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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.

The anti-TBEV effect of 2=-CMA in cell culture diminished gradually after day 3 posttreatment. 7-Deaza-2=-CMA showed no detectable cellular toxicity (CC 50 > 50 M), and the antiviral effect in culture was stable for >6 days posttreatment. Computational molecular analyses revealed that compared to the other two compounds, 7-deaza-2=-CMA formed a large cluster near the active site of the TBEV polymerase. High antiviral activity and low cytotoxicity suggest that 7-deaza-2=-CMA is a promising candidate for further investigation as a potential therapeutic agent in treating TBEV infection.

Phosphatidylinositol 4-kinase IIIβ (PI4KB) is indispensable for the replication of various positive-sense single stranded RNA viruses, which hijack this cellular enzyme to remodel intracellular membranes of infected cells to set up the functional replication machinery. Therefore, the inhibition of this PI4K isoform leads to the arrest of viral replication. Here, we report on the synthesis of novel PI4KB inhibitors, which were rationally designed based on two distinct structural types of inhibitors that bind in the ATP binding side of PI4KB. These "hybrids" not only excel in outstanding inhibitory activity but also show high selectivity to PI4KB compared to other kinases. Thus, these compounds exert selective nanomolar or even subnanomolar activity against PI4KB as well as profound antiviral effect against hepatitis C virus, human rhinovirus, and coxsackievirus B3. Our crystallographic analysis unveiled the exact position of the side chains and explains their extensive contribution to the inhibitory activity.

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