Abstract Body (Do not enter title and authors here): Introduction: The mavaCamten ObservationaL evIdence Global cOnsortium in hypertrophic cardiomyopathy (COLLIGO-HCM; ClinicalTrials.gov ID NCT06372457) is a multinational, multicenter observational research initiative aiming to describe the real-world outcomes of mavacamten for the treatment of obstructive HCM.

Aims: Describe the real-world effectiveness and safety of mavacamten, measured by echo measurements and NYHA class.

Methods: This retrospective study used data from medical records from two participating HCM centers in the US. Patient-level data was extracted to assess the effectiveness and safety of mavacamten post-treatment initiation through 60 weeks. Patient characteristics and outcomes were described, including echocardiogram measurements, New York Heart Association (NYHA) functional class, and safety.

Results: A total of 93 patients were treated with mavacamten (mean age 60.6 ± 13.9 years, 23.7% black, 57.0% female, and 77.4% NYHA class III at baseline) with a mean follow-up of 37.0 ± 28.1 weeks (Table). From baseline to week 60, 3 (3.2%) patients experienced temporary treatment discontinuation, and 3 (3.2%) discontinued mavacamten due to left ventricular ejection fraction (LVEF) <50%. By week 12, 77.1% of patients had improved by ≥1 NYHA class. The percentage increased to 89.5% by week 24 and remained stable through week 60. Mean changes from baseline in resting and Valsalva left ventricular outflow tract gradients were 31.8 ± 32.8 and 57.3 ± 47.3 mmHg, respectively, at week 24, and remained similar through week 60. Mean change in LVEF from baseline was 4.1 ± 7.1% at week 12 and remained largely unchanged through week 60 (Figure).

Conclusions: This study demonstrated the early and sustained effectiveness of mavacamten with one of the longest follow-ups to date, in a real-world population with a higher racial diversity and disease burden than those in the clinical trials. This data further substantiates the effectiveness and safety profile of mavacamten.