How a clinical trial works


Who runs clinical trials?

Clinical trials can be sponsored or funded by federal agencies, pharmaceutical companies, academic medical centers, or voluntary groups. However, the clinical trials are run by a principal investigator who is usually a medical doctor. She is joined by a research team made up of doctors, nurses, social workers, or other healthcare professionals.

Clinical trial phases

The clinical trial research process can be described by phases, each with a different purpose aimed at different questions.

  • Pre-clinical testing
    • Before a drug can be tested in humans, a safe dose must be determined; this is a main goal of pre-clinical studies.
  • Investigational New Drug Application
    • In the US, a pharmaceutical company must submit an application to the FDA’s Investigational New Drug (IND) program for permission to ship an experimental drug across state lines to clinical investigators. The FDA reviews the application to make sure that the drug is safe to test in humans in any planned clinical trials. IND approval only allows the drug to be tested in humans, but not yet for it to be marketed and sold in treatment of the disease.
  • Phase I
    • In this phase, the study assesses drug safety by determining what the drug’s most frequent and adverse effects are.
  • Phase II
    • In phase II, studies focus on drug effectiveness. This is whether a drug works in people who have a certain condition or disease.
  • Phase III
    • Here the study tests drug effectiveness on a larger scale in populations. This is used to determine the best drug dosage and see how the drug reacts in combination with other drugs.
  • Approval
    • After FDA approval is received for a drug to be put on the market for use in clinical care, studies are conducted to continue gathering information about a drug’s efficacy, optimal use, and safety in Phase IV trials (to study long-term effects) and post-marketing studies (to examine specific populations).
  • Post-marketing studies
    • These studies focus on special populations and the drug’s efficacy within these populations.

How long is a clinical trial?

Each trial in each step of the clinical research process varies in length depending on the study. Participants are told how long the trial will last before they enroll to participate.


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