Kinesin spindle protein (KSP) inhibitors. 9. Discovery of (2S)-4-(2,5-difluorophenyl)-n-[(3R,4S)-3-fluoro-1-methylpiperidin-4-yl]-2-(hydroxymethyl)-N-methyl-2-phenyl-2,5-dihydro-1H-pyrrole-1-carboxamide (MK-0731) for the treatment of taxane-refractory cancer.

Inhibition of kinesin spindle protein (KSP) is a novel mechanism for treatment of cancer with the potential to overcome limitations associated with currently employed cytotoxic agents. Herein, we describe a C2-hydroxymethyl dihydropyrrole KSP inhibitor ( 11) that circumvents hERG channel binding and poor in vivo potency, issues that limited earlier compounds from our program. However, introduction of the C2-hydroxymethyl group caused 11 to be a substrate for cellular efflux by P-glycoprotein (Pgp).

Kinesin spindle protein (KSP) inhibitors. Part 7: Design and synthesis of 3,3-disubstituted dihydropyrazolobenzoxazines as potent inhibitors of the mitotic kinesin KSP.

Observations from two structurally related series of KSP inhibitors led to the proposal and discovery of dihydropyrazolobenzoxazines that possess ideal properties for cancer drug development. The synthesis and characterization of this class of inhibitors along with relevant pharmacokinetic and in vivo data are presented. The synthesis is highlighted by a key [3+2] cycloaddition to form the pyrazolobenzoxazine core followed by diastereospecific installation of a quaternary center.

Kinesin spindle protein (KSP) inhibitors. Part 4: Structure-based design of 5-alkylamino-3,5-diaryl-4,5-dihydropyrazoles as potent, water-soluble inhibitors of the mitotic kinesin KSP.

Molecular modeling in combination with X-ray crystallographic information was employed to identify a region of the kinesin spindle protein (KSP) binding site not fully utilized by our first generation inhibitors. We discovered that by appending a propylamine substituent at the C5 carbon of a dihydropyrazole core, we could effectively fill this unoccupied region of space and engage in a hydrogen-bonding interaction with the enzyme backbone. This change led to a second generation compound with increased potency, a 400-fold enhancement in aqueous solubility at pH 4, and improved dog pharmacokinetics relative to the first generation compound.

Kinesin spindle protein (KSP) inhibitors. Part 3: synthesis and evaluation of phenolic 2,4-diaryl-2,5-dihydropyrroles with reduced hERG binding and employment of a phosphate prodrug strategy for aqueous solubility.

2,4-Diaryl-2,5-dihydropyrroles have been discovered to be novel, potent and water-soluble inhibitors of KSP, an emerging therapeutic target for the treatment of cancer. A potential concern for these basic KSP inhibitors (1 and 2) was hERG binding that can be minimized by incorporation of a potency-enhancing C2 phenol combined with neutral N1 side chains. Aqueous solubility was restored to these, and other, non-basic inhibitors, through a phosphate prodrug strategy.

Zafirlukast metabolism by cytochrome P450 3A4 produces an electrophilic alpha,beta-unsaturated iminium species that results in the selective mechanism-based inactivation of the enzyme.

Zafirlukast is a leukotriene antagonist indicated for the treatment of mild to moderate asthma, but the drug has been associated with occasional idiosyncratic hepatotoxicity. Structurally, zafirlukast is similar to 3-methylindole because it contains an N-methylindole moiety that has a 3-alkyl substituent on the indole ring. The results presented here describe the metabolic activation of zafirlukast via a similar mechanism to that described for 3-methylindole.

Metabolism of rofecoxib in vitro using human liver subcellular fractions.

The metabolism of rofecoxib, a potent and selective inhibitor of cyclooxygenase-2, was examined in vitro using human liver subcellular fractions. The biotransformation of rofecoxib was highly dependent on the subcellular fraction and the redox system used. In liver microsomal incubations, NADPH-dependent oxidation of rofecoxib to 5-hydroxyrofecoxib predominated, whereas NADPH-dependent reduction of rofecoxib to the 3,4-dihydrohydroxy acid metabolites predominated in cytosolic incubations.

Mechanism-based inhibition of human liver microsomal cytochrome P450 1A2 by zileuton, a 5-lipoxygenase inhibitor.

Zileuton, a 5-lipoxygenase inhibitor, was evaluated as an inhibitor of cytochrome P450 activity in human liver microsomes. In the absence of preincubation, the racemate was found to be a weak inhibitor (IC50 > 100 microM) of phenacetin O-deethylation (POD) (CYP1A2), paclitaxel 6alpha-hydroxylation (CYP2C8), diclofenac 4'-hydroxylation (CYP2C9), (S)-mephenytoin 4'-hydroxylation (CYP2C19), bufuralol 1'-hydroxylation (CYP2D6), testosterone 6beta-hydroxylation (CYP3A4), chlorzoxazone 6-hydroxylation (CYP2E1), and bupropion hydroxylation (CYP2B6). When preincubated with NADPH-fortified human liver microsomes in the absence of substrate, zileuton (racemate) was shown to inhibit POD.

Novel 5-cyclopropyl-1,4-benzodiazepin-2-ones as potent and selective I(Ks)-blocking class III antiarrhythmic agents.

Novel 5-cyclopropyl-1,4-benzodiazepin-2-ones having various N-l substituents were identified as potent and selective blockers of the slowly activating cardiac delayed rectifier potassium current (I(Ks)). Compound 11 is the most potent I(Ks) channel blocker reported to date.