Generation of IL‐2‐Fc‐antibody conjugates by click chemistry

Abstract

AbstractBackgroundImmunocytokines (ICKs) are antibody directed cytokines produced by genetic fusion of an antibody to a cytokine.MethodsWe 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.ResultsAn 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.ConclusionThe 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.