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Lead Wistar Inventors
Paul M. Lieberman, Ph.D. Troy E. Messick, Ph.D.

Unmet Need

Tumor viruses drive many human cancers. Epstein-Barr Virus (EBV) is associated with several malignancies, including nasopharyngeal cancer (NPC), Burkitt’s lymphoma, non-Hodgkin’s lymphoma, gastric carcinoma, and NK/T cell lymphoma and is estimated to be responsible for one-to-two percent of all human cancer worldwide. Existing antivirals are ineffective against treating EBV infection and there are no orally bioavailable small molecule inhibitors available on the market to treat EBV-associated cancers.


EBNA1 Target:

Epstein-Barr Nuclear Antigen 1 (EBNA1) is an ideal target for elimination of latent infection and treatment of EBV-associated disease. EBNA1 is expressed in all EBV positive tumors. EBNA1 is required for immortalization of primary B-lymphocytes and for the stable maintenance of the EBV genome in latently infected cells. The structure of EBNA1 represents a unique fold that has no homology to other proteins in the human proteome. By targeting a virally expressed protein with no known human orthologs, these compounds will have few side effects and mitigate the potential risk of inherent toxicity. The three-dimensional structure of EBNA1 bound to the inhibitors has been solved by x-ray crystallography and has driven our chemical strategy. Collectively, these studies demonstrate that EBNA1 is an ideal and validated target for inhibition of latent EBV and treatment of EBV-associated malignancies.

Nasopharyngeal Carcinoma (NPC):

Nasopharyngeal Carcinoma is our primary target patient population for this first-in-class drug discovery program for several reasons. First, nearly 100 percent of non-keratinizing NPC is EBV positive. Second, NPC is a serious health problem worldwide. According to data from the International Agency for Research on Cancer (IARC), 84,500 cases are diagnosed and 51,600 deaths occur each year worldwide. Third, patients usually present with advanced locoregional disease, 40 to 60 percent of whom fail the current standard of care. For patients with distant metastases, the chance of cure remains dismal. Fourth, the current chemotherapy regimen of cytotoxic drugs has a severe toxicity profile and has limited efficacy. Our EBV specific therapy aims for superiority in terms of efficacy and safety profile as compared to the current chemotherapeutic standard of care. Finally, biomarkers for NPC are available that have clinical relevance for the predicted mechanism of action.

Stage of Development

Supported by the Wellcome Trust and led by an internationally recognized leader in the EBV field, Dr. Lieberman and team have developed potent inhibitors of latent EBV infection. These inhibitors have nanomolar potency in biochemical and cell based assays and are efficacious in animal models of EBV-driven cancers. The unique therapeutic strategy is to inhibit latent EBV that drives the proliferation of EBV-positive cancers. Our first-in-class inhibitor of latent EBV provides superior efficacy and a better safety profile than the current standard of care.

Lead Series Profile:

Our compound meets or exceeds industry standard criteria for development:


– Nanomolar potency in biochemical assays
– Selective activity in cell based assays
– Biophysical validation of target engagement
– High aqueous solubility


– No CYP450 inhibition activity
– High metabolic stability in human and mice liver microsomes
– High bioavailability and low clearance in PK studies

Safety and toxicology

– No hemolysis activity
– No hERG activity
– High selectivity in broad-based screens
– Negative in Ames test for mutagenicity
– Low in vivo toxicity: high maximum tolerated dose

In vivo studies:

We have performed xenograft studies using an EBV-positive NPC cell line. EBNA1 inhibitors provide a significant tumor protective effect with a tumor growth inhibition level > 93%. We performed histochemistry analysis on the tumor derived from the xenograft studies. EBER-ISH, a robust, sensitive method for detecting EBV in latently infected cells, indicates that the vehicle control tumors contain EBV RNA, whereas the inhibitor treated tumor is virtually EBV-free. These results are indicative that the lead series is engaging the target in vivo and further validates our therapeutic approach.

Intellectual Property

A robust patent portfolio has been assembled to protect the lead series and related chemical space including composition of matter and medical use claims. US9309212; 15/054455; 15/036,211; PCTUS2014/065765 [U.S., EPO, Japan, Singapore, Brazil, Mexico, New Zealand, India, China, Australia, South Korea, Thailand, Canada]; PCT/US2012/038938; PCT/US2016/032574.

Collaboration Opportunity

The Wellcome Trust and The Wistar Institute are seeking a co-development collaborator to bring this program into the clinic.