Synthesis and evaluation of antitumoral activity of ester and amide derivatives of 2-arylamino-6-trifluoromethyl-3-pyridinecarboxylic acids

Pyridine: the scaffolds with significant clinical diversity

The nitrogen-bearing heterocycle pyridine in its several analogous forms occupies an important position as a precious source of clinically useful agents in the field of medicinal chemistry research. This privileged scaffold has been consistently incorporated in a diverse range of drug candidates approved by the FDA (Food and Drug Administration). This moiety has attracted increasing attention from several disease states owing to its ease of parallelization and testing potential pertaining to the chemical space. In the next few years, a larger share of novel pyridine-based drug candidates is expected. This review unifies the current advances in novel pyridine-based molecular frameworks and their unique clinical relevance as reported over the last two decades. It highlights an inclination to the use of pyridine-based molecules in drug crafting and the subsequent emergence of several potent and eligible candidates against a range of diversified diseases.

The nitrogen-bearing heterocycle pyridine in its several analogous forms occupies an important position as a precious source of clinically useful agents in the field of medicinal chemistry research.

2-(Arylamino)-6-(trifluoromethyl)nicotinic Acid Derivatives: New HIV-1 RT Dual Inhibitors Active on Viral Replication

The persistence of the AIDS epidemic, and the life-long treatment required, indicate the constant need of novel HIV-1 inhibitors. In this scenario the HIV-1 Reverse Transcriptase (RT)-associated ribonuclease H (RNase H) function is a promising drug target. Here we report a series of compounds, developed on the 2-amino-6-(trifluoromethyl)nicotinic acid scaffold, studied as promising RNase H dual inhibitors. Among the 44 tested compounds, 34 inhibited HIV-1 RT-associated RNase H function in the low micromolar range, and seven of them showed also to inhibit viral replication in cell-based assays with a selectivity index up to 10. The most promising compound, 21, inhibited RNase H function with an IC50 of 14 µM and HIV-1 replication in cell-based assays with a selectivity index greater than 10. Mode of action studies revealed that compound 21 is an allosteric dual-site compound inhibiting both HIV-1 RT functions, blocking the polymerase function also in presence of mutations carried by circulating variants resistant to non-nucleoside inhibitors, and the RNase H function interacting with conserved regions within the RNase H domain. Proving compound 21 as a promising lead for the design of new allosteric RNase H inhibitors active against viral replication with not significant cytotoxic effects.

New 3-Cyano-2-Substituted Pyridines Induce Apoptosis in MCF 7 Breast Cancer Cells

The synthesis of new 3-cyano-2-substituted pyridines bearing various pharmacophores and functionalities at position 2 is described. The synthesized compounds were evaluated for their in vitro anti-cancer activities on five cancer cell lines using 5-FU as reference compound. The results revealed that the benzohydrazide derivative 9a induced growth inhibition in human breast cancer cell line MCF-7 with an IC₅₀ value of 2 μM and it showed lower cytotoxicity on MCF-12a normal breast epithelial cells. Additionally, 9a induced apoptotic morphological changes and induced apoptosis in MCF-7 in a dose and time-dependent manner according to an enzyme linked immunosorbent apoptosis assay which is further confirmed by a TUNEL assay. Flow cytometric analysis indicated that 9a arrested MCF-7 cells in the G1 phase, which was further confirmed by increased expression of p21 and p27 and reduced expression of CDK2 and CDK4. Western blot data revealed significant upregulation of the expression of p53, Bax, caspase-3 and down-regulation of Bcl-2, Mdm-2 and Akt. Additionally, 9a increased the release of cytochrome c from mitochondria to cytoplasm which provokes the mitochondrial apoptotic pathway while it showed no significant change on the expression of the death receptor proteins procaspase-8, caspase-8 and FAS. Furthermore, 9a reduced the expression of phospho AKT and β-catenin in dose dependent manner while inhibiting the expression of migration-related genes such as matrix metalloproteinase (MMP)-9 and vascular endothelial growth factor (VEGF). Our findings suggest that compound 9a could be considered as a lead structure for further development of more potent apoptosis inducing agents with anti-metastatic activities.

N-aryl-6-methoxy-1,2,3,4-tetrahydroquinolines: a novel class of antitumor agents targeting the colchicine site on tubulin

Structural optimizations of the prior lead 1a led to the discovery of a series of N-aryl-6-methoxy-1,2,3,4-tetrahydroquinoline derivatives as a novel class of tubulin polymerization inhibitors targeted at the colchicine binding site. The most active compound 6d showed extremely high cytotoxicity against a human tumor cell line panel (A549, KB, KBvin, and DU145) with GI50 values ranging from 1.5 to 1.7 nM, significantly more potent than paclitaxel, especially against the drug-resistant KBvin cell line, in the same assays. Analogs 5f, 6b, 6c, and 6e were also quite potent, with a GI50 range of 0.011-0.19 μM. In further studies, active compounds 6b-e and 5f significantly inhibited tubulin assembly, with IC50 values of 0.92-1.0 μM and strongly inhibited colchicine binding to tubulin, with inhibition rates of 75-99% (at 5 μM), comparable with or more potent than combretastatin A-4 (IC50 0.96 μM). Current studies included design, synthesis, and biological evaluations of 24 new compounds (series 3-6). Related SAR analysis, molecular modeling, and evaluation of essential drug-like properties, i.e. water solubility, log P, and in vitro metabolic stability, were also performed.

Synthesis and biological evaluation of N-alkyl-N-(4-methoxyphenyl)pyridin-2-amines as a new class of tubulin polymerization inhibitors

Based on our prior antitumor hits, 32 novel N-alkyl-N-substituted phenylpyridin-2-amine derivatives were designed, synthesized and evaluated for cytotoxic activity against A549, KB, KB(VIN), and DU145 human tumor cell lines (HTCL). Subsequently, three new leads (6a, 7g, and 8c) with submicromolar GI(50) values of 0.19-0.41 μM in the cellular assays were discovered, and these compounds also significantly inhibited tubulin assembly (IC(50) 1.4-1.7 μM) and competitively inhibited colchicine binding to tubulin with effects similar to those of the clinical candidate CA-4 in the same assays. These promising results indicate that these tertiary diarylamine derivatives represent a novel class of tubulin polymerization inhibitors targeting the colchicine binding site and showing significant anti-proliferative activity.

Anticancer activity of N-bis(trifluoromethyl)alkyl-N'-(polychlorophenyl) and N'-(1,2,4-triazolyl) ureas

A number of N-bis(trifluoromethyl)alkyl-N'-substituted ureas have been synthesized and evaluated for their in vitro anticancer activity against the human cancer cell lines at the National Cancer Institute (NCI, USA). Marked activity was shown for compounds 4a and 5a. The most sensitive cell lines relative to the tested compounds were: 4a UO-31 (renal cancer, logGI(50) -5.62), HS 578T (breast cancer, logGI(50) -5.50), 5a HCC-2998 (colon cancer, logGI(50) -5.94), NCI-H322M (lung cancer, logGI(50) -5.75) and PC-3 (prostate cancer, logGI(50) -5.66).