Research and Drug Development for Huntington's Disease
Clinical Trials: Phase II
The main purpose of phase II is to gather preliminary evidence as to whether the potential drug helps participants with the relevant disease. Phase II trials are also used to determine the common short-term side effects and risks associated with the drug in patients with the relevant disease. The participants in these studies, anywhere from 100-300 affected individuals, are usually closely monitored. Rare side effects will probably not be seen because the phase II participant population is too small.
Phase II trials are sometimes randomized, which means that half the participants in the study are chosen at random to receive the old or "standard" treatment, and half are chosen to receive the new treatment. Furthermore, these trials are often double-blinded, which means that neither the participants nor the clinical researchers know who has gotten which treatment. This eliminates bias on the part of the researchers, both in terms of deciding who would get the new treatment, and in observing or measuring the results.
A successful phase II trial is necessary to convince the scientists and physicians conducting the clinical trials that it is worthwhile to move into a phase III trial, which is very costly and time-consuming. Scientists must look at various measurable factors (outcomes) to decide whether the phase II trial was successful. If the drug being tested seemed to reduce or improve symptoms, nerve cell loss, tumor size, blood pressure, or any other relevant outcome in comparison with the control group, they will consider proceeding with a phase III trial.
A phase II trial can take up to two years, and even if successful, does not guarantee that a phase III trial will also be successful. It is important to note that only about 30% of all potential drugs make it through phase I and phase II trials. Even if the drug does make it this far, many problems may become evident once it is used in a larger participant population. This uncertainty is simply one of the many risks that all drug developers and clinical researchers take during research and development.
HD and Phase II Clinical Trials
A few different HD treatments are being studied in phase II trials as of April 2007. The Huntington's Study Group is sponsoring a trial to look at the long-term safety and efficacy of minocycline in reducing symptoms for patients with HD. This phase II study is being conducted at multiple centers across the US, and is enrolling about 100 participants. For more information on this study, please click here.
Another phase II trial is being conducted at the University of Iowa to examine the effects of atomoxetine on daily activities such as attention and focus, thinking ability and muscle movements in subjects with early HD. This treatment is mostly aimed at relieving the cognitive symptoms of HD, and the drug has been successful in treating similar symptoms in patients with ADHD. The trial is currently recruiting participants; for more information, please click here.
It is important to remember that only a small percentage of all clinical trials are successful. In 2001, a phase II trial was conducted to test the effectiveness of the drug amantadine for the treatment of chorea associated with HD. Amantadine blocks the action of glutamate, which is thought to be implicated in HD toxicity. For more information on the role of glutamate in HD, please click here. The drug has had some success in relieving symptoms in patients with Parkinson's disease. However, the phase II clinical trial indicated that, in fact, amantadine had little effect on Huntington's chorea, and so it was not continued into a phase III trial. For more information on this trial, click here.
Last Modified: 05/22/2009
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