SNDX-275-0130 is a Phase 1, two-cohort, open-label, drug-drug interaction study of entinostat and exemestane. All patients will be enrolled into one of two cohorts to receive either entinostat monotherapy followed by entinostat plus exemestane (Cohort 1), or exemestane monotherapy followed by exemestane plus entinostat (Cohort 2).