Phases of clinical trials
As clinical trials move forward from early and small Phase I trials through post-marketing Phase IV studies, more people are involved and more information is available on safety and effectiveness.
The following information comes courtesy of the Marti Nelson Cancer Foundation and Cancer Action Now:
- Pre-clinical Studies: Before a new medicine is tested on people (which is what the “clinical” part of the phrase “clinical trial” refers to), researchers must first determine its physical and chemical properties in the lab and study its effects on laboratory animals.
- Phase I Trials: Information on the new drug is submitted to the FDA (Food and Drug Administration) for IND status. IND stands for Investigational New Drug. The FDA, along with a local group of experts – called an IRB or institutional review board – approves the design of the clinical trial, and a small number of patients is given the drug by clinical investigators, the people who run clinical trials. During this phase, researchers try to figure out what happens to the drug in the human body: how much of it can be safely given, how it affects various organs, how it’s metabolized, etc. Usually only a very small number of people are involved in this first phase of human testing.
- Phase II Trials: This phase of testing involves larger numbers of human volunteers and aims to determine how effective the new drug is in treating the disease it’s designed to combat. In some cases the results are so impressive a drug can be approved on the basis of Phase II trials alone. More often, the drug moves into Phase III testing.
- Phase III Trials: Larger studies, perhaps involving as many as several hundred to several thousand people, are conducted comparing the new drug to a currently approved medication.
- Post-marketing Studies (Phase IV Trials): Required for drugs approved under accelerated approval to confirm that the drug is, in fact, as effective as the clinical trials suggest. Can also be used for gaining additional indications (on-label approved uses) for a drug that’s already on the market.
Last Update: January 9, 2009
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