Aficamten in patients with obstructive hypertrophic cardiomyopathy: an integrated safety analysis
Authors: Masri A , Barriales-Villa R , Elliott P , Nassif M E , Owens A T , Oreziak A , Tower-Rader A , Chiu M , Heitner S B , Kupfer S , Malik F I , Melloni C , Meng L , Wohltman A , Saberi S 
Published: October 2024

Abstract

Background
Aficamten is a next-in-class, oral, selective cardiac myosin inhibitor targeting the hypercontractility underlying hypertrophic cardiomyopathy (HCM). It relieves left ventricular outflow tract obstruction, improves exercise capacity, symptoms, quality of life, and cardiac biomarkers with a modest effect on left ventricular ejection fraction (LVEF).

Purpose
To present an integrated safety analysis from all aficamten trials to date.

Methods
Patients with obstructive HCM (oHCM) who received ≥1 dose of aficamten or placebo [PBO] in the phase 2 REDWOOD-HCM trial, phase 3 SEQUOIA-HCM trial, or the open-label extension FOREST-HCM were included.

Results
In the PBO-controlled pool of REDWOOD-HCM and SEQUOIA-HCM, 170 patients received aficamten and 153 PBO. In the cumulative (parent+extension) aficamten treated pool, 283 patients were analyzed from initial dose of aficamten or after enrollment in FOREST-HCM (100 PBO-to-aficamten). Overall, mean age was 59 years, 42% were female. In the PBO-controlled pool the mean cumulative follow up was 70.8 patient-years (py) on aficamten, and 66.3 py on PBO, and the total cumulative exposure period to aficamten was 205.2 py. The mean dose of aficamten in the cumulative pool was 12.6 mg/day. Treatment emergent serious adverse events (TESAE) occurred in 10 (5.9%) aficamten patients vs 14 (9.2%) PBO patients in the PBO-controlled pool, and in 24 (8.5%) aficamten patients in the cumulative pool. In the blinded phase, reported AEs were dizziness in 11 (6.5%) aficamten vs 3 (2%) PBO patients, syncope in 3 (1.8%) vs 4 (2.6%), dyspnea in 11 (6.5%) vs 8 (5.2%) and hypertension in 11 (6.5%) vs 4 (2.6%). Site-read LVEF &lt;50%, all resulting in down-titration occurred in 9 (5.3%) aficamten patients [exposure adjusted incidence rate (EAIR) 11.2 per 100 py] and 1 (0.7%) PBO patient (EAIR: 1.3 per 100 py), and in 11 (3.9%) aficamten patients in the cumulative pool (EAIR: 5.3 per 100 py). None of the LVEF &lt;50% events in aficamten patients were associated with heart failure symptoms; 1 PBO patient with a low LVEF had an AE of peripheral edema. During the maintenance phase of the cumulative exposure pool, 1588 echocardiograms were performed, of which 11 (0.7%) led to dose reduction due to LVEF &lt;50%, none resulted in discontinuation or treatment interruption. In the cumulative pool, 6 (2.1%) patients terminated treatment early, none due to aficamten-related AEs. New onset atrial fibrillation occurred in 4 (2.4%) aficamten (EAIR: 4.9 per 100 py) and 5 (3.3%) PBO patients (EAIR: 6.5 per 100 py). There were no deaths during the study period.

Conclusions
In this integrated safety analysis, aficamten had a safety profile similar to PBO and was consistent over an extended treatment period. There was a low incidence of LVEF &lt;50%, none of which were associated with clinical sequalae, and all were successfully managed by dose reduction. Monitoring echocardiography in the maintenance phase yielded very few actionable results.