Drug development and screening

Question 1

What is drug discovery?

Answer 1

Drug discovery can be described as the process of identifying chemical entities that have the potential to become therapeutic agents

Question 2

What are the 5 steps for drug discovery from bench to bedside?

Answer 2

1. Biological question
2. Basic research
3. Drug discovery
4. Drug development
5. Drug delivery

Question 3

What are the 5 drug discovery workflows?

Answer 3

1. Target selection: find a drug target
2. Hit identification: find a molecule that targets what we want
3. Lead discovery: select the most specific molecule for the target
4. Lead optimization: make sure there is no off-target effects
5. Drug development: animal studies and clinical trials

Question 4

What is the difference between forward and reverse approach in drug discovery?

Answer 4

Forward: phenotypic screening => lead compound (gene of interest)
=> target protein identification

Reverse: target protein => small molecule screening
(directed mutagenesis) => phenotype analysis

Question 5

What are the pros and cons for target-based assays (measuring the direct interaction between a compound and a protein)?

Answer 5

Pros:
• usually single step, homogeneous reaction
• readily adaptable for high throughput screening (can screen a lot of compounds)

Cons: 
• restricted to one target (not a biological effect)
• don’t reflect cellular
dependent conditions (availability, toxicity, etc.)

Question 6

What are the pros and cons for cell-based assays (measuring alterations in phenotype)?

Answer 6

Pros: 
• functional data
• phenotypic information 
• open to unknown
mechanism of action

Cons:
• multistep reactions
• not fully controlled reaction conditions
• prone to batch-to-batch variations

Question 7

What can a phenotypic screening measure?

Answer 7

o Cell viability
o Signaling pathway activity
o Protein expression and localization
o Morphological changes 
o Cell cycle
o Cell migration
...

Question 8

How can we measure cell viability assays and when?

Answer 8

How: 
o nuclei count
o metabolism 
o membrane integrity
o apoptosis

When:
o finding anti-proliferative agents
o toxicity testing
o studying rescue effect

Question 9

How can we measure single target assays and when?

Answer 9

How: 
o membrane staining
o RNA staining
o DNA staining
...

When:
o finding mechanisms of action
o targeting a specific pathway/protein

Question 10

When do we measure morphologic assays?

Answer 10

o Finding mechanisms of action

o Targeting a phenotype without knowing the target

Question 11

When do we measure cell cycle assays?

Answer 11

o Finding mechanisms of action involving the cell cycle

o Targeting the cell cycle

Question 12

How can we measure motility assays and when?

Answer 12

How:
o wound healing assay
o nanoparticle phagocyting assay
…

When:
o finding factors affecting cell motility (migration, metastasis, etc.)
o targeting a phenotype without knowing the target

Question 13

What does the Z’ factor validate/evaluate and what does it differentiate?

Answer 13

• The Z’ factor was introduced for validation and evaluation of screening assays
• It accounts for differences between signal and background noise and their respective uncertainties
Goes from 0 (worst) to 1 (best)

Question 14

What are the 3 steps for a typical screening campaign?

Answer 14

1. Primary screening: selected library is tested at single concentration
2. Counter screening: active compounds (hits) are tested for specificity
3. Dose response: IC50 determination