You are here
What are Clinical Trials?
Clinical trials involve hundreds to many thousands of volunteer trial participants. Every trial is governed using well-defined ethical rules and standards to protect participant safety.
For patients suffering from a condition that is currently untreatable, participation in a clinical trial may provide access to potential new therapies. While participating, volunteers obtain closely controlled care in research medical facilities, in addition to helping others by contributing to medical research.
Phases of Development
Clinical Development Process
An experimental therapy is first tested in the laboratory and in animal studies. After this “preclinical” testing, and only if shown to meet certain safety criteria and have value as a potential new therapy, the therapy advances to clinical testing in humans (known as phases).
Phase 1 clinical trials mark the first time an experimental therapy is administered to humans.
Phase 1 trials usually focus on ensuring the therapy is safe to use in people, rather than how effective it may be as a treatment for a given disease. During this phase, escalating doses of the experimental therapy are given to a small number of study participants so that researchers can measure the body’s response, including how it is absorbed, its duration in the bloodstream, and which dosage levels are safe and well tolerated.
Phase 2 trials generally assess the effectiveness of an experimental therapy at treating a specific illness or medical condition.
Information about the experimental therapy's safety, side effects, and potential risks are also collected. In this phase, researchers work to determine the most effective dosages for the experimental therapy and the most appropriate method of delivery, such as tablets, extended-release capsules, infusions, or injections. Phase 2 clinical trials involve a larger number of trial participants, typically up to several hundred, who usually have the medical condition that the experimental therapy is intended to treat.
Filing an application for registration with the country’s health regulatory authority is the next step in bringing a potential new therapy to patients. In the United States, a new drug application (NDA) is filed with the US FDA.
In Europe, a market authorization application (MAA) is filed with the European Agency for the Evaluation of Medicinal Products (EMEA). Descriptions of the therapy’s manufacturing process, along with quality data and trial results from all preclinical and clinical trials, are provided in order to demonstrate the safety and effectiveness of the new therapy.
If approval is granted, the new therapy can then be sold for use as detailed in the final approval label granted by the regulatory authority.
Phase 4 trials—also called "postmarketing studies"—are conducted after regulatory approval and are critical to informing the ongoing use of the therapy. Through such trials, researchers collect additional information about longer-term risks, benefits, and optimal use. These trials often involve thousands of participants and may continue for many years.