Discovery of a substituted 8-arylquinoline series of PDE4 inhibitors: structure-activity relationship, optimization, and identification of a highly potent, well tolerated, PDE4 inhibitor

The discovery and SAR of a new series of substituted 8-arylquinoline PDE4 inhibitors are herein described. This work has led to the identification of several compounds with excellent in vitro and in vivo profiles, including a good therapeutic window of emesis to efficacy in several animal models. Typical optimized compounds from this series are potent inhibitors of PDE4 (IC(50)<1nM) and also of LPS-induced TNF-alpha release in human whole blood (IC(50)<0.5microM). The same compounds are potent inhibitors of ovalbumin-induced bronchoconstriction in conscious guinea pigs (EC(50)<0.1mg/kg ip) but require a dose of about 10mg/kg po in the squirrel monkey to produce an emetic response. From this series of compounds, 23a (L-454,560) was identified as an optimized compound.     

Cantharimides: a new class of modified cantharidin analogues inhibiting protein phosphatases 1 and 2A.

Cantharidin and its analogues have been of considerable interest as potent inhibitors of the serine/threonine protein phosphatases 1 and 2A (PP1 and PP2A). However, limited modifications to the parent compounds is tolerated. As part of an on-going study we have developed a new series of cantharidin analogues, the cantharimides. Inhibition studies indicate that cantharimides possessing a D- or L-histidine, are more potent inhibitors of PP1 and PP2A (PP1 IC(50)=3.22+/-0.7 microM; PP2A IC(50)=0.81+/-0.1 microM and PP1 IC(50)=2.82+/-0.6 microM; PP2A IC(50)=1.35+/-0.3 microM, respectively) than norcantharidin (PP1 IC(50)=5.31+/-0.76 microM; PP2A IC(50)=2.9+/-1.04 microM) and essentially equipotent with cantharidin (PP1 IC(50)=3.6+/-0.42 microM; PP2A IC(50)=0.36+/-0.08 microM). Cantharimides with non-polar or acidic amino acid residues are only poor inhibitors of PP1 and PP2A.     

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.     

Pentacyclic triterpenes. Part 5: synthesis and SAR study of corosolic acid derivatives as inhibitors of glycogen phosphorylases

The synthesis and biological evaluation of corosolic acid derivatives and related compounds as inhibitors of rabbit muscle glycogen phosphorylase a is described. Within this series of compounds, 8 (IC(50)=7.31 microM), 12d (IC(50)=3.26 microM), and 12e (IC(50)=5.1 microM) exhibited more potent activities than the parent compound 1 (IC(50)=20 microM). SAR of these compounds is also discussed.     

Quantitative studies of inhibitors of ADP-ribosylation in vitro and in vivo

The ADP-ribosyl moiety of NAD+ is consumed in reactions catalyzed by three classes of enzymes: poly(ADP-ribose) polymerase, protein mono(ADP-ribosyl)transferases, and NAD+ glycohydrolases. In this study, we have evaluated the selectivity of compounds originally identified as inhibitors of poly(ADP-ribose) polymerase on members of the three classes of enzymes. The 50% inhibitory concentration (IC50) of more than 20 compounds was determined in vitro for both poly(ADP-ribose) polymerase and mono(ADP-ribosyl)transferase A in an assay containing 300 microM NAD+. Of the compounds tested, benzamide was the most potent inhibitor of poly(ADP-ribose) polymerase with an IC50 of 3.3 microM. The IC50 for benzamide for mono(ADP-ribosyl)transferase A was 4.1 mM, and similar values were observed for four additional cellular mono(ADP-ribosyl)transferases. The IC50 for NAD+ glycohydrolase for benzamide was approximately 40 mM. For seven of the best inhibitors, inhibition of poly(ADP-ribose) polymerase in intact C3H1OT1/2 cells was studied as a function of the inhibitor concentration of the culture medium, and the concentration for 50% inhibition (culture medium IC50) was determined. Culture medium IC50 values for benzamide and its derivatives were very similar to in vitro IC50 values. For other inhibitors, such as nicotinamide, 5-methyl-nicotinamide, and 5-bromodeoxyuridine, culture medium IC50 values were 3-5-fold higher than in vitro IC50 values. These results suggest that micromolar levels of the benzamides in the culture medium should allow selective inhibition of poly(ADP-ribose) metabolism in intact cells. Furthermore, comparative quantitative inhibition studies should prove useful for assigning the biological effects of these inhibitors as an effect on either poly(ADP-ribose) or mono(ADP-ribose) metabolism.     

