The term “clinical research” refers to research that involves human study participants. Clinical research is usually carried out in four phases, as shown in the figure below. Each phase builds on findings from studies conducted in earlier phases.
Several things are important to know.
- Phase 1 and Phase 2 studies are often called “early phase studies”. They do not include many study participants and study participants are monitored very carefully.
- Phase 3 studies are called “late phase studies”. In most cases, the FDA requires findings from two Phase 3 studies before they will consider a drug for marketing.
- Phase 4 studies are conducted AFTER a drug is approved for marketing. They are usually designed to determine if a drug has rare side effects that were missed in the Phase 3 studies.