Researchers conduct clinical trials to try to learn if an experimental new drug works and is safe in humans in order for it to be approved. Clinical trials may also study a medical device or a medical procedure.
It takes a lot of research to develop a new drug treatment. Clinical trials are done in several steps, also called “phases”. Each phase has a specific purpose. The phases are designed to answer certain questions about the experimental drug being tested while aiming to keep the participants in each trial as safe as possible.
Researchers study experimental drugs in a lab before studying in humans. This type of research study is called a "pre-clinical trial".
The goal is to collect information about the experimental drugs. Then researchers ask the government and other independent groups for permission to begin a clinical trial in humans. Pre-clinical trials are required before the experimental drug can be studied in humans.
Phase 1 clinical trials are the first step after the pre-clinical trials. The Phase 1 clinical trials are usually the first time a new experimental drug is studied in humans
A Phase 1 clinical trial tests the drug in a small group of people (usually 15-100 participants).
Researchers design Phase 1 trials to learn:
Phase 2 clinical trials assess how well the experimental drug is working in people who are diagnosed with a disease or condition.
There are usually 100-500 participants.
Researchers design Phase 2 clinical trials to:
If the results of Phase 1 and Phase 2 clinical trials are positive, the experimental drug is studied in a larger number of participants with the disease or condition.
There are usually 1000-5000 participants.
Researchers design Phase 3 clinical trials to:
Phase 4 clinical trials are conducted after the experimental drug is approved by regulatory authorities. These clinical trials may take place over many years and usually involve a large number of participants.
Researchers design Phase 4 clinical trials to:
Requirements, also called “eligibility criteria”, can be related to age, gender, the type and stage of a medical condition or disease, previous treatment, and other medical conditions.
“Inclusion criteria” are the requirements a person must meet to be considered for the clinical trial. Allowing only certain participants to join a clinical trial helps researchers figure out if the results of the clinical trial are caused by the experimental drug and not by other factors.
“Exclusion criteria” are a list of conditions and reasons that might prevent a person from being in a clinical trial. These criteria may help protect people whose health may become worse if they joined the clinical trial.
Yes. A participant can leave a clinical trial at any time and for any reason. Participants may choose to tell the research team when they are leaving and why, but they are not obligated to do so.
It is important for people to ask questions before deciding to join a clinical trial. Some questions people might want to ask their doctor or nurse are below.
The clinical trial
Benefits and Risks
Participation and care
Costs can depend on a country’s laws and a participant’s health insurance.
Clinical research done in people must follow strict rules. Every clinical trial has a plan called a “protocol”. The protocol is a set of instructions that everyone in the clinical trial must follow. It is the plan for how the clinical trial will be carried out.
Before a clinical trial begins, it must be approved by a government department (such as the FDA in the United States of America or the European Medicines Agency in Europe) and other organizations (such as Ethics Committee). Different countries require different approvals. Approvals seek to ensure that trial participants rights and welfare are protected from unreasonable risks. Nonetheless, while efforts are made to control the risks to participants, some risks may be unavoidable since clinical trials are designed to learn more about an experimental drug.
A “placebo” looks like the experimental drug but does not have any medicine in it. In clinical trials, new drugs are sometimes compared with placebos. Some participants are given a placebo instead of the experimental drug. This helps to see if any effects seen are actually caused by the experimental drug being studied.
“Informed consent” is a process to make sure a participant understands important information about a clinical trial before agreeing to be in the clinical trial. Information includes the purpose of the clinical trial, rights as a participant, the experimental drugs used, and the risks and benefits.
If you are considering participating in a clinical trial, you can ask the doctors and nurses questions about the clinical trial to decide if you feel comfortable joining. You can also talk with family, friends, or your personal doctor before you decide if you will participate.
You decide if you want to participate or not in the clinical trial and sign the consent form. The informed consent can be translated into other languages for the clinical trial participant. No one should pressure or influence your decision in any way. Parents or guardians decide whether children can participate in a clinical trial, and whether to sign the consent form on their behalf.
If a participant decides to join a clinical trial, he or she must sign an informed consent form. Signing the form indicates that the participant understands the trial is research and that he or she can leave a clinical trial at any time. The research staff will help the participant do it safely.
If new benefits, risks, or medical problems are discovered during the clinical trial, the researchers must tell the participants. Participants may need to sign a new informed consent form to stay in the clinical trial.
If a patient does not meet the eligibility criteria to join a clinical trial, they should speak with their doctor or other healthcare provider to learn about what other options there are.
Below is a list of sources where more information about clinical trials may be found: