Generation of IL-2-Fc-antibody conjugates by click chemistry.

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Immunocytokines (ICKs) are antibody directed cytokines produced by genetic fusion of an antibody to a cytokine. We now show that antibodies conjugated by click chemistry to interleukin-2 (IL-2)-Fc form fully active conjugates, and in one example, equivalent activity to a genetically produced ICK. An IL-2-Fc fusion protein was optimized for click chemistry at hinge cysteines using protein stabilizing IL-2 mutations at Lys35 and Cys125 and Fc hinge mutations at Cys142 and Cys148. The IL-2-Fc fusion protein with K35E and C125S mutations with 3 intact hinge cysteines, designated as IL-2-Fc Par, was selected based on its minimal tendency to aggregate. IL-2-Fc-antibody clicked conjugates retained high IL-2 activity and bound target antigens comparable to parent antibodies. An IL-2-Fc-anti-CEA click conjugate showed comparable anti-tumor activity to an anti-CEA-IL-2 ICK in immunocompetent CEA transgenic mice bearing CEA positive orthotopic breast tumors. Significant increases in IFNγ+ /CD8+ and decreases in FoxP3+ /CD4+ T-cells were found for the clicked conjugate and ICK therapies, suggesting a common mechanism of tumor reduction. The production of antibody targeted IL-2 therapy via a click chemistry approach is feasible with comparable activity to genetically produced ICKs with the added advantage of multiplexing with other monoclonal antibodies.