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The Five Phases of Clinical Trials

Erol Onel

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As vice president of Heron Therapeutics, Erol Onel works with a team responsible for seeking approval for a long-acting non-opioid pain drug. Possessing more than a decade of experience in clinical research, Erol Onel has successfully engaged with the US Federal Drug Administration on several occasions and is familiar with all phases of a clinical trial, as outlined below.

1. Phase 0: The purpose of phase 0 trials is to learn how human beings process a drug and how it affects the body. To gather this information, small groups of individuals are given small doses of the new drug.
2. Phase I: After researchers know how humans are affected by a new drug, they begin studying the drug’s safety. Testing may take several months and often includes groups of between 20 and 100 volunteers. Dosage sizes are changed during phase I trials to assess side effects. Roughly 70 percent of new drugs pass this phase.
3. Phase II: In this phase of clinical trials, researchers examine the efficacy of the new drug. Phase II trials often include several hundred volunteers and last between several months and two years. They are designed to include a control group, which receives a placebo or standard treatment, and an experimental group, which is given the new drug. Many phase II trials are blind and randomized.
4. Phase III: The use of blind and randomized testing continues into phase III trials, but the participant pool increases to include several thousand patients. Phase III trials take several years to complete. Data collected through these trials is often sent to the FDA to assist with the approval process.
5. Phase IV: Also known as post-marketing surveillance trials, phase IV tests are done after the FDA has approved a new drug for consumer sale. Studies in this stage focus on comparing the new drug to other drugs in the market, monitoring long-term effectiveness, and analyzing cost-effectiveness.