiated on 5 mg of mavacamten with dose titrations using symptom assessment and echocardiographic measurements of LVOT gradient and LV ejection fraction (LVEF) measurements. We measured changes in NYHA class, LVEF, LVOT gradients (resting and Valsalva) at baseline, 4, 8 and 12 weeks. Results At 261±143 days (range of 31-571 days), 69 (46%) patients had ≥1 NYHA class, 27 (18%) additional patients had ≥2 NYHA class improvement and 40 (27%) reported a no change in symptoms. The mean LVOT gradient at rest decreased from 41±33 mmHg at baseline to 16±17 mmHg at 4 weeks, 16±16 mmHg at 8 weeks and 15±16 mmHg at 12 weeks. The mean drop in resting LVOT gradient from baseline to last follow-up was 26±3 mmHg (p<0.0001). The mean Valsalva LVOT gradient decreased from 72±43 mmHg at baseline to 29±31 mmHg at 4 weeks, 29±28 mmHg at 8 weeks and 30±29 mmHg at 12 weeks (p<0.001). The mean reduction in post Valsalva LVOT gradient from baseline to last follow-up was 43±4 mmHg (p<0.0001). At baseline, 100% patients had Valsalva LVOT gradients ≥ 30 mm Hg and 142 (95%) had ≥ 50 mm Hg. After initiation of mavacamten therapy, Valsalva LVOT gradient ≥ 30 mm Hg was observed in 44/150 (29%) at 4 weeks, 40/141 (28%) at 8 weeks and 41/136 (30%) at 12 weeks. In 40 patients who reported no symptomatic improvement, the mean Valsalva LVOT gradient decreased from 73±39 mmHg at baseline to 34± 27 mmHg at 4 weeks, 35±28 mmHg at 8 weeks and 30±24 mmHg at 12 weeks (P<0.001). The mean LVEF at baseline was 66±6% and changed to 64±5% at 4 weeks, 63±5% at 8 weeks and 62±7% at 12 weeks (p<0.0001). No patient underwent SRT, developed LVEF ≤30% or developed heart failure requiring admission. Three (2%) patients needed temporary interruption of mavacamten due to LVEF<50. During follow up, dose reduction or discontinuation of background HCM therapy (betablockers, calcium channel blockers and disopyramide) occurred in 33 (22%) patients. The breakdown of various drug doses of mavacamten, at last follow-up, is as follows: 2.5 mg (n=29, 19%), 5 mg (n=80, 53%), 10 mg (n=37, 25%) and 15 mg (n=3, 2%). Conclusions In a real-world study in symptomatic oHCM patients at a multi-hospital tertiary care referral center, we demonstrate the efficacy and safety of prescribing mavacamten under the REMS program.