Bench to bedside Flashcards
Order of drug discovery process
Discovery - target validation hit identification lead identification lead optimisation nomination phase clinical trials - phases I-IV
What characteristics do we need our drug to have?
good bioavailability good absorption slow metabolism - allow for absorption no toxic metabolites bodily distribution to facilitate access to the target
Achieving a pharmacodynamic output at a molecular level?
enzyme inhibition
receptor antagonism/agonism
Introduce groups which drive up affinity for the target protein to improve potency (lower dose can be given)
Introduce groups which achieve selectivity (reducing toxicity)
H-bonding drives interactions with key amino acids in the target protein
Lipophilic can provide interactions with drug target
Achieving the correct pharmacokinetic profile to enable access to the target for a sustained time period?
ADME
Where the drug goes (i.e. protein bound drug cannot exert effect)
how long it stays in the body (half life)
How it is metabolised
Ranges of bonds, short, mid, long
and groups typically involved
- vdW - Short range - aromatic and non-polar aliphatic side groups
- H-bond - Mid range - polar, uncharged side groups
electron- deficient H.
Electronegative atoms with lone pairs O, F, N - Ionic - long range- NH3 +ve with negative (e.g. O)
Role of halogen in SPR profiles
block oxidation but lipophilic so influence water solubility therefore absorption
Role of hydrophilic groups
promote phase II metabolism and renal excretion
How are hits against the target identified?
High throughput assay. Use compound library to identify any “hits”
Target enzyme + substrate = quantifiable signal readout
How is inhibitory activity carried out (simple version)?
Target enzyme + small molecule inhibitor compared with quantified readouts
Optimising for potency - ABSORPTION
Physical properties and formulation (log D, log P)
solubility
permeability (Caco2)
Optimising for potency - DISTRIBUTION
Vd Bioavailability Target selectivity Receptor drug interactions Protein binding
Optimising for potency - METABOLISM
Modifications - Phase I and Phase II
Renal and hepatic clearance
Optimising for potency - EXCRETION and TOXICITY
Toxicology assays - AMES - mutagenicity
HERG - screens for cardiotoxicity/arrhythmias
in vivo safe dosing, toxic dose
IC 50
EC50 and IC50 definitions
EC50 Half maximal response drug concentration
IC50 concentration of inhibitor where response is reduced by half
What does DMPK stand for?
Drug Metabolism and Pharmacokinetics
What is IHC?
Immunohistochemistry (IHC) is an important application of monoclonal antibodies to determine the tissue distribution of an antigen of interest in health and disease
what occurs in phase 2a trials
dose finding and PK in 10s of patients
2b trials?
confirm efficacy with confidence 10-100 patients
binding roles:
- Amine
- Amides
- Carboxylic acids
- Esters
- Aromatic ring
- amine HBD/HBA if lone pair available (N)
- amide - HB
- Carboxylic acid - HB - good ligand for Zn, Ionic bonding
- Esters - used to mask polar groups
- Aromatic ring - vdWs. Phenol - HB
Quick summary of enalapril optimisation
- Thiol improves potency (but S/Es) so replaced aromatic (S1)
- COOH essential for oral administration (salt forming group) - RCOOH + NaOH = RCOONa + H20
- Aliphatic S2 occupancy
- COOH binds ERG (Zn)
- Carboxylic acid too polar (masks as ethyl ester in prodrug)
Summary of farnesyl transferase inhibitors
- Zn bound in FT active site increases nucleophilicity of the Cys thiol group
- Thiol co-ordinates Zn and has good affinity for FT site
- Aromatic - higher affinity
- Free carboxyl - affinity for binding
in vivo test for CYP
liver hepatocytes + compound = metabolites and any interactions
Planar aromatic structures in topoisomerase I inhibitors
and other drug development
promote stacking in solude state preventing dissolution
(inert = no salt forming groups => hydrolyse
Tertiary aliphatic amine allows formulation as a salt
in vitro testing
- pharmacology
- PK
- Safety (IHC)
- affinity/potency target test, MOA, effect in complex assay system
- PK - Clearance, PAMPA, Caco-2 (permeability), Ussing chamber, Solubility (max absorbed dose), Plasma protein binding
- Safety - selectivity - affinity/potency
specificity - cell lysis
front-loaded HERG (cardiotoxicity)
AMES - (carcinogenicity)
