Korlym, also known as mifepristone, is the lead compound in Corcept's development portfolio. It is a small molecule which blocks the cortisol, or GR-II receptor. By blocking the receptor, Korlym reduces the receptor's activation by cortisol. Korlym is being evaluated for the treatment of Cushing's Syndrome and psychotic depression, severe unmet medical needs in which excess or irregular cortisol plays a role.

The active ingredient in Korlym, mifepristone, was discovered in 1980 in France by Roussel Uclaf. Mifepristone is approved in the United States and internationally for the termination of early pregnancy, as the compound blocks not only the cortisol receptor, but also the progesterone receptor. Mifepristone is approved for use in a physician's office as a single dose in combination with the drug misoprostol for the termination of early pregnancy in women with a confirmed uterine pregnancy of accurately predicted duration.

The composition of matter patents surrounding mifepristone expired in 1998. However, Corcept has licensed intellectual property from Stanford University to protect certain important methods of use for Korlym. In addition, Corcept also has been granted Orphan Drug Designation for Korlym for the treatment of endogenous Cushing's Syndrome in the United States which also may afford the company additional market exclusivity.