Discovery of the Selective Androgen Receptor Modulator MK-0773 Using a Rational Development Strategy Based on Differential Transcriptional Requirements for Androgenic Anabolism Versus Reproductive Physiology

The androgen receptor (AR) is a member of the nuclear receptor (NR) superfamily of ligand-dependent transactivation factors. Androgens such as testosterone and 5-a-dihydrotestosterone (DHT) act as agonists of AR. AR mediates various biological effects such as the development of male reproductive tissues, sexual development, and spermatogenesis. [1][2][3][4] Since androgen declining with age contributes to age-related bone and muscle loss and increase in fat mass, 5) the anabolic effect of androgen is attractive for the maintenance of health. Furthermore, it is known that AR is involved in androgen-dependent prostate cancer growth. Thus, antagonists of AR (flutamide, bicalutamide, and nilutamide) are used in anti-androgen therapy for prostate cancer. 8,9) AR mediates the expression of androgen-regulated genes, as represented by prostate specific antigen (PSA) [10][11][12] and FK506-binding protein 51 (FKBP51). [13][14][15] In the absence of a ligand, AR is localized in the cytoplasm, where it forms complexes with chaperones. Upon ligand binding, AR translocates into the nucleus. Following nuclear translocation, AR binds to androgen responsive elements (ARE) in the promoter regions of its target genes as a homodimer. Generally, the transcriptional activity of nuclear receptors is modulated by their interaction with cofactors such as coactivators and corepressors. [16][17][18][19] The type of ligand that binds to the receptor determines which type of cofactor is chosen. In the case of agonists, AR interacts with coactivators dominantly over corepressors, and vice versa in the case of antagonists.Unlike other nuclear receptors, AR AF2 demonstrates weak transcriptional activity. However, ligand-dependent interaction between NTD and LBD/AF2 (which is termed as the N/C interaction) endows AR with synergistic transactivation potential. [20][21][22][23] Thus, the N/C interaction is important for the ligand-dependent transactivation potential of AR.Synthetic AR ligands are useful for treatment of prostate cancer and age-related diseases such as osteopenia and sarcopenia. Previously, we prepared novel synthetic steroids.24) In our preliminary screening for novel AR ligands, a steroid compound, (17a,20E)-17,20-[(1-methoxyethylidene) bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl ester (YK11), behaved apparently as a partial agonist of AR in an ARE-luciferase reporter assay (unpublished data). We were interested in this partial agonistic nature of YK11. In this report, we will show that YK11 blocks the N/C-interaction required for the full-agonistic function of wild-type AR, inducing selective AR-target genes owing to the constitutive transactivation potential of AF-1 subdomain in endogenous AR-expressing MDA-MB 453 cells. MATERIALS AND METHODS ChemicalsThe compounds tested in our preliminary screening for novel AR ligands were prepared by previously

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

(17.ALPHA.,20E)-17,20-[(1-Methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic Acid Methyl Ester (YK11) Is a Partial Agonist of the Androgen Receptor

Kanno

Hikosaka

Zhang

et al. 2011

“…It has been reported that the tissue selectivity of the SARMs MK-0773 and 2-FPA are inversely correlated with the recruitment of the cofactor TIF-2. 22) In this report, we studied the tissue-selective mechanism of S-101479. Firstly, we demonstrated the direct effects of S-101479 on osteoblast differentiation by using MC3T3-E1 cells, a preosteoblastic cell line established from the calvaria of neonatal mice.…”

mentioning

confidence: 99%

Mechanism of the Tissue-Specific Action of the Selective Androgen Receptor Modulator S-101479

Furuya

Yamamoto

Ohyabu

et al. 2013

Selective androgen receptor modulators (SARMs) comprise a new class of molecules that induce anabolic effects with fewer side effects than those of other anabolic agents. We previously reported that the novel SARM S-101479 had a tissue-selective bone anabolic effect with diminished side effects in female animals. However, the mechanism of its tissue selectivity is not well known. In this report, we show that S-101479 increased alkaline phosphatase activity and androgen receptor (AR) transcriptional activity in osteoblastic cell lines in the same manner as the natural androgen ligand dihydrotestosterone (DHT); conversely, stimulation of AR dimerization was very low compared with that of DHT (34.4%). S-101479 increased bone mineral content in ovariectomized rats without promoting endometrial proliferation. Yeast two-hybrid interaction assays revealed that DHT promoted recruitment of numerous cofactors to AR such as TIF2, SRC1, β-catenin, NCoA3, gelsolin and PROX1 in a dose-dependent manner. SARMs induced recruitment of fewer cofactors than DHT; in particular, S-101479 failed to induce recruitment of canonical p160 coactivators such as SRC1, TIF2 and notably NCoA3 but only stimulated binding of AR to gelsolin and PROX1. The results suggest that a full capability of the AR to dimerize and to effectively and unselectively recruit all canonical cofactors is not a prerequisite for transcriptional activity in osteoblastic cells and resulting anabolic effects in bone tissues. Instead, few relevant cofactors might be sufficient to promote AR activity in these tissues.

“…[13][14][15][16]22,[29][30][31] The reduced virilizing effect that was evaluated by the effect on the prostate is not sufficient to enable treatment for women who require diminished anabolic effects on the uterus. Recently, Merck Research Laboratories demonstrated the effects of bone-selective SARMs in a female animal model 32,33) ; different tissue selectivities are needed to develop postmenopausal osteoporosis drugs. The physiology of the uterus is regulated by estrogens.…”

Section: Discussionmentioning

confidence: 99%

The Novel Non-steroidal Selective Androgen Receptor Modulator S-101479 Has Additive Effects with Bisphosphonate, Selective Estrogen Receptor Modulator, and Parathyroid Hormone on the Bones of Osteoporotic Female Rats

Furuya

Yamamoto

Ohyabu

et al. 2012

We have studied non-steroidal selective androgen receptor modulators (SARMs) to develop anti-osteoporosis drugs for males and females. Many SARMs have been studied for their anabolic effects on bone or muscle with reduced virilizing effects in male animals. However, the tissue selectivities of these agents in female animals have not been fully evaluated. We evaluated the novel SARM S-101479 from tetrahydroquinoline libraries in ovariectomized (OVX) rats. S-101479 preferentially bound to the androgen receptor with nanomolar affinity among nuclear receptors. It increased the bone mineral density (BMD) of femurs and diminished the effects on the uterus and clitoral gland in OVX rats. We then compared the effect of S-101479 on bone with those of commercial anti-osteoporosis drugs such as alendronate, raloxifene, and teriparatide. Furthermore, we evaluated the effects of combination treatments with these agents in OVX rats. After 16-week treatment, all agents significantly increased BMD, but the magnitude of bone mineral content (BMC) and/or bone size (projected bone area) were different. Alendronate, raloxifene, and teriparatide maintained BMC and bone size in this experimental dose. Only S-101479 increased BMC with bone size on single treatments. In combination treatment, S-101479 significantly increased BMC and bone size compared with single treatments of other agents. S-101479, like natural androgen, may have showed periosteal bone formation of the cortical area and indicated additive effects with commercial anti-osteoporosis drugs. These results indicate that S-101479 may be a useful anti-osteoporosis drug, particularly for patients with established severe osteoporosis.Key words selective androgen receptor modulator; bone anabolic; additive effect Androgens are known to have beneficial anabolic effects on various tissues such as bone, muscle, and red blood cells (RBCs).1-4) However, the clinical use of androgens has been limited because of their undesirable virilizing and metabolic actions. Their effect on the prostate gland is an extremely serious side effect because the risk of prostate cancer or benign prostate hyperplasia may increase. 5,6) The side effects of androgens are not lethal in women, but many virilizing effects (e.g., hirsutism, voice change, and acne) have been observed. 7,8) Anabolic steroids were developed to reduce the side effects of androgens and treat osteoporosis. However, their actions were not sufficient to reduce virilizing effects, and they exhibited hepatotoxic actions. [9][10][11][12] Recently, the actions of non-steroidal selective androgen receptor modulators (SARMs) have been investigated in many laboratories. [13][14][15][16][17] Typically, they were observed to be more tissue-selective than anabolic steroids and were orally available in preclinical models. We have focused on bone anabolic SARMs to develop anti-osteoporosis agents without serious virilizing effects.