What is Phase II
clinical trial? Phase II studies test the efficacy of a drug or device. This second phase of testing can last from several months to two years, and involves up to several hundred patients. Most phase II studies are randomized trials where one group of patients receives the experimental drug, while a second "control" group receives a standard treatment or placebo. Often these studies are "blinded" which means that neither the patients nor the researchers know who has received the experimental drug. This allows investigators to provide the pharmaceutical company and the licensing authority with comparative information about the relative safety and effectiveness of the new drug. About one-third of experimental drugs successfully complete both Phase I and Phase II studies. Phase
II Studies are sometimes divided into Phase IIA and Phase IIB
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Phase
IIA is Specifically designed to assess dosing requirements
(how much dose should be given).
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Phase
IIB is specifically designed to study efficacy (how well the
drug works at the prescreibed dose(S)).
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What is Phase III
clinical trial?
Phase III studies involve randomized and blind testing in several hundred to several thousand patients. This large-scale testing, which can last several years, provides the pharmaceutical company and the licensing authority with a more thorough understanding of the effectiveness of the drug or device, the benefits and the range of possible adverse reactions. 70% to 90% of drugs that enter Phase III studies successfully complete this phase of testing. Once Phase III is complete, a pharmaceutical company can request licensing authority for approval to market the drug.
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