To disrupt Fcγ receptor and complement binding, Wang et al. mutated Fc residues in IgG(L) scFv antibodies bispecific for human CD3 and disialoganglioside GD2 or oncoprotein ErbB2 (HER2) (BsAbs). The Fc mutations did not impact the BsAbs’ pharmacokinetics, stability, antigen binding, or T cell killing in vitro, but did reverse BsAb-induced, myeloid cell-mediated T cell depletion from peripheral blood; lung sequestration; and kidney deposition in mice. Fc mutations enhanced BsAb-induced T cell tumor infiltration and the therapeutic effect on GD2+ or HER2+ tumors in immunocompetent human CD3ε transgenic or immunodeficient mouse models.
Contributed by Paula Hochman
Bispecific antibodies (BsAbs) that engage T cells bind to tumor cells via a tumor-associated antigen and to T cells through surface CD3. BsAbs have promising antitumor properties in vivo. Here we describe the effects of Fc silencing on BsAbs-driven T-cell trafficking to solid tumors. We used BsAbs driven by disialoganglioside GD2 or oncoprotein ErbB2 (HER2) and built on the IgG(L)-scFv platform with or without Fc silencing. We studied the kinetics of T-cell infiltration from blood into solid tumor masses when driven by these BsAbs. We also investigated the therapeutic efficacy of these BsAbs in two mouse models: immunodeficient mice xenografted with patient-derived GD2+ neuroblastoma or HER2+ breast cancer, and human CD3epsilon transgenic mice implanted with a GD2+ murine tumor. BsAbs built with intact Fc domain failed to drive T cells to tumor thereby failing to achieve an antitumor effect in mice. T cells became sequestered in lungs by myeloid cells or depleted in circulation. In contrast, when Fc function was silenced by N297A+/-K322A mutations, T cells were able to infiltrate into subcutaneous solid tumors, a prerequisite for successful therapy outcome.