Discovery and therapeutic promise of selective androgen receptor modulators

Androgens are essential for male development and the maintenance of male secondary characteristics, such as bone mass, muscle mass, body composition, and spermatogenesis. The main disadvantages of steroidal androgens are their undesirable physicochemical and pharmacokinetic properties. The recent discovery of nonsteroidal selective androgen receptor modulators (SARMs) provides a promising alternative for testosterone replacement therapies with advantages including oral bioavailability, flexibility of structural modification, androgen receptor specificity, tissue selectivity, and the lack of steroid-related side effects.     

Serendipitous discovery of novel imidazolopyrazole scaffold as selective androgen receptor modulators

A novel imidazolopyrazole derivative has been fortuitously discovered as potent selective androgen receptor modulator with in vivo efficacy.     

Arylisothiocyanato selective androgen receptor modulators (SARMs) for prostate cancer

A new series of androgen receptor targeted agents (ARTA) was prepared and tested in androgen-dependent and -independent prostate cancer cell lines. These agents were bicalutamide analogs with isothiocyanato substituted B-rings. Also, the linker sulfone of R-bicalutamide was maintained or replaced with several alternative linkages including ether, amine, N-methylamine, thioether, and methylene (in this case the product was a racemic mixture) functional groups at the X-position. To expand the structure-activity relationship (SAR) of these arylisothiocyanato AR ligands, B-ring halogenated arylisothiocyanato ligands were also prepared and tested. The arylisothiocyanato AR ligands showed strong binding affinities to AR ranging from 0.6 to 54 nM. Among them, thioether and ether linkages demonstrated high binding affinities (0.6 and 4.6 nM, respectively) and selective cell growth inhibition (approximately 3- to 6-fold) for LNCaP, an androgen-dependent prostate cancer cell line, when compared to the androgen independent prostate cell lines (DU145, PC-3, and PPC-1) and a bladder cell line (TSU-Pr1). However, the ligands were inactive (IC50>100 mM) in a normal monkey kidney cell line (CV-1) that was used as the control for non-specific toxicity.     

Novel selective androgen receptor modulators: SAR studies on 6-bisalkylamino-2-quinolinones

A series of selective androgen receptor modulators (SARMs) with a wide spectrum of receptor modulating activities was developed based on optimization of the 4-substituted 6-bisalkylamino-2-quinolinones (3). Significance of the trifluoromethyl group on the side chains and its interactions with amino acid residues within the androgen receptor (AR) ligand binding domain are discussed. A representative analog (9) was tested orally in a rodent model of hypogonadism and demonstrated desirable tissue selectivity.     

Synthesis and SAR of novel hydantoin derivatives as selective androgen receptor modulators

A novel series of hydantoin derivatives were identified by in vivo studies as tissue selective androgen receptor modulators. SAR around this series revealed that the function of the ligand could be altered by minor structural modification.     

Synthesis of potent, substituted carbazoles as selective androgen receptor modulators (SARMs)

The synthesis and in vitro binding affinity for a novel series of potent androgen receptor modulators is described. One of the more potent compounds (17, RAD35010) was further characterized in vivo where it restored levator ani weight in castrated male rats to near sham level while having no significant effect on prostate weight.     

Linking ligand-induced alterations in androgen receptor structure to differential gene expression: a first step in the rational design of selective androgen receptor modulators

We have previously identified a family of novel androgen receptor (AR) ligands that, upon binding, enable AR to adopt structures distinct from that observed in the presence of canonical agonists. In this report, we describe the use of these compounds to establish a relationship between AR structure and biological activity with a view to defining a rational approach with which to identify useful selective AR modulators. To this end, we used combinatorial peptide phage display coupled with molecular dynamic structure analysis to identify the surfaces on AR that are exposed specifically in the presence of selected AR ligands. Subsequently, we used a DNA microarray analysis to demonstrate that differently conformed receptors facilitate distinct patterns of gene expression in LNCaP cells. Interestingly, we observed a complete overlap in the identity of genes expressed after treatment with mechanistically distinct AR ligands. However, it was differences in the kinetics of gene regulation that distinguished these compounds. Follow-up studies, in cell-based assays of AR action, confirmed the importance of these alterations in gene expression. Together, these studies demonstrate an important link between AR structure, gene expression, and biological outcome. This relationship provides a firm underpinning for mechanism-based screens aimed at identifying SARMs with useful clinical profiles.     

