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.
The purpose of this study is to determine the effect of exemestane on the pharmacokinetics (PK) of entinostat and to determine the effect of entinostat on the PK of exemestane in patients with locally recurrent or metastatic estrogen receptor positive (ER+) breast cancer. Additionally, this study will evaluate the safety and tolerability of entinostat in combination with exemestane, and assess the effectiveness of entinostat in combination with exemestane in terms of best overall response and overall survival.