Understanding Clinical Trials
Last updated: June 2019
A clinical trial is a research study that is conducted to determine whether a specific medical intervention, such as a treatment, device, procedure, or change in behavior is safe and effective in humans.1,2 A clinical trial may be designed to compare a new treatment to one that is already available, to a placebo (contains no active ingredients), or to no intervention. Further, some clinical trials compare interventions that are already available to each other.
The process of investigating the safety and efficacy of a specific intervention is complex, and clinical trials are actually one of the final stages of that investigation. A new intervention will first be examined in a laboratory, and if data for that intervention look promising, the next step could involve testing that intervention on animals. Of course, even if that intervention seems promising in animals, it may or may not have similar results in humans. Therefore, testing a new intervention in humans is necessary. This testing is done in multiple phases, which are defined by the Food and Drug Administration (FDA).
Clinical trial phases
The Phase 0 study is a relatively new designation. They are exploratory in nature and involve very limited human exposure to the drug. They are also known as human microdosing studies, with a goal of speeding up the process of development for promising drugs by examining the pharmacokinetics of the drug in a very small number of patients (10-15).
Phase 1 studies are usually conducted with a small group of healthy volunteers (usually between 20-100 people) and examine safety of the drug. The goal is to evaluate the drug’s most frequent and serious adverse events. Often times a secondary goal will be to look at how the body processes the drug (metabolism and secretion).
Phase 2 studies gather preliminary data on the efficacy of a drug in people who have a certain disease or condition, and these studies include a larger number of patients (typically 100-300). Study participants receiving the drug may be compared with similar participants receiving a different treatment, which is usually an inactive substance (called a placebo) or a different drug. The safety of the new drug continues to be examined.
Phase 3 studies gather more information about safety and effectiveness of a drug. Phase 3 studies include a much larger group of participants (often 1000-2000), with the goal of definitively assessing how efficacious a treatment is. It is typical for there be at least two successful Phase 3 trials that demonstrate the safety and efficacy of a drug to gain approval from the FDA.
Phase 4 studies are conducted after FDA has approved a drug for marketing. These studies gather additional information about a drug’s safety, efficacy, or optimal use.
Funding for clinical trials
Clinical studies can be funded by a variety of sources, including pharmaceutical companies, academic medical centers, voluntary groups, federal agencies such as the National Institutes of Health, the U.S. Department of Defense, and the U.S. Department of Veterans Affairs. Physicians, health care providers, and other individuals can also sponsor clinical research.
Clinical trial locations
Clinical trials take place in a variety of settings, including hospitals, doctors’ offices, universities, and community clinics. Often times, a clinical trial will have multiple sites (locations). This is determined by who is conducting the trial.
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