L10: Biological drugs Flashcards
what are biologicals?
Biologicals: drugs produced in or extracted from a biological source
Also known as biopharmaceuticals
Sources:
human, animal, fungi, bacteria, plant
Biologicals can be: (recombinant) proteins, nucleic acids (gene therapy) or living cells
examples: pembrolzimab, semaglutide, adalimumab, nivolumab etc.
variolation?
first use of biologicals- variolation
Smallpox
400.000 deaths/year in 18th century Europe
ariolation
First described in China in the 10th century!
Inserting powdered scabs of smallpox infected individuals into superficial scratches of the skin
Smallpox eradicated in 1980
early biologicals
passive immunisation
Earlu biologicals- passive immunity. Exposed healthy rabbits to dipertheia toxoid and creates a resistent rabbit. Took the serum from this rabbit introduced to another healthy rabbit and this is now protected from virulent listeria. Now know there were antibodies in serum directed against diperthia toxoid that provides this protection.
Healthy individuals get passive immunity.
Take horse or cow serum and transfer to healthy individuals
recombiant proteins
the first industrial scale biologicals
Proteins isolated from tissue or produced in vitro can be used as drugs when injected
Mechanism of action:
- Substitute function of protein that is not there or not functioning well
Examples:
Insulin: produced by beta cells of the islets of langerhans in the pancreas. Hormone that regulates blood glucose levels. Identified by banting and best (1920-1921).
First diabetic patient treated with ox-pancreas extract in 1922- allergic reaction due to impurity
cow/pig insulin used as treatment for type 1 diabtes melitus until 1982
Up until ear;y 19080s where it was replaced with recombinant insulin.
Extracting proteins from animal has intrinsic risk that it is seen as foreign creating allergic reactions.
Erythropoietin
Blood factors
Interferons
Growth Factors
recombiant insulin
Recombinant technology- isolate gene of protein you want to produce and insert into an expression plasmid- a dna sequence containing the cues that the cell system needs to start producing the protein. The plasmid can be introduced into mamlian, insulin, yeast or prokaryotic cells.
So bacteria and depending on the complexity of your protein you mau need to use something mammalian to ensure it folds and has the right post-translational modifications? Can produce alot more protein in prokaryotic systems and yeast systems than you would with mammalian cells so both ahve advantages and disadvantages. End up with protein with same amino acid sequence as what is missing in the patient. Easy to isolate protein if you have cell culture or bacterial culture? Increased purity as it is the human protein, less immunogenicity and less expensive than getting protein otu of cows or pigs.
recombiant proteins can be modified
Very easy to introduce favourable mutations in recombinant proteins
Development of insulin analogues
Lispro (Humalog) does not dimerise, more easily absorbed -> Fast acting
Glargine (Lantus) forms aggregates -> long acting
Recombinant proteins can be modified: insulin has a response time of around 5-6 years from administration to peak activity. If someone has high glucose and you want something that works quickly, list pro? One lysine changed for proline insulin doesnt dimerise Makes it mor eeasy to absorb. If someone has type 1 diabetes rather than having to inject insulin over and over during the day, can modify insulin for a slow release variant. Glargine- aspergine? Replaced by aregnine so form aggregates rather than dimerising making absorption slow. Additional advantage of the recombinant technology is the ability to modify proteins to have more favourable pharmacology characteristics.
blood factors
X-linked recessive mutations in Factor VIII or IX cause haemophilia
Blood does not clot
mutation ina certain blood clotting factor msotly factor 8 or factor 9 causing haemophillia. a very rare genetic related bleeding disorder.
Treated with clotting factors purified from human plasma since 1971
Replaced by recombinant form in 1984
but purifying proteins from human sources can have adverse effects.
contamination.
many got infected.
Plasma of up to 60,000 paid donors pooled together (including drug addicts, inmates)
Contaminated with HIV and Hepatitis C
1,200 deaths in UK
why are recombiant proteins generally better than those purified from a human/animal source?
cheaper, safer, opportunity to modify
antibodies
antibodies specifically bind foreign molecules
Antibodies produced as part of the adaptive immune response
Variable domain specifically binds to foreign molecules (antigen)
Produced by B lymphocyte (B cell)
Each B cell produces an antibody with different antigen binding domain
When B cells encounter antigen it will produce soluble antibodies
development of monoclonal antibodies?
isolate your protein and if you inject antigen into mouse, immune system sees it as foreign, starts generating antibodies aainst the protein antigen you just injected.
if for drug target: inject target, mouse generates b cells with receptors for this antigen, isolate these, fuse them in a cell type that is specialised in producing antibodies.
fromm myeloma- easier to make a cancer cell line from normal cells
get a cell line which produce the antibody against protein of interest
isolate from supernatant
gives you monoclonal antibody.
