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Steps of a Clinical Trial

Enrolling in a Clinical Trial

Clinical research to test a new treatment is a long process that requires many steps. Each step is important so researchers can learn if a treatment is effective, if it is safe for patients, and how it compares to current treatments. The research process must also protect the rights and welfare of patients. 

  1. In the United States, each research study is reviewed by an Institutional Review Board (IRB). An IRB is a committee of medical experts, scientists, doctors, and other representatives who carefully consider each new study before it begins. Every clinical trial has to be approved based on a careful evaluation of the potential benefits and risks. This helps protect the health and rights of patients.

  2. Only certain patients can be included in a clinical trial. Patients are screened to see if they meet certain criteria. The specific qualifications for a study are known as eligibility criteria or inclusion criteria. The criteria are different for each study. They may include the type or stage of disease, patient age, health conditions, and other factors. Patient screening helps to protect the health and safety of patients so that only those most likely to benefit in a safe way are included in the study. This also enables scientists to learn about the impact of treatment based on the characteristics of the participants.

  3. Participating in a research study is completely voluntary. There are many things to consider when deciding whether to enroll in a clinical trial. The process of understanding the aspects of a research study and choosing to participate is called informed consent. If the patient is not an adult or is not able to give consent, a parent or legal guardian will be asked to give written permission by signing an informed consent form. Children may also be asked to sign an assent form saying that they agree to take part in the research study. A member of the research team will explain the study so that the child and family understand and know what to expect. Younger children under age 7 are not usually asked for assent. Through the informed consent process, patients and families should feel that they have been given enough information to decide whether to participate.

    Patients should understand:

    • What is the purpose of the research?
    • Who is eligible to participate?
    • What treatments are included and how are they given?
    • What tests and procedures are done and how often?
    • What are the risks of treatment and procedures and how are they monitored?
    • What treatments are available outside of the clinical trial?
    • How does the research team communicate with patients?
    • How is information shared with others or kept confidential?
    • What should I do if I have questions or concerns?

Phases of Clinical Trials

Clinical trials follow a series of steps or phases. The research goals and plans are different depending on the phase of study.

Phase I

Phase I clinical trials test new treatments that are being studied for the first time. In this phase, a small number of people receive the experimental treatment. A main goal of this phase is to find out if the treatment is safe and to get information on the dose that should be used.

Questions answered by Phase I

  • Is the treatment safe?
  • What dose of the treatment should be given?
  • What are the side effects of the treatment?

Phase II

Phase II trials test the experimental treatment in more people for a longer period of time. The goal is to find out if the treatment works for people with a certain disease or condition. Side effects are monitored.

Questions answered by Phase II

  • What is the effect of treatment on a disease or condition?

Phase III

Phase III trials test the treatment in a large number of people. The experimental treatment may be compared against a standard treatment, or two different experimental treatments may be compared to each other. Side effects are monitored over a longer period time.

Questions answered by Phase III

  • How does the new treatment compare to a standard treatment?

Phase IV

Phase IV trials test the treatment in a very large number of people after the drug or device has been approved by the U.S. Food and Drug Administration (FDA). Researchers collect information about how the treatments are used and monitor side effects and effectiveness over long periods of time in a large number of patients.

Questions anwered by Phase IV

  • What are the effects of treatment in different people over time?
  • What are the long-term benefits?
  • What are the long-term risks?
  • How is the new treatment incorporated into medical care?

Reviewed: June 2018