Abstract 964: Induction of immunogenic cell death and interferon signaling by carboplatin and the ATR inhibitor M6620 may contribute to anti-tumor activity of M6620-carboplatin-avelumab triplet combination in MC38 tumor model
Authors: Alimzhanov Marat , George Ashwin , Shah Parantu , Zimmerman Astrid , Schroeder Andreas , Falk Martin , Amendt Christiane , Halle Joern-Peter , Blaukat Andree , Zenke Frank , Soulard Patricia 
Published: September 2020

Abstract
Ataxia-telangiectasia mutated and Rad3-related kinase (ATR) is one of the key players in the DNA damage response (DDR) to replication stress. M6620 is a potent and selective ATR inhibitor which has been shown to sensitize cancer cells to the lethal effects of DNA-damaging chemotherapeutic agents. We previously demonstrated that M6620 significantly enhances the anti-tumor efficacy of dual combinations of platinum-based chemotherapy and avelumab, an FDA-approved anti-PD-L1 monoclonal antibody, in syngeneic tumor models in vivo. The purpose of this study was to further elucidate the potential mechanisms of action that drive the therapeutic benefit of this triplet combination therapy.
Treatment with certain chemotherapeutic agents has been reported to promote immunogenic cell death (ICD) in tumor cells. We utilized in vitro assays to test the expression of markers of immunogenic cell death in murine MC38 colorectal carcinoma cells. After 72 hours of treatment, carboplatin and M6620 dual combination treatment significantly increased the levels of Calreticulin, HMGB1, and ATP relative to treatment with either single agent. In addition, gene expression profiling was used to determine pathways differentially induced by the drug treatments. RNA-sequencing (RNA-seq) analysis was performed on MC38 cells treated in vitro with carboplatin, M6620, or dual combination therapy. Comparison of gene expression between treatment groups at 48 hours post-treatment revealed that the dual combination therapy significantly increased expression of genes regulated by type I/II interferons (IFN), including CCl5, CXCL10, CXCL11 and ISG15. RNA-seq gene expression analysis was also performed on MC38 tumor samples from mice treated with carboplatin, M6620, avelumab, carboplatin/avelumab dual therapy, or carboplatin/M6620/avelumab triple combination therapy. Triple combination therapy induced a more robust upregulation of IFN-inducible genes at day 3 compared with monotherapies or carboplatin/avelumab dual combination, consistent with in vitro observations that M6620 and carboplatin dual combination therapy enhanced expression of genes regulated by IFNs.
Taken together, these data suggest that potentiation of immunogenic cell death and induction of pro-inflammatory responses by M6620, in the context of chemotherapy-induced DNA damage, may contribute to the enhanced anti-tumor efficacy observed with carboplatin, M6620, and avelumab triple combination therapy.
Citation Format: Marat Alimzhanov, Ashwin George, Parantu Shah, Astrid Zimmerman, Andreas Schroeder, Martin Falk, Christiane Amendt, Joern-Peter Halle, Andree Blaukat, Frank Zenke, Patricia Soulard. Induction of immunogenic cell death and interferon signaling by carboplatin and the ATR inhibitor M6620 may contribute to anti-tumor activity of M6620-carboplatin-avelumab triplet combination in MC38 tumor model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 964.