Discovery of substituted N-phenyl nicotinamides as potent inducers of apoptosis using a cell- and caspase-based high throughput screening assay.
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.
Cai
Sui Xiong
SX
Cytovia, Inc., 6650 Nancy Ridge Drive, San Diego, California 92121, USA. scai@maxim.com
Nguyen
Bao
B
Jia
Shaojuan
S
Herich
John
J
Guastella
John
J
Reddy
Sanjeeva
S
Tseng
Ben
B
Drewe
John
J
Kasibhatla
Shailaja
S
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
D000970:Antineoplastic Agents; D014404:Tubulin; D009536:Niacinamide; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases