The drug development process moves forward in phases:
Phase 1 Trial – Testing the safety of a drug
Phase 1 trials are conducted to determine a drug’s basic safety and how it affects the body. These early trials typically involve a small number of patients who are often healthy volunteers; the exception being oncology studies. Phase 1 trials typically last several months allowing researchers to give enrolled participants increasing doses of the drug, monitor their reactions and identify side effects. Drugs that meet safety standards often move on to Phase 2 trials.
Phase 2 Trial – Determining whether a drug works
These trials involve more people, usually up to 100, who all share the health condition the new drug is targeting. Lasting up to two years, Phase 2 trials are conducted to find out if the new treatment works well enough to warrant testing in larger numbers. Phase 2 trials also seek to learn more about side effects and the most effective dose. Because different people react differently to drugs, every stage includes careful safety monitoring for any adverse side effects.
Phase 3 Trial – Confirming how well a drug works
Phase 3 trials compare the new drug with the standard accepted treatment to see whether it is more effective or causes fewer side effects. Phase 3 trials are large-scale trials – often involving thousands of patients in many different sites and countries – that can extend over several years.
The more testing a drug goes through, the more confident we can be that it’s safe and effective. For research purposes, Phase 3 trials are usually randomized – that means that some people get the new drug and others get the standard therapy or an inactive substance that looks like the tested drug (called a placebo). After Phase 3 trials are completed, drug developers submit all their findings to regulatory authorities for drug approval.
Phase 4 trials – Proving a drug in the real world
Even after a drug is approved and put on the market, studies often continue to monitor its long-term safety and effectiveness in real patients outside the controlled environment of the clinical trial. These tests are also called post-marketing studies or surveillance studies. Other tests may be conducted to explore new, different reasons to use the drug.