Biologic Flashcards
What is post-translational modification and give examples
A covalent alteration of a peptide sequence that occurs after the peptide has been synthesized.
Examples: Glycosylation, Sulfation, Phosphorylation, Acetylation.
What are good organisms/hosts for synthesizing biologics
Cannot be a prokaryote as they are not capable of PTM.
* Human kidney cells
* Chinese hamster cells
What kind of biologic is Infliximab
TNF inhibitor
Monitoring b4 therapy
Co-morbidities
FBC
Renal function
LFT
Tb test (have prophylaxis if at risk)
Chest x-ray
Infliximab indications
RA
Crohn’s disease
UC
Psoriasis
What is a biosimilar
Highly similar to its biologic and has no clinical meaningful difference to its reference product
Tocilizumab
Anti IL-6
Zu = Humanised
Abatacept
Anti-costimulation
Advantages of biologics
Are highly specific and selective
Large SA = Good for binding
Disadvantages of biologics
- Antigenic = often cause immune response
- Not membrane permeable
- Require organism for synthesis (difficult to synthesize)
- Biosimilars require same amount of tests as reference product
Advantages of E.coli host
- It is well studied
- Quick & cheap
- Large scale fermentation possible
- Can produce a lot of heterologous proteins (High yield)
Disadvantages of E.coli host
- Unable to carry out Post-translational modifications
- Potential pyrogenic
What is glycosylation
- Occurs within ER, catalysed by oligosaccharyl transferase
- Oligosaccharyl chain fused to polypeptide
- Followed by oligosaccharide timming
What is oligosaccharyl trimming
The adding and removal of futher saccharides vua various other enzymes. This process aids proteins folding & transport within the cell.
Oligosaccharyl trimming results in different glycoforms of the same product.
Types of glycosylation
N-linked glycosylation
O-linked glycosylation
What are glycoforms
Different versions of the same product after it has undergone glycosylation. They can impact…solubility, stability, half-life, biological activity, immunogenicity .
Describe hybridoma process
A process that mass produces monoclonal antibodies (usually from mice).
1. Immunize mouse with specific antigens
2. Isolate plasma cells produced
3. Fuse plasma cell with immortal myeloma cell
4. Grow and reproduce hybridoma cells in medium
5. Identify hybridoma with highest Ab production
6. Replicate and mass produce
Drug requirements for liposome use
- Log P < 1.7 - Drug incorporated in aqeuous compartment
- Log P > 5 - Drug incorporated within lipid bilayer
- 1.7-5 = Can diffuse out of liposome (loss of drug)
Common modifications for liposomes and why
PEGylation - Addition of charged lipids on surface = Stealth
Cholesterol - Lipophilic, rigid, planar structure = Reduces bilayer permeability ∴ ↑ Drug retention
Stops liposomes from coalescing & aggregating via steric propulsions
Benefits of encapsulation
- Drugs can have bad pharmacokinetics & properties
- Drug vehicles can exchange their properties for the drugs
- Liposome can be tailored for specific targets
- Can act as drug reservoir - sustained drug release (beneficial if drug is rapidly metabolised)
- Protection from DNAase, RNAase, Protease for specific drugs
What is drug loading & how is it different to the standard method
Liposome is preformed w/o drug
Contains trapping agent in aqeuous comp - ensures drug retention
Can have gradient (pH, ionic) that drives loading into liposome
Is a better process for drugs within 1.7-5 perhaps
A solution for Log P 3.4 drug
Introduce it into a modified liposome that consists of a trapping agent in the aqeuous compartment so that it does not diffuse into the lipid bilayer. Use a pH or ionic gradient to drive the drug loading.
MPS depoting
Large liposomes are likely to be recognised by blood opsonins and uptaken into the mononuclear phagocytic system. Accumulation of liposomes here leads to the breakdown and therefore slow release of drug into circulation (similar to a slow transfusion.)
What happens to large liposomes in the blood
They are opsonised and depositted in the MPS
Negatives of MPS depoting
Cancer medication can cause toxic side effects for longer due to MPS depotting.
A solution to MPS depotting
PEGylation of the liposome surface.
What is PEGylation
Charged lipids that repel opsonins in the blood therby acting as a stealth inducer. Allows liposome to travel the circulation for longer = More likely t reach target tissue
What determines clearance
Particle size. 6-8nm < renally cleared. Anthing larger is opsonised and MPS depositioned. If PEGylated = Hepatically cleared via bile and faeces
Describe the EPR effect
ENHANCED PERMEATION
* Tumour blood vessels are distorted & degraded due to irratic angiogenesis
* Results in leaky vascilature = Drug is more likely to permeate tumour endothelial layer
ENHANCED RETENTION
* Lymphatic system breakdown = No drainage = Accumulation of drug particles = More therapeutic
Benefit of using nanomedicine over small drug molecules
Small drug molecules are rapidly cleared = Short/limited therapeutic effect
also due to size, permeate into various tissue (more side effects)
Nanomedicine»_space; liposomes = larger = not eliminated rapidly + encapsulated + protected = less S/Es, longer therapeutic effect
Abraxane
- Albumin-bound paclitaxel
- Used in breast cancer
- Not liposomal
- Benefit: GP60-mediated transcytosis of albumin (natural transport)
- Non-antigenic
