Design, synthesis and biological evaluation of substituted dioxodibenzothiazepines and dibenzocycloheptanes as farnesyltransferase inhibitors

A new series of FTase inhibitors containing a tricyclic moiety--dioxodibenzothiazepine or dibenzocycloheptane--has been designed and synthesized. Among them, dioxodibenzothiazepine 18d displayed significant inhibitory FTase activity (IC(50)=17.3 nM) and antiproliferative properties.     

Synthesis and evaluation of GGPP geometric isomers: divergent substrate specificities of FTase and GGTase I.

A stereocontrolled synthetic route has been used to prepare two of the geometric isomers of all-trans-GGPP. Neither of these isomers is effective substrates for mammalian GGTase I, but 3 is a potent inhibitor of this enzyme (IC(50)=100 nM). Surprisingly, both compounds are effective substrates for mammalian FTase.     

Isoquinoline derivatives as potent CRTH2 receptor antagonists: synthesis and SAR

Synthesis and structure-activity relationship of a novel series of isoquinoline CRTH2 receptor antagonists are described. One of the most potent compounds, TASP0376377 (6m), showed not only potent binding affinity (IC(50)=19 nM) but also excellent functional antagonist activity (IC(50)=13 nM). TASP0376377 was tested for its ability of a chemotaxis assay to show the effectiveness (IC(50)=23 nM), which was in good agreement with the CRTH2 antagonist potency. Furthermore, TASP0376377 showed sufficient selectivity for binding to CRTH2 over the DP1 prostanoid receptor (IC(50)>1 μM) and COX-1 and COX-2 enzymes (IC(50)>10 μM).     

Benzimidazolones and indoles as non-thiol farnesyltransferase inhibitors based on tipifarnib scaffold: synthesis and activity

A series of analogs of tipifarnib (1) has been synthesized as inhibitors of FTase by substituting the benzimidazolones and indoles for the 2-quinolone of tipifarnib. The novel benzimidazolones are potent and selective FTase inhibitors (FTIs) with IC(50) values of the best compounds close to that of tipifarnib. The current series demonstrate good cellular activity as measured in their inhibiting the Ras processing in NIH-3T3 cells, with compounds 2c and 2f displaying EC(50) values of 18 and 22nM, respectively.     

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.     

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 and structure-activity relationships of urea derivatives as potent and novel CCR3 antagonists

The synthesis and structure-activity relationships of ureas as CCR3 antagonists are described. Optimization starting with lead compound 2 (IC(50)=190 nM) derived from initial screening hit compound 1 (IC(50)=600 nM) led to the identification of (S)-N-((1R,3S,5S)-8-((6-fluoronaphthalen-2-yl)methyl)-8-azabicyclo[3.2.1]octan-3-yl)-N-(2-nitrophenyl)pyrrolidine-1,2-dicarboxamide 27 (IC(50)=4.9 nM) as a potent CCR3 antagonist.     

Small molecule somatostatin receptor subtype-2 antagonists

The first potent small molecule sst2 antagonists are reported. Altering known sst2 agonist molecules yielded compounds with high sst2 binding affinity and full antagonist activity. Compound 7a, for example, displaced somatostatin binding to the sst2 receptor with an IC(50)=2.9 nM and antagonized somatostatin action with an IC(50)=29nM.     

Substituted 2,2-bisaryl-bicycloheptanes as novel and potent inhibitors of 5-lipoxygenase activating protein

The discovery and SAR of a novel series of substituted 2,2-bisaryl-bicycloheptane inhibitors of 5-lipoxygenase activating protein (FLAP) are herein described. SAR studies have shown that 2,5-substitution on the exo-aryl group is optimal for potency. The most potent compounds in this series have an ortho-nitrogen aryl linked with a methyleneoxy as the 5-substituent and a polar group such as a urethane as the 2-substituent. One of the most potent compounds identified is the 5-benzothiazolymethoxy-2-pyridinylcarbamate derivative 2 (FLAP IC(50)=2.8 nM) which blocks 89% of ragweed induced urinary LTE(4) production in dogs (at an I.V. dose of 2.5 microg/kg/min). This compound inhibits calcium ionophore stimulated LTB(4) production in both human polymorphonuclear (PMN) leukocytes and human whole blood (IC(50)=2.0 and 33 nM, respectively).     

