Potential Dual Targeting of EGFR and VEGFR2 by Repurposed Drugs for Cholangiocarcinoma: A Molecular Docking Study

Objective: Cholangiocarcinoma is an aggressive hepatobiliary malignancy characterized by high mortality, late-stage diagnosis, and limited systemic treatment options. The epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor 2 (VEGFR2) signaling pathways play central roles in tumor cell proliferation, survival, and tumor angiogenesis. This study investigated the potential inhibitory interactions of three commonly used non-oncologic drugs, doxycycline, propranolol, and metformin, with EGFR and VEGFR2 using molecular docking analysis, and compared their binding profiles with that of sorafenib, a reference multi-target kinase inhibitor.Materials and Methods: The crystal structures of EGFR (PDB ID: 1M17) and VEGFR2 (PDB ID: 4ASD) kinase domains were retrieved from the Protein Data Bank and prepared using OpenBabel. Three-dimensional ligand structures were generated from SMILES representations using RDKit, energy-minimized with the MMFF94 force field, and converted to PDBQT format using Meeko. Docking simulations were performed with AutoDock Vina (version 1.2). The docking protocol was validated by multi-pose redocking of the co-crystallized ligands (erlotinib and sorafenib), with the lowest root-mean-square deviation (RMSD) value reported. Ligand-protein interactions were evaluated using an in-house geometric classification algorithm and independently verified using the Receptor-Ligand Interactions module of BIOVIA Discovery Studio Visualizer. Drug-likeness and physicochemical properties were assessed using RDKit according to Lipinski's rule of five.Results: Docking protocol validation yielded RMSD values of 1.32 Å for EGFR and 0.30 Å for VEGFR2, confirming the reliability of the docking workflow. Among the repurposing candidates, doxycycline exhibited the strongest binding affinity toward both EGFR (-8.82 kcal/mol) and VEGFR2 (-8.17 kcal/mol), with binding energies approaching those of the reference compound sorafenib (EGFR: -9.01 kcal/mol; VEGFR2: -10.54 kcal/mol). Propranolol showed moderate binding affinity, whereas metformin displayed the weakest interactions with both targets. Doxycycline formed conventional hydrogen bonds with the catalytic Asp831 (DFG motif) and hinge-region Thr766 residues of EGFR, and with Asp1046 (DFG motif) and Asp814 residues of VEGFR2. All investigated compounds satisfied Lipinski's rule of five.Conclusion: These findings highlight doxycycline as a noteworthy in silico dual-target candidate against EGFR and VEGFR2 in cholangiocarcinoma, warranting further experimental evaluation. The validated docking workflow and consistent interaction patterns support this observation; however, these findings remain hypothesis-generating and require confirmation through experimental studies before any biological or therapeutic conclusions can be drawn.