Synthesis and biochemical evaluation of a range of potent benzyl imidazole-based compounds as potential inhibitors of the enzyme complex 17alpha-hydroxylase/17,20-lyase (P450(17alpha))

The cytochrome P-450 enzyme, 17alpha-hydroxylase/17,20-lyase (P450(17alpha)), is a potential target in hormone-dependent cancers. Here, we report the synthesis and biochemical evaluation of a range of benzyl imidazole-based compounds which have been targeted against the two components of this enzyme, that is, 17alpha-hydroxylase (17alpha-OHase) and 17,20-lyase (lyase). The results from the biochemical testing suggest that the compounds synthesised are good inhibitors, with N-4-iodobenzyl imidazole (5) (IC50=10.06 microM against 17alpha-OHase and IC50=1.58 microM against lyase) showing equipotent activity against lyase compared to the standard compound, ketoconazole (KTZ) (IC50=3.76+/-0.01 microM against 17alpha-OHase and IC50=1.66+/-0.15 microM against lyase). Furthermore, the compounds tested are less potent towards the 17alpha-OHase component, a desirable property in the development of novel inhibitors of P450(17alpha).     

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.     

Structure-activity relationships of chiral selective norepinephrine reuptake inhibitors (sNRI) with increased oxidative stability

The synthesis and SAR of a series of chiral heterocyclic ring-constrained norepinephrine reuptake inhibitors are described. The best compounds compare favorably with atomoxetine in potency (IC(50)s<10 nM), selectivity against the other monoamine transporters, and inhibition of CYP2D6 (IC(50)s>1 microM). In addition, the compounds are generally more stable than atomoxetine to oxidative metabolism and thus are likely to have lower clearance in humans.     

Design, synthesis, and biological evaluation of 8-biarylquinolines: a novel class of PDE4 inhibitors

The structure-activity relationship of a novel series of 8-biarylquinolines acting as type 4 phosphodiesterase (PDE4) inhibitors is described herein. Prototypical compounds from this series are potent and non-selective inhibitors of the four distinct PDE4 (IC(50)<10 nM) isozymes (A-D). In a human whole blood in vitro assay, they inhibit (IC(50)<0.5 microM) the LPS-induced release of the cytokine TNF-alpha. Optimized inhibitors were evaluated in vivo for efficacy in an ovalbumin-induced bronchoconstriction model in conscious guinea pigs. Their propensity to produce an emetic response was evaluated by performing pharmacokinetic studies in squirrel monkeys. This work has led to the identification of several compounds with excellent in vitro and in vivo profiles, including a good therapeutic window of efficacy over emesis.     

Tetraketones: a new class of tyrosinase inhibitors

Twenty-eight tetraketones (1-28) with variable substituents at C-7 were synthesized and evaluated as tyrosinase inhibitors. Remarkably compounds 25 (IC(50)=2.06 microM), 11 (IC(50)=2.09 microM), 15 (IC(50)=2.61 microM), and 27 (IC(50)=3.19 microM) were found to be the most active compounds of the series, even better than both standards kojic acid (IC(50)=16.67 microM) and L-mimosine (IC(50)=3.68 microM). This study may lead to the discovery of therapeutically potent agents against clinically very important dermatological disorders including hyperpigmentation as well as skin melanoma.     

Discovery of structurally diverse HIV-1 integrase inhibitors based on a chalcone pharmacophore

Recently, we reported small-molecule chalcones as a novel class of HIV-1 integrase (IN) inhibitors. The most potent compound showed an IC50 value of 2 microM for both IN-mediated 3'-processing and strand transfer reactions. To further utilize the chalcones, we developed pharmacophore models to identify chemical signatures important for biological activity. The derived models were validated with a collection of published inhibitors, and then were applied to screen a subset of our small molecule database. We tested 71 compounds in an in vitro assay specific for IN enzymatic activity. Forty-four compounds showed inhibitory potency<100 microM, and four of them exhibited IC50 values<10 microM. One compound, 62, with an IC50 value of 0.6 microM, displayed better potency than the original chalcone 2 against the strand transfer process. This study demonstrates the systematic use of pharmacophore technologies to discover novel structurally diverse inhibitors based on lead molecules that would exhibit poor characteristics in vivo. The identified compounds have the potential to exhibit favorable pharmacokinetic and pharmacodynamic profiles.     

Substituted uracil derivatives as potent inhibitors of poly(ADP-ribose)polymerase-1 (PARP-1)

A new class of PARP-1 inhibitors, namely substituted fused uracil derivatives were synthesised. Starting from a derivative with an IC(50)=2microM the chemical optimisation program led to compounds with more than a 100-fold increase in potency (IC(50)<20nM). Additionally, physicochemical and pharmacokinetic properties were evaluated. It could be shown that compounds bearing a piperazine or phenyl substituted betaAla-Gly side chain exhibited the best overall profile.     

