Clinical Trials >

Clinical Trial Phases

Clinical Trial Phases

Clinical trials are done in "phases," each of which answers a different question about the drug or treatment. The outcome of each phase determines whether the new drug or treatment will continue to be studied in the next phase.

Phase I Clinical Trials: Is a New Drug or Treatment Safe for People?

Phase I studies are usually the first research involving people and are designed to learn about safety and side effects. Because these studies are so preliminary and little is known about the treatment's effects, phase I trials are small (usually between 15-50 people) and are often limited to those who have not had positive results from other treatments.

Phase II Clinical Trials: Does the Treatment Work?

Drugs and treatments found to meet safety standards in phase I trials go on to phase II, which is focused on determining whether the treatment works as the medical researchers believe it will. Phase II trials tend to be small (25-100 patients).

Phase I and II trials, all participants get the study drug or treatment, that is, there in no placebo group.

Phase III Clinical Trials: Is it Better Than What's Already Available?

If a treatment works well in phase II, new studies are designed for phase III that measure its efficacy against the current best treatment. Phase III studies are usually large (several hundred people) so typically there are a number of different locations around the country that are enrolling patients in these studies.

If a phase III trial has good results, the next step is submission of an application for approval to the FDA.