Discovery of potential ALK inhibitors by virtual screening approach

Crizotinib is an anticancer drug used for the treatment of non-small cell lung cancer. Evidences available suggest that there is a development of an acquired resistance against crizotinib action due to the emergence of several mutations in the ALK gene. It is therefore necessary to develop potent anti-cancer drugs for the treatment of crizotinib resistance non-small cell lung cancer types. In the present study, a novel class of lead molecule was identified using virtual screening, molecular docking and molecular dynamic approach. The virtual screening analysis was done using PubChem database by employing crizotinib as query and the data reduction was carried out by using molecular docking techniques. The bioavailability of the lead compounds was examined with the help of Lipinski rule of five. The screened lead molecules were analyzed for toxicity profiles, drug-likeness and other physico-chemical properties of drugs by OSIRIS program. Finally, molecular dynamics simulation was also performed to validate the binding property of the lead compound. Our analysis clearly indicates that CID 11562217, a nitrile containing compound (pyrazole-substituted aminoheteroaryl), could be the potential ALK inhibitor certainly helpful to overcome the drug resistance in non-small cell lung cancer.

Investigation of Paclitaxel Resistant R306C Mutation in β-Tubulin—A Computational Approach

Paclitaxel is the most effective chemotherapeutic agent used for the treatment of a broad spectrum of solid tumors. However, observed paclitaxel resistance in clinical trials presents one of the major obstacles for cancer chemotherapy. Most importantly, resistance due to β-tubulin mutations (R306C) has been intensely debated in recent years. Despite all efforts, mechanism of resistance is still not well understood. In this study, computational techniques were employed to uncover the effect of R306C mutation in the β-tubulin structure and its function. The tools such as I-Mutant, CUPSAT and Fold-X were employed to address the consequence of R306C mutation in the structural stability of β-tubulin. Further, molecular docking and molecular dynamics study was employed to understand the functional impact of β-tubulin mutation. Our results suggest that the R306C mutation causes a significant reduction in the binding affinity between β-tubulin and paclitaxel. Further, docked complex analysis indicates that destruction of conservative hydrogen bond maintained by the residues Arg282 and Gly360 should be responsible for the large conformation changes of the binding pocket in R306C mutant. Finally, molecular dynamics simulations study confirms the stable binding of paclitaxel with native type β-tubulin structure rather than mutant (R306C) type. We certainly believe that this study will provide useful guidance for the development of novel inhibitors that are less susceptible to drug resistance.

Discovery of a potential lead compound for treating leprosy with dapsone resistance mutation in M. leprae folP1

A potential lead compound to overcome dapsone resistance in M. leprae folP1 was identified by a virtual screening strategy.

Molecular level understanding of resistance to nalidixic acid in Salmonella enteric serovar typhimurium associates with the S83F sequence type

Nalidixic acid is an antibiotic drug used for treatment of Salmonellosis, a gastrointestinal infection. DNA gyrase subunit A (GyrA) of Salmonella typhimurium is the drug target for nalidixic acid. Resistance of GyrA to nalidixic acid, because of a point mutation in S. typhimurium, was recently reported. Substitution of Phe in place of Ser at locus 83 in GyrA of S. typhimurium has been experimentally associated with nalidixic acid resistance. Despite recent efforts, the mechanism of this resistance is not well understood. In this investigation we used computational techniques to address this shortcoming. Our results showed that contact with residue Arg 91 is certainly important for efficient binding of nalidixic acid to the target protein, and that mutation of this residue results in 180° rotation of the antibiotic in its binding pocket, around its own long axis. It is hoped these findings may enable development of new antibiotics against resistant forms of Salmonella.

