About Clinical Trials

Clinical trials look at new ways to prevent, detect, or treat disease. The goal of clinical trials is to determine if a new test or treatment works and is safe. 

The idea for a clinical trial —also known as a clinical research study —often originates in the laboratory. After researchers test new therapies or procedures in the laboratory and in animal studies, the most promising experimental treatments are moved into clinical trials, which are conducted in phases. During a trial, more information is gained about an experimental treatment, its risks, and its effectiveness.

• Natural history studies provide valuable information about how disease and health progress.
• Prevention trials look for better ways to prevent a disease in people who have never had the disease or to prevent the disease from returning. Better approaches may include medicines, vaccines, or lifestyle changes, among other things.
• Screening trials test the best way to detect certain diseases or health conditions.
• Diagnostic trials determine better tests or procedures for diagnosing a particular disease or condition.
• Treatment trials test new treatments, new combinations of drugs, or new approaches to surgery or radiation therapy.
• Quality of life trials (or supportive care trials) explore and measure ways to improve the comfort and quality of life of people with a chronic illness.
  

Clinical trials are conducted in phases. Each phase has a different purpose and helps researchers answer different questions.

• Phase I trials: Researchers test an experimental drug or treatment in a small group of people (20–80) for the first time. The purpose is to evaluate its safety and identify side effects.
• Phase II trials: The experimental drug or treatment is administered to a larger group of people (100–300) to determine its effectiveness and to further evaluate its safety.
• Phase III trials: The experimental drug or treatment is administered to large groups of people (1,000–3,000) to confirm its effectiveness, monitor side effects, compare it with standard or equivalent treatments, and collect information that will allow the experimental drug or treatment to be used safely.
• Phase IV trials: After a drug is approved by the FDA and made available to the public, researchers track its safety, seeking more information about a drug or treatment’s risks, benefits, and optimal use.

For more information about clinical trials, see the webpage at National Institute of Health.