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Photodynamic therapy (PDT) is a rapidly evolving area of cancer management against solid tumors. PDT is either administrated by injecting photosensitizer (porphyrins) or by accumulation of intracellular protoporphyrin IX via the inhibition of human Protoporphyrinogen Oxidase IX (hPPO). In this study, novel inhibitors of hPPO have been investigated by integrating virtual screening, molecular docking, and molecular dynamics (MD) simulation. A ligand-based pharmacophore was generated from a training set of 22 inhibitors of hPPO. The selected pharmacophore had four chemical features including three hydrogen bond acceptors and one hydrophobic. The pharmacophore was characterized by highest correlation coefficient of 0.96, cost difference of 53.20, and lowest root mean square deviation of 0.73. The resultant pharmacophore was validated by Fischer’s Randomization and Test Set Validation methods. The validated pharmacophore was used as a 3D query to screen chemical databases including NCI, Asinex, Chembridge, and Maybridge. The screening of chemical databases and the subsequent application of Lipinski’s Rule of Five, and ADMET Assessment Test, retrieved 1176 drug-like compounds. The drug-like compounds were subjected to molecular docking studies in the active site of hPPO to eliminate false positive hits and to elucidate their true binding orientation. Top three candidate molecules with high docking scores and hydrogen bond interactions with catalytic active residues were selected as best candidate inhibitors against hPPO. The binding stability of selected candidate inhibitors was evaluated by MD simulation. The MD simulation of hits portrayed strong hydrogen bonds and key hydrophobic interactions with catalytic active residues of hPPO including R59, R97, G159, G332 and flavin moiety of FAD (coenzyme of hPPO). Our study predicts three hit compounds against hPPO, which could possibly accumulate high concentration of protoporphyrinogen-IX, and thereby acting as an intracellular photosensitizer against tumor cells through photodynamic therapy. Keywords: Photodynamic therapy (PDT), hPPO Inhibition, Virtual screening, Pharmacophore modeling, Molecular docking simulation, Molecular dynamics (MD) simulation

Prolyl oligopeptidase (POP) is a potential therapeutic target for treatment of several neurological disorders and α-synucleinopathies including Parkinson's disease. Most of the known POP inhibitors failed in the clinical trials due to poor pharmacokinetic properties and blood-brain impermeability. Therefore, a training set of 30 structurally diverse compounds with a wide range of inhibitory activity against POP was used to generate a quantitative pharmacophore model, Hypo 3, to identify potential POP inhibitors with desirable drug-like properties. Validations through test set, cost analysis, and Fisher's randomization methods proved that Hypo 3 accurately predicted the known inhibitors among inactive compounds. Hypo 3 was employed as 3D query for virtual screening on an in-house drug-like chemical database containing compounds with good brain permeability and ADMET parameters. Database screening with Hypo 3 resulted in 99 compounds that were narrowed down to 21 compounds through molecular docking. Among them, five compounds were identified in our earlier studies, while two compounds showed in vitro POP inhibition. The current study proposed new 16 virtually screened compounds as potential inhibitors against POP that possess Gold docking score in the range of 64.61–75.74 and Chemscore of −32.25 to −38.35. Furthermore, the top scoring four hit compounds were subjected to molecular dynamics simulations to reveal their appropriate binding modes and assessing binding free energies. The hit compounds interacted with POP effectively via hydrogen bonds with important active site residues along with hydrophobic interactions. Moreover, the hit compounds had key inter-molecular interactions and better binding free energies as compared to the reference inhibitor. A potential new hydrogen bond interaction was discovered between Hit 2 with the Arg252 residue of POP. To conclude, we propose four hit compounds with new structural scaffolds against POP for the lead development of POP-based therapeutics for neurological disorders.

