title: Discovery of substituted N-phenyl nicotinamides as potent inducers of apoptosis using a cell- and caspase-based high throughput screening assay.
abstract: By applying a novel cell- and caspase-based HTS assay, a series of N-phenyl nicotinamides has been identified as a new class of potent inducers of apoptosis. Through SAR studies, a 20-fold increase in potency was achieved from a screening hit N-(4-methoxy-2-nitrophenyl)pyridine-3-carboxamide (1) to lead compound 6-methyl-N-(4-ethoxy-2-nitrophenyl)pyridine-3-carboxamide (10), with an EC(50) of 0.082 microM in the caspase activation assay in T47D breast cancer cells. The N-phenyl nicotinamides also were found to be active in the growth inhibition assay where compound 10 had a GI(50) value of 0.21 microM in T47D cells. More importantly, compound 10 was found to be equipotent in MES-SA cells and paclitaxel-resistant, p-glycoprotein overexpressed MES-SA/DX5 cells. Compounds 1 and 6-chloro-N-(4-ethoxy-2-nitrophenyl)pyridine-3-carboxamide (8), a more potent analogue, were found to arrest T47D cells in G(2)/M phase of the cell cycle followed by induction of apoptosis as measured by flow cytometry. Compound 8, which was more potent than 1 in the caspase activation assay, also was found to be more potent in G(2)/M arrest and apoptosis assay. These data confirm that the cell-based caspase activation assay is useful for screening for inducers of apoptosis, as well as for SAR studies and lead optimization. Upon further characterization, N-phenyl nicotinamides were found to be inhibitors of microtubule polymerization in vitro. The identification of N-phenyl nicotinamides as a novel series of inducers of apoptosis demonstrates that our cell- and caspase-based HTS assay is useful for the discovery and optimization of potentially novel anticancer agents.
authors.affiliation: Cytovia, Inc., 6650 Nancy Ridge Drive, San Diego, California 92121, USA. scai@maxim.com
authors.forename: Sui Xiong
authors.initials: SX
authors.lastname: Cai
authors.forename: Bao
authors.initials: B
authors.lastname: Nguyen
authors.forename: Shaojuan
authors.initials: S
authors.lastname: Jia
authors.forename: John
authors.initials: J
authors.lastname: Herich
authors.forename: John
authors.initials: J
authors.lastname: Guastella
authors.forename: Sanjeeva
authors.initials: S
authors.lastname: Reddy
authors.forename: Ben
authors.initials: B
authors.lastname: Tseng
authors.forename: John
authors.initials: J
authors.lastname: Drewe
authors.forename: Shailaja
authors.initials: S
authors.lastname: Kasibhatla
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D004354:Drug Screening Assays, Antitumor; D005434:Flow Cytometry; D006801:Humans; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014404:Tubulin / Q000737:chemistry; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D014404:Tubulin; D009536:Niacinamide; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases