lecture 5 Flashcards
lectures before this one focused on processes in what stage
processes in the early stage of development
lecture 5 focuses on what stage
the preclinical stage of drug discovery
what does preclinical mean
before humans
pre = before
clinical = humans
what are the preclinical test research activities
aka what is tested in preclinical studies
- toxicology
- pharmacodynamics
- pharmacokinetics
- optimisation of drug delivery systems
what is pharmacodynamics
what the drug does to the body
if it goes to the right place
biochemical effect of the drug
what is pharmacokinetics
how the body handles the drug
what the body does to the drug
what is optimisation of drug delivery systems
how the drug will be delivered
why are iterations carried out. why is it repeated
- to reduce toxicity
- to improve pharmacokinetic performance
what is the goal of preclinical drug development
- an optimised compound is found + becomes a potential drug
- its ready for clinical trials
what must the drug respect in order to go from preclinical to clinical trials
it has to follow good GLP
what is GLP
good laboratory practice
what does good laboratory practice ensure
ensures that the proper quality system + ethical considerations are established
what 2 things occur in lead compound optimisation
- structural varient is synthesised on the lead compound
- more than one property is optimised (ADME)
what does synthesising a structural varient on the lead compound do
it optimises its properties to become a drug candidate
what must happen to go from prescription to patient health
ADME
what does ADME stand for
activity
adsorption
metabolism
excretion
toxicity
ADME stands for descriptors that quantify a drug : which are
- entering the body
- moving around the body
- changing within the body
- leaving the body
overtime ADME has diversified according to the
needs of others
what mechanisms is ADME used to describe
- crossing the gut wall
- movement between compartments
- mechanism of metabolism
- excretion / elimination
what are the 2 ADME stages
in vitro ADME.
in vivo ADME
why is in vitro ADME a thing
it uses cell cultures in order to estimate how a new product will react
why is in vivo ADME used
used to validate in vitro ADME
how do cells transport molecules
transcellular
paracellular
what is transcellular transport
active + passive
through the cell membrane
what is paracellular transport
transport between cells
h2o, ions, small solutes, molecules
why is cell transport important
biological targets are usually found in cells
what is drug permeability important in
oral drug absorption
what are oral drug absorption dependent on
its passive permeability
the possibility that a transport protein will uptake the drug
2 assays to study permeability
PAMPA
Caco-2 cell assay
what does PAMPA stand for as an assay of permeability
parallel artificial membrane permeability assays
is PAMPA in vitro or in vivo
in vitro
transcellular transportation
through cell membranes
describe PAMPA permeability assay
test compound in buffer in the DONOR WELL
lipid membrane that mimics a cell membrane
RECEIVER WELL this is where the drug is transported into
what is the goal of PAMPA
to see if the drug is transported across the cell membrane or if it neeeds a transport protein
we can tell
what is the Caco-2 cell assay testing
testing paracellular transport,, using a real cell monolayer to see if the drug can be transported between cells
uses a real cellular model
stages of Caco-2 cell assay
see if the dye passes through the monolayer from the aptical to basolateral chamber
what is an advantage of Caco-2 against pampa
Caco-2 uses a real cell system better as it uses a real. cullular model (cell monolayer)
Papp is the
apparent permeability coefficient
equation for Papp
dQ(conc in basal chamber) /dTime
x 1/Area x C0 (initial conc)
what measures plasma binding + drug distribution
in vitro binding assays
measure if the drug binds to proteins
in vivo assays that measure drug binding to proteins
PPB BTB BPP
plasma protein binding
brain tissue binding
blood plasma partitioning
in the body, what equilibrium is available to drugs
being bound + binding to smt or being free
what happens when a drug is bound to something
it cannot bind to the target
it isnt effective
what happens when the drug is free to move
it can bind to the target
it can be effective
what things in the body could a drug bind to
proteins
lipids
tissues
what normally metabolises small molecules
CYP P450
cytochrome p450
what are the cytochrome p450
family of enzymes located in the HEPTATIC ENDOPLASMIC RETICULUM
what are the 2 stages of drug metabolism
phase 1
phase 2
what is the main goal for both phases of metabolism
to increase water solubility of the drug to facilitate excretion via sweat/urine
phase 1 description of metabolism
CYP chemically modifies the drug
they add OH to make the molecule more polar (SAR)
