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Clinical Trial Process

Drug Discover Process Website 1The U.S. Food and Drug Administration (FDA) continuously reviews clinical trial data to ensure safety standards are met, and treatment benefit is likely, before allowing clinical trials to move from one phase to the next.

There are three primary stages that a new drug must go through before being approved for public use by the FDA. You can learn more about these phases on our drug development webpage here.

The FDA team reviews the drug sponsor’s New Drug Application (NDA), to examine all trial data collected (from preclinical research and clinical trials), and the treatment’s intended use - if the benefits outweigh the risks of the therapy, the NDA may be approved. After approval, a phase 4 study examines possible long-term effects.

  • Phase I clinical trials test new treatments in small groups of healthy volunteers (20-100) to evaluate safety, determine safe dosage levels and identify side effects. This phase is usually short, spanning from a few months, and less than a year.
             
    • Goal of phase 1 clinical trials: Test the safety, side effects, and best dose of a new treatment.
  • Phase II clinical trials test the drug on 300-500 volunteers who have the disease to further evaluate its safety and effectiveness. Phase II trials span from several months to two years.
                           
    • Goal of phase 2 clinical trials: Continue to test the safety of a new treatment and see if new treatment works well enough (has promising results) to move to a phase 3 trial.  
  • Phase III studies test the drug on 1000-5000 volunteers with the disease to confirm its effectiveness, monitor side effects and compare it to commonly used treatments. This phase usually takes at least 1 to 3 years to complete.
                                                
    • Goal of phase 3 clinical trials: See how well the treatment works to prevent, diagnose or treat the disease, learn about any long-term side effects.
    • After phase III is completed, the national regulatory authority (like the FDA or the European Medicines Agency [EMA]) decides whether to approve the newly developed medication. National regulatory authorities review all data regarding effectiveness and safety to make a final decision. After approval, doctors can prescribe the new treatment to their patients.

  • Phase IV studies, also known as post-marketing research, are done after the drug or treatment has been marketed to the public to collect information about its effect in various populations, and any side effects associated with long-term use.
              
    • Goal of Phase 4 clinical trials: For researchers to continue to look at the treatment’s benefits for people, and to ensure that these benefits last many years.
Drug discovery development approval Flyer2

Download printable document here.