Design,Synthesis And Biological Activities Of Novel PARP-1 Inhibitors With Pyrazolotriazinone Skeleton

Poly(ADP-ribose)polymerases(PARPs)are nucleus enzymes exist in eukaryotic cells,which play an important role in the process of DNA repair.Present PARP-1 inhibitors were designed based on the nicotinamide moiety of NAD+ and demonstrated diverse structures.We analyzed the X-ray structures of PARP with substrates and found that the common structural feathers of PARP-1 inhibitors were the key amide group and rigid plane moiety.Furthermore,we find that a large hydrophobic pocket exists in the active site.This feature allows us to introduce various substituents to enhance potency and improve solubility or other physico-chemical properties.Based on the above SAR study,we take Olaparib as template to design Pyrrolotriazinones derivatives as novel PARP-1 inhibitors.Considering the large hydrophobic pocket,we further introduce various side chains to the scaffolds.Molecular dockings were adopted to make sure the rationality of design.Synthesis of pyrrolo[1,2-d][1,2,4]triazin-4(3H)-one derivatives mainly can be divided into three steps.At first,pyrrole,alkyne and tosyl azide occur a three molecule coupling reaction by using a Cu+ catalyst;after that,under a strong alkaline condition,the above compounds are used to react with ethyl carbazate to form pyrrolo[1,2-d][1,2,4]triazin-4(3H)-one nucleus,and the cyano group is hydrolyzed to the carboxy group;finally,a condensation reaction is implemented to afford target compounds.New Pyrrolotriazinone Skeletons as PARP-1 inhibitors were evaluated for their anticancer activity against breast cancer cell line(MDA-MB-3 36)using Olaparib(AZD-2281)as reference drugs.Compounds 1-34,1-35,1-38 and 1-39 showed strong antitumor activity(IC50 values were 39.1nM,69.3 nM,30.5 nM and 31.3 nM),SAR analysis revealed that(?)introduction of 2-chlorine or 2,3-dichloro on the pyrroleon might significantly enhance the activity.(?)1-cyclobutyl and 1-cyclopenty on the end of piperazine might be beneficial for the anticancer activity.(iii)The replacement of 2-H to 2-F on the Benzene couldn't increase the activity.Normal cytotoxicity tests were performed on 1-32,1-34,1-35,1-38 and 1-39 using the Alarm blue method.The results showed that 1-32,1-34 and 1-35 had weak cytotoxicity to normal cells.1-34 and 1-35 showed strong antitumor activity and weak cytotoxicity,and can be used as candidate PARP-1 inhibitors for further study.