Synthesis of 21-nitrogen substituted pregna-5,17(20)-dienes from pregnenolone

Antiproliferative, proapoptotic, and tumor-suppressing effects of the novel anticancer agent alsevirone in prostate cancer cells and xenografts

The aim of this study was to explore the mechanisms of action of alsevirone in prostate cancer (PC) in vitro and in vivo: CYP17A1 inhibition, cytotoxic, apoptotic, and antitumor effects in comparison with abiraterone. The CYP17A1-inhibitory activity was investigated in rat testicular microsomes using high-performance liquid chromatography. Testosterone levels were evaluated using enzyme-linked immunoassay. IC₅₀ values were calculated for PC3, DU-145, LNCaP, and 22Rv1 cells using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test. The antitumor effect in vivo was studied in DU-145 and 22Rv1 subcutaneous xenografts in Balb/c nude mice. Alsevirone reduced the CYP17A1-inhibitory activity by 98% ± 0.2%. A statistically significant reduction in the testosterone concentration in murine blood was recorded after the 7th administration of 300 mg/kg alsevirone at 0.31 ± 0.03 ng/ml (p < .001) versus 0.98 ± 0.22 ng/ml (p = .392) after abiraterone administration and 1.52 ± 0.49 ng/ml in control animals. Alsevirone was more cytotoxic than abiraterone in DU-145, LNCaP, and 22Rv1 cells, with IC₅₀ values of 23.80 ± 1.18 versus 151.43 ± 23.70 μM, 22.87 ± 0.54 versus 28.80 ± 1.61 μM, and 35.86 ± 5.63 versus 109.87 ± 35.15 μM, respectively. Alsevirone and abiraterone significantly increased annexin V-positive, caspase 3/7-positive, and activated Bcl-2-positive cells. In 22Rv1 xenografts, alsevirone 300 mg/kg × 10/24 h per os inhibited tumor growth: on Day 9 of treatment, tumor growth inhibition = 59% (p = .022). Thus, alsevirone demonstrated significant antitumor activity associated with CYP17A1 inhibition, apoptosis in PC cells, and testosterone reduction.

Oxazolinyl derivatives of [17(20)E]-21-norpregnene differing in the structure of A and B rings. Facile synthesis and inhibition of CYP17A1 catalytic activity

Five 4,5-dihydro-1,3-oxazole derivatives of [17(20)E]-21-norpregnene, comprising 3β-hydroxy-5-ene (1), 3,6-dioxo-4-ene (2), 3-oxo-4-ene (3), 3α,5α-cyclo-6-oxo (4), 3β-hydroxy-6-oxo (5) fragments were synthesized. Synthesis was conducted with improved procedure, based on reaction of suitably protected [17(20)E]-pregnen-21-oic acids with ethanolamine in presence of triphenyl phosphine, carbon tetrachloride, and triethyl amine. Potency of the compounds 1-5 to inhibit 17α-hydroxylase/17,20-lyase (CYP17A1) activity was studied by highly sensitive electrochemical method, using the enzyme immobilization technique. Compounds 1 and 3 were found to be potent CYP17A1 inhibitors, compounds 2 and 5 were not active, compound 4 strongly and irreversibly suppressed the enzyme activity. Molecular docking of compounds 1-5 in the active site of CYP17A1 showed that positions of all compounds in the enzyme active site were similar.

[Interaction of novel oxazoline derivatives of 17(20)e-pregna-5,17(20)-diene with cytochrome P450 17A1]

In order to find novel inhibitors of 17a-hydroxylase-17,20-lyase (cytochrome P450 17A1, CYP17A1), a key enzyme of biosynthesis of androgens, molecular docking of six new oxazoline-containing derivatives 17(20)E-pregna-5,17(20)-diene has been carried out to the active site of the crystal structure of CYP17A1 (pdb 3ruk). Results of this study indicate that: 1) complex formation of docked compounds with CYP17A1 causes their isomerization in energetically less favorable 17(20)Z-isomer; 2) the localization of the steroid moiety of all compounds in the active site is basically the same; 3) the structure of the oxazoline moiety significantly influences its position relative to heme as well as the energy of complex formation; 4) coordination of the nitrogen atom of the oxazoline moiety and the heme iron is only possible in the 17(20)Z-conformation with anti oriented double bonds 17(20), and C=N; 5) the presence of two substituents at C4' of the oxazoline moiety significantly impairs ligand binding; 6) oxazoline--and benzoxazole-containing derivatives 17(20)E-pregna-5,17(20)-diene can effectively inhibit the catalytic activity CYP17A1 and may be of interest as a basis for the development of new drugs for the treatment of androgen-dependent cancer.

