Clinical Trial Phases

Clinical trials consist of five phases; Early Phase I and Phases I-IV. Each phase is designed to test a different aspect of the new drug, device, or method. Once the new form of treatment has made it through all five phases, it is eligible for review and FDA approval. At this point, the FDA decides if the new treatment is as safe and effective as existing therapies. If successfully approved, the new product is introduced into the medical marketplace for a specific, approved use (clinical indication). That means many thousands or millions of new users, which can generate new findings that did not appear in the controlled trial. For that reason the new treatment will undergo ongoing testing even after receiving initial FDA approval to ensure it is safe for the general public. 

  • Early Phase I: Early Phase I trials test the initial safety and potency of the new treatment. These trials do not serve a diagnostic or therapeutic purpose. Since the purpose of this phase is to test the limits of the drug and determine how much a person can handle, most of the testing is done on animals rather than human subjects for safety reasons.

  • Phase I: Phase I trials aim to determine how effective the new drug, treatment, or device is and how the human body processes it. Researchers test varying dosages and methods of administering the treatment. It tests the capacity of the new treatment in order to figure out the safest and most effective dosage. Placebos are not used and tests are usually conducted on healthy individuals. Participants are also being monitored for possible side effects during this phase.

  • Phase II: Phase II trials investigate if the new treatment leads to prolonged life and/or better health outcomes. The purpose of this phase is to discover if the treatment worked as intended and if it improved the lives of the participants. Placebos are not usually used for patient volunteers. If a placebo is used, it is combined with the existing standard treatment. Researchers continue to look for adverse side effects.

  • Phase III: In a Phase III trial, researchers compare their new treatment to the existing standard treatment. They look to see whether the new treatment performs better than the current treatments available. In this phase, participants are separated into groups of those who receive the new treatment and those who receive the standard treatment. The new treatment may also be combined with other treatments to test what is most effective. Investigators may begin to request FDA approval during a Phase III trial.

  • Phase IV: In a Phase IV trial, the treatment being studied is one that has recently received FDA approval. Although the treatment has received approval it continues to be studied so that its long term effects can be monitored. If the treatment is found to have adverse side effects it may be taken off the market. Market-based comparisons between the new treatment and standard treatment are also made in this phase. A few of the questions the research may consider in this phase are: which treatment improves the patient’s quality of life? Which is more affordable and cost-effective?