Development of a small molecule drug for EBV-associated gastric cancers.

63 Background: Worldwide, EBV is associated with ~10% of gastric cancer. Currently, no pharmaceutical-based therapies exist that selectively target EBV associated gastric cancers. EBV, in its latent oncogenic form, is dependent on the continuous expression of Epstein-Barr Nuclear Antigen 1 (EBNA1), a multifunctional dimeric protein critical for viral replication, genome maintenance and viral gene expression. Methods: The aim of this program is to advance the development of a New Chemical Entity (NCE) for latent infection of Epstein-Barr Virus (EBV) to treat EBV-associated gastric cancer. We have used structure-based drug design and medicinal chemistry methods to identify and develop a small molecule clinical candidate that selectively inhibits the DNA-binding activity of EBNA1. Results: The clinical candidate inhibits EBNA1 function with nanomolar potency in biochemical assays and low micromolecular activity in several cell-based assays. We demonstrate that our clinical candidate provides protection in 4 different xenograft models of EBV-driven tumor growth, including patient-derived xenografts. Furthermore, RNA analysis experiments confirm in vivo target engagement by the elimination of EBV in treated tumor tissue. The clinical candidate is selective, showing no activity in an EBV-negative xenograft experiments. The clinical candidate has met industry-accepted criteria for drug suitability, safety and toxicology including physicochemical properties, metabolic stability, selectivity in broad-based screens and bioavailability, and lack in vivoliabilities, including genotoxicity and 14-day toxicity studies. Conclusions: IND-enabling studies including safety pharmacology and toxicology and GMP manufacturing have begun with a projected First-In-Human clinical trial in Q4 2017. These data establish proof-of-concept for targeting EBNA1—a protein previously thought to be undruggable.