Toripalimab-associated diabetes mellitus: a case report from the community of Southern China.

Summary: Immune checkpoint inhibitors (ICPis) are novel immunotherapy drugs for a variety of cancers. Toripalimab is one of the ICPis that selectively blocks programmed death 1 (PD-1) and has been used for the treatment of malignant cancers in the hospitals of China. But with the widespread use of ICPis, some of the adverse reactions have gradually appeared. One of the most serious side effects is diabetes mellitus which is a relatively rare immune-related adverse event (irAEs) with life-threatening complications. We report a case of diabetes after the administration of toripalimab for the treatment of melanoma in southern China. To our knowledge, this is a rare case of diabetes occurring during toripalimab therapy, there is only one similar case reported in China so far. As China has a high morbidity of malignant cancer, a significant number of patients could be affected by the adverse reactions of using ICPis. Therefore, when ICPis are administrated, it is very important for clinicians to pay attention to one of the serious side effects - diabetes mellitus. Insulin therapy is often necessary after the diagnosis of ICPis-related diabetes, which has been proved as an effective method to prevent diabetic ketoacidosis (DKA) and other life-threatening complications in these patients. Learning points: Toripalimab can cause the diabetes mellitus. ICPis-related diabetes is treated primarily with insulin. Immune checkpoint inhibitors cause diabetes by primarily destroying islet β cells. There is not enough evidence to demonstrate that diabetic autoantibodies are related to diabetes caused by ICPis. In addition to focusing on the efficacy of PD-1 inhibitor therapy, it is also necessary to pay attention to its adverse reactions, such as ICPis-related diabetes mellitus.