Identification of neuron selective androgen receptor inhibitors

AIM To identify neuron-selective androgen receptor(AR) signaling inhibitors, which could be useful in the treatment of spinal and bulbar muscular atrophy(SBMA), or Kennedy's disease, a neuromuscular disorder in which deterioration of motor neurons leads to progressive muscle weakness. METHODS Cell lines representing prostate, kidney, neuron, adipose, and muscle tissue were developed that stably expressed the CFP-AR-YFP FRET reporter. We used these cells to screen a library of small molecules for cell typeselective AR inhibitors. Secondary screening in luciferase assays was used to identify the best cell-type specific AR inhibitors. The mechanism of action of a neuronselective AR inhibitor was examined in vitro using luciferase reporter assays, immunofluorescence microscopy, and immunoprecipitations. Rats were treated with the most potent compound and tissue-selective AR inhibition was examined using RT-q PCR of AR-regulated genes and immunohistochemistry.RESULTS We identified the thiazole class of antibiotics as com-pounds able to inhibit AR signaling in a neuronal cell line but not a muscle cell line. One of these antibiotics, thiostrepton is able to inhibit the activity of both wild type and polyglutamine expanded AR in neuronal GT1-7 cells with nanomolar potency. The thiazole antibiotics are known to inhibit FOXM1 activity and accordingly, a novel FOXM1 inhibitor FDI-6 also inhibited AR activity in a neuron-selective fashion. The selective inhibition of AR is likely indirect as the varied structures of these compounds would not suggest that they are competitive antagonists. Indeed, we found that FOXM1 expression correlates with cell-type selectivity, FOXM1 co-localizes with AR in the nucleus, and that sh RNA-mediated knock down of FOXM1 reduces AR activity and thiostrepton sensitivity in a neuronal cell line. Thiostrepton treatment reduces FOXM1 levels and the nuclear localization of beta-catenin, a known co-activator of both FOXM1 and AR, and reduces the association between beta-catenin and AR. Treatment of rats with thiostrepton demonstrated AR signaling inhibition in neurons, but not muscles. CONCLUSION Our results suggest that thiazole antibiotics, or other inhibitors of the AR-FOXM1 axis, can inhibit AR signaling selectively in motor neurons and may be useful in the treatment or prevention of SBMA symptoms.     

糖皮质激素受体及其选择性调节剂研究进展

糖皮质激素（glucocorticoids,GCs）是临床上广泛使用的一类抗炎药物,在体内主要通过糖皮质激素受体（glucocorticoid receptor,GR）发挥生理和药理作用。GR是核受体超家族的成员之一,为配体激活的转录因子,在机体的多种生理和病理活动中扮演重要的角色。随着对GR信号通路的深入研究,寻找针对糖皮质激素受体的新型调节剂,以期将抗炎作用和现有糖皮质激素的副作用相分离,已经成为新药发现的研究热点。本文对近年来GR的分子结构、生物学作用及其选择性调节剂的研究进展作一简要的介绍。     

Deoxybenzoins are novel potent selective estrogen receptor modulators

Deoxybenzoins are plant compounds with similar structure to isoflavones. In this study, we evaluated the ability of two synthesized deoxybenzoins (compound 1 and compound 2) (a) to influence the activity of the estrogen receptor subtypes ERalpha and ERbeta in HeLa cells co-transfected with an estrogen response element-driven luciferase reporter gene and ERalpha- or ERbeta-expression vectors, (b) to modulate the IGFBP-3 and pS2 protein in MCF-7 breast cancer cells, (c) to induce mineralization of KS483 osteoblasts and (d) to affect the cell viability of endometrial (Ishikawa) and breast (MCF-7, MDA-MB-231) cancer cells. Docking and binding energy calculations were performed using the mixed Monte Carlo/Low Mode search method (Macromodel 6.5). Compound 1 displayed significant estrogenic activity via ERbeta but no activity via ERalpha. Compound 2 was an estrogen-agonist via ERalpha and antagonist via ERbeta. Both compounds increased, like the pure antiestrogen ICI182780, the IGFBP-3 levels. Compound 2 induced, like 17beta-estradiol, significant mineralization in osteoblasts. The cell viability of Ishikawa cells was unchanged in the presence of either compound. Compound 1 increased MCF-7 cell viability consistently with an increase in pS2 levels, whereas compound 2 inhibited the cell viability. Molecular modeling confirmed the agonistic or antagonistic behaviour of compound 2 via ER subtypes. Compound 2, being an agonist in osteoblasts, an antagonist in breast cancer cells, with no estrogenic effects in endometrial cancer cells, makes it a potential selective estrogen receptor modulator and a choice for hormone replacement therapy.     

Tetrahydroquinoline-based selective estrogen receptor modulators (SERMs)

A new series of estrogen receptor ligands based on a 6-hydroxy-tetrahydroquinoline scaffold is described, in addition to their binding affinity and functional activity in MCF-7 cells. Several 1,2-disubstituted tetrahydroquinolines bearing a basic side chain were shown to be high affinity ligands and antagonists in the MCF-7 proliferation assay. Compounds lacking the basic side chain were agonists in the MCF-7 assay.     

Design and synthesis of tricyclic tetrahydroquinolines as a new series of nonsteroidal selective androgen receptor modulators (SARMs)

Some tricyclic tetrahydroquinolines (THQs) were found to have the potential of a new series of nonsteroidal selective androgen receptor modulators (SARMs). Compound 5b was first designed and synthesized under our hypothesis based on a four-point pharmacophoric requirement of the 3-carbonyl, 18-methyl, 17-hydroxyl, and 13-quaternary carbon groups of dihydrotestosterone (DHT). It was revealed that this compound exhibits not only a strong androgen receptor (AR) agonistic activity (EC₅₀ = 9.2 nM) but also the highest selectivity in binding affinity to AR among the steroid hormone receptors. Furthermore, this compound showed a weak virilizing effect with retention of the desired anabolic effect as compared with DHT in vivo.     

