Cyclin-G associated kinase (GAK) emerged as a promising drug target for the treatment of viral infections. However, no potent and selective GAK inhibitors have been reported in the literature to date. This paper describes the discovery of isothiazolo[5,4-b]pyridines as selective GAK inhibitors, with the most potent congeners displaying low nanomolar binding affinity for GAK. Co-crystallization experiments revealed that these compounds behaved as classic type I ATP-competitive kinase inhibitors. In addition, we have demonstrated that these compounds exhibit a potent activity against hepatitis C virus (HCV) by inhibiting two temporally distinct steps in the HCV lifecycle (i.e. viral entry and assembly). Hence, these GAK inhibitors represent chemical probes to study GAK function in different disease areas where GAK has been implicated (including viral infection, cancer and Parkinson's disease).

COVID-19, caused by the SARS-CoV-2 virus, is responsible for a global pandemic that has paralyzed the normal life in many countries around the globe. Therefore, the preparation of both effective vaccines and potential therapeutics has become a major research priority in the biotechnology sector. Both viral proteins and selected host factors are important targets for the treatment of this disease. Suitable targets for antiviral therapy include i.a. viral methyltransferases, which allow the viral mRNA to be efficiently translated and protect the viral RNA from the innate immune system. In this study, we have focused on the structure-based design of the inhibitors of one of the two SARS-CoV-2 methyltransferases, nsp14. This methyltransferase catalyzes the transfer of the methyl group from S-adenosyl-L-methionine (SAM) to cap the guanosine triphosphate moiety of the newly synthesized viral RNA, yielding the methylated capped RNA and S-adenosyl-L-homocysteine (SAH). The crystal structure of SARS-CoV-2 nsp14 is unknown; we have taken advantage of its high homology to SARS-CoV nsp14 and prepared its homology model, which has allowed us to identify novel SAH derivatives modified at the adenine nucleobase as inhibitors of this important viral target.We have synthesized and tested the designed compounds in vitro and shown that these derivatives exert unprecedented inhibitory activity against this crucial enzyme. The docking studies nicely explain the contribution of an aromatic part attached by a linker to the position 7 of the 7-deaza analogues of SAH. Our results will serve as an important source of information for the subsequent development of new antivirals to combat COVID-19. File list (2) download file view on ChemRxiv nsp14_chemRxiv_Tomas.pdf (1.29 MiB) download file view on ChemRxiv chemRxiv_Supporting_final.pdf (4.16 MiB) The structure-based design of SARS-CoV-2 nsp14 methyltransferase ligands yields nanomolar

Phosphatidylinositol 4-kinase IIIβ is a cellular lipid kinase pivotal to pathogenesis of various RNA viruses. These viruses hijack the enzyme in order to modify the structure of intracellular membranes and use them for the construction of functional replication machinery. Selective inhibitors of this enzyme are potential broad-spectrum antiviral agents, as inhibition of this enzyme results in the arrest of replication of PI4K IIIβ-dependent viruses. Herein, we report a detailed study of novel selective inhibitors of PI4K IIIβ, which exert antiviral activity against a panel of single-stranded positive-sense RNA viruses. Our crystallographic data show that the inhibitors occupy the binding site for the adenine ring of the ATP molecule and therefore prevent the phosphorylation reaction.