Abstract 5117: Combined treatment with the epigenetic drug CM272 and an anti-BCL-XL proapoptotic drug sensitizes solid tumors to immune checkpoint blockade (2023)

Abstract Epigenetic modulators in combination with proapoptotic drugs have become a standard of treatment for acute myeloid leukemia. However, the clinical efficacy of these combinations in solid tumors has shown to be negligible. Our group has demonstrated that the epigenetic drug CM272, which targets DNMT and G9a, induces synergistic responses in combination with proapoptotic drugs in hematological malignancies (Cancer Discovery 2021). We have also reported that CM272 induces an immunogenic cell death that sensitizes tumor cells to immune checkpoint blockade (ICB) (Nature Medicine 2020). Here, we hypothesized that CM272 in combination with proapoptotic drugs may sensitize tumor cells to ICB, resulting in profound anti-tumor responses. To test this hypothesis, we evaluated in vitro the sensitivity of cancer cells to different combinations of epigenetic and proapoptotic drugs. The most efficient combination was tested in various immunocompetent mouse models, followed by an immunophenotypic characterization of the tumor microenvironment. We found that CM272 in combination with inhibitors of BCL-XL, BCL2 or MCL1, yielded synergistic in vitro responses in a large collection of human and mouse cell lines derived from solid tumors. Mechanistically, the treatments induced the expression of endogenous retroelements/retroviruses, which led to the activation of RIG-1 and MDA5 viral sensors, ATP hydrolysis and tumor cell death. Remarkably, we found that CM272 in combination with BCL-XL inhibition had more potent anti-tumor effects than that found with BCL2 or MCL1 inhibitors. In vivo, the triple combination CM272, A1331852 (BCL-XL inhibitor) and an anti-PD-1 moAb significantly reduced tumor growth and increased overall survival in three subcutaneous lung cancer models (LLC, 393P, Lacun-3) in comparison to double treatments. Moreover, this triple combination also induced significant anti-tumor responses in subcutaneous mouse models of colon cancer (MC38) and melanoma (B16), as well as in orthotopic models of lung cancer (LLC), glioblastoma (CT-2A) and breast cancer (ANV5), leading to prolonged survival and cure in a fraction of animals. The triple therapy was associated with a significant increase in the ratio of CD8 T versus immunosuppressive Treg cells, and M1 versus M2 macrophages. In conclusion, we report a novel regimen combining a dual epigenetic inhibitor, an anti-BCL-XL, and an anti-PD-1 moAb that results in potent responses in multiple pre-clinical models of solid tumors. The mechanisms underneath the antitumor responses include the modulation of the energy metabolism in tumor cells, leading to cell death boosted by an anti-BCL-XL pro-apoptotic drug, along with fostering the immune system to generate an efficient anti-tumor response assisted by ICB. This study reveals the potential of epigenetic therapeutics to treat and cure patients with solid tumors. Citation Format: Yaiza Senent, Vicente Fresquet, Victoria Jimenez, Karmele Valencia, Ana Remirez, Francisco Exposito, Marisol Gonzalez-Huarriz, Borja Ruiz-Fernandez de Cordoba, Haritz Moreno, Daniel Ajona, Marta M Alonso, Fernando Lecanda, Antonio Pineda-Lucena, Felipe Prosper, Alfonso Calvo, Jose Angel Martinez-Climent, Ruben Pio. Combined treatment with the epigenetic drug CM272 and an anti-BCL-XL proapoptotic drug sensitizes solid tumors to immune checkpoint blockade. [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 5117.