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Viracta Eyes FDA Accelerated Approval Path for Nana-val in EBV-Positive PTCL

NEW YORK – Viracta Therapeutics, buoyed by positive Phase II trial data, on Monday said it will seek accelerated approval for Nana-val (nanatinostat plus valganciclovir) in the US as a treatment for Epstein-Barr virus (EBV)-positive peripheral T-cell lymphoma.

The treatment comprises the histone deacetylase (HDAC) inhibitor nanatinostat combined with the antiviral agent valganciclovir. Nanatinostat blocks isoforms of Class I HDACs, which then induces viral genes epigenetically silenced in EBV-related cancers.

The pivotal NAVAL-1 clinical trial includes multiple patient cohorts. In the relapsed or refractory EBV-positive peripheral T-cell lymphoma cohort, 20 patients were randomized to receive either Nana-val or nanatinostat monotherapy. Patients could cross over to the Nana-val arm in the event they didn't respond to nanatinostat monotherapy after six weeks.

In the 10-patient intent-to-treat population, the overall response rate was 50 percent in the Nana-val arm, and the complete response rate was 20 percent. In the seven-patient efficacy-evaluable population, the overall response rate was 71 percent and the complete response rate was 29 percent.

Meanwhile, in the nanatinostat monotherapy arm, the overall response rate was 10 percent among 10 intent-to-treat patients and no one had a complete response. The overall response rate was 13 percent among eight patients in the efficacy-evaluable population. Five patients on nanatinostat monotherapy crossed over to receive Nana-val, and two of them remain on treatment with stable disease as of a data cutoff in early February.  

According to San Diego-based Viracta, the treatment was well-tolerated in the NAVAL-1 trial, and side effects were generally manageable or reversible.

The firm plans to pursue the accelerated approval pathway midyear with the US Food and Drug Administration and share topline results from the second stage of the NAVAL-1 trial during the third quarter of 2024.

Viracta is also evaluating Nana-val, both alone and in combination with Merck's checkpoint inhibitor Keytruda (pembrolizumab), in multiple EBV-positive solid tumor types in a Phase Ib/II clinical trial.