FK143, a novel nonsteroidal inhibitor of steroid 5 alpha-reductase: (2) In vivo effects on rat and dog prostates

Virtual screening approach for the discovery of selective 5α-reductase type II inhibitors for benign prostatic hyperplasia treatment

Background: 5α-Reductase type II (5αR2) inhibition is a promising strategy for benign prostatic hyperplasia treatment. A computational approach including virtual screening, ligand-based 3D pharmacophore modeling, 2D quantitative structure-activity relationship and molecular docking simulations were adopted to develop novel inhibitors. Results: Hits were first filtered via the validated pharmacophore and 2D quantitative structure-activity relationship models. Docking on the recently determined cocrystallized structure of 5αR2 showed three promising hits. Visual inspection results were compared with finasteride ligand and dihydrotestosterone as reference, to explain the role of binding to Glu57 and Tyr91 for 5αR2 selective inhibition. Conclusion: Alignment between Hit 2 and finasteride in the binding pocket showed similar binding modes. The biological activity prediction showed antitumor and androgen targeting activity of the new hits.

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.

Actions of 5alpha-reductase inhibitors on the epididymis

Testosterone is converted to the more biologically active androgen, dihydrotestosterone (DHT), by steroid 5alpha-reductase. Two isozymes of 5alpha-reductase, types 1 and 2, are abundantly expressed in the epididymis. DHT is the androgen found in the nuclei of epididymal cells and is essential for the maturation of spermatozoa. Thus, one approach to block androgen action in the epididymis is to inhibit DHT formation. Several compounds have been reported to inhibit either one or both forms of 5alpha-reductase in many tissues. The first commercially available inhibitor of 5alpha-reductase, finasteride, has a predominant effect on the type 2 isozyme, while more recently developed agents, such as dutasteride, PNU157706 and FK143, act as dual inhibitors. We found that the treatment of adult rats with such agents results in pronounced effects on the expression of genes essential to the formation of the optimal luminal microenvironment that is required for proper sperm maturation. Furthermore, drug treatment caused a significant decrease in the percentage of progressively motile and morphologically normal spermatozoa in the cauda epididymides. Mating females to treated males resulted in fewer successful pregnancies and a higher rate of pre-implantation loss. Thus, there may be a role for dual 5alpha-reductase inhibitors as potential components of a male contraceptive.

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.

Hormonal effects of Z-350, possessing steroid 5alpha-reductase inhibitory and alpha1-adrenoceptor antagonistic actions, in the rat

We examined the hormonal effects of Z-350, (S)-4-[3-(4-[1-(4-methylphenyl)-3-[4-(2-methoxyphenyl)piperazine-1-yl]propoxy]benzoyl)indole-1-yl]butyric acid hydrochloride, which has both alpha1-adrenoceptor blocking activity and steroid 5alpha-reductase inhibitory activity, in male and female rats. Z-350 administered orally for 14 days at a dose of 30 mg/kg to normal male rats significantly reduced the weight of the prostate and seminal vesicles without affecting the weight of the testis, epididymis, adrenals, kidney or liver. Prostatic levels of dihydrotestosterone decreased dose-dependently, with a slight increase in the level of testosterone at a Z-350 dose of 100 mg/kg. We observed no effects on the weight of the prostate in castrated rats or on the weight of the uterus in normal or 17beta-estradiol-treated female rats. These results suggest that Z-350 inhibits prostatic growth via inhibition of steroid 5-reductase without other hormonal effects.

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.

The mechanism of epristeride against benign prostatic hyperplasia

Epristeride, a 5alpha-reductase inhibitor, decreases prostate size and improves symptoms in men with benign prostatic hyperplasia. However, little is known about the histopathology of the prostate after treatment with epristeride. To study the relationship between apoptosis and the mechanism of epristeride in the treatment of benign prostatic hyperplasia, the induction of apoptosis by epristeride was detected and measured in vitro by: (a) observing morphological changes in cells by light microscopy; (b) comparing the relative content of dihydrotestosterone in the rat prostate epithelial cells untreated and treated with epristeride by microspectrophotometry; (c) estimating changes in cell size and DNA integrity by flow cytometry; and (d) monitoring nucleosomal DNA fragmentation by agarose gel electrophoresis. The cells treated with epristeride showed a reduction in cell size, an increase in the cytoplasm/nuclear ratio, which is indicative of the condensation of nuclear chromatin, a significant decrease in optical density at 580 nm (OD580 nm), and an oligonucleosomal ladder and a subdiploid peak of DNA characteristic of apoptosis. Therefore, the mechanism of epristeride in the treatment of benign prostatic hyperplasia might be apoptosis stimulated by decreasing dihydrotestosterone level.

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.