Biotechnology and Pharmaceutical Investor Research
Phase II Trials


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Phase II (or Phase 2) clinical trials are the second step in a series of trials on human beings required by the FDA (Food and Drug Administration) prior to the approval of new drugs or therapies.

Because Phase I trials are nearly meaningless to the value of a company's stock, serving mainly to screen out drugs that are too toxic to use, Phase II results are the first solid indicator of potential for ultimate approval.

Phase II trials are about safety, effectiveness, and science. Phase II trials are usually conducted in human subjects who have the disease or condition the drug or therapy is designed to help. Volunteers are closely monitored for side effects and adverse reactions.

This phase of testing helps determine the common short-term side effects (adverse reactions) and risks associated with the drug and their statistical prevalence. Phase II studies typically include control groups (similar patients who are given a placebo) and are conducted with a relatively small number of patients, usually involving 100 to 300 people.

Phase II trials have goals, called endpoints, that the researchers agree upon in advance with the FDA. Usually meeting the endpoints results in progressing to Phase III, and failing to meet the endpoints means dropping the drug or having to do another Phase II trial. Sometimes Phase II trials are separated into A and B sections, for testing safety and effectiveness. Sometimes several Phase II trials are done to determine which particular disease target or subset of patients should be enrolled in Phase III studies.

It is also important to note that safety concerns do not go away just because a Phase II trial has good results and a Phase III trial is planned. Even drugs that have been approved for marketing have been recalled or had their indications limited because of adverse effects discovered when the drug was given to larger numbers of patients.

However, if a drug is shown to be effective in a Phase II trial and has an acceptable level of safety, this is a good indicator that the drug may be successful in Phase III trials. Investors should be aware that a result being statistically significant in a smaller (Phase II) trial does not guarantee that it will still be statistically significant in a larger Phase III trial. However, the odds of doing well in Phase III are considerably improved by a good Phase II outcome.

More information:

FDA on Phase II