Synthesis and biochemical evaluation of (carbamoylalkenyl)phenyloxy carboxylic acid derivatives as non-steroidal 5 alpha-reductase inhibitors

Evaluation of Cell Permeation of a Potent 5α-Reductase Inhibitor Using MALDI-TOF MS

N-(Dicyclohexyl)acetyl-piperidine-4-benzylidene-4-carboxylic acid (1), although a very potent in vitro 5alpha-steroid reductase (5alphaR) type 2 inhibitor, showed only marginal in vivo activity in rats. Since this could be due to hindered cellular uptake of the carboxylic acid, acid (1) and its corresponding methyl ester (1a) were compared with respect to their permeation properties. In the parallel artificial membrane permeation assay (PAMPA), 1a showed a higher %flux of 55 versus 6 for 1. Considering the high potency of 1 and better permeation of 1a, the use of 1a as a prodrug for 1 was explored using the human prostate carcinoma cell line DU145. Esterase activity, a prerequisite for this prodrug concept was detected employing 4-nitrophenyl acetate (4-NPA) as a substrate. After incubation of DU145 cells with 1 and 1a, respectively, permeated 1a and its hydrolysis to 1 were unequivocally observed by MALDI-TOF MS analyses, whereas 1 could not be detected inside the cells above the detection limit. Regarding biological activity, 1a showed a stronger inhibition of 5alphaR in intact DU145 cells than 1 (IC50 values, 4 microM and > 10 microM for 1a and 1, respectively). These results suggest that the in vivo activity of 1 might be increased by the use of its methyl ester prodrug 1a.

Biocatalytic synthesis of 4-pregnen-20,21-diol-3-one, a selective inhibitor of human 5alpha-reductase type II

Biocatalysis, the conversion of substrates into valuable products by the use of enzymes, has some striking advantages in comparison to standard organic chemistry for drug synthesis. By biocatalysis, substrates that contain several identical reactive groups at different positions can be converted with high regio-selectivity and enantio-selectivity. In this study, an E. coli isolate (E132) was identified which was able to convert the steroid desoxycorticosterone into the product 4-pregnen-20,21-diol-3-one in real terms. The product was purified from the cell culture supernatant by HPLC and its structure was demonstrated by mass spectrometry and NMR spectroscopy. It was tested on inhibition of human 5alpha-reductases type I and type II. At a concentration of 10 microM, inhibition was 49.0% for type I and 81.8% for type II, whereas there was no inhibition of human aromatase (CYP19) at 20 microM and human 17alpha-hydroxylase-C17,20-lyase (CYP17) at 2.5 microM detectable. The IC50 value of 4-pregnen-20,21-diol-3-one for human 5alpha-reductase type II was determined to be 1.56 microM.

5-Phenyl substituted 1-methyl-2-pyridones and 4'-substituted biphenyl-4-carboxylic acids. synthesis and evaluation as inhibitors of steroid-5alpha-reductase type 1 and 2

The synthesis of a series of 5-phenyl substituted 1-methyl-2-pyridones (I) and 4'-substituted biphenyl-4-carboxylic acids (II) as novel A-C ring steroidomimetic inhibitors of 5alpha-reductase (5alphaR) is described. Compounds 1-4 (I) were synthesized by palladium catalyzed cross coupling (Ishikura) reaction between diethyl(3-pyridyl)borane and aryl halides (1b-4b) followed by alpha-oxidation with sodium ferrocyanate of the 1-methyl-pyridinium salt. Inhibitors II (5-18) were obtained either by two successive Friedel-Crafts acylations from biphenyl (5a-10a) followed by saponification to yield the corresponding carboxylic acids (5-10) or by Suzuki cross coupling reaction to give the 4'-substituted biphenyl-4-carbaldehydes 11a-18a. The latter compounds were subjected to a Lindgren oxidation to yield compounds 11-18. The compounds were tested for inhibitory activity toward human and rat 5alphaR1 and 2. The test compounds inhibited 5alphaR, showing a broad range of inhibitory potencies. The best compound in series I was the N-(dicyclohexyl)-4-(1,2-dihydro-1-methyl-2-oxopyrid-5-yl)benzamide 4 exhibiting an IC(50) value for the human type 2 enzyme of 10 microM. In series II, the most active compound toward human type 2 isozyme was the 4'-(dicyclohexyl)acetyl-4-biphenyl carboxylic acid (10; IC(50)=220nM). Both series showed only marginal activity toward the human type 1 isozyme. In conclusion, the biphenyl carboxylic acids (II) are more appropriate for 5alphaR inhibition than the 5-phenyl-1-methyl-2-pyridones (I). Especially the 4'-carbonyl compounds 5-10 represent new lead structures for the development of novel human type 2 inhibitors.

