Lecture 9

Question 1

Define active, hits and leads

Answer 1

Active- Raw output from HTS and is in the from of IC50 from dose response using HTS assay on sample solution of DMSO.

Hits- defined in term of profile that confirm chemical structure and show biological activity as well as having good physical chemistry data, drug metabolism and pharmacokinetics measurement

Leads- described in term of target profile of chemical and biological data

Question 2

How are the ways to find chemical starting points?

Answer 2

Natural product- a constant source of new hits and drugs
HTS
Fragment based drug discovery
Virtual screening
Fast-follower approach

Question 3

Describe fragment based approach

Answer 3

This approach involve screening of low MWt molecules to look for low affinity hits for further opmisation. Screening is done via NMR, X-ray and SPA screening and optimisation relies on X-ray crystallography.
Type of approaches:
- linking fragment
-growing fragment

Question 4

Decribe virtual screening approach

Answer 4

Look for common chemical features among the actives and build a pharmacophore model based on them. Then can either:
- Look for new compounds based on the pharmacophore model through commercial databases or legacy compounds. This is known as knowledge based drug discovery
- Look for new compounds based on their ability to bind to receptor in the 3D receptor model. This is known as structured based drug design.

The succesfull compounds will be hits.

Question 5

Describe fast follower approach

Answer 5

• Design new compounds as hit based on existing active drug with similar chemical structure at a clinically validated receptor.
• Doesn’t require finding out whether unknown compounds bind to a target receptor
• Benefits of this approach is that the compound will have high selectivity, safety, PK, phycial properties, etc.

Question 6

What is a biological assay?

Answer 6

• An assay that can detect and measure biological activity of the molecules in a relevant biological system
• They need to be robust and reproducible

Question 7

Do we need to revalidate the activity of the initial hits using second assay?

Answer 7

Yes

Question 8

Describe enzymatic / biochemical assay

Answer 8

The assay monitor the formation of the product of an enzymatic assay. The enzyme is isolated and purified and the assay measures either its inhibition or activation by detecting the amount of product formed.

Question 9

Describe functional assay and give an example of this assay

Answer 9

Assay that measure the downstream effects of a binding event e.g. changes in cAMP, transcription event, protein level and Ca2+ mobilisation
An example of this assay is a Ca2+ assay

Question 10

Describe a phenotypic assay

Answer 10

Unlike targed-based drug discovery, phenotypic screening does not rely on knowing the identity of a sepcific drug target or its hypothetical role in disease. A key benefit of this approach is its ability to capture complex biological mechanism