Early Insights on Mavacamten Usage in Canada: A Retrospective Cohort Study of the Mavacamten Patient Support Program.

Background: Only a limited amount of real-world data are available on the demographic and clinical characteristics of adult patients with obstructive hypertrophic cardiomyopathy (oHCM) treated with mavacamten in Canada. Methods: This observational retrospective cohort study included adult patients with symptomatic oHCM enrolled in the mavacamten patient support program in Canada between January 4, 2023 and April 12, 2024. Baseline demographic information, clinical characteristics, medical history, and mavacamten treatment information were collected from the program database. Results: A total of 683 patients met the eligibility criteria for the study. The median age was 65.0 years (interquartile range: 57.0-73.0); 52.1% of the patients were male; and 67.1% were classified as being in New York Heart Association class II at baseline. Most patients were on beta-blocker monotherapy at baseline (63.7%) and the data cutoff point (76.3%). Almost all patients (99.4%) were initiated with 5 mg of mavacamten. The median follow-up time was 27.4 weeks (range: 1.6-70.1), and the median treatment duration was 24.6 weeks (range: 0.4-64.4). At the data cutoff point, 17.1% of patients were on 2.5 mg of mavacamten, 52.6% were on 5 mg, 20.2% were on 10 mg, and 2.2% were on 15 mg. Mavacamten was discontinued by 7.9% of patients, the main reasons being a side effect or adverse event (2.5%; 17 of 683), an undisclosed physician decision (1.8%; 12 of 683), or lack of efficacy (0.9%; 6 of 683). Conclusions: These early results provide the largest dataset on mavacamten utilization in the Canadian oHCM population. Baseline demographic and clinical characteristics and mavacamten dose distributions are comparable to those found in clinical trials and real-world studies. Clinical Trial Registration: NCT06549608.