Identification\nof a Potent CDK8 Inhibitor Using Structure-Based\nVirtual Screening

Pulmonary fibrosis\nis excessive scarring of the lung\ntissues. Transforming\ngrowth factor-beta (TGF-β) has been implicated in pulmonary\nfibrosis due to its ability to induce the epithelial-to-mesenchymal\ntransition (EMT) and promote epithelial cell migration. Cyclin-dependent\nkinase 8 (CDK8) can mediate the TGF-β signaling pathways and\ncould function as an alternative therapeutic target for treating pulmonary\nfibrosis. Here, we performed a structure-based virtual screening campaign\nto identify CDK8 inhibitors from a library of 1.6 million compounds.\nThe screening process ended with the identification of a novel CDK8\ninhibitor, P162-0948 (IC<sub>50</sub>: 50.4 nM). An interaction analysis\nhighlighted important CDK8–ligand interactions that support\nits binding and inhibitory activity. Testing against a panel of 60\ndifferent kinases demonstrated P162-0948 selectivity toward CDK8.\nCrucially, the inhibitor was found to be structurally novel when compared\nto known CDK8 inhibitors. Testing in A549 human alveolar epithelial\ncell lines showed that the P162-0948 can reduce cell migration and\nprotein expression of EMT-related proteins. When P162-0948 was treated\nin cells at 5 μM, phosphorylation of Smad in the nucleus was\nreduced, which suggests disruption of the TGF-β/Smad signaling\npathway. The identification of P162-0948 shows that it is not only\npotent, but its structural novelty can inform future design studies\nfor potential therapeutics targeting pulmonary fibrosis.