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What are Phases of Clinical Trials?

The development of new treatments usually progresses through levels of research, called phases, in the process of testing new drugs and procedures before they can be approved and released for general use.

  • Phase 1 Trials
    Phase 1 trials evaluate the safety of a new agent or device. Before these compounds are tested in phase 1 trials, they are extensively studied in laboratory animals. A Phase 1 trial may involve different doses of a drug to learn about how well people tolerate it and to help determine what the most effective dose will be.

  • Phase 2 Trials
    If the Phase 1 trial has shown that people tolerated the new agent well and did not experience serious side effects, the process moves forward to find out if the compound or device might be an effective treatment. Phase 2 trials usually include small groups of participants who have the disease/condition the new therapy is designed to treat. Phase 2 studies give researchers early information as to whether a treatment might be effective while continuing to confirm the safety of the treatment.

  • Phase 3 Trials
    If the previous phases have successfully demonstrated that a new compound or device is safe and may potentially be effective,  a phase 3 study is performed.  Phase 3 studies are generally a comparison between the new compound or device and the current standard of care.  Results from a Phase 3 study can lead to approval from the Food and Drug Administration (FDA). 

  • Phase 4 Trials
    After a compound or device is approved by the FDA and available for use, the FDA may require additional safety information be collected on the agent or device. 

Who Conducts the Clinical Trial?

Every clinical trial is led by a “principal investigator,” often a medical doctor or other medical professional. The principal investigator leads the research team that might include doctors, nurses and other health care professionals. The principal investigator is responsible for making sure the study is carried out properly and safely.

How Are Clinical Trial Participants Protected?

Before joining a study, participants undergo a process of Informed Consent, which includes discussion of the risks and potential benefits of participating in a study.

The institution conducting the research must utilize an Institutional Review Board (IRB). The IRB is made up of physicians, researchers, and community members. The board reviews every study before deciding if the study can move forward.  The main focus of the IRB is to protect the rights and welfare of study participants. The IRB monitors each study, at least annually, throughout the life of the study.  

The Food and Drug Administration (FDA) has strict regulations for the conduct of clinical trials to ensure the protection of study participants. 

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Who Can Participate in a Clinical Trial?

Many studies are designed for people with specific diseases or conditions. Others are looking for healthy volunteers, and some studies enroll both individuals with diseases/conditions, as well as, healthy volunteers for comparison. Every clinical trial has detailed criteria that determine whether an individual is eligible to participate.

Contact Information

Joint Clinical Trials Office Weill Cornell Medicine /
1300 York Avenue,
Box 305
New York, NY 10065 Phone: (646) 962-8215 Fax: (646) 962-0536

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