Drug discovery is a process that involves target identification, validation, lead identification and optimization, and preclinical and clinical testing in humans. The goal is to identify compounds that can safely and effectively treat diseases. Preclinical testing assesses safety and efficacy in cells and animals. If promising, an Investigational New Drug application is filed with the FDA and clinical trials in humans begin. Clinical trials have phases to test safety, efficacy, side effects, and optimal dosage in healthy volunteers and patients. If successful, a New Drug Application is filed with the FDA for review and potential approval.

1. Drug discovery is a
process which aims
at identifying a
compound
therapeutically useful
in curing and treating
disease
Product Characterization
lead identification & optimization
Target identification is process of
identifying the direct molecular
target(protein, nucleic acid, or
small molecule).
Identifying the biological of the
disease and the potential targets
for involvement ,is the first step in
the discovery of a medicine.
Drug
Target identification Target validation
Discovery
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 overexpression of the
presumed target. Tools for Target
Validation Antisense technologies si
RNA Antisense Oligonucleotides 15
Clinical trials are conducted in people
(volunteer)and intended to answer specific
questions about the safety and efficacy of
drugs, vaccines, other therapies, or new
methods of using current treatments
It generates data for discovering and
verifying the Clinical, pharmacological
(including pharmacodynamic and
pharmacokinetic) and adverse effects with
the objective of determining safety and
efficacy of the new drug
Drug developers must file an
Investigational New Drug application to
FDA before commencement clinical
research.In the IND application,
developers must include:
• Preclinical and toxicity study data
• Drug manufacturing information
• Clinical research protocols for studies to
be conducted
• Previous clinical research data (if any)
• Information about the investigator/
developer.
When any new drug molecule shows a
promising therapeutic activity, then the
molecule is characterized by its size, shape,
strength, weakness, use, toxicity, and
biological activity. Early stages of
pharmacological studies are helpful to
characterize the mechanism of action of the
compound.
1 Identification of Lead Once a target & a testing
system has been chosen, the next is to find a “Lead
Compound” which shows the desired
pharmaceutical activity.
A lead compound is generally defined as a new
chemical entity that could potentially be developed
into a new drug by optimizing its beneficial effects
and minimizing its side effects.
2 Lead Optimization 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.  Once
compounds with desirable in vitro profiles have
been identified, these are characterized using in
vivo models.
Clinical Research
The Investigational New Drug
Process (IND)
Preclinical Testing
Preclinical studies are conducted to define pharmacological and toxicological effects not
only prior to initiation of human studies but throughout clinical development.  Both in vitro
and in vivo studies can contribute to this characterization
The pre-clinical trials can be conducted in two ways: General pharmacology and Toxicology.
Pharmacology deals with the pharmacokinetic and pharmacodynamic parameters of drug.
Pharmacokinetic studies are very important to make known the safety and efficacy
parameters in terms of absorption, distribution, metabolism and excretion.
First stage of testing in human subjects
• Designed to assess the safety, tolerability, PK and PD of
drug.
• 20-25 healthy volunteers
The aim of a Phase I trial is to determine the maximum
tolerated dose (MTD) of the new treatment. • Phase I trials
are the first tests of a drug with a lesser number of healthy
human volunteers. In most cases, 20 to 80 healthy
volunteers with the disease/condition participate in Phase.
Objectives
Therapeutic confirmatory trials.
• Large scale, multicentre, Randomised, Controlled
trials .
• Target population: several 100’s to 3000 patients.
• Takes a long time: up to 5 years
• To establish efficacy of the drug against existing
therapy in larger number of patients, method of
usage, & to collect safety data etc.
Phase 0 clinical trials, developed in response
to the United States Food and Drug
Administration (FDA)'s recent exploratory
Investigational New Drug (IND) guidance, are
intended to expedite the clinical evaluation of
new molecular entities.Phase 0 trials besides
termed as human micro dose studies, they
have single sub-therapeutic doses given to 10
to 15 volunteers and give pharmacokinetic
data or help with imaging specific targets
without exerting pharmacological actions
Objectives
• Efficacy in patients (primary objective)
• Safety issues (secondary objective)
• Optimum dose finding
• Dose efficacy relationship
• Therapeutic dose regimen
• Duration of therapy
• Frequency of administration
• Therapeutic window
Phase 1: Safety and dosage
Phase 0 clinical trial
Phase 3: Efficacy and
adverse drug reactions
monitoring
Phase 2: Efficacy and side effects
Objectives
Done after drug has been marketed • Post Marketing
Surveillance (PMS).
No fixed duration / patient population
studies continue to collect data about effects in
various populations & side effects from long term use.
Detect the unknown/rare adverse drug reaction/s
Evaluation of over-dosage
Identifications of new indications
Dose refinement: Evaluation of new formulations,
dosages, durations of treatment
Evaluation in different age groups / types of patients
Comparative Benefit-Risk assessment
Phase 4: Post-Market Drug
Safety Monitoring
New Drug Application
A New Drug Application (NDA) expresses the
full story of a drug molecule. Its purpose is to
verify that a drug is safe and effective for its
proposed use in the people studied. A drug
developer must include all about a drug
starting from preclinical data to Phase 3 trial
datain the NDA. Developers must include
reports on all studies, data, and analysis.
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