Discovery of 2-(1H-indol-5-ylamino)-6-(2,4-difluorophenylsulfonyl)-8-methylpyrido[2,3-d]pyrimidin-7(8H)-one (7ao) as a potent selective inhibitor of Polo like kinase 2 (PLK2).

Several families of protein kinases have been shown to play a critical role in the regulation of cell cycle progression, particularly progression through mitosis. These kinase families include the Aurora kinases, the Mps1 gene product and the Polo Like family of protein kinases (PLKs). The PLK family consists of five members and of these, the role of PLK1 in human cancer is well documented. PLK2 (SNK), which is highly homologous to PLK1, has been shown to play a critical role in centriole duplication and is also believed to play a regulatory role in the survival pathway by physically stabilizing the TSC1/2 complex in tumor cells under hypoxic conditions. As a part of our research program, we have developed a library of novel ATP mimetic chemotypes that are cytotoxic against a panel of cancer cell lines. We show that one of these chemotypes, the 6-arylsulfonyl pyridopyrimidinones, induces apoptosis of human tumor cell lines in nanomolar concentrations. The most potent of these compounds, 7ao, was found to be a highly specific inhibitor of PLK2 when profiled against a panel of 288 wild type, 55 mutant and 12 lipid kinases. Here, we describe the synthesis, structure activity relationship, in vitro kinase specificity and biological activity of the lead compound, 7ao.

Discovery of 8-cyclopentyl-2-[4-(4-methyl-piperazin-1-yl)-phenylamino]-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidine-6-carbonitrile (7x) as a potent inhibitor of cyclin-dependent kinase 4 (CDK4) and AMPK-related kinase 5 (ARK5).

The success of imatinib, a BCR-ABL inhibitor for the treatment of chronic myelogenous leukemia, has created a great impetus for the development of additional kinase inhibitors as therapeutic agents. However, the complexity of cancer has led to recent interest in polypharmacological approaches for developing multikinase inhibitors with low toxicity profiles. With this goal in mind, we analyzed more than 150 novel cyano pyridopyrimidine compounds and identified structure-activity relationship trends that can be exploited in the design of potent kinase inhibitors. One compound, 8-cyclopentyl-2-[4-(4-methyl-piperazin-1-yl)-phenylamino]-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidine-6-carbonitrile (7x), was found to be the most active, inducing apoptosis of tumor cells at a concentration of approximately 30-100 nM. In vitro kinase profiling revealed that 7x is a multikinase inhibitor with potent inhibitory activity against the CDK4/CYCLIN D1 and ARK5 kinases. Here, we report the synthesis, structure-activity relationship, kinase inhibitory profile, in vitro cytotoxicity, and in vivo tumor regression studies by this lead compound.

Design, synthesis, and biological evaluation of (E)-N-aryl-2-arylethenesulfonamide analogues as potent and orally bioavailable microtubule-targeted anticancer agents.

A series of novel (E)-N-aryl-2-arylethenesulfonamides (6) were synthesized and evaluated for their anticancer activity. Some of the compounds in this series showed potent cytotoxicity against a wide spectrum of cancer cell-lines (IC50 values ranging from 5 to 10 nM) including all drug resistant cell-lines. Nude mice xenograft assays with compound (E)-N-(3-amino-4-methoxyphenyl)-2-(2',4',6'-trimethoxyphenyl)ethenesulfonamide (6t) showed dramatic reduction in tumor size, indicating their in vivo potential as anticancer agents. A preliminary drug development study with compound 6t is predicted to have increased blood-brain barrier permeability relative to many clinically used antimitotic agents. Mechanistic studies indicate that 6t and some other analogues disrupted microtubule formation, formation of mitotic spindles, and arrest of cells in mitotic phase. Compound 6t inhibited purified tubulin polymerization in vitro and in vivo and circumvented drug resistance mediated by P-glycoprotein. Compound 6t specifically competed with colchicine binding to tubulin and with similar avidity as podophylltoxin, indicating its binding site on tubulin.

Design, synthesis, and biological evaluation of 1-(4-sulfamylphenyl)-3-trifluoromethyl-5-indolyl pyrazolines as cyclooxygenase-2 (COX-2) and lipoxygenase (LOX) inhibitors.

A series of 20 novel 1-(4-sulfamylphenyl)-3-trifluoromethyl-5-indolyl pyrazolines were designed, synthesized, and screened in vitro for anti-inflammatory activity. These compounds were designed for evaluation as dual inhibitors of cyclooxygenases (COX-1 and COX-2) and lipoxygenases (LOX-5, LOX-12, and LOX-15) that are responsible for inflammation and pain. All pyrazoline molecules prepared are optically active and compounds that are more potent in COX-2 inhibitory activity (5a and 5f) were resolved by chiral column and each enantiomer was tested for cyclooxygenase inhibitory activity. Molecular modeling and comparison of molecular models of 5a enantiomers with that of celecoxib model shows that 5a (enantiomer-1) and 5a (enantiomer-2) have more hydrogen bonding interactions in the catalytic domain of COX-2 enzyme than celecoxib. Compounds 5a, 5e, and 5f showed moderate to good LOX-5 and LOX-15 inhibitory activity and this is comparable to that of celecoxib and more potent than rofecoxib.