Stable expression of human 5alpha-reductase type II in COS1 cells due to chromosomal gene integration: a novel tool for inhibitor identification

Inhibitors of human 5alpha-reductase type II are promising drug candidates for the treatment of benign prostatic hyperplasia which is associated with high prostatic DHT levels. In this study we describe the evaluation of potential inhibitors in a new cell assay. First a plasmid (pRcCMV-5alphaII) for the expression of human 5alpha-reductase type II was constructed by the use of the vector pRcCMV and transfected into the African green monkey fibroblast-like cell line COS1. By selection with G418 sulfate, ten COS1 single cell clones were obtained of which three stably exhibited high 5alpha-reductase activity. One single cell clone (COS1-5alphaIIST) was selected for further investigations. By Southern blot analysis, fluorescence in situ hybridization (FISH) and comparative PCR experiments it turned out that the expression plasmid pRcCMV-5alphaII has been integrated into the chromosome, resulting in a long-term stable expression of the foreign 5alpha-reductase gene. The newly established cell line was used for testing novel compounds on their inhibitory effect on human 5alpha-reductase type II. Using this whole cell assay, inhibitors with IC(50) values in the nanomolar range could be identified.

Stable expression of the human 5alpha-reductase isoenzymes type I and type II in HEK293 cells to identify dual and selective inhibitors

A eucaryotic cell assay was established to identify novel, dual and selective inhibitors of human 5alpha-reductase. For this purpose the cDNAs encoding 5alpha-reductase type I and type II were inserted into a pRcCMV vector and expressed in human embryonic kidney (HEK293) cells. Single cell clones with substantially high enzymatic activity were selected and established as permanent cell lines. KM values were determined for both isozymes. The inhibitory potency of several steroidal and non-steroidal compounds synthesized in our group, as well as finasteride and 4MA as controls, were tested by measuring the conversion of [3H]androstenedione. Reaction products were quantified by a HPLC reversed phase technique. Using the new cell assays, selective as well as novel dual 5alpha-reductase inhibitors with IC50 values between 1.0 and 2.5 microM were identified.

Synthesis and evaluation of novel steroidal oxime inhibitors of P450 17 (17 alpha-hydroxylase/C17-20-lyase) and 5 alpha-reductase types 1 and 2

17 alpha-Hydroxylase/C17-20-lyase (P450 17, CYP 17) and 5 alpha-reductase are the key enzymes in androgen biosynthesis and targets for the treatment of prostate cancer and benign prostatic hyperplasia. In the search of inhibitors for both enzymes, 23 pregnenolone- or progesterone-based steroids were synthesized bearing an oxime group connected directly or via a spacer to the steroidal D-ring. Tested for inhibition of human and rat P450 17, some pregnenolone (9, 11, 14) and a series of progesterone compounds (17-20) turned out to be highly active inhibitors of the human enzyme. The most active compound was Z-21-hydroxyiminopregna-5, 17(20)-dien-3 beta-ol (9) showing K(i) values of 44 and 3.4 nM for the human and rat enzymes, respectively, and a type II UV-difference spectrum indicating a coordinate bond between the oxime group and the heme iron. In contrast to the pregnenolones which showed no inhibition of 5 alpha-reductase isozymes 1 and 2, the progesterones 16, 17, 20, 21, and 23 showed marked inhibition, especially toward the type 2 enzyme. Compounds 17 and 20 were identified as potent dual inhibitors of both P450 17 and 5 alpha-reductase. Tested for selectivity, the most potent P450 17 inhibitors 9, 10, and 14 showed no or only marginal inhibition of P450 arom, P450 scc, and P450 TxA(2). Selected compounds were tested for inhibition of the target enzymes using whole-cell assays. Compounds 9-11 strongly inhibited P450 17 being coexpressed with NADPH-P450 reductase in E. coli cells, and 16, 20, and 23 markedly inhibited 5 alpha-reductase expressed in HEK 293 cells. Tested for in vivo activity, 9 (0.019 mmol/kg) decreased the plasma testosterone concentration in rats after 2 and 6 h by 57% and 44%.

