Korlym (mifepristone)
An approved treatment for Cushing Disease.
The same compound appears under different names depending on the context. Here is how to identify Mifepristone wherever you encounter it, plus the key facts at a glance.
- Generic name
- Mifepristone
- Brand name
- Korlym
- Development codes
- RU-486, C-1073
- Drug class
- Glucocorticoid receptor antagonist
- Manufacturer
- Corcept Therapeutics
- How it's taken
- Taken by mouth once daily with a meal.
The first FDA-approved medication specifically for Cushing's syndrome. Unlike other treatments that lower cortisol levels, mifepristone blocks cortisol's effects at the receptor. Specifically approved for controlling hyperglycemia (high blood sugar) caused by excess cortisol in adults with Cushing's syndrome who have type 2 diabetes or glucose intolerance.
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Where Mifepristone fits
Unique mechanism among Cushing's treatments: blocks cortisol action at the receptor rather than reducing cortisol production. Specifically indicated for Cushing's patients with type 2 diabetes or glucose intolerance who cannot have surgery or for whom surgery failed.
How Mifepristone works
Rather than reducing how much cortisol the body makes, mifepristone blocks cortisol from attaching to its receptors throughout the body. Think of it as changing the locks so cortisol's key no longer works. This means cortisol is still produced (and blood cortisol levels may actually rise), but it can't trigger the harmful metabolic effects like high blood sugar, weight gain, and muscle weakness.
Mechanism: Glucocorticoid receptor antagonist that blocks cortisol from binding to its receptor
Side effects and safety
Common side effects include nausea, fatigue, headache, low potassium (hypokalemia occurred in 44% of patients in the trial), joint pain, vomiting, and peripheral edema. Because cortisol levels cannot be used to monitor treatment, there is a risk of adrenal insufficiency. Endometrial thickening occurs in women. Korlym has a boxed warning because it ends pregnancy. It must not be used during pregnancy: a negative pregnancy test is needed before starting and after any break in treatment of more than 14 days, and a non-hormonal birth control method is needed during treatment and for 1 month after stopping. Korlym can also prolong the QT interval (a change in heart rhythm), so it should be avoided with other drugs that do this, and people with Cushing's can develop a serious lung infection (Pneumocystis pneumonia) soon after starting. The label also warns about worsening of conditions treated with steroids, extra caution in people with heart disease because cortisol levels stay high, and the need for a lower maximum dose with strong CYP3A inhibitors.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Mifepristone
Taken by mouth once daily with a meal. Starting dose is 300 mg per day, which can be increased in 300 mg increments based on clinical response. Maximum dose is 1200 mg per day. Most patients respond at 300-900 mg per day.
Availability and cost
Generic versions may be available at a lower cost. Ask your pharmacist.
Only glucocorticoid receptor blocker approved for Cushing's syndrome. Narrow FDA indication limited to patients with hyperglycemia secondary to hypercortisolism.
Help paying for Korlym
Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.
- Copay help
A Co-Pay Assistance Program is available; eligibility is not stated on the page.
The official page does not say who qualifies. Ask the program. · source - Free medicine program
Patient Assistance Program for qualifying patients; free medication for eligible patients who have no insurance or were denied coverage.
For: no insurance · source - Bridge or quick-start supply
Free medication for eligible patients while they seek insurance approval.
The official page does not say who qualifies. Ask the program. · source - Insurance and case manager help
Patient Access Coordinator checks insurance benefits, helps with prior authorization and coordinates home delivery; 24/7 specialty pharmacist.
The official page does not say who qualifies. Ask the program. · source
Good to know: Korlym is not sold at retail pharmacies. The page does not say who qualifies for the copay program or what income limits apply.
- From a charity · HealthWell FoundationCushing's Disease or Cushing's Syndrome fundOpen
Pays for: Copays, premiums or other treatment costs.
- From a charity · NORD RareCareCushing's Syndrome Medical Assistance fundOpen
Pays for: Medical and medication costs.
The foundation says: “Accepting new applications and re-enrollments for current year” - From a charity · NORD RareCareCushing's Syndrome Premium Copay Assistance fundOpen
Pays for: Insurance premiums and copays.
The foundation says: “Accepting new applications and re-enrollments for current year” - From a charity · TotalAssist (formerly PAN Foundation)Cushing's Disease or Syndrome fundOpen
Pays for: Out-of-pocket costs for approved medications, up to $9,500 per year. Requires health insurance (any kind).
How Cushing disease treatments compare
Four FDA-approved medical therapies are available for Cushing's disease. Your endocrinologist will recommend a treatment based on the source of your excess cortisol, your blood sugar levels, surgical history, and how you respond to initial therapy. This chart summarizes the key practical differences between options.
