Phases of Clinical Trials

Clinical development studies research the safety and efficacy of an investigational new drug in humans through three phases.

Phase I

In this phase, the safety of a drug candidate is assessed in a small group of healthy individuals, as well as the metabolism of the drug in the human body. Furthermore, the incidence and presence of any side-effects resulting from dose changes are studied.

Phase II

These clinical trials are conducted in a limited patient population and are designed to evaluate the efficacy of the drug candidate for the specific, targeted indication as well as to further identify possible adverse effects and safety risk and to determine dose tolerance and optimal dosage.

Phase III

In Phase III clinical trials, a drug candidate is tested in large patient populations. In this phase, the pharmaceutical company (sponsor) and regulatory agencies aim to achieve insight into the drug candidate’s efficacy and the scope of its related adverse reactions. Most Phase III studies are both randomized and blinded, and they are typically of long duration. Some Phase III trials may last for several years. Upon successful completion of Phase III trials, the sponsor can request marketing approval through the appropriate regulatory agency. For example, to receive marketing approval in the United States, a sponsor submits a New Drug Application (NDA) to the FDA. Within the European Union, a Marketing Authorization Application must be obtained from the European Medicines Agency (EMEA).

In orphan indications, the numbers of patients involved in Phase II and III studies are much smaller than in traditional drug development.