Preclinical drug research
Types of drugs:
Chemicals: small molecules bv aspirin
Natural products: complex molecules bv chemotherapy
Biologicals: large complex molecules bv insulin, EPO,…
Major disease areas: cardiovascular impairment, respiratory diseases, neurodegenerative diseases, …
Development costs:
Cost of drug research and development: increasing because all the ‘easy’ molecules have been designed
Total cost: 0,8 – 1,5 billion USD
Total time: ± 10 years
New drug must have clear added value if there are already drugs for the disease
Fail fast , fail cheap: better to kill compound early on than having to kill it after investing a lot of
money in the development (clinical phase = 40% of total cost)
Failure rates: majority of compounds fail in preclinical development
lot of effort done to determine efficacy, toxicity, decay, …
to have drug fail in preclinical studies and not in clinical phases
Pharmacokinetics: main reason of drugs failing , difficult to
predict human ADME in animals
Investment shortage:
In neglected diseases
In orphan diseases: small part of population has disease
Pattent: needed for highest income because you have not competition
Early pattent: less time to make money but otherwise somebody may have already patented
the molecule
Blockbuster: drug that gives revenue of + 1 billion dollars a year
Genetics: high level of competition , high sale volume but low sale value ,
low medical differentiation
Mega-blockbusters: medium level of competition and medical differentiation ,
drug not too expensive
Targeted therapeutics: high medical differentiation(targeted) ,
low volumes of sale but drug is very expensive
Therapies:
Conventional therapeutics:
Conventional therapeutics: interventions aimed at alleviating the disease effects
by improving symptoms/prognosis , disease prevention , permanent cure
Natural products: bv antibiotics , anticancer , …
,Small molecules:
Broad chemical space
Various administration routes
Longterm pharmaceutical experience
Lower level of selectivity
Pharmacokinetic limitations
Often poor oral absorption
Non-conventional therapeutics:
Non-conventional health products:
Nutraceuticals: dietary preparations
o Some scientific background
o No regulatory approval needed
Cosmeceuticals: cosmetics supplemented with active substances
o Little/ no scientific background
Biopharmaceuticals:
Biopharmaceuticals: therapeutic protein/ nucleic acid preparations made by techniques involving
DNA technology
Bv insulin , blood clotting factors , enzymes , antibodies , vaccines , stem cells ,…
Straightforward discovery
Uncommon unexpected toxicity
High product quality
Expensive production
No oral activity
Short half-life
Species-specific action so animal models less reliable
Gene therapy:
Gene therapy: correcting genetic defects by altering genetic material of cells by recombinant DNA technology
introduce new genes to replace missing/defective genes
Not many licenced for clinical use yet
Exposure lasts a lifetime so must be very safe
Antisense-DNA: oligonucleotide complementary to known mRNA sequence can block expression selectively
Quick degradation in plasma
Need liposomal packing
Ribozymes: RNA-sequences that inactivate genes by catalysing DNA-cleavage
Cell-based therapy:
Cell-based therapy: cell replacement in degenerative diseases
o Cell grafts: leukaemia , bone-marrow malignancy
o Chrondrocytes: cartilage repair
o Keratinocytes: treat burns
Ethical issues: use of embryonic tissue
Organ- and tissue transplantation
Bionic devices
,Trends in drug discovery:
Physiological targets -> molecular targets: less phenotypic assessment and more molecular
Compound libraries + in silico predictions
New technologies: high throughput screening, PK-PD modelling, …
Parallel evaluation: lead optimization programmes run drugability, pharmacology, toxicology, …
studies at the same time
Drug development process:
! Preclinical packages precede every phase of clinical trials !
