Phase III studies aim to be the definitive assessment of the drug under investigation, providing additional safety data, confirming efficacy, and providing the necessary comparative data where an approved therapy is available. These studies are randomized, controlled, multicenter trials enrolling large numbers of patients. The actual number of patients studied can be as large as 3,000 to 5,000, but is also dependent on the number of patients who suffer from the target disease or condition.

Once the comprehensive Phase III studies have been completed, all available evidence, including all preclinical and clinical data collected before and during the clinical trials, is compiled to form the registration dossier. This dossier (e.g., the New Drug Application [NDA] in the US, or the Marketing Authorisation Application [MAA] in the EU) is then submitted to the relevant regulatory authorities in order to obtain approval to market the drug in the respective jurisdictions.

If the regulatory authorities are satisfied that the information provided in the dossier shows that the drug has fulfilled the relevant safety and efficacy criteria, approval to market the drug is granted.