Drug discovery Flashcards
What is High throughput screening (HTS)?
A method that involves using a biological assay to identify mechanisms of action without knowing the structure.Puts different structures with the drug target and uses an assay to test if novel molecules bind to the target
What is a compound library
A collection of structures that can be used in High throughput screening. A good library is full of representative compounds (not just series molecules), and lead like (follow the rule of 5)
What is the Rule of 5
Desirable properties for an active drug:- Small molecular weight (<10)
What is the process of rational drug design
Generate a model of the target receptor/enzyme.Use this to build the drug to fit the gap.However, doesn’t always work because proteins are flexible, and this doesn’t account for induced fits
Why is the HERG channel important in drug design?
Drugs that block the HERG channel can cause ‘Torsades de Pointe’, a drug induced arrhythmia. This can cause death by ventricular fibrillation.
How was the drug ‘Maraviroc’ developed?
It is a GPCR (CCR5) antagonist (Go/Gi coupled). CCR5 cell line used with a displacement assay to find a suitable molecule. First molecule was an agonist, so structure changed so drug was viable with no side-effects.Improved structure was sent to other drug companies to test against their compound libraries, and was deemed safe.Tested in animals, and gave good results. TAH DAH!
What are the stages involved in drug discovery
Target discoveryLead discoveryLead optimisationPreclinical development
What are the stages involved in drug development
Preclinical/clinical development.RegistrationMarketing and sales
What are the advantages of fragment screening?
Smaller libraries cover large chemical spacePotential to produce better fitting compounds
What are the disadvantages of fragment screening?
Crystalline structure requiredSpecific/specialised assay technology used
Give some examples of screening assays used in HTS
Radioligand binding assaysAlphascreen assayFunctional cell based assay (using calcium sensitive dyes)Beta-arrestin assay
What is the role of DMPK in drug discovery
Potential drugs are selected with DMPK properties appropriate to the intended drug target
What does DMPK stand for
Drug Metabolism and PharmacoKinetics (DMPK)
What are the most commonly targeted molecules
GPCRsLigand gated ion channelsNuclear receptorsEC2 transferasesIon channels
What is fragment screening
Screen smaller fragments of the target to try and build up efficient leads (potency not important). Can add together to make a potent drug.
How does a functional cell based assay work (calcium sensitive dyes)
Fluo3 fluoresces when bound to calciumFluo3 loaded into cells GPCR (linked to Gq protein) activated. Causes calcium release. Measurable through fluorescence screen.
How does a beta arrestin assay work
Complementation assay.N-terminus of GPCR is mutated. When beta-arrestin binds, a substrate can cause a chemiluminescent signal.Specialist cell required.
What does the process of highthroughput screening involve
Test compound libraryRetest positives (to weed out false positives)Assess responses at different concentrationsPurify compounds and assessTAH DAH! confirmed hit compounds
What is lead optimisation
Transforming a biologically active compound into a clinical candidate (drug). Involves optimising good bits, confirming activity in model organism and reducing side effects
What are the 4 phases of lead optimisation
1a - activity/solubility/selectivity1b - in vitro ADME2 - in vivo ADME/activity3 - safety
What is the Caco-2 assay used for
Specific cell line that acts like the gut lining. Shows if a specific drug can travel through the GI tract (tests absorption)
How is drug metabolism tested in vitro (model)
Liver microsomes (contains phase 1 and 2 enzymes; requires co-factor supplements)Liver hepatocytes (expensive)
