ATOR-4066, a bispecific antibody targeting CD40 and CEACAM5, induces strong myeloid and T cell–dependent tumor immunity and synergizes with PD-1 blockade

Despite recent progress within the field of immuno-oncology, immune suppression in the tumor microenvironment, defective antigen presentation, and low levels of tumor-specific T cells are key limitations of current cancer immunotherapies. CD40-targeting immunotherapies hold promises for addressing these limitations across solid tumors. Here, we describe ATOR-4066, a bispecific antibody that targets CD40 and CEACAM5 developed for immunotherapy of cancer using the Neo-X-Prime platform. ATOR-4066 showed potent CEACAM5-dependent activation in vitro with ability to activate intratumoral immune cells from patient derived material. In vivo, ATOR-4066 induced superior anti-tumor activity compared to CD40 mAb in MC38-CEA tumors and cured mice with well-established tumors with a heterogeneous CEACAM5 expression. Using RNA sequencing, flow cytometry and cytokine analysis, we show that ATOR-4066 promotes immune cell trafficking to tumors and activates both myeloid cells and T cells within the tumor microenvironment, with limited immune activation in the periphery. ATOR-4066 initially induces a T cell-independent anti-tumor response, yet a functional T cell response is critical for long-term tumor control and immunity directed to tumor antigens other than CEACAM5. Finally, we demonstrate that ATOR-4066 synergizes with PD-1 blockade in vitro. In conclusion, these data provide mechanistic evidence for the proposed mode of action and support further development of ATOR-4066 in CEACAM5 expressing cancers.