Mycophenolate Mofetil w/ Prednisone for Immune Related Hepatitis From Checkpoint Inhibitor Therapy

Inclusion Criteria: * Patients must be ≥ 18 years at the time of irAE diagnosis and must have been diagnosed with a solid tumor or hematologic malignancy being treated with non-curative intent. * Patients must be diagnosed or presumed to have by a treating Medical Oncology or Hematology-Oncology clinician with immune-related hepatitis, G2-G3 (as defined in section 11.0), with plan for at least temporary interruption of IO therapy and initiation of corticosteroid treatment. * Patients must have been previously treated for any malignancy with at least one dose of an IO agent targeting the Programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PDL-1) or CTLA-4 axis. IO use may have occurred at any time prior to diagnosis of irAE. * Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin must have been measured within screening window outlined in Section 8.0 (Study Calendar). * Patient must be able to take study medications by mouth. * Baseline hemoglobin (HgB) at time of enrollment ≥8.0 g/dL, absolute neutrophil count (ANC) ≥ 1500/mm3, and platelet count ≥ 100,000/mm3 without red blood cell or platelet transfusion in the two weeks preceding measurement of lab values. Lab values are to be assessed within screening window outlined in Section 8.0 (Study Calendar). * Baseline estimated Glomerular Filtration Rate (eGFR) \< 30 mL/min/1.73m2 * Patients must be able to understand and willing to sign a written informed consent and HIPAA consent document. Exclusion Criteria: * Patients previously treated for irAE hepatitis. * Patients diagnosed or presumed to have G4 immune-related hepatitis. * Patients receiving renal replacement therapy with hemodialysis or peritoneal dialysis at time of enrollment. * Patients with a documented history of Child-Turcotte-Pugh class B and C liver dysfunction. * Patients with significant liver dysfunction at time of presentation, as defined by an otherwise unexplained change in mental status or International Normalized Ratio (INR) ≥ 1.5 attributed to synthetic liver dysfunction. * Patients with active hepatitis B (HBV), hepatitis C (HCV), or tuberculosis. Confirmatory testing for these infections may be performed if no recent result is available in the patient's records and, in the opinion of the treating physician, such testing is clinically warranted. Past HBV is exclusionary. Patients with treated HCV infection and documented eradication are eligible to enroll. * Patients with uncontrolled human immunodeficiency virus (HIV), Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpes simplex virus (HSV), or Varicella-zoster virus (VZV). Confirmatory testing for these infections is not required. * Patients with a history of gastrointestinal bleeding, ulceration, or perforations within one year of trial enrollment. Use of proton-pump inhibitor therapy is allowed. * Patients with any history of solid organ or allogeneic stem cell transplantation. * Patients with type I diabetes mellitus (DM). * Patients with type II DM with most recent glycated hemoglobin measurement greater than or equal to 9.0%. * Patients with a documented history of phosphoribosyl-transferase deficiency. * History of allergic reactions to MMF, prednisone, methylprednisolone, or dexamethasone. * Patients with decompensated congestive heart failure at time of enrollment, at the discretion of treating clinician, regardless of ejection fraction. * Patients with history of suicidal ideation or past suicide attempt. * Uncontrolled or intercurrent severe medical illness at the time of enrollment, as defined below: 1. Patients being treated with vasopressors 2. Patient requiring mechanical ventilation or extracorporeal membrane oxygenation 3. Patients being treated with parenteral antibiotic, antifungal, or antiviral medications * Patients with chronic autoimmune diseases requiring long-term immunosuppressive treatment at the time of enrollment, or for whom the mechanism of index inflammatory changes is too uncertain to initiate irAE-directed treatment at the discretion of treating provider. * Patients with congenital (e.g. combine variable immunodeficiency) or acquired (e.g. chronic leukemia) immunodeficiency requiring long-term prophylactic antimicrobial treatment at time of enrollment (e.g. intravenous immunoglobulin (IVIg), prophylactic antiviral treatment, etc.) * Women of child-bearing potential (WOCBP) who are pregnant or breast-feeding. * Patients unable to commit to use of reliable contraception throughout the study period.