Design,synthesis And Anti-pancreatic Cancer Activity Of Novel KRAS-PDEδ Inhibitors

KRAS signaling pathway is closely related to the occurrence of cancer.The mutantion of KRAS protein is common in different kinds of cancers,particularly in appproximately90%pancreatic cancers.Targeting KRAS signaling is becoming an important strategy in antitumor drug discovery.However,it is challenging to find new chemical entities targeting KRAS because of the lack of suitable binding cavities on the KRAS protein surface.Recently,it has been confirmed that PDEδprotein is essential to the transportation and correct localiztion of KRAS in the cell.PDEδregulates the dynamic distribution of KRAS in the cell and promote the accumulation of KRAS protein on the cell membrane.Carcinogenic signals are ultimately released on account of high concentration of KRAS on the plasma membrane.Therefore,KRAS-PDEδprotein-protein interaction has been recognized as a potential target for anti-KRAS signaling.This dissertation focused on the drug discovery of novel small molecule KRAS-PDEδprotein-protein interaction inhibitors.Main results include two parts:1.Fragmented-based drug design of novel KRAS-PDEδinhibitors.Inspired by the the crystal structures of PDEδin complex with fragment-like inhibitors（PDB entry:4JV6 and 5X73）,computational FBDD was applied in rational design of novel PDEδinhibitors via linkage of the two fragment inhibitors.Novel KRAS-PDEδinhibitors with high binding affinity were designed and synthesized.The binding affinity of compound C2（K_D=4±1.1 nM）was relatively higher than that of deltazinone（K_D=8±4 nM）,while compounds C8(IC₅₀=58.6±6.3μM)and D9(IC₅₀=52±2.5μM)were comparable to deltazinone(IC₅₀=48±6μM)in terms of in vitro anti-tumor activities.2.Structure-based optimization of novel KRAS-PDEδinhibitors.The main drawbacks of the existing inhibitors are low cellular potency and poor drugability.Further structural optimization studies were performed by structure-based rational design of 18 new inhibitors.All of these compounds showed good binding affinity toward PDEd.Importantly,the antitumor activity of most compounds was significantly better than celtazinone.In particular,compounds E1(K_D=58±5 nM,IC₅₀=28±6.3μM)and G3(K_D=38±17 nM,IC₅₀=8.8±2.4μM)had a good combination on the binding affinity and antitumor activity.Compound G3 remarkablely down-regulated phosphorylation of Erk and Akt.Immunofluorescence staining experiments showed that compound G3 could dramatically interfere with the intracellular KRAS-PDEδinteraction.This study provided a promising molecular probe or lead compound for investigation in the biological functions and druggability of KRAS-PDEδinteraction.