Antibody-based approaches to modulate immune response

Abstract

In context of an increasing interest in immunotherapeutic treatments, the work described in this thesis expands the current knowledge of several potential antibody-based therapeutic approaches. A new development is the use of bispecific antibodies (BsAb). To introduce BsAb, chapter 2 describes the different platforms currently used to generate IgG-like and non-IgG-like BsAbs, as well as the strategies to gain clinical approval for the different BsAbs. A highly selective binding, as can be achieved with BsAbs, could be beneficial to ‘target’ certain cell populations, such as Tregs, against which current treatments appear to be insufficiently specific. Focusing on BsAb-based therapeutic approaches, in chapter 3 we investigate a novel strategy to optimize a T-cell redirecting bispecific antibody. Two Fab x sdAb-Fc, directed against CD3 and EGFR, with different lengths of the hinge region, were compared. The results show that a shorter hinge design improves BsAb-induced anti-tumor activity, induces more effector cell/target cell clustering and activates T cells more efficiently. In addition, we show (chapter 4) how important it is to select the right isotype antibody. In a mouse tumor model, only IgG2a antibodies were found to exert anti-tumor function, achieving a survival rate of approximately 50%. None of the isotypes tested showed a synergistic effect with adoptive T-cell therapy. An increasing interest in the costimulatory receptor TNFR2 in cancer has prompted us to design, generate and produce novel anti-mTNFR2 antibodies (chapter 5). The characterization and different features of these antibodies are described in this chapter, and they could be used as tools in follow-up studies to further investigate i) the role of TNFR2 in cancer, and ii) how TNFR2 targeting with different antibody candidates that either block or activate this receptor could improve immunotherapy. In chapter 6, two anti-mTNFR2 antibodies were selected for assessment of their application in vitro, ex vivo and in vivo, which revealed their capacity to bind to Tregs but also to CD4+ effector T cells. Taken together, the results presented in this thesis highlight the progress achieved in immunotherapy approaches, with focus on BsAbs and novel strategies to improve cancer treatments. Furthermore, novel anti-mTNFR2 antibodies were developed and featured as useful tools to unravel the role of this receptor in tumor growth.