Provided herein are methods and compositions related to the
in vivo testing of therapeutic agents comprising a human Fc in genetically modified rodents (e.g., the testing of the pharmacokinetic and / orpharmacodynamic properties of such a therapeutic agent in genetically modified rodents). In some embodiments the genetically modified rodents express antibodies comprising a human Fc (e.g., a human IgG1 Fc, a human IgG4 Fc). In some embodiments, the rodents express fully human antibodies (i.e., antibodies having human heavy chains and human light (gamma or kappa) chains). In certain embodiments the genetically modified rodents comprise one or more Fc receptors with a human
extracellular domain (e.g., a
Neonatal Fc Receptor (FcRn), a beta-2-microglobulin polypeptide (beta 2Mu), a Fc epsilon
receptor 1 alpha (Fc[epsilon]R1[alpha]), a
Fc gamma receptor 1 alpha (Fc[gamma]R1a), a
Fc gamma receptor 2a (Fc[gamma]R2a), a
Fc gamma receptor 2b (Fc[gamma]R2b), a Fc gamma
receptor 3a (Fc[gamma]R3a),a Fc gamma
receptor 3b (Fc[gamma]R3b), a Fc gamma receptor 2c (Fc[gamma]R2c)). The transmembrane and cytoplasmic domain of such receptors can be human or non-human (e.g.,
rodent).