A case with hepatic immune-related adverse events caused by nivolumab exhibiting impaired accumulation of regulatory T cells.

Systemic administration of anti-programmed cell death 1 (PD-1) antibody (Ab) has achieved remarkable success in metastatic cancers. The blockade of PD-1-mediated signaling pathways sometimes cause immune-related adverse events (irAEs) due to restored anti-cancer as well as anti-self immunity. Although the liver is a preferential organ for irAEs, the immuno-pathogenesis underlying hepatic irAEs has been poorly understood. We describe a 57-year-old man with Stage IV lung cancer who underwent the first-line regimen composed of carboplatin and paclitaxel. Nivolumab treatment (3.2 mg/kg, every 3 weeks) was initiated when the disease progressed after the first chemotherapy. Sequential occurrence of irAEs involving the multiorgan systems was observed. He developed hepatic irAEs (Grade 3) after endocrine, lung, and cutaneous irAEs. Lobular hepatitis characterized by predominant infiltration of CD8 T cells was seen in the liver biopsy specimens. Interestingly, defective accumulation of regulatory T cells (Tregs) expressing forkhead box protein P3 (FOXP3) was evident in this case with hepatic irAEs as compared with typical cases with autoimmune hepatitis. This case suggests that hepatic irAEs are characterized not only by lobular infiltration of CD8 T cells but also by defective accumulation of FOXP3 Tregs.