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Cicrculation of antibodies in blood is extended by what
FcRn
All four IgG subclasses bind to what
Neonatal Fc receptor (FcRn) at a pH <6.5
FcRn Recycling Steps
IgGs enter into endosome via fluid phase endocytosis
Endosomes are acidified by ATPase H+ pump
In endosome FcRn binds IgGs at pH 5-6.5
FcRn bound IgGs are protected from lysosomal degradation
Bound IgGs are recycled to the plasma membrane
IgGs are released back into circulation (pH 7.4)
FcRn recycling creates a
reserivor in blood endothelium, thereby extending their half-lives in circulation
Fc glycans. are important for
structural integrity and conformation
FcRn binds to Fc domains
-at pH 6-6.5
-Interactions depend on Ch2/CH3 amino acids and carbohydrates
What is a major therapeutic platform
recombinant monoclonal antibodies
Process-dependent complexities: Produced in living cells (hosts)
-Mammalian cell secretion
-Composition of IgG carbohydrates is a function of the host cell lines
-Enzymatic glycosylation (oligosaccharyltransferase (OST))
-Site specific—> Asn 297 on CH2 domain —> N-Glycens
-Complex branched carbohydrates
Two laws having to do with Biosimilars
Affordable Care Act and Biologics Price Competition and Innovation Act (BPCIA)
Biosimilars
-Generally made from living sources
-Require a specialized process to produce
-Nearly identical to original biologics
-Faster development process
-Usually less expensive than original biologics
Generics
-Generally made from chemicals
-Have a simpler process to copy
-Copy of brand-name drugs
-Faster development process
-Usually less expensive than brand-name drugs
Note 
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