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

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.

Abstract 5331: Biological assessment of the virus-like drug conjugate AU-011 to specifically target a breadth of human cancer types

Introduction: AU-011 is a virus-like drug conjugate based on a human papillomavirus (HPV) derived virus-like particle (VLP) conjugated to a light-activated cytotoxic payload (IRDye700DX) currently in Phase II clinical trials for the treatment of primary choroidal melanoma. When activated by near-infrared light, AU-011 has a dual mechanism of action inducing rapid, tumor necrosis resulting in pro-immunogenic cell death and long-term anti-tumor immunity. HPV-derived VLPs bind a wide variety of tumor types via modified heparan sulfate proteoglycans (HSPG) found on the tumor surface. This study explores the breadth of tumor types that could benefit from a targeted treatment intervention with AU-011 and surveys genes and biological pathways that are positively and negatively associated with this targeting.

Methods: AU-011 binding, cytotoxicity and HSPG specificity was surveyed in 127 tumor cell lines representing breast, cervical, CNS (glioblastoma, astrocytoma), colon, esophageal, gastric, hematopoietic, lung, liver, melanoma (cutaneous or choroidal), oropharyngeal, ovarian, pancreas, prostate, renal, urothelial and skin cancers, and sarcomas (osteosarcomas, mesotheliomas, retinoblastomas). Publicly available gene expression data for 101 of these cell lines was cross-referenced to identify gene signatures that correlated (either positively or negatively) with AU-011 binding and cytotoxicity.

Results: AU-011 activity was observed for every tumor type examined, with some variation across several of the types. HSPG-specific binding was well-conserved across all tumor types tested except for most cells of lymphoid origin which are known to have HSPG deficiency. Collectively the tumor-derived cell lines exhibiting average binding EC50s < 100 pM were ocular cancers (choroidal melanomas and retinoblastomas) and solid tumors including urothelial, bone, breast, cervical, CNS, colon, cutaneous melanoma, esophageal, gastric, liver, lung, skin, oropharyngeal, ovarian, and renal. Urothelial, bone, breast, cervical, CNS, esophageal, gastric, liver, lung, melanoma, skin, ovarian, renal and retinoblastoma all exhibited AU-011 mediated cytotoxicity with an average potency of < 100pM. Correlative gene expression analysis demonstrated a strong association between AU-011 activity and genes involved in epithelial-to-mesenchymal transition, glycosaminoglycan biosynthesis/metabolism, and extracellular matrix interactions. Expression signatures for ribosomal activity and protein translation were negatively associated with AU-011 binding and activity.

Conclusions: Collectively these data demonstrate the wide potential applicability of AU-011 to target a number of tumor types, particularly those derived from neural or epithelial lineages. Importantly, a large portion of these tumors are accessible making their AU-011 targeting clinically translatable.

Citation Format: Rhonda C. Kines, Nathan R. Fons, Elisabet de los Pinos, John T. Schiller. Biological assessment of the virus-like drug conjugate AU-011 to specifically target a breadth of human cancer types [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5331.

HPV based photodynamic therapy: a new approach for anti-cancer therapy (VAC12P.1019)

A new method of targeted photodynamic therapy (PDT) is proposed for potentiating anti-tumor immunity. Human papillomavirus (HPV) virus-like particles (VLPs) bind a broad range of tumor types both, in vitro and in vivo, but do not bind healthy, intact tissues. We have linked a photosensitizer dye, IR700, to the HPV VLPs and applied the dye-coupled particles (IR700-VLP) to tumor cells. When exposed to 690nm light, the bound conjugates induced immediate necrotic-like cell death in ovarian, lung, melanoma and cervical cancer cell lines in vitro, and in melanoma and lung tumors in vivo. We are currently expanding these studies to examine long-term tumor growth/survival and the generation of anti-tumor immunity in C57Bl/6 mice using the TC-1 tumor model, which expresses the HPV oncogenes, E6 and E7. This model allows us to track the T-cell responses generated against the HPV oncogenes, in both primary and metastatic tumor settings. Treatment with IR700-VLP and light exposure induced an influx of CD8+ and CD4+ T-cells into the treated tumors. Ex vivo cultures of whole tumor cell suspensions showed IFN-γ production in PMA/ionomycin-stimulated CD8+ and CD4+ T cells and to a lower extent without stimulation, suggesting that these T-cells may have been primed against the tumor antigens. Our data suggest that local anti-tumor immunity can be induced through the rapid tumor cell death caused by IR700, in conjunction with the ability of HPV VLP to induce an innate immune response.