Inhibition of protein kinase CK2 by condensed polyphenolic derivatives. An in vitro and in vivo study

ATP site-directed inhibitors that can target individual kinases are powerful tools for use in signal transduction research, all the more so in the case of a pleiotropic, constitutively active protein kinase such as CK2, which is not turned on in response to specific stimuli. By screening a library of more than 200 derivatives of natural polyphenolic compounds, we have identified 16 molecules which inhibit CK2 with IC(50) values of 相似文献   

Specific inhibitors of Plasmodium falciparum thioredoxin reductase as potential antimalarial agents

Plasmodium falciparum thioredoxin reductase (PfTrxR: NADPH+Trx(S)2+H+<-->NADP++Trx(SH)2) is a high Mr flavin-dependent TrxR that reduces thioredoxin (Trx) via a CysXXXXCys pair located penultimately to the C-terminal Gly. In this respect, PfTrxR differs significantly from its human counterpart which bears a Cys-Sec redox pair at the same position. PfTrxR is essentially involved in antioxidant defense and redox regulation of the parasite and has been previously validated by knock-out studies as a potential drug target for malaria chemotherapy. Moreover, human TrxR is present in most cancer cells at levels tenfold higher than in normal cells. Here we report the discovery of a series of potent inhibitors of PfTrxR. The three most promising inhibitors, 3(IC50(PfTrxR)=2 microM and IC50(hTrxR)=50 microM), 7(IC50(PfTrxR)=2 microM and IC50(hTrxR)=140 microM), and 11(IC50(PfTrxR)=0.5 microM and IC50(hTrxR)=4 microM) were selective for the parasite enzyme. Detailed mechanistic characterization of the effects of these compounds on the PfTrxR-catalyzed reaction showed clear uncompetitive inhibition with respect to both substrate and cofactor. For the most specific PfTrxR inhibitor 7, an alkylation mechanism study based on a thiol conjugation model was performed. Furthermore, all three compounds were active in the lower micromolar range on the chloroquine-resistant P. falciparum strain K1 in vitro.     

Hydrophobicity, a physicochemical factor in the inhibition of the enzyme estrone sulfatase (ES).

We report the initial structure-activity relationship study (SAR) (in particular logP) of a series of compounds based upon 4-sulfamated phenyl ketones as potent inhibitors of the enzyme estrone sulfatase (ES). The results of the study show that these compounds are irreversible inhibitors of ES and that they are more potent than COUMATE, but weaker than EMATE. Analysis of the SAR data shows a strong correlation between IC(50) and logP but also supports our previous study, which suggests a very strong relationship between pK(a) and IC(50).     

Bidentate peptides: highly potent new inhibitors of enkephalin degrading enzymes

Three series of bidentates bearing an hydroxamic or an N-Acyl-N-hydroxy amino group on structures related to Phe-Gly or Phe-Ala exhibit strong inhibitory potency against purified enkephalinase with IC50 values in the 4 to 15 nM range. As with thiol-containing inhibitors, such as thiorphan, the most active compounds are those in which a methylene spacer separates the benzyl P1' moiety from the Zn coordinating residue. Formation of a bidentate complex with the metal enzyme is clearly demonstrated by a loss of potency of three order of magnitude following the removal of one component of the bidentate group. All the compounds studied are unable to interact with angiotensin converting enzyme (IC50 greater than 10,000 nM). Moreover, compounds of the general formula HONHCO-CH2-CH(CH2 phi)-CONH-CH(R)-COOH belonging to the most active series of enkephalinase blockers (IC50 approximately 4 nM) behave also as highly potent and competitive inhibitors (IC50 approximately 10 nM) of a Tyr-Gly releasing dipeptidylaminopeptidase purified from rat brain. The pure steroisomer [(R)-3-(N-hydroxy)carboxamido-2-benzylpropanoyl]-L-alanine designated kelatorphan, exhibits also a relatively good inhibitory potency against aminopeptidases (IC50 approximately 10 microM) and can be considered as the first virtually complete inhibitor of enkephalin metabolism. This very interesting property of inhibiting all three enzymes of enkephalin metabolism could enhance the required selectivity for a possible clinical use of these inhibitors as new analgesic and psychoactive drugs.     

6-Nitrobenzimidazole derivatives: potential phosphodiesterase inhibitors: synthesis and structure-activity relationship

6-Nitrobenzimidazole derivatives (1-30) synthesized and their phosphodiesterase inhibitory activities determined. Out of thirty tested compounds, ten showed a varying degrees of phosphodiesterase inhibition with IC(50) values between 1.5±0.043 and 294.0±16.7 μM. Compounds 30 (IC(50)=1.5±0.043 μM), 1 (IC(50)=2.4±0.049 μM), 11 (IC(50)=5.7±0.113 μM), 13 (IC(50)=6.4±0.148 μM), 14 (IC(50)=10.5±0.51 μM), 9 (IC(50)=11.49±0.08 μM), 3 (IC(50)=63.1±1.48 μM), 10 (IC(50)=120.0±4.47 μM), and 6 (IC(50)=153.2±5.6 μM) showed excellent phosphodiesterase inhibitory activity, much superior to the standard EDTA (IC(50)=274±0.007 μM), and thus are potential molecules for the development of a new class of phosphodiesterase inhibitors. A structure-activity relationship is evaluated. All compounds are characterized by spectroscopic parameters.     

New inhibitors of scrapie-associated prion protein formation in a library of 2000 drugs and natural products

Transmissible spongiform encephalopathies (TSEs) are fatal, untreatable neurodegenerative diseases associated with the accumulation of a disease-specific form of prion protein (PrP) in the brain. One approach to TSE therapeutics is the inhibition of PrP accumulation. Indeed, many inhibitors of the accumulation of PrP associated with scrapie (PrP(Sc)) in scrapie-infected mouse neuroblastoma cells (ScN(2)a) also have antiscrapie activity in rodents. To expedite the search for potential TSE therapeutic agents, we have developed a high-throughput screening assay for PrP(Sc) inhibitors using ScN(2)a cells in a 96-well format. A library of 2000 drugs and natural products was screened in ScN(2)a cells infected with scrapie strain RML (Chandler) or 22L. Forty compounds were found to have concentrations causing 50% inhibition (IC(50)s) of PrP(Sc) accumulation of 相似文献   

Discovery of novel EGFR tyrosine kinase inhibitors by structure-based virtual screening

By using of structure-based virtual screening, 13 novel epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors were discovered from 197,116 compounds in the SPECS database here. Among them, 8 compounds significantly inhibited EGFR kinase activity with IC(50) values lower than 10 μM. 3-{[1-(3-Chloro-4-fluorophenyl)-3,5-dioxo-4-pyrazolidinylidene]methyl}phenyl 2-thiophenecarboxylate (13), particularly, was the most potent inhibitor possessing the IC(50) value of 3.5 μM. The docking studies also provide some useful information that the docking models of the 13 compounds are beneficial to find a new path for designing novel EGFR inhibitors.     

Design, synthesis, and biological evaluation of N-acetyl-2-(or 3-)carboxymethylbenzenesulfonamides as cyclooxygenase isozyme inhibitors

A group of N-acetyl-2-(or 3-)carboxymethylbenzenesulfonamides, possessing either a F or a substituted-phenyl ring substituent (4-F, 2,4-F2, 4-SO2Me, 4-OCHMe2) attached to its C-4 or C-6 position, was prepared using a palladium-catalyzed Suzuki cross-coupling reaction for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. Although N-acetyl-3-carboxymethyl-6-fluorobenzenesulfonamide [14, COX-1 IC50 = 2.26 microM; COX-2 IC50 = 0.012 microM; COX-2 selectivity index (SI) = 188] and N-acetyl-3-carboxymethyl-6-(4-isopropoxyphenyl)benzenesulfonamide (20c, COX-1 IC50 >100 microM; COX-2 IC50 = 0.15 microM; COX-2 SI >667) exhibited potent in vitro COX-2 inhibitory activity and high COX-2 selectivity, both compounds were inactive anti-inflammatory agents in a carrageenan-induced rat paw edema assay. In contrast, the less potent and less selective COX-2 inhibitors N-acetyl-2-carboxymethyl-4-fluorobenzenesulfonamide (12, COX-1 IC50 = 4.25 microM; COX-2 IC50 = 0.978 microM; COX-2 SI = 4.3), N-acetyl-2-carboxymethyl-4-(2,4-difluorophenyl)benzenesulfonamide (17c, COX-1 IC50 = 1.02 microM; COX-2 IC50 = 1.00 microM; COX-2 SI = 1.02), and N-acetyl-3-carboxymethyl-6-(4-methanesulfonylphenyl)benzenesulfonamide (20e, COX-1 IC50 = 0.109 microM; COX-2 IC50 = 1.14 microM; COX-2 SI = 0.095) exhibited moderate anti-inflammatory activity where a 75 mg/kg oral dose reduced inflammation 26%, 14%, and 20%, respectively, at 3 h postdrug administration relative to the reference drug aspirin where a 50 mg/kg oral dose reduced inflammation by 25% at 3 h postdrug administration.