Phase 3 Study

A phase 3 study or phase 3 trial is the last set of preapproval trials to evaluate a new drug before obtaining final [Page 430]approval. Phase 3 studies are generally designed to assess the effectiveness and safety of a new drug or intervention and start to establish its role in clinical practice. They are generally controlled, randomized, comparative studies. Phase 3 studies may have a short follow-up period for evaluation. The main focus of a phase 3 study is effectiveness, but a knowledge of safety is also necessary to fully evaluate the proper role of a new drug or intervention. The more long-term evaluations are part of the phase 4 studies.

Phase 3 studies are usually multicentered, run at more than one site, because they usually involve 1000 to 3000 patients (or more) in the sample for whom the investigational drug or treatment is eventually intended. The larger number of patients allows additional safety data to be obtained. These data often provide much of the information needed for the package insert and product labeling.

In addition to the types of studies just described, which are sometimes referred to as phase 3A studies, there are also phase 3B studies. These are conducted after submission of the New Drug Application (NDA) but before the product's approval and marketing. A drug company may also look to expand indications during the phase 3B period between submission for approval and receipt of marketing authorization. The results of phase 3 trails are usually those that are pivotal in obtaining approval of authorities for the marketing of a drug.

A series of well-designed phase 3 studies are used by the pharmaceutical manufacturer to demonstrate safety and efficacy in a larger population. The results of these studies are considered pivotal to obtaining the approval of authorities for marketing of the drug. Postmarketing phase 4 studies are then undertaken. For example, a phase 3 trial might be titled “A Study of the Safety and Efficacy of Experimental Drug X Compared With Marketed Drug Y in Patients With Disease Z.”