An In-silico Approach: Design, Homology Modeling, Molecular Docking, MM/GBSA Simulations, and ADMET Screening of Novel 1,3,4-oxadiazoles as PLK1inhibitors

Background: Breast cancer is the most commonly diagnosed and major cause of cancer-related deaths in women worldwide. Disruption of the normal regulation of cell cycle progression and proliferation are the major events leading to cancer. Human Polo-like Kinase 1 (PLK1) plays an important role in the regulation of cellular division. High PLK1 expression is observed in various types of cancer including breast cancer. 1,3,4-oxadiazoles are the fivemembered heterocycles, that serve as versatile lead molecules for designing novel anticancer agents and they mainly act by inhibiting various enzymes and kinases. Objective: A novel series of 1,3,4-oxadiazole derivatives (A1-A26) were designed and subjected to an in-silico analysis against PLK1 enzyme (PDB ID:1q4k), targeting breast cancer. Methods: The chemical structure of each compound (A1-26) was drawn using ChemDraw software. The 3D structure model of protein target (PDB ID:1q4k) was built using the SWISSMODEL server. Molecular docking simulation was performed to determine the designed compound’s probable binding mode and affinity towards the protein target (PDB ID:1q4k). The designed compounds were subjected to ADME screening, as well as Prime MM/GBSA simulations using Schrodinger suite 2020-4. Furthermore, the safety profile of compounds was examined through the OSIRIS property explorer program and the results were compared with the standard drugs, 5-fluorouracil and cyclophosphamide. Results: Based on the binding affinity scores, the compounds were found selective to target protein 1q4k through hydrogen bonding and hydrophobic interactions. The compounds A11, A12, and A13 were found to have higher G scores and binding free energy values. The ADME screening results were also found to be within the acceptable range. Moreover, the in-silico toxicity prediction assessments suggest that all designed compounds have a low risk of toxicity, and have higher efficiency for the target receptor. Conclusion: The study showed that the substitution of electron-donating groups at the various position of the aromatic ring, which is bonded at the second position of the substituted 1,3,4- oxadiazole nucleus resulted in compounds with good binding energy and G score compared to the standard drugs, and hence, they can be further developed as potent PLK1 enzyme inhibitors.