Gauging Outcomes of Obstructive HCM Treated with Mavacamten

By James P. MacNamara, M.D., M.S.C.S.

Assistant Professor of Internal Medicine

Mavacamten is the first cardiac myosin inhibitor approved to reduce left ventricular outflow tract (LVOT) obstruction, improve quality of life, and increase fitness in patients with obstructive hypertrophic cardiomyopathy (oHCM). The COLLIGO-HCM study, sponsored by Bristol Myers Squibb, is a multinational, multicenter observational study of real-world outcomes for patients with oHCM treated with mavacamten. UT Southwestern was an original member of the study, and at the #AHA24, we presented the preliminary findings of the American cohort.

We manually extracted patient-level data from the medical record for all patients (n = 93) with oHCM who were prescribed mavacamten at the cohort’s two centers from 2022 to 2024. The cohort was diverse, with 57% women and 24% Black patients, much higher than the Phase III clinical trials. At baseline, the patients had a significant symptom burden (77% with NYHA III symptoms) and significant LVOT obstruction (mean LVOT gradient with Valsalva was 84 mm Hg).

Treatment with mavacamten was associated with a significant improvement in NYHA class and LVOT obstruction. By week 12, 77% of patients had improved by ≥ 1 NYHA class. The percentage increased to 88% by week 24 and remained stable through week 60. By week 24, 87% of patients had achieved a resting LVOT gradient < 30 mm Hg, and 72% had achieved a Valsalva LVOT gradient < 30 mm Hg. Mavacamten carries a risk of decreasing the LV ejection fraction (LVEF). In our study, 3% of patients temporarily discontinued mavacamten and an additional 3% permanently discontinued mavacamten due to LVEF < 50%, rates similar to prior studies.

These data further confirm the early and sustained effectiveness of mavacamten in improving symptoms and obstruction in a real-world population with higher racial diversity and disease burden than those previously reported in the clinical trials.