This is a multicenter, open-label, Phase 3 study in up to approximately 1400 participants. Eligible participants will receive eplontersen once every 4 weeks for up to 36 months or 6 months after eplontersen is approved and available in the site's country, whichever occurs first. Participants will also receive daily supplemental doses of the recommended daily allowance (RDA) of vitamin A. This study will consist of the following periods: less than or equal to (≤) 10-week screening assessment period, up to 36-month treatment period, and up to 6-month post-treatment evaluation period.
The purpose of this study is to evaluate the safety and tolerability of extended dosing with eplontersen in participants with ATTR-CM.