Abstract 6660: The novel codon-modified Zika virus CDX-602 shows anti-tumor efficacy and remodels the tumor microenvironment in preclinical models

Abstract Multiple oncolytic viruses have been shown to induce multifaceted changes in the tumor microenvironment, that ultimately support induction of anti-tumor immune responses. We have previously demonstrated that CodaLytic, a codon-modified influenza virus, can kickstart the cancer immunity cycle at various steps in several mouse models with differing baseline immune contextures. Here, we are describing the activity of a new codon-modified virotherapeutic derived from the same synthetic viral engineering platform [Coleman et al., Science 2008]. Zika virus strain MR766 was synthetically codon-modified at 664 positions in the envelop gene to yield CDX-602. Virus was originally passaged in Vero cells and working stocks were expanded in BSR-T7 cells for in vivo use after titration on MA104.1 cells. Efficacy after intratumoral injection of 107 PFU/dose CDX-602 alone or in combination with 200 μg/dose αPD-1 blockade (RMP1-14, i.p.) was determined in subcutaneous B16-F10 melanoma and orthotopic EMT6 breast cancer models (n = 10). Changes in the tumor immune infiltrate were characterized using flow cytometry 6 or 8 days after treatment initiation, respectively (n = 5). In the immunotherapy-resistant B16-F10 model, CDX-602 monotherapy led to highly reproducible tumor growth inhibition (TGI, 52%, p < 0.0001 vs vehicle control), resulting in modest, but significant prolongation of median survival (25%, p < 0.01). Anti-tumor efficacy correlated with increased tumor immune infiltration with CD4+ and CD8+ T cells (R2 = 0.68 and 0.67, respectively, p < 0.01). Importantly, frequencies of cross-presenting dendritic cells (cDC) were increased 3.8-fold (p < 0.0001) after virus treatment, while no compensatory influx of CD206+ macrophages was observed, suggesting immune contexture changes conducive to anti-tumor immune induction. Efficacy was confirmed in the EMT6 model, in which monotherapy TGI was 44% and thus on par with αPD-1 blockade (50%, both p < 0.0001 vs control). Combination viroimmunotherapy in this model further improved efficacy, leading to 71% TGI and a doubling in complete regressions to 40%. Inclusion of CDX-602 in the treatment regimen led to similar changes in immune infiltration, in particular recruitment of CD8+ T cells and cDCs (9.7-fold and 6.9-fold increase after combination, respectively). Additional ex vivo analyses to confirm induction of anti-tumor immune responses are ongoing. Taken together, this preclinical data establishes CDX-602 as a novel virotherapeutic candidate that engages multiple mechanisms of action that contribute to anti-tumor activity. CDX-602 is the second virotherapeutic candidate derived from Codagenix’s codon modification platform, further supporting the utility of this synthetic viral engineering technology for viroimmunotherapy of cancer and highlighting its potential across multiple viral species. Citation Format: Nusrat Jahan, Yiwen Zhao, Katarina Blagovic, Ying Wang, J Robert Coleman, Steffen Mueller, Johanna K. Kaufmann. The novel codon-modified Zika virus CDX-602 shows anti-tumor efficacy and remodels the tumor microenvironment in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6660.