categorized as Phase I to IV trials. They are generally described as follows:
Phase I (small number of participants, normally between 6-10 healthy volunteers, or very sick patients for whom treatment options are lacking)
Phase I studies are designed to allow scientists and medical doctors to understand what effects an investigational compound has in human subjects. The goal is to study what happens to the compound in the body from a safety and tolerability point of view after it is swallowed, injected or infused. .Study participants are monitored for the occurrence and severity of any side effects that they may experience.
Phase II (once the initial safety of the study drug has been confirmed in Phase I trials, Phase II trials are performed on larger groups of patients, generally 20-300 depending on the type of disease)
Phase II studies are designed to begin to evaluate the safety and efficacy of an investigational medicine in patients, and often used to determine if different dosages of the treatment have different effects. The patients are given various doses of the compound and closely monitored to compare the effects and to determine the safest and most effective dosing regimen. In many instances, multiple Phase II studies are conducted to test the compound in a variety of patient populations or indications.
Phase III (carried out on large patient groups, 300–3,000 or more depending upon the disease being studied)
Phase III studies are designed to confirm the safety and efficacy of an investigational medicine. Large numbers of patients are generally involved in order to adequately confirm benefit and safety. These studies, as in the earlier phases, may involve one or more ‘treatment arms’, which allow for the safety and efficacy of the new investigational drug to be compared to other available treatments, or to be tested in combination with other therapies. Information obtained from Phase III studies is used to determine how the compound is best prescribed to patients in the future.
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Phase IV (also known as Post-Marketing Surveillance Trials)
Phase IV studies take place after the medicine has received regulatory approval (market authorization) and are designed to provide broader efficacy and safety information about the new medicine in large numbers of patients, subpopulations of patients, and to compare and/or combine it with other available treatments. These studies are designed to evaluate the long-term effects of the drug. Under these circumstances, less common adverse events may be detected.
