Phases of Clinical Trials

Clinical trials are scientific studies that are conducted to find ways to prevent, screen for, diagnose or treat diseases. These trials also help scientists find which approach works best for certain illnesses or groups of people. Clinical trials play an important role in healthcare decision making and are categorized into four main phases:

Phase I: The goal of phase I is to discover if a new treatment is safe and to determine the best way to administer the new treatment, as well as to see if it has any possible side effects.

This trial is usually conducted with 15 to 30 patients who are divided into small groups called cohorts. A dose of the new drug is given to the first cohort and, if he or she does not show any severe side effects, a new cohort is given a higher dose of the same drug. The dose increases until doctors find the best dose for future testing. If the treatment is found safe, it is moved to Phase II in the trial.

Phase II: In this phase, the test is designed to assess the safety and efficacy of an experimental treatment.

Less than 100 patients usually join a Phase II trial. In this phase, doctors also observe the patients’ side effects. If the treatment works, the test proceeds to Phase III.

Phase III: Testing in this phase will attempt to discover if a new treatment is better than a standard treatment.

This phase may include hundreds to thousands of patients around the country or globally. Each patient has a chance of being in one of the two following groups:

Control group − the group getting the standard treatment

Study group − the group getting the new treatment being tested

Phase IV: A Phase IV trial finds additional information about the long-term benefits and side effects of the treatment.

Doctors usually study the treatments that have already been approved by the FDA. The goal of this phase is to continue studying the side effects of a new treatment.

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