As the name implies, a phase 0 trial precedes "phase I" testing, traditionally the first step in the process of human drug testing.

If the drug hits its intended target without producing significant side effects, the next phase can be expedited. Phase 0 studies expose a small number of people to low doses of a drug over a limited period of time -- seven days or less. The new model, a so-called "phase 0" clinical trial, promises to streamline the costly and time-consuming drug development process, helping to deliver good drugs to people who need them more quickly. In a phase I study, the goal is to determine the best way to administer a drug and the maximum dose tolerated with the fewest side effects. "We want to find out if they're ineffective in the smallest number of patients and get definitive information as cole in the development process as possible," said Dr. Scientists look at how the body reacts to the drug and how it acts in the body.

Doroshow, director of the division of cancer treatment and diagnosis at the National Cancer Institute in Bethesda, Md.