Mycophenolate mofetil for immune checkpoint inhibitor‐related hepatotoxicity relapsing during dose reduction of corticosteroid: A report of two cases and literature review

BACKGROUND: Immune checkpoint inhibitors (ICIs) sometimes cause immune‐related liver injury, which can lead to cessation of treatment, hospitalization, and even mortality. Although high‐dose corticosteroids are usually effective in treatment of ICI‐related liver injury, one fifth of affected patients require additional immunosuppressive therapy. It remains uncertain how best to treat ICI‐related liver injury that relapses under corticosteroid therapy after temporary remission. CASE: Here we report two cases of ICI‐related liver injury successfully treated with mycophenolate mofetil (MMF). In the first case, a 74‐year‐old man with stage IIIA lung cancer underwent curative chemoradiotherapy. After the second infusion of durvalumab, grade 3 ICI‐related liver injury (mixed pattern) developed. In the second case, a 46‐year‐old man with stage IVB lung cancer received pembrolizumab‐containing chemotherapy. After the first cycle, grade 2 ICI‐related hepatitis developed. In the both cases, liver injury improved with high‐dose prednisolone but relapsed during tapering of the drug. After liver biopsy was performed to confirm the diagnosis of ICI‐related liver injury, MMF (2000 mg/day) was added. MMF was effective for both patients and permitted discontinuation or reduction of prednisolone. CONCLUSION: MMF appears to be an appropriate treatment option for ICI‐related liver injury that respond to high‐dose corticosteroids but relapse during steroid tapering.