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

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.

In vitro VLA-4 blockade results in an impaired NK cell-mediated immune surveillance against melanoma

Natalizumab (NTZ) is a monoclonal antibody targeting the α4β1 integrin (CD49d/CD29), very late antigen-4 (VLA-4), which is approved for treatment of relapsing-remitting multiple sclerosis (RR-MS). A possible association between NTZ treatment and a higher risk of melanoma is under debate. Natural Killer (NK) cells, which express VLA-4, represent an innate barrier limiting spreading of melanoma under steady state conditions. Indeed, because of their expression of activating receptors, they are very efficient in recognizing and killing melanoma cells without the need of a previous priming. For this reason, we aimed at assessing whether NK-cell functions might be impaired by sustained exposure to NTZ. To investigate this possibility we isolated NK cells from healthy donors and tested their cytotoxic and migratory functions against primary melanoma cells derived from subcutaneous and lymph node metastases. Flow cytometry analysis demonstrated expression of CD49d on both freshly isolated NK cells and activated NK cells. Moreover, VLA-4 and its receptor, vascular cell adhesion protein-1 (VCAM-1) were similarly expressed on freshly isolated NK cells. However, upon a short exposure to NTZ, expression of VLA-4 on NK cells decreased. Analysis of NK receptor expression upon exposure of NK cells from three healthy donors to NTZ indicated that DNAM-1 and NKp46 are apparently decreased, while NKG2A is increased. The degranulation of NK cells towards melanoma cells, which express both VLA-4 and VCAM-1, was not affected when NTZ was added to the co-culture or when both NK cells and melanoma cells were each pre-exposed to NTZ for over 12h. In contrast, degranulation was significantly inhibited after 48h of pre-incubation indicating that NTZ can influence NK-cell degranulation towards melanoma cells only after a prolonged exposure. Using a migration chamber assay, we observed that the migration of NK cells towards melanoma cells was dependent upon the concentration of melanoma cells in the lower chamber, and that it was significantly reduced in presence of NTZ. Our results show that upon exposure to NTZ both cytolytic activity and migration toward melanoma cells were affected, suggesting that binding of NTZ to NK cells affects pathways involved in these NK-cell functions. We analyzed the expression of CD49d on NK cells from MS patients treated with NTZ and observed that it decreases with time of treatment. These data suggest that blockade of VLA-4 on NK-cell surface alters some key functions involved in the immune surveillance toward melanoma by NK cells and may provide a mechanistic explanation for the reported occurrence of melanoma in MS patients treated with NTZ.