Flashcards in Lecture 5 - mAbs Deck (71):
Which cell type produces Ig and is used in the lab as an 'Ig producing factory'?
What is a monoclonal antibody?
A population of Ab's from a single B cell clone
(i.e., they all have the same specificity)
What factors give mAbs great therapeutic potential?
• Well tolerated (come from us)
• Very high specificity
What is the half-life of Ab?
Which types of diseases are mAbs mainly used for at the moment?
• Auto-immune conditions
What are 'The Big 5' mAbs?
• Adalimumab (Anti-TNF)
• Infliximab (Anti-TNF)
• Trastizumab (Anti-HER2)
• Bevacizumab (Anti-VEGFA)
• Rituximab (Anti-CD20)
What is the name of Anti-TNF?
What is the name for Anti-CD20?
What is the name for Anti-VEGFA?
Avastin / Bevacizumab
What is the name for Anti-HER2?
Herceptin / Trastuzumab
What recognition did the researchers who came up with mAbs receive?
Nobel Prize for Medicine in 1984
Describe the process of harvesting mAbs from mice
1. Mice spleen cells + myeloma cells
4. Culture in drug
5. Selection of positive cells
6. Harvest of mAbs
What are the shortcomings of mAbs from mice?
• They are recognised as foreign and thus have a short half life
• The 'mice' constant region means that they are lacking some effector functions
Describe 'Humanisation' of mice mAb
1. CDR grafting in vitro
• Mouse variable region grafted onto human constant region
• Ig are fully human apart from the CDRs
• Longer half life in serum (than fully mouse)
2. Transgenic mice
• Have human Ig genes
• Challenge mice with antigen
• Mice produce human Ig
• Very good half life
3. Harvesting from humans
• Harvest B cells from immune individual
• Fuse with EBV to immortalise cells
• Screening to select for the desired specificity
• Ig isolation
How good are humanised mAbs raised in vitro?
Still fairly crude
Describe mAbs raised in transgenic mice
• have human Ig genes (C or V & C)
These mAbs are really good because they contain barely any mice parts
Describe mAb generation from humans
1. Infected human with high affinity, IgG
2. Memory cells collected
3. Immortalisation: Memory cells infected with EBV
5. mAbs harvesting
What are the advantages and disadvantages of mAbs from infected humans?
• not rejected by patients
• mAbs have specificity that was effective at clearing the infection
• Specificities limited to foreign immunogens
What are human mAbs most often used for?
What are the pros of passive immunisation?
Useful when a very quick immune response is needed (HIV, SARS, influenza)
What is 'naked mAb' useful for?
ADCC: Antibody dependent cell-mediated cytotoxicity
CDC: cell dependent cytotoxicity
What are some ways we can 'arm' mAbs?
• Bispecific mAb
• Cellular immunoconjugates
Radioactive substance conjugates to a mAb which is specific for a tumour cell
Cytokine conjugated to a mAb specific for a tumour cell
Describe Cellular immunoconjugates
mAb bispecific for tumour cell and killer cell
This brings the killer cell right to the tumour cell
What are the mechanisms of action of mAbs?
1. Ligand blockade
2. Receptor blockade
3. Target cell depletion
4. Target cell activation
Which mAb is used against Rheumatoid arthritis, psoriasis & Crohn's disease?
• Remicade (Infliximab)
• Humira (Adalimumab)
Which mAb is used for anti-angiogenesis and cancer therapy?
• Avastin (Bevacizumab)
Which mAb is used for Breast cancer?
• Herceptin / trastuzumab
Which mAb is used for Rheumatoid arthritis and non-Hodgkins lymphoma?
Describe the mechanism of action of anti-TNFa
• "Ligand blockade"
• mAb specific for TNF (pro-inflammatory cytokine)
• TNF bound by mAb, so it can't bind to TNF-R on inflammatory cells
Describe improvement in Rheumatoid arthritis with Remicade
Increased function of joints compared to patients not taking the drug
What is the role of TNF-a in Rheumatoid arthritis?
• Strong pro-inflammatory cytokine
• Leads to joint destruction
Describe the success of Avastin / Bevacizumab
mAb used in cancer, anti-angiogenesis agent
• Better survival rates compared to conventional therapy
• However, benefit is not that great
• Not a cure
Describe the function of anti-RANKL mAbs
• "Ligand blockade"
• Specific for RANKL, which is a factor that increases the action of osteoclasts
• By blocking RANK-L, we decrease bone resorption in Multiple Myeloma
Which cancer cells produce lots of RANK-L?
