Study to Learn About the Safety of Fazirsiran and if it Can Help People With Alpha-1 Antitrypsin Liver Disease With Mild Liver Scarring (Fibrosis)

The liver produces a protein called alpha-1 antitrypsin (AAT). AAT is normally released into the bloodstream. In some people, the liver makes an abnormal version of the AAT protein, called Z-AAT. Making an abnormal version of the AAT protein can result in liver disease as Z-AAT builds up in liver cells, which leads to liver problems such as liver scarring (fibrosis), continuing liver damage (cirrhosis), and eventually endstage liver disease. Fazirsiran is a medicine that reduces the creation of the Z-AAT protein and thus the build-up of this abnormal protein in the liver. People with this type of liver disease who already have mild liver scarring will take part in the study. They will be treated with fazirsiran or a placebo for about 2 years. This study will check the long-term safety of fazirsiran, whether participants tolerate the treatment and if there are any effects on liver scarring. A liver biopsy, a way of collecting a small tissue sample from the liver, will be taken twice during the study.