What is a clinical trial?

A clinical trial is a research study involving people to answer specific health questions about the prevention, diagnosis or treatment of a disease or condition. If the clinical trial involves a treatment, it is only done after the treatment has undergone significant preclinical testing. In a clinical trial, patients receive treatment and the doctors carry out the research on how the treatment affects the patients. While clinical trials have risks for the patients who take part, each study also takes steps to protect patients.

Clinical trials can be conducted in four phases.

Phase I trials:
Phase I studies usually involve a small number of people and are conducted to determine how much of a new drug should be given, how often and what the dose is that will cause the least amount of side effects. In cancer studies, the effect of the treatment can also be explored.

Phase II trials:
Phase II trials continue to test the safety of the drug while evaluating more specifically how a treatment works.

Phase III trials:
If a drug has been found to be safe and shows efficacy, a phase III trial will be conducted to test the new drug in comparison to the current standard. Often these trials will enroll a large number of patients and may be conducted across the country or even the world. As with phase I and II trials, patients are still closely watched for side effects during a phase III trial, and more information is collected about the effectiveness of the treatment.

Phase IV trials:
Once a drug has shown that it is both safe and effective and has been approved for use in the general public by the regulatory agency, a phase IV trial may be conducted to answer additional questions regarding the drug’s risks, benefits or optimal use. These types of trials are referred to as post-marketing studies.