Therapeutic concept: decision to start project based on
Scientific and technical points: Could we do it? available targets, assays, models , patent situation, …
Operational points: Can we do it? timescale, resource needs(staff, facilities, investments), …
Strategic points: Should we do it? likelihood return of investment , unmet medical need, market
predictions,…
Target selection: identify compounds by screening libraries, consider Lipinski rules , …
Target validation: see if compound binds target by in silico assessment , do further screening and profiling
to end up with a few hits (compounds expected to be effective on target)
Lead finding: select the best out of a large number of compounds
Lead optimization: in previous lead fails select the next best compound and end up with 1 drug candidate
Preclinical trials:
Safety pharmacology
Genotoxicity
28-day repeat dose toxicologt in 2 species
3-12 chronic toxicology in 2 species
Reproductive toxicology
24-month carcinogenicity in 2 species
Clinical trials phase 1: test safety , pharmacokinetics in healthy humans
Clinical trials phase 2: test safety , efficacy in a few patients
Clinical trials phase 3: test safety , efficacy in many patients
Regulatory approval
Post-market surveillance: ongoing pharmacovigilance in a broad clinical population
, Candidate drug finding:
Target: has molecular recognition site (binding site) where the drug will bind
Binding site: typically hydrophobic pocket on surface of the target
Binding region: region in binding site involved in binding interactions
Binding groups: functional groups on the drug involved in binding interactions
Binding: intermolecular (not covalently) to have on/off effect
Target types: macromolecules
Lipids: cell membrane lipids
Proteins: receptors, enzymes, carrier proteins, structural proteins
Nucleic acids: DNA, RNA
Carbohydrates: cell surface carbohydrates, antigens
Lock-and-key: target and drug bind with high complementarity of surface properties between
protein and ligand energetically favourable conformation
Target selection:
Forward approach: analyse pathophysiology to find possible target of the disease
(disease -> target identified -> drugs developed) Bv AIDS -> reverse transcriptase HIV protease -> Saquinavir
Backward approach: analyse mechanism of action of existing therapeutics
(drug -> disease -> target) Bv benzodiazepines -> anxiety -> BDZ binding site on GABA A receptor
New drug targets: estimated 600-1500 drugable targets in humans , drugs for infectious diseases ,
non-target directed drugs (oxygen, vitamins, minerals, …)
Genomics:
Genetic information: to know the function at organism level -> identify therapeutic targets -> create drug
= Static information
Disease genes: mutations associated with a particular disease
Single gene disorder: gene-products not drug-targetable bv cystic fibrosis
Multiple gene disorder: gene products may be drug-targetable bv tyrosine kinase
Disease modifying genes: mutations in regulatory genes cause over/under-expression of normal non-
mutated genes
Drugable genes: gene product with drug-recognition binding site
Gene target identification:
Chromosomal mapping
Look for disease modifying genes
Differential expression in diseased and normal tissue
Proteomics:
Proteomics: look directly at the gene product
Ideal situation: 1 gene -> 1 protein -> 1 drug target
Disadvantages:
Splice variants
Multimeric / heteromeric receptors
Association between protein and non-protein receptors
Types of drugs:
Chemicals: small molecules bv aspirin
Natural products: complex molecules bv chemotherapy
Biologicals: large complex molecules bv insulin, EPO,…
Major disease areas: cardiovascular impairment, respiratory diseases, neurodegenerative diseases, …
Development costs:
Cost of drug research and development: increasing because all the ‘easy’ molecules have been designed
Total cost: 0,8 – 1,5 billion USD
Total time: ± 10 years
New drug must have clear added value if there are already drugs for the disease
Fail fast , fail cheap: better to kill compound early on than having to kill it after investing a lot of
money in the development (clinical phase = 40% of total cost)
Failure rates: majority of compounds fail in preclinical development
lot of effort done to determine efficacy, toxicity, decay, …
to have drug fail in preclinical studies and not in clinical phases
Pharmacokinetics: main reason of drugs failing , difficult to
predict human ADME in animals
Investment shortage:
In neglected diseases
In orphan diseases: small part of population has disease
Pattent: needed for highest income because you have not competition
Early pattent: less time to make money but otherwise somebody may have already patented
the molecule
Blockbuster: drug that gives revenue of + 1 billion dollars a year
Genetics: high level of competition , high sale volume but low sale value ,
low medical differentiation
Mega-blockbusters: medium level of competition and medical differentiation ,
drug not too expensive
Targeted therapeutics: high medical differentiation(targeted) ,
low volumes of sale but drug is very expensive
Therapies:
Conventional therapeutics:
Conventional therapeutics: interventions aimed at alleviating the disease effects
by improving symptoms/prognosis , disease prevention , permanent cure
Natural products: bv antibiotics , anticancer , …
,Small molecules:
Broad chemical space
Various administration routes
Longterm pharmaceutical experience
