Monoclonal Antibody Flashcards
How many chains make up Ig?
4
What does the immunoglobulin fold result in?
strongest structure in protein biology
What does IgG have?
Sugar that is glycosylated making it a glycoprotein
What is long-term immunity down to>
Antibody production & secretion
What type of response occurs due to infection?
Polyclonal response
What is the polyclonal response?
Antigen cross-linking by multiple antibodies
Can you mimic the polyclonal response and why?
No - we need to find one monoclonal antibody that recognizes one epitope
For clinical treatment what do we need the monoclonal antibody to be?
Specific
High binding affinity for target
What is the immunoglobulin structure?
Tetrameric - 4 peptide chains joined by disulfide bonds
What region of the Ab is the antigen binding site?
Fab
What section is critical for pharmacokinetics?
Fc - trunk
What are characteristics of the finger part of the Ab?
hyper variable - short gene segments any combination of aa
Binds antigens
Define clinical pharmacokinetics?
Application of pharmacokinetic principles to the safe & effective therapeutic management of drugs in an individual patient
What part of the antibody is the PK profile relevant to?
Fc portion
What are 4 desirable characteristics of antibody drugs?
Good stability & solubility
long persistence
high selectivity & specificity
low risk for bioconversion to toxic metabolites
What is half life?
Time taken for serum conc. of drug to decrease by half its steady state conc
What is difference between selectivity & specificty?
Selectivity - breast cancer tissue
specificity - receptor on breast cancer cell
What does CDR stand for?
complementary determining regions
What is a paratope?
sequences of Ab making contact with antigen?
What is the epitope?
Sequence of antigen making contact with Ab
What is the CDR responsible for?
Aa in CDR have right chemistry & folded in right way for interface for epitope & paratope bonding
What is the half-life of Abs down to?
Salvage from lysosomal pathway by FcRn
What is the MoA of salvaging Ab?
Fc gamma receptor binds to Fc portion ->
Internalized in early endosome -> pH in endosome drops ->
Antibody stops recognizing each other -> new receptor takes over (FcRn) -> rescues Ab ->
Returns to surface and is let go
What gives pH control in IgG and FcRn recognition?
Glycoprotein
What are 4 downfalls of IgG?
Not orally available
incomplete absorption following IM or SC admin
nonlinear distribution/elimination
leads to endogenous antibody response - alter efficacy
Who were the first to produce the first murine mAbs from hybridomas?
Kohler & Milstein
What were 4 downfalls of murine mAbs?
Allergic reaction
induction of anti-drug antibodies
short half life
poor recruiters of effector function ADCC & CDC
What is muromonab-CD3?
immunosuppressant drug reducing acute rejection in organ transplants
What does muromonab-CD£ target?
CD3 receptor on T cells
What was developed to overcome downfalls of murine Ab?
Chimeric mouse-human antibodies were developed (ximab)
How was ximab made?
grafting antigen-specific variable domain of mouse (35%) onto constant domains of human Ab (65%)
What was the final engineered mAb?
humanized (zumab) developed
What is the zumab?
Murine hypervariable regions (CDR) onto human Ab framework (95% human)
What four thing does targeted cancer therapies do?
interferer with cell growth signaling or tumors blood vessel development
promote cancer cell death
stimulate immune system to destroy specific cancer cells
deliver toxic drugs
What are 4 targets for cancer biology?
VEGF
EGFR
CD19
immune checkpoints
What is HER2?
receptor tyrosine kinase essential for cell division & proliferation eg. Cardiac myocytes
What are tyrosine kinase domains activated by?
Homodimerization & heterodimerization generally induced by ligand binding
What happens when receptor overexpression or mutation occurs?
Induce dimerization - promote cellular proliferation & survival
What does HER2 signalling promote cell growth through?
RAS-MAPK pathway
What does HER2 signalling inhibit cell death through?
PIK3 AKT (target of mTOR) inhibits apoptosis
What does trastuzumab target?
juxtamembrane (epitope) portion of EC domain of HER2 receptor -> prevents tyrosine kinase activation
What doe preclinical models of Trastuzumab suggest?
recruits immune effector cells responsible for antibody-dependent cytotoxicity
What is the loading dose of trastuzumab?
8mg per kg given IV
What is a side effect of trastuzumab?
5% had cardiotoxic effects
Why are people primarily resistant to trastuzumab?
Breaking of EC domain leaving P95 has already occurred - patients have already lost EC before treatment - epitope is gone
What % of patients develop secondary resistance to Trastuzumab?
70%
Which 2 proteins play are role in primary/acquire resistance to trastuzumb?
PTEN
Src
