Lecture 5: Preclinical studies Flashcards
Pre-clinical ‘proof of principle’
- lead optimisation (dozens of compounds)
- Candidate seeking
- preclinical development
preclinical drug development
Vital to gather as much safety and efficacy data at this stage to support future regulatory submissions
Aims of preclinical drug development
Assess potential therapeutic effects of drug candidate in relevant organisms
Gather sufficient preclinical data on the drug to evaluate safety of drug candidate for human use
To determine if drug candidate has potential to ever be developed as a pharmaceutical for human use
- not just to do with safety and efficacy, but also manufacturing etc
Who does preclinical drug development?
Big Pharmaceutical companies
* Traditionally done in-house
* Increasingly being out-sourced to preclinical contract research organisations (CRO’s)
Larger biotechnology organisations
* Some done in-house
* Mainly out-sourced
Smaller biotechnology organisations and Universities
* Little done in-house
* Primarily out-sourced
Identifying a lead candidate series
- Preclinical profiling begins when a lead compound(s) has been discovered.
- Assessing efficacy in early animal models
- Identifying signs of potential off-target or toxic effects.
- Early PK profiling (to compare with in vivo efficacy)
4 Primary areas of preclinical testing
Efficacy testing
- How does the drug work?
- How effective is the drug?
- Cell based assays
- Animal models of human disease
ADME
- What does the body do to the drug?
- What is the most effective way to deliver it?
- Relevant animal models
Toxicology
- Is the drug safe?
- Are there any contraindications?
- Primarily animal testing
- In vitro and in silico approaches
Pharmaceutics
- Is drug manufacture feasible and reliable?
- Physicochemical properties
- Formulation studies
Efficacy testing
How does the drug work?
How effective is the drug?
Cell based assays
Animal models of human disease
“Proof of concept” studies in animal models of disease
In vitro tests
In vivo models (typically rodents)
what does in vitro (?) testing look out for
- binding affinity or potency and efficacy
- high selectivity
- functional cellular assays:
(- enzyme inhibition - inflammatory mediators
- neuronal cell death )
in vivo testing 4 outcome measures
typically performed on rodents
- make sure you measure key outcomes relevant to disease pathology
- make sure its testing in a relevant animal model
- determine if a beneficial effect is observed
- is effect seen at a dose realistic for humans?
ADME
Pharmacokinetics (pk) = sum of ADME process = what happens to the drug inside the body
Adsorption: movement of drug into bloodstream
Distribution: tissue distribution from site of absorption
Metabolism: biotransformation into more polar forms (hydrolysis, conjugation, oxidation)
Excretion: excretion of active drug and metabolites
most ADME usually performed by LC-MS (liquid chromatography mass spectrometry)
tissue distribution
at end of trial kill animal, collect tissue and look at tissue distribution
PK/PD relationship
relationship between pharmacokinetics and pharmacodynamics
= effect over time
5 types of toxicity testing
- Acute toxicity
- Repeat-dose toxicity
- Carcinogenicity
- Genetic Toxicity
- Reproductive toxicity
aim of toxicity testing
- identify safe starting dose and subsequent dose escalation scheme in humans
- identify potential organ system toxicities and whether such toxicities are reversible
- identify safety parameters for clinical monitoring
Acute toxicity studies: design and endpoints
Design:
1. at least 2 species (both sexes)
2. 2 routes of administration (Iv and intended route)
3. emphasis on signs of toxicity and mode of death rather than LD50
4. 3-5 rodents per sex per dose
What to look out for:
1. gross signs of toxicity (death etc)
2. changes in behaviours (hyperactivity, aggression)
3. changes in fur, skin, mucous membranes
4. observing tremors, salivation, sleep etc
5. weight monitored
repeat-dose toxicity studies design and endpoints
Design:
1. at least 2 species
2. 3 dose levels + control group
3. 10-15 rats per sex, 4-6 dogs/monkeys
4. route of ad = dependent on expected human exposure
5. duration: “”
What to look out for:
1. general behaviour, weight, food consumption
2. eye examination
3. telemtry: heart rate, blood pressure
4. haematology
5. urine analysis
6. post-mortem examination
ICH guidelines on preclinical studies
Duration = minimum duration in rodent and = in non-rodents
look at liver, lungs and kidneys
carcinogenicity testing: about
goal: determine capability of drug to cause cancer
genotoxic = direct interaction with DNA
non-genotoxic = indirect
required when maximum duration of continuous drug exposure is >6 months
carcinogenicity testing design and endpoints
Design:
- aim to identify tumour-causing potential of a drug
- route as intended on humans
- administered to animals (usually rats) for at least 6 months
endpoints:
- may do it in another species on use another model to test
genotoxicity testing design and endpoints
Design:
Testing Schedule 1:
- Ames test
- Cytogenetic testing for chromosomal damage
- in vivo micronucleus assay
Testing Schedule 2
- Ames test
-in vivo assessment of genotoxicity with 2 tissues
Monitoring and endpoints:
- if negative for genotoxicity = usually enough evidence to believe it
- if positive for genotoxicity = further testing required
Reproductive toxicity studies: design and endpoints
Design:
- typically use rats
- route as intended
- at least 3 dosage levels used
- control groups
- females: hormonal cycles, pregnancy and embryo development
- males: reproductive organs
Endpoints:
- all stages of development measured from conception to sexual maturity
5 questions of toxicology issue management
- what is the safety margin
- is the toxicity reversible
- is there a biomarker
- what is the mechanism
- what is the relevance of the finding to humans
why do whole animal studies provide better predictions of the pharmacological parameters and properties of
new drugs
- Tissue distribution
- Drug effects in whole organism
- Long term effects - carcinogenicity and fibrosis
- Pharmacokinetics
- Blood brain barrier penetration
pharmaceutics aim and types of studies
aim: Determine if the drug candidates have suitable physical, chemical & biological properties
to become a medicine for human use
studies:
* Physicochemical profiling and characterization
* Preliminary formulation development suitable for efficacy and toxicology studies
* Dissolution testing - standard paddle apparatus
* Stability testing - controlled temperature and humidity for extended periods
* Assessment of particle size and any modifications
FDA requirements
- New Drug Applications (NDA) and Investigational New Drug (IND) submissions
- Efficacy and potency data for the drug
- Safety profile of the drug – Toxicology and Pharmacology data package
- Manufacturing information - composition, stability and excipients
- Clinical protocols if studies are to be done in humans
- Investigator information and human research ethics approvals
the 5R framework
- The right target
- the right tissue
- the right safety
- the right patient
- the right commercial potential
Use of acute toxicity study results and data package
- Informs likely effects of acute over dosage in humans
- Identifies potential target organs for toxicity, and
- Identify parameters for monitoring in future clinical evaluation
- Useful for the design of repeat-dose toxicity studies (eg selection of
doses)
