Abstract 4155: Mitazalimab, a potent CD40 agonist in combination with chemotherapy redirects and activates tumor infiltrating myeloid cells
Authors: Smith Karin Enell , Thagesson Mia , Nilsson Anneli , Werchau Doreen , Ellmark Peter 
Published: June 2022

Abstract
Mitazalimab is a human CD40 agonistic antibody developed for immunotherapy of cancer. Activation of CD40, expressed on myeloid cells, such as dendritic cells and tumor infiltrating macrophages, leads to improved T cell priming and initiation of T cell-dependent anti-tumor responses. Mitazalimab is a FcγR crosslinking-dependent IgG1 antibody, with potential for high efficacy and manageable safety profile.
Immunologically cold and immune-excluded tumors, such as pancreatic cancer, are defined by low infiltration of immune cells as well as low expression and release of neoantigens. In pancreatic cancer, effector CD8+ T cells are excluded from the tumor by the desmoplastic tumor stroma, which surrounds the tumor and hosts immunosuppressive macrophages that dampen the immune response in the tumor microenvironment. By activating and re-directing tumor infiltrating myeloid cells, CD40 agonists such as mitazalimab, have the potential to augment the response to chemotherapy and spark an effective anti-tumor response by i) priming T cells reactive to the tumor neoantigens released by the chemotherapy, and ii) inducing degradation of the stroma surrounding the tumor thereby enhancing the efficacy of chemotherapy.
The ability of mitazalimab to augment the response to chemotherapy was demonstrated in mice, transgenic for human CD40 (hCD40tg), inoculated with the syngeneic tumor cell line MB49. Mitazalimab, administered repeatedly together with FOLFIRINOX (oxaliplatin, irinotecan, 5-fluorouracil and folinic acid), synergized effectively with chemotherapy, inducing long-term survival. The combined treatment improved activation of antigen presenting cells in the circulation, intratumoral T cell responses as well as reduced the amount of intratumoral immunosuppressive M2 macrophages. By converting the MB49 tumor cell line resistant to FOLFIRINOX treatment, we could further demonstrate that the combination of mitazalimab and FOLFIRINOX induced a strong anti-tumor activity also in a chemoresistant variant of the MB49 cell line.
In conclusion, mitazalimab synergizes effectively with chemotherapy, leading to induction of long-term survival in a preclinical tumor model by reducing immunosuppressive M2 macrophages and improving T cell responses intratumorally. These preclinical data, together with the clinical data of mitazalimab from the phase 1 study (NCT02829099), where mitazalimab was well tolerated up to 1200 μg/kg with a manageable safety profile, support the ongoing clinical phase 2 study OPTIMIZE-1 (NCT04888312) of mitazalimab in combination with chemotherapy in pancreatic cancer.
Citation Format: Karin Enell Smith, Mia Thagesson, Anneli Nilsson, Doreen Werchau, Peter Ellmark. Mitazalimab, a potent CD40 agonist in combination with chemotherapy redirects and activates tumor infiltrating myeloid cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4155.