Phases of development
Pre-clinical: Promising new agents first undergo pre-clinical testing in animals and are designated by the U.S. Food and Drug Administration (FDA) as an Investigational New Drug if the pre-clinical data is positive. Research then moves on to clinical testing in people through phase I, II and III clinical trials.
Phase I: Is it safe? This phase determines how the drug works in healthy study participants. Researchers examine the mechanism of action (how the drug acts), safety and side effects. The overall safety of the medication in patients is not established at this phase.
Phase II: Is it effective? This phase determines if a drug's clinical activity may be beneficial against a particular disease or condition. A drug reaches phase II only after the FDA has reviewed the phase I data and concludes the drug is safe enough for patients to proceed with further testing. At this point, a larger group of patients, such as more than 100, is enrolled and rating scales specific to a condition or disease are used to record data.
Phase III: Can it be used in more patients? At this point, the medication is ready to be studied in a larger population, such as 1,000 patients, with even more advanced rating scales and clinical measures. In recent years, the trend has been to include "real world" measurements—for example, how patients' activities of daily living are improving.
Phase IV: Can it be used in different types of patients? At this phase, the FDA has already granted approval, but the study may identify an additional use or gather more safety information from a larger group of patients. These studies can also provide information on how the drug may be best used or best combined with other treatments. Sometimes phase IV studies establish effectiveness in a subgroup of patients, such as patients over age 65.
New Drug Application (NDA): Filed for non-biologics with the FDA after completion of human clinical trials. An NDA usually contains hundreds of pages of scientific information and clinical data.
Biologic License Application (BLA): Filed for biologics with the FDA after completion of human clinical trials. Biologic drugs for use in humans must be shown to be safe, pure and potent.