Types & Phases of Clinical Trials

Different types of clinical trials include:

  • Treatment trials, which test new treatments, new combinations of drugs, or new ways to do surgery or radiation therapy.
  • Prevention trials, which look for better ways to prevent disease in people who have never had the disease or to stop a disease from coming back. 
  • Diagnostic trials, which try to find better tests or methods for diagnosing a disease or condition.
  • Screening trials, which test the best way to spot certain diseases or health conditions.
  • Quality of Life trials, which look at ways to improve comfort and quality of life.

The four phases of a clinical trial include:

Phase I

Initial studies of the new drug or treatment carried out in a small group of people (20-80) for the first time in humans after laboratory and/or animal testing.  They may include healthy participants and/or patients. These studies:

  • look at how a drug acts in the human body;
  • evaluate safety;
  • find a safe dosage range;
  • identify toxic side effects with increasing doses; and
  • look at early signs of effectiveness.

Phase II

Controlled clinical studies where the new study drug or treatment is given to a larger group of people (100-300). Phase II trials are done to:

  • give initial information about effectiveness in people with the disease or condition;
  • identify the common short-term side effects and risks; and
  • look more at safety and benefits.

Phase III

Expanded controlled and uncontrolled trials of the new study drug or treatment to large groups of people (1,000-3,000). These studies:

  • confirm effectiveness;
  • look at side effects;
  • compare it or its combination with other drugs/treatments with the current standard therapy;
  • find out more about safety and efficiency; and
  • look at the benefit-risk relationship of the drug/treatment.

Phase IV

Post-marketing studies after the study drug or treatment is approved and the drug is available on the market. These studies provide more information such as risks, benefits and optimal use in order to improve usefulness on a large scale.