A Phase Ii Trial Of Onapristone In Combination With Fulvestrant For Patients With Er-Positive And Her2-Negative Metastatic Breast Cancer After Progression On Endocrine Therapy And Cdk 4/6 Inhibitors

Antiprogestins act as Progesterone Receptor (PgR) antagonists. 

Novel and promising class of drugs to overcome endocrine resistance associated with ESR1 mutations.

SMILE STUDY is a multi-institutional phase II clinical trial to determine the efficacy of an antiprogestin, Onapristone +fulvestrantas second line therapy for patients with HR+/HER2- metastatic breast cancer (MBC).

Hypothesis: The proposed combination of therapy with onapristone + fulvestrant is effective for patients with metastatic ER+, and or, PR+/-, HER-2 negative breast cancer with disease progression on Endocrine therapy and CDK 4/6 Inhibitors