Clinical Trial Phases
Phase 1
Phase 1 clinical trials are designed to test a new therapy in a small group of people for the first time to evaluate safety (e.g., to determine a safe dosage range and to identify adverse effects). It can include healthy participants or patients.
Phase 2
Phase 2 clinical trials are designed to study an investigational therapy in a larger group of people to determine efficacy and to further evaluate its safety. It is conducted in participants with the condition or disease under study and will determine common short-term adverse effects and risks.
Phase 3
Phase 3 clinical trials are designed to study the efficacy of the investigational therapy in large groups of patients by comparing the therapy to other standard or experimental therapies as well as to monitor adverse effects, and to collect information that will allow the therapy being studied to be used safely.
Phase 4
Phase 4 clinical trials are conducted after a therapy has been approved and marketed. Many of these studies are designed to monitor effectiveness of a newly approved therapy in the general population and to collect information about any adverse effects associated with widespread use.