CTLA4 and clostridium difficile infection: In four cases CDI appeared as an isolated endocrine irAE induced by avelumab (an anti-PD-L1 monoclonal antibody, anti-PD-L1-mAb) (25), sintilimab (an anti-PD1-mAb (27) or nivolumab (an anti-PD1-mAb) (26) as single agents; in the case CDI was attributed to combination treatment: tremelimumab + durvalumab (an anti-CTLA4-mAb and an anti-PD-L1-mAb, respectively) (28).