Martina Schmittnaegel, Eike Hoffmann, Sabine Imhof-Jung, Cornelia Fischer, Georg Drabner, Guy Georges, Christian Klein, Hendrik Knoetgen

Bifunctional antibody fusion proteins engaging effector T cells for targeted elimination of tumor cells via CD3 binding have shown efficacy in both preclinical and clinical studies. Different from such a polyclonal T cell recruitment, an alternative concept is to engage only antigen-specific T cell subsets. Recruitment of specific subsets of T cells may be as potent but potentially lead to fewer side effects. Tumor-targeted peptide-MHC class I complexes (pMHCI-IgGs) bearing known antigenic peptides complexed with MHC class I molecules mark tumor cells as antigenic and utilize the physiological way to interact with and activate T cell receptors. If for example virus-specific CD8+ T cells are addressed, the associated strong antigenicity and tight immune surveillance of the effector cells could lead to efficacious anti-tumor treatment in various tissues. However, peptide-MHC class I fusions are difficult to express recombinantly, especially when fused to entire antibody molecules. Consequently, current formats are largely limited to small antibody fragment fusions expressed in bacteria followed by refolding or chemical conjugation. Here we describe a new molecular format bearing a single pMHCI complex per IgG fusion molecule characterized by enhanced stability and expression yields. This molecular format can be expressed in a full immunoglobulin format and can be designed as mono- or bivalent antibody binders.