sign in sign up
<<
Home , Drug discovery, Lead compound

Topic 7 and design Pt. 1

Chapter 9 Patrick Contents

Part 1: Sections 9.1-9.3

1. Target disease 2. Drug Targets 3. Testing Drugs 3.1. In vivo Tests 3.2. Tests 3.2.1. Enzyme Inhibition Tests 3.2.2. Testing with Receptors AND DEVELOPMENT Stages 1) Identify target disease 2) Identify drug target 3) Establish testing procedures 4) Find a 5) Structure Activity Relationships (SAR) 6) Identify a 7) Drug design- optimising target interactions 8) Drug design - optimising pharmacokinetic properties 9) Toxicological and safety tests 10) Chemical development and production 11) Patenting and regulatory affairs 12) Clinical trials 1. TARGET DISEASE Priority for the

• Can the profits from marketing a new drug outweigh the cost of developing and testing that drug?

Questions to be addressed

• Is the disease widespread? (e.g. cardiovascular disease, ulcers, malaria) • Does the disease affect the first world? (e.g. cardiovascular disease, ulcers) • Are there drugs already on the market? • If so, what are there advantages and disadvantages? (e.g. side effects) • Can one identify a market advantage for a new ? 2. DRUG TARGETS-Remember? A) LIPIDS Cell Membrane Lipids

B) Receptors Enzymes Carrier Proteins Structural Proteins (tubulin)

C) NUCLEIC ACIDS DNA RNA

D) CARBOHYDRATES Cell surface carbohydrates Antigens and recognition molecules 2. DRUG TARGETS TARGET SELECTIVITY

Between species

• Antibacterial and antiviral agents • Identify targets which are unique to the invading pathogen • Identify targets which are shared but which are significantly different in structure

Within the body

• Selectivity between different enzymes, receptors etc. • Selectivity between receptor types and subtypes • Selectivity between isozymes • Organ selectivity 3. TESTING DRUGS

• Tests are required in order to find lead compounds and for drug optimisation

• Tests can be in vivo or in vitro

• A combination of tests is often used in research programs 3.1 in vivo Tests

• Carried out on live animals or humans • Measure an observed physiological effect • Measure a drug’s ability to interact with its target and its ability to reach that target • Can identify possible side effects • Rationalization may be difficult due to the number of factors involved • Transgenic animals - genetically modified animals • Drug - concentration of drug required to produce 50% of the maximum possible effect • Therapeutic ratio/index - compares the dose level of a drug required to produce a desired effect in 50% of the test

sample (ED50) versus the dose level that is lethal to 50% of the sample (LD50) 3.2 in vitro Tests-See drug binding supplement

• Tests not carried out on animals/humans Target molecules (e.g. isolated enzymes or receptors) Cells (e.g. cloned cells) Tissues (e.g. muscle tissue) Organs Micro-organisms (for antibacterial agents) • More suitable for routine testing • Used in high throughput screening • Measure the interaction of a drug with the target but not the ability of the drug to reach the target • Results are easier to rationalize - less factors involved • Does not demonstrate a physiological or clinical effect • Does not identify possible side effects • Does not identify effective prodrugs 3.2.1 Enzyme Inhibition Tests

• Identify competitive or non competitive inhibition

• Strength of inhibition measured as IC50

• IC50 = concentration of inhibitor required to reduce enzyme activity by 50% 3.2.2 Testing with Receptors

• Not easy to isolate membrane bound receptors

• Carried out on whole cells, tissue cultures, or isolated organs

• Affinity - strength with which compounds bind to a receptor

• Efficacy - measure of maximum biochemical effect resulting from binding of a compound to a receptor.

