Potent novel nonsteroidal androgen antagonists with a phthalimide skeleton

Dehydrogenative 6π heterocyclization under visible light irradiation and mechanistic insights

A visible-light-driven oxidative 6π heterocyclization for the synthesis of structurally diverse π-conjugated polycyclic 1-aminoisoquinolines has been developed. DFT calculations demonstrated that deprotonation is the rate-determining step.

Histone deacetylase inhibitors (HDACIs). Structure--activity relationships: history and new QSAR perspectives

Histone deacetylase (HDAC) inhibition is a recent, clinically validated therapeutic strategy for cancer treatment. HDAC inhibitors (HDACIs) block angiogenesis, arrest cell growth, and lead to differentiation and apoptosis in tumor cells. In this article, a survey of published quantitative structure-activity relationships (QSARs) studies are presented and discussed in the hope of identifying the structural determinants for anticancer activity. Secondly a two-dimensional QSAR study was carried out on biological results derived from various types of HDACIs and from different assays using the C-QSAR program of Biobyte. The QSAR analysis presented here is an attempt to organize the knowledge on the HDACIs with the purpose of designing new chemical entities with enhanced inhibitory potencies and to study the mechanism of action of the compounds. This study revealed that lipophilicity is one of the most important determinants of activity. Additionally, steric factors such as the overall molar refractivity (CMR), molar volume (MgVol), the substituent's molar refractivity (MR) (linear or parabola), or the sterimol parameters B(1) and L are important. Electronic parameters indicated as σ(p), are found to be present only in one case.

Design, synthesis, and evaluation of isoindolinone-hydroxamic acid derivatives as histone deacetylase (HDAC) inhibitors

We designed and synthesized hydroxamic acid derivatives bearing a 4-(3-pyridyl)phenyl group as a cap structure, and found that they exhibit potent histone deacetylase (HDAC) inhibitory activity. A representative compound, 17a, showed more potent growth-inhibitory activity against pancreatic cancer cells and greater upregulation of p21(WAF1/CIP1) expression than the clinically used HDAC inhibitor suberoylanilide hydroxamic acid (Zolinza).

Structural development studies of nuclear receptor ligands

Studies in our laboratory are focused on structural development studies of biological response modifiers (BRMs), including nuclear receptor (NR) ligands, which act directly on cells at the gene expression level, and thalidomide (and related molecules), which modulates a variety of physiological processes. Our studies on the molecular design of ligands for retinoic acid receptor (RAR), androgen receptor (AR), vitamin D receptor (VDR), farnesoid X receptor (FXR), and peroxisome proliferator-activated receptor (PPAR) are reviewed.

Design, synthesis, and evaluation of cyclic amide/imide-bearing hydroxamic acid derivatives as class-selective histone deacetylase (HDAC) inhibitors

A series of hydroxamic acid derivatives bearing a cyclic amide/imide group as a linker and/or cap structure, prepared during our structural development studies based on thalidomide, showed class-selective potent histone deacetylase (HDAC)-inhibitory activity. Structure-activity relationship studies indicated that the steric character of the substituent introduced at the cyclic amide/imide nitrogen atom, the presence of the amide/imide carbonyl group, the hydroxamic acid structure, the shape of the linking group, and the distance between the zinc-binding hydroxamic acid group and the cap structure are all important for HDAC-inhibitory activity and class selectivity. A representative compound (30w) showed potent p21 promoter activity, comparable with that of trichostatin A (TSA), and its cytostatic activity against cells of the human prostate cell line LNCaP was more potent than that of the well-known HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA).

Tubulin polymerization inhibitors with a fluorinated phthalimide skeleton derived from thalidomide

4,7-Difluoro-2-(2,6-diisopropylphenyl)-1H-isoindole-1,3-dione [4,7FPP-33 (14)] has a potent tubulin-polymerization-inhibiting activity comparable with those of the known tubulin-polymerization inhibitors rhizoxin and colchicine. The structure-activity relationship for fluorine substitution was elucidated.

(+)-(2R,5S)-4-[4-Cyano-3-(trifluoromethyl)phenyl]-2,5-dimethyl-N-[6-(trifluoromethyl)pyridin-3- yl]piperazine-1-carboxamide (YM580) as an Orally Potent and Peripherally Selective Nonsteroidal Androgen Receptor Antagonist

A novel series of trans-N-aryl-2,5-dimethylpiperazine-1-carboxamide derivatives was synthesized and their androgen receptor (AR) antagonist activities and in vivo antiandrogenic effects were evaluated. Pharmacological assays indicated that compound 33 was a potent AR antagonist, and subsequent optical resolution provided (+)-(2R,5S)-4-[4-cyano-3-(trifluoromethyl)phenyl]-2,5-dimethyl-N-[6-(trifluoromethyl)pyridin-3-yl]piperazine-1-carboxamide (33a, YM580) which exhibited the most potent antiandrogenic activity. Unlike bicalutamide, compound 33a decreased the weight of rat ventral prostate in a dose-dependent manner (ED(50) = 2.2 mg/kg/day), and induced the maximum antiandrogenic effect, comparable to that of surgical castration, without significantly affecting serum testosterone levels. Compound 33a is a promising clinical candidate for prostate cancer monotherapy.

Angiogenesis inhibitors derived from thalidomide

5-Hydroxy-2-(2,6-diisopropylphenyl)-1H-isoindole-1,3-dione (5HPP-33: 10), which was obtained during our previous structural development studies on thalidomide, was revealed to possess potent anti-angiogenic activity in a human umbilical vein endothelial cell (HUVEC) assay. Thalidomide (1) and its metabolite, 5-hydroxythalidomide (5-HT: 2), which possesses a hydroxyl group at the position corresponding to that of 5HPP-33, as well as IMiDs (immunomodulatory derivatives of thalidomide: 3 and 5), also showed weak or moderate activity in the same assay.

Design and synthesis of phthalimide-type histone deacetylase inhibitors

Several hydroxamic acid derivatives with a substituted phthalimide group as a linker and/or cap structure, prepared during structural development studies based on thalidomide, were found to have histone deacetylase (HDAC)-inhibitory activity. Structure-activity relationship studies indicated that nature of the substituent introduced at the phthalimide nitrogen atom, introduction of a hydroxamic acid structure, and distance between the N-hydroxyl group and the cap structure are important for HDAC-inhibitory activity.

Design and synthesis of subtype-selective cyclooxygenase (COX) inhibitors derived from thalidomide

A series of substituted indoline and indole derivatives with cyclooxygenase (COX)-inhibitory activity was prepared during our structural development studies based on thalidomide as a multi-template lead compound. Structure-activity relationship studies indicated that the nature of the substituent introduced at the benzene ring of the indoline (indole) backbone, and the length and type of the linking group between the nitrogen atom of indoline (indole) and the N-substituent are important for the activity. This study has led to the identification of COX-1-selective inhibitors, and these should be useful not only as pharmacological tools to investigate the physiology and pathophysiology of COX, but also as sophisticated leads for the development of novel drugs to treat COX-associated diseases, such as inflammatory diseases, and cancer.

Tubulin-polymerization inhibitors derived from thalidomide

2-(2,6-Diisopropylphenyl)-5-hydroxy-1H-isoindole-1,3-dione (5HPP-33), which was obtained during our previous structural development studies on thalidomide, was revealed to possess potent tubulin-polymerization-inhibiting activity, comparable to that of the known tubulin-polymerization inhibitors, rhizoxin and colchicine. A major metabolite of thalidomide, 5-hydroxythalidomide, which possesses a hydroxyl group at the position corresponding to that of 5HPP-33, also showed moderate inhibitory activity.

N-Arylpiperazine-1-carboxamide Derivatives: a Novel Series of Orally Active Nonsteroidal Androgen Receptor Antagonists

A novel series of N-arylpiperazine-1-carboxamide derivatives was synthesized and their androgen receptor (AR) antagonist activities and in vivo antiandrogenic properties were evaluated. Reporter assays indicated that trans-2,5-dimethylpiperazine derivatives are potent AR antagonists, and in this series trans-N-4-[4-cyano-3-(trifluoromethyl)phenyl]-N-(2,4-difluorophenyl)-2,5-dimethylpiperazine-1-carboxamide (18 g, YM-175735) exhibited the most potent antiandrogenic activity. Compared to bicalutamide, YM-175735 is an approximately 4-fold stronger AR antagonist and has slightly increased antiandrogenic activity, suggesting that YM-175735 may be useful in the treatment of prostate cancer.

Phenylhomophthalimide-type NOS inhibitors derived from thalidomide

Thalidomide shows moderate inhibitory activity toward neuronal nitric oxide synthase (nNOS) and inducible NOS (iNOS), but not toward endothelial NOS (eNOS). Structural development studies of thalidomide yielded novel phenylhomophthalimide-type NOS inhibitors with enhanced activity and different subtype selectivity.

