WALTHAM, Mass., Sept. 6, 2011 /PRNewswire/ -- Syndax Pharmaceuticals, Inc., a clinical-stage epigenetics oncology company, announced today that ENCORE 301, a randomized, placebo-controlled phase 2 study of exemestane with and without entinostat hit its primary endpoint of an improvement in progression-free survival (PFS). The study showed that patients who received entinostat, a novel, oral small molecule inhibitor of class I histone deacetylases, with the hormone therapy exemestane, lived longer without their disease getting worse than people who received exemestane alone. Safety and efficacy results from the trial will be presented in a poster and an oral presentation at the American Society of Clinical Oncology (ASCO) Breast Cancer Symposium 2011 in San Francisco, CA this week.