Summary

Aurora Kinase A (AurkA) is a protein kinase described to be involved in myriad cellular pathways with its major role being the regulation of proper mitosis progression. Elevated expression and activation of AurkA have been identified as a characteristic of multiple cancer types, positioning AurkA as an attractive target for cancer treatment. Despite the encouraging results of clinical trials for AurkA inhibitors, it has become clear that catalytic inhibition of AurkA leads to dose-limiting toxicities.

Previous work from our research group identified AurkA as a promising therapeutic target for the treatment of TP53-altered liver carcinomas. In order to overcome toxicity limitations and thus enhance the therapeutic index, first-of-their-kind kinase-spearing AurkA-ligands specifically targeting the AurkA interactome were developed. 

As part of a multi-year medicinal chemistry development program, we initially screened a TüCAD compound library to identify candidates selective for Trp53^-/- murine liver cancer cells. Using  molecular docking simulations and iterative structure-activity-relationship (SAR)-driven optimization cycles, we successfully developed first-in-class kinase-sparing AurkA ligands. Within these optimization cycles, we were able to synthesize three generations of active ligands building up a project library of about 600 compounds. In addition to enhancing cellular activity and selectivity, we applied structure-based approaches to improve key pharmacokinetic properties, including metabolic stability, solubility, and bioavailability, both in vitro and in vivo.

The novel AurkA ligands selectively kill TP53-deficient human liver cancer cells, as well as AurkA-dependent TP53; RB1-deficient human small cell lung cancer cells (SCLC). Mechanistically, these novel AurkA ligands induce cell death by mitotic catastrophe, as seen by immunofluorescence staining that revealed rapid spindle defects and deregulated mitosis. In particular, immunoprecipitation and cellular thermal shift assays indicated that the ligands lead to a hyperstabilization of the complex of AurkA with its major allosteric co-activator TPX2. 

The preclinical safety assessment of our novel ligands supported the initial hypothesis. Continuous administration of AurkA ligands to mice did not result in toxicities, as these ligands do not interfere with the kinase function of AurkA, which is crucial for non-transformed cells. Moreover, further investigations with a novel 3^rd-Generation AurkA ligand demonstrated a favorable safety profile in standard in vitro assays widely used in the pharmaceutical industry to evaluate the inhibition or activation of over 500 human target proteins.

Preclinical proof-of-concept therapy studies using a novel 3^rd-Generation AurkA ligand as a single agent demonstrated highly significant prolongation of survival in HDTV-induced hepatocellular carcinoma mouse models. Furthermore, therapeutic evaluations in cell line-derived xenografts (CDX) and orthotopic small cell lung cancer mouse models showed remarkable therapeutic efficacy of these novel 3^rd Generation AurkA ligands as standalone treatments.

References:

• Moschopoulou et al. 2024 Cancer Res. 84 (6_Supplement): 4478. (Link:  https://doi.org/10.1158/1538-7445.AM2024-4478)
• Dauch et al. 2016 Nat. Med. (22), 744–753 (Link: https://www.nature.com/articles/nm.4107)
• Patents:
  • EP24165627
  • WO/2022/096679 A1