Allosteric drugs targeting Aurora kinases for the treatment of cancer

• Applicant: Dr. Ricardo M. Biondi
• Subject Area: Pharmacy ; Pharmacology
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264918179

There is consensus that the future treatment of cancer will involve the combination of targeted drugs, selected based on the particular characteristics of the tumors, in a personalized medicine approach. Thus, future personalized therapies require a larger set of selective targeted drugs that could be used in combination therapies. Protein kinases are major drug targets and numerous drugs directed to the ATP-binding site have been developed over the last decade. However, most of those drugs are very unselective. As an alternative, there is increasing interest in the development of allosteric, non-ATP-binding site regulators of protein kinases. Over the last 12 years, we discovered and characterized an allosteric regulatory site (PIF-pocket) in the large family of AGC protein kinases. We were also pioneers in developing the technology to pharmacologically activate or inhibit AGC kinases by targeting the allosteric PIF-pocket with low-molecular-weight compounds. Aurora kinases (AurA, AurB, and AurC) are closely related to AGC protein kinases and are activated by the binding of the auxiliary proteins TPX2 and INCENP, which bind to a PIF-pocket-site of AurA and AurB, respectively. Aurora kinases are important regulators of cell division, are overexpressed in a variety of cancer types, and are promising drug targets for the treatment of cancers. Notably, AurA stabilizes N-Myc, acting together as oncogenic partners in 20-30% of childhood cancer neuroblastoma. It is considered that AurA kinase inhibition by allosteric compounds will destabilize AurA/N-Myc complexes, lead to N-Myc degradation, and thus be more effective for the treatment of cancers. As preliminary work to this application, we used medium-throughput screening and identified low-molecular-weight modulators of human AurA, which displace TPX2 from the allosteric pocket, indicating an allosteric mechanism of action. We also obtained detailed information on one hit compound, PSx137, which inhibits AurA activity in vitro, promotes the arrest of the cell cycle of human cancer cells in the G2/S stage, and is toxic to these cells in culture. The current application aims to analyze the structural mechanism of action of PSx137 and other novel identified compounds and to obtain crystal structures of Aurora proteins in complex with the allosteric compounds. The structural information will confirm the binding site of the allosteric compounds and allow us to understand the mechanisms underlying allosteric communication and crosstalk between the PIF-pocket-site and the active site, details which remain largely unknown. In addition, the research on the current application will provide information for the rational improvement of the potency and selectivity of such allosteric regulators of Aurora kinases for the development of anti-cancer drugs. The project is in line with major undertakings of the Frankfurt University Hospital in translational research.

• DFG Programme: Research Grants