Advances in Monoclonal Antibody Therapy Flashcards
Small molecule drug
- Low MW
- Chemically synthesised (defined chemical reactions)
- Simple, well defined structure
What are small molecules known as?
The pillars of traditional medicine
Examples of small molecule drugs targets
Extracellular proteins
Intracellular receptors
In cytoplasm, nuclei, CNS
Examples of small molecule drugs
Aspirin
Penicillin
Paracetamol
Lipitor (Atorvastatin)
Biological molecule
- High MW
- Derived from living organisms (manufactured)
- Large, complex, dynamic structure
Uses of large biologics
- Therapeutic proteins (peptides, antibodies)
- Nucleic acid based therapies (RNAi, gene therapy/editing)
- Blood components
- Cellular therapies (e.g. CAR T-cell therapy)
- Tissue therapies (allogenic transplants)
50% of biologics marketed today are?
Monoclonal antibodies (fastest growing class of drugs)
Monoclonal antibody
An example of a biologic
High specificity, allowing the stimulating of the immune system to attack certain antigenic cells
What is the large biologic that is the 2nd best selling drug (2021)? What is it used for?
Humira (mAb)
- Autoimmune disease treatment (rheumatoid arthritis, psoriatic arthritis, Crohn’s, psoriasis)
- Forecasted to be replaced by Keytruda by 2024 (mAb for cancer immunotherapy)
Small molecules vs Biologics
Small mol: low MW, simple structure, independent of manufacturing process, identical copies possible, well-defined, stable, non-immunogenic
Biologic: high MW, complex structure, defined by exact manufacturing process, identical copies impossible, can’t be characterised completely, unstable, immunogenic
Advances in biotechnology enabled?
Synthesis of biological molecules (proteins) in microorganisms & other living cells (via recombinant DNA technology)
Key areas for mAb use
- Immunotherapy
- Inflammatory diseases
- Autoimmune diseases
- CVD
- Oncology
- Neurodegenerative diseases
- COVID-19
Briefly discuss mAb therapy
- Very specific
- Immunotherapy
- Uses mAbs to bind monospecifically to certain cells or proteins
- Stimulation of patient’s immune system to attack certain cells
Antibody functions
- Neutralisation
- Agglutination
- Precipitation
- Complement activation
How do mAbs work?
- Variable region of antibody binds to a single antigen
- Specific binding
- mAbs are useful for highly targeted therapeutic administration
- Minimises adverse off target side effects
- Useful for delivery of toxic drugs
True or False: The host’s immune system produces long-term Abs after short-term mAb drug administration
True
The first reliable source of mAbs
Immunotherapy, 1970s, Hybridoma technology
- Orthoclone 1986 - limited organ transplant rejection
- Can take the hybridoma out of the mouse & modify it → develop it into a mAb
The biggest manufacturing problem associated with mAbs
Low stability
Discuss Keytruda (Pembrolizumab)
Humanised mAb used in cancer immunotherapy
- Binds specifically to PD1
- Few severe adverse events (5%: fatigue, rash, dry mouth)
- Can be combined with targeted and untargeted drugs
(i) Chemotherapy
(ii) Radiotherapy
(iii) Immune modulators
What is PD-1?
PD1 = programmed cell death protein 1
- PDL-1: transmembrane protein of cancer cells, which prevents PD-1 from identifying it & the immune system from killing the cancer cells
PD1 blockade: ↑ T-cell mediated anti-tumour immunity, inhibits T-cell PD1/tumour cell PD1 interaction, potential treatment strategy
Is cytotoxic activity associated with Keytruda?
