Rational Design,Synthesis And Biological Evaluation Of CGAS Inhibitors Based On The Virtual Screening&the Study Of The Computational Approach For The Binding Mode Of S1P₁ Agonists Base On The Active-like Receptor Model

The cyclic GMP-AMP synthase(cGAS)is a member of nucleic acid transferase,which can synthesize the second messager,2’,3’-cGAMP,to activate the stimulator of interferon genes(STING)on the endoplasmic reticula(ER)for the regulation of the innate immunity.Recently,cGAS has been declared as a potential target for the autoimmune disease because the inhibition of the cGAS leads to the immunosuppress.Since there are few known scaffolds of cGAS inhibitor,we will integrate the structure-based and the ligand-based drug design strategies to design,synthesize and evaluate the novel cGAS inhibitors with high activity.First,the cascading processes of virtual screening will be implemented based on the methods such as complex-based pharmacophore model,molecular docking and molecular dynamic.The potential hits of cGAS inhibitor will be obtained from the commercial database of small molecule.After the evaluation of the biological activity,compound WJ-0016 with substituted acetamide scaffold,which remained weak activity in the 10 μM level,was found for the further structure optimization.Based on this hit compound,seventeen compounds were designed,synthesized as the series Ⅰ.Meanwhile,eighteen compounds were designed and synthesized based on the ligand-based strategies as the series Ⅱ.Then,the biological evaluation will be applied to the total thirty-five compounds.With the structure-activity relationship of the compounds series Ⅰ,we draw a conclusion that the substituted acetamide scaffold with a flexible hydrophilic group instead the aromatic chloride atom,a mesyl group and anα-naphthylamine structure will be more potential as cGAS inhibitor.Finally,compound I-a-9c and I-a-8 remaining respectively 83.9%and 75.4%inhibition ratio in the 10μM level,which performed better than the positive compound and the WJ-0016,were obtained for the further development.Sphingosine-1-phosphate receptor-1(SIPiR)is a member of the G protein-coupled recq)tor(GPCR)family.It plays an important role in the regulation of the immune system.Therefore,the SIP1R becomes a hot target for the autoimmune disease,and there are two drugs on marked for S1P1R,Fingolimod(S-FTY720)and Siponimod(BAF312).With the development of the study,more and more SIP1R agonists were reported and several of them have been in the clinical trails.Unfortunately,the study of the structure biology for SIP1R is hysteretic because there is only an inactive state of SIP1R reported.Although some key residues for the binding affinity could be revealed by the site-mutagenesis study,but the integrated binding model of the S1P1R is still unclear.To solve this question,our team integrated the existing data and the experience of the ligand-based SIP1R agonists design,and tried to induce the inactive state of S1P1R to obtain the active-like state of SIP1R via Gaussian accelerated molecular dynamic(GaMD).Then,two representative SIP1R agonists were docked into the active-like pocket of the SIP1R to verify the rationality of the computational result.In the further study,we collected over one thousand SIP1R agonists with the biological activity value.Then these compounds were docked into the active-like and inactive state SIP1R respectively.The computational result showed that the active-like state of SIP1R performed better in the prediction of the activity for SIP1R agonists than the inactive one.After that,the molecular dynamic and the MM-GBSA method were used to analyze the binding model of three S1P1R agonists in the clinical trials systematically.From the result of the energy decomposition,we found four groups of key residues were vital for the binding model,they were group P1:Arg120,Glul21;group P2:Met124,Phe125,Leu297;group P3:Leu195,Cys206,Leu272,Leu276;group P4:Phe210,Trp269.Furthermore,the salt bridge in P1 and theπ-π stacking in P2 were considered as the most importance interactions,and the hydrophobic interaction in P3 and P4 was never reported before in a systemic way.Not only that,we also synthesized some oxadiazole derivatives based on the known S1P1R agonists designed and synthesized in house.Finally,the biological activity was evaluated and all the five oxadiazole derivatives were docked into the active-like pocket of the S1P1R to verify the rationality of the active-like state of S1P1R and the four groups of key residues.