Identification, synthesis and evaluation of CSF1R inhibitors using fragment based drug design.

Colony-stimulating factor 1 receptor is a type III receptor protein tyrosine kinase belonging to PDGFR family. CSF1R signaling is essential for differentiation, proliferation and survival of macrophages. Aberrant expression of CSF1R appears to be an attractive target in several cancer types. Higher expression of CSF1R ligands correlates to tumor progression. CSF1R inhibitors have been shown to suppress cancers. We have attempted an in silico fragment derived drug discovery approach by screening ˜25,000 in-house compounds as potential CSF1R inhibitors. Using FBDD approach we have identified six diverse fragments that exhibit affinity towards hinge region of CSF1R. Some of the fragments 5-nitroindole and 7-azaindole and their derivatives were synthesized for further evaluation. The in silico and in vitro enzyme activity studies reveal moderate inhibition of CSF1R kinase activity by 5-nitroindole and good inhibition by 7-azaindole fragments. Bio and chemiinformatics studies have shown that 7-azaindole compounds have better membrane permeability and enzyme inhibition properties. Molecular docking studies show that the amino acid residues 664-666 in the hinge region of the cytosolic domain of CSF1R to be the preferred region of binding for nitroindole and azaindole derivatives. Further optimization and biological analysis would identify these fragments as potential and promising leads as CSF1R inhibitors.

Regioselective synthesis, antimicrobial evaluation and theoretical studies of 2-styryl quinolines.

2-Styryl quinolines (9a-l) have been synthesized regioselectively from 2-methyl-quinoline by using NaOAc in water acetic acid binary solvents and evaluated for their antibacterial activity against both Gram-positive and Gram-negative strains. Among these, the compounds 12 and 8 were found to be active against both bacterial strains. Compounds 9b, 9f, 9g, 9i, 9j and 9k were the most active among the series exhibiting MIC values ranging between 1.9 and 31.2 µg ml(-1) against different bacterial strains. Compounds 9j and 9k were found to be as potent as the standard drug ciprofloxacin against Micrococcus luteus, Klebsiella planticola and Staphylococcus aureus. In addition, the compounds showed bactericidal activity; compound 9j was found to be better than ciprofloxacin, with an MBC value of 0.9 µg ml(-1) against both M. luteus and K. planticola. The compounds also inhibited biofilm formation, and compound 9j was found to be equipotent to erythromycin against M. luteus and S. aureus MLS16. Further, theoretical studies such as those on druggable properties and PMI plot have been carried out.

Development of α-glucosidase inhibitors by room temperature C-C cross couplings of quinazolinones.

Novel quinazolinone based α-glucosidase inhibitors have been developed. For this purpose a virtual screening model has been generated and validated utilizing acarbose as a α-glucosidase inhibitor. Homology modeling, docking, and virtual screening were successfully employed to discover a set of structurally diverse compounds active against α-glucosidase. A search of a 3D database containing 22,500 small molecules using the structure based virtual model yielded ten possible candidates. All ten candidates were N-3-pyridyl-2-cyclopropyl quinazolinone-4-one derivatives, varying at the 6 position. This position was modified by Suzuki-Miyaura cross coupling with aryl, heteroaryl, and alkyl boronic acids. A catalyst screen was performed, and using the best optimal conditions, a series of twenty five compounds was synthesized. Notably, the C-C cross coupling reactions of the 6-bromo-2-cyclopropyl-3-(pyridyl-3-ylmethyl)quinazolin-4(3H)-one precursor have been accomplished at room temperature. A comparison of the relative reactivities of 6-bromo and 6-chloro-2,3-disubstituted quinazolinones with phenyl boronic acid was conducted. An investigation of pre-catalyst loading for the reaction of the 6-bromo-2-cyclopropyl-3-(pyridyl-3-ylmethyl)quinazolin-4(3H)-one substrate was also carried out. Finally, we submitted our compounds to biological assays against α-glucosidase inhibitors. Of these, three hits (compounds 4a, 4t and 4r) were potentially active as α-glucosidase inhibitors and showed activity with IC50 values <20 µM. Based on structural novelty and desirable drug-like properties, 4a was selected for structure-activity relationship study, and thirteen analogs were synthesized. Nine out of thirteen analogs acted as α-glucosidase inhibitors with IC50 values <10 µM. These lead compounds have desirable physicochemical properties and are excellent candidates for further optimization.

Virtual screening studies on HIV-1 reverse transcriptase inhibitors to design potent leads.

The purpose of this study is to identify novel and potent inhibitors against HIV-1 reverse transcriptase (RT). The crystal structure of the most active ligand was converted into a feature-shaped query. This query was used to align molecules to generate statistically valid 3D-QSAR (r(2) = 0.873) and Pharmacophore models (HypoGen). The best HypoGen model consists of three Pharmacophore features (one hydrogen bond acceptor, one hydrophobic aliphatic and one ring aromatic) and further validated using known RT inhibitors. The designed novel inhibitors are further subjected to docking studies to reduce the number of false positives. We have identified and proposed some novel and potential lead molecules as reverse transcriptase inhibitors using analog and structure based studies.

Insilico studies on anthrax lethal factor inhibitors: pharmacophore modeling and virtual screening approaches towards designing of novel inhibitors for a killer.

Bacillus anthracis is a causative organism of anthrax. The main reason to use anthrax as a bioweapon is the combination of the spore's durability and the lethal toxaemia of the vegetative stage. In anthrax infection, lethal factor (LF) is playing crucial role in causing cell death, by inhibiting pathways that rely on this kinase family. The combination of vaccine and antibiotics is preferred as an effective treatment for this target. Till date, no small molecule inhibitor is identified as a drug on the target. In this study, we have performed pharmacophore modeling and docking studies to identify a novel small molecule inhibitor to target the Anthrax LF. The best pharmacophore model is used to screen approximately 2M drug-like small molecule database and yielded 2543 hits. Docking studies of the pharmacophore hits on to the active site of Anthrax LF resulted 120 structurally diverse hits. Out of 120 hits, based on synthetic feasibility, 17 hits are selected for further synthesis and pharmacological screening. In due course, we will publish the updated results.

Combined pharmacophore and structure-guided studies to identify diverse HSP90 inhibitors.

Heat Shock Protein 90 (HSP90), an ATP-dependent molecular chaperone, has emerged as a promising target in the treatment of cancer. Inhibition of HSP90 represents a new target of antitumor therapy, since it may influence many specific signaling pathways. Many HSP90 inhibitors bind to the ATP-binding pocket, inhibit chaperone function, resulting in cell death. Recent clinical trials for treatment of cancer have put HSP90's importance into focus and have highlighted the need for full scale research into HSP90 related pathways. Here we report five novel HSP90 inhibitors which were identified by using pharmacophore models and docking studies. We used highly discriminative pharmacophore model as a 3D query to search against database of approximately 1 M compounds and cluster analysis results yielded 455 compounds which were further subjected for docking. Glide docking studies suggested 122 compounds as in silico hits and these compounds were further selected for the cytotoxicity assay in the HSP90-over expressing SKBr3 cell line. Of the 122 compounds tested, 5 compounds inhibited cell growth with an IC(50) value less than 50 microM.