Bioassays in drug discovery Flashcards
what are the main stages in drug development
- selection of disease target
- discovery of lead molecule by bioassay
- preclinical studies
- clinical studies
why are bioassays needed
- to predict some type of therapeutic potential, either directly or by analogy, of test compounds
- typically conducted to measure the effects of a substance on a living organism
define bioassay
any qualitative or quantitative analysis of a substance that uses a living system
give examples of bioassays
- whole animals
- isolated organs
- lower organisms (bacteria)
- cultured cells
- isolated sub cellular systems (enzymes)
what are in vitro/ex vivo studies used for
- screening
- cell viability
- drug drug interaction studies
- metabolite identification/elucidation
- plasma protein binding
- genotoxicity
what is involved in screening assays
- high throughput in vitro assay
- specific assay
- need to have a low cost and high specificity
what are screening assays used for
used in in vitro enzyme/receptor assays to test specificity in plate based format
give an example of assays to test for new drugs
cell growth for anti cancer medications
what needs to be considered in terms of pharmacodynamics of bioassays
- does the drug affect the target at effective concentrations that can be reached clinically
- does the drug modify the disease process in an animal model
how can drug effectiveness be tested
- test leading compounds
- ex vivo on isolated tissues
- in vivo in animal models of the disease to determine If it has the desired effect
how can pharmacokinetics be measured using bioassays
only very basic measurements can be made using bioassays
- full animal studies are required to get the full pharmacokinetic profile for ADME
What are drug drug interaction studies
- using pooled human liver microsomes or other in vitro metabolism models
- determine the effects of the new compound on metabolising enzyme activity and potential interactions/side effects
what is involved in metabolite identification/elucidation
- using liver microsomes/cells
- using LC-MS to identify possible metabolites
- synthesise metabolites to test for toxicity and efficacy
what is involved in plasma protein binding study
- using human and other species plasma
- use equilibrium dialysis or ultrafiltration
- determines the stability of drug in plasma
what toxicology studies can be conducted
- safety pharmacology
- cell viability
- cardiovascular toxicity
- genotoxicity
what toxicology studies can be conducted
- safety pharmacology
- cell viability
- cardiovascular toxicity
- genotoxicity
what is safety pharmacology
studying the potential undesirable pharmacodynamic effects of a substance
what is used in cell viability
- MTT assays
- LDH assays
- apoptosis and necrosis measurements
what is involved in testing cardiovascular toxicity
- all drugs require hERG testing
- if its ability to conduct electrical current across the cell membrane is inhibited or compromised, long QT syndrome may occur
what is hERG
a potassium ion channel in the heart
what is used in genetoxicity
- bacterial reverse mutation test- use bacteria which have mutations in genes involved in histidine synthesis
- need histidine to grow
- if they grow without histidine, indicates mutations induced by drug - COMET assay- single cell gel electrophoresis to detect DNA damage
what are ex vivo studies
test compounds on tissue taken from a living organism
- can be used to test effectiveness of a drug and identify potential side effects
what are in vivo studies
testing which takes place in a living organism
- eg. animal models
- can be used to identify toxicity in key systems such as cardiovascular system, CNS, respiratory system
what in vivo tests are conducted
- biochemical- blood levels of creatinine, ALT
- histopathology
- physiological observations- breathing, heart rate
- observation of behaviour when drug is administered
