Synthesis of 4(5)-phenylimidazole-based analogues of sphingosine-1-phosphate and FTY720: discovery of potent S1P1 receptor agonists

The novel immunosuppressant FTY720 has been demonstrated to elicit immunomodulating effects via interaction with the G-protein coupled receptor S1P(1). FTY720 induced agonism at the S1P(3) receptor, however, has been shown to result in mild bradycardia, a minor side-effect of initial FTY720 therapy. This report describes the synthesis of several potent 4(5)-phenylimidazole-based S1P(1) receptor agonists that are accompanied by poor agonist activity at S1P(3). For instance, compound 20 displayed an EC(50)=4.7+/-1.3 nM at the S1P(1) receptor and EC(50)=780+/-1.3 nM at the S1P(3) receptor using a [gamma-(35)S]GTP-binding assay as compared to phospho-FTY720 (S1P(1): EC(50)=1.3+/-1.3nM, S1P(3): EC(50)=2.0+/-2.4 nM).     

C(4)-alkyl substituted furanyl cyclobutenediones as potent, orally bioavailable CXCR2 and CXCR1 receptor antagonists

A novel series of cyclobutenedione centered C(4)-alkyl substituted furanyl analogs was developed as potent CXCR2 and CXCR1 antagonists. Compound 16 exhibits potent inhibitory activities against IL-8 binding to the receptors (CXCR2 Ki=1 nM, IC(50)=1.3 nM; CXCR1 Ki=3 nM, IC(50)=7.3 nM), and demonstrates potent inhibition against both Gro-alpha and IL-8 induced hPMN migration (chemotaxis: CXCR2 IC(50)=0.5 nM, CXCR1 IC(50)=37 nM). In addition, 16 has shown good oral pharmacokinetic profiles in rat, mouse, monkey, and dog.     

Design, synthesis, and biological evaluation of novel 4-alkylamino-1-hydroxymethylimidazo[1,2-a]quinoxalines as adenosine A(1) receptor antagonists

A series of 4-alkylamino-1-hydroxymethylimidazo[1,2-a]quinoxalines have been synthesized and evaluated for their adenosine A(1) receptor inhibitory activity in the radioligand binding assays. The compounds were tested for the inhibition percent (IP) and the affinity toward A(1)AR (K(i)) that IP were more than 90% in the nanomolar range. 4-Cyclopentylamino-7,8-dichloro-1-hydroxymethylimidazo[1,2-a]quinoxaline 18 is the most potent compound in this series, having K(i)=7nM, which is remarkably higher than that of IRFI-165 (K(i)=48). 1-Hydroxymethyl groups of the tricyclic heteroarmatic compounds displayed the potent affinities toward A(1)AR.     

Specificity and stability of a new PTH1 receptor antagonist,mouse TIP(7-39)

Parathyroid hormone 1 (PTH1) receptor antagonists might be of benefit in hypercalcemia of malignancy (HHM) and hyperparathyroidism. We previously identified bovine tuberoinfundibular peptide (7-39) (bTIP(7-39)) as a high-affinity PTH1 receptor antagonist. Mouse TIP(7-39) is an antagonist (rPTH1 K(B)=44 nM, rPTH2=940 nM) that is more potent than other known PTH1 receptor antagonists: bTIP(7-39) (210 nM), PTH-related protein (PTHrP)(7-34) (640 nM), and bPTH(7-34) (>3000 nM). Plasma proteases slowly (t(1/2)=81 min) inactivated [125I] mTIP(7-39). Intravenous plasma [125I]mTIP(7-39) was bi-phasically cleared (radioactivity t(1/2)=2.9 min (70%) and 120 min (30%), binding activity t(1/2)=3.6 min (92%), and t(1/2)=21 min (8%)). Loss of unlabeled mTIP(7-39) (250 microg/kg i.v.) receptor binding was similar. mTIP(7-39)'s high-affinity should facilitate animal evaluation of effects of PTH1 receptor antagonism.     

4-(2-pyridyl)piperazine-1-carboxamides: potent vanilloid receptor 1 antagonists

A series of 4-(2-pyridyl)piperazine-1-carboxamide analogues based on the lead compound 1 was synthesized and evaluated for VR1 antagonist activity in capsaicin-induced (CAP) and pH (5.5)-induced (pH) FLIPR assays in a rat VR1-expressing HEK293 cell line. Potent VR1 antagonists were identified through SAR studies. From these studies, 18 was found to be very potent in the in vitro assay [IC(50)=4.8 nM (pH) and 35 nM (CAP)] and orally available in rat (F%=15.1).     

