Photo-conversion of two epimers (20R and 20S) of pregna-5,7-diene-3beta, 17alpha, 20-triol and their bioactivity in melanoma cells.

Pregna-5,7-dienes and their hydroxylated derivatives can be formed in vivo when there is a deficiency in 7-dehydrocholesterol (7-DHC) Delta-reductase function, e.g., Smith-Lemli-Opitz syndrome (SLOS). Ultraviolet B (UVB) radiation induces photoconversion of 7-DHC to vitamin D3, lumisterol3 and tachysterol3. Two epimers (20R and 20S) of pregna-5,7-diene-3beta,17alpha,20-triol (4R and 4S, respectively) were synthesized and their UVB photo-conversion products identified as corresponding 9,10-secosteroids with vitamin D-like and tachysterol-like structures, and 5,7-dienes with inverted configuration at C-9 and C-10 (lumisterol-like). The number and character of the products and the dynamics of the process were dependent on the UVB dose. At high UVB doses, the formation of multiple oxidized derivatives of the primary products, and the formation of 5,7,9(11)-triene, were observed. The production of vitamin D-like, tachysterol-like and lumisterol-like derivatives was also observed in human skin treated with 4R and 4S, and subjected to UV irradiation, as shown by RP-HPLC. Newly synthesized compounds inhibited melanoma growth in dose dependent manner, and some of them showed equal or higher potency than 1,25(OH)2D3. In summary, we have characterized for the first time the products of UV induced conversion of pregna-5,7-diene-3beta,17alpha,20-triols and documented that the newly synthesized compounds have antiproliferative properties against melanoma cells.

Metabolism of steroidal anti-inflammatory antedrugs in vitro: methyl 3,20-dioxo-11beta,17alpha,21-trihydroxy-1,4-pregnadiene-16alpha-carboxylate; its 9alpha-fluorinated, and their 21-O-acyl derivatives.

The in vitro hydrolysis rates of steroidal anti-inflammatory antedrugs, methyl 3,20-dioxo-11beta,17alpha,21-trihydroxy-1,4-pregnadiene-16alpha-carboxylate (P16CM), its 9alpha-fluorinated analogue (FP16CM), and their 21-O-acyl derivatives (P16CM-acetyl, FP16CM-acetyl, FP16CM-propionyl, FP16CM-valeryl, and FP16CM-pivalyl) were investigated in rat plasma. These steroids were synthesized based on the antedrug concept. P16CM and FP16CM were hydrolyzed to inactive steroid-16-carboxylate, with half-lives of 90.0 and 99.4 min, respectively. The metabolite was positively identified by NMR and elemental analysis. To determine the relative hydrolysis rate of the C21-O-acyl versus the C16-methoxycarbonyl group, P16CM- and FP16CM-21-O-acyl derivatives were also studied. The hydrolysis rates of all 21-O-acyl groups were much faster than that of the 16-methoxycarbonyl group. The half-lives of P16CM-acetyl, FP16CM-acetyl, FP16CM-valeryl, and FP16CM-propionyl were 6.3, 16.8, 23.2, and 18.4 min, respectively. On the other hand, FP16CM-pivalyl showed relatively slow hydrolysis rate (T(1/2): 59.7 min). These results clearly indicate that 21-O-acyl group is metabolized first to active compound, P16CM or FP16CM, followed by the hydrolysis of 16-methoxycarbonyl to corresponding inactive steroid-16-carboxylates as the major metabolites. Collectively, the results of the present study support the previous reports where decrease in adverse systemic effects without losing local anti-inflammatory activity was attributed to the hydrolysis of the active agents to inactive acidic metabolites in the systemic circulation. This study thus shows that the incorporation of a 16-methoxycarbonyl coupled with a 21-O-acyl moiety may be a fundamentally sound synthetic strategy in the development of locally active anti-inflammatory steroids having reduced systemic adverse activities.

Effect of chirality at C-20 of methyl 11beta,17alpha,20-trihydroxy-3-oxo-1,4-pregnadien-21-oate derivatives on antiinflammatory activity.

In an effort to determine the C-20 chirality effect on the antiinflammatory activity of 17beta-glycolate esters, methyl 11beta,17alpha,20-trihydroxy-3-oxo-1,4-pregnadien-21-oate and its 9alpha-fluoro analog, their acetonide and their carbonate derivatives were synthesized and evaluated. The agents were tested for their binding potency to the macrophage glucocorticoid receptor, and their effect on LPS-induced nitric oxide generation in RAW 264.7 cells. The acetonide derivatives showed the highest binding affinity while the triols and carbonates bound rather poorly to the receptors. With the exception of the triols, the alpha-isomer in each pair of the agents exhibited higher binding affinity to the receptor than its corresponding beta-isomer, clearly indicating that C-20 chirality has a significant effect on antiinflammatory activity. In addition, the alpha-isomers of the acetonides showed substantially higher binding affinity than the parent compound, prednisolone. In contrast to the high binding activity exhibited by some of the acetonides, all of the agents showed weak inhibitory effect on NO generation. Metabolic inactivation during assessment of NO inhibition may play a role in the divergence noted between receptor affinity and the measured biologic activity resulting from the binding.

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.