Novel oxazolinyl derivatives of pregna-5,17(20)-diene as 17α-hydroxylase/17,20-lyase (CYP17A1) inhibitors

New oxazolinyl derivatives of [17(20)E]-pregna-5,17(20)-diene: 2'-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4',5'-dihydro-1',3'-oxazole 1 and 2'-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4',4'-dimethyl-4',5'-dihydro-1',3'-oxazole 2 were evaluated as potential CYP17A1 inhibitors in comparison with 17-(pyridin-3-yl)androsta-5,16-dien-3β-ol 3 (abiraterone). Differential absorption spectra of human recombinant CYP17A1 in the presence of compound 1 (λmax=422 nm, λmin=386 nm) and compound 2 (λmax=416 nm) indicated significant differences in enzyme/inhibitors complexes. CYP17A1 activity was measured using electrochemical methods. Inhibitory activity of compound 1 was comparable with abiraterone 3 (IC50=0.9±0.1 μM, and IC50=1.3±0.1 μM, for compounds 1 and 3, respectively), while compound 2 was found to be weaker inhibitor (IC50=13±1 μM). Docking of aforementioned compounds to CYP17A1 revealed that steroid fragments of compound 1 and abiraterone 3 occupied close positions; oxazoline cycle of compound 1 was coordinated with heme iron similarly to pyridine cycle of abiraterone 3. Configuration of substituents at 17(20) double bond in preferred docked position corresponded to Z-isomers of compounds 1 and 2. Presence of 4'-substituents in oxazoline ring of compound 2 prevents coordination of oxazoline nitrogen with heme iron and worsens its docking score in comparison with compound 1. These data indicate that oxazolinyl derivative of [17(20)E]-pregna-5,17(20)-diene 1 (rather than 4',4'-dimethyl derivative 2) may be considered as potential CYP17A1 inhibitor and template for development of new compounds affecting growth and proliferation of prostate cancer cells.

[Molecular modeling of interaction of 17(20)Z- and 17(20)E-pregna-5,17(20)-dien-21-oyl amides with the nuclear receptor LXRbeta]

Aiming the search of novel regulators of lipid metabolism and their potential targets, in this study we performed molecular modeling of eight isomeric 17(20)Z- and 17(20)E-pregna-5,17(20)-dien-21-oyl amides differing in structure of the amide moiety. Analysis of the low energy conformers revealed that all 17(20)E-isomers had three main energy minima (corresponding to values of the dihedral angle theta20,21 (C17 = C20-C21 = 0) to approximately 0 degrees, to approximately 120 degrees and to approximately 240 degrees), the most occupied minimum was found to correspond to theta20,21 to approximately 0 degrees; while 17(20)Z-isomers had either one or two pools of low energy conformations. Molecular docking of these compounds to the ligand-binding site of the nuclear receptor LXRbeta (a potential target) indicates high probability of binding for E-isomers and the absence of that for Z-isomers. Results of the molecular modeling were confirmed by an experiment in which stimulation of triglyceride biosynthesis in Hep G2 cells in the presence of 17(20)E-3beta-hydroxypregna-5,17(20)-dien-21-oyl (hydroxyethyl)amide was demonstrated.

Synthesis and molecular modeling of (4'R)- and (4'S)- 4'-substituted 2'-{[(E)-androst-5-en-17-ylidene]-methyl}oxazolines

Synthesis of four novel (4'R)- and (4'S)- 2'-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]-methyl} oxazolines, comprising 4'-hydroxymethyl (1 and 2) and 4'-methoxycarbonyl (3 and 4) substituents is presented. Reaction of 17α-bromo-21-iodo-3β-acetoxypregn-5-en-20-one with either (L)-serine methyl ester, or (D)-serine methyl ester resulted in methyl N-[3β-acetoxy-21-oxopregna-5,17(20)-dien-21-yl]-(L)-serinate and methyl N-[3β-acetoxy-21-oxopregna-5,17(20)-dien-21-yl]-(D)-serinate (as mixtures of related [17(20)E]- and [17(20)Z]-isomers). Cyclization of obtained amides led to methyl 2'-{[(E)-3β-acetoxyandrost-5-en-17-ylidene]methyl}-(4'S)-4',5'-dihydro-1',3'-oxazole-4'-carboxylate and methyl 2'-{[(E)-3β-acetoxyandrost-5-en-17-ylidene]methyl}-(4'R)-4',5'-dihydro-1',3'-oxazole-4'-carboxylate which were transformed to titled compounds 1-4. The molecular docking of compounds 1-4 to ligand binding site of nuclear receptor LXRβ revealed significant differences due to stereochemical configuration of 4' atom and structure of 4'-substituent.

Pregna-5,17(20)-dien-21-oyl amides affecting sterol and triglyceride biosynthesis in Hep G2 cells

Synthesis of series [17(20)Z]- and [17(20)E]-pregna-5,17(20)-dien-21-oyl amides, containing polar substituents in amide moiety, based on rearrangement of 17α-bromo-21-iodo-3β-acetoxypregn-5-en-20-one caused by amines, is presented. The titled compounds were evaluated for their potency to regulate sterol and triglyceride biosynthesis in human hepatoma Hep G2 cells in comparison with 25-hydroxycholesterol. Three [17(20)E]-pregna-5,17(20)-dien-21-oyl amides at a concentrations of 5 μM inhibited sterol biosynthesis and stimulated triglyceride biosynthesis; their regulatory potency was dependent on the structure of amide moiety; the isomeric [17(20)Z]-pregna-5,17(20)-dien-21-oyl amides were inactive.