The 4 Clinical Trial Phases: A Primer

Doctors conducting a clinical trialThe entire process of clinical trials is developed to make certain that new therapies are better than existing ones. If your doctor suggests that you take part in a clinical trial, they've probably come to the conclusion that it’s the most suitable treatment option that might work for you.

If you’re wondering or a little nervous about the process, which is totally normal, here’s what you should generally expect at each phase.

Phase 1 Clinical Trials

The main objectives of this phase include the following:

  • Determine if a new therapy is safe
  • Determine the most effective method for giving the treatment
  • Look for indications that the disease is responding to the new therapy

Phase 2 Clinical Trials

During a Phase 2 clinical trial, the main goal is testing to see if the new therapy works and why and if there are any side effects. If it works, the therapy would be further studied during Phase 3. Fewer than 100 participants typically join this phase.

Phase 3 Clinical Trials

The purpose of this phase is to test whether the new therapy is more effective than all other existing standard therapies. This phase typically includes hundreds or thousands of participants all over the world or the country. 

Upon conclusion of this phase, the Food and Drug Administration (FDA) would then review the results of the trials to ensure the effectiveness and safety of the new therapy. If it deems the new therapy effective and safe for humans, they would approve it so it could be available for public use.

Phase 4 Clinical Trials

During this phase, the goal is to find out if the new therapy comes with long-term side effects.

As you could see, a new therapy has to go through all four clinical trial phases for it to be approved for public use, and every single phase serves a different purpose. Additionally, in most cases, when you join a clinical trial, you’d only have to participate in one phase as recommended by your doctor. While therapies are required to go through all the phases, you don’t.