**TReatment for ImmUne Mediated PathopHysiology (TRIUMPH) Study** The TRIUMPH study looks at treatments for children with acute liver failure, a serious condition where the liver suddenly stops working. This research will test if certain medicines, called *corticosteroids* and *equine anti-thymocyte globulin* (eATG), can help these kids by calming their immune systems. An *immune system* is the body's defense against infections and diseases. The study involves 160 children aged 1-18 years and will take place at 20 hospitals in the United States. In this study, children are randomly placed into one of three groups: one gets high-dose *methylprednisolone* (a type of corticosteroid), another gets eATG, and the last group gets a placebo (a harmless pill). The treatment lasts 4 days, followed by a gradual lowering of the medicine or placebo for up to 42 days. Participants will have follow-up visits for a year to monitor progress. - **Length of Study:** Treatment lasts up to 42 days with follow-ups for a year. - **Visits Needed:** Includes several follow-ups in the first month and then more spaced out visits. - **Potential Benefits/Risks:** May improve liver health but involves testing new treatments. **Note:** Always discuss study participation with your healthcare provider to understand the possible risks and benefits.