Discovery of novel Cobactin-T based matrix metalloproteinase inhibitors via a ring closing metathesis strategy

The discovery of potent N-hydroxyl caprolactam matrix metalloproteinase (MMP) inhibitors (6) based on the natural product Cobactin-T (2) is described. The synthetic method, which utilizes the ring closing metathesis reaction, is compatible to provide complementary (R) and (S) enantiomers. These compounds tested against MMP-2 and 9, show that the R stereochemistry (i.e., 16), which is opposite for that found in the natural product Cobactin-T is >1000-fold more active with IC(50) values of 0.2-0.6nM against both enzymes. The variation in the incorporation of the sulfonamide enzyme recognition element (Ar(2)XAr(1)SO(2)N(R(1)), 6), along with alterations in the RCM/double bond chemistry (R(2)) provided a series of sub nanomolar MMP inhibitors. For example, compounds 16 and 34 were found to be the most potent with IC(50) values against MMP-2 and MMP-9 found to be between 0.2 and 0.6nM with 34 being the most potent compound discovered (MMP-2 IC(50)=0.39nM and MMP-9 IC(50)=0.22nM). Compounds 16 and 34 showed acceptable drug-like properties in vivo with compound 34 showing oral bioavailability.     

Analysis of farnesyl transferase activity during hormone-induced maturation of Xenopus laevis oocytes

Preincubation of Xenopus laevis oocytes with insulin or insulin-like growth factor 1 (IGF-1) resulted in inhibition of farnesyl transferase (FTase) activity measured both in vivo (after microinjection of tritiated farnesyl pyrophosphate and Ras-CVIM into oocytes) and in extracts using a filtration assay. FTase activity measured in oocyte extracts was inhibited 55% after a 20 min treatment of oocytes with 1 microM insulin or 10 nM IGF-1. The apparent IC(50) for inhibition of oocyte FTase by IGF-1 is 0.3 nM. The observed decrease in FTase activity was apparently not due to translocation of enzyme from cytosol to membrane, since activities measured both in soluble extracts and resuspended crude pellets displayed comparable levels of inhibition following hormone treatment. Using a hexapeptide (TKCVIM) as substrate, FTase activity was also inhibited 65% when oocytes were pretreated with 10 nM IGF-1. Two FTase inhibitors [(alpha-hydroxyfarnesyl) phosphonic acid (HFPA) and chaetomellic acid A (CA)] effectively inhibited Xenopus oocyte FTase by 80-90% when added to assay mixtures (IC(50) values of 338 +/- 96 nM HFPA and 232 +/- 80 nM CA) or after incubation of oocytes in drug before preparation of soluble extracts for assay (IC(50) values of 7 +/- 6 nM HFPA and 328 +/- 128 nM CA). The farnesyl transferase inhibitors were observed to slow the time course of oocyte maturation but did not block the IGF-1-induced maturation response. J. Exp. Zool. 286:193-203, 2000.Copyright 2000 Wiley-Liss, Inc.     

Sulfonamide derivatives as new potent and selective CB2 cannabinoid receptor agonists

A novel series of sulfonamide derivatives 3, the CB(2) receptor agonists, was synthesized and evaluated for activity against the human CB(2) receptor. We first identified sulfonamide 3a, which was obtained by random screening of our in-house chemical library as a moderately active (CB(2) IC(50)=340nM) CB(2) receptor agonist. We then attempted to test its analogues to identify compounds with a high affinity for the CB(2) receptor. One of these, compound 3f, exhibited high affinity for the human CB(2) receptor (IC(50)=16nM) and high selectivity for CB(2) over CB(1) (CB(1) IC(50)/CB(2)IC(50)=106), and behaved as a full CB(2) receptor agonist in the [(35)S]GTPgammaS binding assay (CB(2) EC(50)=7.2nM, E(max)=100%).     

Functionalization at position 3 of the phenyl ring of the potent mGluR5 noncompetitive antagonists MPEP

We described the synthesis and biological evaluation of MPEP analogs functionalized at the position 3 of the phenyl ring. The results point out the limitation in the choice of a functional group at this position; the only substituents leading to retention of activity are NO(2) (IC(50)=13 nM) and CN (IC(50)=8 nM).     

Enhanced FTase activity achieved via piperazine interaction with catalytic zinc

Benzocycloheptapyridine tricyclic compounds with piperazine or substituted piperidine moieties extending either from the 5- or 6-position of the tricyclic bridgehead exhibited enhanced FTase activity: this resulted from favorable binding of the ligand nitrogen with the catalytic zinc found in the FTase. A single isomer at C-11 with piperazine adduct extending from the 6-position, compound 24, exhibited excellent FTase activity with IC50 = 0.007 microM, soft agar IC50 = 72 nM, and Rat AUC(PO, 10 mpk) = 4.0 microM x h. X-ray of (-)-[8-chloro-6-(1-piperazinyl)-1H-benzo[5,6]]cyclohepta[1,2-b]pyridine-11-yl]-1-(methylsulfonyl)piperidine 24 bound to Ftase revealed favorable interaction between piperazine nitrogen and catalytic zinc atom.     

Activity of a novel dual thromboxane A(2)receptor antagonist and thromboxane synthase inhibitor (BM-573) on platelet function and isolated smooth muscles.

The pharmacomodulation of sulfonylureas structurally related to torasemide and characterized by a TXA(2)antagonism led to the synthesis of BM-573. This original molecule showed a high affinity (IC(50)1.3 nM) for the TXA(2)receptor of human platelets in comparison with both reference compounds, SQ-29548 (IC(50)21 nM) and sulotroban (IC(50)930 nM). Moreover, this torasemide derivative was found to be a potent inhibitor of human platelet aggregation induced by arachidonic acid (ED(100)=0.13 microM) or by U-46619 (ED(50)=0.24 microM), a TXA(2)agonist. BM-573 relaxed the isolated rat thoracic aorta (ED(50)=28.4 nM) and guinea-pig trachea (ED(50)=17.7 nM) contracted by U-46619. BM-573 (1 microM) completely reduced the platelet production of TXB(2)induced by arachidonic acid. Finally, BM-573 (30 mg/kg, per os) lost the diuretic properties of torasemide in rats.     

Synthesis and antimalarial evaluation of novel isocryptolepine derivatives

A series of mono- and di-substituted analogues of isocryptolepine have been synthesized and evaluated for in vitro antimalarial activity against chloroquine sensitive (3D7) and resistant (W2mef) Plasmodium falciparum and for cytotoxicity (3T3 cells). Di-halogenated compounds were the most potent derivatives and 8-bromo-2-chloroisocryptolepine displayed the highest selectivity index (106; the ratio of cytotoxicity (IC(50)=9005 nM) to antimalarial activity (IC(50)=85 nM)). Our evaluation of novel isocryptolepine compounds has demonstrated that di-halogenated derivatives are promising antimalarial lead compounds.     

Structure-Activity relationships of 2-substituted 5,7-Diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acids as a novel class of endothelin receptor antagonists

Synthesis and structure-activity relationships of 2-substituted-5,7-diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acids, a novel class of endothelin receptor antagonists, were described. Derivatization of a lead structure 1 (IC(50)=2.4nM, 170-fold selectivity) by incorporating a substituent such as an alkyl, alkoxy, alkylthio, or alkylamino group into the 2-position of the cyclopenteno[1,2-b]pyridine skeleton was achieved via the key intermediate 8. Introduction of an alkyl group led to the identification of potent ET(A)/ET(B) mixed receptor antagonists, a butyl (2d: IC(50)=0.21nM, 52-fold selectivity) and an isobutyl (2f: IC(50)=0.32nM, 26-fold selectivity) analogue. In contrast, installment of a primary amino group resulted in ET(A) selective antagonists, a propylamino 2p (IC(50)=0.12nM, 520-fold selectivity) and an isopropylamino 2q (IC(50)=0.10nM, 420-fold selectivity) analogue. These results suggested that a substituent at the 2-position of the 5,7-diarylcyclopenteno[1,2-b]pyridine-6-carboxylic acids played a key role in the binding affinity for both ET(A) and ET(B) receptors.     

Purification and properties of Arabidopsis thaliana type 1 protein phosphatase (PP1).

The Arabidopsis thaliana type 1 protein phosphatase (PP1) catalytic subunit was released from its endogenous regulatory subunits by ethanol precipitation and purified by anion exchange and microcystin affinity chromatography. The enzyme was identified by MALDI-TOF mass spectrometry from a tryptic digest of the purified protein as a mixture of PP1 isoforms (TOPP 1-6) indicating that at least 4-6 of the eight known PP1 proteins are expressed in sufficient quantities for purification from A. thaliana suspension cells. The enzyme had a final specific activity of 8950 mU/mg using glycogen phosphorylase a as substrate, had a subunit molecular mass of 35 kDa as determined by SDS-PAGE and behaved as a monomeric protein of approx. 39 kDa on Superose 12 gel filtration chromatography. Similar to the mammalian type 1 protein phosphatases, the A. thaliana enzyme was potently inhibited by Inhibitor-2 (IC(50)=0.65 nM), tautomycin (IC(50)=0.06 nM), microcystin-LR (IC(50)=0.01 nM), nodularin (IC(50)=0.035 nM), calyculin A (IC(50)=0.09 nM), okadaic acid (IC(50)=20 nM) and cantharidin (IC(50)=60 nM). The enzyme was also inhibited by fostriecin (IC(50)=22 microM), NaF (IC(50)=2.1 mM), Pi (IC(50)=9.5 mM), and PPi (IC(50)=0.07 mM). Purification of the free catalytic subunit allowed it to be used to probe protein phosphatase holoenzyme complexes that were enriched on Q-Sepharose and a microcystin-Sepharose affinity matrix and confirmed several proteins to be PP1 targeting subunits.     

2,4-disubstituted pyrimidines: a novel class of KDR kinase inhibitors

2,4-Disubstituted pyrimidines were synthesized as a novel class of KDR kinase inhibitors. Evaluation of the SAR of the screening lead compound 1 (KDR IC(50)=105 nM, Cell IC(50)=8% inhibition at 500 nM) led to the potent 3,5-dimethylaniline derivative 2d (KDR IC(50)=6 nM, cell IC(50)=19 nM).