FK143, a novel nonsteroidal inhibitor of steroid 5 alpha-reductase: (1) In vitro effects on human and animal prostatic enzymes

Development of a Liquid Chromatography/Mass Spectrometry-Based Inhibition Assay for the Screening of Steroid 5-α Reductase in Human and Fish Cell Lines

Steroid 5-α reductase (5AR) is responsible for the reduction of steroids to 5-α reduced metabolites, such as the reduction of testosterone to 5-α dihydrotestosterone (DHT). A new adverse outcome pathway (AOP) for 5AR inhibition to reduce female reproduction in fish (AOP 289) is under development to clarify the antiestrogenic effects of 5AR inhibitors in female fish. A sensitive method for the DHT analysis using chemical derivatization and liquid chromatography–tandem mass spectrometry was developed. A cell-based 5AR inhibition assay that utilizes human cell lines, a transient overexpression system, and fish cell lines was developed. The measured IC₅₀ values of two well-known 5AR inhibitors, finasteride and dutasteride, were comparable in the different systems. However, the IC₅₀ of dutasteride in the fish cell lines was lower than that in the human cell lines. Finasteride showed a higher IC₅₀ against the RTG-2 cell line. These results demonstrated that 5ARs inhibition could differ in terms of structural characteristics among species. The assay has high sensitivity and reproducibility and is suitable for the application in 5AR inhibition screening for various endocrine disruption chemicals (EDCs). Future studies will continue to evaluate the quantitative inhibition of 5AR by EDCs to compare the endocrine-disrupting pathway in different species.

The one-pot synthesis of butyl-1H-indol-3-alkylcarboxylic acid derivatives in ionic liquid as potent dual-acting agent for management of BPH

Based on the SAR of both α₁-AR antagonists and 5α-reductase (5AR) inhibitors, the dual-acting agent 4-(1-(4-(4-(2-methoxyphenyl)piperazin-1-yl)butyl)-1H-indol-3-yl)butanoic acid 4aaa was designed against BPH and synthesized by two steps of N-alkylation. One-pot protocol towards 4aaa was newly developed. With IL [C₆min]Br as solvent, the yield of 4aaa was increased to 75.1% from 16.0% and the reaction time was shortened in 1.5 h from 48 h. 25 derivatives structurally based on arylpiperazine and indolyl butyric acid with alkyl linker were prepared. The protocol was futher extended to get another 14 derivatives wherein O-alkylation was involved, and applied to the synthesis of biologically efficient molecules DPQ and Aripiprazole. Expectedly, compound 4aaa exhibited dual inhibition of α₁-AR and 5α-reductase, and exhibited no obvious cytotoxicity against human cells. The pharmacokinetic properties of 4aaa was also determined.

Repurposing steroidogenesis inhibitors for the therapy of neuropsychiatric disorders: Promises and caveats

Steroids exert a profound influence on behavioral reactivity, by modulating the functions of most neurotransmitters and shaping the impact of stress and sex-related variables on neural processes. This background - as well as the observation that most neuroactive steroids (including sex hormones, glucocorticoids and neurosteroids) are synthetized and metabolized by overlapping enzymatic machineries - points to steroidogenic pathways as a powerful source of targets for neuropsychiatric disorders. Inhibitors of steroidogenic enzymes have been developed and approved for a broad range of genitourinary and endocrine dysfunctions, opening to new opportunities to repurpose these drugs for the treatment of mental problems. In line with this idea, preliminary clinical and preclinical results from our group have shown that inhibitors of key steroidogenic enzymes, such as 5α-reductase and 17,20 desmolase-lyase, may have therapeutic efficacy in specific behavioral disorders associated with dopaminergic hyperfunction. While the lack of specificity of these effects raises potential concerns about endocrine adverse events, these initial findings suggest that steroidogenesis modulators with greater brain specificity may hold significant potential for the development of alternative therapies for psychiatric problems. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.

Promotion Effect of Apo-9'-fucoxanthinone from Sargassum muticum on Hair Growth via the Activation of Wnt/β-Catenin and VEGF-R2

This study was conducted to evaluate the effects of Sargassum muticum extract and apo-9'-fucoxanthinone, a principal component of S. muticum, on hair growth. When rat vibrissa follicles were treated with S. muticum extract for 21 d, the hair-fiber lengths for the vibrissa follicles increased significantly. Treatment with the S. muticum extract and the EtOAc fraction of the S. muticum extract markedly increased the proliferation of dermal papilla cells (DPCs) and decreased the 5α-reductase activity. In addition, the EtOAc fraction of the S. muticum extract significantly promoted anagen initiation in C57BL/6 mice. Especially, apo-9'-fucoxanthinone, an active constituent from the S. muticum extract, caused an increase in DPC proliferation and a decrease in 5α-reductase activity. To elucidate the molecular mechanisms of apo-9'-fucoxanthinone on the proliferation of DPCs, we examined the level of various signaling proteins. Apo-9'-fucoxanthinone increased the level of vascular endothelial growth factor receptor-2 (VEGF-R2), Wnt/β-catenin signaling proteins such as phospho(ser9)-glycogen synthase kinase-3β (GSK-3β) and phospho(ser552)-β-catenin, whereas apo-9'-fucoxanthinone did not affect the transforming growth factor-β (TGF-β) signaling proteins such as Smad2/3. These results suggest that apo-9'-fucoxanthinone from S. muticum could have the potential for hair growth with DPC proliferation via the activation of Wnt/β-catenin signaling and the VEGF-R2 pathway.

Steroidal pyrazolines and pyrazoles as potential 5α-reductase inhibitors: synthesis and biological evaluation

Taking pregnenolone as the starting material, two series of pyrazolinyl and pyrazolyl pregnenolones were synthesized through different routes. The synthesis of the analogs of both series is multistep and proceeds in good overall yields. While the key step in the synthesis of pyrazolinyl pregnenolones is the heterocyclization of benzylidine derivatives (3) in presence of hydrazine hydrate, it is the condensation of 3β-hydroxy-21-hydroxymethylidenepregn-5-en-3β-ol-20-one (5) with phenylhydrazine in the synthesis of pyrazolyl derivatives. Compounds of both the series were tested for their 5α-reductase inhibitory activities. Amongst all the compounds screened for their 5α-reductase inhibitory activities, compound 4b, 4c and 6b were found to be the most active.

Potential targets in the discovery of new hair growth promoters for androgenic alopecia

INTRODUCTION

Androgenic alopecia (AGA) is the major type of scalp hair loss affecting 60 - 70% of the population worldwide. It is caused by two potent androgens, namely testosterone (T) and 5α-dihydrotestosterone (5α-DHT). Till date, only two FDA-approved synthetic drugs, minoxidil and finasteride, are used to cure AGA with only 35 and 48% success, respectively; therefore, a search for new drug based on the mechanism of androgens action is still needed.

AREAS COVERED

Relevant literature was reviewed to identify current therapeutic targets and treatments for AGA. The potential targets are classified into three categories: i) 5α-reductase; ii) androgen receptor and iii) growth-factor-producing genes related to hair growth.

EXPERT OPINION

Relevant assay systems using the right targets are required in order to obtain specific and effective drugs for AGA treatment. It is unlikely that single targeted agents will be sufficient for treating AGA, and therefore, it would be a challenge to obtain compounds with multiple activities.

Effect of carbamates on mRNA encoding lipid enzymes in hamster flank organs

Flank organs are an androgen-dependent pilosebaceous complex present in male and female hamsters. These organs have been used for the evaluation of antiandrogenic drugs, which could be used for the treatment of androgen-dependent afflictions. This study demonstrated the role of four different steroidal carbamates 7-10 in the expression of mRNAs coding for different enzymes involved in the lipid metabolism in flank organs. To determine the biological effects of compounds 7-10 on the expression of mRNA coding for lipid enzymes, steroids 7-10, testosterone (T), progesterone (P), and/or 7-10 were applied on the flank organs. Later, the mRNA expression for the enzymes was determined by polymerase chain reaction. The binding of 8 and 9 to the progesterone receptor (PR) as well as their effects on the activity of 5α-reductase were also evaluated. Treatments with T, P, and 7-10 increased the mRNA expression for glycerol 3-phosphate acyl transferase (GPAT), β-hydroxy-β-methylglutaryl-CoA synthase (HMG-CoA-S), β-hydroxy-β-methylglutaryl-CoA reductase (HMG-CoA-R), phosphatidylinositol synthase (PI-S), and squalene-synthase (SQ-S). However, the combined treatments with P + 7-10 decreased the expression of GPAT, HMG-CoA-S, and HMG-CoA-R. Expression of mRNA for all enzymes was variable under treatment with T + 7-10. Data showed that these carbamates did not bind to the PR, but inhibited the activity of 5α-reductase. Carbamates 7-10 changed the mRNA expression model induced by T and P in flank organs.

Hair-Loss Preventing Effect of Grateloupia elliptica

This study was conducted to evaluate the effect of Grateloupia elliptica, a seaweed native to Jeju Island, Korea, on the prevention of hair loss. When immortalized rat vibrissa dermal papilla cells were treated with extract of G. elliptica, the proliferation of dermal papilla cells significantly increased. In addition, the G. elliptica extract significantly inhibited the activity of 5α-reductase, which converts testosterone to dihydrotestosterone (DHT), a main cause of androgenetic alopecia. On the other hand, the G. elliptica extract promoted PGE2 production in HaCaT cells in a dose-dependent manner. The G. elliptica extract exhibited particularly high inhibitory effect on LPS-stimulated IL-12, IL-6, and TNF-α production in lipopolysaccharide (LPS)-stimulated bone marrow-derived dendritic cells. The G. elliptica extract also showed inhibitory activity against Pityrosporum ovale, a main cause of dandruff. These results suggest that G. elliptica extract has the potential to treat alopecia via the proliferation of dermal papilla, 5α-reductase inhibition, increase of PGE2 production, decrease of LPS-stimulated pro-inflammatory cytokines and inhibitory activity against Pityrosporum ovale.

Spectrophotometric method for the assay of steroid 5α-reductase activity of rat liver and prostate microsomes

A simple spectrophotometric method for the assay of steroid 5α-reductase (5α-SR) was developed in which 5α-dihydrotestosterone (5α-DHT) and 5α-androstane-3α,17β-diol (5α-diol), metabolites formed in the NADPH-dependent reduction of testosterone with enzyme sources of 5α-SR, were measured by enzymatic cycling using 3α-hydroxysteroid dehydrogenase in the presence of excess thionicotinamide-adenine dinucleotide (thio-NAD) and NADH. It was found that 5α-SR activity was proportional to the accumulated thio-NADH having an absorption maximum at 400 nm. Because of the high cycling rate (> 600 cycle per min) and no interference from testosterone, enzymatic cycling can determine the sum of 5α-DHT and 5α-diol at the picomole level without separation from excess testosterone. The present method was readily applicable to the assay of 5α-SR activity of rat liver and prostate microsomes as well as to the assay of inhibitory activity of finasteride, a synthetic inhibitor of 5α-SR.

The promoting effect of Ishige sinicola on hair growth

This study was conducted to evaluate the promoting effect of Ishige sinicola, an alga native to Jeju Island, Korea, on hair growth. When vibrissa follicles were cultured in the presence of I. sinicola extract for 21 days, I. sinicola extract increased hair-fiber length. After topical application of I. sinicola extract onto the back of C57BL/6 mice, anagen progression of the hair shaft was induced. The I. sinicola extract significantly inhibited the activity of 5α-reductase. Treatment of immortalized vibrissa dermal papilla cells (DPCs) with I. sinicola extract resulted in increase of cell proliferation, which was accompanied by the increase of phospho-GSK3β level, β-catenin, Cyclin E and CDK2, whereas p27kip1 was down-regulated. In particular, octaphlorethol A, an isolated component from the I. sinicola extract, inhibited the activity of 5α-reductase and increased the proliferation of DPCs. These results suggest that I. sinicola extract and octaphlorethol A, a principal of I. sinicola, have the potential to treat alopecia via the proliferation of DPCs followed by the activation of β-catenin pathway, and the 5α-reductase inhibition.

In vivo and in vitro effect of androstene derivatives as 5α-reductase type 1 enzyme inhibitors

The aim of these studies was to synthesize twelve ester derivatives of dehydroepiandrosterone with therapeutic potential. The effect of 1-12 was demonstrated in the flank organs of gonadectomized hamsters treated with testosterone and the synthesized steroids. In vitro studies were carried out determining the IC50 values for the inhibition of the activity of 5α-reductase type 1 and 2, which are present in rat liver and human prostate respectively. The binding of 1-12 to the androgen receptors (AR) was determined using rat's prostate cytosol. Steroids 1-12 containing different substituents in the phenyl group of the ester moiety in C-3 reduced the flank organs and inhibited the activity of 5α-R type 1; however only steroids 1 and 2 inhibited 5α-R type 2. 1-12 did not bind to the AR. The modification of one atom of the substituents in the phenyl group of the ester moiety in C-3 changed their biological potency (IC50).

Effect of Dieckol, a component of Ecklonia cava, on the promotion of hair growth

This study was conducted to evaluate the effect of Ecklonia cava, a marine alga native to Jeju Island in Korea, on the promotion of hair growth. When vibrissa follicles were cultured in the presence of E. cava enzymatic extract (which contains more than 35% of dieckol) for 21 days, E. cava enzymatic extract increased hair-fiber length. In addition, after topical application of the 0.5% E. cava enzymatic extract onto the back of C57BL/6 mice, anagen progression of the hair-shaft was induced. The treatment with E. cava enzymatic extract resulted in the proliferation of immortalized vibrissa dermal papilla cells (DPC). Especially, dieckol, among the isolated compounds from the E. cava enzymatic extract, showed activity that increased the proliferation of DPC. When NIH3T3 fibroblasts were treated with the E. cava enzymatic extract and the isolated compounds from the E. cava enzymatic extract, the E. cava enzymatic extract increased the proliferation of NIH3T3 fibroblasts, but the isolated compounds such as eckol, dieckol, phloroglucinol and triphlorethol-A did not affect the proliferation of NIH3T3 fibroblasts. On the other hand, the E. cava enzymatic extract and dieckol significantly inhibited 5α-reductase activity. These results suggest that dieckol from E. cava can stimulate hair growth by the proliferation of DPC and/or the inhibition of 5α-reductase activity.

Various treatment options for benign prostatic hyperplasia: A current update

In benign prostatic hyperplasia (BPH) there will be a sudden impact on overall quality of life of patient. This disease occurs normally at the age of 40 or above and also is associated with sexual dysfunction. Thus, there is a need of update on current medications of this disease. The presented review provides information on medications available for BPH. Phytotherapies with some improvements in BPH are also included. Relevant articles were identified through a search of the English-language literature indexed on MEDLINE, PUBMED, Sciencedirect and the proceedings of scientific meetings. The search terms were BPH, medications for BPH, drugs for BPH, combination therapies for BPH, Phytotherapies for BPH, Ayurveda and BPH, BPH treatments in Ayurveda. Medications including watchful waitings, Alpha one adrenoreceptor blockers, 5-alpha reductase inhibitors, combination therapies including tamsulosin-dutasteride, doxazosin-finasteride, terazosin-finasteride, tolterodine-tamsulosin and rofecoxib-finasteride were found. Herbal remedies such as Cernilton, Saxifraga stolonifera, Zi-Shen Pill (ZSP), Orbignya speciosa, Phellodendron amurense, Ganoderma lucidum, Serenoa Repens, pumpkin extract and Lepidium meyenii (Red Maca) have some improvements on BPH are included. Other than these discussions on Ayurvedic medications, TURP and minimally invasive therapies (MITs) are also included. Recent advancements in terms of newly synthesized molecules are also discussed. Specific alpha one adrenoreceptor blockers such as tamsulosin and alfuzosin will remain preferred choice of urologists for symptom relief. Medications with combination therapies are still needs more investigation to establish as preference in initial stage for fast symptom relief reduced prostate growth and obviously reduce need for BPH-related surgery. Due to lack of proper evidence Phytotherapies are not gaining much advantage. MITs and TURP are expensive and are rarely supported by healthcare systems.

New steroidal lactones as 5α-reductase inhibitors and antagonists for the androgen receptor

This study reports the synthesis of several new steroidal lactones: 5α,6β-dibromo-17a-oxa-D-homoandrostane-3β-yl-3'-oxapentanoate (11), 5α,6β-dibromo-17a-oxa-D-homoandrostane-3β-yl-propanoate (12), 5α,6β-dibromo-17a-oxa-D-homoandrostane-3β-yl-butanoate (13), 5α,6β-dibromo-17a-oxa-D-homoandrostane-3β-yl-pentanoate (14), 5α,6β-dibromo-17a-oxa-D-homoandrostane-3β-yl-hexanoate (15), 17a-oxa-D-homoandrost-5-en-17-one-3β-yl-3'-oxapentanoate (16), 17a-oxa-D-homoandrost-5-en-17-one-3β-yl-propanoate (17), 17a-oxa-D-homoandrost-5-en-17-one-3β-yl-butanoate (18), 17a-oxa-D-homoandrost-5-en-17-one-3β-yl-pentanoate (19) and 17a-oxa-D-homoandrost-5-en-17-one-3β-yl-hexanoate (20) with a therapeutic potential as antiandrogens. The biological effect of these steroids was demonstrated in in vivo as well as in vitro experiments. In the in vivo experiments, we measured the activity of ten new steroidal derivatives on the weight of the prostate and seminal vesicle glands of gonadectomized hamsters treated with testosterone. For the in vitro studies, we determined the IC(50) values by measuring the concentration of the steroidal derivatives that inhibits 50% of the activity of the 5α-reductase enzyme present in human prostate and also its binding capacity to the androgen receptors (AR) obtained from rat's prostate cytosol. The results from these experiments indicated that compounds 11-20, significantly decreased the weight of the prostate and seminal vesicles as compared to testosterone treated animals; this reduction of the weight of these glands was comparable to that produced by Finasteride. On the other hand, compounds 11-20 inhibited the enzyme 5α-reductase, with compounds 14-19 (IC(50) values of 4.2 ± 0.95, 0.025 ± 0.003, 1.2 ± 0.45, 1.2 ± 0.1, 0.028 ± 0.003, and 0.069 ± 0.005 nM, respectively) showing the highest inhibitory activity. The results from the in vitro experiments indicated that only 15-17 bind to the AR.

New ester derivatives of dehydroepiandrosterone as 5α-reductase inhibitors

The aim of this study was to synthesize different ester derivatives of dehydroepiandrosterone with therapeutic potential as antiandrogens. The biological effect of these steroids was demonstrated in in vivo as well as in vitro experiments. In the in vivo experiments, we measured the activity of seven steroids on the weight of the prostate and seminal vesicles of gonadectomized hamsters treated with testosterone. For the in vitro studies, we determined the IC(50) values by measuring the concentration of the steroidal derivatives that inhibits 50% of the activity of 5α-reductase present in human prostate and also its binding capacity to the androgen receptors (AR) obtained from rat's prostate cytosol. The results from these experiments indicated that compounds 7 5α,6β-dibromo-3β-propanoyloxyandrostan-17-one, 8 5α,6β-dibromo-3β-butanoyloxyandrostan-17-one and 9 5α,6β-dibromo-3β-(3'-oxapentanoyloxy)-androstan-17-one, significantly decreased the weight of the prostate and seminal vesicles as compared to testosterone treated animals; this reduction of the weight of these glands was comparable to that produced by Finasteride 11. On the other hand, compounds 4 3β-acetoxyandrost-5-en-17-one, 5 3β-hexanoyloxyandrost-5-en-17-one 6 3β-(3'-oxapentanoyloxy)-androst-5-en-17-one, 7 and 12 dehydroepiandrosterone, (commercially available) inhibited the enzyme 5α-reductase. Compounds 4, 5, 6, 8 and 9 (IC(50) values of 5.2±1.2, 0.049±0.002, 6.4±1.1, 0.10±0.045, and 6.8±0.9 nM, respectively) exhibited the highest inhibitory activity. However, none of these compounds binds to the AR.

Molecular interactions of progesterone derivatives with 5 alpha-reductase types 1 and 2 and androgen receptors

The aim of this study was to ascertain the inhibitory effect of several progesterone derivatives for 5 alpha-reductase types 1 and 2 isozymes and to determine the binding to the androgen receptor. The 3,20-dioxopregna-4-ene-17 alpha-yl acetate 4 containing an acetoxy group in C-17 and steroid 17 alpha-hydroxypregn-4-ene-3,20-dione 5 having a hydroxyl group in the same position inhibited both isozymes. On the other hand, 17 alpha-hydroxy-4,5-epoxypregnan-3,20-dione 6 with an epoxy function at C-4, inhibited only the type 1 enzyme. Steroid 4-chloro-17 alpha-hydroxypregn-4-ene-3,20-dione 7a and 4-bromo-17 alpha-hydroxypregn-4-ene-3,20-dione 7b having the C-4 conjugated system and a chlorine or a bromine atom at C-4 respectively, inhibited both types of 5 alpha-reductase. These results indicate that an increase in the electronegativity of ring A produces a major inhibitory activity for 5 alpha-reductase type 1; however this increase was not observed for type 2 enzyme. When the free hydroxyl group of 7a or 7b was esterified, compounds 3,20-dioxo-4-chloropregn-4-ene-17 alpha yl-4-ethylbenzoate 8a and 3,20-dioxo-4-bromopregn-4-ene-17 alpha yl-4-ethylbenzoate 8b were obtained; these steroids inhibited only the 5 alpha-reductase type 2 enzyme. Finasteride and steroids 4, 5, 7b, 8a showed a comparable in vivo pharmacological activity, however the IC(50) values of these compounds were higher as compared to that of finasteride. These results indicated also that steroids 4, 5, 7a, and 7b bind to the androgen receptor whereas compounds 6, 8a and 8b failed to do so. The overall data from this study showed that steroids 5 and 7b bind to the AR and decreased of the growth of prostate and seminal vesicles. Moreover, 4 decreased also the growth of seminal vesicles.

Novel C-6 substituted and unsubstituted pregnane derivatives as 5alpha-reductase inhibitors and their effect on hamster flank organs diameter size

The present study is addressed to ascertain the inhibitory effect of several progesterone derivatives having a chlorine substituent at C-6 (12a-12d), 15 with a bromine substituent at C-6 and 14a-14d, without any halogen atom at C-6 all having an ester side chain at C-17 (benzoate ester bearing a Cl, F and a Br atom at C-4 position of the phenyl ring) on the 5alpha-reductase enzyme activity present in human prostate. In addition, it was also of interest to investigate the pharmacological effect on hamster flank organs diameter size. In order to study the structure-activity relationships of steroids 12a-12d, 14a-14d and 15 we determined the concentration of these steroids that inhibited 50% of the activity of human prostate 5alpha-reductase enzyme (IC(50)), as well as the in vivo effect of these compounds in the hamster flank organs diameter size. We also ascertained, the capacity of these steroids to bind to the androgen receptors present in the rat prostate cytosol using labeled mibolerone (MIB) for monitoring the binding to the androgen receptor. The results from this study indicated that compounds 12a-12d (having a chlorine substituent at C-6), 14a-14d (lacking a halogen atom at C-6), 13 and 15 (having a bromine atom at C-6) showed an increased antiandrogenic effect (lower value for the diameter of the flank organs) as compared to the flank organs from testosterone-treated hamsters. On the other hand, the series of compounds containing a chlorine substituent at C-6 compounds (12a-12d) showed a higher antiandrogenic activity as compared to the compounds lacking a halogen atom at C-6 (14a, 14b and 14d). Although compounds 13 and 15 decreased the flank organs diameter size, however, this increase was not statistically significant as compared to that of the commercially available product finasteride. The steroidal derivatives 13, 14a-14d (lacking the chlorine substituent at C-6) and 15 (having a bromine atom at C-6) exhibited a higher 5alpha-reductase inhibitory activity (lower IC(50) values) as compared to the series of compounds 12a-12d having the halogen substituent at C-6. Finasteride reduced the diameter size of the flank organs. The effect of this steroid and compounds 12a-12d, 13, 14a-14d and 15 on hamster flank organs can be explained by the fact that these steroids did not bind to the androgens receptor, which indicates that its mechanism of action is an inhibiting for the 5alpha-reductase activity. This enzyme is present in the hamster flank organs and was inhibited by the novel steroids in the human prostate homogenates.

New progesterone derivatives as inhibitors of 5α-reductase enzyme and prostate cancer cell growth

In this study we report the synthesis and pharmacological evaluation, in vivo as well as in vitro, of four new progesterone derivatives 4-7. The evaluation in vivo was carried out on gonadectomized male hamsters that were injected subcutaneously daily with 1 mg/Kg of testosterone (T) and/or 1 mg/Kg of finasteride, or with 2 mg/Kg of the novel compounds. It was observed that when testosterone (T) and finasteride or compound 4 were injected together, the weight of the prostate decreased significantly as compared to that oftestosterone-treated animals. Compounds 5-7 did not show any in vivo activity. The 5alpha-reductase inhibitory activity of the novel compounds was determined in vitro using human prostate homogenates; the steroids 4-7 inhibited the 5alpha-reductase activity with IC50 values lower than that for the reference compound finasteride. 3. The effect of compounds 4-7 on the growth of lymphocytes and prostate cancer culture cells line was that steroid 4 inhibited the growth of both cells lines at a concentration of 50 microM and showed a cytotoxic effect whereas compounds 5-7 showed a much lower inhibition. Nevertheless steroids 4-7 didn't exhibit any toxic effects in vivo since the animals remained alive during the six days of treatment.

