On August 14, 2024 Viracta Therapeutics, Inc. (Nasdaq: VIRX), a clinical-stage precision oncology company focused on the treatment and prevention of virus-associated cancers that impact patients worldwide, reported positive Phase 2 NAVAL-1 trial results from Stages 1 and 2 of the relapsed or refractory (R/R) Epstein-Barr virus-positive (EBV+) peripheral T-cell lymphoma (PTCL) cohort (Press release, Viracta Therapeutics, AUG 14, 2024, View Source,-Regulatory-Progress,-and-Updated-Nana-val-Clinical-Development-Plan [SID1234645931]). Additionally, the Company received productive feedback from its meeting with the U.S. Food and Drug Administration (FDA), providing clarity on the potential regulatory path to initial registration of Nana-val in patients with R/R EBV+ PTCL. Based on FDA’s feedback, Viracta plans to begin a randomized controlled trial (RCT) of Nana-val in the second half of 2025.
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"We are pleased to present important additional data from our NAVAL-1 trial, which further supports Nana-val’s potential to address the high unmet medical needs of patients living with relapsed or refractory EBV-positive PTCL," said Darrel P. Cohen, M.D., Ph.D., Chief Medical Officer of Viracta. "Nana-val demonstrated substantial antitumor activity with a generally well-tolerated safety profile across Stage 1 and Stage 2 of the relapsed or refractory EBV-positive PTCL cohort, with a median duration of response that has not yet been reached. We are also encouraged by the particularly robust clinical responses observed in the second-line EBV-positive PTCL subgroup."
Mark Rothera, President and Chief Executive Officer of Viracta, added, "Aligning with the FDA on the potential path forward in relapsed or refractory EBV-positive PTCL marks a critical step towards bringing Nana-val to patients. EBV-positive PTCL is an aggressive cancer with survival rates that decline precipitously 12-24 months after diagnosis. Published literature suggests that EBV-positive lymphomas are a distinct oncological disease associated with poorer survival outcomes than EBV-negative lymphomas. We believe it is critical to treat these patients as early as possible with an EBV-targeted therapy to improve patient outcomes. Our updated Nana-val clinical development plan is designed to address this urgent need and expedite a randomized controlled trial, which we plan to initiate in 2025 to support potential registration."
Key Takeaways from the R/R EBV+ PTCL Cohort of the Phase 2 NAVAL-1 Trial
Overview: A total of 21 patients with primarily Stage III-IV disease (who had received ≥1 [median 2] prior systemic PTCL therapies) received nanatinostat (20 mg orally once daily, 4 days/week) in combination with valganciclovir (900 mg orally once daily, 7 days/week) across the first two stages of the study. Data generated from the expansion phase of the R/R EBV+ PTCL cohort may be shared in future updates.
As of the June 28, 2024 data cutoff, combined Stages 1 and 2 data demonstrated:
In the R/R EBV+ PTCL population:
The overall response rate (ORR) was 33% and the complete response rate (CRR) was 19% in the intent-to-treat (ITT) population (n=21); the ORR was 41% and the CRR was 24% in the efficacy-evaluable (EE) population (n=17).
In the second-line EBV+ PTCL subpopulation:
The ORR was 60% and the CRR was 30% in the ITT population (n=10); the ORR was 67% and the CRR was 33% in the EE population (n=9).
Median duration of response (DOR) has not yet been reached.
Two responding patients proceeded to hematopoietic stem-cell transplant without relapse, one of whom remains in response over 16 months.
Nana-val was generally well-tolerated:
The most common treatment-related adverse events were fatigue, nausea, decreased appetite, diarrhea, platelet count decreased, and anemia. These adverse events were primarily mild to moderate in severity and generally manageable or reversible.
Nana-val Clinical Development Plan: Next Steps
Based on the Company’s meeting with FDA and the particularly robust response rates observed in the second-line treatment setting, Viracta will focus Nana-val’s clinical development on patients with R/R EBV+ PTCL as follows: First, the Company will focus the primary analysis on the second-line EBV+ PTCL subpopulation in the ongoing NAVAL-1 trial’s expansion phase. Second, the Company plans to begin an RCT of Nana-val in the second-line treatment of EBV+ PTCL patients in 2025. Viracta believes this strategy will best position Nana-val for a potential NDA filing in 2026 for accelerated approval based on an interim analysis of second-line EBV+ PTCL patient data from the NAVAL-1 trial, provided that the ORR and DOR are compelling and the RCT is well underway. In addition, it creates the opportunity for accelerated approval based on final analysis of NAVAL-1 trial data, or for accelerated or full approval based on the outcomes of the RCT at interim or final analysis, respectively.
