Identification of pyrazole scaffold inhibitors targeting cyclin-dependent kinase 8 for potential use in pulmonary fibrosis.

Idiopathic Pulmonary Fibrosis (IPF) is a disease that includes inflammation and scarring of the lung tissues. Cyclin-dependent kinase 8 (CDK8) is a target of interest due to its role in inflammatory pathways. CDK8 can also modulate the TGF-β/Smad signaling associated with IPF. Herein, a structure-based virtual screening (SBVS) campaign led to the identification of three CDK8 inhibitors. Testing of candidate inhibitors in protein and cellular assays confirmed CDK8 inhibition, with the most potent inhibitor producing an IC value of 398.8 nM. Computational analysis identified pharmacological interactions that lead to CDK8 inhibition. No significant cytotoxicity was observed when the inhibitor was treated in vitro. Further results showed that the inhibitor can disrupt proteins associated with the epithelial-mesenchymal transition (EMT) and reduce cell migration. Additionally, the inhibitor can disrupt the TGF- β1/Smad signaling axis in the nucleus, potentially impacting the transcription of IPF related protein expression, when treated in cells at 5 µM. Comparisons to structures of known CDK8 inhibitors showed the identified inhibitor to be structurally novel. When tested against a panel of kinases at 1 µM, the most potent inhibitor demonstrated a favorable CDK8 selectivity profile. The identification of the CDK8 inhibitors in this study can be used in future drug design studies and as CDK8 probes to explore alternative therapeutics for IPF.