FOREST-HCM enrolled 213 patients with obstructive HCM from May 28, 2021 through October 31, 2023. Previously presented data from 17 patients who had been enrolled through 48 weeks in FOREST-HCM showed that prolonged treatment with aficamten was associated with significant and sustained reductions in left ventricle outflow tract gradient (LVOT-G), and improvements in symptoms and cardiac biomarkers. The updated data set presented at ACC in Atlanta focuses on 46 patients from FOREST-HCM that had completed 48 weeks of follow-up at the time of the current interim analysis.
At Week 48, 75% of these patients were receiving the 15 mg or 20 mg dose of aficamten. Treatment with aficamten for 48 weeks resulted in substantial and sustained reductions in average resting LVOT-G (mean change from baseline (SD) = -39.6 mmHg (34), p<0.0001) and Valsalva LVOT-G (mean change from baseline (SD) = -53.2 mmHg (38.6), p<0.0001). Statistically significant improvements in New York Heart Association (NYHA) Functional Class from baseline were observed, with 82.2% of patients improving by ≥1 NYHA class with no instances of worsening NYHA class. Additionally, there were significant improvements in NT-proBNP, a biomarker of cardiac wall stress, with an average decrease of 63% from baseline to week 48 (p<0.001). Treatment with aficamten also resulted in statistically significant improvements in measures of cardiac structure and function including decreases in maximum wall thickness (mean change from baseline (SE) = -0.12 cm (0.02), p<0.0001), left atrial volume index (mean changes from baseline (SE) = -3.5 mL/m2 (0.98), p=0.0008) and lateral E/e' (mean change from baseline (SE) = -2.2 (0.92), p=0.02). While 19 of these 46 patients in FOREST-HCM met guideline eligibility criteria for septal reduction therapy (SRT) at baseline, only one patient remained eligible for SRT after six months of treatment with aficamten, representing a 94% reduction in SRT-eligibility.