A Trial to Learn if Receiving ALN-PNP siRNA is Safe and Well Tolerated, and How it Works in Adult Participants With Nonalcoholic Fatty Liver Disease (NAFLD) and a Genetic Risk Factor

This study is researching an experimental drug called ALN-PNP. This study is focused on participants who are known to have nonalcoholic fatty liver disease (NAFLD), and a specific variant of the patatin-like phospholipase domain containing 3 (PNPLA3) gene. The aim of this study is to see how safe, tolerable, and effective the study drug is. This study is looking at several other research questions, including: * What side effects may happen from taking the study drug * How the study drug works to change liver fat content in NAFLD * How much study drug and study drug metabolites (byproduct of the body breaking down the study drug) are in your blood at different times * Whether the body makes antibodies against the study drug (which could make the drug less effective or could lead to side effects) * Better understanding of the study drug and NAFLD