Globally, breast cancer is one of the primary reasons of death noticed in women. Despite continuous efforts to formulate effective treatments, search to identify promising therapeutics is underway. Consequently, a drug with low toxicity, high efficacy, and which can escape resistance mechanism is in a high demand. Natural compounds are bestowed with several medicinal properties demonstrating low toxicity. Therefore, the current research focuses on the use of several plant- derived chemical compounds against aromatase, a validated drug target for breast cancer. Correspondingly, employing the known inhibitors, a 3D QSAR pharmacophore model was generated and was subsequently validated. Using the three-featured pharmacophore as the 3D query, the alkaloids, flavonoids, coumarins and the AfroDB were scrupulously examined to retrieve the compounds with inhibitory activities complemented by the pharmacophore model. The obtained compounds were subjected to molecular docking studies executed employing the Cdocker accessible on discovery studio v4.5. The resultant ideal poses from the largest cluster conferred with key reside interactions and higher dock scores than the reference and the Food and Drug Administration (FDA) approved drugs were escalated to molecular dynamics simulation studies conducted employing GROMACS v5.0.6 for 30 ns. Correspondingly, the Hits (ZINC95486358, ZINC95486354, and ZINC90711737) have displayed stable root mean square deviations, coupled by appropriate positioning at the active site displaying greater number of hydrogen bonds. Moreover, the Hits (ZINC95486358, ZINC95486354, and ZINC90711737) were noticed to anchor with various key residues essential for clamping the ligand at the binding pocket. Therefore, these findings guide us to determine that the identified Hits can act effectively against breast cancer, thereby increasing the life expectancy. Furthermore, they can assist as scaffolds for designing novel drugs that aid in curing the cancer.

ACK1, an intracellular non-receptor tyrosine kinase when abnormally activated and amplified causes numerous sorts of human cancers, therefore, act as a major target of cancer drug development. Currently, there are very small numbers of inhibitors reported for ACK1 inhibition and none of them are in clinical trials. In this study, to identify potential ACK1 inhibitors, a small dataset was prepared from already known inhibitors as a training set for ligand-based pharmacophore model generation using the Hip-Hop algorithm available in the Discovery Studio. Selected pharmacophore hypothesis, Hypo1 displayed the highest rank and consists of five features including two hydrogen bond acceptors (HBA), two-ring aromatic (RA) and one hydrophobic (HYP). Hypo1 was further validated by Receiver Operating Characteristic (ROC) curve and Guner-Henry (GH) approach which give an ROC value of 0.92 and highest GH score of 0.78. Drug-like database was generated from ZINC, ANX, NCI and Princeton database using Lipinski's rule of five and ADMET descriptors. Validated Hypo1 was used for searching new potential hit compounds from the generated drug-like database. From molecular docking analysis, ten potential inhibitor compounds were selected on the basis of Goldscore >67.72, the score of reference inhibitor Dasatinib. Furthermore, molecular dynamics simulation study was performed to study the stability of docking conformations. Subsequently, molecular dynamics simulation analyses revealed that the Hit1 and Hit2 compounds have desirable molecular interaction with key residues Thr205 and Ala208 in the hinge region of ACK1 with better binding affinity. Finally, various pharmacokinetic properties over the Hit1 and Hit2 compounds were analyzed using pkCSM tool and it was found that our hit compounds have shown comparable results with reference. Therefore, we propose the Hit1 and Hit2 compounds may be crucial against ACK1 as potential anticancer agents subjected to experimental validation.

Breast cancer is one of the common causes of death noticed in women globally. In order to find effective therapeutics, the current investigation has focussed on identifying candidate compounds for EGFR and HER2. Accordingly, the pharmacophore modelling approaches were adapted to identify two prospective compounds and were docked against the target 3RCD that is complexed with TAK-285 a known dual inhibitor. Focussing on the target 3RCD, our results have showed that the compounds have demonstrated a good binding affinity towards the target occupying the binding pocket. They have established key residue interactions with stable molecular dynamics simulation results. The Hit compounds have demonstrated a potential to penetrate the blood brain barrier thereby enriching their therapeutics towards breast cancer brain metastasis. Taken together, our findings propose two candidate compounds as EGFR/HER2 inhibitors that might serve as novel chemical spaces for designing and developing new inhibitors.