Fcγ Receptor Dependency of Agonistic CD40 Antibody in Lymphoma Therapy Can Be Overcome through Antibody Multimerization

Immunomodulatory mAbs, led by the anti-CTLA4 mAb ipilimumab, are an exciting new class of drugs capable of promoting anticancer immunity and providing durable control of some tumors. Close analysis of a number of agents has revealed a critical yet variable role for Fc gamma receptors in their efficacy. In this article, we reveal that agonistic anti-CD40 mAbs have an absolute requirement for cross-linking by inhibitory Fc gamma RIIB when used systemically to treat established BCL1 syngeneic lymphoma, and therapy is lost when using a mouse IgG2a mAb not cross-linked by Fc gamma RIIB. Furthermore, in Fc gamma RIIB-deficient mice the lymphoma itself can provide Fc gamma RIIB to cross-link anti-CD40 on neighboring cells, and only when this is blocked does therapy fail. The dependence on Fc gamma RIIB for immunostimulatory activity was not absolute, however, because when anti-CD40 mAbs were administered systemically with the TLR3 agonist polyinosinic: polycytidylic acid or were given subcutaneously, activatory Fc gamma R could also provide cross-linking. Using this mechanistic insight, we designed multimeric forms of anti-CD40 mAb with intrinsic Fc gamma R-independent activity that were highly effective in the treatment of lymphoma-bearing mice. In conclusion, Fc gamma R-independent anti-CD40 activation is a viable strategy in vivo. These findings have important translational implications, as humans, unlike mice, do not have IgG that binds strongly to Fc gamma RIIB; therefore Fc gamma R-independent derivatives represent an attractive therapeutic option.