Abstract 4039: Enhanced anti-cancer efficacy of the AhR Inhibitor DA-4505 in combination with anti-PD-1 treatment: Attenuation of lung metastasis and elimination of tumor

Abstract Background: The Aryl hydrocarbon receptor (AhR) is one of the most predominant regulators of cancer metabolism. AhR plays a crucial role in inhibiting the activation of immune cells and promoting the growth of tumor cells. Here, we propose that a best-in-class AhR inhibitor, DA-4505, improves anti-tumor efficacy in combination with anti-PD-1. Methods: To explore the anti-tumor effects, DA-4505 was administered at a daily dose of 10 mg/kg either alone or in combination with anti-PD-1 (10 mg/kg) in a syngeneic mouse model. Tumor volume, survival rates, and metastasis were measured, and immune profiles were evaluated using mIHC, flow cytometry, and scRNAseq. Results: The synergistic anti-tumor effects of the DA-4505 and aPD-1 combination therapy were observed across four mouse tumor models (CT26, 4T1, LLC, TC1). The combination group demonstrated a significant improvement in anti-tumor efficacy compared to the monotherapy groups. Despite the moderate response of aPD-1 in the CT26 colon tumor model, the combination group displayed heightened anti-tumor effects through increase in CD8 T cell activity (P<0.05). In the LLC and TC1 lung cancer models, the combination therapy demonstrated improved anti-tumor effects and survival rates (P<0.001). Notably, the LLC model exhibited a significant increase in M1-type macrophages, while the TC1 model showed a significant augmentation in functional markers of CD3+ T cells within the combination group (P<0.05). In both models, there was a significant reduction in the ratio of immunosuppressive M-MDSC and PMN-MDSC in the combination group. Immune depletion assays elucidated that DA-4505 mediated anti-tumor effects by increase in CD8+ T cells, NK cells, and macrophages in the CT26 model. In contrast, the LLC model exhibited the contribution of macrophages and CD4+ T cells to anti-tumor effects in the combination group (P<0.05). To assess the impact on metastasis inhibition, an orthotopic model of 4T1 mouse tumor was established, revealing a significantly increased anti-tumor effects and survival rate in the combination group, accompanied by a reduced lung metastasis ratio. H&E staining confirmed diminished migration of tumor tissue to adjacent areas. scRNAseq analysis of CT26 tumor samples indicated consistent changes at the gene expression level, reflecting a decrease in metastasis-related MMP and VEGF genes in the combination group and an increasing trend in cytotoxicity-related genes following DA-4505 treatment. Conclusion: The AhR inhibitor, DA-4505, has demonstrated enhanced anti-tumor efficacy when administered in combination with anti-PD-1. Furthermore, it not only promoted tumor elimination but also demonstrated significant efficacy in inhibiting metastasis. This study highlights the potential of combining AhR inhibitors with immunotherapies for clinical treatment. Citation Format: Dong Kwon Kim, Sujeong Baek, Seung Min Yang, Young Taek Kim, Joon Yeon Hwang, Seul Lee, Seong-san Kang, Mi hyun Kim, Heekyung Han, Kwangmin Na, Chai Young Lee, Yu Jin Han, Taedong Han, Hyounmie Doh, Jongho Cho, Dajeong Kim, Daewon Cha, Jae Hwan Kim, Youngseon Byeon, Young Seob Kim, Mi Ran Yun, Jii Bum Lee, Min Hee Hong, Sun Min Lim, Kyoung-Ho Pyo, Byoung Chul Cho. Enhanced anti-cancer efficacy of the AhR Inhibitor DA-4505 in combination with anti-PD-1 treatment: Attenuation of lung metastasis and elimination of tumor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4039.