N-Alkylidenearylcarboxamides as new potent and selective CB(2) cannabinoid receptor agonists with good oral bioavailability

A novel series of N-alkylidenearylcarboxamides 4, a CB(2) receptor agonist, were synthesized and evaluated for activity against the human CB(2) receptor. In a previous paper, we reported that sulfonamide derivative 1 acted as a potent CB(2) receptor agonist (IC(50)=65 nM, EC(50)=19 nM, E(max)=90%). However, compound 1 also exhibited poor metabolic stability in human liver microsomes. During the structural modification of 1, we found that a novel series of N-alkylidenearylcarboxamide, 4-1, had a moderate affinity for the CB(2) receptor (IC(50)=260 nM, EC(50)=86 nM, E(max)=100%) and good metabolic stability in human liver microsomes. We explored its analogues to discover compounds with a high affinity for the CB(2) receptor and with good oral bioavailability. Among them, compounds 4-9 and 4-27 had high affinities for the human CB(2) receptor (CB(2) IC(50)=13 nM and 1.2 nM) and a high selectivity for CB(2) (CB(1) IC(50)/CB(2) IC(50)=270 and 1600); furthermore, significant plasma levels were observed following oral administration in rats (C(max)=233 ng/mL and 148 ng/mL, respectively, after a dose of 10 mg/kg). Furthermore, compound 4-9 had good oral bioavailability (F=52%, 3mg/kg).     

Discovery of potent CCR4 antagonists: Synthesis and structure-activity relationship study of 2,4-diaminoquinazolines

A new series of quinazolines that function as CCR4 antagonists were discovered during the screening of our corporate compound libraries. Subsequent compound optimization elucidated the structure-activity relationships and led the identification of 2-(1,4'-bipiperidine-1'-yl)-N-cycloheptyl-6,7-dimethoxyquinazolin-4-amine 14a, which showed potent inhibition in the [(35)S]GTPgammaS-binding assay (IC(50)=18nM). This compound also inhibited the chemotaxis of human and mouse CCR4-expressing cells (IC(50)=140nM, 39nM).     

Synthesis and biological evaluation of 5-[(aryl)(1H-imidazol-1-yl)methyl]-1H-indoles: potent and selective aromatase inhibitors

The synthesis and the aromatase (CYP19) inhibitory activity of 5-[(aryl)(imidazol-1-yl)methyl]-1H-indoles were reported. Among the tested racemate compounds, 5-[(4-chlorophenyl)(1H-imidazol-1-yl)methyl]-1H-indole 8b emerged as a potent CYP19 inhibitor (IC(50)=15.3 nM). Chiral chromatography allowed isolation of the (+) enantiomer 8b2, which was about twice as active as the racemate (IC(50)=9 nM).     

Alpha-substituted N-(4-tert-butylbenzyl)-N'-[4-(methylsulfonylamino)benzyl]thiourea analogues as potent and stereospecific TRPV1 antagonists

A series of alpha-substituted N-(4-tert-butylbenzyl)-N'-[4-(methylsulfonylamino)benzyl]thiourea analogues have been investigated as TRPV1 receptor antagonists. alpha-Methyl substituted analogues showed potent and stereospecific antagonism to the action of capsaicin on rat TRPV1 heterologously expressed in Chinese hamster ovary cells. In particular, compounds 14 and 18, which possess the R-configuration, exhibited excellent potencies (respectively, K(i)=41 and 39.2 nM and K(i(ant))=4.5 and 37 nM).     

Synthesis, biological evaluation and molecular docking studies of novel 2-(1,3,4-oxadiazol-2-ylthio)-1-phenylethanone derivatives

In present study, a series of new 2-(1,3,4-oxadiazol-2-ylthio)-1-phenylethanone derivatives (6a-6x) as potential focal adhesion kinase (FAK) inhibitors were synthesized. The bioassay assays demonstrated that compound 6i showed the most potent activity, which inhibited the growth of MCF-7 and A431 cell lines with IC(50) values of 140 ± 10 nM and 10 ± 1 nM, respectively. Compound 6i also exhibited significant FAK inhibitory activity (IC(50)=20 ± 1 nM). Docking simulation was performed to position compound 6i into the active site of FAK to determine the probable binding model.     

Design and synthesis of piperidine farnesyltransferase inhibitors with reduced glucuronidation potential

The design and synthesis of a novel piperidine series of farnesyltransferase (FTase) inhibitors with reduced potential for metabolic glucuronidation are described. The various substitution and exchange of the phenyl group at the C-2 position of the previously described 2-(4-hydroxy)phenyl-3-nitropiperidine 1a (FTase IC(50)=5.4nM) resulted in metabolically stable compounds with potent FTase inhibition (14a IC(50)=4.3nM, 20a IC(50)=3.0nM, and 50a IC(50)=16nM). Molecular modeling studies of these compounds complexed with FTase and farnesyl pyrophosphate are also described.     

Synthesis, biochemical evaluation of a range of potent 4-substituted phenyl alkyl imidazole-based inhibitors of the enzyme complex 17alpha-Hydroxylase/17,20-Lyase (P45017alpha)

We report the synthesis, biochemical evaluation and rationalisation of the inhibitory activity of a number of azole-based compounds as inhibitors of the two components of the cytochrome P-450 enzyme 17alpha-hydroxylase/17,20-lyase (P450(17alpha)), i.e. 17alpha-hydroxylase (17alpha-OHase) and 17,20-lyase (lyase). The results suggest that the compounds synthesised are potent inhibitors, with 7-phenyl heptyl imidazole (11) (IC(50)=320 nM against 17alpha-OHase and IC(50)=100 nM against lyase); 1-[7-(4-fluorophenyl) heptyl] imidazole (14) (IC(50)=170 nM against 17alpha-OHase and IC(50)=57 nM against lyase); 1-[5-(4-bromophenyl) pentyl] imidazole (19) (IC(50)=500 nM against 17alpha-OHase and IC(50)=58 nM against lyase) being the most potent inhibitors within the current study, in comparison to ketoconazole (KTZ) (IC(50)=3.76 microM against 17alpha-OHase and IC(50)=1.66 microM against lyase). Furthermore, consideration of the inhibitory activity against the two components shows that all of the compounds tested are less potent towards the 17alpha-OHase in comparison to the lyase component, a desirable property in the development of novel inhibitors of P450(17alpha). From the modelling of these compounds onto the novel substrate heme complex (SHC) for the overall enzyme complex, the length of the compound, along with its ability to undergo interaction with the active site corresponding to the C(3) area of the steroidal backbone, are suggested to play a key role in determining the overall inhibitory activity.     

Discovery and initial SAR of arylsulfonylpiperazine inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1)

High-throughput screening of a small-molecule compound library resulted in the identification of a series of arylsulfonylpiperazines that are potent and selective inhibitors of human 11beta-Hydroxysteroid Dehydrogenase Type 1 (11beta-HSD1). Optimization of the initial lead resulted in the discovery of compound (R)-45 (11beta-HSD1 IC(50)=3nM).     

2-(Arylmethyl)-3-substituted quinuclidines as selective alpha 7 nicotinic receptor ligands

A series of 2-(arylmethyl)-3-substituted quinuclidines was developed as alpha7 neuronal nicotinic acetylcholine receptor (nAChR) agonists based on a putative pharmacophore model. The series is highly selective for the alpha7 over other nAChRs (e.g., the alpha4beta2 of the CNS, and the muscle and ganglionic subtypes) and is functionally tunable at alpha7. One member of the series, (+)-N-(1-azabicyclo[2.2.2]oct-3-yl)benzo[b]furan-2-carboxamide (+)-8l), has potent agonistic activity for the alpha7 nAChR (EC(50)=33nM, I(max)=1.0), at concentrations below those that result in desensitization.     

Synthesis and SAR of N-benzoyl-L-biphenylalanine derivatives: discovery of TR-14035, a dual alpha(4)beta(7)/alpha(4)beta(1) integrin antagonist

alpha(4)beta(1) and alpha(4)beta(7) integrins are key regulators of physiologic and pathologic responses in inflammation and autoimmune disease. The effectiveness of anti-integrin antibodies to attenuate a number of inflammatory/immune conditions provides a strong rationale to target integrins for drug development. Important advances have been made in identifying potent and selective candidates, peptides and peptidomimetics, for further development. Herein, we report the discovery of a series of novel N-benzoyl-L-biphenylalanine derivatives that are potent inhibitors of alpha4 integrins. The potency of the initial lead compound (1: IC(50) alpha(4)beta(7)/alpha(4)beta(1)=5/33 microM) was optimized via sequential manipulation of substituents to generate low nM, orally bioavailable dual alpha(4)beta(1)/alpha(4)beta(7) antagonists. The SAR also led to the identification of several subnanomolar antagonists (134, 142, and 143). Compound 81 (TR-14035; IC(50) alpha(4)beta(7)/alpha(4)beta(1)=7/87 nM) has completed Phase I studies in Europe. The synthesis, SAR and biological evaluation of these compounds are described.     

