A number of challenges impede the more widespread use of proteins as drugs including: their rapid elimination from circulation and the need to dose proteins via injection. Strategies that overcome these limitations could decrease dosing frequency and improve patient convenience and compliance. Engineering proteins to interact with the MHC Class I-like neonatal Fc receptor (FcRn) represents a promising strategy to improve circulation time and enable alternative routes of protein administration. FcRn is expressed in several organs and tissues in which it serves a distinct role in the protection of IgG from catabolism and/or transport of IgG across epithelial barriers. Peptide sequences that bind to FcRn with moderate affinity have been identified by phage display and may be amenable for incorporation into proteins in order to improve their pharmacokinetic properties and enable pulmonary protein delivery. We will investigate factors that affect the circulation time and epithelial transcytosis of FcRn binding peptide-modified proteins as a general strategy to improve protein circulation and enable pulmonary protein delivery.
Three specific aims will be aggressively pursued.
Aim 1. (A) Synthesize peptides ligands for FcRn and confirm they bind and are transported by FcRn;(B) Generate recombinant FcRn binding fusion proteins in E. coli based upon sequences identified in Aim 1A and characterize their interaction with FcRn.
Aim 2. Determine the relationship between FcRn binding, in vivo circulation time, pulmonary absorption, and pulmonary retention in a human FcRn transgenic mouse model.
Aim 3. Evaluate the therapeutic potential of FcRn binding peptide-modified human growth hormone (hGH) in a murine model of growth hormone deficiency. Our studies will generate a better understanding of the factors that control internalization and transcytosis of cargos attached to an FcRn ligand. Success in this research could enable the development of new protein-based therapies with convenient routes of administration that could greatly improve treatment in problematic patient populations such as children and the elderly.

Public Health Relevance

Improved PK and Delivery of Protein Modified with FcRn Binding Ligands Project Relevance Our goal is to engineer proteins to interact with FcRn and use them to define factors that affect FcRn mediated protein circulation and pulmonary absorption. Successful completion of the plan would result in a novel method to improve protein delivery and pharmacokinetics that could be translated into improved protein therapeutics for treating human disease.

National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Exploratory/Developmental Grants (R21)
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Gene and Drug Delivery Systems Study Section (GDD)
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Tucker, Jessica
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University of California San Francisco
Schools of Pharmacy
San Francisco
United States
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Sockolosky, Jonathan T; Szoka, Francis C (2015) The neonatal Fc receptor, FcRn, as a target for drug delivery and therapy. Adv Drug Deliv Rev 91:109-24
Sockolosky, Jonathan T; Kivimäe, Saul; Szoka, Francis C (2014) Fusion of a short peptide that binds immunoglobulin G to a recombinant protein substantially increases its plasma half-life in mice. PLoS One 9:e102566
Sockolosky, Jonathan T; Szoka, Francis C (2013) Periplasmic production via the pET expression system of soluble, bioactive human growth hormone. Protein Expr Purif 87:129-35
Sockolosky, Jonathan T; Tiffany, Matthew R; Szoka, Francis C (2012) Engineering neonatal Fc receptor-mediated recycling and transcytosis in recombinant proteins by short terminal peptide extensions. Proc Natl Acad Sci U S A 109:16095-100