Study to Determine the Prevalence of Hypercortisolism in Patients With Type 2 Diabetes and Treatment With Korlym® (Mifepristone) (CATALYST)

For Part 1: Inclusion Criteria: Has difficult to control T2D (HbA1c ≥7.5% and ≤11.5%) based on HbA1c performed at screening. AND Taking 3 or more anti-hyperglycemic drugs. OR Taking insulin and other anti-hyperglycemic drugs. OR Taking 2 or more anti-hyperglycemic drugs AND a.) the presence of 1 or more micro-vascular or macro-vascular complication (retinopathy, diabetic nephropathy and chronic kidney disease, diabetic neuropathy, atherosclerotic heart disease with diabetes); AND/OR b.) concomitant hypertension requiring 2 or more anti-hypertension medications. • Women on oral contraceptive pills (OCPs) may be screened but must be willing and able to stop OCPs for at least 3 weeks prior to the dexamethasone suppression test. Exclusion Criteria: * Has type 1 diabetes mellitus. * New-onset diabetes less than 1 year. * Systemic glucocorticoid medications exposure (excluding inhalers or topical) within 3 months of screening. * Is pregnant or lactating. For women of childbearing potential, have a positive pregnancy test before dexamethasone administration. A woman of childbearing potential includes all women \<50 years old, women whose surgical sterilization was performed \<6 months ago, and women who have had a menstrual period in the last 12 months. * On hemodialysis or has end-stage renal disease. * Has severe untreated sleep apnea as judged by the Investigator. * Has excessive alcohol consumption (\>14 units/week for male, \>7 units/week for female) as judged by the Investigator. * Has severe psychiatric illness by history (such as schizophrenia or dementia) as judged by the Investigator. * Has severe medical or surgical illness as judged by the Investigator. * Is a night shift worker, i.e., is awake from approximately 11 PM to 7 AM. * Has taken any investigational drug within 4 weeks prior to screening, or within less than 5 times the drug's half-life, whichever is longer. * Has had the diagnosis of Cushing syndrome or has used or plans to use any of the following treatments for Cushing syndrome: \- Mifepristone, metyrapone, osilodrostat, ketoconazole, fluconazole, aminoglutethimide, etomidate, octreotide, larazotide, pasireotide, long-acting octreotide or pasireotide. * Has a history of hypersensitivity or severe reaction to dexamethasone For Part 2: Inclusion Criteria: * Has completed Part 1 of the study with post-DST cortisol level of \>1.8 μg/dL and dexamethasone level ≥140 ng/dL * Will have no change in, or initiation of, diabetes medications within 4 weeks prior to first study drug dose Exclusion Criteria: * Has any change in status of exclusion criteria from Part 1 * Requires inhaled glucocorticoid use and may require systemic glucocorticoids if their condition deteriorates during study * Has severe, poorly controlled hypertension at screening (defined as mean systolic BP \>160 mmHg or mean diastolic BP \>100 mmHg); must be able to correct to a BP of \<160/100 mmHg before first dose of study drug * Has refractory hypokalemia; must be able to correct to potassium level of ≥4.0 mEq/L before first dose of study drug * Has poorly controlled hyperthyroidism/hypothyroidism before first dose of study drug (confirmed by TSH or free thyroxine) * Has plans for adrenalectomy or adrenal nodulectomy * Has renal insufficiency (eGFR \<30 mL/min/1.73m2) * Has liver test results \>3x ULN (ALT or AST) or bilirubin \>1.5x ULN * Takes drugs metabolized by CYP3A and CYP3A substrates with narrow therapeutic ranges * Receiving systemic corticosteroids that cannot be discontinued * Uses hormonal contraceptives * Has a history of unexplained vaginal bleeding, endometrial hyperplasia with atypia, or endometrial carcinoma * Is pregnant or lactating * Has a known hypersensitivity to mifepristone or any of the product components