Tetrahydroquinolines as a novel series of nonsteroidal selective androgen receptor modulators: structural requirements for better physicochemical and biological properties

A rationally designed tetrahydroquinoline (1) for nonsteroidal selective androgen receptor modulators was modified for the exploration of promising compounds by Grieco three-component condensation using various dienophiles. Based on the in vitro effects and physicochemical properties of the synthesized compounds, compound 4c was selected for further study. Compound 4c increased the femoral bone mineral density as much as DHT, but it reduced the uterus effect compared with DHT in ovariectomized rats. Thus, compound 4c has desirable osteoanabolic effects with weak undesirable effects on the uterus in a female osteoporosis model.     

C19-steroids as androgen receptor modulators: design, discovery, and structure-activity relationship of new steroidal androgen receptor antagonists

Dehydroepiandrosterone (DHEA), the most abundant steroid in human circulating blood, is metabolized to sex hormones and other C19-steroids. Our previous collaborative study demonstrated that androst-5-ene-3beta,17beta-diol (Adiol) and androst-4-ene-3,17-dione (Adione), metabolites of DHEA, can activate androgen receptor (AR) target genes. Adiol is maintained at a high concentration in prostate cancer tissue; even after androgen deprivation therapy and its androgen activity is not inhibited by the antiandrogens currently used to treat prostate cancer patients. We have synthesized possible metabolites of DHEA and several synthetic analogues and evaluated their role in androgen receptor transactivation to identify AR modulators. Steroids with low androgenic potential in PC-3 cell lines were evaluated for anti-dihydrotestosterone (DHT) and anti-Adiol activity. We discovered three potent antiandrogens: 3beta-acetoxyandrosta-1,5-diene-17-one 17-ethylene ketal (ADEK), androsta-1,4-diene-3,17-dione 17-ethylene ketal (OAK), and 3beta-hydroxyandrosta-5,16-diene (HAD) that antagonized the effects of DHT as well as of Adiol on the growth of LNCaP cells and on the expression of prostate-specific antigen (PSA). In vivo tests of these compounds will reveal their potential as potent antiandrogens for the treatment of prostate cancer.     

Preclinical experience with two selective progesterone receptor modulators on breast and endometrium

Org 31710 and Org 33628 are two highly selective progesterone receptor modulators (PRMs) with respect to their anti-progestational and anti-glucocorticoid activity. The compounds have been studied both in vitro and in vivo. Org 33628 has approximately four times stronger anti-progestational activity in vitro than does Org 31710, and in rats it is about 15 times more potent in the pregnancy interruption test. Two main indications for the use of PRMs are breast cancer and fertility regulation. The effects of both Org 31710 and Org 33628 were tested in relevant models for these indications. The effects of the two compounds on breast tumor development were assessed and in rats using the DMBA model. Their potency in menses induction was tested in monkeys on a 4-day regimen in the luteal phase, and after a single dose at day 21 of the normal cycle, and under a continuous progestin treatment using desogestrel. The compounds were also tested alone in a continuous low-dose regimen. The effects on follicular development and ovulation were determined by measuring estradiol and progesterone levels. Cycle control was monitored by daily vaginal swabs. In the DMBA model, Org 31710 at oral doses of 0.8, 2.0, and 5.0 mg/kg showed a clear dose-related reduction in tumor load. With the two highest doses, an even lower tumor load was seen after a 3-week treatment period compared to the tumor load at the start of treatment. Org 33628 showed a similar efficacy as Org 31710 at a dose of 2.0 mg/kg. RU 486 after oral treatment was two times less potent in this model than Org 31710 and Org 33628. The efficacy of menses induction using the 4-day regimen is dependent on the time of administration relative to the progesterone peak in the luteal phase. The highest efficacy is achieved in the descending part of the peak, at which a 100% success rate is found with a dose of 1 mg/kg of either Org 31710 or Org 33628. In Cynomolgus monkeys, at a single dose of 15 mg/kg of Org 31710 or Org 33628 in the luteal phase, menses induction was achieved only in 60% of the treatment cycles. Surprisingly menses induction can be achieved with a single dose that is about a ten-times lower when the monkeys are treated continuously with desogestrel. Cycle control is better at low than at high doses of antiprogestin in combination with daily dosing of 4 microg/kg desogestrel. Despite the difference in receptor affinity, no difference between Org 31710 and Org 33628 was found in menses induction. In the continuous low-dose (1 mg/kg) regimen with the PRMs, follicular development occurs normally while ovulation is inhibited. Ovulation is resumed shortly after stopping treatment, and a normal menses occurs after the first progesterone peak. Both compounds may be interesting options for the prevention and treatment of breast cancer and for fertility control.