In the global CAPItello-291 randomized phase 3 study (NCT04305496) in patients with hormone receptor-positive/HER2-negative advanced breast cancer and progression during/after aromatase inhibitor treatment, capivasertib–fulvestrant significantly improved progression-free survival (PFS) in the overall population and patients with PIK3CA/AKT1/PTEN-altered tumors versus placebo–fulvestrant. This evidence concerns the gene AKT1 and breast cancer.