Diabetic ketoacidosis as a hallmark of autoimmune diabetes occurring after two cycles of cemiplimab.

Introduction: Clinical indications of immune checkpoint inhibitors have expanded to a variety of malignancies. Nearly 50% of patients with advanced cutaneous squamous cell carcinoma, respond to the programmed-death 1 inhibitor cemiplimab. To date, insulin-dependent diabetes mellitus has been documented with the use of several immune checkpoint inhibitors but not cemiplimab.

Case Report: We report herein the first case of a patient with cutaneous squamous cell carcinoma who developed diabetic ketoacidosis and insulin-dependent diabetes mellitus following only two cycles of cemiplimab. A score of 6 on the Naranjo nomogram makes the causality relationship between cemiplimab use and the insulin-dependent diabetes mellitus probable.

Management And Outcome: The patient's developed diabetic ketoacidosis was managed with intravenous fluids and intravenous insulin, with a prompt resolution. Cemiplimab was discontinued, and the patient was discharged on long-acting and short-acting insulin therapy, with a follow-up with endocrinology.

Discussion/conclusions: The mechanism by which cemiplimab caused insulin-dependent diabetes mellitus is most likely due to lack of endogenous insulin production in the setting of immune-mediated loss of pancreatic beta-cells. Patients may benefit from fasting blood glucose monitoring and early immune checkpoint inhibitor discontinuation where elevated serum glucose is detected.