A clinical trial is a research study performed in humans to tackle any number of questions related to disease screening, diagnosis and treatment. Treatment trials determine if a new drug, combination of drugs, or therapy is both safe and effective for treating a disease or medical condition. All clinical trials are conducted using a set of criteria called a protocol. A protocol describes the types of patients who may enter the study, the schedules of tests and procedures, drugs, dosages and length of the study.
Clinical trials are conducted in phases. The trials at each phase have a different goal and together will provide valuable information for evaluating a new treatment.
PRECLINICAL: Before a drug can be given to a human, laboratory studies are conducted to demonstrate safety in humans and the likelihood of the drug to combat the disease.
PHASE 1 TRIALS: The primary goal of a phase 1 study is to assess the drug's safety, usually in healthy volunteers. Researchers will test the drug in a small sample of individuals (20 - 80) for the first evaluation of the drug in a human. As part of safety, these initial studies will determine a safe dosage range and identify side effects.
PHASE 2 TRIALS: The primary goal of phase 2 controlled clinical trials is to evaluate the effectiveness of the drug at various dosages for a particular indication or indications in patients with the disease or condition under study and to determine the common short-term side effects and risks. Phase 2 trials usually include a larger group of individuals (100 -300) than the phase 1 trials. Numerous phase 2 trials are often conducted in the early stages of testing a new drug.
Most phase 2 trials are randomized trials in which one or more groups of individuals will receive the experimental drug and another group of individuals will be the “control” group and receive a placebo or standard of care. Blinded trials mean that neither patients nor the researchers know who is receiving the experimental drug.
PHASE 3 TRIALS: The primary goal of phase 3 trials is to confirm the drug's effectiveness, monitor side effects, compare with standard of care, and record information that will allow the drug or treatments to be used safely. Phase 3 trials include a large number of individuals, ranging from several hundred to thousands.
PHASE 4 TRIALS: After the drug receives FDA approval for use, phase 4 trials or post-marketing studies can be conducted to provide additional information including the drug's risks, benefits, and optimal use.