New steroidal antiinflammatory antedrugs: Methyl 3,20-dioxo-9 alpha-fluoro-11 beta,17 alpha,21-trihydroxy-1,4-pregnadiene-16 alpha-carboxylate and its 21-O-acyl derivatives

In a continuing effort to increase local to systemic activity ratios of potent steroidal antiinflammatory antedrugs, a series of 21-O-acyl derivatives of methyl 3,20-dioxo-9 alpha-fluoro-11 beta,17 alpha,21-trihydroxy-1,4-pregnadiene-16 alpha-carboxylate, FP16CM, were synthesized. These derivatives were evaluated for antiinflammatory activity and their adverse effects in an acute and semi-chronic croton oil-induced ear edema bioassay. Following a single topical application in the croton oil-induced ear edema bioassay, treatment with all the compounds resulted in dose-dependent inhibition of edema. From these dose-response profiles, the following ID(50) values (nmol/ear resulting in a 50% reduction of edema) were calculated: prednisolone (Pred); 454, FP16CM; 255, 21-acetate (FP16CM-acetyl); 402, 21-propionate (FP16CM-propionyl); 474, 21-valerate (FP16CM-valeryl); 446 and 21-pivalate (FP16CM-pivalyl); 219 nmol. In a 5-day semi-chronic study at the equipotent doses, the novel steroidal antedrugs did not significantly alter body weight gain, thymus weights or plasma corticosterone levels unlike the parent compound Pred. The compounds were assessed for high-affinity glucocorticoid receptor binding and glucocorticoid-mediated inhibition of nitric oxide (NO) generation in an in vitro RAW 264.7 macrophage cell culture system. Binding affinities for cytosolic glucocorticoid receptors were Pred; 85, FP16CM-acetyl; 86, FP16CM-propionyl; 169, FP16CM-valeryl; 149, FP16CM-pivalyl; 126 nM, respectively. Concomitant potencies for inhibition of NO generation by macrophages stimulated with lipopolysaccharide were Pred; 159, FP16CM-acetyl; 377, FP16CM-propionyl; 405, FP16CM-valeryl; 344, FP16CM-pivalyl; 311 nM, respectively. Collectively, results of these investigations suggest that esterification of 21-OH with various anhydrides did not improve receptor binding, inhibition of NO generation and ear edema inhibition, however, serum corticosterone level and local over systemic activities (L/S) were markedly improved.