Innovative Partnerships
Phases of a Clinical Trial
A clinical trial may usually be categorized as falling into one of four stages or "phases."
Phase 1: A new therapy in the human body
This is the first experience using the new drug or treatment in humans. Both healthy adult participants and those adults and children with the disease being studied may be enrolled. Phase 1 studies are designed to determine how the drug is broken down in the human body and how it interacts with the human body. Phase 1 studies test the safety and possible side effects of the new therapy. Phase 1 studies may also provide the first evidence of effectiveness. Researchers use information from Phase 1 studies to design Phase 2 studies. Phase 1 studies typically enroll only a small number of people, sometimes as few as a dozen
Phase 2: First effectiveness studies
These are the first effectiveness studies of a drug in humans. Taking the drug at the doses and on the schedule found to be safe in Phase 1 trials, researchers administer the drug to participants with the disease or condition of interest. During Phase 2, researchers collect additional safety and effectiveness data, further study the side effects and risks, and collect additional information about the proper dose and dosing schedule. Phase 2 studies typically involve
control groups, are closely monitored, and are conducted in a relatively small number of participants, usually not more than several hundred participants.
Phase 3: Overall benefit & risk
These studies are expanded, longer-term research studies, performed after Phase
1 and Phase 2 studies have shown some evidence of both safety and effectiveness.
Phase 3 studies are intended to gather additional information about effectiveness
and safety needed to evaluate the overall benefit/risk relationship of the study
drug/treatment as compared to the current standard therapies for specific diseases/conditions.
Researchers collect additional information about drug or treatment-related side
effects, including the less common side effects. Several hundred to several thousand
participants may be enrolled. At the conclusion of a properly designed Phase 3 trial,
the new drug or treatment will be found to be inferior, equivalent, or superior
to the standard treatment.
Phase 4: Real-life conditions
The intent of these "post-marketing surveillance" studies is to learn more about the drug after it has been approved by the
U.S. Food and Drug Administration. In Phase 4 studies, researchers gather additional information about an approved drug's risks, benefits, and best uses associated with large-scale usage in "real-life conditions
Contacts:
Ann Melvin, MD
Associate Program Director,
Research Subject Advocate Program
(206) 987-2535
ann.melvin@seattlechildrens.org
Anthony Back, MD
Associate Program Director,
Research Subject Advocate Program
(206) 288-6797
tonyback@seattlecca.org