Preclinical In Vitro And In Vivo Study Of Ud-017, A Novel Highly Selective And Orally Available Cdk7 Inhibitor, In A Variety Of Cancers.

e14086 Background: Cyclin dependent kinase 7 (CDK7) modulates mRNA transcription and some oncogenes are reported to be sensitive to inhibition of transcription in certain cancer cells. CDK7 inhibitors have been considered as an intriguing approach to treat cancers that depend on transcriptional regulation of their oncogenes. We synthesized a novel highly selective CDK7 inhibitor, UD-017, and found that the compound showed antitumor potency in a variety of cancers in vitro and in vivo. We therefore explored underlying mechanisms especially focusing on an oncogenic driver, c-Myc. Methods: We examined CDK7 selectivity of UD-017 against the other CDKs and kinases. We evaluated an antiproliferative activity of UD-017 in over 200 multiple types of cancer cell lines including patients-derived cancer cells. We then investigated the correlation between c-Myc expression levels and an antiproliferative activity of UD-017 in cancer cells. Antitumor efficacy of UD-017 was assessed in multiple types of cancer xenograft models and patients-derived xenograft model. We determined whether an intratumoral c-Myc expression levels correlated with in vivo antitumor efficacy of UD-017 in xenograft models. Results: UD-017 inhibited CDK7 enzyme (IC 50 = 16 nM) highly selectively among the CDKs (over 300-fold) and almost mono-specifically in a panel of 313 kinases assay. In a cellular antiproliferative panel assay, UD-017 broadly inhibited the proliferation of a variety of cancer cells and c-Myc expression levels showed the good correlation with antiproliferative activity. UD-017 showed favorable PK profile and good oral absorbability and showed the potent antitumor activity in multiple types of cancer xenograft models in mice. In correlation with the PK, UD-017 reduced the intratumoral c-Myc mRNA levels time-dependently after dosing of UD-017 in the colorectal cancer xenograft model. Conclusions: We identified a highly selective and orally available CDK7 inhibitor that showed the broad in vitro and in vivo antitumor activity in a variety of cancers, modulating c-Myc as an oncogenic driver. These data support the rationale for further advancing towards clinical development.