Enantioselective synthesis of S-(+)-2beta-carboalkoxy-3alpha-[bis(4-fluorophenyl)methoxy]tropanes as novel probes for the dopamine transporter

Synthesis of a series of pure S-(+)-2beta-carboalkoxy-3alpha-[bis(4-fluorophenyl)methoxy]tropanes (>99% ee) was achieved by employing a chiral amine-induced asymmetric reaction of tropinone with methyl cyanoformate as the key step. In this series, all of the S-(+)-enantiomers were 2-fold more potent than their racemic mixtures and all displayed high-affinity binding for DAT (K(i)=13-40 nM). These data support previous findings of significant divergence in structural requirements for high-affinity DAT binding among tropane-based inhibitors. Furthermore, the 2-substituent in the 3alpha-[bis(4-fluorophenyl)methoxy]tropane series is well tolerated at the DAT but not at SERT (K(i)=690-2040 nM), or muscarinic M(1) receptors (K(i)=133-4380 nM) resulting in highly selective DAT ligands that may provide new leads toward a cocaine-abuse therapeutic.     

The influence of modifications in imide fragment structure on 5-HT(1A) and 5-HT(7) receptor affinity and in vivo pharmacological properties of some new 1-(m-trifluoromethylphenyl)piperazines

New, flexible (7, 9, 11 and 13) and rigid (8, 10, 12 and 14) imides with a 1-(m-trifluorophenyl)piperazine fragment and a tetramethylene or a 1e,4e-cyclohexylene spacer, respectively, showed very high affinity (K(i)=0.3-34 nM) and agonistic in vivo activity for 5-HT(1A) receptors. Flexible new compounds and the previously described 5 also bound to 5-HT(7) receptors (K(i)=21-134 nM). Selected glutarimide derivatives, that is, the most potent postsynaptic 5-HT(1A) receptor agonist rigid compound 8 and its flexible analogue 7, as well as the previously described full agonist-rigid compound 6 and the partial agonist-its flexible counterpart 5 exhibited moderate affinity for alpha(1)-adrenoceptors (K(i)=85 - 268 nM), but were practically devoid of any affinity for dopamine D(2) sites. Those glutarimides demonstrated anxiolytic- (5 and 7) and antidepressant-like (5, 6 and 8) activity in the four-plate and the swim tests in mice, respectively; at the same time, however, they inhibited the locomotor activity of mice. The antidepressant-like effect of 8 was significantly stronger than that induced by imipramine used as a reference antidepressant.     

1,3-Dipropyl-8-(1-phenylacetamide-1H-pyrazol-3-yl)-xanthine derivatives as highly potent and selective human A(2B) adenosine receptor antagonists

A new series of 1,3-dipropyl-8-(1-phenylacetamide-1H-pyrazol-3-yl)-xanthine derivatives has been identified as potent A(2B) adenosine receptor antagonists. The products have been evaluated for their binding affinities for the human A(2B), A(1), A(2A), and A(3) adenosine receptors. N-(4-chloro-phenyl)-2-[3-(2,6-dioxo-1,3-dipropyl-2,3,6,7-tetrahydro-1H-purin-8-yl)-5-methyl-pyrazol-1-yl] (11c) showed a high affinity for the human A(2B) adenosine receptor K(i)=7nM and good selectivity (A(1), A(2A), A(3)/A(2B)>140). Synthesis and SAR of this novel class of compounds is presented herein.     

4-arylphthalazin-1(2H)-one derivatives as potent antagonists of the melanin concentrating hormone receptor 1 (MCH-R1)

A novel series of 4-arylphthalazin-1(2H)-one linked to arylpiperidines were synthesized and evaluated as MCH-R1 antagonists. The results of an extensive SAR study probing the effects of substituents on the 4-arylphthalazin-1(2H)-one C-4 aryl group led to the identification of the 4-(3,4-difluorophenyl) derivative as a highly potent MCH-R1 inhibitor with an IC(50)=1nM. However, further investigations showed that this substance has unacceptable pharmacokinetic properties including a high clearance and volume of distribution.     

1,7- and 2,7-naphthyridine derivatives as potent and highly specific PDE5 inhibitors

Novel 1,7- and 2,7-naphthyridine derivatives, designed by the introduction of nitrogen atom into the phenyl ring of previously reported 4-aryl-1-isoquinolinone derivatives, were disclosed as a new structural class of potent and specific PDE5 inhibitors. Among them, 2,7-naphthyridine 4c showed potent PDE5 inhibition (IC(50)=0.23 nM) and one of the best PDE5 specificities against PDEs1-4,6 (>100,000-fold selective versus PDE1-4, 240-fold selective vs PDE6). This compound showed more potent relaxant effects on isolated rabbit corpus cavernosum (EC(30)=5.0 nM) than Sildenafil (EC(30)=8.7 nM). The compound 4c (T-0156) was selected for further biological and pharmacological evaluation of erectile dysfunction.