In vivo and in vitro effect of novel 4,16-pregnadiene-6,20-dione derivatives, as 5alpha-reductase inhibitors

In this study, we report the synthesis and biological evaluation of several new 3-substituted pregna-4,16-diene-6,20-dione derivatives (11a-11d). These compounds were prepared from the commercially available 16-dehydropregnenolone acetate. The biological effect of these steroids was demonstrated in in vivo and in vitro experiments. In the in vivo experiments, we measured the activity of the 11a-11d on the weight of the prostate gland of gonadectomized hamsters treated with testosterone plus finasteride or with the new steroids. For the studies in vitro, we determined the IC50 values by measuring the steroid concentration that inhibits 50% of the activity of 5alpha-reductase present in human prostate. In order to study the mechanism of action of 11a-11d, we also determined the capacity of these steroids to bind to the androgen receptor (AR) present in the rat prostate cytosol using labeled mibolerone as a tracer. The results from this work indicated that compounds 11a-11d significantly decreased the weight of the prostate as compared to testosterone treated animals and this reduction of the weight of the prostate was comparable to that produced by the finasteride. On the other hand 11a-11d exhibited a high inhibitory activity for the human 5alpha-reductase enzyme with IC50 values of 1.4 x 10(-8), 1.8 x 10(-9), 1.0 x 10(-8) and 4 x 10(-5) respectively. However the IC50 value of 11a (1.8 x 10(-9)) was the only one lower than that of finasteride (8.5 x 10(-9)). Nevertheless this compound did not show a higher potency in vivo as compared to that of compounds 11b-11d. The competition analysis for the androgen receptor indicated that the IC50 value of non-labeled mibolerone used in this experiment was 1nM, whereas steroids 10, 11a-11d did not inhibit the labeled mibolerone binding to the androgen receptor. On the other hand, steroid 10 did not show any activities in vitro or in vivo, and for this reason these steroidal derivatives (11a-11d) cannot be considered as prodrugs of compound 10. In conclusion, the compounds containing chlorine 11a, bromine 11b, iodine 11c atoms, and 11d (without any substituent in the ester moiety) at C-3 produce a significant decrease of the prostate weight in castrated animals treated with T and inhibits the activity of the 5alpha-reductase. Apparently the presence of the halogen atoms in compounds 11a-11c enhances the inhibitory activity for the 5alpha-reductase enzyme.

Steroid 5-alpha reductase type 2 activity in biopsies from malignant and normal prostatic tissues

BACKGROUND

The conversion of testosterone (T) to the more potent metabolite dihydrotestosterone (DHT) by prostate-specific steroid 5 alpha-reductase isoenzymes is a key mechanism in the action of androgens in the prostate and it is important in the promotion and progression of prostate diseases. We described an adaptation of a sensitive method for evaluation of the 5 alpha-reductase type 2 (5 alpha-R2) activity using a small quantity of protein.

METHODS

We used 29 human prostate transrectal ultrasound-guided core biopsies obtained from patients (median age 70, range 55-86 y) undergoing this procedure for diagnostic purposes. 4-[(14)C]testosterone and NADPH were incubated with biopsy homogenate. Reaction products were extracted, separated by thin layer chromatography and revealed by autoradiography. Areas correspondent to T and DHT were scraped into vials and their radioactivity determined.

RESULTS

The 5 alpha-R2 activity was expressed as ln (natural logarithm). The assay was validated according to the protein concentration and incubation time linearities. The 5 alpha-R2 activity showed a significant difference between normal and neoplastic tissues with significance level set at P<0.05, mainly in the left prostate lobe. This was independent from the PSA levels.

CONCLUSIONS

Determination of 5 alpha-R2 activity, using the conditions reported herein, could be utilized as an efficient biochemical parameter of prostate neoplastic processes.

Steroids with a carbamate function at C-17, a novel class of inhibitors for human and hamster steroid 5alpha-reductase

In order to study the biological activity of the two novel steroidal carbamates derivatives: 8a and 8b, we determined the concentration of both compounds that inhibit the 50% of the activity of human prostate 5alpha-reductase enzyme, as well as the in vivo effect of these compounds in the weight of hamster prostate and flank organs diameter size. We determined also, the capacity of these steroids to bind to the androgen receptors present in the rat prostate cytosol. Furthermore the activity of these compounds on the mRNA expression of glycerol 3-phosphate acyl transferase (GPAT) in flank organs was analyzed by RT-PCR. This enzyme induces the triglycerides synthesis, which is increased by T in flank organs. The results from this study indicated that steroids 8a and 8b inhibited the human 5alpha-reductase activity. Compound 8b, which contains a bromine atom in the molecule, decreased the inhibitory effect of the human 5alpha-reductase activity, whereas steroid 8a, which lacks a halogen atom did not show any decrease in the activity of this enzyme. The competition studies demonstrated that 8a and 8b did not inhibit mibolerone binding to the androgen receptor present in the rat prostate cytosol. However, the in vivo activity of both steroids was similar; steroids 8a and 8b had a tendency to decrease the weight of the hamster prostate although this parameter was not statistically significant. These compounds also significantly reduced the diameter of the pigmented spot of hamster flank organs, which are androgen dependent skin's pilosebaceous structures. Steroids 8a and 8b, decreased the transcription of mRNA encoding for GPAT in intact hamster's flank organs topically treated in a similar way as in gonadectomized non-treated animals. These results suggest that mRNA encoding for GPAT is induced by DHT in this tissue.

Effect of testosterone and steroids homologues on indolamines and lipid peroxidation in rat brain

The purpose of the present study was to evaluate the effect of 4-pregnen-17-hydroxy-3-one (A) and two steroids homologues: 3beta-acetoxy-5,16-pregnadien-20-one (B) and 3beta-acetoxy-16alpha-17alpha-epoxy-4-pregnen-20-one (C). Male Wistar rats were treated with o-cresol combined (A, B or C) steroids. Lipid peroxidation status as result of measurement reactive substances to thiobarbituric acid (TBARS) as well as serotonin (5-HT) and its precursor 5-hydroxytryptophan (5-HTP) were measured. The prostate glands were weighed, the 5alpha-reductase activity was determined. The animals treated with A, B, and C steroids showed a slight increase in both 5alpha-reductase activity and prostate size. 5-HT and 5-HTP levels did not change significantly, and TBARS showed an increase in the group treated with B steroid and a decrease in the A steroid group with significant differences in both groups (p<0.05) versus control group. Results suggest that A steroid reduces TBARS in rat brain, perhaps as a result of the interaction between the testosterone unsaturated carbons and OH(-) groups with free radicals.

