On June 11, 2026 Theriva Biologics, Inc. (NYSE American: TOVX), a diversified clinical-stage company developing therapeutics designed to treat cancer and related diseases in areas of high unmet need, reported that clinical and translational results from VCN-01’s Phase 1 clinical trial in Head & Neck Squamous Cell Carcinoma (HNSCC) were recently published on-line first in the journal Clinical Cancer Research. The article, titled "Phase I trial of intravenous VCN-01 oncolytic adenovirus and durvalumab in patients with head and neck metastatic squamous cell carcinoma refractory to immunotherapy", can be read here.

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"We are very excited to see Clinical Cancer Research share the VCN-01 results in immunotherapy-refractory metastatic HNSCC patients with the broad oncology community," said Ricard Mesia (Catalan Institute of Oncology, ICO), expert on HNSCC and coordinating investigator in this study. "The trial demonstrates the ability of VCN-01 to resensitize tumors from these heavily pretreated patients to the immune checkpoint inhibitor durvalumab. Pharmacokinetic, tissue biopsy, radiomic and transcriptomic results from the study all support the VCN-01 stroma-degrading mode-of-action, being investigated to enhance tumor penetration by VCN-01 and coadministered therapies and enable/enhance an anti-tumor immune response. There are very few treatment options available to immunotherapy-refractory metastatic HNSCC patients, and the clinically impactful findings from this report encourage further clinical development of VCN-01 with immune checkpoint inhibitors or other immune modulating anticancer therapies."

Data summary – VCN-01 Phase 1 clinical trial (NCT03799744) in metastatic, immunotherapy-refractory Head & Neck Squamous Cell Carcinoma (HNSCC)

The trial enrolled 20 adult patients with refractory or metastatic HNSCC, whose disease progressed despite previous therapies, including anti-PD-(L)1 immune checkpoint inhibitors. Six patients were enrolled into the concomitant Arm I LD of the study and were administered IV low dose VCN-01 (3.3E12 virus particles; LD) four hours prior to a fixed IV dose of durvalumab (1500 mg/q4w). Eight patients were enrolled into the sequential Arm II LD of the study, receiving low dose IV VCN-01 14 days prior to IV durvalumab administration. An additional six patients were entered into Arm II HD, receiving high dose IV VCN-01 (1.0E13 virus particles; HD) 14 days prior to IV durvalumab administration.

Median progression-free survival (PFS) was 1.6 months in Arm I LD, 3.7 months in Arm II LD, and 2.1 months in Arm II HD.
Median overall survival (OS) was 10.3 months in Arm I LD, 15.5 months in Arm II LD, and 17.3 months in Arm II HD.
Circulating levels of the stroma-degrading hyaluronidase enzyme PH20 (expressed during selective VCN-01 intratumoral replication) increased significantly after VCN-01 administration in all tested patients, peaking on day 3-8 for most patients and detectable until day 28 in 11 of 12 patients.
Similarly, VCN-01 viral genome levels detected in patient blood exhibited an initial peak immediately following administration and a secondary peak on day 3-8, consistent with continued viral replication in tumors followed by a return of virus to circulation.
Upregulation of CD8 and IDO was observed in tumor biopsy samples, consistent with increased tumor infiltration by activated cytotoxic T cells – historically associated with increased HNSCC patient survival. Diminished levels of FoxP3, CD25, and CTLA4 were also observed, consistent with a reduction in tumor Tregs and inhibition of tumor immunosuppression.
Tumor biopsies revealed upregulation of PD-1 and PD-L1 in most patients following VCN-01 administration that correlated with patient survival, suggesting that immune system activity and heightened PD-L1 expression in tumors contributed to the improved outcomes from VCN-01 and durvalumab combination.

(Press release, Theriva Biologics, JUN 11, 2026, View Source [SID1234666575])