TPS6134 Background: Head and neck squamous cell carcinoma (HNSCC) has high recurrence rates despite standard perioperative treatments such as surgery with adjuvant radiotherapy and/or chemotherapy, with about 35% of patients relapsing. Neoadjuvant immune checkpoint therapy has shown promise: in the Phase III KEYNOTE-689 trial, adding perioperative pembrolizumab to standard care significantly improved median event-free survival (51.8 vs 30.4 months), leading to FDA approval in June 2025. However, only 9.4% of patients achieved a major pathologic response, a key predictor of reduced relapse and a surrogate for long-term benefit in other cancers. This low response rate underscores the need for more effective strategies to expand and deepen durable immune-mediated tumor responses in HNSCC. Our strategy is to develop a combination immunotherapy/gene therapy targeting the immunosuppressive myeloid populations such as tumor-associated macrophages (TAMs) and neutrophils (TANs), which are increasingly recognized as key mediators of immune evasion and poor outcomes. VLPONC-01 is a novel, non-replicating, viral particle-based therapy to target TAMs and TANs. VLPONC-01 efficiently delivers self-amplifying RNA (saRNA) encoding an engineered human Interleukin 12 (IL-12) gene into cells in the tumor microenvironment (TME), leveraging the natural tropism of Venezuelan equine encephalitis virus (VEEV). Within transfected cells, the RNA amplifies itself and directs the cell to produce and secrete IL-12 protein. The released IL-12 is expected to concentrate in the TME, where it activates immune cells and enhances their ability to attack cancer cells. Methods: This is a first-in-human, phase 1, open-label trial evaluating the safety and early efficacy of intratumoral administration of VLPONC-01 in patients with HNSCC, focusing on its ability to reduce tumor burden and lessen surgical morbidity. Furthermore, it will characterize IL-12-driven alterations in the tumor microenvironment and determine the synergistic potential of combining this approach with anti-PD-1 immunotherapy. The study includes two cohorts: Cohort A tests weekly intratumoral injection in recurrent and/or metastatic tumor patients to assess safety and determine dose levels, while Cohort C randomizes patients with resectable tumors into three groups to receive low-dose VLPONC-01 plus pembrolizumab, high-dose VLPONC-01 plus pembrolizumab, or pembrolizumab alone, prior to surgery. Outcomes include dose-limiting toxicities, surgical delays, systemic cytokine responses, and tumor response assessed by imaging and pathology. Clinical trial information: NCT06736379 .

Abstract Immunosuppressive myeloid cells such as tumor-associated macrophages (TAMs) and neutrophils (TANs) contribute to resistance against immune checkpoint therapies by fostering a suppressive tumor microenvironment (TME). To overcome this barrier, we developed a single-cycle alphavirus replicon particle (VRP) vector encapsulating self-amplifying RNA (saRNA) encoding interleukin-12 (IL-12) for intratumoral delivery, leveraging the natural tropism of alphaviruses for myeloid cells. The VRP was engineered with a capsid nuclear localization signal mutation to enhance transgene expression and reduce host cell toxicity. In preclinical studies, single-cell RNA sequencing of treated mouse 4T1 breast carcinoma tumors and draining lymph nodes revealed that IL12-VRP preferentially transduced M2-like TAMs and TANs, reprogramming them toward pro-inflammatory phenotypes via interferon signaling. This effect was further amplified by IL-12 expression, leading to expansion of pro-inflammatory Nos2+ macrophage and neutrophil populations. IL12-VRP also activated cytotoxic NK and T cells, inducing IFN-γ expression and enhancing anti-tumor immunity. Compared to lipid nanoparticle-based delivery of the same saRNA replicon, IL12-VRP achieved superior tumor control in the MC38 colorectal model with ∼1000-fold lower RNA gene copies in the dose. IL12-VRP suppressed MOC2 head and neck model tumor growth, prevented nodal and lung metastases, and remodeled immune landscapes in both tumors and lymphoid tissues. CT26 colorectal carcinoma model mice treated with IL12-VRP exhibited tumor reduction, durable systemic immune memory and rejected subsequent tumor rechallenge. These findings establish IL12-VRP as a potent immunomodulatory platform capable of reprogramming myeloid cells and enhancing adaptive immunity. This approach may improve outcomes in myeloid-dominant TMEs and augment current immunotherapies. Ongoing clinical evaluation (NCT06736379) will determine its translational potential. Citation Format: Forrest Bowling, Momoko Ishikawa, Dhanya Nambiar, Jayalaxmi Sastri, Keiko Ishimoto, Fumiya Tao, Koyo Takahashi, Ivan Stepanek, Hongbin Cao, Davis Leitner, Kenta Matsuda, Fred Baik, John Sunwoo, Quynh Thu Le, Jonathan Smith, Wataru Akahata. Alphavirus replicon expressing IL-12 reprograms tumor-associated macrophages and neutrophils and induces anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2894.

Abstract Chikungunya virus (CHIKV) causes periodic outbreaks and is endemic in more than 110 countries. VIMKUNYA, a CHIKV virus-like particle (CHIKV VLP) vaccine, was recently approved by regulators in the United States, European Union, and United Kingdom. Efficacy of VIMKUNYA in endemic settings is difficult to evaluate due to outbreak unpredictability. We used cynomolgus macaques, which model human CHIKV viremia and disease, to assess CHIKV VLP vaccine efficacy. Doses as low as 1.25 μg of CHIKV VLP with aluminum hydroxide adjuvant and passively transferred IgG from vaccinated humans significantly reduced viremia, disease, and joint pathology. Animals that received IgG doses resulting in mean reciprocal 80% neutralization titers of 35, well below the predicted protective threshold of ≥100, exhibited improved clinical outcomes compared with CHIKV-infected control animals, suggesting clinical benefits may occur at lower antibody levels. These findings demonstrate immunogenicity and protective efficacy of CHIKV VLP and relevance of neutralizing antibodies in protection, reinforcing its use in humans to protect against chikungunya disease.

Background There remains a significant need to eliminate the risk of recurrence of resected cancers. Cancer vaccines are well tolerated and activate tumor-specific immune effectors and lead to long-term survival in some patients. We hypothesized that vaccination with alphaviral replicon particles encoding tumor associated antigens would generate clinically significant antitumor immunity to enable prolonged overall survival (OS) in patients with both metastatic and resected cancer.Methods OS was monitored for patients with stage IV cancer treated in a phase I study of virus-like replicon particle (VRP)-carcinoembryonic antigen (CEA), an alphaviral replicon particle encoding a modified CEA. An expansion cohort of patients (n=12) with resected stage III colorectal cancer who had completed their standard postoperative adjuvant chemotherapy was administered VRP-CEA every 3 weeks for a total of 4 immunizations. OS and relapse-free survival (RFS) were determined, as well as preimmunization and postimmunization cellular and humoral immunity.Results Among the patients with stage IV cancer, median follow-up was 10.9 years and 5-year survival was 17%, (95% CI 6% to 33%). Among the patients with stage III cancer, the 5-year RFS was 75%, (95%CI 40% to 91%); no deaths were observed. At a median follow-up of 5.8 years (range: 3.9–7.0 years) all patients were still alive. All patients demonstrated CEA-specific humoral immunity. Patients with stage III cancer had an increase in CD8 +TEM (in 10/12) and decrease in FOXP3 +Tregs (in 10/12) following vaccination. Further, CEA-specific, IFNγ-producing CD8+granzyme B+TCM cells were increased.Conclusions VRP-CEA induces antigen-specific effector T cells while decreasing Tregs, suggesting favorable immune modulation. Long-term survivors were identified in both cohorts, suggesting the OS may be prolonged.