Nonsteroidal Androgen Receptor Ligand Research Articles

Induction of double-strand breaks with the non-steroidal androgen receptor ligand flutamide in patients on androgen suppression: a study protocol for a randomized, double-blind prospective trial

BackgroundProstate cancer remains the most prevalent malignancy and the second-leading cause of cancer-related death in men in the USA. Radiation therapy, typically with androgen suppression, remains a mainstay in the treatment of intermediate- and high-risk, potentially lethal prostate cancers. However, local recurrence and treatment failure remain common. Basic and translational research has determined the potential for using androgen receptor (AR) ligands (e.g., dihydrotestosterone and flutamide) in the context of androgen-deprived prostate cancer to induce AR- and TOP2B-mediated DNA double-strand breaks (DSBs) and thereby synergistically enhance the effect of radiation therapy (RT). The primary aim of this study is to carry out pharmacodynamic translation of these findings to humans.MethodsPatients with newly diagnosed, biopsy-confirmed localized prostatic adenocarcinoma will be recruited. Flutamide, an oral non-steroidal androgen receptor ligand, will be administered orally 6–12 h prior to prostate biopsy (performed under anesthesia prior to brachytherapy seed implantation). Key study parameters will include the assessment of DNA double-strand breaks by γH2A.x foci and AR localization to the nucleus. The initial 6 patients will be treated in a single-arm run-in phase to assess futility by establishing whether at least 2 subjects from this group develop γH2A.x foci in prostate cancer cells. If this criterion is met, the study will advance to a two-arm, randomized controlled phase in which 24 participants will be randomized 2:1 to either flutamide intervention or placebo standard-of-care (with all patients receiving definitive brachytherapy). The key pharmacodynamic endpoint will be to assess whether the extent of γH2A.x foci (proportion of cancer cells positive and number of foci per cancer cell) is greater in patients receiving flutamide versus placebo. Secondary outcomes of this study include an optional, exploratory analysis that will (a) describe cancer-specific methylation patterns of cell-free DNA in plasma and urine and (b) assess the utility of serum and urine samples as a DNA-based biomarker for tracking therapeutic response.DiscussionThis study will confirm in humans the pharmacodynamic effect of AR ligands to induce transient double-strand breaks when administered in the context of androgen deprivation as a novel therapy for prostate cancer. The findings of this study will permit the development of a larger trial evaluating flutamide pulsed-dose sequencing in association with fractionated external beam RT (+/− brachytherapy). The study is ongoing, and preliminary data collection and recruitment are underway; analysis has yet to be performed.Trial registrationClinicalTrials.gov NCT03507608. Prospectively registered on 25 April 2018.

A new avenue toward androgen receptor pan-antagonists: C2 sterically hindered substitution of hydroxy-propanamides.

The androgen receptor (AR) represents the primary target for prostate cancer (PC) treatment even when the disease progresses toward androgen-independent (AIPC) or castration-resistant (CRPC) forms. Because small chemical changes in the structure of nonsteroidal AR ligands determine the pharmacological responses of AR, we developed a novel stereoselective synthetic strategy that allows sterically hindered C2-substituted bicalutamide analogues to be obtained. Biological and theoretical evaluations demonstrate that C2-substitution with benzyl and phenyl moieties is a new, valuable option toward improving pan-antagonist behavior. Among the synthesized compounds, (R)-16m, when compared to casodex, (R)-bicalutamide, and enzalutamide, displayed very promising in vitro activity toward five different prostate cancer cell lines, all representative of CPRC and AIPC typical mutations. Despite being less active than (R)-bicalutamide, (R)-16m also displayed marked in vivo antitumor activity on VCaP xenografts and thus it may serve as starting point for developing novel AR pan-antagonists.

