Clinical trials - what does each phase mean?

Pre-clinical research

  • Not performed on people.

  • Main goals are: collect drug/vaccine safety data and assess a safe dose for human studies.
  • Phase 0

  • First clinical trials done on people.

  • Main goals are: assess how the drug affects the body. Performed on 10-15 people.
  • Phase I

  • Performed on 15-30 people.

  • Main goals are: best dosage with fewest side effects and drug safety assessment.

  • If drug is deemed safe, continue to Phase II.
  • Phase II

  • Usually fewer than 100 people in the trial.

  • If a drug is found to elicit a response in the patients, it can enter Phase III trials.
  • Phase III

  • The comparison between the new drug and the standard-of-care drug is made.

  • 100 or more patients are enrolled in this phase.

  • These trials are often randomized (i.e patients are split into groups, ones that receive the new drugs and the control group that receives the standard-of-care drug).

  • Phase III trials can be stopped early if a) the side effects of the new drug(s) are too severe or b) if one of the drugs (in either the treatment or control group) shows much better results than the other.
  • Phase IV

  • Hundreds or thousands of patients are enrolled in this trial.

  • This trial occurs most often after the drug has been FDA-approved.

  • The purpose of this trial is to find rare side effects, interaction of the approved drug with other medication and other information.

  • Sources: Phases of clinical trials and Types and phases of clinical trials

    The median price for clinical trials is $19 million.