Design, Synthesis And Bioactivity Study Of Small Molecule Inhibitors Targeting Mcl-1 Protein

The anti apoptotic protein Bcl-2 and Mcl-1 in Bcl-2 family proteins are overexpressed in many tumor cells and antagonize the apoptosis of tumor cells.They are important targets for targeting anticancer drugs.ABT-199 targeting Bcl-2 protein is approved by FDA,but Mcl-1protein cannot be targeted resulting in resistance to many tumor cells.Therefore,targeting Mcl-1 protein inhibitors is a major challenge in this field.In this paper,we used fragment based drug design method to grow S1-6 that is Mcl-1 and Bcl-2 protein double target inhibitor.By retaining the key pharmacophore of S1-6（bromothiol and carbonyl）,meanwhile introducing the hydrophobic group and the hydrogen bond receptor group to occupy P2 hydrophobic pocket that is an active site of the Mcl-1 protein,compounds A3-A13 that targeting Mcl-1 were designed and synthesized.Compounds A10 and A13 were obtained as selective Mcl-1 protein inhibitors.ELISA detection of IC₅₀ is 0.50 and 0.80μM,and the affinity is 5-7 times higher than Bcl-2 protein.¹H-¹⁵N NMR results showed that these compounds occupied P2 and P4 pockets of Mcl-1 protein,and interacted with Arg263.The results of structure-activity relationship analysis confirm that the introduction of hydrophobic group and hydrogen bond receptor group is beneficial to the combination of molecular and Mcl-1 protein,while the introduction of hydrophobic group occupying the P2 pocket realizes the molecular selectivity to Mcl-1.It proves that the P2 pocket is a binding site that contributes to Mcl-1 selectivity.In addition,Bcl-2/Mcl-1 protein double target inhibitor compound A11 was obtained,which can combine Mcl-1 and Bcl-2 proteins with affinity of sub-μM.Cell activity experiments showed that compounds A11 and A13 could induce apoptosis of K562,Hela tumor cells with high expression of Mcl-1 and IC₅₀ are 3.36±1.01μM and 7.02±0.40μM respectively.This study not only obtained the Mcl-1 protein selective inhibitor and the Mcl-1/Bcl-2protein double target inhibitor,but also provided the structural basis and principle for the design of the selective inhibitor of Mcl-1 protein.