{"url_path":"/sec/tovx/8-k/2026-06-11/item-8-01","section_key":"item-8-01","section_title":"Item 8.01 Other Events.**","topic":"sec","document":{"doc_type":"8-K","doc_date":"2026-06-11","source_url":"https://www.sec.gov/Archives/edgar/data/894158/0001104659-26-072633-index.html","accession_number":"0001104659-26-072633","cik":"0000894158","ticker":"TOVX","issuer_name":"Theriva Biologics, Inc.","edgar_url":"https://www.sec.gov/Archives/edgar/data/894158/0001104659-26-072633-index.html","primary_entity_key":"0000894158","primary_entity_name":"Theriva Biologics, Inc."},"word_count":364,"has_tables":true,"body_markdown":"**Item 8.01. Other Events.** \n\n \n\nOn June 11, 2026, the\nCompany issued a press release announcing that clinical and translational results from VCN-01’s Phase 1 clinical trial in HNSCC\nwere recently published on-line first in the journal Clinical Cancer Research.\n\n \n\nThe trial enrolled 20\nadult patients with refractory or metastatic HNSCC, whose disease progressed despite previous therapies, including anti-PD-(L)1 immune\ncheckpoint inhibitors. Six patients were enrolled into the concomitant Arm I LD of the study and were administered IV low dose VCN-01\n(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\nArm II LD of the study, receiving low dose IV VCN-01 14 days prior to IV durvalumab administration. An additional six patients were entered\ninto Arm II HD, receiving high dose IV VCN-01 (1.0E13 virus particles; HD) 14 days prior to IV durvalumab administration.\n\n \n\n·Median progression-free survival (PFS) was 1.6\nmonths in Arm I LD, 3.7 months in Arm II LD, and 2.1 months in Arm II HD.\n\n·Median overall survival (OS) was 10.3 months\nin Arm I LD, 15.5 months in Arm II LD, and 17.3 months in Arm II HD.\n\n·Circulating levels of the stroma-degrading hyaluronidase\nenzyme PH20 (expressed during selective VCN-01 intratumoral replication) increased significantly after VCN-01 administration in all tested\npatients, peaking on day 3-8 for most patients and detectable until day 28 in 11 of 12 patients.\n\n·Similarly, VCN-01 viral genome levels detected\nin patient blood exhibited an initial peak immediately following administration and a secondary peak on day 3-8, consistent with continued\nviral replication in tumors followed by a return of virus to circulation.\n\n·Upregulation of CD8 and IDO was observed in tumor\nbiopsy samples, implying increased tumor infiltration with activated cytotoxic T cells – historically associated with increased\nHNSCC patient survival. Diminished levels of FoxP3, CD25, and CTLA4 were also observed, consistent with a reduction in tumor Tregs and\ninhibition of tumor immunosuppression.\n\n·Tumor biopsies revealed upregulation of PD-1\nand PD-L1 in most patients following VCN-01 administration that correlated with patient survival, suggesting that immune system activity\nand heightened PD-L1 expression in tumors contributed to the improved outcomes from VCN-01 and durvalumab combination."}