Phase III clinical trials involve 300 to 3,000 volunteers and last 1 to 4 years. They are designed to further assess a drug's safety, efficacy, and effectiveness. Only about 25-30% of drugs proceed from Phase II to Phase III. Phase III trials provide most of the safety data needed for regulatory approval and marketing. If results are satisfactory, trial findings are compiled into a regulatory submission for review by health authorities. Approximately 50% of drug candidates either fail Phase III trials or are rejected by regulatory agencies.
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