Abstract 4223: Cis-activation of PD-1+ effector T cells with dual-targeting immunocytokines generated using a novel chemical conjugation platform

Abstract

Abstract Immunocytokines (IC) provide the opportunity for targeted delivery of cytokines as payloads to tissues and cells to improve safety and efficacy of cytokine-based therapies. ICs have gained significant interest in recent years and several antibody-cytokine fusion proteins have entered clinical trials. Compared to recombinant fusion proteins, we have developed an entirely different approach to IC generation based on the site-specific, chemical conjugation of synthetic cytokines to antibodies. Bright Peak generates enhanced and conjugatable cytokines using a novel protein engineering platform based on solid-phase peptide synthesis and subsequent chemical ligation of protein segments. Our synthetic cytokines can then be readily chemically conjugated to specific lysine residues in the Fc region of an existing IgG1, IgG2 or IgG4 antibody without the need for prior antibody engineering. Chemical conjugation of cytokine payloads is rapid, enabling the flexible generation of ICs based on different antibodies and payloads within weeks. We applied our technology to more than 10 antibodies and found that neither antigen binding nor payload potency and selectivity are affected by chemical conjugation. Importantly, binding of the Fc domain of ICs to Fc gamma receptors or FcRn is not significantly affected. We are initially focusing on the development of PD-1-targeted ICs to achieve dual-targeting of PD-1+ effector T cells (cis-signaling). Using several anti-PD-1 antibodies and various synthetic IL-2 variants as payloads, we created ICs with different drug-antibody ratios and explored alternative conjugation sites within the Fc region. Resulting PD-1/IL-2 ICs are highly active showing significantly enhanced potency due to avidity resulting from binding of the cytokine to PD-1+ effector T cells in cis. Our PD-1/IL-2 ICs induce strong pharmacodynamic effects in vivo, and we are currently optimizing the pharmacological profiles of PD-1-targeted ICs for clinical application. In addition, we are actively exploring cis-signaling ICs targeting different surface receptors and immune cells. Citation Format: Jean-Philippe Carralot, Matilde Arévalo Ruiz, Robert Tam, Eric Armentani, Vijaya R. Pattabiraman, Bertolt Kreft. Cis-activation of PD-1+ effector T cells with dual-targeting immunocytokines generated using a novel chemical conjugation platform [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 4223.