Where is RANK?
What are some examples of mAb ligand blockade?
• Anti-TNF-α (Adalimumab, Infliximab)
• Anti-RANK-L (Denosumab)
• Anti-VEGFA (Bevacizumab)
Describe receptor down-modulation
When receptors are engaged a lot, they are taken back into the cell and degraded, in order to down regulate the response
What are some examples of mAb receptor blockade or down-regulation?
Receptor down regulation: Anti-HER2
• HER2 is a receptor in malignant breast cancer cells
• Tumour growth is suppressed by blocking the receptor
What is HER-2?
In which disease is it overactive?
• Epidermal GF receptor
• Breast cancer
What are some ways that depletion occurs?
• MAC formation
Which cells express CD20?
All B cells
Describe the action of Rituximab
• mAb specific for CD20
• Brings about transient depletion of ALL B cells
Describe the effectiveness of Rituximab
50% remission of B cell lymphoma (eg. non-Hogdkins lymphoma) patients
What is combination therapy?
Conventional treatment + mAb
What was Rituximab's initial use, and what is it used for now?
Started off as a cancer therapy
Now used for auto-immune conditions
What is Rituximab specific for?
What is Herceptin specific for?
What is Remicade specific for?
What is Avastin specific for?
Describe mAbs used for cell activation
What is significant about this?
• mAbs specific for parts of T cells
• When engaged, lead to activation of T cells
(**T cell activation without antigen!**)
• more T cell cytotoxicity
• more T cell help
2. Anti-CD28 → this didn't end well
What happened with the first in man trials of Anti-CD28?
Massive cytokine storm and organ failure in the 6 healthy subjects
What is Ipilimumab, and what disease is it used for?
Used in metastatic melanoma
What is CTLA4?
Expressed on the surface of T cells after activation by DCs to prevent further activation
What is the effect of Anti-CTLA4?
Blockage of inhibition of T cell activation
→ More T cell activation
What are some limitations of mAbs as therapeutics?
• Anti-CD28 disaster
• infections (in immune cell depletions)
• Anti-mAb antibodies (loss of efficacy)
What is an orphan disease?
Rare diseases with limited treatment development
Describe the structure of CARs
Chimeric antigen receptors
• External Ab 'for specificity)
• Intracellular T cell activation section
Describe how CARs could be used to treat disease
(Chimeric antigen receptor)
1. T cells isolated from patient
2. Viral vector delivers anti-CD19 CAR gene to T cells
3. T cells in culture express anti-CD19 CAR
4. Lymphocytes killed in patient
5. CAR expressing T cells reinstated in patient
6. CAR expressing T cells recognise B cells (through CD19) and induce CTL killing
7. Depletion of B cells
Used for CLL & Follicular lymphoma
How are the CARs put into T cells?
What is the effect of CAR therapy in B cell cancers?
Complete depletion of B cells
On which cells is CD19 expressed?
What is IL-1β?
Brings about systemic features of inflammation:
• tissue damage
Which diseases is Anti-IL1β used for?
What is the mechanism of action?
How has it been received in patients?
Used for CAPS: a collection of rare autoimmune disorders
Mechanism of action:
• Ligand blockade
• Complete response within 7 days
• Well tolerated
• Long lasting
• No side effects
What are 'off-label' trials?
A drug becomes licensed for one rare disease, and then is use in trials for more common diseases.
This is what happened with Rituximab and now for Anti-IL1β mAbs
What other disorders is Anti-IL1β being used for?
• Juvenile idiopathic arthritis
• Late onset Type 2 Diabetes
(chronic inflammatory conditions)
Describe the mechanism of B cell depletion with Anti-CD20 (Rituximab)
→ mAb binds to CD20
• IgG(1) binds to CD20
• NK cells bind IgG with IgγR I
• NK cells induce apoptosis of B cell
2. Complement activation
• IgM binds to CD20
• Activation of Cq1
• Complement cascade
• Formation of membrane attack complex
• Ig binds to CD20
• Phagocytes binds Ab with FcR
• Intracellular killing in phagosome
What is the mechanism of action of Anti-VEGFA?
Which class are monoclonal antibodies?