Abstract A014: Low -neurovirulence wild-type Zika virus strains induce durable tumor regression and survival benefit in patient-derived glioblastoma models

Abstract Glioblastoma (GBM) remains uniformly lethal due to therapeutic resistance driven by the blood–brain barrier, tumor heterogeneity, and profound immunosuppression. Oncolytic viruses offer a strategy to overcome these barriers. Zika virus (ZIKV) is a uniquely appropriate oncolytic virus candidate as it is neurotropic and selectively targets glioblastoma stem cells (GSCs). However, strain-specific efficacy and safety profiles remain incompletely defined. We evaluated two naturally occurring, low-neurovirulence wild-type ZIKV strains—ZIKV Nicaragua/2016 (ZIKVN) and ZIKV SJRP/2016 (ZIKVS). Both strains were found to be safe in a controlled human clinical trial (NCT05123222). Concurrently, viral infection, replication, and cytotoxicity were quantified in 12 patient-derived GSC lines, CRISPR-engineered AXL knockout lines, and glioblastoma organoids. Therapeutic efficacy was assessed in heterotopic and orthotopic patient derived xenograft models. using bioluminescence imaging and survival analyses. Both ZIKVN and ZIKVS efficiently infected GSCs, achieving >50% infection by 24–48 hours at MOI 1 in high-AXL–expressing lines and inducing dose-dependent apoptosis (Annexin V+ cells increased 3- to 6-fold). AXL knockout reduced infection and apoptosis by >80%, confirming receptor-mediated entry. In organoid models, ZIKVS selectively eliminated GSCs while sparing normal neural cells. In subcutaneous xenografts, intratumoral ZIKV caused rapid tumor regression to below detection limits within 10–14 days. ZIKVN achieved 100% survival at 120 days (study completion), whereas MR766 controls showed only 37% survival due to significant weight loss. In orthotopic intracranial models (n=65), both ZIKVN and ZIKVS cleared established tumors within ∼12 days. ZIKVN produced an 80% complete response rate but was associated with delayed weight loss in 27% of responders. In contrast, ZIKVS yielded 63% complete responses and 80% long-term survival with no treatment-related morbidity. Dose de-escalation demonstrated efficacy at doses as low as 102 PFU, and intravenous ZIKVS achieved 75–80% complete responses with 80% survival at 90 days. These data identify ZIKVS as a highly effective and well-tolerated oncolytic virus candidate for GBM. Together with existing human safety data, this work provides strong quantitative preclinical justification for clinical evaluation of ZIKVS in recurrent glioblastoma. Citation Format: Parvez Akhtar, Samuel Zwernik, Deb Donohoe, Stephen Whitehead, Richard Rovin. Low -neurovirulence wild-type Zika virus strains induce durable tumor regression and survival benefit in patient-derived glioblastoma models [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Brain Cancer; 2026 Mar 23-25; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(6_Suppl):Abstract nr A014.