Fc glycoengineering of a PD-L1 antibody harnesses Fcγ receptors for increased antitumor efficacy.

FDA-approved anti-PD-L1 monoclonal antibodies (mAbs) bear the IgG1 isotype, whose scaffolds are either wild-type (e.g., avelumab) or Fc-mutated and lacking Fcγ receptor (FcγR) engagement (e.g., atezolizumab). It is unknown whether variation in the ability of the IgG1 Fc region to engage FcγRs renders mAbs with superior therapeutic activity. In this study, we used humanized FcγR mice to study the contribution of FcγR signaling to the antitumor activity of human anti-PD-L1 mAbs and to identify an optimal human IgG scaffold for PD-L1 mAbs. We observed similar antitumor efficacy and comparable tumor immune responses in mice treated with anti-PD-L1 mAbs with wild-type and Fc-mutated IgG scaffolds. However, in vivo antitumor activity of the wild-type anti-PD-L1 mAb avelumab was enhanced by combination treatment with an FcγRIIB-blocking antibody, which was co-administered to overcome the suppressor function of FcγRIIB in the tumor microenvironment (TME). We performed Fc glycoengineering to remove the fucose subunit from the Fc-attached glycan of avelumab to enhance its binding to the activating FcγRIIIA. Treatment with the Fc-afucosylated version of avelumab also enhanced antitumor activity and induced stronger antitumor immune responses compared with the parental IgG. The enhanced effect by afucosylated PD-L1 antibody was dependent on neutrophils and associated with decreased frequencies of PD-L1+ myeloid cells and increased infiltration of T cells in the TME. Our data reveal that the current design of FDA-approved anti-PD-L1 mAbs does not optimally harness FcγR pathways and suggest two strategies to enhance FcγR engagement to optimize anti-PD-L1 immunotherapy.

Bispecific antibodies increase the therapeutic window of CD40 agonists through selective dendritic cell targeting.

Therapeutic use of agonistic anti-CD40 antibodies is a potentially powerful approach for activation of the immune response to eradicate tumors. However, the translation of this approach to clinical practice has been substantially restricted due to the severe dose-limiting toxicities observed in multiple clinical trials. Here, we demonstrate that conventional type 1 dendritic cells are essential for triggering antitumor immunity but not the toxicity of CD40 agonists, while macrophages, platelets and monocytes lead to toxic events. Therefore, we designed bispecific antibodies that target CD40 activation preferentially to dendritic cells, by coupling the CD40 agonist arm with CD11c-, DEC-205- or CLEC9A-targeting arms. These bispecific reagents demonstrate a superior safety profile compared to their parental CD40 monospecific antibody while triggering potent antitumor activity. We suggest such cell-selective bispecific agonistic antibodies as a drug platform to bypass the dose-limiting toxicities of anti-CD40, and of additional types of agonistic antibodies used for cancer immunotherapy.