Normally, new medical products go through four phases of testing. Each phase (or stage) has a different purpose.
PHASE 1
Phase 1 is the first time a new treatment is tried in humans, which is also known as human subjects research. The goal of during Phase 1 is to find out if a new drug or treatment is safe. Volunteers are watched closely to see if there are any unwanted effects.
Phase 1 studies usually only include small numbers of people. If the treatment is found to be safe, it can move to the next phase.
PHASE 2
Phase 2 is the first step to find out if a new treatment really works. Phase 2 trials include more people. A larger number of participants allows researchers to see if the treatment shows ways that it is effective. Phase 2 studies are also used to determine the most appropriate doses or frequencies of treatments, and to test the treatment in selected groups of people. For example, a person’s age or gender might affect their response to treatment. With more people, it’s possible to see if the treatment works the same for people of different ages or genders.
Phase 2 research also continues to watch for side effects. With a larger number of people, it’s possible to see different types of side effects.
PHASE 3
Some people might have good results from treatments in Phase 1 or 2 trials. However, these good results could be due to factors other than the treatment. Even though Phase 2 trials have a larger number of participants than Phase 1, larger studies are still needed to make sure the effect of the treatment is real and is safe.
Phase 3 trials can have as many as 3,000 people. With a larger group, researchers can set stricter guideline for saying when and how a treatment is effective. For example, they might control for a lot more factors to be sure that it’s really the treatment that makes the difference.
In some cases, a treatment may already exist. Phase 3 studies can compare two or more treatments to see which one works best.
Unexpected effects are tracked even more closely in Phase 3. As more people try the treatment, it becomes clearer which unexpected effects are likely, whether they are harmful, and who is more likely to have them.
Phase 3 studies are needed to get reliable answers about safety and effectiveness of the treatment being studied. If results are good, the new treatment can be approved for doctors to prescribe to patients.
PHASE 4
Phase 4 trials happen after a drug is approved by the FDA. Phase 4 trials continue to track safety. More information is obtained about who is helped by a treatment. This research also finds out more about risks of combining different medical treatments and products.
Summary
This step-by-step process helps make sure new medical products can have the most benefits and least risks for people and communities. At each phase of research, it’s important to have diverse groups of patient volunteers. Diverse groups may include differences such as race, ethnicity, age, gender, and income, and overall health status. A new treatment can only move forward if it successfully passes each phase.