Specific nonpeptide inhibitors of puromycin-sensitive aminopeptidase with a 2,4(1H,3H)-quinazolinedione skeleton

Potent, specific, chemically stable and non-peptide/small-molecular inhibitors of puromycin-sensitive aminopeptidase, such as 3-(2,6-diethylphenyl)-2,4(1H,3H)-quinazolinedione (PAQ-22, 5), were prepared by the structural development of a potent PSA inhibitor, 2-(2,6-diethylphenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione (PIQ-22, 4). The design was carried out partly by applying electrostatic potential field information obtained from PIQ-22 (4) and its derivatives based on thalidomide (2). This information revealed that a positive electrostatic potential field around the benzylic methylene in the tetrahydroisoquinoline ring is necessary for potent activity. Lineweaver-Burk plot analysis showed that PAQ-22 (5) and its derivatives inhibit puromycin-sensitive aminopeptidase (PSA) in a non-competitive manner. These potent and specific PSA inhibitors showed dose-dependent cell invasion-inhibitory activity in a Matrigel assay using mouse melanoma B16F10/L5 cells, in spite of their low cell toxicity.

Synthesis and anticonvulsant evaluation ofN-substituted-isoindolinedione derivatives

A series of N-substituted-1,3-isoindolinedione derivatives (2-16) were synthesized for the purpose of defining the effect of N-substitution on the anticonvulsant activity of these derivatives. The target compounds (2-16) were obtained by condensation of phthalic anhydride with the corresponding amine derivative. The structures of the synthesized derivatives (2-16) were confirmed by means of IR, 1H-NMR, 13C-NMR, MS and elemental analyses. The anticonvulsant activity of all compounds (2-16) were evaluated by subcutaneous pentylenetetrazole seizure threshold test at doses of 0.2, 0.4 and 0.8 mmol/kg compared with sodium valproate as a positive control. Their neurotoxicity were determined by the rotorod test. Many of the present series of compounds showed good anticonvulsant activity at the tested doses, as compared to sodium valproate. Three of them (4, 6 and 11) exhibited 100% protection against convulsions, neurotoxicity and death at all tested doses. Out of the series, two compounds (12 and 13) were completely inactive with 100% mortality. 3-(p-chlorophenyl)-4-(1,3-dioxo-2,3-dihydro-1H-2-isoindolyl)butanoic acid derivative (11) has emerged as the most active compound which is 20 times more active than valproate with ED50 8.7, 169 mg/kg; TD50 413, 406 mg/kg and PI 47.5, 2.4. The results revealed the importance of the combination of baclofenic and phthalimide moieties (compound 11) as a promising anticonvulsant candidate.

Synthesis and Pharmacological Evaluation of Novel Arylpiperazine Derivatives as Nonsteroidal Androgen Receptor Antagonists

The search for novel antiandrogens by high-throughput screening (HTS) of the Yamanouchi chemical library led to the discovery of the lead compound (5), which possesses an arylmorpholine moiety. Through the optimization of the lead compound (5), we have found a series of novel arylpiperazine derivatives. Among them, 4-[4-cyano-(3-trifluoromethyl)phenyl]-N-(4-fluorophenyl)piperazine-1-carboxamide (22; YM-92088) exhibited a potent AR antagonistic activity with an IC(50) value of 0.47 microM in the reporter assay, which is more potent than bicalutamide (4) which has an IC(50) value of 0.89 microM.

Thalidomide as a Nitric Oxide Synthase Inhibitor and Its Structural Development

Thalidomide has been found to exhibit weak nitric oxide synthase (NOS)-inhibitory activity. Structural development studies of thalidomide showed that some N-2,6-dimethylphenylhomophthalimide analogs possess NOS-inhibiting activity.

Thalidomide analogues demonstrate dual inhibition of both angiogenesis and prostate cancer

The identification of agents with antiproliferative activity against endothelial cells has significant value for the treatment of many angiogenesis-dependent pathologies. Herein, we describe the discovery of a series of thalidomide analogues possessing inhibitory effects against both endothelial and prostate cancer cells. More specifically, several analogues exhibited low micromolar to mid-nanomolar potency in the inhibition of human microvascular endothelial cell (HMEC) proliferation, both in the presence and absence of vascular endothelial growth factor (VEGF), with the tetrafluorophthalimido class of compounds demonstrating the greatest potency. Additionally, all the compounds were screened against two different androgen independent prostate cancer cell lines (PC-3 and DU-145). Again, the tetrafluorophthalimido analogues exhibited the greatest effect with GI(50) values in the low micromolar range. Thalidomide was found to demonstrate selective inhibition of androgen receptor positive LNCaP prostate cancer cells. Furthermore, we showed that, as an example, tetrafluorophthalimido analogue 19 was able to completely inhibit the prostate specific antigen (PSA) secretion by the LNCaP cell line, while thalidomide demonstrated a 70% inhibition. We have also demonstrated that a correlation exists between HMEC and prostate cancer cell proliferation for this structural class. Altogether, our study suggests that these analogues may serve as promising leads for the development of agents that target both androgen dependent and independent prostate cancer and blood vessel growth.

