An Extension Study of CORLUX in the Treatment of Endogenous Cushing's Syndrome

Inclusion Criteria: * Have completed the Week 24 visit and the 6-Week Follow-up visit of Corcept Study C-1073-400 (NCT00569582). * In the opinion of the Investigator, are expected to maintain clinical benefit from mifepristone. * Women of childbearing potential have a negative serum pregnancy test at Entry. * Women of childbearing potential must be willing to use non-hormonal, medically acceptable methods of contraception during the study. * Are able to provide written informed consent * Are able to return to the investigative site to complete the study evaluations outlined in the protocol. * Will not use systemic estrogens during the study. Exclusion Criteria: * Have an acute or unstable medical problem, which could be aggravated by mifepristone treatment. * Are taking medications within 14 days of the Entry visit that a) have a large first pass metabolism that is largely mediated by CYP3A4 and which have a narrow therapeutic margin; and/or b) are strong CYP3A4 inhibitors. * Female patients of reproductive potential, who are pregnant or who are unable or unwilling to use medically acceptable, non-hormonal methods of contraception during the study. * Have received investigational treatment (drug, biological agent or device) other than CORLUX (mifepristone) within 30 days of Entry * Have a history of an allergic reaction or intolerance to CORLUX (mifepristone) * Have uncorrected hypokalemia (potassium level of \<3.5 mEq/L) at Entry. Spironolactone or eplerenone is allowed to control hypokalemia. * Postmenopausal women with a history of endometrial hyperplasia with atypia or pathological features consistent with endometrial carcinoma. * Thickened endometrium on the Entry Visit transvaginal ultrasound that has not resolved after induction of menstrual bleeding with progesterone. * Uncontrolled, clinically significant hypothyroidism or hyperthyroidism. * Any woman with an intact uterus who has a hemorrhagic disorder or is being treated with an anticoagulant (e.g. warfarin, heparin). * Have renal failure as defined by a serum creatinine of ≥2.2 mg/dL. * Elevated total bilirubin \>1.5 ULN, elevated ALT or AST ≥3X the upper limit of normal.