This clinical trial is focused on studying a condition called Transthyretin-Mediated Amyloid Cardiomyopathy (ATTR-CM). ATTR-CM is a heart disease where abnormal proteins build up in the heart, affecting its function. The study will test a treatment called ION-682884, also known as Eplontersen, which is a type of medication called an antisense oligonucleotide. This medication is designed to target and reduce the production of the abnormal protein causing the disease. Participants in the study will receive either the ION-682884 treatment or a placebo, which is an inactive substance that looks like the treatment but does not contain the active medication.

The purpose of the study is to evaluate the effect of ION-682884 on heart-related health outcomes in patients with ATTR-CM. Participants will receive regular injections under the skin and will be monitored over a period of time to assess the treatment’s impact on their heart health. The study will compare the number of heart-related events, such as heart failure or heart attacks, between those receiving the treatment and those receiving the placebo. The study aims to determine if ION-682884 can improve the health and quality of life for people with ATTR-CM.

Throughout the study, participants will continue to receive their usual care for ATTR-CM. The study will involve regular visits to the clinic for health assessments and to receive the injections. The overall goal is to see if ION-682884 can reduce the risk of serious heart problems and improve the well-being of patients with this condition. Participants’ health and safety will be closely monitored by the study team throughout the trial.