Our findings using endocrine-resistant breast cancer cell lines demonstrate for the first time that dual targeting of mTORC1 and mTORC2/AKT signalling with an mTOR kinase inhibitor (AZD8055) can be effective even under conditions in which the allosteric mTORC1 inhibitor RAD001 (everolimus) fails to control growth. Here, AKT1 is linked to breast cancer.