Abstract 6295: Belzupacap sarotalocan, an investigational virus-like drug conjugate, preferentially binds cancer cell glycosaminoglycans associated with the epithelial to mesenchymal transition
Authors: Fons Nathan R. , Kines Rhonda C. , Schiller John T. 
Published: June 2023

Abstract
Human papillomaviruses (HPVs) are non-enveloped, double-stranded DNA viruses that utilize modified glycosaminogycans (GAGs) such as heparan sulfate proteoglycans, within the epidermal basement membrane as initial attachment factors prior to cell entry and infection. Similarly modified GAGs are also commonly found on the surface of tumor cells, enabling HPV capsids with tumor-selective binding properties. Belzupacap sarotalocan (bel-sar, formerly AU-011), is a virus-like drug conjugate composed of an HPV virus-like particle (VLP) conjugated to a cytotoxic payload (phthalocyanine dye) which upon light activation, causes rapid immunogenic tumor necrosis of bound tumor cells in vivo and has the potential to induce long-term anti-tumor immunity. Bel-sar has been shown to bind to and kill a wide variety of tumor types in preclinical models and is entering a Phase 3 clinical trial for the treatment of early-stage choroidal melanoma. To investigate the precise GAG modifications as well as the overall genetic signature which mediates the binding specificity of bel-sar, a large, multi-tumor type binding screen of bel-sar on 124 cancer cell lines was performed in vitro, where we identified a strong relationship between drug binding and pathways involved in the epithelial to mesenchymal transition (EMT). Additionally, through dose escalation treatments, HeLa subclones were generated which fail to bind and are resistant to the cytotoxic effects of bel-sar. Gene expression profiling and biochemical characterization of these resistant HeLa cell lines demonstrated a strong reduction in the expression of GAGs and a marked down-regulation of TGF-β signaling, ultimately resulting in the induction of a mesenchymal to epithelial transition (MET). Furthermore, gene-gene correlation studies showed that a variety of GAG biosynthesis genes are associated with TGF-β signaling and EMT progression, and that these genes are important determinates of bel-sar binding. Overall, these data suggest that the binding of bel-sar and HPV VLPs is strongly dependent on the expression and modification of GAGs that occurs during the EMT process. As many cancers, especially metastatic tumors, are thought to undergo at least partial EMT, these data provide mechanistic insights into the tumor-targeting ability of HPV VLP-conjugates such as bel-sar and suggest possible applications for such therapies across a wide variety of other tumor types.
Citation Format: Nathan R. Fons, Rhonda C. Kines, John T. Schiller. Belzupacap sarotalocan, an investigational virus-like drug conjugate, preferentially binds cancer cell glycosaminoglycans associated with the epithelial to mesenchymal transition [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 6295.