MK-126

MK-126 (16a-methyl 9a-fluorohydrocortisone) is a synthetic corticosteroid developed by Merck & Co. in the late 1950s. It is a derivative of hydrocortisone featuring a methyl group at the 16a-position and a fluorine atom at the 9a-position. In early clinical evaluations for rheumatoid arthritis, MK-126 demonstrated approximately three times the anti-inflammatory potency of prednisolone. The addition of the 16a-methyl group was a significant structural modification intended to mitigate the salt-retaining properties typically associated with 9a-fluorinated steroids. Although MK-126 showed significant biologic activity and therapeutic potential without discernible electrolyte disturbances at tested doses, it was ultimately overshadowed by its unsaturated analogue, 16a-methyl 9a-fluoroprednisolone (MK-125), which became widely known as dexamethasone.

Other names

16a-methyl 9a-fluorohydrocortisone9a-fluoro-16a-methylhydrocortisone16alpha-methyl-9alpha-fluorohydrocortisone