mAbs recycling Flashcards
what mediates recycling of albumin and IgG
neonatal Fc receptor
what is IgG?
antibodies
what happens when a antibody binds to the Fc receptors on cells?
IgG moves into one of t he endocytotic vesicles
the unbound IgG will be sorted for catabolic degradation to just the amino acids
those bound will get recycled and remade
pH raises to 7.4 and the binding stops and the IgG is released back into the blood
how does pH regulate Fc binding to the FcRn:
IgG binds at ______ pH
IgG binds at ACIDIC pH
what is the CQAs? example
critical quality attributes
FcRn binding affinity is a CQA defined by industry
what does industry want mAbs to do in relation to Fc receptors?
bind well but also be released when needed
how can we modify mAbs binding to FcRn?
modifying THE aa SEQUENCE
When the antigen is bound to the mAbs can it still be taken up by FcRns?
yes as the antigen is bound to the FAB region and the Fc region can bind to the FcRn at the same time
what can this dual binding to antigens and FcRn lead to in relation to antigens half life?
is this good or bad
extension of half life- we might not want this
need to find a way to release the antigen from the FAB during recycling
IgG types 1 and 2 and 4 have a half life of?
21 days
IgG type 3 has a half life of?
7 days
as you _____ the molecular mass you can have a very high half life
decrease
types of IgG’s?
natural and recombinant
TF: all IgGs are glycosylated
true
TF: glycosylation is required for an IgG antibody long half life
FALSE
what is the shorter half life of Fc fusion molecules in comparison to the whole IgG been attributed to?
the lower binding affinity to FcRn
the glycol mediated disposition and the receptor (of fusion partner) mediated disposition
fusion protein is a ______ ______ of a IgG. this means ______ is important
synthetic mimic
glycosylation
why is charge important on mAbs?
as often the surface of a cell is negatively charged and the receptors can also be negative
what is a powerful way of improving PK of mAbs relating to charge?
change the pI
what can cause charge variation of mAbs
manufacturing:
uncontrolled mutations
glycosylation
what is the normal pI of mAbs?
about 8
mAbs: with a pI of about 8 and at pH 8 you have a half life of about ______
20 days
as you increase the pI, why can recycling decrease?
the molecule will be constantly charged, meaning it doesn’t feel the changes in endocytotic vesicle so doesn’t bind to FcRn and doesn’t get recycled
Hence increasing the pI decreases the half life.
increasing the pI _______ the half life
decreases
______ clearance with a low pI
lower
what must be done to ensure the quality of the mAbs
prevent charge/ pI variations
what can the administration of therapeutic mAbs lead to?
formation of anti-drug antibodies (ADA)
what do ADAs do to mAbs
therefore effects
bind to the mAb, form immune complexes impacting on PK, PD, safety and efficacy of mAbs.
bad responses of ADAs
hypersensitivity: anaphylaxis
accelerated clearance
TF: ADAs are neutralising
false
can be neutralising or non-neutralising
drop of mAb concentration in blood could be due to?
ADAs
This drop is probably due to a higher clearance of immune complexes
how to tackle decreased blood concentrations due to ADAs
might need to increase dose to achieve desired exposure. This drop is probably due to a higher clearance of immune complexes
binding of mAb to FcRn and recycling contributes to?
half life
mAbs PK is usually dependent on?
biology of target antigen
PK dose proportionality of mAbs?
Non-linear PK at low doses
Linear PK at high doses after saturation of target
mAbs distribution is usually limited too?
blood and interstitial space
mAbs partitioning from blood to tissues is typically ____%
5-15%
TF: there is no clearance of intact antibody
TRUE
TF: immunogenicity in animals is predictive of immunogenicity in humans
FALSE
Novel antibody formats?
antibody fragments
antibody drug conjugates
bispecific: modified IgG to which a second part variable region has been attached so antibody will bind to 2 targets
multi specific- antibody possessing multiple binding sites
bispecific IgG is much more _____
unstable
example of a antibody fragment?
take one part
e.g. single chain Fc region
novel formats are ____ complex than mAbs
more
in novel formats, different molecular domains can be linked through?
what does this mean?
flexible linkers- we pick and choose what we want in the structure and discard what we dont want
for novel formats there is a _______ in stability
decrease
for novel formats there is a _______ in solubility
decrease
why is there decreased stability and solubility in novel formats of mAbs?
synthetic so can form aggregates
aggregates are more likely to trigger?
an immune response
novel formats tend to lose a lot of the?
dose
what do fusion proteins consist of?
a protein, peptide or receptor exodomain fused to the Fc region of the mAb
Fc portion typically consists of the hinge region usually along with the conserved N-glycosylation site in the CH2 domain
the Fc portion in fusion proteins typically contain?
the hinge region usually along with the conserved N-glycosylation site in the CH2 domain
in fusion proteins the half-life is ______
extended
what is the most prominent antibody fragment?
FAB
what drugs do Antibody drug conjugates (ADC) deliver?
mAb employed as drug delivery agents with chemotherapeutic drugs, immunotoxins, radioisotopes or cytokines
how is the drug released from the antibody?
cleavable linker in either lys or cys residues allowing release
ADCs can be either ____ specific or ______ specific
bi
multi
what does bi or multi specific mean?
antibodies contain two or more variable domains with affinity for different antigen
Bispecific formats comprise ….. based constructs
IgG like and FAB fragment based constructs
