SAT-673 Acute Onset Type 1 Diabetes Mellitus Caused by the Checkpoint Inhibitor Nivolumab

Background. Checkpoint inhibitors are monoclonal antibodies that augment immune system antitumor activity. Nivolumab is a checkpoint inhibitor that targets the programmed cell death receptor 1 (PD-1). Approximately 15% of patients treated with checkpoint inhibitors experience endocrine immune-related adverse events (irAEs), with autoimmune thyroid disorders and hypophysitis the most common endocrine irAEs. We present a case of acute onset type 1 diabetes mellitus (T1D) complicating treatment with nivolumab. Case. An 84 year old female received nivolumab (Opdivo) for metastatic small cell lung cancer. She tolerated twelve cycles of treatment well, but after the thirteenth cycle, she developed polydipsia and polyuria that prompted her to seek medical attention. Laboratories in the emergency department were notable for plasma glucose 998 mg/dL, bicarbonate 13 mM, anion gap 24, and strongly positive serum and urine ketones. An insulin infusion and parenteral fluids promptly resolved diabetic ketoacidosis (DKA), and the patient was then managed with subcutaneous basal/bolus insulin. Antibody markers (e.g. anti-GAD65) for T1D were undetectable, and evaluation for other endocrine irAEs was unremarkable. Given the rapid onset of DKA and the patient’s advanced age, she was diagnosed with nivolumab-induced T1D and discharged home on exogenous insulin. Conclusions. In a recent meta-analysis of 38 immune checkpoint inhibitor trials and over 7,500 patients, T1D was the least common endocrine irAE. The incidence of T1D was 0.2% compared to 6.6% for hypothyroidism, 2.9% for hyperthyroidism, 1.3% for hypophysitis, and 0.7% for primary adrenal insufficiency. All but one case (12/13) of T1D occurred in patients treated with a PD-1 inhibitor. Markers of both cellular and humoral diabetes-associated autoimmunity have been demonstrated in patients with T1D during treatment with nivolumab, and autoimmune destruction of beta-cells is the presumed etiology of diabetes. However, diabetes autoantibodies are detected in only about 50% of cases, and the absence of humoral markers does not exclude the diagnosis of nivolumab-induced T1D. There is a slight male predominance among published cases of nivolumab-induced T1D, and though median onset of T1D1 is after 11 weeks of treatment, there is a wide range of recorded times to T1D onset. Approximately 70% of patients present in DKA, and the significant majority of patients have undetectable or low C-peptide levels. Unfortunately, loss of beta-cell function persists after stopping nivolumab, and lifelong exogenous insulin is required for diabetes management. Though nivolumab-induced T1D is rare, the high risk of DKA as in this patient’s case illustrates the importance of recognizing nivolumab as a potential cause of autoimmune diabetes in older patients receiving anti-PD-1 immunotherapy.