Aims To assess real-world characteristics, outcomes, and healthcare utilization associated with commercial mavacamten use in patients with oHCM.

Methods and Results We used the Symphony Dataverse to study patients receiving mavacamten between May 25, 2022 and June 30, 2024. Safety outcomes were prespecified and individual hospital-level claims manually reviewed to categorize cardiovascular hospitalizations. We included 2,440 patients and 18,494 mavacamten dispenses (63% females, median age 66 years [Interquartile range (IQR): 55, 73]). Patients were followed for a median of 3,037.0 days (IQR: 2,808, 3,221) prior to mavacamten initiation, and for 240 days (IQR: 117, 407) on mavacamten. Atrial fibrillation or flutter (AF/AFL) at baseline were present in 536 (22%) of patients, while new-onset AF/AFL requiring therapy occurred in 125 patients (5%) and new heart failure (HF) in 100 patients (4%). During follow-up, 154 patients (6%) received new dispenses of loop diuretics, 102 (4%) oral anticoagulants, 78 (3%) amiodarone, 17 (0.7%) sotalol, and 6 (0.2%) dofetilide. There was a total of 306 patients (13%) with 428 acute care episodes (most common claims were HF (n= 80, 26%), AF (n=74, 24%), and AFL (n= 16, 5%)). Predictors of safety outcomes (new HF, new AF/AFL, ventricular tachycardia, or transient ischemic attack [TIA]/stroke claim) were: age at mavacamten start, obesity, and TIA/stroke history.

Conclusion With 8 month median follow-up in this study, healthcare utilization for patients on mavacamten appeared substantial. New AF/AFL and HF occurred in 5% and 4%, respectively. Further work is needed to understand longer-term outcomes of mavacamten use in oHCM.

Ahmad Masri received research grants from Pfizer, Ionis, Attralus, Cytokinetics and Janssen and consulting fees from Cytokinetics, BMS, BridgeBio, Pfizer, Ionis, Lexicon, Attralus, Alnylam, Haya, Alexion, Akros, Edgewise, Rocket, Lexeo, Prothena, BioMarin, AstraZeneca, and Tenaya. Other coauthors have no disclosures.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Oregon Health & Science University IRB waived oversight for the insurance claims database research

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