16a-Methyl corticosteroids; a new series of anti-inflammatory compounds; clinical appraisal of their antirheumatic potencies.

Four new derivatives of hydrocortisone, each containing in common a methyl grouping at the 16a-carbon position of the steroid molecule, have been synthesized and are being studied in human subjects. The compounds are 16a-methyl 9a-fluoroprednisolone (MK-125: hexadecadrol), 16a-methyl 9a-fluorohydrocortisone (MK-126), 16a-methylprednisolone (MK-110), and 16a-methylhydrocortisone (MK-117). Biologic tests in animals have indicated that these analogues exhibit, in varying degrees, striking alterations of several physiologic properties, including enhanced anti-inflammatory activity unassociated with corresponding disturbance of electrolyte metabolism. In the present study preliminary observations of the effects of the four new compounds were made in patients with rheumatoid arthritis. Clinical estimates of the antirheumatic potencies of the compounds, as compared with prednisolone, were accomplished by determining the milligram dosages required to maintain similar degrees of improvement of active rheumatoid manifestations. The approximate antirheumatic potencies of the compounds, on an average, were gauged as follows: for 16a-methyl 9a-fluoroprednisolone, about seven times greater than prednisolone; for 16a-methyl 9a-fluorohydrocortisone, about three times greater; for 16a-methylprednisolone, approximately one-third greater; and for 16a-methylhydrocortisone, about 70 per cent that of prednisolone. In the dosage used, none of the compounds promoted discernible salt and water retention. These observations would indicate that 16a-methyl 9a-fluoroprednisolone (hexadecadrol) possesses greater anti-inflammatory potency per milligram than any steroid yet produced. The therapeutic efficiency of the compound on longterm administration is being studied.