Humanized FcRn mouse models for evaluating pharmacokinetics of human IgG antibodies

•We have developed several humanized FcRn mouse models.•hFcRn mouse models are suitable for PK assays of human/humanized mAbs and Fc-based therapeutics.•These hFcRn mouse models correlate well with non-human primates and human clinical trial data.•These models are also applicable for efficacy validation, especially for xenograft studies. A key element for the successful development of novel therapeutic antibodies is to fully understand their pharmacokinetic and pharmacodynamic behavior before performing clinical trials. While many in vitro modeling approaches exist, these simply cannot substitute for data obtained from appropriate animal models. It was established quite early that the unusual long serum half-life of immunoglobulin G’s (IgGs) and Fc domains are due to their rescue and recycling by the neonatal Fc receptor (FcRn). The diverse roles of FcRn became apparent after isolation and cloning. Interesting are the significant species differences between rodent and human FcRn reactivity, rendering wild type rodents an inadequate model for studying IgG serum half-life. With the advance of genetic engineering mouse models have been established expressing human FcRn, and lacking mouse FcRn protein. These models have become highly relevant tools for serum half-life analysis of Fc-containing compounds.