Drug discovery process.

DRUG DISCOVERY PROCESS
DR. VITHALRAO VIKHE PATIL FOUNDATION'S COLLEGE
OF PHARMACY, VILAD GHAT, AHEMADNAGAR
PRESENTED BY
MISS. S.R.BORUDE
M.PHARM
(SEM-2)ROLL NO.2
PHARMACOLOGY
UNDER
GUIDANCE OF
PROF.H.J.PAGAR
DEPT. OF
PHARMACOLOGY

FLOW OF SEMINAR
2
 Introduction
 Drug Discovery Process
 Phases Involved in drug discovery process
1. Target Identification
2. Target Validation
3. Lead Identification
4. Lead Optimization
5. Preclinical and Clinical Development
 References

INTRODUCTION
3
 Drug discovery is an inventive process of identifying a
compound or new medication based on knowledge of biological
target, therapeutically useful in treating and curing a disease.
 The process of drug discovery involves
 the identification of candidates,
 synthesis,
 characterization,
 screening,
 assays for therapeutic efficacy.
Once a compound has shown its value in these tests, it will begin
the process of drug development prior to clinical trials.

FLOW CHART OF DRUG
DISCOVERY & DEVELOPMENT
4
Identify disease
Isolate protein
involved in
disease (2-5 years)
Find a drug effective
against disease protein
(2-5 years)
Formulation
Preclinical
testing
(1-3 years)
Scale-up
FDA approval
(2-3 years)
Human clinical
trials
(2-10 years)

PHASES INVEDLED IN DRUG
DISCOVERY PROCESS
5
Target Identification
Target Validation
Lead Identification
Lead Optimization
Pre-clinical & Clinical
Development

PIPELINE FOR DRUG
DISCOVERY PROCESS
6

7
TARGET
 A drug target is the specific binding site of a drug in vivo
through which the drug exerts its action.
 It may be molecular or cellular structure involved in
pathology which are responsible for disease
 They may be
- G-protein coupled receptors - 45%
- Enzymes - 28%
- Hormones and factors - 11%
- Ion channels - 5%
- Nuclear receptors – 2%
1.TARGET IDENTIFICATION

Characteristics of target
8
 The bimolecular have special sites that match other.
 The bimolecular structure might change - when the bimolecular
binds to small molecules and the changes in structure normally
are reversible.
 Following the change in the biomolecule’s structure -
physiological responses occur and induce regulation of the cell,
organ, tissue, or body status.
 The physiological responses triggered by the changes in
bimolecular - complex regulation & therapeutic effect on
pathological conditions.
 The expression, activity, and structure of the biomolecule might
change over the duration of the pathological process.
 Small molecules binding to the bimolecular are drugs.

Tools For Target Identification
9
1) Cellular & molecular biology
2) Genomics
3) Proteomics
4) Bioinformatics
1) Cellular & molecular biology
 New tech.
 Aims
-discovering new genes and protein
-quantifying and analyzing gene expression between
diseased & normal cells

2) Genomics
10
 Field of science – structure, function, and mapping of genome
Types
a) Structural genomics
b) Functional genomics
a) Structural genomics
 Used to describe 3D structure of every protien encoded by a
given genome
 Characterize genome structure
b) Functional genomics
 Focus on gene transcription, translation, regulation of genes &
protein-protein interaction
 Measure all gene product like mRNA & protein within
biological samples

3) Proteomics
11
 Large scale study of protein & their function
 It is the study of the proteome, the complete set of proteins
produced by a species, using the technologies of large - scale
protein separation and identification.
 The analysis of proteins including protein-protein, protein
nucleic acid, and protein ligand interactions
4) Bioinformatics
 Bioinformatics is a branch of molecular biology that involves
extensive analysis of biological data using computers, for the
purpose of enhancing biological research.
 Bioinformatics methods are used to transform the raw sequence
into meaningful information (eg. genes and their encoded
proteins) and to compare whole genomes (disease vs. not).

2.TARGET VALIDATION
12
 Target validation is the process by which the predicted
molecular target – for example protein or nucleic acid –of a
small molecule is verified. Target validation can include
knockdown or over expression of the presumed target.
Tools for target validation
1) siRNA
2)Antisense oligonucleotide

Target validation process
13
Evaluating the hits.
Performing screening to find hits.
Constructing a high-throughput screen.
Designing a bioassay to measure biological activity
Evaluating its potential as a target.
Discovering a biomolecule of interest.

