Ion channel drug screening steps Flashcards
1
Q
Drug discovery screening steps
A
Target selection and validationi primary screen secondary screen lead optimisation safety + toxicity efficacy clinical trials
2
Q
What is primary screening?
A
- Determining molecular targets
- How they correlate to disease
- Where are they found in the body?
- Pathways and roles
3
Q
How to do primary/pre-screening
A
- Genetics – sequencing, family traits
- In vitro – cellular models
- Manual patch clamp
- In vivo – animals e.g., mouse
4
Q
Primary screen steps
A
- Large amounts of compound (100k)
- High throughput screening
- Identify active compounds against specified targets
5
Q
How to do primary screening details
A
- Radio-flux assays - Use radioisotopes of key ions – track where they go - sodium, calcium etc
- Voltage/ion sensitive dyes/fluorophores which detect voltage and ion changes
6
Q
Pros of radio flux and dyes
A
- Can do large screening
- High throughput – tests millions of samples rapidly
- Quite cheap
7
Q
CONS of radio-flux and dyes
A
- Radioactive – so careful with handling and waste
- Indirect measure for ion channel activity which can lead to false positives/negatives
- Provide limited qualitative data
- No real-time data/mechanism of action
8
Q
What is secondary screening?
A
About 1-20k compounds
• Put through medium/high throughput screening
• Identify most active compounds against target
• Selectivity screens against similar channels
9
Q
How to do secondary screening?
A
• Automated patch clamp e.g., Qpatch
10
Q
Pros of automated patch clamp
A
- Data rich
- High quality
- Mechanism of action can be determined
11
Q
New changes to screening methods?
A
- Scientists want to do just one big APC screening rather than 1 and 2
- Save time and resources
- Better than doing the whole radioactive bla
12
Q
What is lead optimisation?
A
- Chemically improve the secondary screen approved compounds
- Look at Absorption, distribution, metabolism and excretion
13
Q
What is the Lipinski rule of 5?
A
- Found that most successful drug-like compounds share physical properties
- The best drugs have:
- MWt < 500
- Solubility < 5
- <5 H-bond donors
- < 10 H-bond acceptors
14
Q
Safety and toxicity
A
- Target selectivity over other ion channels
- Ion channel cardiac safety pharmacology
- Therapeutic index – measure safety of drug
- TI = Toxic dose/effective dose
- High TI = bigger window of drug effect
15
Q
Efficacy
A
- Animal models
- Show the efficacy In mouse for example
- Animal to human translation?