• Potency - concentration of an required to produce 50% of the maximum possible effect. Contents

Part 2: Section 9.4 Lead compounds from the natural world

4. The Lead Compound 4.1. Sources of Lead Compounds 4.2. Identification of Lead Compounds 4.3. Lead Compounds from the Natural World - Extracts - and Ancient Records - Herbal Remedies of Olde - Venoms and Toxins - Endogenous Compounds 4 The Lead Compound Introduction Def: A compound demonstrating a property likely to be therapeutically useful

• The level of activity and target selectivity are not crucial • Used as the starting point for drug design and development • Found by design ( or NMR) or by screening compounds (natural or synthetic) • Need to identify a suitable test in order to find a lead compound • Active Principle - a compound that is isolated from a natural extract and which is principally responsible for the extract’s pharmacological activity. Often used as a lead compound. 4.1 Sources of Lead Compounds

Plantlife (flowers, trees, bushes) Micro-organisms (bacteria, fungi) A) The Natural World Animal life (frogs, snakes, scorpions) Biochemicals (Neurotransmitters, ) Marine (corals, bacteria, fish etc)

B) The Synthetic World Chemical synthesis (traditional) Combinatorial synthesis

C) The Virtual World Computer aided drug design 4.2 Identification of Lead Compounds

A) Isolation and purification solvent-solvent extraction chromatography crystallization distillation

B) Structure determination elemental analysis molecular weight mass spectrum infrared ultraviolet nmr (1H, 13C, 2D) X-ray crystallography 4.3 Lead Compounds from the Natural World PLANT EXTRACTS 4.3 Lead Compounds from the Natural World PLANT EXTRACTS

MORPHINE

POPPY CAPSULE 4.3 Lead Compounds from the Natural World PPLLAANNTT EEXXTTRRAACCTTSS

•• OOPPIIUUMM -- MMoorrpphhiinnee

•• CCIINNCCHHOONNAA BBAARRKK -- QQuuiinniinnee

•• YYEEWW TTRREEEE -- TTaaxxooll 4.3 Lead Compounds from the Natural World PLANT EXTRACTS

WILLOW TREE - SALICYLIC ACID O OH O OH Acetic anhydride OH O CH3 O

COCA BUSH - COCAINE Me CH N 3 CO2Me N H O Procaine

O CH3 C NH2 H C O O 4.3 Lead Compounds from the Natural World O VENOMS AND TOXINS C OH O C N O O O Teprotide H C N CH C N CH C N H O O CH2 CH CH3 C N CH C N CH CH2 O O H 2 CH 2 C O CH3 H N CH C N CH C 2 N CH H 2 NH2 CH CH O 2 2 CH 2 C OH CH2 NH O C O HN C NH C N OH NH2 CH3 HS

Captopril (anti-hypertensive) 4.3 Lead Compounds from the Natural World

BUT WAIT….why do plants make these things???!!! 4.3 Lead Compounds from the Natural World MeO

VENOMS AND TOXINS CH3 N HO CH3 O H

H O H3C N OH H3C OMe Tubocurarine (from curare) 4.3 Lead Compounds from the Natural World MeO

VENOMS AND TOXINS CH3 N HO CH3 O H

H O H3C N OH H3C OMe Tubocurarine (from curare)

MeO OMe O O CH3 H N C C N MeO O (CH2)5 O OMe

OMe MeO OMe OMe Atracurium (Neuromuscular blocker) 4.3 Lead Compounds from the Natural World ENDOGENOUS COMPOUNDS: found in YOU

NATURAL LIGANDS FOR RECEPTORS

OH OH H H N HO N HO Me Agonist HO HO ADRENALINE SALBUTAMOL

NH2 NMe2

HO MeHN S Agonist O O N N H H 5-HYDROXYTRYPTAMINE SUMATRIPTAN 4.3 Lead Compounds from the Natural World ENDOGENOUS COMPOUNDS

NATURAL LIGANDS FOR RECEPTORS

OH O N Antagonist H H HO N OH Me

HO ADRENALINE PROPRANOLOL

Me NH H 2 N NHMe HN S HN N N CN Antagonist HISTAMINE 4.3 Lead Compounds from the Natural World ENDOGENOUS COMPOUNDS

NATURAL SUBSTRATES FOR ENZYMES

Enkephalins Enkephalinase inhibitors

HIV Peptides HIV Protease inhibitors

H CO2H O N O H H H H N N H N N N H2N H H H H O O OH CONH2 H L-Phe-L-Pro SAQUINAVIR Contents

Part 3: Section 9.4 - Lead compounds from the synthetic world

4.4. Lead Compounds from the Synthetic World - Organic Synthesis - Combinatorial Synthesis - Combinatorial Synthesis - Peptide Synthesis - Combinatorial Synthesis - Heterocyclic Synthesis 4.4 Lead Compounds from the Synthetic World

