About Clinical Trials

Researchers conduct clinical trials to learn whether an intervention or experimental treatment works and is safe for people with specific conditions before it can be approved for use by the general population or those diagnosed with a specific disease.

Clinical trials can test experimental treatments such as investigational drugs, new combinations of drugs, vaccines, devices and digital therapies. They may also test procedures or changes in behavior, such as exercise or diet. Clinical trials may include healthy volunteers or people with specific illnesses or conditions. Often, before clinical trials involve people like you, researchers may need to test experimental treatments in the lab.

Before testing an experimental treatment in people, researchers must first get permission from government regulatory agencies. These agencies review the researchers’ development plans for the experimental treatment and the results from pre-clinical trials to decide if it is ok to proceed with clinical trials. In some countries clinical trials are also called “clinical studies” or “clinical research studies” or simply “trials."

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Phases of a clinical trial

Clinical trials are done in several steps, which are also called “phases." Each phase is designed to answer specific questions about the experimental treatment to see if it works and to understand what side effects may occur. As an experimental treatment moves through these phases, researches learn more about the treatment, its risks and its effectiveness.


Pre-Clinical Development

Before clinical trials can involve people like you, the experimental treatment may need to be researched in the lab. Once the researchers have enough information, they ask for permission from the government and independent groups called ethics committees to begin clinical trials.

Phase 1

These clinical trials are usually the first time an experimental treatment is studied in a small group of people. Phase 1 trials may study an experimental treatment in healthy volunteers. They may also research the late stage of diseases, like cancer where standard treatments are no longer effective. Phase 1 trials help researchers test the safety of a treatment and determine a safe dose or range of doses to be used in the next phase. Researchers also find out how the treatment acts in the body and may identify side effects people have when using the experimental treatment.

Phase 2

These clinical trials are done to learn if an experimental treatment helps participants who have a specific condition or disease. Phase 2 trials usually include a larger group of participants than Phase 1 trials. Researchers continue to study the safety of the experimental treatment. If the treatment is an experimental drug, researchers continue to learn about which dose works.

Phase 3

These clinical trials are done to confirm that an experimental treatment helps participants who have a specific condition. These clinical trials often compare the experimental treatment to another treatment or, if appropriate, a placebo. A placebo looks like a drug or treatment but does not have an active product or treatment in it. Using a placebo without another active treatment may not be appropriate in some conditions or diseases. In phase 3 clinical trials researchers also continue to study the safety of the treatment. After Phase 3, researchers share all the information learned from all phases of clinical trials with government regulatory agencies, such as the United States Food and Drug Administration, European Medicines Agency, or Pharmaceuticals and Medical Devices Agency in Japan. Based on the information, these agencies decide if a treatment can be approved for patients to take.

Phase 4

These clinical trials happen after a drug or treatment has been approved for patients to take. Clinical trials in phase 4 usually take place over many years because researchers want to learn about long term use and safety of a drug or treatment. Researchers may also look at other aspects of the treatment after it is approved, such as impact on quality of life. Phase 4 clinical trials usually include thousands of participants.

Why participate in a clinical trial?

Access experimental treatments and care

As a clinical trial participant, you may have access to experimental treatments before they are widely available. In addition, participation in a clinical trial provides an opportunity for you to play an active role in your own healthcare.

Help others by advancing medical science

Your participation helps researchers gather important information that may guide future research. When you participate, you are helping researchers learn of new ways to manage, treat or monitor a disease or condition.

Help researchers discover new treatments

What researchers learn from clinical trials helps them discover new or better treatments or tests that may help future patients.

What to expect when participating in a clinical trial

Here are some steps you can expect when you participate in a clinical trial:


You will talk to a member of the clinical team to learn about the clinical trial and to see if it may be a good fit for you. A research team member will explain the trial and ask you some questions about your health so you can decide together if the clinical trial is a match for you. This is also a good time to ask questions about participation details. The clinical trial doctor will also explain if participating in a clinical trial may impact other treatment options for your condition or illness.

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Clinical trial participation
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