A Phase 2a Study of ALN-PNP With and Without a GLP1R Agonist in Adult Patients With Homozygous PNPLA3-Related MASLD

This study will test a study drug called ALN-PNP with and without another drug that is used for controlling blood sugar, appetite, and weight (for example, tirzepatide), to see if it can help treat MASLD, also known as fatty liver disease. ALN-PNP reduces the amount of Patatin-like phospholipase domain-containing protein 3 (PNPLA3), a protein that liver cells make, which may help decrease liver fat if there is an abnormal PNPLA3 protein. The goal of this study is to understand the effect of ALN-PNP with or without tirzepatide on reducing liver fat. The study is looking at: * How well ALN-PNP with and without tirzepatide works * What side effects ALN-PNP might cause * How much ALN-PNP is in the blood at different times * How the body and the liver change after having ALN-PNP, which can help researchers understand why ALN-PNP works better in some people than others

Key Inclusion Criteria: Part A and Part B: 1. Homozygous for the PNPLA3 p.I148M genotype 2. Liver fat by Magnetic Resonance Imaging-Proton Density Fat Fraction (MRI-PDFF) ≥15% at visit 3 3. Has a Body Mass Index (BMI) ≥30 to \