Pharmacological characterization of an imidazolopyrazole as novel selective androgen receptor modulator

Selective androgen receptor modulators (SARMs) are androgens with tissue-selective activity. SARMs that have anabolic activity on muscle while having minimal stimulatory activity on prostate are classified as SARM agonists. They can be used to prevent the loss of lean body mass that is associated with cancer, immunodeficiency, renal disease and aging. They may also have anabolic activity on bone; thus, unlike estrogens, they may reverse the loss of bone strength associated with aging or hypogonadism. Our in-house effort on SARM program discovers a nonsteroidal androgen receptor ligand with a unique imidazolopyrazole moiety in its structure. In vitro, this compound is a weak androgen receptor binder and a weak androgen agonist. Despite this, in orchidectomized mature rats it is an effective SARM agonist, with an ED50 on levator ani muscle of 3.3mg/kg and an ED50 on ventral prostate of >30mg/kg. It has its maximal effect on muscle at the dose of 10mg/kg. In addition, this compound has mixed agonistic and antagonistic activities on prostate, reducing the weight of that tissue in intact rats by 22% at 10mg/kg. The compound does not have significant effect on gonadotropin levels or testosterone levels in both orchidectomized and intact male rats. It does not have notable progestin, estrogen or glucocorticoid agonistic or antagonistic activity in rats. In a female sexual behavior model, it improves the sexual desire of ovariectomized female rats for sexually mature intact males over nonsexually ovariectomized females. Overall, the imidazolopyrazole is a potent prostate-sparing candidate for development as a SARM agonist with an appropriate pharmacological profile for clinical benefit in muscle-wasting conditions and female sexual function disorders.

Structural basis for computational screening of non-steroidal androgen receptor ligands

Importance of the field: Deep structural and chemical understanding of the protein target and computational methods for detection of receptor-selective ligands are important for the early drug discovery in the steroid receptor field.Areas covered in this review: This review focuses on the use of currently available structural information of the androgen receptor (AR) and known AR ligands to make computational strategies for the discovery of AR ligands in order to offer new chemical platforms for drug development.What the reader will gain: AR is a challenging target for drug discovery and modeling even if there is a wealth of experimental data available. First, only the active structure of AR is currently known, which hampers the design of AR antagonists. Second, the structural similarity between the ligand-binding sites of AR and its mutated forms and closely related steroid receptors (SRs) such as progesterone receptors presents challenges for the development of drugs with receptor-selective function.Take home message: Research indicates that a very small chemical change in the structure of a non-steroidal ligand can cause a complete change in its activity. One source of this effect arises from binding to similar binding sites in related SRs and other proteins in the signaling pathway. Currently, computational methods are not able to predict the subtle differences between AR ligand activities but modeling does offer the possibility of generating new lead structures that might have the desired properties.

Pharmacokinetics, biodistribution and metabolism of a novel selective androgen receptor modulator designed for prostate cancer imaging

Knowledge of the presence and extent of disease plays a major role in clinical management of prostate cancer, as it provides meaningful information as to which therapy to choose and who might benefit from this therapy. The wide expression of androgen receptor (AR) in primary and metastatic prostate tumors offers a cellular target for receptor-mediated imaging of prostate cancer. In our previous study, a non-steroidal AR ligand, S-26 [S-3-(4-fluorophenoxy)-2-hydroxy-2-methyl-N-(4-cyano-3-iodophenyl)-propionamide] showed promising in vitro pharmacological properties as an AR-mediated imaging agent, with high AR binding affinity and AR specificity. The overall goal of this study was to characterize the in vivo metabolic and biodistribution profile of S-26 in rats. Non-compartmental pharmacokinetic analysis of S-26 in rat plasma showed that clearance (CL), volume of distribution (Vd(ss)), and half-life (T(1/2)) of S-26 were 0.30 + or - 0.07 l/h/kg, 1.44 + or - 0.33 l/kg, and 4 h, respectively, after intravenous (i.v.) administration. Dose proportionality (1, 10 and 30 mg/kg) studies suggested that the pharmacokinetics of S-26 are dose-independent. The plasma concentrations of all 3 doses were further simultaneously fitted with a two-compartmental model and the results were similar to those obtained from non-compartmental analysis. Biodistribution studies using (125)I-labeled S-26 indicated that it did not specifically target AR-rich tissue (e.g. prostate). A substantial amount of radioactivity recovered from thyroid gland indicated the release of free iodine. In metabolism studies, unchanged S-26 and its metabolites were detected in rat urine and fecal samples. Oxidation, de-iodination, hydrolysis, and sulfate conjugation were the major metabolic pathways of S-26 in rats, with de-iodination representing a unique metabolic pathway of S-26 among other selective androgen receptor modulators. In conclusion, the extensive plasma clearance and de-iodination of S-26 likely contribute to its lack of AR tissue selectivity in vivo. Future studies using metabolically stable ligands with less lipophilicity and higher AR binding affinity may represent a promising and rational approach for AR-mediated imaging.

