A Randomized, Phase II Study for Premenopausal Metastatic or Locally Advanced Breast Cancer Patients: Capivasertib, Goserelin, Fulvestrant With/Without Durvalumab, Versus Goserelin, Fulvestrant, and Durvalumab, Versus Goserelin/ Fulvestrant.

This is an open-label randomized phase II study in estrogen receptor positive locally advanced or metastatic breast cancer patients. The main inclusion population are either luminal subtype B by PAM50 analysis or failed less than 2 lines of hormonal therapy for locally advanced or metastatic breast cancer. The subjects have to be premenopausal or perimenopausal and are not allowed to receive any systemic chemotherapy for their locally advanced or metastatic breast cancer. Eligible subjects will be randomized into goserelin/ fulvestrant/ durvalumab (Arm A), goserelin/ fulvestrant/ capivasertib/ durvalumab (Arm B), or goserelin/ fulvestrant/ capivasertib (Arm C) at a 1:1:1 ratio. The primary endpoint is objective response rate (ORR) of the whole other three arm compared to historical goserelin/ fulvestrant control arm. The major secondary endpoint will be progression-free survival or ORR compared among different treatment arms. Secondary endpoints include PFS and ORR comparison between arms. Exploratory endpoints include biomarkers, such as TILs, PD-L1 correlation with treatment response.