1) siRNA
14
 Small (or short) interfering RNA (siRNA) is the commonly
used for RNA interference (RNAi) tool for inducing short-
term silencing of protein coding genes.
 It is a double stranded RNA molecule which interferes with
the expression of specific genes by degrading mRNA after
transcription & preventing translation.
 siRNA is double stranded RNA(dsRNA). It consist of two
RNA strands, an antisense (or guide) strand and a sense (or
passenger) strand, which form a duplex
 20-24 bp length.16

Mechanism
15
 long dsRNA is cleaved by an endo-ribonuclease called Dicer to
form short interfering RNA or siRNA.
siRNA enters the cell and
binds to Argonaute protein
to form RISC.
 siRNA is then unwinded
to form single stranded
siRNA.
 si rna and RISC complex
find their complementary
mRNA

2) Antisense Oligonucleotide
16
 Antisense technology prevent the synthesis of specific
protein.
 AS- ONS;15-20 nucleotides which are complementary to
their target mRNA.
 When these AS-ON combined with target mRNA, a
DNA/RNA hybrid form which degraded by the enzyme
RNase H.
 RNase H is a non specific endonuclease which catalyse
cleavage of RNA.
 RNase H has ribonuclease activity cleaves the 3’-O-P bond
of RNA in a DNA/RNA duplex.

Mechanism
17

Conti…
18

3. LEAD IDENTIFICATION
19
 Lead
Compounds are chemical compounds that show
desired biological or pharmacological activity and may
initiate the development of a new clinically relevant
compound.
 Organic compounds are identified which interact with the
target protein and modulate its activity by using random
(screening) or rational (design) approaches.

Approaches for lead identification
20
1)
• High Throughput screenning
2)
• Combinatorial Chemistry/synthesis
3)
• Virtual Screenning
4)
• Structure Based Drug Design

1) High throughput Screnning
21
“High throughput screening (HTS) is an
experimental process or tool that employs a group of
techniques to quickly conduct a very vast number of
chemical, pharmacological, genetic, biological tests to
identify biomolecular pathways or pharmacological actions.
 10,000 – 100,000 compounds can be screened daily.

Types of HTS assay in drug discovery
22
a) Biochemical Assay
b) Cell Based Assay
a) Biochemical Assay
 Measure function of a purified target dentify compounds
that modulate the activity of the target protein.
 Recombinant (engineered) proteins, proteins isolated from
crude cell lysates .
 Target-based
- Enzymes (e.g. kinases,proteases)
- Receptors (e.g. Nuclear receptors, Kinase GPCRs)
- Hormones

b) Cell Based Assay
23
Phenotype-based
- Transcriptional read-outs Second messenger levels
- Protein interactions
- Cell viability (cell death/apoptosis)
- Proliferation

Conti….
24

Instrumentation
25
 Microtiter plate ( Assay Plate)
 Plates/containers made of plastic, having spaced wells
– up to 384, 1536 or 3456 wells.
 They would contain solvents (e.g. DMSO + test
compounds)
 They would also contain proteins, cells, etc. to be
analysed.
 Some might be kept empty or contain pure solvents to
serve as controls.

Detectors
26
 Diverse spectromètres (fluorescence, mass, NMR, FTIR,
etc.),
 Chromatography (Gas, Liquid, Ion exchange, etc.) and
 Microscopy (Scanning tunneling microscopy, atomic force
 microscopy, confocal microscopy) and Calorimeters.

Importance and Application of HTS
27
 Selection of compounds from a vast number synthesized by
combinatorial chemistry and other methods.
 For lead generation for the treatment of a disease.
 It is an efficient tool in studying biomolecular interactions
and pathways.
 It is highly efficient, fast, accurate and dependable in
compound screening
 Useful in DNA sequencing

2)Combinatorial chemistry/synthesis
28
“ The automated synthesis of a large number of compounds in
a short time period using a defined reaction route and a
large variety of reactants, Normally carried out on small
scale using solid phase synthesis and automated synthetic
machines”
Tech used in combinatorial chemistry
A. Solid phase tech.
1] Solid phase synthesis
2] Parallel synthesis
a) Hoghton’s tea bag procedure
b) Automated parallel synthesis

Conti…
29
3] Mixed combinatorial synthesis
4] Mixed & split synthesis
 Combinatorial chemistry plays a central role because of its ability to
create and produce molecules. In addition, combinatorial chemistry is
an active participant in drug development from the synthesis of
substances until its bulk production. Combinatorial chemistry can
create large population of analogs of a given scaffold.
 The analogs are synthesize in successive steps with the use of
robotics. The analogs are included in “combinatorial libraries”
consisting of a great number of wells, each one containing in
solution several dozens of compounds.
 Only a few milligrams of compounds can be obtained by this
method, however this is generally sufficient for primary
biological screening.

