Durvalumab-induced Type 1 Diabetes in a Patient With Pre-existing GADA-positive Diabetes and Preserved Insulin Secretion.

Predicting the onset of type 1 diabetes mellitus (T1D) in patients treated with immune checkpoint inhibitors (ICI) remains challenging. ICI-induced T1D (ICI-T1D) is a rare but serious complication that leads to complete insulin depletion. While diabetes-associated autoantibodies, such as glutamic acid decarboxylase antibodies (GADA), are typically absent in non-ICI-related fulminant T1D, they are relatively common in ICI-T1D. However, it is unclear whether these autoantibodies are detectable before the development of ICI-T1D. We present the case of a 61-year-old man with diabetes who had strongly positive GADA and preserved insulin secretion prior to initiating ICI therapy. Following treatment with durvalumab, he developed ICI-T1D, characterized by complete insulin depletion. Notably, the onset of ICI-T1D was precisely tracked on a daily basis, facilitating the timely initiation of insulin therapy and preventing diabetic ketoacidosis. Although the cost-effectiveness of pretreatment GADA screening and intensive monitoring remains a concern, early detection of diabetes-associated autoantibodies and vigilant glucose monitoring after ICI administration may help predict ICI-T1D and enable early therapeutic intervention.