Enhanced FcRn-dependent transepithelial delivery of IgG by Fc-engineering and polymerization

Abstract

Monoclonal IgG antibodies (Abs) are used extensively in the clinic to treat cancer and autoimmune diseases. In addition, therapeutic proteins are genetically fused to the constant Fc part of IgG. In both cases, the Fc secures a long serum half-life and favourable pharmacokinetics due to its pH-dependent interaction with the neonatal Fc receptor (FcRn). FcRn also mediates transport of intact IgG across polarized epithelial barriers, a pathway that is attractive for delivery of Fc-containing therapeutics. So far, no study has thoroughly compared side-by-side how IgG and different Fc-fusion formats are transported across human polarizing epithelial cells. Here, we used an in vitro cellular transport assay based on the human polarizing epithelial cell line (T84) in which both IgG1 and Fc-fusions were transported in an FcRn-dependent manner. Furthermore, we found that the efficacy of transport was dependent on the format. We demonstrate that transepithelial delivery could be enhanced by Fc-engineering for improved FcRn binding as well as by Fc-polymerization. In both cases, transport was driven by pH-dependent binding kinetics and the pH at the luminal side. Hence, efficient transcellular delivery of IgG-based drugs across human epithelial cells requires optimal pH-dependent FcRn binding that can be manipulated by avidity and Fc-engineering, factors that should inspire the design of future therapeutics targeted for transmucosal delivery.

Considerations for the Design of Antibody-Based Therapeutics

“…198 Similarly, aggregates of thermally stressed IgG1 have enhanced affinity for FcRn, while immune-complexed and hexamerized IgG1 have enhanced FcRnmediated transepithelial transport. 199,200 For CD40 antibodies, agonism is generally dependent on FcgRIIb-mediated crosslinking. However, covalent multimers of mouse IgG2a were shown to activate CD40 in a FcgR-independent manner, allowing for increased survival in a mouse lymphoma model.…”

“…Attachment of the IgM tailpiece to the IgG C-terminus is another hexamerization approach that allows for enhanced binding to Fc-binding proteins. 200,203 Depending on structure and context, these multimerizing antibodies may be useful for both potentiating and inhibiting the immune functions of complement and FcRs.…”

A comprehensive review of the neonatal Fc receptor and its application in drug delivery

“…Interestingly, this FcRn-mediated enhancement of IgG1 half-life improved antitumor activity of Fc-engineering antibodies in mice(Zalevsky et al, 2010), suggesting that at least in these mice cancer models, increased drug exposure through half-life extension can enhance efficacy and enables less frequent drug dosing(Sockolosky and Szoka, 2015). Very recently, Foss and colleagues have made a thorough comparison on how IgG and different Fc-fusion formats are transported across human epithelial cells(Foss et al, 2016).The authors confirmed that transepithelial delivery is strongly dependent on the format of the ligands and on the appropriate pH conditions, and observed enhanced transport rates upon Fcengineering or polymerization, as compared with intact IgG1(Foss et al, 2016). Furthermore, a number of other mutations to the IgG Fc-domain that alter the pH-dependent binding have been extensively described and reviewed(Chen and Balthasar, 2012;Kuo and Aveson, 2011;Rath et al, 2015;Sockolosky and Szoka, 2015).Altogether, these findings validated the tremendous impact of the Fc engineering strategies, since the several mutations demonstrated the simultaneous modulation of the serum half-life, tissue distribution and activity of a given human IgG (Dall'Acqua et al…”

Intact anti‐LPS IgY is found in the blood after intragastric administration in mice

“…However, studies have shown that due to the structural differences in proteins, the Fc fragment of IgY cannot bind to the Fc receptor on mammalian cell membranes. Thus, IgY does not undergo endocytosis and transport into blood by FcRn . Other studies have indicated that surface modifications of proteins by hydrophobization could improve transport.…”