Acidic heterocycles as novel hydrophilic pharmacophore of androgen receptor ligands with a carborane core structure

A novel series of androgen receptor (AR) ligands bearing an acidic heterocycle with hydrogen-bonding ability as the terminal polar group was developed. Since most non-steroidal AR ligands so far known are structurally limited to nitro- or cyanobenzanilide as the polar pharmacophore, development of alternative hydrogen-bonding components is required to obtain novel AR ligands. Various acidic heterocycles were introduced into a hydrophobic phenylcarborane (1-phenyl-1,12-dicarba- closo-dodecaborane) core structure to provide a moiety that could interact effectively with the critical basic arginine residue of the AR ligand binding domain. The most potent compounds, 1,2,4-oxadiazole-5-thione derivatives 21a and 21b, exhibited higher affinity for hAR than did the well-known anti-androgen hydroxyflutamide. The results suggest that this heterocyclic functionality is potential bioisoster of the nitro and cyano groups forming the polar pharmacophores of known non-steroidal AR ligands.

Targeted intracellular protein degradation induced by a small molecule: En route to chemical proteomics

We have developed a heterobifunctional all-small molecule PROTAC (PROteolysis TArgeting Chimera) capable of inducing proteasomal degradation of the androgen receptor. This cell permeable PROTAC consists of a non-steroidal androgen receptor ligand (SARM) and the MDM2 ligand known as nutlin, connected by a PEG-based linker. The SARM–nutlin PROTAC recruits the androgen receptor to MDM2, which functions as an E3 ubiquitin ligase. This leads to the ubiquitination of the androgen receptor, and its subsequent degradation by the proteasome. Upon treatment of HeLa cells with 10 μM PROTAC for 7 h, we were able to observe a decrease in androgen receptor levels. This degradation is proteasome dependent, as it is mitigated in cells pre-treated with 10 μM epoxomicin, a specific proteasome inhibitor. These results have implications for the potential study and treatment of various cancers with increased androgen receptor levels.

A selective androgen receptor modulator with minimal prostate hypertrophic activity restores lean body mass in aged orchidectomized male rats

Androgens are required for the maintenance of normal sexual activity in adulthood and for enhancing muscle growth and lean body mass in adolescents and adults. Androgen receptor (AR) ligands with tissue selectivity (selective androgen receptor modulators, or SARMs) have potential for treating muscle wasting, hypogonadism of aging, osteoporosis, female sexual dysfunction, and other indications. JNJ-37654032 is a nonsteroidal AR ligand with mixed agonist and antagonist activity in androgen-responsive cell-based assays. It is an orally active SARM with muscle selectivity in orchidectomized rat models. It stimulated growth of the levator ani muscle with ED 50 0.8 mg/kg, stimulating maximal growth at a dose of 3 mg/kg. In contrast, it stimulated ventral prostate growth to 21% of its full size at 3 mg/kg. At the same time, JNJ-37654032 reduced prostate weight in intact rats by 47% at 3 mg/kg, while having no inhibitory effect on muscle. Using magnetic resonance imaging to monitor body composition, JNJ-37654032 restored about 20% of the lean body mass lost following orchidectomy in aged rats. JNJ-37654032 reduced follicle-stimulating hormone levels in orchidectomized rats and reduced testis size in intact rats. JNJ-37654032 is a potent prostate-sparing SARM with the potential for clinical benefit in muscle-wasting diseases.

