The Phases of Industry Trials Posted on October 19, 2007 Jeffrey Jonas (bio) provides a brief description of each phase of a drug trial.

Phase I trials are the first trials of a new drug in humans. And these are typically trials in normal volunteers, sometimes in patients with the illness in question, to just get a sense of the dosing of the drug and its basic safety parameters. Once you have that established, you go into Phase II.

And there are different ways to describe Phase II and different labels that are used. But fundamentally, Phase II studies are your early proofs of concept study where you get a sense of whether the drug works and what the dosing is and what its true safety profile is in the target patient population.

Once you have that established, you then go to Phase III studies. These are the studies that are required for approval. And in the U.S., you need typically two positive studies, plus other criteria have to be met for the drug to be approved. And those are your, again, your Phase III trials.

When Phase III is completed, you then put together a new drug application, or an NDA, and that’s submitted to the FDA who then review it to make a determination of whether the drug can be approved or not.

Phase IV does exist. And Phase IV is conventionally termed, “post-marketing.” And these are studies that are either done at the discretion of the company, sometimes mandated by the FDA, sometimes done in agreement with the FDA to look at the study once the drug has been released into the general population for use.

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