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Learn the Basics of Clinical Trials


Updated May 26, 2014

Clinical trails are studies conducted using human participants by researchers in government labs, medical schools, or by pharmaceutical or medical manufacturers, to test how well a new drug, medical device, diagnostic tool, therapy, treatment or form of prevention works to improve health, cure disease, or improve quality of life. The goal is to test efficacy and safety.

Before trials are conducted with human participants, they may have previously been studied with laboratory animals like mice or rats, to draw preliminary conclusions and to judge the safety of the protocol for human patients.

How Is a Clinical Trial Conducted?

There are five main components to any clinical trial, all considered to be part of the protocol:

1. Disease, illness or condition: The experiment is developed and carried out on people with the same set of symptoms,who have had similar results on diagnostic tests, are determined to have the same or similar diagnosis, and perhaps are considered in similar stages of a disease. Which of these criteria are used depends on the purpose of the trial (see #2 below.)

For example, a trial may be undertaken with a group of patients who are all considered to have stage three lung cancer. Or, a study may be done on patients who have recently developed macular degeneration.

2. Purpose: There are several types of trials:

  • Treatment trials, which probably account for the most clinical trials, test new drugs, therapies, devices, or surgeries.
  • Prevention trials test the possibilities for keeping someone from developing a specific disease or condition.
  • Diagnostic and Screening trials may result in new ways to detect or diagnose a specific disease or condition.
  • Quality of Life trials, also called Supportive Care trials are intended to study ways to keep people with difficult or chronic disease comfortable or to improve their quality of life.

No matter which type of trial it is, there will be a goal in mind, usually one which leads to having the treatment, device or protocol approved by the FDA to be marketed and sold in the US.

3. Patients: One important aspect of developing evidence is making sure the patients meet consistent criteria. The more similar the participants, the more specific the outcomes can be. Depending on the trial, they may need to be the same gender, of similar ages, from the same race, have other similar genetic make up, and have the same diagnosis with specific symptoms.

For example, a drug could be tested on post-menopausal women with heart disease and yield excellent outcomes, but may not be a good choice for men of any age who have heart disease accompanied by diabetes.

4. Approach: Patients are usually divided into two or more groups. The members of each group are provided with the same test, treatment or therapy for the same period of time, under the same circumstances.

For most trials, there will be at least two groups. One group will be given the drug or therapy being tested, and the other group, called the "control group," will be given no therapy, or will be given a placebo (a false, non-therapeutic therapy.) Sometimes there will be even more groups which may test additional aspects of the drug or therapy such as a larger dose of a drug.

For example, a new drug intended to alleviate the symptoms of arthritis may be tested. There may be three groups in the trial for the drug. One group may be given the new drug. The next group may be given a drug that is already a standard treatment, and the third group may be given a placebo.

Included in the treatment assignment is time. Some trials require patients to test a therapy for just a few days. Others will require months or even years in order for there to be enough evidence that it's the best choice, or yields the most benefits.

By making sure each group and member is consistent, researchers can determine which group benefited the most. Each group is given identical instructions, and when patients agree to participate, they often sign papers to promise to follow the directions to their best ability.

5. Phases: There may be up to four phases of any clinical trial, and each phase is the next step in determining the outcomes. If or when problems arise in a phase, then the trial must be adjusted before it can move up to the next phase. In some cases, when real problems are demonstrated (e.g. if people get sicker or die) then the trials may be stopped.

  • In Phase I trials, a small group of 20 to 80 people will be studied to evaluate the therapy being studied to make initial safety determinations, such as dosage amount and/or side effects.
  • In Phase II trials, a larger group (up to 300 people) will be studied for the same reasons as Phase I trials.
  • In Phase III trials, an even larger group (up to 3,000 people) will be studied to confirm the effectiveness of the drug, therapy or device being tested, monitor side effects, compare it to other treatments previously studied, and in general follow participants to confirm the treatment is safe. By the time a trial arrives at Phase III it may be considered effective and safe enough to be a good choice for treatment.

If a treatment is being studied and is found to be useful and successful through Phase III trials, it will be most often be submitted to the FDA for approval. If approved, will be marketed and sold.

  • Phase IV trials are sometimes requested by the FDA to be run after the treatment has been marketed for some period of time, to confirm the patients using that therapy, post-approval, are finding the same results as were reported from the first three phases of trials, and reported through the application process to the FDA.

Interested in Participating in a Clinical Trial?

There are a number of reasons patients may be interested in participating in a clinical trial. Wise patients know to weigh the risks and benefits, and to be fully informed about the trial before they participate.

Can't Find a Clinical Trial But Want to Try a New, Experimental Drug or Medical Device?

Under certain circumstances, you may be able to petition for a Compassionate Use Exemption.  Learn more about compassionate use, and how to apply for a compassionate use grant.

Learn more about clinical trials:

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