Fazirsiran (ARO-AAT) is a second-generation RNAi agent. Fazirsiran consistes of a cholesterol-conjugated RNAi trigger (chol-RNAi) to selectively degrade Alpha1-antitrypsin (AAT) mRNA by RNAi and a melittin-derived peptide conjugated to N-acetylgalactosamine (NAG) formulated as the excipient EX1 to promote endosomal escape of the chol-RNAi in hepatocytes. Fazirsiran can be used in the study of Alpha-1 Antitrypsin Deficiency (AATD) liver disease.