Clinical Trials: What You Need to Know

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Phase 0 clinical trials: Exploring if and how a new drug may work

Even though phase 0 studies are done in humans, this type of study is not much like the other phases of clinical trials. It’s included here because some cancer patients may be asked to take part in these kinds of studies in the future.

Phase 0 studies are exploratory studies that often use only a few small doses of a new drug in each patient. They test to find out whether the drug reaches the tumor, how the drug acts in the human body, and how cancer cells in the human body respond to the drug. The patients in these studies might need extra biopsies, scans, and blood samples as part of the study.

The biggest difference between phase 0 and the later phases of clinical trials is that there’s no chance the volunteer will be helped by taking part in a phase 0 trial. Because drug doses are low, there’s also less risk to the patient in phase 0 studies compared to phase I studies.

Phase 0 studies help researchers find out whether the drugs do what they are expected to do. If there are problems with the way the drug is absorbed or acts in the body, this should become clear very quickly in a phase 0 clinical trial. This process may help avoid the delay and expense of finding out years later in phase II or even phase III clinical trials that the drug doesn’t act as it was expected to based on lab studies.

Phase 0 studies are not yet being used widely, and there are some drugs for which they wouldn’t be helpful. Phase 0 studies are very small, often with fewer than 20 people. They are not a required part of testing a new drug, but are part of an effort to speed up and streamline the process.

Here’s how a phase 0 study might work:

Lucia had several courses of chemotherapy after her cancer spread. The chemo helped at first, but the cancer came back again. After talking with her doctor, Lucia does not think she wants any of the current options that are offered for standard treatment. She’s interested in a clinical trial that might help her. She has found a phase III clinical trial of a new drug, but the study she wants to be in doesn’t start enrolling for nearly 4 weeks.

Then, her doctor tells her about a new substance that has been studied and tested in the lab, including animal studies. It looks like it might help her type of cancer. Phase I human studies have not started, but a phase 0 study of the new drug, called “EX-0,” is available. This study will only take a few days and isn’t expected to have many side effects, because patients will be getting very small doses of the drug. Lucia learns that extra blood samples and biopsies will be needed to find out how quickly the drug goes into her blood and what it does with the tumor. She decides that, even though this will not help her personally right now, it might help someone else in the future. She knows that other members of her own family have had this type of cancer, and she wants them and others to have as many good options as possible.

When she meets with the research coordinator, he explains in detail how the study will work. He goes out of his way to make sure that Lucia understands that the study cannot help her at all. Any information gained from the study would help the drug maker know whether they should continue with human studies. Lucia makes sure that taking the Phase 0 study drug will not keep her from going into the phase III study next month. She also asks more questions about what’s known about side effects that happened in animal studies, and what else she might expect. Lucia decides that she is willing to take these risks, so she signs the consent form and finds out which days she will need to be at the study center over the next 2 weeks. She answers some medical questions and signs release forms to get her medical records from her doctor and the hospital where she was treated. The staff draws some blood and they plan to start testing next week.


Last Medical Review: 09/21/2012
Last Revised: 09/21/2012