Evaluation of THEO-260 as a novel oncolytic virus therapy for treating stromal rich tumours.

Abstract

e14573 Background: Stromal rich tumours pose a significant challenge to the effectiveness of systemic anticancer therapies, including immunotherapies and oncolytic viruses. This is due to the abundance of cancer associated fibroblasts (CAFs) that suppress immune cells and limit drug penetration. THEO-260 is a potent, mechanistically novel oncolytic virus therapy intrinsically capable of lysing both cancer cells and CAFs, and is currently in development for late stage relapsed refractory ovarian cancer. Methods: The efficacy and safety of THEO-260 was assessed in multicellular spheroids, in patient-derived ex vivo fresh ovarian samples and in mouse models of human stromal tumours. Results: Unpassaged ascites and tumour samples collected from cytoreductive surgeries for advanced ovarian cancer (n=24 independent patients) were treated with a clinically-relevant dose of THEO-260. THEO-260 effectively killed the cancer cell (EpCAM+ EGFR+PDL1+ CA125+) and CAF (FAP+) populations, being efficacious in treatment-naive and platinum-resistant patient samples. Importantly, the T cell population in these patients, in addition to primary normal fibroblasts (including intestinal, pulmonary, dermal, cardiac, uterine fibroblasts) from healthy donors, were not damaged. Ex vivo studies show THEO-260 stimulates effector T cell responses upon tumour lysis as indicated by IFNγ release. Demonstrating suitability as an IV delivered agent, THEO-260 was active in pooled human serum and whole human blood (n = 10 donors). THEO-260 excels in low nutrient, low proliferative environments, typical of human solid tumours and has been developed with a view to persist in the tumour microenvironment without the need for repeated cycles of delivery. THEO-260 is well tolerated in vivo following a clinically relevant intravenous dosing regimen. In PARP inhibitor and platinum resistant ovarian cancer murine models containing human CAFs and cancer cells, THEO-260 shows antitumor efficacy, with a complete reduction in tumour volume in subcutaneous and intraperitoneal systems, and superiority to SOC. Virus activity is not restricted to ovarian cancer, with cell line data demonstrating killing in additional solid tumour types, including pancreatic, colorectal, lung, and breast cancer. THEO-260 exhibits genetic and temperature based stability, and GMP manufacturing to high yields is underway. Conclusions: Taken together, we present a preclinical data package for THEO-260 supporting progression to Phase I clinical trials.