A selective androgen receptor modulator with minimal prostate hypertrophic activity enhances lean body mass in male rats and stimulates sexual behavior in female rats

Androgen receptor (AR) ligands with tissue selectivity (selective androgen receptor modulators, or SARMs) have potential for treating muscle wasting, hypogonadism of aging, osteoporosis, female sexual dysfunction, and other indications. JNJ-28330835 is a nonsteroidal AR ligand with mixed agonist and antagonist activity in androgen-responsive cell-based assays. It is an orally active SARM with muscle selectivity in orchidectomized rat models. It stimulated growth of the levator ani muscle, stimulating maximal growth at a dose of 10 mg/kg. At the same time, JNJ-28330835 reduced prostate weight in intact rats by a mean of 30% at 10 mg/kg, while having no inhibitory effect on muscle. Using magnetic resonance imaging (MRI) to monitor body composition, it prevented half of the loss of lean body mass associated with orchidectomy, and restored about 30% of lost lean mass to aged orchidectomized rats. It had agonist effects on markers of both osteoclast and osteoblast activity, suggesting that it reduces bone turnover. In a model of sexual behavior, JNJ-28330835 enhanced the preference of ovariectomized female rats for sexually intact male rats over nonsexual orchidectomized males. JNJ-28330835 is a prostate-sparing SARM with the potential for clinically beneficial effects in muscle-wasting diseases and sexual function disorders.

Pharmacokinetics and Pharmacodynamics of Nonsteroidal Androgen Receptor Ligands

Testosterone and structurally related anabolic steroids have been used to treat hypogonadism, muscle wasting, osteoporosis, male contraception, cancer cachexia, anemia, and hormone replacement therapy in aging men or age-related frailty; while antiandrogens may be useful for treatment of conditions like acne, alopecia (male-pattern baldness), hirsutism, benign prostatic hyperplasia (BPH) and prostate cancer. However, the undesirable physicochemical and pharmacokinetic properties of steroidal androgen receptor (AR) ligands limited their clinical use. Nonsteroidal AR ligands with improved pharmacological and pharmacokinetic properties have been developed to overcome these problems. This review focuses on the pharmacokinetics, metabolism, and pharmacology of clinically used and emerging nonsteroidal AR ligands, including antagonists, agonists, and selective androgen receptor modulators.

Preclinical Pharmacology of a Nonsteroidal Ligand for Androgen Receptor-Mediated Imaging of Prostate Cancer

Proper management of prostate cancer patients is highly dependent on the spread of the disease. High expression levels of the androgen receptor (AR) in prostate tumor offer a target for identifying cancer metastasis. We investigated the use of nonsteroidal AR ligands for receptor-mediated imaging as a diagnostic tool for prostate cancer staging. Compound S-26 [S-3-(4-fluorophenoxy)-2-hydroxy-2-methyl-N-(4-cyano-3-iodophenyl)-propionamide]was identified from a series of iodinated ether-linked derivatives of bicalutamide due to its high-AR binding affinity of 3.3 nM (which is similar to testosterone and approximately 25% of the binding affinity of dihydrotestosterone) in an in vitro competitive binding assay using rat prostate cytosol. Furthermore, S-26 exhibited a greater binding affinity (K(i) = 4.4 nM) in a whole-cell binding assay using COS-7 cells transfected with human AR than testosterone (K(i) = 32.9 nM) and dihydrotestosterone (K(i) = 45.4 nM). We also confirmed that sex hormone-binding globulin (SHBG), a plasma protein that binds steroids with high affinity, does not bind with S-26. Cotransfection studies with the estrogen, progesterone, and glucocorticoid receptor indicated that S-26 does not cross-react with other members of the steroid hormone receptor family. The nonsteroidal structure, high-AR binding affinity, specificity, and lack of binding to SHBG indicate that S-26 exhibits favorable properties for further development as an imaging agent for prostate cancer.

Chemistry and Structural Biology of Androgen Receptor

AbstractFor Abstract see ChemInform Abstract in Full Text.

