Basics of Clinical Trials

Defining the different phases of a clinical trial

NHF 2015 (Dallas, August 13-15) A plenary session for patients and caregivers at the National Hemophilia Foundation (NHF) 2015 Annual Meeting focused on explaining the basics of clinical trials. Clinical trials are research studies that evaluate whether a drug (treatment) is safe and effective for humans. In the United States, the drug undergoes several different phases of clinical trials before it can gain approval from the United States Food and Drug Administration (US FDA). The different phases of a clinical trial are listed below:  

  • Phase 1: These studies are done to test new drugs (treatments) in small groups of people for safety and side effects. These studies show the action and breakdown of drugs in humans. They also may provide some early insight into the potential side effects with increasing doses and early evidence to show the drugs work. This phase may include healthy participants and/or actual patients.
  • Phase 2: These studies include clinical trials that are conducted to show if the drug is effective at treating a particular condition. The study usually involves patients with the condition and is used to look at how well treatments work and look for additional safety concerns and identify common short-term side effects. Phase 2 studies can also be used to test different doses or treatment regimens to see which might be more effective to study further.
  • Phase 3: These studies use larger groups of people to confirm that the drug (treatment) works well, further look for any side effects in bigger populations of patients, and compare new treatments with other available “standard” treatments.   They are conducted to gather additional information about the benefit vs risk of the drug and support regulatory approval so that a company can market the drug (treatment).  
  • Phase 4: These studies are conducted after a drug has been FDA approved to gain the “real world experience”. They are done to collect additional information about the drugs risks and benefits in a broader group of patients, subgroups of patients that might have been excluded from the phase 2 and 3 studies, or in combination with other medications commonly prescribed for the disorder.