New nonsteroidal steroid 5 alpha-reductase inhibitors. Syntheses and structure-activity studies on carboxamide phenylalkyl-substituted pyridones and piperidones

In the search for nonsteroidal inhibitors of 5 alpha-reductase for the treatment of benign prostatic hyperplasia (BPH), we synthesized diisopropyl (1a-8a) and tert-butyl (1b-8b) benzamides, as well as ethyl benzoates (1c, 3c), which were substituted in 4 position via variable alkyl spacer (n = 0: 1-4, n = 1: 5, 7 and n = 3: 6, 8) with a 1-methyl-2-pyridone (1, 2, 5, 6) or a 1-methyl-2-piperidone (3, 4, 7, 8) moiety mimicking steroidal ring A. The directly connected benzamides (1a-4a, 1b-4b) and benzoates (1c, 3c) were obtained by palladium-catalysed coupling reaction of diethyl(3-pyridyl)-borane with 4-bromobenzoic acid derivatives, followed by alpha-oxidation of the 1-methyl-pyridinium salt and subsequent separation of the regioisomers. Catalytic hydrogenation of the pyridones (1, 2) led to the piperidones (3, 4). The preparation of the benzamides with a methylene (5, 7) and a propylene spacer (6, 8), respectively, started with the reduction of the keto group of 5-benzoyl-1,2-dihydro-1-methyl-2(1H)-pyridone and catalytic hydrogenation of the alkene obtained by Wittig reaction of 5-formyl-1,2-dihydro-1-methyl-2(1H)-pyridone with (2-phenylethyl)triphenylphosphonium bromide, respectively. The phenyl ring was functionalized by Friedel-Crafts reaction, haloform cleavage to give the acid, formation of the acid chloride, and subsequent treatment with the appropriate amines. Again, catalytic hydrogenation of the pyridones (5, 6) led to the piperidones (7, 8). The 5 alpha-reductase inhibitory properties were determined using rat ventral prostate, as well as human BPH tissue as enzyme source, 1 beta-2 beta-[3H]testosterone as substrate and a HPLC procedure for the separation of dihydrotestosterone (DHT). Tested at a concentration of 100 microM, the inhibition values of 1-8 ranged from 0-79%. Significant differences were observed between rat and human enzyme. The most active compound was ethyl 4-(1-methyl-2-oxopiperid-5-yl)benzoate 3c (68%) for the human enzyme and N,N-bis(1-methylethyl)-4-[3-(1,2-dihydro-1-methyl-2-oxopyrid-5-yl) propyl] benzamide 6a (79%) for the rat enzyme.

Synthesis and 5 alpha-reductase inhibitory activities of benzofuran derivatives with a carbamoyl group

A series of 2-phenylbenzofuran derivatives with a diphenylmethylcarbamoyl group at the 5 or 6 position of the benzofuran ring were synthesized and evaluated for rat and human testosterone 5 alpha-reductase inhibitory activities in vitro. They had inhibitory activities against both enzymes and the 6-carbamoyl derivatives tended to be more potent than the 5-carbamoyl compounds.