Interplay of multiple interaction forces: Binding of tyrosine kinase inhibitor nintedanib with human serum albumin

• Nintedanib leads to increase in alpha helical content in HSA.
• Nintedanib induced compaction in hydrodynamic radii of HSA.
• Nintedanib induced microenvironment change around tryptophan residue.
• Both hydrophobic as well as electrostatic interactions are involved between nintedanib and HSA.

In this study, we have investigated the binding affinity of the newly approved tyrosine kinase inhibitor nintedanib (NIB) with human serum albumin under simulated physiological condition. The obtained results demonstrate that fluorescence intensity of human serum albumin (HSA) gets quenched by NIB and quenching occurs in static manner. Binding parameters calculated from modified Stern–Volmer equation shows that the drug binds to human serum albumin with a binding constant in the order of 103, with the number of binding sites approximately equal to one. Synchronous fluorescence data deciphered the change in the microenvironment of tryptophan (Trp) residue in HSA. Circular dichroism data showed an increase in helical content upon drug binding. Dynamic light scattering measurements deciphered the reduction in hydrodynamic radii of the protein, further differential scanning calorimetry results shows that nintedanib increase the thermostability of HSA. Molecular docking results demonstrated that major binding forces involved in the complex formation are hydrogen bonding and hydrophobic interaction.