In Contents 6-2: How Does a Clinical Trial Work?, we learned a little about clinical trials. The following Reading gives us more information about the three phases of clinical trials and is excerpted from Enroll-HD.
Reading: The Phases of Clinical Trials
How are they structured?
Drugs are almost always first tested in animal models to get a sense of what the correct dosage should be, to look for dangerous side effects, and to get hints about whether it might help people with the disease.
Phase I
The first step in human testing is Phase I, which mainly looks at the safety of a potential drug. The drug is given to a small number of healthy people at various doses for a short time to make sure they don’t develop any serious side effects.
Phase II
About 70 percent of all studies make it to the next step, a Phase II trial. Usually, people who have the disease in question are given the drug over a period of weeks or months. Phase II trials are designed to further evaluate safety—to make sure that the drug doesn’t cause problems in a larger group of people who actually have the disease—and to look at what dose can be given to people. Often a Phase II trial is also designed to give an early hint about efficacy, meaning whether or not it is effective—does the drug show signs that it might be beneficial to patients?
Many trials are very choosy about which people will be included in this stage. This is so that the analysis won’t be clouded by other factors—they want to try to isolate the effect of the drug, and keep everything else the same. Trials often seek volunteers in a narrow age range with a specific set of symptoms, and no other health problems.
This type of trial is almost always randomized and blinded, meaning that the trial participants are randomly assigned to treatment groups, with some given the active treatment at different doses and others given a placebo—a sugar pill or something else known to be inactive—without anyone knowing what kind of treatment they are getting (this is the ‘blinded’ part). This is to prevent people’s hopes or subconscious biases from influencing the results. Even the staff who run the study don’t know which people are getting the experimental drug—only the people who analyze the data know which is which.
Phase III
About one third of all drugs make it to a Phase III trial. This is the real acid test, when the drug or treatment is given to a larger and more diverse group of people. More than half of the drugs that have made it this far are successful in Phase III testing. The upshot is that the overall success rate for drugs that begin clinical trials is only about 20 percent.
References
How Does a Clinical Trial Work? (n.d.). Retrieved July 4, 2017, from https://www.enroll-hd.org/what-is-a-clinical-trial
Exercise
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