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Phase 3 trial:

A Phase 3 study compares the results of people taking a new treatment with the results of people taking the standard treatment (for example, which group has better survival rates or fewer side effects). Phase 3 trials may include hundreds of people and are designed to prove the safety and efficacy of a new treatment.

Phase 2 trial:

A Phase 2 trial is a study to test whether a new treatment has an clinical effect (for example, whether it shrinks a tumor or improves blood test results).

Phase 1 trial:

A Phase 1 trial is the first step in testing a new treatment in humans. These studies test the best way to give a new treatment (for example, by mouth, intravenous infusion, or injection) and the best dose. The dose is usually increased a little at a time in order to find the highest dose that does not cause harmful side effects. Because little is known about the possible risks and benefits of the treatments being tested, Phase I trials usually include only a small number of study volunteers.