The term 'clinical trial' is the name given to any study involving the testing of a drug, device or other intervention in humans.
Phase 1: Intended to screen for safety. Testing within a small group of people (20–80) to evaluate safety, determine safe dosage ranges (eg. establishment of the maximum tolerated dose or MTD), and begin to identify side effects.
Phase 2: These trials are designed to provide information on the efficacy of the drug in a defined patient group. These trials are in larger groups of patients (100–300) to see if drug is effective and to further evaluate its safety.
Phase 3: These studies are usually conducted in multiple sites and provide final confirmation of safety and efficacy. Testing with large groups of people (1,000–3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow it to be used safely.
Phase 4: These studies are conducted following registration of the product.