This is an OLE study for subjects completing from one of two double-blind clinical
trials. Subjects must have completed the Week 13 visit from one of these two parent
clinical trials to be eligible for this OLE.

This study will evaluate the safety and effectiveness of the study drug belcesiran with placebo (an inactive drug treatment) in treating Alpha-1 Antitrypsin Deficiency-Associated Liver Disease AATLD. Belcesiran or placebo will be administered subcutaneously (via a shot) in the thigh or abdomen. About 46 people will take part in this study in about 30 hospitals and clinics worldwide. If deemed eligible, subjects will be randomized (assigned into a group by chance) into 1 of 3 study cohorts (groups). Subjects in Cohorts 1 will be dosed monthly to receive a total of 7 doses. Subjects in Cohort 2 will be dosed monthly to receive a total of 13 doses. Cohort 3 will be dosed monthly for the first 6 months and then quarterly thereafter for a total of 13 doses. Subjects will be given the option for extended treatment in an optional treatment period of an additional 4 to 6 doses of either belcesiran or placebo up to 72 weeks depending on group assignment. Subjects will then enter a follow up period for up to 96 weeks depending on group assignment. Study participation will last up to 192 weeks (3.5 years).