Lower level of selectivity
Pharmacokinetic limitations
Often poor oral absorption
Non-conventional therapeutics:
Non-conventional health products:
Nutraceuticals: dietary preparations
o Some scientific background
o No regulatory approval needed
Cosmeceuticals: cosmetics supplemented with active substances
o Little/ no scientific background
Biopharmaceuticals:
Biopharmaceuticals: therapeutic protein/ nucleic acid preparations made by techniques involving
DNA technology
Bv insulin , blood clotting factors , enzymes , antibodies , vaccines , stem cells ,…
Straightforward discovery
Uncommon unexpected toxicity
High product quality
Expensive production
No oral activity
Short half-life
Species-specific action so animal models less reliable
Gene therapy:
Gene therapy: correcting genetic defects by altering genetic material of cells by recombinant DNA technology
introduce new genes to replace missing/defective genes
Not many licenced for clinical use yet
Exposure lasts a lifetime so must be very safe
Antisense-DNA: oligonucleotide complementary to known mRNA sequence can block expression selectively
Quick degradation in plasma
Need liposomal packing
Ribozymes: RNA-sequences that inactivate genes by catalysing DNA-cleavage
Cell-based therapy:
Cell-based therapy: cell replacement in degenerative diseases
o Cell grafts: leukaemia , bone-marrow malignancy
o Chrondrocytes: cartilage repair
o Keratinocytes: treat burns
Ethical issues: use of embryonic tissue
Organ- and tissue transplantation
Bionic devices
,Trends in drug discovery:
Physiological targets -> molecular targets: less phenotypic assessment and more molecular
Compound libraries + in silico predictions
New technologies: high throughput screening, PK-PD modelling, …
Parallel evaluation: lead optimization programmes run drugability, pharmacology, toxicology, …
studies at the same time
Drug development process:
! Preclinical packages precede every phase of clinical trials !
Therapeutic concept: decision to start project based on
Scientific and technical points: Could we do it? available targets, assays, models , patent situation, …
Operational points: Can we do it? timescale, resource needs(staff, facilities, investments), …
Strategic points: Should we do it? likelihood return of investment , unmet medical need, market
predictions,…
Target selection: identify compounds by screening libraries, consider Lipinski rules , …
Target validation: see if compound binds target by in silico assessment , do further screening and profiling
to end up with a few hits (compounds expected to be effective on target)
Lead finding: select the best out of a large number of compounds
Lead optimization: in previous lead fails select the next best compound and end up with 1 drug candidate
Preclinical trials:
Safety pharmacology
Genotoxicity
28-day repeat dose toxicologt in 2 species
3-12 chronic toxicology in 2 species
Reproductive toxicology
24-month carcinogenicity in 2 species
Clinical trials phase 1: test safety , pharmacokinetics in healthy humans
Clinical trials phase 2: test safety , efficacy in a few patients
Clinical trials phase 3: test safety , efficacy in many patients
Regulatory approval
Post-market surveillance: ongoing pharmacovigilance in a broad clinical population
, Candidate drug finding:
Target: has molecular recognition site (binding site) where the drug will bind
Binding site: typically hydrophobic pocket on surface of the target
Binding region: region in binding site involved in binding interactions
Binding groups: functional groups on the drug involved in binding interactions
Binding: intermolecular (not covalently) to have on/off effect
Target types: macromolecules
Lipids: cell membrane lipids
Proteins: receptors, enzymes, carrier proteins, structural proteins
Nucleic acids: DNA, RNA
Carbohydrates: cell surface carbohydrates, antigens
Lock-and-key: target and drug bind with high complementarity of surface properties between
protein and ligand energetically favourable conformation
Target selection:
Forward approach: analyse pathophysiology to find possible target of the disease
(disease -> target identified -> drugs developed) Bv AIDS -> reverse transcriptase HIV protease -> Saquinavir
Backward approach: analyse mechanism of action of existing therapeutics
(drug -> disease -> target) Bv benzodiazepines -> anxiety -> BDZ binding site on GABA A receptor
New drug targets: estimated 600-1500 drugable targets in humans , drugs for infectious diseases ,
non-target directed drugs (oxygen, vitamins, minerals, …)
Genomics:
Genetic information: to know the function at organism level -> identify therapeutic targets -> create drug
= Static information
Disease genes: mutations associated with a particular disease
Single gene disorder: gene-products not drug-targetable bv cystic fibrosis
Multiple gene disorder: gene products may be drug-targetable bv tyrosine kinase
Disease modifying genes: mutations in regulatory genes cause over/under-expression of normal non-
mutated genes
Drugable genes: gene product with drug-recognition binding site
Gene target identification:
Chromosomal mapping
Look for disease modifying genes
Differential expression in diseased and normal tissue
Proteomics:
Proteomics: look directly at the gene product
Ideal situation: 1 gene -> 1 protein -> 1 drug target
Disadvantages:
Splice variants
Multimeric / heteromeric receptors
Association between protein and non-protein receptors
