ACTA ENDOCRINOLOGICA (BUC)

Context. Phosphoinositide-3-kinase (PI3K) pathway inhibitors are increasingly used as targeted therapy in malignancies. We discuss here three cases of PI3K inhibitor induced hyperglycemia and discuss the mechanism of action of these medications and treatment of this class side effect. Objectives. Alpelisib (Piqray) is the newest PI3K inhibitor used in conjunction with Fulvestrant to treat specific types of breast cancer. Since PI3K is a critical mediator of insulin signaling, hyperglycemia is an on-target, unfortunate side effect of this treatment. We present a case series of severe hyperglycemia induced by the alpelisib in three women without a history of diabetes. Design. All three women in this study had hormone receptor (HR) positive, human epidermal growth factor receptor 2 (Her2) negative, PI3K mutated breast cancer. They were referred to our clinic by Oncology for alpelisibinduced hyperglycemia. Subjects and Methods. Review of laboratory values and glucometer values were conducted during each visit allowing treatment decisions. Two of these women are actively managed by us for their diabetes. One woman recently died due to progression of malignancy. Results. All three women presented with new onset of severe hyperglycemia after the initiation of PI3K inhibitor, alpelisib. At least one case noted maximal glucose elevation in the hours following drug ingestion. In another, cessation of Alpelisib reversed the hyperglycemia within the span of one week. Conclusion. Hyperglycemia induced by PI3K inhibitors can be recalcitrant and might necessitate interruption of chemotherapy. Optimal glucose-lowering therapy remains unclear as exogenous insulin has the theoretical potential to overcome PI3K inhibition.