Synthesis and Pharmacological Evaluation of New Progesterone Esters as 5.ALPHA.-Reductase Inhibitors

In this study we report the synthesis and pharmacological evaluation of four new progesterone derivatives; 17alpha-hydroxy-16beta-methylpregna-4,6-diene-3,20-dione 12, 17alpha-cyclopropylcarbonyloxy-16beta-methylpregna-4,6-diene-3,20-dione 13, 17alpha-cyclobutylcarbonyloxy-16beta-methylpregna-4,6-diene-3,20-dione 14, 17alpha-acetoxy-16beta-methylpregna-4,6-diene-3,20-dione 15 and the pregnatriene compound 17alpha-cyclobutylcarbonyloxy-16beta-methylpregna-1,4,6-triene-3,20-dione 16. The pharmacological effect of these compounds was determined in vivo as well as in vitro. The evaluation in vivo was carried out on gonadectomized male hamsters that were injected subcutaneously daily with testosterone (T) and/or finasteride, or with the novel compounds. At the end of the treatments the animals were sacrificed and the prostates were weighed. It was observed that when testosterone (T) and finasteride or compounds 12-16 were injected together, the weight of the prostate decreased significantly as compared to that of the testosterone-treated animals. The 5alpha-reductase inhibitory activity was evaluated in vitro using human prostate homogenates. These experiments showed the following IC50 values: compound 12 (alcohol at C-17) 1.2 x 10(-6) M, 13 (cyclopropyl substituent at C-17) 7.9 x 10(-10) M, 14 (cyclobutyl substituent) 3.2 x 10(-8) M, 15 (acetoxy substituent) 6.3 x 10(-11) M and 16 (cyclobutyl substituent) 3.9 x 10(-6) M. It is evident from these data that when the size of the substituent at C-17 is decreased, the 5alpha-reductase inhibitory activity increases. Apparently, in this biological model, the 5alpha-reductase inhibitory activity depends upon the steric effect of the substituent at C-17. However, the free alcohol 12 showed much lower 5alpha-reductase inhibitory activity.

Hypotheses on how selection for some traits in rodents led to correlated responses in offspring sex ratios

Selective breeding of some species of rodent has sometimes occasioned unexpected and unexplained correlated changes in sex ratio (proportion male) at birth. Experiments in selective breeding for blood pH, sexual drive, body weight, sexual dimorphism in adult body weight, and for resistance to a dietary toxin have all been reportedly accompanied by this strange phenomenon. Here attempts are made to explain this. The overall form of explanation is that selection for any one of these characters is incidentally accompanied by selection for hormone concentrations which in turn are responsible for the variation in sex ratio. For example one may suppose that selection for sexual drive ipso facto selects for offspring sex ratios because, (1) Androgen levels are partially responsible for sexual drive and (2) Androgen levels are also (weakly) genetically determined and (3) Lastly, ex hypothesi, androgen concentrations are partially responsible for offspring sex ratios. If this line of reasoning were correct, the selection for sex drive would be expected to be accompanied by correlated changes in offspring sex ratio.

Novel 17 Substituted Pregnadiene Derivatives as 5.ALPHA.-Reductase Inhibitors and Their Binding Affinity for the Androgen Receptor

The in vitro antiandrogenic activity of four new progesterone derivatives: 4, 5, 6 and 7 (8 is a known compound) was determined. These compounds were evaluated as 5alpha-reductase inhibitors as well as by their capacity to bind to the androgen receptor in gonadectomized hamster prostate. The IC(50) value was determined using increasing concentrations of 4, 5, 6, 7 and 8 in the presence of [(3)H]T and the microsomal fraction of the hamster prostate containing the 5alpha-reductase enzyme. In this paper we also demonstrated the effect of increasing concentrations of the novel steroids upon [(3)H]DHT binding to the androgen receptors from hamster prostate which produces competition for the androgen receptor sites. The in vitro studies showed that steroids 4, 5, 6, 7 and 8 had an inhibitory activity for the 5alpha-reductase with IC(50) of: 4 (0.17 microM), 5 (0.19 microM), 6 (1 microM), 7 (4.2 microM), and 8 (2.7 microM). On the other hand, the IC(50) value for compounds 4, 5, 6, 7, 8 and DHT showed the following order of affinity for the androgen receptor: 6>7>5>DHT. Surprisingly compounds 4 and 8 did not bind to the androgen receptor. The overall data indicate that all synthesized compounds are inhibitors for the enzyme 5alpha-reductase present in the hamster prostate. In contrast, compounds 5, 6 and 7, which have a cyclohexyl group in the side chain showed a high affinity for the androgen receptor.

Molecular Interactions of New Pregnenedione Derivatives

The in vitro inhibitory activity of five new progesterone derivatives: 17alpha-hydroxy-16beta-methylpregna-1,4,6-triene-3,20-dione 1; 16beta-methyl-17alpha-toluoyloxypregna-1,4,6-triene-3,20-dione 2; 17alpha-hydroxy-6-methylenepregn-4-ene-3,20-dione 3; 6-methylene-17alpha-toluoyloxypregn-4ene-3,20-dione 4 and 17alpha-(p-bromobenzoyloxy)-6-methylenepregn-4-ene-3,20-dione 5 was determined. These compounds were evaluated as 5alpha-reductase inhibitors as well as antagonists for the androgen receptor. Compounds 1, 2, 3, 4 and 5 showed the following inhibitory activity for the 5alpha-reductase enzyme with IC(50) values of: 1 (1.65 microM), 2 (10 microM), 3 (19 nM), 4 (100 nM) and 5 (100 nM). The results of this study also showed the effect of increasing concentrations of the novel steroids upon [(3)H]dihydrotestosterone binding to androgen receptors from male hamster prostate. The K(i) values for compounds 1, 2, 3, 4, 5 and dihydrotestosterone showed the following order of affinity for the androgen receptor: 4>5>dihydrotestosterone>2>3>1. The overall data indicated that all synthesized compounds 1, 2, 3, 4 and 5 are inhibitors of the 5alpha-reductase enzyme present in the hamster prostate. In addition compounds 1, 2, 3, 4 and 5 also presented an affinity for the androgen receptor.

Pharmacodynamic analysis of steroid 5alpha-reductase inhibitory actions of Z-350 in rat prostate

The pharmacodynamics of (S)-4-[3-[4-[1-(4-methylphenyl)-3-[4-(2-methoxyphenyl)piperazine-1-yl]propoxy]benzoyl]indole-1-yl] butyric acid hydrochloride (Z-350), which has alpha(1)-adrenoceptor antagonistic and steroid 5alpha-reductase inhibitory effects, were investigated in rats. The disposition of Z-350 was a function of linear kinetics at doses from 1 to 30 mg/kg; the bioavailability was calculated to be 65.2%. The inhibition of 5alpha-reductase was dependent on the concentration of Z-350 in plasma and in the prostate. Analysis of the relationship between the concentration in the prostate and the inhibition seen after a single oral administration showed that the Hill constant was almost 1.0 and EC(50)(n(H)) was 47.4 ng/g of tissue; these parameters did not change after multiple administration. Z-350 inhibited 5alpha-reductase 1 h after oral administration at a dose of 3 mg/kg; maximum inhibition was observed after 2-4 h, and the inhibition (%) was maintained for 24 h after oral administration.

