Overview of Clinical Trials
What is clinical research?
Clinical trials are conducted to collect data regarding
the safety and efficacy of new drug and device
development. There are several steps and stages of
approval in the clinical trials process before a drug or
device can be sold in the consumer market, if ever.
Drug and device testing begins with extensive laboratory
research which can involve years of experiments in animals
and human cells. If the initial laboratory research is
successful, researches send the data to the Food and Drug
Administration (FDA) for approval to continue research and
testing in humans.
Once approved, human testing of experimental drugs and
devices can begin and is typically conducted in four
phases. Each phase is considered a separate trial and,
after completion of a phase, investigators are required to
submit their data for approval from the FDA before
continuing to the next phase.
Human Clinical Trial Phases
Phase I studies assess the safety of a drug or device.
This initial phase of testing, which can take several
months to complete, usually includes a small number of
healthy volunteers (20 to 100), who are generally paid for
participating in the study. The study is designed to
determine the effects of the drug or device on humans
including how it is absorbed, metabolized, and excreted.
This phase also investigates the side effects that occur
as dosage levels are increased. About 70% of experimental
drugs pass this phase of testing.
Phase II studies test the efficacy of a drug or device.
This second phase of testing can last from several months
to two years, and involves up to several hundred patients.
Most phase II studies are randomized trials where one
group of patients receives the experimental drug, while a
second "control" group receives a standard treatment or
placebo. Often these studies are "blinded" which means
that neither the patients nor the researchers know who has
received the experimental drug. This allows investigators
to provide the pharmaceutical company and the FDA with
comparative information about the relative safety and
effectiveness of the new drug. About one-third of
experimental drugs successfully complete both Phase I and
Phase II studies.
Phase III studies involve randomized and blind testing in
several hundred to several thousand patients. This
large-scale testing, which can last several years,
provides the pharmaceutical company and the FDA with a
more thorough understanding of the effectiveness of the
drug or device, the benefits and the range of possible
adverse reactions. 70% to 90% of drugs that enter Phase
III studies successfully complete this phase of testing.
Once Phase III is complete, a pharmaceutical company can
request FDA approval for marketing the drug.
Phase IV studies, often called Post Marketing Surveillance
Trials, are conducted after a drug or device has been
approved for consumer sale. Pharmaceutical companies have
several objectives at this stage: (1) to compare a drug
with other drugs already in the market; (2) to monitor a
drug's long-term effectiveness and impact on a patient's
quality of life; and (3) to determine the
cost-effectiveness of a drug therapy relative to other
traditional and new therapies. Phase IV studies can result
in a drug or device being taken off the market or
restrictions of use could be placed on the product
depending on the findings in the study.
Participating in a Clinical Trial
For more detailed information and answers to frequently
asked questions about participating in clinical trials,
please visit Volunteering for a Clinical Trial.
Funding Clinical Trials
Funding for clinical research comes from the federal
government such as the National Institutes of Health, the
Department of Defense, the Department of Veteran's Affairs,
and private industry such as pharmaceutical and biotech
companies, medical institutions, and foundations.
Patient Education Resources
CenterWatch offers a selection of books and brochures for patients and their families to learn more about participating in a clinical trial. Please visit our Store to order.