Structural Basis for Accommodation of Nonsteroidal Ligands in the Androgen Receptor

The mechanism by which the androgen receptor (AR) distinguishes between agonist and antagonist ligands is poorly understood. AR antagonists are currently used to treat prostate cancer. However, mutations commonly develop in patients that convert these compounds to agonists. Recently, our laboratory discovered selective androgen receptor modulators, which structurally resemble the nonsteroidal AR antagonists bicalutamide and hydroxyflutamide but act as agonists for the androgen receptor in a tissue-selective manner. To investigate why subtle structural changes to both the ligand and the receptor (i.e. mutations) result in drastic changes in activity, we studied structure-activity relationships for nonsteroidal AR ligands through crystallography and site-directed mutagenesis, comparing bound conformations of R-bicalutamide, hydroxyflutamide, and two previously reported nonsteroidal androgens, S-1 and R-3. These studies provide the first crystallographic evidence of the mechanism by which nonsteroidal ligands interact with the wild type AR. We have shown that changes induced to the positions of Trp-741, Thr-877, and Met-895 allow for ligand accommodation within the AR binding pocket and that a water-mediated hydrogen bond to the backbone oxygen of Leu-873 and the ketone of hydroxyflutamide is present when bound to the T877A AR variant. Additionally, we demonstrated that R-bicalutamide stimulates transcriptional activation in AR harboring the M895T point mutation. As a whole, these studies provide critical new insight for receptor-based drug design of nonsteroidal AR agonists and antagonists.

Chemistry and structural biology of androgen receptor.

Androgen receptor (AR) is a member of the steroid and nuclear receptor superfamily,1 which is composed of over 100 members and continues to grow. Among this large family of proteins, only five vertebrate steroid receptors—estrogen, progesterone, androgen, glucocorticoid, and mineralocorticoid receptors—are known. Two subtypes of estrogen receptor have been identified, estrogen receptor α and estrogen receptor β.2 Like other steroid receptors, AR is a soluble protein that functions as an intracellular transcriptional factor. AR function is regulated by the binding of androgens, which initiates sequential conformational changes of the receptor that affect receptor–protein interactions and receptor–DNA interactions. AR-regulated gene expression is responsible for male sexual differentiation and male pubertal changes. AR ligands are widely used in a variety of clinical applications (i.e., agonists are employed for hypogonadism, while antagonists are used for prostate cancer therapy). Fang et al.3 recently summarized a large number of chemicals that bind to the AR. The current review focuses on well-characterized AR ligands that bind to the AR with high affinity and integrates discussion regarding the biology, metabolism, and structure-activity relationships for therapeutic and emerging classes of AR ligands. The known AR ligands can be classified as steroidal or nonsteroidal based on their structure or as agonist or antagonist based on their ability to activate or inhibit transcription of AR target genes. Synthetic AR ligands were first developed by modifying the steroidal structure of endogenous androgens. The structure–activity relationship of these steroidal AR ligands is well documented4-6 and will only be briefly summarized in this review. However, low oral bio-availability, poor pharmacokinetic properties, and side effects have limited the use of many steroidal AR ligands. Until recently, it was considered impossible to separate the androgenic and anabolic effects of AR ligands due to their reliance on a single AR. However, newly discovered nonsteroidal AR ligands may provide a new strategy to achieve tissue selectivity, as is possible with estrogen receptor ligands. Novel nonsteroidal pharmacophores are summarized in this review with discussion of the emerging structure–activity relationships and examples of their tissue selectivity included.7 1.1. Physiologic Roles and Clinical Application of Androgens AR is mainly expressed in androgen target tissues, such as the prostate, skeletal muscle, liver, and central nervous system (CNS), with the highest expression level observed in the prostate, adrenal gland, and epididymis as determined by real-time polymerase chain reaction (PCR).8 AR can be activated by the binding of endogenous androgens, including testosterone and 5α-dihydrotestosterone (5α-DHT). Physiologically, functional AR is responsible for male sexual differentiation in utero and for male pubertal changes. In adult males, androgen is mainly responsible for maintaining libido, spermato-genesis, muscle mass and strength, bone mineral density, and erythropoisis.7,9 The actions of androgen in the reproductive tissues, including prostate, seminal vesicle, testis, and accessory structures, are known as the androgenic effects, while the nitrogen-retaining effects of androgen in muscle and bone are known as the anabolic effects. Numerous and varied site mutations in AR have been identified (The Androgen Receptor Gene Mutations Database World Wide Web Server, http://www.androgendb.mcgill.ca/). The majority of these mutations are associated with diseases, like Androgen Insensitivity Syndrome and prostate cancer. The androgen withdrawal syndrome observed in prostate cancer therapy also appeared to be related to certain AR mutations, such as T877A and W741C mutations, which convert some AR antagonists into agonists (see more discussion in section 3.1.1). Besides the site mutations documented, AR gene polymorphism has also been identified, particularly, the poly-Q (CAG)n at exon I. The polymorphic (CAG)10–35 triplet repeat sequence, starting from codon 58, codes for polyglutamine. The length of the repeat is inversely correlated with the transactivation activity of AR. The correlation between the length of the CAG repeat and disease stage was recently reviewed by Oettel.10 Classically, testosterone is used to treat male hypogonadism, Klinefelter's syndrome, anemia secondary to chronic renal failure, aplastic anemia, protein wasting diseases associated with cancer, burns, traumas,acquiredimmunodeficiencysyndrome(AIDS), etc., short stature, breast cancer (as an anti-estrogen), and hereditary angioedema.7 Recently, hormone replacement therapy in aging males has also been proposed to improve body composition, bone and cartilage metabolism, and certain domains of brain function and even decrease cardiovascular risk.10

Pharmacology, pharmacokinetics, and metabolism of acetothiolutamide, a novel nonsteroidal agonist for the androgen receptor.

The present study characterized the in vitro androgen receptor (AR) binding affinity, in vitro and in vivo pharmacological activity, and in vivo pharmacokinetics and metabolism of acetothiolutamide, a nonsteroidal AR ligand. AR binding was determined by a competitive binding assay. In vitro AR agonist activity was examined by a cotransfection assay. Acetothiolutamide displayed high AR binding affinity (K(i) = 4.9 +/- 0.2 nM) and full agonist activity in the in vitro studies. Next, the androgenic, anabolic, and antiandrogenic activity of acetothiolutamide was evaluated in a castrated immature rat model. In this animal model, acetothiolutamide exhibited an overall negligible androgenic effect, but a statistically significant anabolic effect at high subcutaneous doses. Also, acetothiolutamide demonstrated a noticeable antiandrogenic effect in castrated rats supplemented with testosterone propionate. To understand the causes for the observed disparity between in vitro and in vivo activities, pharmacokinetics and metabolism of acetothiolutamide were studied in male Sprague-Dawley rats. Acetothiolutamide was rapidly cleared from rat plasma (clearance of about 45 ml/min/kg) in a concentration-independent manner after i.v. dosing. Acetothiolutamide was completely absorbed after subcutaneous administration, but not bioavailable after oral dose. In the metabolism study, the unchanged molecule and its metabolites in urine and fecal samples were detected by high-performance liquid chromatography-mass spectrometry. The structures of major metabolites were elucidated with liquid chromatography-tandem mass spectrometry. After i.v. administration, acetothiolutamide was excreted in urine and feces as unchanged drug and a variety of metabolites. Oxidation, hydrolysis, and sulfate conjugation of phase I metabolites were the major metabolic pathways of acetothiolutamide in rats. Overall, the high plasma clearance of acetothiolutamide, due to its extensive hepatic metabolism, likely contributed to its lack of androgenic activity in vivo.

