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Are endosomal trafficking parameters better targets for improving mAb pharmacokinetics than FcRn binding affinity?

Authors
  • Gurbaxani, Brian1
  • Dostalek, Miroslav
  • Gardner, Iain
  • 1 Chronic Viral Diseases Branch, Division of High-Consequence Pathogens and Pathology, National Centre for Emerging and Zoonotic Infectious Diseases, Centres for Disease Control and Prevention, Atlanta, GA, USA. Electronic address: [email protected]
Type
Published Article
Journal
Molecular immunology
Publication Date
Dec 01, 2013
Volume
56
Issue
4
Pages
660–674
Identifiers
DOI: 10.1016/j.molimm.2013.05.008
PMID: 23917469
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

F.W.R. Brambell deduced the existence of a protective receptor for IgG, the neonatal Fc receptor (FcRn), long before its discovery in the early to mid-1990s. With the coincident, explosive development of IgG-based drugs, FcRn became a popular target for tuning the pharmacokinetics of monoclonal antibodies (mAbs). One aspect of Brambell's initial observation, however, that is seldom discussed since the discovery of the receptor, is the compliance in the mechanism that Brambell observed (saturating at 10s-100s of μM concentration), vs. the comparative stiffness of the receptor kinetics (saturating in the nM range for most species). Although some studies reported that increasing the already very high Fc-FcRn affinity at pH 6.0 further improved mAb half-life, in fact the results were mixed, with later studies increasingly implicating non-FcRn-dependent mechanisms as determinants of mAb pharmacokinetics. Mathematical modelling of the FcRn system has also indicated that the processes determining the pharmacokinetics of mAbs have more nuances than had at first been hypothesised. We propose, in keeping with the latest modelling and experimental evidence reviewed here, that the dynamics of endosomal sorting and trafficking have important roles in the compliant salvage mechanism that Brambell first observed nearly 50 years ago, and therefore also in the pharmacokinetics of mAbs. These ideas lead to many open questions regarding the endosomal trafficking of both FcRn and mAbs and also to what properties of a mAb can be altered to achieve an improvement in pharmacokinetics. Published by Elsevier Ltd.

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