4-(Benzoylindolizinyl)butyric acids; novel nonsteroidal inhibitors of steroid 5alpha-reductase. III

A novel series of indolizinebutyric acids with various benzoyl substituents was synthesized to develop nonsteroidal inhibitors of steroid 5alpha-reductase, and the structure-activity relationships in this series were studied. We previously reported the structure-activity relationships in a series of indolebutyric acids as well as the discovery of the novel nonsteroidal 5alpha-reductase inhibitor, FK143. We have now made other modifications to this compound to improve in vivo inhibitory activity. By altering the heterocyclic nucleus and changing the benzoyl substituent we have succeeded in identifying the strongly active compound, FK687, (S)-4-[1-[4-[[1-(4-isobutylphenyl)butyl]oxy]benzoyl]indolizin-3-yl]butyric acid, which displays strong in vitro inhibitory activity against the human enzyme and in vivo inhibitory activity against the castrated young rat model. This compound should be a useful agent for the treatment of benign prostatic hyperplasia.

Kinetic analysis of LY320236: competitive inhibitor of type I and non-competitive inhibitor of type II human steroid 5alpha-reductase

Type I and type II steroid 5alpha-reductases (5alpha-R) catalyze the conversion of testosterone (T) to dihydrotestosterone (DHT). LY320236 is a benzoquinolinone (BQ) that inhibits 5alpha-R activity in human scalp skin (Ki(typeI)=28.7+/-1.87 nM) and prostatic homogenates (Ki(typeII)=10.6+/-4.5 nM). Lineweaver-Burk, Dixon, and non-linear analysis methods were used to evaluate the kinetics of 5alpha-R inhibition by LY320236. Non-linear modeling of experimental data evaluated V(max) in the presence or absence of LY320236. Experimental data modeled to the following equation 1v=+ fixing the In0c value equal to 1.0 or 0 are consistent with non-competitive or competitive inhibition, respectively. LY320236 is a competitive inhibitor of type I 5alpha-R (In0c=0, Ki=3.39+/-0.38, RMSE = 1.300) and a non-competitive inhibitor of type II 5alpha-R (In0c=1, Ki=29. 7+/-3.4, RMSE = 0.0592). These data are in agreement with linear transformation of the data using Lineweaver-Burk and Dixon analyses. These enzyme kinetic data support the contention that the BQ LY320236 is a potent dual inhibitor with differing modes of activity against the two known human 5alpha-reductase isozymes. LY320236 represents a class of non-steroidal 5alpha-R inhibitors with potential therapeutic utility in treating a variety of androgen dependent disorders.

Dual-acting agents with alpha1-adrenoceptor antagonistic and steroid 5alpha-reductase inhibitory activities. Synthesis and evaluation of arylpiperazine derivatives

A series of arylpiperazine derivatives were prepared and evaluated for their alpha1-adrenoceptor antagonistic activities and 5alpha-reductase inhibitory activities. SAR study led to the identification of the potent dual-acting compound 2f, which had a pA2 value of 7.5 for alpha1-adrenoceptor antagonism and an IC50 value of 1.5 nM for 5alpha-reductase inhibition.

N-substituted 4-(5-indolyl)benzoic acids. Synthesis and evaluation of steroid 5alpha-reductase type I and II inhibitory activity

The synthesis of N-alkyl and N-arylalkyl substituted 4-(5-indolyl)benzoic acid derivatives as inhibitors of steroid 5alpha-reductases is described. For the human type II isozyme a benzyl substituent (IC50 6.20 microM) and for the human type I isozyme a cyclohexanemethyl substituent (IC50 2.10 microM) on the indole nitrogen proved to be most efficacious, thus providing interesting leads for the development of drugs for the treatment of benign prostatic hyperplasia (BPH).

The neurosteroids, progesterone and 3alpha,5alpha-THP, enhance sexual motivation, receptivity, and proceptivity in female rats

The effects of progesterone (P) and the neurosteroid and P metabolite, 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP) on ovariectomized (ovx), estradiol-3-benzoate (EB)-primed rats on sexual motivation, receptivity, and proceptivity were examined. Changes in central P and 3alpha,5alpha-THP were measured following administration of EB, EB+P, EB+3alpha,5alpha-THP, or EB+inhibitor of 5alpha-reductase or P metabolism (epostane and finasteride)+P (Expt. 1). Partner preference was measured as the duration of time females in these different hormonal treatments spent in proximity to a male vs. female conspecific (Expt. 2). Receptivity (lordosis quotients and ratings) and proceptivity (darting, hopping, ear wiggling, and pacing), for different hormone treatments were assessed (Expt. 3 and Expt. 4, respectively). Conditioned place preference following hormone treatments and paced mating enabled assessment of sexual motivation (Expt. 5). Central P and 3alpha,5alpha-THP were measured in various combinations of hormone/mating conditions (Expt. 6). Studies revealed that 3alpha,5alpha-THP has a significant role in these reproductive measures. Brain concentrations of 3alpha, 5alpha-THP were significantly higher in animals receiving EB+P or EB+3alpha,5alpha-THP compared to animals receiving EB alone, or EB+P in conjunction with an inhibitor of P metabolism. EB+P and EB+3alpha, 5alpha-THP significantly increased time spent in proximity to the male, receptivity and proceptivity. When administered to ovx, EB-primed rats, the progestin metabolite, 3alpha,5alpha-THP, had effects on these behaviors similar to P. Epostane, an inhibitor of P and 3alpha,5alpha-THP biosynthesis, and finasteride, an inhibitor of P metabolism to 3alpha,5alpha-THP, administered to EB+P animals reduced male partner preference, proceptive, and receptive behaviors to levels seen in EB+vehicle animals. Notably, whole brain 3alpha, 5alpha-THP levels were significantly increased and whole brain P levels were significantly reduced in paced mated rats compared to standard mated, and receptive non-mated animals. These studies suggest that P and 3alpha,5alpha-THP may have some common effects on reproductive behavior, e.g., sexual motivation, receptivity, and proceptivity.

Pharmacokinetics and pharmacodynamics of FK143, a nonsteroidal inhibitor of steroid 5 alpha-reductase, in healthy volunteers

The pharmacokinetics and pharmacodynamics of FK143, a new nonsteroidal inhibitor of steroid 5 alpha-reductase, were investigated in healthy volunteers, with use of plasma FK143 concentrations and serum dihydrotestosterone levels as an index for pharmacologic effects. The area under the plasma concentration-time curve from zero to infinity [AUC(0-infinity)] and maximum plasma concentration [Cmax] were increased dose proportionally after oral administration (100 to 500 mg) while subjects were in the fed state. The AUC(0-infinity) and Cmax after 500 mg oral administration during fed conditions were significantly larger than those during the fasted state, suggesting an increase of the absorption of FK143. Dihydrotestosterone concentrations after a single administration of FK143 (100 to 500 mg) during fed conditions decreased to about 65% of predose values and thereafter slowly recovered to the same levels as predose values at 168 hours. A combined pharmacokinetic-pharmacodynamic model was constructed with use of changes in dihydrotestosterone concentrations. The pharmacokinetic-pharmacodynamic profiles of FK143 after repeated administration were predictable with use of the pharmacokinetic-pharmacodynamic parameters obtained after a single administration of FK143.

Inhibition of rat prostate carcinogenesis by a 5alpha-reductase inhibitor, FK143

BACKGROUND

Androgen levels in the prostate may influence carcinogenesis in this organ. Inhibitors of the enzyme 5alpha-reductase block conversion of testosterone to the more active androgen dihydrotestosterone. The use of a 5alpha-reductase inhibitor, finasteride, in the chemoprevention of prostate cancer is being evaluated in a clinical trial.

PURPOSE

This study was conducted to determine if a 5alpha-reductase inhibitor, FK143, inhibits the development of prostate cancer in rats.

METHODS

Male ACI/Seg rats, which spontaneously develop prostate cancer, were randomly assigned at 80 weeks of age to receive one of three diets (n = 35/group) containing 0 (i.e., control group), 20, or 200 ppm FK143. At 140 weeks of age, the animals were killed, and the prostates were removed and examined for histopathologic features in addition to being assayed for androgen concentrations. Two-sided statistical tests were used to calculate all P values.

RESULTS

The incidence of prostate carcinoma in the control group was 62.9% (22 of 35 rats); in the group fed the 20 ppm FK143-containing diet, it was 45.7% (16 of 35); and in the group fed the 200 ppm FK143-containing diet, it was 67.6% (23 of 34) (overall, P = .153). The corresponding incidences of macroscopic lesions were 17.1% (six of 35 rats), 0% (none of 35), and 23.5% (eight of 34), respectively (overall, P = .004). The incidence of macroscopic lesions in the prostates of rats in the 20-ppm diet group was significantly lower than that in the control group (P = .029) or that in the 200-ppm diet group (P = .003). Intraprostatic dihydrotestosterone content was significantly lower in rats in the groups fed diets containing 20 or 200 ppm FK143 (mean values: 4.51 and 4.33 pg/mg wet weight of prostate tissue, respectively) than in the control group (6.10 pg/mg) (overall, P<.001); by contrast, testosterone was higher in the 200-ppm diet group (2.09 pg/mg) than in the control group (1.08 pg/mg) or the 20-ppm diet group (1.21 pg/mg) (overall, P<.001).

CONCLUSIONS

FK143, when fed to rats at 20 or 200 ppm, significantly reduced the level of dihydrotestosterone in their prostate tissue. However, the incidence of macroscopic cancer in the prostate was suppressed in rats consuming the 20 ppm FK143-containing diet but not in those consuming the 200-ppm diet. The lack of dose dependence for the chemopreventive activity of FK143 may be explained by the reciprocal increase of tissue testosterone in the 200-ppm diet group.

IMPLICATIONS

The 5alpha-reductase inhibitor FK143 may, at specific doses, reduce the incidence of spontaneously developing prostate cancer; however, whether these findings in rats will apply to humans remains to be determined.

FR146687, a novel steroid 5 alpha-reductase inhibitor: in vitro and in vivo effects on prostates

BACKGROUND

Steroid 5 alpha-reductase is implicated in the pathogenesis of benign prostatic hyperplasia (BPH). We studied the in vitro and in vivo effects of FR146687, a new inhibitor of 5 alpha-reductase.

METHODS

Two isozymes of rat and human 5 alpha-reductases were expressed in 293 cells. In vivo effects of drugs were evaluated on rat and dog prostates. Castrated immature rats were injected with testosterone propionate (TP) or 5 alpha-dihydrotestosterone propionate (DHTP) to induce growth of the ventral prostates. Testosterone and 5 alpha-dihydrotestosterone (DHT) contents in rat and dog prostates were measured by gas chromatography-mass spectrophotometry (GC-MS).

RESULTS

FR146687 showed noncompetitive inhibition in both isozymes and no inhibitory effects on other steroid oxidoreductases. In mature rats and castrated immature rats treated with TP, FR146687 dose-dependently reduced ventral prostate and seminal vesicle weight at doses above 0.1 mg/kg, while castrated immature rats treated with DHTP were not affected by FR146687. FR146687 showed more potent reduction of rat prostates than finasteride. DHT concentration in the prostates was significantly reduced when FR146687 was administered to rats and beagles.

CONCLUSIONS

FR146687 is a dual inhibitor for 5 alpha-reductase isozymes and significantly reduced the growth and DHT content in the prostate.

Inhibition of rat alpha-reductases by finasteride: evidence for isozyme differences in the mechanism of inhibition

The mechanism of inhibition of the rat types 1 and 2 5alpha-reductase by finasteride was investigated using recombinantly expressed enzymes. These studies revealed that finasteride is a potent, reversible inhibitor of the rat type 1 5alpha-reductase with Ki=10.2+/-1.3 nM. Finasteride is a potent inhibitor of the rat type 2; however, in this case the compound binds to the type 2 isozyme-NADPH complex to form a ternary complex with Ki=1.19+/-0.10 nM, which then rearranges to a high affinity complex (E:I) with a pseudo first order rate constant of 1.62+/-0.22 x 10(-3)/s. The second order rate constant is k3/Ki=1.37+/-0.31 x 10(6) M/s. Heat denaturation of the (type 2 enzyme:inhibitor) complex releases dihydrofinasteride and presumably the NADP+-adduct previously identified with the human 5alpha-reductases. The effects of finasteride were also studied in intact COS cells transiently expressing the rat types 1 and 2 5alpha-reductase. Results with whole cell assays confirm differences in mechanism of inhibition of rat types 1 and 2 5alpha-reductase by finasteride.