Abstract 4103: Novel mRNA-encoded HPV vaccine with APC maturation signal and endolysosomal trafficking domain demonstrates superior T cell-mediated immunogenicity and efficacious tumor clearance in vivo

Abstract Human Papillomavirus (HPV), particularly HPV16, is a known causative agent of cancers in various anatomical sites, notably the anogenital and oropharyngeal regions. Despite the availability of prophylactic HPV vaccines for almost two decades, vaccination rates among young females, who are at a heightened risk for cervical intraepithelial neoplasia (CIN) and subsequent invasive cancer, remain suboptimal. The current standard of care for cervical cancer, involving invasive surgery and chemotherapy-based treatments, underscores the pressing need for safer and more effective therapeutics to enhance patient survival and quality of life. In this context, while several HPV16-E6/E7 targeted therapeutic vaccines are in development and clinical trials, their clinical efficacy has been limited due to inadequate antigen presentation and suboptimal immunogenicity. Addressing this, our team has developed a novel, highly immunogenic mRNA therapeutic cancer vaccine, engineered to activate a robust T cell-mediated adaptive immune response and exhibit strong anti-tumor potential. Our innovative approach includes the design of an HPV16-E6/E7 mRNA vaccine (ABO2101) that incorporates a unique antigen-expressing cassette. This cassette features endolysosomal trafficking domains and antigen presenting cell (APC) activation stimulators, enhancing both Class I and Class II antigen presentation and APC maturation, thereby amplifying antigen-specific T cell responses. In both murine and human-derived experimental models, ABO2101 has demonstrated a significantly more potent adaptive T cell response against HPV16 antigens compared to other HPV16 mRNA therapeutic vaccines. In antitumor efficacy evaluations using TC-1 tumor-bearing mice, ABO2101 single-dose administration successfully eradicated both early-stage (50 mm³) and advanced (500 mm³) tumors. This was accompanied by a marked increase in HPV16-specific CD8+ cytotoxic T lymphocytes within the tumor microenvironment. Moreover, in prophylactic and adjuvant therapy models, ABO2101 prevented tumor growth across various dosages, indicating its robust preventative capabilities. Further, the combination of ABO2101 with immune checkpoint inhibitors, including PD-1 and CTLA-4 antibodies, displayed a synergistic effect in both immune-oncology sensitive and resistant animal models, suggesting a potential for combinational clinical therapy. In conclusion, our development of ABO2101, a mRNA-based HPV16-E6/E7 therapeutic cancer vaccine inclusive of APC maturation signals, represents a groundbreaking advancement in HPV-associated cancer treatment, as supported by our compelling preclinical data. Citation Format: Liang Du, Hongya Han, Jingshu Ma, Zhenxing Yang, Jinjuan Mao, Jijun Yuan, Bo Ying. Novel mRNA-encoded HPV vaccine with APC maturation signal and endolysosomal trafficking domain demonstrates superior T cell-mediated immunogenicity and efficacious tumor clearance in vivo 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 (6Suppl): Abstract nr 4103.