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1. Introduction
2. Phases of Clinical Trial:
a.Phase 0
b. Phase 1
c.Phase 2
d.Phase 3
e.Phase 4
3.Conclusion
4.References
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Introduction
Clinical Trial:
Any investigation in human subjects intended to
discover or verify the clinical, pharmacological, and
other pharmacodynamic effect of an investigational
product and to identify any adverse reactions to an
investigational product and to study absorption,
distribution, metabolism,excretion of an
investigational product with the object of ascertaining
its safety and efficacy.
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Clinical trial is a systematic investigation in
human subjects for evaluating the safety &
efficacy of any new drug.
Clinical trials are a set of tests in medical research
and drug development that generate safety and
efficacy data for health interventions in human
beings.
Phases of clinical trial
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Phase 0
Phase 0 is a recent designation for exploratory, first-in-human
trials conducted in accordance with the United States Food and
Drug Administration's (FDA) 2006 Guidance on
Exploratory Investigational New Drug (IND) Studies. Phase 0
trials are also known as human micro dosing studies.
Micro dosing helps researchers select better drug candidates for
clinical trials by providing early human PK and bioavailability
data.
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Distinctive features of Phase 0
 Primary goal:- To assess Pharmacodynamic and
Pharmacokinetic particularly oral bioavailability and halflife of the drug.
 Dose: it is 1/100th of therapeutic dose.
 Subjects: 10-15 healthy volunteers.
 A Phase 0 study gives no data on safety or efficacy, being by
definition a dose too low to cause any therapeutic effect.
 Phase 0 clinical trial are not mandatory. They are case to
case based.
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Phase 1
Phase I trials are the first stage of testing in human subjects.
Normally, a small group of 20–100 healthy volunteers will be
recruited.The duration will be 6-12 months.
Phase I trials also normally include dose-ranging, also called
dose escalation studies, so that the best and safest dose can be
found and to discover the point at which a compound is too
poisonous to administer.
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Distinctive features of Phase 1
 Primary goal: To assess the safety (pharmacovigilance),




tolerability, pharmacokinetics, and pharmacodynamis of a
drug.
These trials are often conducted in an inpatient clinic, where
the subject can be observed by full-time staff.
Phase I trials most often include healthy volunteers.
The tested range of doses will usually be a fraction of the
dose that caused harm in animal testing.
Volunteers are paid an inconvenience fee for their time spent
in the volunteer centre. Pay depends on length of participation.
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Different kinds of phase1 trial
Single
ascending
dose
Multiple
ascending
dose
Food
effect
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Phase 2
Once a dose or range of doses is determined, the next
goal is to evaluate whether the drug has any
biological activity or effect. Phase II trials are
performed on larger groups (100-300) and are
designed to assess how well the drug works, as well
as to continue Phase I safety assessments.The
duration will be 6 months to several years.
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Types of Phase 2
Phase 2a
How much
drug should
be given
Phase 2
Phase 2b
How well
the drug
response to
the dose
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Distinctive features of phase 2a
 Primary goal: To determine the therapeutic efficacy.
 Pilot trials: Dose response determination, determine
dose regimen and determination of target population.
 Subjects: Few hundreds . Patients fitting narrow
eligibility criteria.
 Trial design: Comparison with baseline status. Open
level or single/ double-blind.
 Dose escalation.
 Parallel dose response.
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Distinctive features of Phase 2b
 Pivotal studies.
 Objectives: Focus on aspects of phase 2a trial.
Blinding.
Placebo or other concurrent control.
Crossover treatments.
Multicenter.
 Subjects: similar to phase 2a.
 Trial design: Single or double blinded.
Conducted at multiple sites.
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Phase 3
Phase III studies are randomized controlled multicenter
trials on large patient groups (300–3,000 or more
depending upon the disease/medical condition
studied) and are aimed at being the definitive
assessment of how effective the drug is, in
comparison with current 'gold standard' treatment.
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Types of Phase 3
Phase 3a:
 Subjects: large.
 Trial design: open level or
single or double blinded.
 Multicenter.
 Testing different stages
of the disease indication.
 Dosage forms ,formulation
 Different routes.
 Pharmacoeconomic
evaluation.
Phase 3b: Phase III trials will
continue while the regulatory
submission is pending at the
appropriate regulatory agency.
This allows patients to continue to
receive possibly lifesaving drugs
until the drug can be obtained by
purchase. i.e. Antiretroviral,
Anticancer etc.
 Peri-approval studies.
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Phase 4
Phase IV trial is also known as post marketing surveillance Trial. Phase IV
trials involve the safety surveillance (pharmacovigilance) and ongoing
technical support of a drug after it receives permission to be sold. The
safety surveillance is designed to detect any rare or long-term adverse
effects over a much larger patient population and longer time period than
was possible during the Phase I-III clinical trials. Harmful effects
discovered by Phase IV trials may result in a drug being no longer sold, or
restricted to certain uses: recent examples involve cerivastatin (brand
names Baycol and Lipobay), troglitazone (Rezulin) and rofecoxib (Vioxx).
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Conclusion
Clinical trial may occur in several different phases .
Drug are developed in several different phases to
meet the multiple objective in the safest, most
efficient manner.
Phase is only a description and not a set of
rules.
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