Computational identification of significant missense mutations in AKT1 gene

The AKT1 gene is of supreme importance in cell signaling and human cancer. In the present study, we aim to understand the phenotype variations that were believed to have the highest impact in AKT1 gene by different computational approaches. The analysis was initiated with SIFT tool followed by PolyPhen 2.0, I-Mutant 2.0, and SNPs&GO tools with the aid of 22 nonsynonymous (nsSNPs) retrieved from dbSNP. A total of five AKT1 variants such as E17K, E17S, E319G, L357P, and P388T are found to exert deleterious effects on the protein structure and function. Furthermore, the molecular docking study indicates the lesser binding affinity of inhibitor with the mutant structure than the native type. In addition, root mean square deviation and hydrogen bond details were also analyzed in the 10 ns molecular dynamics simulation study. These computational evidences suggested that E17K, E17S, E319G, L357P, and P388T variants of AKT1 could destabilize the protein networks, thus causing functional deviations of protein to some extent. Moreover, the findings strongly indicate that screening for AKT1, E17K, E17S, E319G, L357P, and P388T variants may be useful for disease molecular diagnosis and also to design the potential AKT inhibitors.

Analyzing resistance pattern of non-small cell lung cancer to crizotinib using molecular dynamic approaches

Crizotinib is the potential anticancer drug used for the treatment of non-small cell lung cancer (NSCLC) approved by FDA in 2011. The main target for the crizotinib is anaplastic lymphoma kinase (ALK). Evidences available indicate that double mutant ALK (L1196M and G1269A) confers resistance to crizotinib. However, how mutation confers drug resistance is not well-understood. Hence, in the present study, molecular dynamic (MD) simulation approach was employed to study the impact of crizotinib binding efficacy with ALK structures at a molecular level. Docking results indicated that ALK double mutant (L1196M and G1269A) significantly affected the binding affinity for crizotinib. Furthermore, MD studies revealed that mutant ALK-crizotinib complex showed higher deviation, higher fluctuation and decreased number of intermolecular H-bonds, when compared to the native ALK-crizotinib complex. These results may be immense importance for the molecular level understanding of the crizotinib resistance pattern and also for designing potential drug molecule for the treatment of lung cancer.

Insight into the oseltamivir resistance R292K mutation in H5N1 influenza virus: a molecular docking and molecular dynamics approach

H5N1 is a subtype of the influenza A virus that can cause disease in humans and many other animal species. Oseltamivir (Tamiflu) is a potent and selective antiviral drug employed to fight the flu virus in infected individuals by inhibiting neuraminidase (NA), a flu protein responsible for the release and spread of the progeny virions. However, oseltamivir resistance has become a critical problem. In particular, influenza strains with a R292K NA mutation are highly resistant to the oseltamivir. Though the biological functions of the mutations have previously been characterized, the structural basis behind the reduced catalytic activity and reduced protein level is not clear. In this study, molecular docking and molecular dynamics (MD) approach were employed to investigate the structural and dynamical effects throughout the protein structure and specifically, at the drug-binding pocket. Furthermore, potential of mean force was analyzed using explicit solvent MD simulations with the umbrella sampling method to explore the free energy of binding. It is believed that this study provides valuable guidance for the resistance management of oseltamivir and designing of more potent antiviral inhibitor.

Discovery of Potential, Non-Toxic Influenza Virus Inhibitor by Computational Techniques

Influenza infection continues to be a major problem in many parts of the world. Rimantadine is a first-line drug used to treat the influenza infection by targeting M2 proton channel. However, S31N mutation in M2 proton channel diminishes the efficiency of rimantadine and creates resistance. To address this issue, the present study was aimed to screen the effective lead candidate against drug resistance strain of influenza from DrugBank database. Initially, the lead molecules were filtered using Lipinski rule of five and the drug likeliness property. Subsequently, the data reduction was carried out by employing molecular docking study. Finally, molecular dynamics simulations techniques were performed to validate the lead compound. Most importantly, the -p LD50 of the screened lead molecule was calculated using CORAL software to estimate the Rat oral toxicity. Accordingly, memantine may possibly become a promising lead compound of rimantadine-resistant influenza virus strain.

