Abstract 1730: A novel chimeric virus-like drug conjugate (VDC) for the potential treatment of HPV-positive tumors

Abstract Introduction: Human papillomavirus (HPV) virus-like particles (VLPs) bind to a wide variety of tumor types via modified glycosaminoglycans (GAGs) found on the tumor cell surface. This finding led to the development of the investigational virus-like drug conjugate (VDC) belzupacap sarotalocan (bel-sar, formerly AU-011), an HPV-derived VLP conjugated to a light-activated cytotoxic payload. When activated by near-infrared light, bel-sar induced rapid tumor necrosis resulting in pro-immunogenic cell death, release of tumor neoantigens and long-term anti-tumor immunity in the TC-1 tumor model. When E6 and E7 expressing TC-1 mouse tumors were treated with the VDC, E7-specific T-cells were detected in the absence of provided tumor antigens. A novel chimeric VDC (cVDC) is now in development, in which E6 and E7 are fused to the L2 capsid protein as a means to potentially further enhance the observed anti-tumor response. This cVDC could allow for the targeted cytotoxicity of HPV-positive tumors in addition to the release of supplemental tumor antigens E6 and E7 within the now pro-immunogenic tumor milieu, potentially leading to a long term anti-tumor response. Methods: The detoxified sequences of E6 and E7 were engineered as one fusion polypeptide on the C-terminus of the L2 minor capsid protein. Both L2/E6/E7 and L2/E7/E6 protein expression vectors were generated to determine if the order of the proteins impacted L2’s ability to co-assemble with L1, the major capsid protein. The plasmids were co-expressed alongside L1 using the mammalian 293TT expression system. Results: Both the L2/E6/E7 and L2/E7/E7 fusion proteins were expressed and co-assembled with L1 into chimeric VLPs. Fusion protein expression was validated by western blots for L2, E6 and E7, and VLPs were confirmed by electron microscopy. Conclusions: Preliminary data indicate that chimeric VDCs containing E6 and E7 can successfully be generated using the 293TT mammalian expression system. Studies evaluating the cytotoxicity and E6 and E7 immunogenicity of the cVDC as well as the impact on tumor targeting are underway. Citation Format: Rhonda C. Kines, Anneli Savinainen, Elisabet de los Pinos, John T. Schiller. A novel chimeric virus-like drug conjugate (VDC) for the potential treatment of HPV-positive tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1730.