Optimization of Multivalent Bispecific Antibodies and Immunocytokines with Improved in Vivo Properties

Abstract

Multifunctional antibody-based biologics, such as bispecific antibodies and immunocytokines, can be difficult to produce with sufficient yield and stability, and often exhibit inferior pharmacokinetics. Dock-and-Lock (DNL) is a modular method that combines recombinant engineering with site-specific conjugation, allowing the construction of various complex, yet defined, biostructures with multivalency and multispecificity. The technology platform exploits the natural interaction between two interactive human protein binding domains that are modified to provide covalent fusion. We explored the potential application of a new class of IgG-based DNL modules with an anchor domain fused at the C-terminal end of the kappa light chain (C(k)), instead of the C-terminal end of the Fc. Two C(k)-derived prototypes, an anti-CD22/CD20 bispecific hexavalent antibody, comprising epratuzumab (anti-CD22) and four Fabs of veltuzumab (anti-CD20), and a CD20-targeting immunocytokine, comprising veltuzumab and four molecules of interferon-α2b, were compared to their Fc-derived counterparts. The Ck-based conjugates exhibited superior Fc-effector functions in vitro, as well as improved pharmacokinetics, stability, and anti-lymphoma activity in vivo. These results favor the selection of DNL conjugates with the C(k)-design for future clinical development.