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 promise for addressing these limitations across solid tumors. In this study, we describe ATOR-4066, a bispecific antibody that targets CD40 and CEACAM5, developed using the Neo-X-Prime platform. ATOR-4066 showed potent CEACAM5-dependent activation in vitro, with an ability to activate intratumoral immune cells from patient-derived material. In vivo, ATOR-4066 induced superior antitumor activity compared with a CD40 mAb in MC38-carcinoembryonic antigen tumors and cured mice with well-established tumors with heterogeneous CEACAM5 expression. Using RNA sequencing, flow cytometry, and cytokine analysis, we showed that ATOR-4066 promoted immune cell trafficking to tumors and activated both myeloid cells and T cells within the tumor microenvironment, with limited immune activation in the periphery. ATOR-4066 initially induced a T cell-independent antitumor response, yet we found that a functional T-cell response was critical for long-term tumor control and immunity directed to tumor antigens other than CEACAM5. Finally, we demonstrated that ATOR-4066 synergized 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.