SYNTHETICSYNTHETICSYNTHETIC COMPOUNDCOMPOUND COMPOUNDSSS 4.4 Lead Compounds from the Synthetic World

O PRONTOSIL: a dye H2N N N S NH2 O NH2 4.4 Lead Compounds from the Synthetic World

O

H2N S NH2 O

SULFANILAMIDE: not RED 4.4 Lead Compounds from the Synthetic World

RUBBER INDUSTRY

CH3 S

C S N CH3 H3C N S C S H3C ANTABUSE 4.4 Lead Compounds from the Synthetic World

ORGANIC SYNTHESIS 4.4 Lead Compounds from the Synthetic World COMBINATORIAL SYNTHESIS

AUTOMATED SYNTHETIC MACHINES 4.4 Lead Compounds from the Synthetic World COMBINATORIAL SYNTHESIS - PEPTIDE SYNTHESIS

AMINO ACID

RESIN BEAD AMINO ACIDS

X

PEPTIDE 4.4 Lead Compounds from the Synthetic World COMBINATORIAL SYNTHESIS - HETEROCYCLIC SYNTHESIS

RESIN BEAD

N N Y

CHR1R2 O 4.4 Lead Compounds from the Synthetic World COMBINATORIAL SYNTHESIS - HETEROCYCLIC SYNTHESIS

N N N N RESIN BEAD R2 R3 O H 4.4 Lead Compounds from the Synthetic World COMBINATORIAL SYNTHESIS - HETEROCYCLIC SYNTHESIS

N N N N RESIN BEAD R2 R3 O R4 EtO R5 O 4.4 Lead Compounds from the Synthetic World COMBINATORIAL SYNTHESIS - HETEROCYCLIC SYNTHESIS

N N N N RESIN BEAD R2 R3 N R4 HN R5 O Contents

Part 4: Lead compounds - Impact of the project

4.5. Lead Compounds - Impact of the 4.6. Lead Compounds - de novo design 4.7. Design of Lead Compounds using NMR Spectroscopy 4.5 Lead Compounds - Impact of the human genome project

The Past Lead Compound Targets

The Future Targets Lead compounds 4.6 Lead Compounds - de novo design 4.6 Lead Compounds - de novo design

X-RAY CRYSTALLOGRAPHY 4.6 Lead Compounds - de novo design

PROTEIN STRUCTURE 4.6 Lead Compounds - de novo design

Receptor CH3 + O H3N ScaffoldScaffoldScaffold HO - Scaffold H- IONIC CO2 BOND Scaffold BON D

VDW BOND 4.6 Lead Compounds - de novo design

THYMIDYLATE KINASE INHIBITOR

NH

N N HN S O O LEAD O COMPOUND Optimisation

O

N N N S O H N 2 O

ANTICANCER AGENT 4.7 Design of Lead Compounds using NMR Spectroscopy

NMR SPECTROSCOPY 4.7 Design of Lead Compounds using NMR Spectroscopy

Binding Site

PPrrootteeiinn 4.7 Design of Lead Compounds using NMR Spectroscopy

PPrrootteeiinn

NO OBSERVABLE BIOLOGICAL EFFECT 4.7 Design of Lead Compounds using NMR Spectroscopy

CH CH CH 3 CH3 CH2

CH2

C CH C

13C NMR 4.7 Design of Lead Compounds using NMR Spectroscopy

CH CH CH 3 CH3 CH2

CH2

C CH C

13C NMR 4.7 Design of Lead Compounds using NMR Spectroscopy

PPrrootteeiinn

Optimise epitope 4.7 Design of Lead Compounds using NMR Spectroscopy

PPrrootteeiinn

Optimise Optimise epitope epitope 4.7 Design of Lead Compounds using NMR Spectroscopy

Link

PPrrootteeiinn

Optimise Optimise epitope epitope 4.7 Design of Lead Compounds using NMR Spectroscopy

LLEEAADD CCOOMMPPOOUUNNDD 4.7 Design of Lead Compounds using NMR Spectroscopy Design of a lead compound as an immunosuppressant

OH O

OMe N H N O HO O O Epitope B

MeO OMe OMe Epitope A 4.7 Design of Lead Compounds using NMR Spectroscopy Design of a lead compound as an immunosuppressant

OH O

OMe N H N O HO O O

MeO OMe OMe Lead compound