Hong Xu, Ming Cheng, Hongfen Guo, Yuedan Chen, Morgan Huse, Nai-Kong V. Cheung

Anti-disialoganglioside GD2 IgG antibodies have shown clinical efficacy in solid tumors that lack human leukocyte antigens (e.g. neuroblastoma) by relying on Fc-dependent cytotoxicity. However, there are pain side effects secondary to complement activation. T cell retargeting bispecific antibodies (BsAb) also have clinical potential. But it is thus far only effective against liquid tumors. In this study, a fully humanized hu3F8-BsAb was developed, where the anti-CD3 huOKT3 single chain Fv fragment (ScFv) was linked to the carboxyl end of the anti-GD2 hu3F8 IgG1 light chain, and was aglycosylated at N297 of Fc to prevent complement activation and cytokine storm. In vitro, hu3F8-BsAb activated T cells through classic immunological synapses, inducing GD2-specific tumor cytotoxicity at femtomolar EC50 with >10(5) fold selectivity over normal tissues, releasing TH1 cytokines (TNF-α, IFN-γ and IL-2) when GD2(+) tumors were present. In separate murine neuroblastoma and melanoma xenograft models, intravenous hu3F8-BsAb activated T cells in situ and recruited intravenous T cells for tumor ablation, significantly prolonging survival from local recurrence or from metastatic disease. Hu3F8-BsAb, but not control BsAb, drove T cells and monocytes to infiltrate tumor stroma. These monocytes were necessary for sustained T cell proliferation and/or survival and contributed significantly to the anti-tumor effect. The in vitro and in vivo anti-tumor properties of hu3F8-BsAb and its safety profile support its further clinical development as a cancer therapeutic, and provide the rationale for exploring aglycosylated IgG-scFv as a structural platform for retargeting human T cells.