Abstract 6792: Targeting immunosuppressive adenosine to enhance vaccinia virus renal cancer oncolysis in vivo
Authors: Chavez Valery A. , Bustamante Floritza , Merchan-Mendes Carolina , Saigh Shannon , Guevara Patricia , Wieder Eric , Merchan Jaime 
Published: April 2023

Background: The oncolytic vaccinia virus (VV) is a promising biotherapy undergoing clinical development in human cancer, including renal cell carcinoma (RCC). While VV induces potent tumor oncolysis and immunomodulation, clinical experience has shown that OV therapy alone leads to limited benefit. Moreover, OVs and checkpoint inhibitor combinations, do not significantly improve clinical responses, underscoring the need to identify new tumor microenvironment targets to overcome OV resistance in vivo. The adenosine pathway is a biologically and clinically relevant target in RCC and is associated with adaptive resistance to immunotherapy. The objectives of this study are to characterize the role of the adenosine axis in tumor escape mechanisms to vaccinia virus in RCC, and to determine the efficacy of novel OV-immunotherapy combinations targeting adenosine.

Methods: The in vitro oncolytic effects of JX-594 and mJX-594 (oncolytic VVs expressing human or murine GMCSF, respectively) in human (786-0, ACHN, CAKi-1, UOK262) and murine (RENCA) renal cancer cell lines were assessed. Proteomic analysis of 786-0 lysates treated with JX-594 was performed for mechanistic studies. The effects of JX-594 and mJX 594 on CD73 and CD39 expression were determined in human and murine RCC. In vivo antitumor effects of mJX-594 alone, and in combination with A2AR, A2BR and Dual Adenosine receptor inhibition was determined in the RENCA model in immunocompetent mice.

Results: Potent in vitro oncolysis and efficient viral replication were observed in human and murine RCC cells after infection with vaccinia virus. VV oncolysis was associated with significant modulation of proliferation, survival, and ER stress pathways, as determined by functional proteomics. JX-594 and mJX-594 treatment induced increased expression of CD39 and CD73 in RCC cell lines and in renal tumors in vivo. While no significant enhancement of vaccinia oncolysis was observed with combinations with A2AR and A2BR inhibitors in vitro, a significant improvement on in vivo tumor control and survival were observed when mJX594 given intravenously was combined with A2AR and A2BR inhibitors (triplet), at a higher degree than single agents or doublets (mJX-594 in combination with single A2AR or A2BR inhibitors). Characterization of treatment mediated changes in immune signatures (nanostring) is underway and will be presented at the meeting.

Conclusion: Vaccinia virus potently induces in vitro oncolysis in RCC cell lines, while also increasing expression of adenosine rate limiting enzymes in vitro and in vivo, which could explain tumor escape to oncolytic VV. MJX-594 combination with A2AR and A2BR inhibition safely and significantly improves renal cancer oncolysis and tumor control in vivo. Our studies uncover a novel, translationally relevant strategy to improve OV efficacy in vivo, in RCC and other cancers.

Citation Format: Valery A. Chavez, Floritza Bustamante, Carolina Merchan-Mendes, Shannon Saigh, Patricia Guevara, Eric Wieder, Jaime Merchan. Targeting immunosuppressive adenosine to enhance vaccinia virus renal cancer oncolysis in vivo [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 6792.