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What are Clinical Trials?

A clinical trial is a research study that explores whether a medical treatment or device is safe and effective for humans. It plays a critical role in the process of bringing new therapies to patients.
It typically takes 12 years (from the moment of discovery in the lab) for a potential new therapy to gain approval for use within patients. And trials conducted during clinical development generate thousands of pieces of data that are generally used by regulatory agencies, such as the US Food and Drug Administration (FDA) to determine approval for use of the therapy and in which medical indications.

Patient Volunteers

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

欧洲杯竞猜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

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

Phase 2 trials generally assess the effectiveness of an experimental therapy at treating a specific illness or medical condition.

欧洲杯竞猜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.

Phase 3

Phase 3 trials test the results of earlier trials in much larger groups of people and gather additional information on the effectiveness and safety of the experimental therapy.
This phase will usually involve several hundred to several thousand participants across multiple study locations. These trials are often randomized, where participants are arbitrarily allocated to receive the experimental therapy, placebo, or another therapy (a “comparator”), and “double-blinded,” in which neither the investigator nor the participant are aware if the therapy given is the true experimental therapy, placebo (medication with no active ingredients), or another therapy (a “comparator”). Phase 3 trials generally provide the primary basis for the benefit–risk assessment for the new therapy and much of the core information about the therapy that is analyzed for inclusion in final labeling if approved by the regulatory authority.


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. 

欧洲杯竞猜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

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.