Treatment interventions being tested can range from medical drugs, to medical devices, to introducing lifestyle changes (diet, exercise). Most clinical trials test new drugs by comparing them to no treatment, to an inactive version of a drug known as a “placebo”, or to a currently available approach. Clinical trials may take months to years to complete and are conducted in a series of steps, known as “phases”, described below.

Phase 1: Is the drug safe?

Healthy volunteers receive different doses of the drug and side effects are evaluated. Safe doses are chosen based on research performed prior to Phase 1, or “pre-clinical research”. The goal is to make sure the drug is not harmful. Usually lasts a few months.

Phase 2: Is the drug effective?

Similar to Phase 1, but the drug is given to a small group of volunteers affected by the medical condition it is intended to treat. This is commonly done by comparing how well participants do with the new drug compared to a placebo. Participants and doctors are typically “blinded”, or prevented from knowing whether the patient received the active drug or the placebo. This is meant to allow for unbiased observations of the participant’s health in response to the drug. Usually lasts a few months to years.

Phase 3: Is the drug still safe? Is it doing what is needed?

Testing becomes a bit more complex. The participant population is expanded while safety and efficacy of the drug continues to be tested. More detailed information about the drug as a treatment is gathered in this phase. Usually lasts several years.

Phase 4: The drug is approved and available on the market.

Long-term effects of the drug will continue to be monitored by pharmaceutical companies and compared to other available drugs and therapies for cost and efficacy.

If you would like to learn more about clinical trials, take a look at these resources by ClinicalTrials.gov and CenterWatch.

Snapshot written by Dr. Claudia Hung edited by Dr. Judit M. Perez Ortiz.