The interplay of non-specific binding, target-mediated clearance and FcRn interactions on the pharmacokinetics of humanized antibodies

Abstract

The application of protein engineering technologies toward successfully improving antibody pharmacokinetics has been challenging due to the multiplicity of biochemical factors that influence monoclonal antibody (mAb) disposition in vivo. Physiological factors including interactions with the neonatal Fc receptor (FcRn) and specific antigen binding properties of mAbs, along with biophysical properties of the mAbs themselves play a critical role. It has become evident that applying an integrated approach to understand the relative contribution of these factors is critical to rationally guide and apply engineering strategies to optimize mAb pharmacokinetics. The study presented here evaluated the influence of unintended non-specific interactions on the disposition of mAbs whose clearance rates are governed predominantly by either non-specific (FcRn) or target-mediated processes. The pharmacokinetics of 8 mAbs representing a diverse range of these properties was evaluated in cynomolgus monkeys. Results revealed complementarity-determining region (CDR) charge patch engineering to decrease charge-related non-specific binding can have a significant impact on improving the clearance. In contrast, the influence of enhanced in vitro FcRn binding was mixed, and related to both the strength of charge interaction and the general mechanism predominant in governing the clearance of the particular mAb. Overall, improved pharmacokinetics through enhanced FcRn interactions were apparent for a CDR charge-patch normalized mAb which was affected by non-specific clearance. The findings in this report are an important demonstration that mAb pharmacokinetics requires optimization on a case-by-case basis to improve the design of molecules with increased therapeutic application.

Keywords:

• non-specific binding
• neonatal Fc receptor (FcRn)
• antibody pharmacokinetics
• charge interactions of IgGs
• target mediated disposition

Disclosure of Potential Conflicts of Interest

All authors in this report are employees of Eli Lilly and Company, Indianapolis, IN. The authors do not have any conflict of interest or financial disclosure to report.

Acknowledgments

The authors thank Robin Brown and Andrea Sperry for measuring the concentrations of the mAbs, Chi-kin Chow for purification of antibody variants, and Yu Tian for determining the pI values of the antibodies.