Novel Fluorinated Antiinflammatory Steroid with Reduced Side Effects: Methyl 9α-Fluoroprednisolone-16-carboxylate

Abstract

In an effort to test the hypothesis that 9α-fluorination of a steroidal antedrug would enhance receptor binding affinity and local antiinflammatory activity, without concomitantly increasing adverse systemic effects, a fluorinated analog,10, of methyl 11β,21-dihydroxy-3,20-dioxo-1,4-pregnadiene-16α-carboxylate (DP16CM,1) was synthesized and evaluated. In the acute rat croton oil-induced ear edema bioassay,10was found to be twice as potent as1. This increase in topical potency was consistent with enhanced binding affinity of10, relative to1. The IC50values for displacement of [3H] dexamethasone from glucocorticoid receptors of rat hepatoma tissue culture cells were 0.16, 1.2, and 0.03 μM for10, 1, and prednisolone, respectively. Following multiple topical ID50applications of prednisolone,1, and its new fluorinated analog,10, in the rat subacute croton oil-induced ear edema bioassay, only prednisolone exhibited significant untoward effects, such as reduction in relative thymus and adrenal weights, plasma corticosterone levels, and normal body weight gain. Thus, while fluorination of1enhanced its topical potency, there was not a concomitant increase in untoward systemic effects. This lack of adverse systemic effects is ostensibly due to the presence of the metabolically labile 16-carboxylate ester moiety.