A clinical trial tests potential treatments in human volunteers to see if they should be approved for wider use in the general population. A treatment could be a drug, medical device, or biologic substance, such as a vaccine. Trials may be designed to test the safety and effectiveness of an experimental therapy, to see whether the new therapy is better than standard therapy, or to compare the effectiveness of two standard therapies.

Clinical trials include a written research study plan (called a protocol) and informed consent forms, which must be approved by a local Institutional Review Board (IRB). The IRB reviews the research and informed consent forms to ensure that the research subject’s rights are protected and that the study does not present any unnecessary risk to the research subject. The research study plan describes the types of people who may participate in the trial, the length of study, risks and benefits, and the study procedures, tests, medications, etc.

There are four phases of clinical trials. Each phase has a different purpose and help researchers answer different questions about the experimental drug or treatment:

Phase I: Researchers test an experimental drug or treatment in a small group of normal people (20-80) for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.

Phase II: The experimental study drug or treatment is given to a larger group of people (100- 300) who suffer from an illness to see if is effective and further evaluate its safety.

Phase III: The experimental study drug or treatment is given to a large group of people (1,000- 3,000) who suffer from an illness to see if it is effective, monitor side effects, compare it to commonly used treatments, and collect information that will allow the experimental drug or treatment to be used safely.

Phase IV: Post-marketing studies yield additional information such as a drug’s long-term risks, benefits, and how it compares to other drugs already in the market.