Clinical Trial Phases Explained

Phase 1 Phase 1 studies, also known as "first in humans" are exactly that β€” the first time a new drug therapy, procedure or device is being testing in humans. All testing up to that point has been done on animal models in the laboratory.

Typically Phase 1 studies usually involve between 20 and 100 people who may be healthy volunteers or have the condition being studied. The volunteers stay in the hospital where they are closely monitored. The purpose of a Phase 1 study is to evaluate the safety of a new drug or procedure, and determine any side effects.

70% of all studies pass this phase.

Phase 2 After successfully completing Phase 1, the next step is to test the drug or therapy in a larger group of people. This group of 100-300 volunteers will have the condition being studied.

During a Phase 2 study the dose is escalated, meaning participants are given gradually increasing doses of the medication in order to find the sweet spot β€” the smallest dose that has the greatest effectiveness with the least number of side effects.

33% of all studies pass this phase.

Phase 3 After a successful Phase 2 trial, experimental treatments move onto Phase 3 where they are tested in much larger groups. Typically 1000-3000 participants take part in Phase 3 studies. These studies may test the new drug against a placebo (an inactive lookalike), or compare the drug to another therapy already on the market.

~80% of all studies pass this phase.

Phase 4 Once a drug, procedure or device has gained FDA approval, the research continues in a Phase 4, or Observational, Study. During this phase, the study looks at effects in various populations and monitors for long term side effects. Phase 4 studies are also referred to as "post market surveillance".