Mifepristone and Eribulin in Patients With Metastatic Triple Negative Breast Cancer or Other Specified Solid Tumors

There will be two parts to the study: Part 1, a dose escalation phase, in which the MTD and RP2D will be determined in up to 20 patients with metastatic breast or other specified solid tumors, regardless of receptor status; and Part 2, a dose expansion phase in which a preliminary estimate of efficacy will be made in an expansion group of up to 20 patients with glucocorticoid receptor-positive metastatic TNBC at the RP2D. Treatment will be administered in 21-day cycles, with the exception of the first cycle, which will be of 28 days duration with a lead-in of 7 days dosing of mifepristone. Cycle 1 (28-day cycle): Mifepristone administered orally (PO) with food once daily for 28 days. Eribulin will be administered intravenously (IV) over 2 to 5 minutes on days 8 and 15. Cycle 2 and beyond (21-day cycle): Mifepristone administered orally (PO) with food once daily for 21 days. Eribulin will be administered intravenously (IV) over 2 to 5 minutes on days 1 and 8. Enrollment in Part 2 of the study (dose expansion) will occur once the RP2D has been determined. Patients in the dose expansion study must have TNBC disease that is glucocorticoid receptor-positive (by immunohistochemistry \[IHC\]). Patients will be treated in repeated 21-day cycles until progression or another withdrawal criterion is met. Part 1 of the study is complete. Part 2 of the study is ongoing.