This study is checking if a medicine called **eplontersen** is safe for people with a heart condition called **ATTR-CM** (Transthyretin-Mediated Amyloid Cardiomyopathy). In this study, people will get eplontersen every four weeks for up to 3 years or until the drug is approved in their country, along with daily vitamin A. The study has different parts: a screening check-up that can last up to 10 weeks, a treatment period that can be up to 36 months, and a follow-up period of up to 6 months. To join, you must have completed a previous related study or have ATTR-CM and agree to take vitamin A. You cannot join if you stopped the study drug in the past or have any new health issues that make joining unsafe.

• The study lasts up to 3 years with regular medicine doses.
• Participants must take vitamin A daily.
• Ensure to complete preliminary and follow-up checks.