Consumer Healthcare Flashcards
Define a drug [ FDA]
The FD&C Act defines drugs, in part, by their intended use, as “articles intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease” and “articles (other than food) intended to affect the structure or any function of the body of man or other animals” [FD&C Act, sec. 201(g)(1)].
Outline the drug discovery process.
XO Read the answer here and re-write what you remember
- Pharmaceutical companies evaluate the future direction and R&D activities on the basis of medical needs, market size, government policies and regulations, patent protection, and key competencies.
- Most diseases, apart from trauma and infections, have origins in the genes or the proteins associated with them, as well as the biochemical pathways and networks.
- Current approach to drug discovery starts with the identification of target or targets that cause or lead to disease.
- Microarray is a technology used to study gene interactions and control of biochemical pathways.
- Target validation is necessary to confirm the validity of a target as a representative of a disease model before too much investment and time is expended on it.
- Once targets are validated, potential drug candidates are designed to bind to and interact with these targets.
- The main drug targets are enzymes and receptors that are found on the cell surface or reside within the intracellular matrix.
- Drugs interact with enzymes and receptors mainly through van der Waals forces and hydrogen bonding; they need the correct shapes and sizes to fit into the active sites of the targets.
- Drugs work in two ways: as agonists and antagonists. Agonists activate the receptors whereas antagonists deactivate, block, or inhibit the receptors.
- After binding of drug and receptor, a cascade of signal transductions occurs
Give detail difference between rational and irrational drug discovery approach?
Irrational approach involves the collection of natural products that have sufficient biodiversity with different and diverse chemical compositions so that many potential variations of chemical compositions and structures can be extracted for testing. The next step is the screening of thousand of these compounds to find lead compounds or potential drug molecules that bind with the receptor and modulate disease pathways. The compound libraries are screened and this can be done using HTS or ultra-HTS. Following the ‘hits’ lead compounds are purified using chromatographic techniques and their chemical composition are identified via spectroscopic and chemical means (X-ray crystallography and NMR).
Whereas rational approach involves drug discovery based on knowledge of the 3D structure and the amino acid of the chosen receptor that would reveal potential binding sites for drug molecules. Structural activity relationship could be developed and the pharmacophore elucidated. The standard technique for 3D structural determination involves X-ray crystallography and NMR spectroscopy. Computational chemistry (in silico) methods and mining through bioinformatics is another means. Once modelled drug is elucidated it can be synthesised using combinatorial chemistry and screened against HTS system.
Both approaches end up undergoing Drug Metabolism and Pharmacokinetic studies to optimise the lead compound.
Give an example of drug developed from irrational approach?
Enalapril from venom of south American snake.
What is HTS
Robotic system that delivers accurate and fast liquid samples into miniaturised well plate (384-/ 1536-) that has the assay reagent in so that the screened compound show signal if it binds with desired drug target.
Explain how computational chemistry works and what rule can be used to better increase selectivity of good lead compounds.
Lipinski’s rule states that, in general, an orally active drug has no more than one violation of the following criteria: No more than 5 hydrogen bond donors (the total number
of nitrogen–hydrogen and oxygen–hydrogen bonds), No more than 10 hydrogen bond acceptors (all nitrogen or oxygen atoms), A molecular mass less than 500 daltons, An octanol-water partition coefficient log P not greater than 5.
Using this rule a ligand library can be developed and computational docking, ranking or screening of the compound can be conducted.
What is combinatorial chemistry?
Combinatorial Chemistry generates a multitude of chemically related(”congeneric”) compounds, so-called combinatorial libraries.
How does a combinatorial chemistry work: Solid phase synthesis…
Resin is the bead at the end of the reaction that will be ‘washed off’, It is an insoluble polymeric inert support that can swell in excess reagent and removed in purification step. Linker/anchor: covalently bound to the resin and it has the starting material attached to the other end. Linker is detachable from starting material. For example amines and this can be then reacted with carboxylic acid which produces amide. Unreacted carboxylate us removed and then amides are released from solid support using UV light for example.
What is established in the pre-clinical testing?
Pharmacokinetics, Pharmacodynamics and toxicology testing is carried out and it is data submitted to the regulatory agency.
Give an example of pre-clinical testing in vitro, in vivo and toxicology testing….
In vitro test to assess drug metabolic stability is liver microsomal stability assay with NADPH to assess Phase I oxidations by CYP and FMO. High-throughput (HTP) assay provides clearance (mL/min/g liver). (Other examples on slide 55 MDD).
In vivo would be assessing the pharmacokinetic parameters in monkey to calculate volume distribution and the drug clearance.
Toxicology test involves carrying out acute testing, sub-chronic and chronic to establish the safety profile of the drug. Gross clinical signs of toxicity such as appearance, body weight changes in animals and gross pathology such as organ weight changes: hepatomegaly, enlargement of the spleen.
What does medicine development involve?
Formulation of the drug product, which includes active pharmaceutical ingredients and excipients, into a final form suitable to be administered to patients.
Study of drug delivery systems to improve the effective presentation of the drug to patients for enhancing certain characteristics and improving patient compliance.
Why are excipients added to the formulation?
Control the release of drug substance in the body
Improve the half-life of the drug substance (refer to Exhibit 4.9)
Improve the assimilation process and bioavailability
Enhance drug dissolution as disintegration promoters
Extend the stability and shelf-life of the drug as antioxidants or preservatives
Improve flow properties of the bulk powder.
Mask unpleasant taste of active ingredients.
Give examples of the use of excipients in oro-dispersible dosage form: improved disintegration?
Microcrystalline cellulose (MCC) is excipient used to improve disintegration profile of medicine.
Give examples of the use of excipients in oro-dispersible dosage form: lubricant?
Magnesium stearate will be added after granule formation as lubricant to prevent adherence to tablet press.
Give examples of the use of excipients in oro-dispersible dosage form: surfactant and taste-masking agent?
Polysorbates 80 is non-ionic surfactant added to function as a dispersing agent.
Cyclodextrin would function as a taste masking agent
Before clinical testing what must the regulatory agency be given?
Documents must be submitted through IRAS system containing the covering letter, manufacturing authorisation, investigation medicinal product dossier and final protocol in English.
The dossier contains pre-clinical testing information (if not provided in the investigator brochure).
Medicinal product must be manufactured to GMP standard.
What are the two checks the regulatory department do?
The regulatory agency have ethics committee, then also a review of the science involved in with the IMP. The ethics committee assess the studies rights, safety, dignity and well-being of research participants, whilst facilitating and promoting ethical research.
What is involved in Phase 1 study (recall, rewrite what you have just seen)…
What is involved in Phase 2 study (recall, rewrite what you have just seen)…
What is involved in Phase 3 study (recall, rewrite what you have just seen)…
What does SEQ stand for?
Safety Efficacy and Quality.
Usually Two large Phase III trial are required.
a. True
b. False
True
What is involved in Phase IV studies…