Learn more about clinical trials, including why people participate and how clinical trials work.


Clinical trials, also referred to as clinical studies, are scientific studies in which investigational medications are tested to evaluate their safety and effectiveness. Clinical trials are one of the most important steps in bringing new treatment to patients.

Visit The Center of Information & Study on Clinical Research Participation or Janssen's Global Trial Finder for more information.


  • Help others with similar symptoms or illnesses
  • Help advance the medical field
  • Potentially gain access to investigational medications
  • Receive study required care and attention from the clinical trial study team

Participation is voluntary and you can stop at any time. Please contact your study team if you have any questions about your participation.

  • How do clinical trials work?

    The purpose of clinical trials is to investigate whether an investigational medication is safe and effective in the treatment of a disease. Clinical trials must follow strict legal and scientific rules and guidelines. This helps protect the patients' rights and safety.

    Only approved medications are allowed for use by prescription. Approval is given by healthcare authorities such as the US Food and Drug Administration (FDA) and European Medicines Agency (EMA). The authorities only approve a medication when it has been proven to be safe and effective. To obtain information about safety and effectiveness of a new medication, clinical trials are performed.

    There are four phases of clinical trials.

    Phase I

    The first study in humans. These are small studies with 20-100 participants, mostly in healthy volunteers. The main objectives are to investigate:

    • Safety of the study medication
    • How the study medication is absorbed by the body and what dosage should be used
    • How the study medication is removed from the body
    • Potential side effects

    Phase II

    Small studies with around 100-500 participants. The main objectives are to investigate:

    • Ongoing safety
    • Whether the study medication works for a particular disease
    • The best dose of the study medication

    Phase III

    Large studies with around 500 or more participants. These are the main studies for final approval by health authorities. The main objectives are to investigate:

    • Safety and side effects in bigger populations
    • Whether the study medication works for a particular disease
    • How the treatment compares to already existing standard therapies

    Phase IV

    Large studies in patients after the study medication has been approved by regulatory authorities for prescription use (or public use if it isn't a medicine that requires a prescription). The main objectives are to investigate:

    • Side effects during day-to-day use in the population
    • Risks and benefits over a longer period of time
  • How are clinical trials regulated and approved?

    Clinical trials must be approved by government health authorities before patients can enter the trial and potentially receive the investigational medication. There are strict rules around how clinical trials must be run, and each trial is different. Patients must meet specific criteria to be included in a clinical trial.

  • Are clinical trials open to everyone?

    Sometimes patients cannot join a clinical trial if they:

    • Have other health problems in addition to the condition being studied
    • Are taking certain other medicines that may affect the trial result and/or put the patient at risk

    For these reasons, in some cases, these patients may not qualify for a clinical trial. Ask your doctor if participating in a clinical trial is right for you. The study physician will also help determine if a patient is a good fit for the study in question.

  • Steps to joining and participating in a Clinical Trial

    1. Eligibility check

    To see if the trial is a potential good match for you, you will answer an online survey (also called pre-screening questions) and you will be put in touch with a nurse that will perform a short phone-interview with you about the study. If you are eligible for the study, you will be contacted by a study clinic and invited to a screening visit.

    2. Informed Consent Form (ICF) Review

    The ICF helps you to make an informed decision about whether or not to participate. The study nurse or doctor is required to review the ICF with you.

    The form includes:

    • What you need to know about the study
    • Patient signature (your signature)
    • Doctor signature

    Please note that you can always decide to stop your participation in the study.

    3. Screening visits

    To make sure the trial is right for you, the study nurse or doctor will need to perform a thorough screening. Depending on the trial, different tests are performed, such as blood samples and general measurements (weight, blood pressure, etc.). The screening can be done in one or more visits, depending on how much data needs to be collected.

    4. Treatment

    The treatment period is different for each study. A treatment period can last a few weeks, several months or, in some cases, years. During the treatment period you will go for regular visits to your clinic, where the study staff will monitor your progress.

    5. Follow-up

    After the treatment ends there may be a follow-up period where your health is monitored by the study doctors. It may include visits to the study clinic for performing final tests or phone calls with the study team. The length of the follow-up period varies between clinical trials.