N-Phenylphthalimide-Type Cyclooxygenase (COX) Inhibitors Derived from Thalidomide: Substituent Effects on Subtype Selectivity

Several N-substituted phenylphthalimide and phenylhomophthalimide derivatives with cyclooxygenase (COX)-inhibitory activity were prepared during structural development studies based on thalidomide as a lead compound. Substituent effects on the subtype selectivity were investigated.

Therapeutic androgen receptor ligands

In the past several years, the concept of tissue-selective nuclear receptor ligands has emerged. This concept has come to fruition with estrogens, with the successful marketing of drugs such as raloxifene. The discovery of raloxifene and other selective estrogen receptor modulators (SERMs) has raised the possibility of generating selective compounds for other pathways, including androgens (that is, selective androgen receptor modulators, or SARMs).

Cyclooxygenase inhibitors derived from thalidomide

Several N-3,5-dimethylphenylphthalimide analogs possessing more potent cyclooxygenase-inhibiting activity than that of aspirin were prepared during structural development studies based on thalidomide. Substituent effects on the activity were investigated.

Anti-androgens with full antagonistic activity toward human prostate tumor LNCaP cells with mutated androgen receptor

Anti-androgens were designed based on the principle of inhibiting the folding of helix 12 of the nuclear androgen receptor. The prepared anti-androgens exhibited full antagonistic activity toward human prostate tumor LNCaP cells with T877A point-mutated nuclear androgen receptor, as far as examined, towards which other known anti-androgens, including hydroxyflutamide, are inactive or act as androgen agonists.

Novel non-steroidal/non-anilide type androgen antagonists with an isoxazolone moiety

3-Substituted (Z)-4-(4-N,N-dialkylaminophenylmethylene)-5(4H)-isoxazolones and related compounds were designed and prepared as candidates for structurally novel androgen antagonists. Several compounds showed potent anti-androgenic activity as assessed by nuclear androgen receptor binding assay and growth inhibition assay using androgen-dependent Shionogi carcinoma cells SC-3. They were approximately 10--220 times more potent than flutamide in these assay systems. They also showed anti-androgenic activity toward prostate tumor cell line LNCaP, which has an aberrant nuclear androgen receptor.

Thalidomide and its analogues as cyclooxygenase inhibitors

Thalidomide showed cyclooxygenase (COX)-1/2 inhibitory activity with a potency comparable to that of aspirin. Structural development studies of thalidomide resulted in potent COX-1/2 inhibitors, and COX-1-selective and COX-2-selective inhibitors.

Structural development of biological response modifiers based on thalidomide

Thalidomide (N-alpha-phthalimidoglutarimide) is a teratogenic hypnotic/sedative agent which was used widely in the late 1950s and the early 1960s. In spite of its withdrawal from the market because of its severe teratogenicity, there has been a resurgence of interest in the drug in recent years due to its potential usefulness for the treatment of various diseases, including acquired immunodeficiency syndrome (AIDS) and various cancers. It has been revealed that thalidomide elicits pleiotropic effects and is a multi-target drug. Our structural development studies of thalidomide, focusing on tumor necrosis factor-alpha(TNF-alpha) production-regulating activity, anti-androgenic activity, puromycin-sensitive aminopeptidase-inhibiting activity, alpha-glucosidase-inhibiting activity, and inhibitory activities toward some other enzymes, are reviewed in relation to the pharmacological effects of thalidomide.

Thymidine phosphorylase inhibitors with a homophthalimide skeleton

Several N-phenylhomophthalimide derivatives were prepared and their inhibitory activity on thymidine phosphorylase/ platelet-derived endothelial cell growth factor (TP/PD-ECGF) was assessed. Among them, 2-(2,6-diethylphenyl)-7-nitro-1,2,3,4-tetrahydroisoquinoline-1,3-dione (9) was found to be a more potent inhibitor than the classical inhibitor, 5-nitrouracil (1). Lineweaver-Burk plot analysis indicated that 9 shows mixed-type competitive inhibition of TP/PD-ECGF, while 1 is a competitive inhibitor.

Novel small molecule nonpeptide aminopeptidase n inhibitors with a cyclic imide skeleton

A novel series of small molecule nonpeptide aminopeptidase N (APN) inhibitors with a N-phenylphthalimide or N-phenylhomophthalimide skeleton were prepared. Evaluation of their protease inhibitory activities revealed that (i) some N-phenylphthalimide analogs are potent APN inhibitors, but they are also inhibitors of another protease, dipeptidylpeptidase IV (DPP-IV), and (ii) some N-phenylhomophthalimide analogs, including 2-(2,6-diethylphenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione (PIQ-22), are potent and specific inhibitors of APN without DPP-IV-inhibitory activity. The structure-activity relationship studies of N-phenylphthalimides and N-phenylhomophthalimides are reviewed. PIQ-22 showed potent tumor-cell invasion-inhibitory activity.