Epstein Barr virus-positive B-cell lymphoma is highly vulnerable to MDM2 inhibitors in vivo.

Epstein-Barr virus (EBV)-positive B-cell lymphomas are common in immunocompromised patients and remain an unmet medical need. Here we report that MDM2 inhibitors (MDM2i) navtemadlin and idasanutlin have potent in vivo activity in EBV+ B-cell lymphoma established in immunocompromised mice. Tumor regression was observed in all 5 EBV+ xenograft-associated B-cell lymphomas treated with navtemadlin or idasanutlin. Molecular characterization showed that treatment with MDM2i resulted in activation of p53 pathways and downregulation of cell cycle effectors in human lymphoma cell lines that either were EBV+ or had undetectable expression of BCL6, a transcriptional inhibitor of the TP53 gene. Moreover, treatment with navtemadlin resulted in tumor regression and prevented systemic dissemination of EBV+ lymphoma derived from 2 juvenile patients with posttransplant lymphoproliferative diseases, including one whose tumor was resistant to virus-specific T-cell therapy. These results provide proof-of-concept for targeted therapy of EBV+ lymphoma with MDM2i and the feasibility of using EBV infection or loss of BCL6 expression to identify responders to MDM2i.