This clinical trial is focused on studying a condition known as Transthyretin Amyloid Cardiomyopathy (ATTR-CM). ATTR-CM is a heart disease caused by the buildup of abnormal proteins called amyloids in the heart tissue, which can lead to heart failure. The study is testing a new treatment called ALXN2220, which is a type of medication known as a monoclonal antibody. Monoclonal antibodies are proteins made in a lab that can bind to specific substances in the body, in this case, the amyloid proteins, to help remove them.

The purpose of this study is to evaluate the effectiveness and safety of ALXN2220 in adults with ATTR-CM. Participants in the study will receive either the ALXN2220 treatment or a placebo, which is a substance with no active medication. The study will be conducted over a period of time, during which participants will receive regular injections of the treatment or placebo. Throughout the study, participants will be monitored for any changes in their heart condition and overall health.

The study aims to determine if ALXN2220 can help reduce the symptoms and progression of ATTR-CM by comparing the health outcomes of those receiving the treatment to those receiving the placebo. Participants will undergo various health assessments, including heart function tests and physical examinations, to track their progress. The study will provide valuable information on whether ALXN2220 is a safe and effective treatment option for people with ATTR-CM.