Development of radioiodinated nonsteroidal androgen receptor ligands for spect imaging of prostate cancer

The appropriate treatment strategy for prostate cancer is critically dependent on its accurate staging (1). Current screening techniques (CT, MRI, Ultrasound) fail to reliably distinguish clinically-localized disease from metastatic disease. A reliable noninvasive method for detection of prostate cancer metastases would thus be of immense clinical benefit for a) disease staging b) implementing the appropriate treatment strategy c) monitoring the effects of therapy. To address this need, many research groups have focused on the development of radiolabeled androgen receptor (AR) ligands for prostate cancer imaging, based on the observation that most prostate tumors and metastases express AR (2,3). The majority of these studies to date have focused on steroid-based ligands (2,4,5). The antiandrogens RU 59063 and RU 58841 (Table l), are prototypes of a new series of nonsteroidal androgen receptor ligands that display high AR affinity and selectivity (6,7). The ease of synthesis and structural modification of these compounds as compared to steroid-based AR ligands, prompted us to select them as leads for development of a SPECT AR radioligand. We have previously shown that substitution of the trifluoromethyl group of RU 59063 with iodine leads to an improvement in AR binding affinity (8). Accordingly, a series of iodinated analogs of RU 59063 and RU 58841 was synthesized for investigation as in vivo AR radioligands (Table 1). Compounds 1-4 were synthesized from 4-cyano-3-iodoaniline using previously reported methods (8). Radioiodination of compounds 1-4 with iodine-125 were achieved in 50-65% radiochemical yield by an ammonium sulfate catalyzed solid phase exchange procedure (Scheme 1). Radiolabeled products were purified either by elution through an anion exchange resin or

Synthesis of (E)‐4‐[4,4‐dimethyl‐2,5‐dioxo‐3‐{1′‐(125I)iodo‐1′‐propen‐3′‐yl}‐1‐imidazolidinyl]‐2‐trifluoromethylbenzonitrile: A potential radioligand for the androgen receptor

AbstractThe synthesis of a novel radioiodinated nonsteroidal androgen receptor ligand (E)‐4‐[4,4‐dimethyl‐2,5dioxo‐3‐{1′‐(125I)iodo‐1′‐propen‐3′‐yl}‐1‐imidazolidinyl]‐2‐trifluoromethylbenzonitrile ([125I]1) is described. In vitro competitive binding studies demonstrated that 1 bound to the rat androgen receptor with high affinity (Ki = 13 nM). No‐carrier‐added [125I]1 was synthesized from the corresponding tri‐n‐butyltin precursor by an oxidative radioiododestannylation reaction with Na[125I]iodide and 3% aqueous hydrogen peroxide as oxidant. Subsequent HPLC purification provided [125I]1 in 86‐92% (average = 90%;n = 5) isolated radiochemical yields having >99% radiochemical and chemical purity and a specific activity range of 1574‐1835 Ci/mmol (average = 1733Ci/mmol; n = 3). Copyright © 2001 John Wiley & Sons, Ltd.

ChemInform Abstract: Design, Synthesis, and Pharmacological Characterization of 4-[4,4-Dimethyl-3-(4-hydroxybutyl)-5-oxo-2-thioxo-1-imidazolidinyl] -2-iodobenzonitrile as a High-Affinity Nonsteroidal Androgen Receptor Ligand.

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Design, Synthesis, and Pharmacological Characterization of 4-[4,4-Dimethyl-3-(4-hydroxybutyl)-5-oxo-2-thioxo-1-imidazolidinyl]- 2-iodobenzonitrile as a High-Affinity Nonsteroidal Androgen Receptor Ligand

4-[4, 4-Dimethyl-3-(4-hydroxybutyl)-5-oxo-2-thioxo-1-imidazolidinyl]-2-+ ++trif luoromethylbenzonitrile (RU 59063) is a prototype of a new class of high-affinity nonsteroidal androgen receptor (AR) ligands. The search for a radioiodinated AR ligand prompted us to synthesize 4-[4, 4-dimethyl-3-(4-hydroxybutyl)-5-oxo-2-thioxo-1-imidazolidinyl]-2-i odo benzonitrile (DTIB) wherein the trifluoromethyl group of RU 59063 was substituted with the similarly hydrophobic iodine atom. DTIB displayed subnanomolar binding affinity (K(i) = 0.71 +/- 0.22 nM) for the rat AR in competitive binding assays. Additionally, DTIB demonstrated potent agonist activity, comparable to that of the natural androgen 5alpha-dihydrotestosterone (DHT), in a cell-based functional assay (cotransfection assay). DTIB represents a new lead for the development of high-affinity radioiodinated AR radioligands.