3)Virtual screenning
30
 It is a computational techinque used in drug discovery to
search libraries of small molecules in order to identify
those structure which are most likely to bind to a target,
typically a protein receptor or enzyme
 Goal- Reduction of the enormous virtual chemical space,
to a manageable number of compound that would inhibit a
target protein responsible for disease and also have highest
chance to lead to a drug candidate.

4. LEAD OPTIMIZATION
31
 Lead optimization is a process that begins with a compound that
displays an interesting biological action and ends with the identification
of the best analog. Molecules are chemically modified and
subsequently characterized in order to obtain compounds with suitable
properties to become a drug. Leads are characterized with respect to
pharmacodynamic properties such as efficacy and potency in vitro and
in vivo, Physiochemical properties, pharmacokinetic properties, and
toxicological aspects.
 Potency - refers to the amount of drug required for its specific
effect to occur.
 Efficacy - measures the maximum strength of the effect itself, at
saturating drug concentrations

Conti…
32
 Pharmacokinetics - determines the fate of xenobiotics.
It explains about “What the body does to the drug”. It often
divided into areas examining the extent and rate of
adsorption, distribution, metabolism, and excretion
(ADME).
 Pharmacodynamics– It determines the biochemical
and physiological effects of drugs, the mechanism of drug
action and the relationship between drug concentration and
effect. It explains about “What the drug does to the body”.

5. PRE-CLINICAL & CLINICAL
DEVELOPMENT
33
Pre-clinical development:
The pre-clinical development includes the following: develop
large scale synthesis; animal safety studies; carcinogenicity tests;
drug delivery; elimination and metabolism studies; drug
formulation experiments; dose-ranging studies in animals. Wide
ranging dosages of the compounds are introduced to the cell line
or animal in order to obtain preliminary efficacy and
pharmacokinetic information.

Conti..
34
Clinical development
1. Treatment trials: test experimental treatments or a new
combination of drugs.
2. Prevention trials: look for ways to prevent a disease or
prevent it from returning.
3. Diagnostic trials: find better test or procedures for
diagnosing a disease.
4. Screening trials: test methods of detecting diseases.
5. Quality of life trials: explore ways to improve comfort &
quality of life for individuals with a chronic illness.

Phases of clinical trials
35
Phase 1 - A small group of healthy volunteers (20-100) are
selected to assess the safety, tolerability, pharmacokinetics,
& pharmacodynamics of a therapy. Normally include dose
ranging studies so that doses for clinical use can be
set/adjusted.[6 months-1 yr]
Phase 2- Performed on larger groups (100-200) & are
designed to assess the activity of the therapy and
effectiveness of drug & continue phase1 safety
assessments.[2-3 yrs]

Conti..
36
Phase 3 -Randomized controlled trials on large patient groups
[1000-5000] [5yr]
 assessment of the efficacy of the new therapy,
 side effects are also monitored.
 to obtain approval from the FDA This document is
submitted to the FDA for review.
Phase 4 –
 After regulatory authority approval
 Larger no. of patients.
 DDI and dose response studies & safety studies

REFERANCES
37
1. Alexander Hillisch Rolf Hilgenfeld “Modern Methods Of
Drug Discovery”, Springer edition,1-12.
2. Prakash N, Devangi P (2010) “Drug Discovery”. J Antivir
Antiretrovir 2: 063-068. doi:10.4172/jaa.1000025.
3. V. Srinivasa Rao and K. Srinivas* “Modern drug discovery
process:” An in silico approach Journal of Bioinformatics and
Sequence Analysis Vol. 2(5), pp. 89-94, June 2011.
4. Patrick Bultinck, “Computational Medicinal Chemistry for
Drug Discovery,” dekkar publication, Page No. 617-634.

Conti…
38
5. Wang S, Sim TB, Kim YS, Chang YT (2004) “Tools for target
identification and validation.” Curr Opin Chem Biol 8: 371-
377.
6. John C. Alexander and Daniel E. Salazar, “Modern
Drug Discovery and Development,” PART | VII Human
Pharmacology 361-380.
7. Alderman E, Elands J (1998) “A novel approach to ultra-
high throughput screening.” Genet Eng News Jan 18: 2.
8. http://www.combichemistry.com/drug discovery.html

Conti…
39
9. Sunil Shewale, Sharad N Shinde, Vikas G Wawlw,
“Basics of Clinical Research”, 1st edition, Prathmesh
Publication, 7-8

Drug discovery process.

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