Abstract 695: The generation of a mono-selective CDK7 inhibitor.

Abstract

Abstract Cyclin-depending kinase (CDK) family members that trigger passage through the cell cycle have been considered as attractive cancer targets for at least two decdes Yet, the first generation of pan-specific CDK inhibitors failed to show clinical efficacy due to their small therapeutic window. CDK family members that control processes such as transcription have caught less attention, although experimental evidence for an involvement in different pathological processes is emerging. CDK7 (or CAK) has essential roles in both the cell-division cycle and transcription, and serves as a direct link between the regulation of basal transcription and the cell cycle. In addition to its role as a transcription activator, CDK7 has been reported to act on specific transcription events by phosphorylating a series of specific transcription factors, such as the estrogen receptor and p53. These findings indicate that CDK7 is a potential target for cancer therapy, and perhaps inflammation. The detailed molecular characterization of the biological role of CDK7, as well as its therapeutic validation, is dependent on the development of highly specific and potent CDK7 inhibitors. We have developed a series of CDK7 inhibitors with picomolar potency on CDK7, more than 1000-fold selectivity over any other CDK, and single digit nM inhibition of sensitive cancer cell lines. Interestingly, a broad screen of >200 different tumor cell lines lead to the identification of responder and non-responder cell lines. Non-responder tumor lines, similar to primary cells are at least by a factor of 1000 less sensitive to the inhibition with the mono-selective CDK7 inhibitor. Our findings further indicate that CDK7 is neither essential for general transcription, nor for the progression through the cell cycle. It rather coordinates cell line specific biological processes. The effects of selective CDK7 inhibitors on tumor cell lines are clearly distinct from existing, nonselective pan-CDK inhibitors. The responder status for a subset of cancer cell lines can be predicted with a distinct biomarker. Chemical optimization of the selective inhibitor lead to a compound which shows dose-dependent pharmacological efficacy in mouse xenograft models after oral administration, with no signs of toxicity at the efficacious doses. Citation Format: Jan E. Eickhoff, Gunther Zischinsky, Axel Choidas, Peter Habenberger, Alexander Wolf, Carsten Degenhardt, Matthias Baumann, Anke Unger, Ahmad Ghallab, Doreen Werchau, Jan Hengstler, Peter Nussbaumer, Bert M. Klebl. The generation of a mono-selective CDK7 inhibitor. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 695. doi:10.1158/1538-7445.AM2013-695