An insight into the interaction between Indisulam and human serum albumin: Spectroscopic method, computer simulation and in vitro cytotoxicity assay.

Indisulam (IDM) is a sulfanilamide anticancer agent and has been identified as a molecular glue recently. It shows potential for novel therapies development and brings more hope for curing human diseases. The affinity between molecular glues and plasma protein makes it significant to understand the characteristics of such substances. Therefore, the interaction between IDM and human serum albumin (HSA) was explored through solvent experiments, computer simulation experiments, enzyme kinetics experiments, and cell viability assay. The results revealed that IDM and HSA spontaneously formed stable binary complex with the binding constant of the order 105 M-1. IDM inserted in the site I of HSA, resulting the change in HSA secondary structure. And π electrons in IDM's benzene rings, as well as van der Waals forces and the H-bond, all helped to stabilize the HSA-IDM complex. The results of molecular dynamic simulation (MD) corresponded with the results from solvent experiment well. For instance, there were approximately 1-5 H-bonds between IDM and HSA. Lys199 and Arg218 were crucial energy contributors in the binding process. The esterase-like activity experiment confirmed that IDM inhibited the catalytic activity of HSA. In addition, cell experiment revealed that serum albumin can significantly reduce the cytotoxicity of IDM towards human embryonic kidney 293T (HEK293T) cells.