Types of Clinical Trials
The many different types of clinical trials can be
broadly divided into two main categories:
+ + Observational studies do not test drugs
or treatments. Instead, researchers examine
participants’ health and may monitor volunteers
over a certain period. With observational
studies, researchers collect data to advance their
understanding of how to track and treat Parkinson’s,
and how the disease naturally changes with time.
Participating in some observational studies could
include visiting a clinic for examinations, having
blood drawn or undergoing brain scans. Other
studies, such as The Michael J. Fox Foundation’s
Fox Insight (foxinsight.org), only require that
you log on to your computer or smartphone to
complete a questionnaire every few months. (See:
“A Technological Revolution in Research,” pg. 13.)
+ + Interventional trials test whether a drug or other
type of therapy works and is safe. Experimental
therapies could include not only medications,
but also exercise, surgical procedures, vitamins,
supplements and even complementary therapies
such as acupuncture or meditation. Each trial has
a different objective and a unique plan called a
protocol so the level of volunteer commitment for
each varies.
Phases of Interventional
Clinical Trials
Clinical trial testing of a new therapy follows a
sequence of phases. Each phase answers different
questions and requires a thoughtfully designed trial
and new group of willing volunteers:
+ + Phase I trials test a potential therapy, procedure
or drug for the first time in a small number of
people (usually about 10 to 100). Often these
are “control,”* volunteers — people without
Parkinson’s. These trials typically evaluate the
safety of a new therapy. They also often yield
information on side effects, effectiveness of
delivery method (e.g., by mouth, injection,
etc.) and appropriate dosage levels. For most
interventions, they last on average several
months, but they may be much longer for certain
surgical therapies.
+ + Phase II trials more comprehensively assess a
treatment’s safety, and determine preliminary
efficacy and side effects in a larger group of people
(usually a few hundred) with Parkinson’s. They
can last months to a few years.
These trials typically are randomized, controlled
studies. This means that one group of participants
receives the experimental treatment, while
the other (a “control” group) receives either
the standard of care or a placebo (an inactive
substance that looks exactly like the treatment).
The standard of care is one that medical experts
accept as the proper one and widely use. When
this doesn’t exist, researchers use a placebo. For
example, we don’t currently have Parkinson’s
disease-modifying therapies (medications that
slow or stop disease progression). So, in trials
testing new potential disease-modifying therapies,
researchers use placebos for comparison to
evaluate the therapy’s effects.
Participants are assigned to groups by a strategy
that mimics chance, or flip of a coin. Often these
studies are “double-blind” as well, meaning that
neither patients nor the research team know who is
getting the experimental treatment.
+ + Phase III trials confirm or disprove a therapy’s
efficacy, safety and side effects in an even larger
group of people with Parkinson’s (anywhere
from 200 to 2,000, although trials testing surgical
therapies may be smaller). Phase III trials, which
also are randomized and controlled, last several
years. Rather than being carried out at one
location, Phase III are often multicenter trials,
meaning they combine the results from volunteers
who participate at many different medical centers.
In order for a therapy to move forward through
Phase I and II, it must meet safety and efficacy
standards. When Phase III studies confirm
these results, a drug maker can submit a new
drug application to the U.S. Food and Drug
Administration or an equivalent application
to the European Medicines Agency or another
governmental body. From there, the review process
can take six to 12 or more months, depending on
the agency’s protocol. If approved, a drug then can
be manufactured and sent to pharmacy shelves.
Once therapies reach the market and doctors
and patients are using them in the “real world,”
companies conduct Phase IV clinical trials. These
studies primarily evaluate long-term side effects in
*Underlined words indicate a commonly used term. Find the definitions in the glossary, starting on page 44.
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Navigating Clinical Trials: A Guide for Parkinson’s Patients and Families