Evexomostat Plus PI3K or AKT Inhibitor and Fulvestrant in Patients With a PI3K Alteration and HR+/Her2- Breast Cancer

This is a Phase 1b/2, open-label, parallel-arms pilot study in men and post-menopausal women with hormone receptor positive (HR+), HER2- advanced or metastatic breast cancer with an alteration in the PI3K pathway, including a mutation of the PIK3CA gene, PTEN loss, or AKT1 mutation, designed to determine the safety of evexomostat (SDX-7320) plus standard of care treatment alpelisib (BYL-719) or capivasertib and fulvestrant (each combined, the 'triplet therapy'), to measure the severity and number of hyperglycemic events, and to assess clinical, anti-tumor benefit of the triplet therapy. The purpose of this study is: * to characterize the safety of the triplet drug combination consisting of either alpelisib or capivasertib (per the treating oncologist's choice) and fulvestrant plus evexomostat, * to test whether evexomostat, when given in combination with either alpelisib or capivasertib and fulvestrant will reduce the number and severity of hyperglycemic events and/or reduce the number or dose of anti-diabetic medications needed to control the hyperglycemia for metabolically normal patients and those deemed at risk for capivasertib and alpelisib-induced hyperglycemia (insulin resistance, as measured by HOMA-IR, baseline elevated HbA1c or well-controlled type 2 diabetes), and * to assess preliminary anti-tumor efficacy for each combination and changes in key biomarkers and quality of life in this patient population.