Corporate Update
Viracta has aligned resources to prioritize its EBV+ lymphoma program and plans to deliver on key potential Nana-val development milestones as follows:
Pause the EBV+ solid tumor program to focus resources on the more advanced EBV+ lymphoma program.
The recommended Phase 2 dose in patients with advanced EBV+ solid tumors is expected to be determined in the second half of 2024.
Report additional data from the ongoing expansion phase of the NAVAL-1 trial in second-line EBV+ PTCL patients in the fourth quarter of 2024.
Report Stage 1 data from patients with R/R EBV+ diffuse large B-cell lymphoma (DLBCL) in the first half of 2025.
Meet with the FDA to finalize the proposed RCT design in the second-line treatment of patients with EBV+ PTCL in the first half of 2025.
Initiate the RCT in the second half of 2025.
Present interim analysis outcomes from the expansion phase of the NAVAL-1 trial in second-line EBV+ PTCL patients in 2026.
File NDA for accelerated approval in 2026 based on interim analysis of the NAVAL-1 trial’s expansion cohort.
Along with this pipeline reprioritization, a reduction in force has been implemented that impacts approximately 23% of the Company’s employees.
Conference Call
Viracta will host an investor call on Wednesday, August 14 at 8:30 a.m. ET to discuss the positive Phase 2 NAVAL-1 trial results from Stages 1 and 2 of the R/R EBV+ PTCL cohort. A live question and answer session will follow the formal presentation. To register, click here.
About the NAVAL-1 Trial
NAVAL-1 (NCT05011058) is a global, multicenter, clinical trial of Nana-val in patients with relapsed or refractory (R/R) Epstein-Barr virus-positive (EBV+) lymphoma. This trial employs a Simon two-stage design where, in Stage 1, participants are enrolled into one of three indication cohorts based on EBV+ lymphoma subtype. If two objective responses are achieved within a lymphoma subtype in Stage 1 (n=10), then additional patients will be enrolled in Stage 2 for a total of 21 patients. EBV+ lymphoma subtypes demonstrating promising antitumor activity in Stage 2 may be further expanded following discussion with regulators to potentially support registration.
About Nana-val (Nanatinostat and Valganciclovir)
Nanatinostat is an orally available histone deacetylase (HDAC) inhibitor being developed by Viracta. Nanatinostat is selective for specific isoforms of Class I HDACs, which are key to inducing viral genes that are epigenetically silenced in Epstein-Barr virus (EBV)-associated malignancies. Nanatinostat is currently being investigated in combination with the antiviral agent valganciclovir as an all-oral combination therapy, Nana-val, in various subtypes of EBV-associated malignancies. Ongoing trials include a potentially registrational, global, multicenter, open-label Phase 2 basket trial in multiple subtypes of relapsed or refractory (R/R) EBV+ lymphoma (NAVAL-1) as well as a multinational Phase 1b/2 clinical trial in patients with recurrent or metastatic (R/M) EBV+ NPC and other advanced EBV+ solid tumors.
About Peripheral T-Cell Lymphoma
T-cell lymphomas comprise a heterogeneous group of rare and aggressive malignancies, including peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) and angioimmunoblastic T-cell lymphoma (AITL). There are approximately 5,600 newly diagnosed T-cell lymphoma patients and approximately 2,600 newly diagnosed PTCL-NOS and AITL patients in the U.S. annually. Approximately 70% of these patients are either refractory to first-line therapy, or eventually experience relapse of their disease. Clinical trials are currently recommended for all lines of PTCL therapy, and most patients with R/R PTCL have poor outcomes, with median progression-free survival and median overall survival times reported to be 3.7 and 6.5 months, respectively. Approximately 40% to 65% of PTCL is associated with EBV, the incidence of EBV+ PTCL varies by geography, and reported outcomes for patients with EBV+ PTCL are inferior to those whose disease is EBV-negative. There is no approved targeted treatment specific for EBV+ PTCL, and therefore this represents a high unmet medical need.
About EBV-Associated Cancers
Approximately 90% of the world’s adult population is infected with EBV. Infections are commonly asymptomatic or associated with mononucleosis. Following infection, the virus remains latent in a small subset of cells for the duration of the patient’s life. Cells containing latent virus are increasingly susceptible to malignant transformation. Patients who are immunocompromised are at an increased risk of developing EBV-positive (EBV+) lymphomas. EBV is estimated to be associated with approximately 2% of the global cancer burden including lymphoma, nasopharyngeal carcinoma (NPC), and gastric cancer.