Clinical research that is related to developing products for patient care is divided into two preclinical and four clinical phases, each addressing different questions. The knowledge gained at each phase is assessed before progressing to the next. The table below provides an overview of the process. Click each phase to learn more.

Phase I studies, sometimes called “first-in-man,” begin to answer the question: Is this drug safe for use by humans? Because the side effects of the investigational drug are unknown, these studies are conducted with in-patient volunteers and are carefully monitored. These volunteers are willing to undertake a certain amount of controlled risk to be part of the study. Healthy volunteers may be paid to participate in the study; or, if the drug has a potential for toxic adverse events (AEs), it may be given to subjects with the disease or condition for which the drug is indicated. For example, a cancer drug, which affects cell metabolism, would be given to cancer patients rather than healthy subjects.

Phase I studies usually involve only a small number of subjects, and often last no more than two weeks. Many are single dose studies, in which a healthy volunteer takes the treatment only once. If the results of Phase I studies indicate that the drug is not safe for human use, the clinical development program will be abandoned.

Phase I studies ask the questions:

• Does the dose that is expected to be effective appear to be safe (that is, not associated with an undue number of AEs)?
• How quickly is the drug absorbed?
• Where is the drug distributed in the body?
• Which organs or organ systems are involved in metabolism of the drug?
• How quickly is the drug eliminated from the body?