add more polar FG to change the way its metabolised
what is phase 2 of metabolism
conjugation of modified scaffold to polar molecules (sugar)
they conjugate the molecuke in order to make it more polar so it can be eliminated rapidly in bile/urine
what are the phase 2 metabolism conjugation examples
glucuronidation
sulphation
amino acids
acetylation
methylation
what is glucuronidation
attaching a drug to an oxidised glucose in order to increase its polarity to be rapidly eliminated
what is sulphation
adding a sulfo group to a drug to increase its polarity in order to be eliminated quicker
what is a sulfo group
think sulfuric acid
HSO3
difference between a sulfated drug and a normal drug
a sulfated drug is more polar and therefore easily eliminated
what technique can be used to improve metabolism of drugs
SAR
structure activity relationship
how is SAR generally used in order to improve drug metabolism
moving// substituting certain functional groups in order to block certain processes // strengthen bonds
SAR + improving metabolism:: how do we block aromatic hydroxylation
substitute a phenyl ring with a para-chlorine group to deactivate the ring
SAR + improving metabolism:: how do we block metabolism
adding certain FG
making bonds stronger by replacing Hydrogens with Fluorines
stronger bonds need more time to be broken
what does changing the structure of a compound do
changes the SAR
changes the metabolism
changes the amount of doses needed
do we watch a drug that needs lots of frequent doses or one that doesnt need as much doses
we want a drug which needs a little amount of doses
in order for a drug to have a small number of doses,, what must SAR do
it must decrease the drugs metabolism,, allowing it to be present in the body for longer periods of time
what does a short half life mean
it means the drug spends less time in the body
more doses will be needed to maintain a high concentration of it
SAR tries to give drugs aaa
longer half life
more time in body
less doses needed
what organ is the major site of drug metabolism in the body
the liver
what happens in the liver
metabolism of most drugs
what are 50% of marketed drugs eliminated by
the heptatic mediated metabolism
HMM
what is the HMM
heptatic mediated metabolism
how 50% of marketed drugs are metabolised
what are liver microsomes
subcellular fractions that cotain membrane bound drug metabolising enzymes like CYP
how are subcellular fractions obtaines
liver microsomes are obtained via cell fractionation
name a membrane bound, drug metabolising enzyme in the liver
CYP
what can microsomes be used to determine
used to determine the in vivo intrinsic clearance of a compound
intrinsic clearence equation
Clint = Vmax (max rate of enzymatic reaction) /// Km (enzyme dissociation constant)
what does intrinsic clearence tell us,, Clint
how efficient an enzyme is at metabolising the drug
– faster Vmax,, rate of enzyymatic reation = more efficient metabolism
high intrinsic clearence akaaa
high clearence category
aka fast rate of metabolism
aka efficient metabolism
name 2 toxicity tests
hERG
mitochondrial toxicity
what is hERG
a gene
human ether a go go gene
inhibiting the hERG gene leads to negative effects on the heart (cardiotoxic effects)
role in cardiac repolarisation
we want to test that our drug does not interfere wth hERG
what is mitochondrial toxicity + what tissues does it effect
metabolic disease
affects active tissues/ tissues with more energy consumption:
skeletal muscles, cardiac + neurological tissues
what cell is the source of atp
the mitochondria
steps of drug ingestion to drug excretion
drug is ingested
drug undergoes body processes
drug is either modified or unchanged
drug is excreted
name 2 types of drug excretion
active excretion
passive excretion
how does passive excretion occur
kidney filtration
how does active excretion occur
using proteins such as kidney transporters
active excretion uses transporters and there are many in vitro methods to study these transporters
vesicular transport is an assay method,
recombinant cell lines,
bidirectional transport assays in polarised monolayers
- identifies cytotoxic compounds
what is in vitro adme used for
to provide insight into how a cell responds to a new drug in an isolated + controlled environment
what are the 3 pros of in vitro adme
- cheaper than using animal models
- faster than in vivo assays
- easily automated using organ on a chip
what are the 2 conc of in vitro adme
- physiologically limited (only a few cells can be tested at a time)
- hard to tranlate into in vivo results
why are there new trends in adme research
- there was ethical concerns over the use of animals
- interspecies pathophysiological differences between animal models and humans
what is a new trend in adme research
- use of 3d cell models instead of an animal model
still a work in progress tho
