Nigel J. Liverton

Nonpeptide glycoprotein IIb/IIIa inhibitors: substituted quinazolinediones and quinazolinones as potent fibrinogen receptor antagonists.

The synthesis and biological activity of a series of 3,6-substituted quinazolinediones and quinazolinones are described. The potent activity of these compounds as platelet aggregation inhibitors demonstrates the utility of these structures as central templates for nonpeptide RGD mimics.

Serum-induced monocyte differentiation and monocyte chemotaxis are regulated by the p38 MAP kinase signal transduction pathway.

Regulation by the p38 mitogen‐activated protein (MAP) kinase signaling pathway of monocytic inflammatory functions was evaluated using L‐790,070, a potent and selective inhibitor of p38 MAP kinase. Three major functions of monocytes were investigated: differentiation, chemotaxis, and phagocytosis. L‐790,070 inhibited serum‐induced monocyte differentiation with an IC50 of 0.5 nM. Monocyte chemotaxis induced by RANTES, macrophage inflammatory protein‐1α (MIP‐1α), monocyte chemotactic protein‐1 (MCP‐1), and fMLP were all sensitive to L‐790,070. When titrated, L‐790,070 inhibited MCP‐1‐induced chemotaxis in a concentration‐dependent manner with an IC50 of 0.3 nM. However, the ability of serum‐derived macrophages to phagocytose apoptotic neutrophils was unaffected by L‐790,070. The concentration with which L‐790,070 inhibited both differentiation and chemotaxis was similar to that necessary to inhibit p38 MAP kinase activation of MAPKAP kinase (0.3 nM) in response to stimulation by lipopolysaccharide. Therefore, the data in this report suggest that the mechanism by which L‐790,070 blocked monocyte differentiation and prevented chemotaxis was by inhibiting p38 MAP kinase activity. J. Leukoc. Biol. 67: 869–875; 2000.

Orally Efficacious NR2B-Selective NMDA Receptor Antagonists

A novel series of benzamidines was synthesized and shown to exhibit NR2B-subtype selective NMDA antagonist activity. Compound 31 is orally active in a carrageenan-induced rat hyperalgesia model of pain and shows no motor coordination side effects.

Sustained Viral Response in a Hepatitis C Virus-Infected Chimpanzee via a Combination of Direct-Acting Antiviral Agents

ABSTRACT Efforts to develop novel, interferon-sparing therapies for treatment of chronic hepatitis C (HCV) infection are contingent on the ability of combination therapies consisting of direct antiviral inhibitors to achieve a sustained virologic response. This work demonstrates a proof of concept that coadministration of the nucleoside analogue MK-0608 with the protease inhibitor MK-7009, both of which produced robust viral load declines as monotherapy, to an HCV-infected chimpanzee can achieve a cure of infection.

Pyridazine based inhibitors of p38 MAPK

Trisubstituted pyridazines were synthesized and evaluated as in vitro inhibitors of p38MAPK. The most active isomers were those possessing an aryl group alpha and a heteroaryl group beta relative to the nitrogen atom in the 2-position of the central pyridazine. Additionally, substitution in the 6-position of the central pyridazine with a variety of dialkylamino substituents afforded a set of inhibitors having good (p38 IC50 1-20 nM) in vitro activity.

Preparation of 3-amino-1,4-benzodiazepin-2-ones via direct azidation with trisyl azide

Abstract An efficient synthesis of 3-amino-1,4-benzodiazepin-2-ones utilizing triisopropylbenzenesulfonyl azide (trisyl azide) for the direct azidation of 1,4-benzodiazepin-2-ones is described.

P2‐Quinazolinones and Bis‐Macrocycles as New Templates for Next‐Generation Hepatitis C Virus NS3/4a Protease Inhibitors: Discovery of MK‐2748 and MK‐6325

With the goal of identifying inhibitors of hepatitisu2005C virus (HCV) NS3/4a protease that are potent against a wide range of genotypes and clinically relevant mutant viruses, several subseries of macrocycles were investigated based on observations made during the discovery of MK‐5172. Quinazolinone‐containing macrocycles were identified as promising leads, and optimization for superior cross‐genotype and mutant enzyme potency as well as rat liver and plasma concentrations following oral dosing, led to the development of MK‐2748. Additional investigation of a series of bis‐macrocycles containing a fused 18‐ and 15‐membered ring system were also optimized for the same properties, leading to the discovery of MK‐6325. Both compounds display the broad genotype and mutant potency necessary for clinical development as next‐generation HCV NS3/4a protease inhibitors.

Phosphorous acid analogs of novel P2-P4 macrocycles as inhibitors of HCV-NS3 protease.

HCV-NS3 protease is essential for viral replication and NS3 protease inhibitors have shown proof of concept in clinical trials. Novel P2-P4 macrocycle inhibitors of NS3/4A comprising a P1 C-terminal carboxylic acid have recently been disclosed. A series of analogs, in which the carboxylic residue is replaced by phosphorous acid functionalities were synthesized and found to be inhibitors of the NS3 protease. Among them the methylphosphinate analogue showed nanomolar level of enzyme inhibition and sub-micromolar potency in the replication assay.

Kinetic characterization of novel NR2B antagonists using fluorescence detection of calcium flux.

To facilitate the discovery of novel N-methyl-d-aspartate (NMDA) receptor antagonists, we have developed a high-throughput functional assay based on fluorescence detection of free intracellular calcium concentrations. Mouse fibroblast L(tk-) cells expressing human NR1a/NR2B NMDA receptors were plated in 96-well plates and loaded with fluorescence calcium indicator fluo-3 AM. NR2B antagonists were added after stimulation of NMDA receptors with 10 microM glutamate and 10 microM glycine. Changes in fluorescence after the addition of the antagonists were fitted by a single exponential equation providing k(obs). The concentration dependence of k(obs) was linear for all NR2B antagonists at concentrations where k(obs) < 0.2 s(-1). The values of k(obs) for six structurally distinct NR2B antagonists were in the range of 1.1 to 7.5 x 10(5) M(-1)s(-1). These values were several orders of magnitude slower than that obtained for diffusion limited Mg(2+) channel block. The rate constants k(off) provided the values of t(1/2) for dissociation of NR2B antagonists in the range of 1.8 min for ifenprodil to 240 min for the slowest novel antagonist. The IC(50) values obtained from the end-point fluorescence measurements agree with K(d) values calculated from kinetic measurements. All kinetic constants, obtained using our fluorescence method, correlate well with data measured by voltage clamp.

Novel 5-cyclopropyl-1,4-benzodiazepin-2-ones as potent and selective IKs-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.