Functional, Biophysical, and Structural Characterization of Human IgG1 and IgG4 Fc Variants with Ablated Immune Functionality.

ABSTRACT: Engineering of fragment crystallizable (Fc) domains of therapeutic immunoglobulin (IgG) antibodies to eliminate their immune effector functions while retaining other Fc characteristics has numerous applications, including blocking antigens on Fc gamma (Fc?) receptor-expressing immune cells. We previously reported on a human IgG2 variant termed IgG2? with barely detectable activity in antibody-dependent cellular cytotoxicity, phagocytosis, complement activity, and Fc? receptor binding assays. Here, we extend that work to IgG1 and IgG4 antibodies, alternative subtypes which may offer advantages over IgG2 antibodies. In several in vitro and in vivo assays, the IgG1? and IgG4? variants showed equal or even lower Fc-related activities than the corresponding IgG2? variant. In particular, IgG1? and IgG4? variants demonstrate complete lack of effector function as measured by antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, antibody-dependent cellular phagocytosis, and in vivo T-cell activation. The IgG1? and IgG4? variants showed acceptable solubility and stability, and typical human IgG1 pharmacokinetic profiles in human FcRn-transgenic mice and cynomolgus monkeys. In silico T-cell epitope analyses predict a lack of immunogenicity in humans. Finally, crystal structures and simulations of the IgG1? and IgG4? Fc domains can explain the lack of Fc-mediated immune functions. These variants show promise for use in those therapeutic antibodies and Fc fusions for which the Fc domain should be immunologically "silent".

SUBMITTER: Tam SH 

PROVIDER: S-EPMC6698826 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature