Clinical Trials Phase 2

If a new drug or medical device shows no serious health effects during phase 1 of a clinical trial, the trial can progress to phase 2. By this time, the researchers overseeing the study have some idea of the safety of the treatment being tested.

Consequently, they can then increase the number of human subjects in phase 2 to include hundreds of volunteers. This is critical, as it gives researchers more confidence in the accuracy of the trial’s data.

Primary Purposes of a Phase 2 Trial

Phase 2 trials focus on efficacy, or how well the tested drug or device performs its intended function. In trials for a drug treatment, phase 2 may also address which doses of the drug are most effective.

Another primary purpose of clinical trial phase 2 is to monitor for side effects that may not have been seen during phase 1. Phase 1 trials involve a small number of human subjects, and side effects affecting only a portion of the population may not be detected. With the increased number of volunteers during a phase 2 trial, potential side effects and safety problems are more likely to appear.

Design of a Phase 2 Trial

If the tested agent is a new drug, volunteers receiving the drug may be compared to another group of volunteers who receive a placebo, which appears similar to the actual drug, but doesn’t contain the substance and doesn’t have any physical effects. As researchers compare treated patients to untreated patients, they can determine the effects of the new drug.

When a placebo comparison isn’t possible, an observational design is applied. In these cases, volunteers are given the drug and then observed for changes over the course of the treatment. Phase 2 trials testing new medical devices often have an observational design.


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