The experimental administration of new drugs or medical therapies to human patients in tightly controlled settings, to find out if there are any unexpected harmful side effects, before making the new drug or therapy available to the general population.

From the BioTech Dictionary at For further information see the BioTech homenode.

Clinical trials are monitored studies that test a new medical treatment, such as a drug or surgical procedure, on human subjects. New combinations of existing drugs or procedures are also tested in this manner. The trials analyze the treatment's safety and effectiveness at treating a certain ailment. If the new treatment passes clinical trials then researchers can petition the Food and Drug Administration (FDA) for approval to begin marketing. Both the federal government and private companies generally fund clinical trials.

Drugs often undergo years of pre-clinical trials before they are tested on humans. During this time they are analyzed in human and animal cells and animal models to get an idea of whether or not the treatment would be effective in humans. If the testing is promising, researchers can submit an Investigational New Drug application (IND) to the FDA. If it is approved then clinical trials can begin.

Clinical trials are divided into four phases:

  • Phase one: This phase analyzes the safety of the treatment. Between 20 and 100 healthy volunteers are given the treatment and monitored for any side effects. Subjects are given varying doses of the treatment to analyze which dose will be the most efficient yet have minimal toxicity and side effects. This ideal dose will be used as the standard in the next phases. If the treatment is a drug, its absorption, metabolization, and excretion from the body are also analyzed. This phase generally takes several months. Roughly seventy percent of treatments pass this phase.
  • Phase two: This phase determines how efficient the treatment is at treating its targeted ailment. Subjects in this phase generally consist of about 40 to 100 patients that have the particular ailment. Patients are given either the treatment or a placebo and monitored for any changes in the ailment. Studies are generally random double blind trials to prevent research bias. This phase can last from several months to a couple of years. Only one third of new treatments pass both phase one and two.
  • Phase three: In this phase the treatment is analyzed in anywhere from hundreds to thousands of patients. This is done to confirm the findings of the first two phases in a larger patient group and to get a better understanding of the treatment’s effectiveness and side effects. The treatment is also compared to any similar current treatments to determine which is more effective and has less toxicity. This phase often takes several years. Seventy to ninety percent of treatments that reach this phase will pass. Once treatments pass phase three researchers can petition the FDA for licensing. If approved, the treatment can be marketed to the public.
  • Phase four: This phase consists of surveillance of the treatment after it has been marketed. Long-term effectiveness, cost, and side effects of the treatment are monitored. This phase is generally not commonly done and the subjects and timeframe can vary widely.



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