Exploring the structural and functional impact of the ALK F1174L mutation using bioinformatics approach

Crizotinib is the most effective and the only drug that has been approved for the treatment of anaplastic lymphoma kinase (ALK)-positive lung cancer. Reports suggest that there is a development of an acquired resistance against crizotinib action due to the emergence of several mutations in the ALK gene and F1174L is one such mutation. In this study, we used molecular docking and molecular dynamics (MD) approach to decipher the effect of F1174L mutation in drug-target binding. Docking results suggest that crizotinib was found to adopt the most promising conformations to the native-type ALK by identifying the M1199 residue as a prospective partner for making a hydrogen bond as compared to the mutant-type ALK. MD results showed that the average atom, especially atoms of the native-type ALK-crizotinib complex, movements were less, displayed less fluctuation, fast convergence of energy, and changes in geometry. This shows the stable binding of crizotinib with the native-type ALK in comparison to the mutant-type ALK. We believe that this study could be useful for the logical design of stronger, more selective, and more consistent ALK inhibitor against drug-resistant F1174L mutation.

Identification of potential inhibitor targeting enoyl-acyl carrier protein reductase (InhA) in Mycobacterium tuberculosis: a computational approach

The explosive global spreading of multidrug resistant Mycobacterium tuberculosis (Mtb) has provoked an urgent need to discover novel anti-TB agents. Enoyl-acyl carrier protein reductase from Mtb is a well-known and thoroughly studied target for anti-tuberculosis therapy. In the present analysis, virtual screening techniques performed from Drug bank database by utilizing INH-NAD adduct as query for the discovery of potent anti-TB agents. About 100 molecules sharing similar scaffold with INH-NAD adduct were analyzed for their binding effectiveness. The initial screening based on number of rotatable bonds gave 42 hit molecules. Subsequently, physiochemical properties such as toxicity, solubility, drug-likeness and drug score were analyzed for the filtered set of compounds. Final data reduction was performed by means of molecular docking and normal mode docking analysis. The result indicates that DB04362, adenosine diphosphate 5-(beta-ethyl)-4-methyl-thiazole-2-carboxylic acid could be a promising lead compound and be effective in treating sensitive as well as drug-resistant strains of Mtb. We believe that this novel scaffolds might be the good starting point for lead compounds and certainly aid the experimental designing of anti-tuberculosis drug in a short time.

An unusual manifestation of Cardiac Sarcoidosis

Non tropical, non hypereosinophilic endo myocardial fibrosis has been reported in literature and is a rare entity.  Cardiac Sarcoidosis manifesting as non-tropical, non hypereosinophilic endomyocardial fibrosis is unknown, though it classically affects the left ventricle and is not associated with specific risk factors. We describe an atypical presentation of sarcoidosis as non-tropical non hypereosinophilic endomyocardial fibrosis in a middle aged female who presented to us with refractory heart failure.

Identification of potential inhibitors of H5N1 influenza A virus neuraminidase by ligand-based virtual screening approach

The neuraminidase (NA) of the influenza virus is the target of antiviral drug, oseltamivir. Recently, cases were reported that influenza virus becoming resistant to oseltamivir, necessitating the development of new long-acting antiviral compounds. In this report, a novel class of lead molecule with potential NA inhibitory activity was identified using a combination of virtual screening (VS), molecular docking, and molecular dynamic approach. The PubChem database was used to perform the VS analysis by employing oseltamivir as query. Subsequently, the data reduction was carried out by employing molecular docking study. Furthermore, the screened lead molecules were analyzed with respect to the Lipinski rule of five, drug-likeness, toxicity profiles, and other physico-chemical properties of drugs by suitable software program. Final screening was carried out by normal mode analysis and molecular dynamic simulation approach. The result indicates that CID 25145634, deuterium-enriched oseltamivir, become a promising lead compound and be effective in treating oseltamivir sensitive as well as resistant influenza virus strains.