Cytotoxic activity occurs when Fc receptors are engaged and the complement system is activated. This does not occur in Keytruda → no cytotoxic activity
Keytruda and metastatic melanoma
median survival <12 months
- Assoc. with genetic mutations
- Inhibitors - 10% response
- Conventional chemotherapy ineffective
- Few treatment options
- Keytruda - for non-responders/relapse
- 1st trial saw up to 52% overall response rate
- Overall response rates consistently higher than chemotherapy
- Progression free survival higher than chemo
- Improved safety profile vs chemo & other mABs (ipilimumab)
- FDA approved 2014
Keytruda and non-small cell lung cancer (NSCLC)
- NSCLS: median survival ~10 months
- Platinum based chemotherapy (first line treatment)
- Few other options
- 1st PD1 blockade trial: Nivolumab
- ↑ overall response rate to 20% compared to 9% seen with chemo
- Keytruda - overall survival superior to chemotherapy
- ↑ when >50% of tumour cells expressed PDL1
- ↑ progression free survival
- Fewer adverse events
- FDA approved 2015
Keytruda and lymphoma
↑ PDL1 expression in Hodgkin Lymphoma
- Good response to PD1 blockade
- Nivolumab - 87% overall response rate
- Keytruda for non-responders/relapse/ineligible for transplant
- Poor response in early studies/trials
- Toxicity (dosages v important) & SAEs
- 2mg/kg every 3 weeks - complete response, no toxicity
- Lower doses could be more useful for lymphoma treatment
mAbs vs standard cancer therapies
mAbs: ~35 FDA approved, restricted admin (I.V. injection or infusion), unstable, highly targeted ‘tailored’ approach (single antigen), few side effects, takes longer for mAb to work (pseudoprogression), long term efficacy & protection, low cytotoxicity
Chemo: ~150 approved, unrestricted admin, stable, untargeted, impairs ca. cell’s ability to replicate, many side effects, immediate effect, treatment effects last only as long as drug remains in system, high cytotoxicity
Why do we see a lot of relapses with cancer?
If all of the cancer cells are not killed by the chemo, they will begin to replicate again
Successful development of mAb requires
- Identification & creation of a selective, potent target molecule
- Humanisation of sequences
- Affinity maturation
- Fc engineering (modulation of effector functions)
- Engineering to address biophysical liabilities
the most commonly used animals in mAb development
Non-human primates (NHPs)
Challenges associated with NHPs
- Critical differences in NHP and human physiology
- Imperfect translation of study results to human safety effectiveness (due to potential differences in target molecule activity)
- Ethical concerns
Solution to NHP challenges
Mouse target knockout phenotypes
- In vitro & in silico (system pharmacology, modelling)
- Reduces animal use
- Improves safety prediction
- Improves overall mAb development process
- Reduces challenges of interspecies translation
mAbs are selected based on
- Affinity
- Potency
- Efficacy
- Biological activity
Significant challenges associated with manufacturing mAbs
- Poor expression
- Solubility
- Cross reactivity (with different molecules)
- Poor pharmacokinetic profiles
- Product stability
(due to molecule complexity)
Why are mAbs so unstable?
Because they have to be highly concentrated (due to FDA regulations - volume of SC injection must be <1.5ml)
Disadvantages of highly concentrated mAbs
- Reduced volume for mAb molecules - crowding
- Formation of irreversible non-covalent protein aggregates
- Increased viscosity (challenging to fill product)
Solutions for product stability
Addition of excipients i.e. sugars
- Prevent formation of irreversible aggregates
- Sugars interact with H2O molecules, not proteins
- Protein molecules can maintain native conformation
- Reduces aggregates
mAb efficacy linked to structural, conformational & chemical stability
Why is stability management critical?
Reduces physical/chemical degradation
Stabilisation strategies
- pH optimisation
- Effective buffer components
- Surfactants - stabilise protein molecules (making them less susceptible to these stresses that can cause physical & chemical degradation)
i. e. sugars and polyols - have antioxidant & cryoprotective properties
Benefit of Fc fusion proteins
i.e. Fusion of coding sequence for Fc region of mAb with coding sequence of another protein
Proteins/peptides have short half lives - Fc fusion extends half life
