Drug-Drug Interaction Study of Entinostat and Exemestane in Postmenopausal Women With ER+ Breast Cancer

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). The cohorts will enroll sequentially, meaning that Cohort 1 will enroll prior to Cohort 2. Cohort 1 will evaluate exemestane's effect on the PK of entinostat. Cohort 2 will evaluate entinostat's effect on the PK of exemestane. In both Cohorts, each treatment cycle will be 28 days. Patients will participate in only one cohort. All patients will be assessed at Screening and at specified times during the conduct of the study using standard clinical and laboratory assessment. Patients will also be assessed for tumor response per standard of care after the Screening Period. Response to treatment will be assessed by computerized tomography (CT), magnetic resonance imaging (MRI) and bone scans as appropriate. Patients will continue receiving their appropriate cycles of study treatment until tumor progression or adverse events (AEs) occur which necessitate discontinuing therapy as determined by the Investigator.