A Case of Grade 4 Hyperglycemia Induced by Capivasertib and Successfully Managed with Early Insulin Intervention

Capivasertib, a protein kinase B (AKT) inhibitor, has demonstrated robust efficacy against hormone receptor-positive, human epidermal growth factor receptor type 2-negative advanced breast cancer, particularly in patients with AKT pathway mutations. However, serious metabolic complications such as hyperglycemia and diabetic ketoacidosis (DKA) have been reported. This case report describes capivasertib-induced hyperglycemia to support the development of safe treatment and monitoring strategies. The case is notable because early detection and timely intervention following the rapid onset of grade 4 hyperglycemia resulted in a favorable clinical course without long-term glycemic complications.

A 69-year-old woman without diabetes developed grade 4 hyperglycemia (522 mg/dL) on day 2 after receiving capivasertib in combination with fulvestrant therapy. Pretreatment glucose tolerance test results were normal. Continuous insulin infusion was promptly initiated in response to the rapid increase in blood glucose levels to prevent ketosis. Her blood glucose levels improved within half a day, and she was discharged on day 6. She did not require further insulin or hypoglycemic agents thereafter.

Inpatient glucose monitoring enabled prompt detection of rapid glucose elevation and early intervention before the onset of DKA, resulting in a favorable outcome. Further clinical evidence is required to define optimal intervention strategies for grade 4 hyperglycemia associated with capivasertib therapy.