4 FDA-approved cushing disease treatments are available: Isturisa (osilodrostat, approved 2020); Korlym (mifepristone, approved 2012); Recorlev (levoketoconazole, approved 2021); Signifor LAR (pasireotide, approved 2012). Isturisa is typically used as first-line medical therapy when surgery is not possible or has not been curative.
| Drug | How it works | How it’s given | How often | Where you get it | Typical use | FDA approved |
|---|---|---|---|---|---|---|
Isturisa osilodrostat | Cortisol synthesis inhibitor — blocks 11-beta-hydroxylase, the final enzyme step in cortisol production | Oral tablet | Twice daily | Home (self-administered) | First-line medical therapy when surgery is not possible or has not been curative | 2020 |
Korlym mifepristone You are here | Glucocorticoid receptor blocker — blocks cortisol from binding to its receptor (does not lower cortisol levels) | Oral tablet | Once daily with a meal | Home (self-administered) | For Cushing's patients with type 2 diabetes or glucose intolerance when surgery is not an option or has failed | 2012 |
Recorlev levoketoconazole | Cortisol synthesis inhibitor — blocks multiple steroidogenic enzymes including 11-beta-hydroxylase | Oral capsule | Twice daily with food | Home (self-administered) | For adults with Cushing's syndrome when surgery is not possible or has not been curative | 2021 |
Signifor LAR pasireotide | Pituitary-targeted somatostatin analog — suppresses ACTH secretion from the tumor, reducing the signal that drives cortisol production | Intramuscular injection (monthly) or subcutaneous injection (twice daily) | Monthly (LAR) or twice daily (subcutaneous) | LAR: doctor's office or infusion center; Subcutaneous: self-administered at home | For Cushing's disease (pituitary-dependent) when surgery is not an option or has failed; only drug that targets the tumor itself | 2012 |
This comparison is for FDA-approved medical therapies only and does not include surgical or radiation treatments, which are typically first-line for Cushing's disease. Always discuss treatment selection with your endocrinologist, who can factor in tumor size, cortisol severity, metabolic complications, and your individual response.
Clinical trial results
SEISMIC trial: open-label study of 50 patients with Cushing's syndrome and hyperglycemia or glucose intolerance. At 24 weeks, 60% of patients with diabetes achieved meaningful improvement in blood sugar control. Some patients reduced or eliminated their need for insulin.
Development history
FDA approved in February 2012 as the first drug specifically indicated for Cushing's syndrome. Mifepristone was previously known for other indications. Corcept Therapeutics repurposed it for the endocrine application.
Explore Cushing Disease trials
Other Cushing Disease treatments
Common questions about Mifepristone
▸What is Mifepristone (Korlym)?
The first FDA-approved medication specifically for Cushing's syndrome. Unlike other treatments that lower cortisol levels, mifepristone blocks cortisol's effects at the receptor. Specifically approved for controlling hyperglycemia (high blood sugar) caused by excess cortisol in adults with Cushing's syndrome who have type 2 diabetes or glucose intolerance.
▸How does Mifepristone work?
Rather than reducing how much cortisol the body makes, mifepristone blocks cortisol from attaching to its receptors throughout the body. Think of it as changing the locks so cortisol's key no longer works. This means cortisol is still produced (and blood cortisol levels may actually rise), but it can't trigger the harmful metabolic effects like high blood sugar, weight gain, and muscle weakness.
▸What are the side effects of Mifepristone?
Common side effects include nausea, fatigue, headache, low potassium (hypokalemia occurred in 44% of patients in the trial), joint pain, vomiting, and peripheral edema. Because cortisol levels cannot be used to monitor treatment, there is a risk of adrenal insufficiency. Endometrial thickening occurs in women. Korlym has a boxed warning because it ends pregnancy. It must not be used during pregnancy: a negative pregnancy test is needed before starting and after any break in treatment of more than 14 days, and a non-hormonal birth control method is needed during treatment and for 1 month after stopping. Korlym can also prolong the QT interval (a change in heart rhythm), so it should be avoided with other drugs that do this, and people with Cushing's can develop a serious lung infection (Pneumocystis pneumonia) soon after starting. The label also warns about worsening of conditions treated with steroids, extra caution in people with heart disease because cortisol levels stay high, and the need for a lower maximum dose with strong CYP3A inhibitors.
▸How is Mifepristone taken?
Taken by mouth once daily with a meal. Starting dose is 300 mg per day, which can be increased in 300 mg increments based on clinical response. Maximum dose is 1200 mg per day. Most patients respond at 300-900 mg per day.
▸Is Mifepristone FDA approved?
Yes, Mifepristone (Korlym) is FDA approved (2012) for the treatment of Cushing Disease.
▸How does mifepristone work differently from other Cushing treatments?
Unlike osilodrostat and levoketoconazole which reduce cortisol production, mifepristone blocks the glucocorticoid receptor where cortisol acts. It does not lower cortisol levels (which may actually rise) but prevents cortisol from exerting its harmful effects on tissues.
▸Why can't cortisol levels be used to monitor mifepristone treatment?
Because mifepristone blocks the cortisol receptor rather than reducing cortisol production, blood cortisol levels do not reflect treatment effectiveness. Doctors monitor clinical signs like blood sugar control, weight, and blood pressure instead.
▸What is the relationship between mifepristone for Cushing and RU-486?
Mifepristone was originally developed as RU-486 for reproductive health applications. Korlym uses the same molecule at higher doses specifically for controlling hyperglycemia in Cushing syndrome, marketed by Corcept Therapeutics.
▸Who is eligible for Korlym?
Korlym is specifically approved for controlling hyperglycemia (high blood sugar) secondary to hypercortisolism in adults with Cushing syndrome who have type 2 diabetes or glucose intolerance and have failed surgery or are not surgical candidates.
▸What are the main side effects of mifepristone for Cushing?
Common side effects include nausea, fatigue, headache, low potassium levels, and joint pain. Because it blocks the cortisol receptor, it can cause adrenal insufficiency symptoms. Women may experience vaginal bleeding or endometrial thickening.
▸Who manufactures Korlym?
Korlym is manufactured by Corcept Therapeutics, which has focused on developing glucocorticoid receptor modulators. It was approved in 2012 as the first glucocorticoid receptor antagonist for Cushing syndrome.