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Clinical trials are research studies designed to find new and better ways to treat patients with a wide range of diseases.

Physicians and scientists conduct clinical trials to find out:

  • Whether a newly developed treatment is safe and effective for patients
  • How and in what dose the new treatment is best administered
  • Whether the treatment is better than other treatments

Clinical trials may test new drugs, new approaches to using existing treatments, or newly developed methods of treatment.

Clinical trials are unique studies in that they rely on the participation of patients to test the new therapies. They are conducted only after a long process of research on the new treatment has already been completed.

Before ever testing a new treatment with people, studies are performed in research labs and with animals to examine possible benefits and side effects. By the time the treatment is given to patients in a clinical trial, it has been under study for many months or years.

When planning a clinical trial, an investigator (usually a physician) must write a detailed plan that outlines both the background and purposes of the study and the exact way in which the study will be conducted. This plan or "protocol" details each step of treatment and care for patients in the study, and it must be approved by scientific review boards within the investigator's institution and within the organization that sponsors the study. The protocol for the study ensures that the patients in study receive appropriate treatment and high-quality care and that the research is conducted scientifically.

Clinical trials are conducted in three phases, each aimed at answering a different research question. Each newly developed treatment must go through all three trial phases.

  • Phase I trials: These first studies in people evaluate how a new drug should be given (for example, by mouth, injected into the blood, or injected into the muscle), how often, and in what dose. Phase I trials are the first tests of a new treatment in humans, so they usually include only a small number of patients, sometimes as few as a dozen.
  • Phase II trials: A Phase II trial continues to test the safety of the drug and begins to evaluate how well the new drug works. Like Phase I trials, they often include a limited number of patients.
  • Phase III trials: These studies test a new drug, a new combination of drugs, or a new surgical procedure in comparison to the current standard for treatment. Participants are usually assigned at random either to the standard treatment group or to the new treatment group (this process is called randomization). Phase III trials often enroll large numbers of people and may be conducted at many doctors' offices, clinics, and medical centers nationwide.

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