This is a multicenter, open-label, Phase 3 study in up to approximately 140 participants. Eligible participants will receive Eplontersen once every 4 weeks for up to 157 weeks. 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 (≤) 8-week screening period, a 157 weeks treatment period, and a 24-week post-treatment evaluation period.
The purpose of this study is to evaluate the safety and tolerability of extended dosing with Eplontersen in participants with hereditary transthyretin-mediated amyloid polyneuropathy (hATTR-PN).