ABSTRACT
Objective: To study structure-specific solubilization effect of Sulfobutyl ether-ß-cyclodextrin (SBE-ß-CD) on Remdesivir (RDV) and to understand the experimental clathration with the aid of quantum mechanics (QM), molecular docking and molecular dynamics (MD) calculations. Methods: The experiment was carried out by phase solubility method at various pH and temperatures, while the concentration of Remdesivir in the solution was determined by HPLC. The complexation mechanism and the pH dependence of drug loading were investigated following a novel procedure combining QM, MD and molecular docking, based on accurate pKa predictions. Results: The phase solubility and solubilization effect of RDV in SBE-ß-CD were explored kinetically and thermodynamically for each assessed condition. An optimal drug / SBE-ß-CD feeding molar ratio was determined stoichiometrically for RDV solubility in pH1.7 solution. The supersaturated solubility was examined over time after pH of the solution was adjusted from 1.7 to 3.5. A possible hypothesis was raised to elucidate the experimentally observed stabilization of supersaturation based on the proposed RDV Cation A /SBE-ß-CD pocket conformations. Conclusion: The computational explorations conformed to the experimentally determined phase solubilization and well elucidated the mechanism of macroscopic clathration between RDV and SBE-ß-CD from the perspective of microscopic molecular calculations.
