L17: VY Lecture 4

Question 1

What is GLP for?

Answer 1

Research data submitted is documented thoroughly to the point that any scientist skilled in the art can follow the documentation to replicate the results.
The level of detailed documentation required is very substantial

Question 2

When is GLP required?

Answer 2

For studies determining safety.

Question 3

When is GLP not required?

Answer 3

• efficacy studies
• PK studies
• drug interaction studies

Question 4

What are the challenges associated with GLP?

Answer 4

• inflexibility (every step must be decided and documented in advance, and each study must then be scheduled)
• takes a lot more time to execute GLP studies
• cost is a lot higher
• most scientists do not have experience working with GLP

Question 5

What is a business opportunity associated with GLP?

Answer 5

• CRO (contract research organization) –> to conduct pre clinical research
• companies outsource preclinical studies to CRO bc more cost effective

Question 6

What are the advantages and disadvantages of in vitro methods in preclinical research?

Answer 6

adv:
- cheaper
- efficient
- availability of human-based cell models like iPSC
- suitable for in depth mechanistic analysis

disadv:
- unreliable for predicting pharmacological and toxicological responses in intact animals

Question 7

What is an example of an in vitro permeability model?

Answer 7

Caco-2 (human colon adenocarcinoma cells)

Question 8

What is Caco-2?

Answer 8

Caco-2 cells act like small intestinal enterocytes
Add test agent on one side of monolayer and permeability is assessed by analyzing concentration on the other side of the monolayer using LC/MS/MS.

• Caco-2 permeability assay considered gold standard for in vitro prediction of in vivo human intestinal bioavailability of orally administered drugs

Question 9

What are some in vitro methods for metabolism?

Answer 9

Metabolic stability studies:

• hepatocytes
• microsomes
• plasma, tissues

Metabolite identification

Metabolic profiling eg phase 1 or 2 enzymes etc

Question 10

What are some in vitro methods for toxicology?

Answer 10

• mammalian cytotoxicity
• mitochondrial toxicity
• reactive metabolites
• hemolysis
• phototoxicity

Question 11

How do we choose animals for preclinical research?

Answer 11

• need minimum of two species
• canine (dogs) may not be good models for solid oral dosage forms bc carnivore intestine is under developed compared to omnivore
• rodents cannot be models for oral antibiotics bc the resulting alteration of intestinal flora causes significant adverse effects

Question 12

What is no observable effect level (NOEL) of drug used for?

Answer 12

used to determine initial phase 1 clinical trial dosage level

Question 13

How to reduce variability in animals?

Answer 13

use in bred mice

Question 14

Why do we do preclinical animal studies?

Answer 14

• data from animal can be extrapolated to humans

- supra therapeutic doses relevant for illuminating toxicities in human (estimate therapeutic window)

Question 15

How to do acute toxicity testing?

Answer 15

Modified LD50 test eg maximal non lethal dose

Question 16

What is chronic toxicity testing?

Answer 16

Repeat administration

Question 17

What are some short term carcinogenicity assays?

Answer 17

Pereira model:
- remove part of liver, subject to test substance to see if initiator -> give phenobarbital in drinking water

Ito model:
- subject liver to DEN (diethyl nitrosamine) as initiator -> subject to test substance to see if it can promote tumour growth

Question 18

What is reproductive toxicology study?

Answer 18

• fertility and embryotoxicity study
• teratogenicity study
• peri and post natal study

Question 19

How can transgenic animals be used in preclinical research?

Answer 19

p53 +/- mice -> more sensitive to carcinogen

Question 20

How can humanized animals be used in preclinical research?

Answer 20

Replace gene encoding mouse xenobiotic sensor with gene encoding human xenobiotic sensor -> better predict human response