Yu et al. showed that 341G2 (bleselumab) binds to both CRD1 and CRD2 domains in hCD40, overlapping the surface binding hCD40L, and that 341G2 hIgG1 and hIgG4 Fc-variants inhibited immune activity. However, hIgG2 Fc-variants, which had minimal FcγR binding, potently agonized CD40 clustering, stimulated in vitro and in vivo immune activity (but induced cytokine only transiently), activated DCs, and synergized with cell therapy and peptide vaccination to control s.c. solid tumors in mouse models. FcγR-independent conversion to agonism depended on hIgG2 hinge’s unique disulfide bonding and was applicable to other antagonistic hCD40 antibodies.
Contributed by Paula Hochman
ABSTRACT: Anti-CD40 monoclonal antibodies (mAbs) comprise agonists and antagonists, which display promising therapeutic activities in cancer and autoimmunity, respectively. We previously showed that epitope and isotype interact to deliver optimal agonistic anti-CD40 mAbs. The impact of Fc engineering on antagonists, however, remains largely unexplored. Here, we show that clinically relevant antagonists used for treating autoimmune conditions can be converted into potent FcgammaR-independent agonists with remarkable antitumor activity by isotype switching to hIgG2. One antagonist is converted to a super-agonist with greater potency than previously reported highly agonistic anti-CD40 mAbs. Such conversion is dependent on the unique disulfide bonding properties of the hIgG2 hinge. This investigation highlights the transformative capacity of the hIgG2 isotype for converting antagonists to agonists to treat cancer.