Exploratory data from these single agent trials is consistent with relevant signalling inhibition based on pre- and post-treatment tumour biopsies (increase in phospho-AKT, reduction in phospho-GSK3β and phospho-PRAS40) and clinical activity in patients with PIK3CA-mutant breast cancer and in patients with tumour AKT1 (E17K) mutations [18, 19]. Here, AKT1 is linked to breast cancer.