DISCOVERY OF A CYNOMOLGUS MONKEY-CROSS-REACTIVE ANTI-HUMAN CD3 MAB FOR T CELL ENGAGERS

Abstract Background Anti-CD3 based T cell engager antibodies can redirect cytotoxic activity of T cells in a non-MHC restricted fashion to kill tumor cells effectively. Therefore, the discovery of an anti-CD3 antibody capable of activating T cells in the presence of tumor cells is highly desirable. Recently, many anti-CD3 bispecific antibodies (bsAbs) entered clinical trials. Despite the promising efficacy of anti-CD3 bsAbs, safety issues arose and establishing a proper therapeutic window between efficacy and safety became a challenge. One of the safety concerns for anti-CD3 bsAbs is the cytokine release syndrome due to T-cell activation. Recent studies have shown that this safety challenge can be mitigated by selecting an anti-CD3 antibody with the appropriate binding epitope, CD3 affinity and binding kinetics (on and off rate). Methods by using WuXi Biologics’ state-of-the-art hybridoma platform, an anti-CD3 Ab was discovered through a combination of immunization and screening strategies. Results the selected anti-CD3 Ab demonstrates moderate affinity and fast-on fast-off binding kinetics against both human and cynomolgus CD3 molecules. Once constructed into T cell engagers (TCEs) using this anti-CD3 Ab with TAA binding arms in WuXiBody® format, the obtained TCEs mediated efficient anti-tumor activity, but induced low levels of cytokine production by T cells. Conclusions WuXi Biologics has discovered an anti-CD3 Ab with desired binding properties to human CD3. As shown in two showcases, the TCEs constructed using this anti-CD3 Ab can elicit efficient T cell cytotoxicity against tumor cells but low levels of cytokine release. The cross-reactivity of the anti-CD3 Ab enables preclinical assessments of toxicity in NHP.