Abstract A169: Overcoming tumor-associated immune suppression and resistance to cancer immunotherapy using Hyal2-ADCC
Authors: Kusmartsev Sergei , Donelan William , Brisbane Wayne , Nguyen Brianna , Hsieh Meng-Lun , Li Shiwu , Dominguez-Gutierrez Paul , O'Malley Padraic , Crispen Paul L 
Published: December 2023

Abstract
Background: Multiple clinical studies have addressed the role of immunotherapies for solid cancers. While these studies have demonstrated promising results and improvements over existing therapies, less than half of patients with advanced disease show the clinical benefits of immunotherapy. Furthermore, once tumors start to produce metastases, it becomes one of the leading causes of cancer-related mortality. Hyal2-ADC is a novel conjugate of anti-Hyal2 monoclonal antibody and cytotoxic payload PNU. Hyaluronidase 2 (Hyal2), which is a membrane-bound enzyme expressed by both MDSCs and epithelial tumor cells, serves as a molecular target for the Hyal2-ADC. Importantly, our anti-Hyal2 antibodies recognize both human and mouse Hyal2.
Methods: Expression of Hyal2 in human and mouse cancer tissues was assessed using immunohistochemistry and Western Blotting. The in vitro effects of Hyal2-ADC tumor cells and MDSCs were evaluated using MTT assay and immunofluorescence. A single-cell RNA sequencing was utilized for the transcriptomic analysis of Hyal2-expressing myeloid cells. The in vivo anti-tumor activity of Hyal2-ADC was evaluated using syngeneic mouse tumor models and human xenograft tumor models in immunodeficient mice. Mice with established bladder or prostate tumors were used in this study.
Results: Administration of Hyal-ADC alone led to the inhibition of tumor growth in a dose-dependent manner. Importantly, the therapeutic effect of Hyal2-ADC was associated with remodeling the tumor microenvironment, reduction of immunosuppressive myeloid cells, and influx of immune T cells. A combination of Hyal2-ADC with anti-PD1 therapy resulted in complete tumor eradication in mice with syngeneic established tumors (initial volume &lt;200 mm3) in 100% treated mice. The cured mice demonstrated long-term protection from tumor re-challenge. Furthermore, the combination therapy of mice with large, advanced established tumors (&gt;200mm3) resulted in 80% tumor eradication.
Conclusions: Hyal2-ADC is a first-in-class drug that selectively targets Hyal2-expressing cells. The modulation of the immunosuppressive tumor microenvironment and development of efficient immune memory observed in murine models suggests that Hyal2-ADC alone or in combination with anti-PD1 therapy could be utilized for the treatment of solid tumors associated with deregulated HA metabolism, including bladder, prostate, breast, brain, and other cancers. Mechanistically, the enzyme Hyal2 is involved in the degradation of tumor-associated hyaluronan (HA), one of the major components of the extracellular matrix in tumor stroma. Depletion of Hyal2-expressing cells leads to normalization of HA metabolism in the tumor microenvironment supporting generation of T cell-mediated anti-tumor immune response. Overall, this study introduces a novel concept to remodeling the tumor microenvironment, bypassing tumor-associated immune suppression, and overcoming resistance to cancer immunotherapy, thus representing a novel therapeutic strategy for patients.
Citation Format: Sergei Kusmartsev, William Donelan, Wayne Brisbane, Brianna Nguyen, Meng-Lun Hsieh, Shiwu Li, Paul Dominguez-Gutierrez, Padraic O'Malley, Paul L Crispen. Overcoming tumor-associated immune suppression and resistance to cancer immunotherapy using Hyal2-ADCC [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A169.