Biologics Flashcards
Biologics
Class of drugs produced by a living system
Biosimilar
A biological product that is approved based on demonstrating that it is highly similar to an FDA approved product
No clinically meaningful differences in safety and efficacy from reference product
Traditional v. biologic formulations
R&D: test new chemical entities v. replace or supplement natural proteins
Clinical intervention: chemical v. biological
Type: Oral v. larger complex proteins
Stability: room T v. refrigerated
Assay: standard drug testing v. minute amounts in vivo (challenge monitoring therapeutic levels)
Amino acids
20 different amino acids
Native state of proteins
properly folded and/or assembled and is bioactive
Types of folded proteins
primary structure
secondary structure (b pleated sheet and alpha helix)-H bond
tertiary structure
quaternary structure
Peptide and protein stability
Chemical stability
Physical stability
Chemical stability
deamidation
racemization (D to L or vice versa)
hydrolysis
oxidation
disulfide exchange reaction
Physical stability
denaturation
aggregation
precipitation
adsorption
Monoclonal antibody (IgG)
Fab–antigen binding in the top y portions
Fc–effector functions, does the attacking
Physico-chemical characteristics of monoclonal antibodies
N-terminal heterogeneity
AA modifications
fragmentation
oligosaccharides
disulfide bonds
C-terminal heterogeneity
deamidation AA
Asn, Gln
Racemization AAa
Asp
Hydrolysis AA
Asp-X
Oxidation AA
Met, Cys, His, Try, Tyr
Disulfide exchange AA
Cys
Denaturation
protein unfolding from the natural state to a more disordered arrangement
partial or complete
reversible or irreversible
loss of biological activity
–>aggregation
–>precipitation
Things that cause denaturation
heat
pH
ionic strength
surface
surfactant
organic solvent
filtration
freezing/freeze-drying
moisture
shear forces
pH and denaturation
pH below isoelectric point: net positive charge –> repelling of AA and denaturation
pH below isoelectric point: net negative charge –> repelling of AA and denaturation
Protein adsorption
Preferential accumulation of protein at surface
reduces surface tension
Quantity is a few mg/m^2
Minimal at pI–> pH and ionic strength is important
Partly reversible on hydrophilic surfaces
Often irreversible on hydrophobic surfaces
Increases with hydrophobicity of protein/surface
Adsorbed proteins may denature to optimize surface interaction
Aggregation
Formation of abnormal soluble aggregates or peptide or protein
Chemical and/or physical interaction
Reversible or irreversible
high concentration
loss of biological activity
Preciptation
macroscopic equivalent of aggregation
Practical issues handling biologics
Require refrigeration
Extreme temperatures/thawing can denature proteins
Sterility–usuallly no preservative
Excessive agitation can denature proteins
Proper diluent is critical
Proteins may adsorb to plastic/glass
Dosing is based on units of activity v. chemical weight
Proteins usually administered SC or IV
Home admin: transport, storage and patient education
To prevent adsorption
apply a surfactant
PH modifier
Buffering agents
Toxicity agents
Tonicity modifiers
Bulking agent
Sugars and polyols
Amino acids
Polymers and proteins
Wetting and/or solubilization agent
Surfactants
Antioxidant
Antioxidant
Preservatives
Antimicrobial preservatives
Antimicrobial preservatives
Chelating or complexing agent
Chelator preservatives
Stability of recombinant TNF under refrigeration
Over a year protein purity is 99% but potency is 50%
Measured activity of TNF
Is low with just D5W but at expected amounts with D5W + 0.25% human serum albumin
Measured activity of IL-2
Should not be administered with an in-line filter because activity decreases drastically
Expiration dates before v. After reconstitution
Years before reconstitution
30 days after reconstitution (8 hours if no preservative)
Factors for parenteral administration of biologics
Concentration of protein drug
Choice of diluent and additives
Contact surfaces (proteins like to adsorb to plastics)
Immunogenicity
Creation of anti drug antibodies against the biologic
Could also create a cytokine storm
Could cause anaphylaxis
To avoid immunogenicity
Human v. Animal
Contaminants
Formulation (storage of freeze-dried material at room temp
Level of glycosylation
Route of application
Dose
Aggregates (instability or improper reconstitution)
IV administration for biologics
Most common for monoclonal antibodies
Advantages of IV
Large volume can be injected
Control rate of infusion
100% bioavailability
High Cmax
Relatively low patient variability
Disadvantages of IV
Specialized equipment with trained personnel
Longer clinic/office stays
Less patient convenience
SC route advantages
Self-administration
Less invasive
Better patient compliance
Lower cost
SC route disadvantages
Limited injection volume; hyaluronidase
Injection site irritation
Inter patient variability
Injection site differences
Bioavailability <100%
Hylauronidase
Degrades the matrix at the extracellular site to increase the effective volume of SC route
Capillary permeability
Decreases with increasing MW
SC injection routes
Abdomen is higher than the thigh
SC absorption and peak concentration time
The lower the MW the faster the time to perks concentration
Renal clearance and proteins
The larger the molecule, the less clearance (esp if charged)
With renal disease, renal clearance decreases
SC injection results for monoclonal antibodies
Not complete bioavailability
Time to peak is about a week
Terminal half life is about 3 weeks
New delivery systems for biologics
Transdermal
Transnasal
Ophthalmic (eye drops/lenses)
Implantable (depots or pumps)
New oral (CR)
Pulmonary
Targeted biologics delivery
Monoclonal antibodies
Liposomes
Modified cells containing active genes
Antibody-drug conjugates for cancer targeting
ADC binds tumor associated antigen
Enters the cell
Lysosome breaks up ADC in cell
Drug is released in cell and reaches target site
