Ertugliflozin/Metformin Hydrochloride

First time in patients study of AZD8835. The study has four parts. Part A AZD8835 is administered as a single agent in a multiple ascending dose escalation phase to investigate dose level for monotherapy. Part B follows the multiple ascending dose phase, additional patients with tumors with documented PIK3CA gene mutation will be enrolled to a single dose expansion phase. Part C is a second dose escalation phase in which post-menopausal patients with estrogen receptor positive (ER+), HER2 negative breast cancer will receive AZD8835 in combination with fulvestrant. Part D follows the combination dose escalation phase of the study, additional postmenopausal patients with ER+/HER2 negative breast cancer with documented PIK3CA gene mutation will be enrolled to a AZD8835 and fulvestrant combination dose-expansion phase at maximum tolerated dose or recommended phase II dose.