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How Clinical Trials Work

It is an uphill battle to bring one treatment* to the market. Imagine leading an expedition where every step is more difficult than the last.

  • The process begins in the laboratory with basic investigations involving bench-top assays and other techniques, cells, and specially-bred animals. This is considered Basic Research/Drug Development.
  • Next, pre-clinical or translational research moves the successful treatment through further rigorous testing to prepare for clinical testing through Pre-Clinical/Translational Research.
  • Finally, the treatment is given to human volunteers enrolled in clinical trials that typically proceed through a succession of three phases (see Phase 1, Phase 2, and Phase 3 Clinical Trials).

These trials are used to determine the safety and effectiveness of the intervention on progressively larger numbers of people. Normally, if the results are positive in the first three phases—depending on the measurement of success defined at the beginning of each phase—the therapy will proceed to the FDA for review on whether it is deemed to be safe and effective for distribution to the public.

Once approved, the sponsor will manufacture the treatment on a large scale for distribution in the United States. Once on the market, the FDA monitors for serious adverse events, and additional clinical trials may be requested by the FDA or undertaken voluntarily by the sponsor company. The data gathering, analysis, and reporting that are necessary to complete these trials can take several years or more. In fact, it can take up to 15 years and more than $1 billion to bring one FDA-approved intervention to the market (please refer to the clinical trial SnapShot titled “An Uphill Battle”).

For a visual summary of the clinical trial process, view our infographic “An Uphill Battle.”

*Although we are using the word "treatment," clinical trials also involve medical research studies in which people participate as volunteers to test new methods of prevention, screening, and diagnosis of disease.



Sources of Information

U.S. Food and Drug Administration (FDA); National Institutes of Health (NIH); Center for Information & Study on Clinical Research Participation (CISCRP); Pharmaceutical Research and Manufacturers of America (PhRMA); Tufts Center for the Study of Drug Development [Updated Outlook 2010 and original referenced paper (DiMasi, Joseph A., Ronald W. Hansen and Henry G. Grabowski (2003) “The Price of Innovation: New Estimates of Drug Development Costs,” Journal of Health Economics 22(2):151-85, March)]; and a paper comparing the costs of different studies (Morgan, Steve, et al. “The cost of drug development: A systematic review” Health Policy 100 (2011) 4–17).

More in this Section

  • Before Human Trials

    Before human trials begin, the process starts in the laboratory, where it takes years of sifting through thousands of potential treatments to find a handful that were fit for testing in clinical trials.

  • Phases of Clinical Trials

    There are three phases to complete in the clinical trial process before a sponsor can submit their treatments to the FDA for consideration to be sold on the market.

  • FDA Approval Process

    The FDA only approves drugs that they determine to have solid evidence of safety and effectiveness for public use or consumption.

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