TOPIC 6: Pre-clinical testing: safety Flashcards
ICH guidelines
- Quality: Pivotal milestones such as the conduct of stability testing, defining of relevant thresholds for impurities. Conducted under GMP.
- Safety: To uncover potential risks such as carcinogenicity, genotoxicity and reproductive toxicity
Dose Ranging study
- Conducted on two or more species of rodents
- At the end of the experiment subjects are euthanized, and autopsied to determine if any organ systems are grossly affected
- Gives an idea of the NTEL
- Single dose tox or escalation protocol
Order of exploratory studies
dose ranging –> Detailed single dose tox –> multiple dose -ranging study (ALL NON-GLP)
Single dose toxicity
- Single dose given to each subject (over a large range i.e. 10, 100, 1000 mg/kg)
- Subjects observed over 14 days for obvious signs of toxicity
- Dose preferably administered in intended route of administration formulation previously shown to be well absorbed etc…
Dose escalation protocol
- Each animal is treated with an increasing dose every 2 days until signs of toxicity appear or 2000 mg/kg is reached.
Detailed single dose toxicity study
- Conducted on 2 or more species
- 4-5 doses tested, ranging from a dose in the expected therapeutic window to doses well above the NTEL
- Regular assessment of animals over a 2 week period for signs of obvious toxicity
- After 2 weeks animals autopsied
Multiple dose tanging toxicity study
- Drug given once or twice daily for two weeks and subjects autopsied
- Gives preliminary information about chronic toxicity
regulatory toxicity
GLP
Conducted under ICH guidelines to seek approval for (a) Human administration for the first time (ind) and (b) permission to sell and market the drug.
Permission to administer to man
- 28 day repeat dose and toxicity
- Safety pharmacology
- Genotox (in viv and in vit)
- Reproductive tox -
Permission to market
3-12 month chronic tox study
- 18-24 month carcinogenicity
- Reproductive toxicity
28 day repeat dose and toxicity
- Conducted on rats
- Used to determine NOAEL
- Three test groups and 1 control group
- Highest dose should aim to produce severe toxicity but not death or severe suffering
- Animals autopsied
- Can be combined with reproductive/developmental toxicity test but the study would then be longer than 28 days
Safety pharmacology:
- Core battery tests: investigate the effects of the substance on vital functions. Focuses on acute CV, CNS and RS effects
- Follow up tests: Required if core-battery tests reveal effects whose mechanisms need to be determined
- Supplementary tests: If known chemistry or pharmacology of a compound gives any reason to suggest it would produce side effects
QT Elongation
In vitro: Evaluates effects on flow through Ikr channels. (hERG channel inhibition)
In vivo: Measures for QT interval elongation in conscious animals (not rodents
Genotoxicity
- Ames test: mutagenicity in bacteria
- In vitro test for chromosomal abnormalities in mammalian cells OR a mouse lymphoma TK cell assay
- In vivo test for chromosomal damage in rodent haemopoietic cells
If one or more tests provers positive further studies are needed to assess the magnitude of the risk
Chronic toxicology
Conducted to test for toxicology after steady state has been achieved
- Subjects: 1 rodent and 1 non rodent species
- Dose range: Clearly toxic, therapeutic level and one in between
- Includes a recovery group where animals are allowed 2-4 weeks to recover in order to assess the reversibility of the changes
Carcinogenicity testing
- Required for NDA but not IND
- Take 2 years and conducted in parallel with clinical trials
Design: - 1 long term test in rodents (rats), 1 other in vivo test such as transgenic mouse models with high sensitivity to carcinogens or long term test in a second rodent species
