Cell Based Assay: This assay was used to measure PI3K-alpha inhibition in cells. BT474 cells (human breast ductal carcinoma, ATCC HTB-20) were seeded into black 384 well plates (Costar, #3712) at a density of 5600 cells/well in DMEM containing 10% FBS and 1% glutamine and allowed to adhere overnight.The following morning compounds in 100% DMSO were added to assay plates by acoustic dispensing. After a 2 hour incubation at 37 C. and 5% CO2, the medium was aspirated and the cells were lysed with a buffer containing 25 mM Tris, 3 mM EDTA, 3 mM EGTA, 50 mM sodium fluoride, 2 mM Sodium orthovanadate, 0.27M sucrose, 10 mM beta-glycerophosphate, 5 mM sodium pyrophosphate, 0.5% Triton X-100 and complete protease inhibitor cocktail tablets (Roche #04 693 116 001, used 1 tab per 50 ml lysis buffer).After 20 minutes, the cell lysates were transferred into ELISA plates (Greiner #781077) which had been pre-coated with an anti total-AKT antibody in PBS buffer.