ASCO: Viracta's HDAC-inhibitor combination garners high response in EBV-linked lymphoma

The oncology community has long been aware of the association between Epstein-Barr virus (EBV) and certain malignancies, including some forms of lymphoma, but targeting these cancers has proven challenging. Early data from a phase 1b/2 study presented at the American Society of Clinical Oncology (ASCO) annual meeting suggests that combining HDAC inhibition with an antiviral therapy may be effective against EBV-associated lymphoma.

Patients in the trial are receiving a combination of Viracta Therapeutics’ HDAC inhibitor nanatinostat (formerly VRx-3996) and valganciclovir, a drug used to treat cytomegalovirus in patients with HIV/AIDS or in people who have recently received organ transplants.

Researchers at Sidney Kimmel Cancer Center-Jefferson Health, which is leading the study, reported that the combination produced an objective response rate of 58% and a complete response rate of 33%. Based on the results, the researchers are considering moving forward with a dosing schedule that would consist of daily doses of valganciclovir, along with nanatinostat given for four days, followed by three days off, according to a statement.

“The main purpose of this study was to develop a new treatment strategy for EBV-associated lymphomas that takes advantage of the vulnerabilities imposed on the cancer by the presence of the virus,” said Pierluigi Porcu, M.D., director of the division of hematologic malignancies and hematopoietic stem cell transplantation at Sidney Kimmel, in the statement.

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Viracta was launched into the spotlight two years ago, when it raised $18.4 million in a series B funding round led by famed investor Patrick Soon-Shiong’s NantKwest. Viracta dubs its approach to fighting cancer as “Kick and Kill,” meaning the therapies are designed to activate genes that have been suppressed by a virus or the cancer itself, and then activate an immune response against the disease.

EBV is a particularly challenging target because an estimated 95% of the adult population is infected with the virus but many aren’t aware of it because it rarely produces symptoms. After infection, the virus can lurk in lymphatic cells and later turn cancerous. EBV has been linked to nasopharyngeal carcinoma and gastric cancer, in addition to lymphoma.

Viracta CEO Ivor Royston, M.D., says in a statement that he was encouraged by the study presented at ASCO because positive responses to the combination treatment were seen in both T cell and B cell lymphomas. The company plans to initiate the phase 2 study in the third quarter of this year.