Comparative insights into the effects of thalidomide and lenalidomide on the structure and function of human serum albumin.

Thalidomide (TLD) and lenalidomide (LND) are immunomodulatory drugs widely employed in multiple myeloma (MM) therapy. Structural differences between TLD and LND lead to differential interactions with human serum albumin (HSA). These interactions first manifest as functional alteration, with both drugs significantly enhancing the esterase-like activity of HSA, and TLD exhibiting a stronger activating effect than LND. Furthermore, TLD and LND alter the secondary structure of protein, with TLD inducing a greater reduction in α-helix content than LND. Further investigation into the interaction mechanisms revealed that both TLD and LND spontaneously bind to site I of HSA, primarily driven by H-bonds and van der Waals forces. Comparative binding affinity (Ka) showed that TLD has a higher binding strength to HSA than LND, as confirmed by molecular docking. Energy decomposition and computational alanine scanning (CAS) analyses indicated that structural differences between TLD and LND influence the types of interacting residues and their energy contributions. Specifically, Lys199, Phe211, Trp214, Ala215, and Arg222 play critical roles in TLD binding, whereas LND binding relies predominantly on both Lys199 and Trp214. Notably, the interaction between Lys199 and these two drugs is a key factor affecting changes in the esterase-like activity of HSA. Our integrated strategy provides novel insights into the distinct interactions between TLD/LND and HSA, which may provide a molecular basis for understanding their differential clinical efficacy and safety profiles.