D. PROTEIN DRUG DELIVERY AND CHALLENGES

Question 1

what are biopharmaceuticals

Answer 1

protein drugs

Question 2

what are the advantages of protein drugs

Answer 2

highly specific and very effective

Question 3

how do biologic drugs compare to conventional drugs

Answer 3

bigger and more complex
ie - Insulin and Pembrolizumab vs Aspirin and Crestor

Question 4

how does IgM act

Answer 4

like a small particle, there is is no transit through basement membrane and hence little extravasation

Question 5

what is the shape of proteins

Answer 5

• globular and packed
• specified by amino acid sequence of polypeptide chain
• flexible polypeptide chain folds into a compact conformation
• side chains help determine conformation in an aqueous solution
• relationship between molecular weight and size depends on shape

Question 6

what challenges are caused by intrinsic physicochemical properties of proteins

Answer 6

• absorption: proteins are large and hydrophilic
• extra-vascular access is difficult as the drug mightn’t be able to reach target and hence will circulate in blood (phospholipid bilayer is tight)
• poor stability as they are easily denatured
• purity and characterisation of recombinant products
• pharmacological action is complex

Question 7

what challenges are caused by anatomical and physiological barriers in human body

Answer 7

low MW drugs reach sites of action by diffusion and partition which isn’t possible for proteins
ie - proteins are large and shapely so can’t easily pass through skin

Question 8

method of delivery proteins to skin

Answer 8

micro knife technique where small needles deliver proteins by puncturing barrier

Question 9

how long can biopharmaceutical manufacturing take

Answer 9

up to 90 days

Question 10

what is process of biopharmaceutical manufacturing

Answer 10

1. collect cells and raw materials
2. create cell bank
3. small scale cell culture
4. large scale cell culture (DNA recombination)
5. recover product
6. filter product (and purify)
7. formulation
8. pool banks
9. sterilise and fill vials
10. lyophilize
11. add lids
12. inspect product
13. label product
14. package product

Question 11

how many cells are required for 1 dose of medicine

Answer 11

1000 billion cells

Question 12

what does the amount of protein drug reaching tissues depend on (ie biodistribution)

Answer 12

1. ability of proteins to be transported across endothelium
2. differences in relative blood flow to different tissues ie - lungs vs cartilage
3. rate of excretion by kidneys
4. metabolism

Question 13

how are small molecules removed in the body (peptides, oligonucleotides etc)

Answer 13

by glomerular filtration in glomerulus by passive filtration in kidneys

Question 14

what is the cut off for glomerular filtration

Answer 14

> 8nm don’t pass through ie - antibodies, albumin (7nm)

Question 15

why is albumin not removed

Answer 15

due to charge
(pores are -vely charged and so is albumin and 2 like charges repel and won’t pass through)

Question 16

how does diabetes affect albumin

Answer 16

makes it more positive and therefore it passes through

Question 17

what is the cut off MW for glomerular filtration

Answer 17

60kDa (proteins)
polysaccharides are 40kDa but pass through

Question 18

how are proteins mainly eliminated

Answer 18

• metabolism by clearance receptors in liver on parenchymal cells and they are also on macrophages
  ie - asialoglycoprotein receptor (ASGPR)
• internalisation of galactose then removed for elimination

Question 19

how does clearance occur

Answer 19

• many proteins have carbohydrate residues (ie - glycoproteins)
• terminal sugar residue is sialic acid but sugars below are different
• sugars are recognised when terminal sugar is cleaved off
• ASGPR recognises D-galactose

Question 20

what does the ASGP receptor clear

Answer 20

• hormones eg: erythropoietin, FSH, interferon
• carrier molecules eg: thyroglobulin, caeruloplasmin, transferrin
• protease inhibitors eg: α-1 antitrypsin, α-2 macroglobulin
• immunological eg: IgG and IgG antigen complexes

Question 21

what other important receptors are on liver parenchymal cells

Answer 21

fucose receptor

Question 22

what other important receptors are on macrophages

Answer 22

N-acetylgalactosamine/ mannose receptor

Question 23

what happens once the protein binds to a receptor

Answer 23

endocytosis and lysosomal degradation by enzymes

Question 24

what is the importance of clearance receptors for drug delivery

Answer 24

1. protein drugs may be cleared from circulation by normal homeostatic mechanisms
2. specific receptors could be used to target drugs to the liver ie: receptor takes up certain proteins then metabolises them inside and potentially release a drug you want to deliver to a liver cell

but cytotoxic drugs (anti-cancer) can cause liver toxicity