Huntington's disease is a genetic, progressive, neurodegenerative disorder characterized by the gradual development of involuntary muscle movements affecting the hands, feet, face, and trunk and progressive deterioration of cognitive processes and memory (dementia). Neurologic movement abnormalities may include uncontrolled, irregular, rapid, jerky movements (chorea) and athetosis, a condition characterized by relatively slow, writhing involuntary movements. Dementia is typically associated with progressive disorientation and confusion, personality disintegration, impairment of memory control, restlessness, agitation, and other symptoms and findings. In individuals with the disorder, disease duration may range from approximately 10 years up to 25 years or more. Life-threatening complications may result from pneumonia or other infections, injuries related to falls, or other associated developments.
Huntington's disease is transmitted as an autosomal dominant trait. The disease results from changes (mutations) of a gene known as "huntington" located on the short arm (p) of chromosome 4 (4p16.3). In those with the disorder, the huntington gene contains errors in the coded "building blocks" (nucleotide bases) that make up the gene's instructions. The gene contains abnormally long repeats of coded instructions consisting of the basic chemicals cytosine, adenine, and guanine (CAG trinucleotide repeat expansion). The length of the expanded repeats may affect the age at symptom onset. The specific symptoms and physical features associated with Huntington's disease result from degeneration of nerve cells (neurons) within certain areas of the brain (e.g., basal ganglia, cerebral cortex).
Huntington’s disease is characterized by rapid uncontrollable muscle movements such as tics or muscle jerks (choreiform movements or chorea). This disorder causes a loss of coordination and personality changes. As the disease progresses, the ability to speak may be impaired, memory may fade, and the involuntary jerky muscle movements (chorea) become more severe.
Huntington’s disease runs a ten to 25 year progressive course. As the disorder progresses, the chorea may subside and there may be an absence of movement (akinesia). Dementia gradually develops. Patients with Huntington’s disease are at high risk of developing pneumonia as a result of being bedridden and undernourished.
Huntington’s disease is inherited as an autosomal dominant trait. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.
In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed “dominating” the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.
Huntington’s disease is caused by changes (mutations) of a gene that is located on the short arm (p) of chromosome 4 (4p16.3). Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as “p” and a long arm identified by the letter “q.” Chromosomes are further subdivided into bands that are numbered.
Known as huntingtin, the gene controls the production of a protein found in nerve cells (neurons) throughout the brain. However, the specific function of the huntingtin protein is not known. In individuals with the disorder, the huntingtin gene contains errors in the coded “building blocks” that make up its specific genetic instructions. The instructions within every gene consist of different arrangements of four basic chemicals (nucleotide bases) called adenine (A), cytosine (C), guanine (G), and thymine (T). In those with Huntington’s Disease, the huntingtin gene contains abnormally long repeats of coded instructions consisting of cytosine, adenine, and guanine (CAG trinucleotide repeat expansion). For example, individuals with the disease have over 35 CAG repeats within the huntingtin gene, with most having more than 39. However, individuals without the disorder tend to have about 20 repeats in the gene. Expanded CAG repeats are unstable and may expand further over time and with successive generations. This is thought to be responsible for genetic anticipation, a phenomenon in which an individual with Huntington’s disease may have symptom onset at a significantly earlier age than his or her affected parent. In addition, some researchers suggest that expanded CAG repeats of the huntingtin gene may become more unstable when the gene is transmitted from the father.
The specific symptoms associated with Huntington’s disease are caused by degenerative changes of nerve cells (neurons) within certain regions of the brain, including the basal ganglia and cerebral cortex. The basal ganglia are specialized nerve cells deep within the brain that play a role in regulating movements. The cerebral cortex, the outer region of the brain, is responsible for conscious thought and movement.
About 30,000 people in the United States have Huntington’s disease and another 200,000 are at risk of developing the condition. Symptoms commonly develop between ages 30 and 50. The disease progresses slowly and a person may live for another 15-20 years after the onset of symptoms.
The diagnosis of Huntington's disease may be confirmed by a thorough clinical evaluation, detailed patient history, and a variety of specialized tests. Specialized x-ray studies such as computerized tomography (CT) scanning, magnetic resonance imaging (MRI), or electroencephalography (EEG) may help confirm the diagnosis of Huntington's Disease. During CT scanning, a computer and x-rays are used to create a file showing cross-sectional images of the brain. During MRI, a magnetic field and radio waves are used to create cross-sectional images of the brain. During an EEG, an instrument records electrical activity of the brain. Neuropsychological and/or genetic tests are also used to aid the diagnosis of Huntington's disease.
In August 2008, the Food and Drug Administration (FDA) approved tetrabenazine (Xenazine) for the treatment of the repetitive, involuntary movements (chorea. associated with Huntington's disease. This is the first and only FDA-approved treatment specifically for any symptom of HD. Prestwick Pharmaceuticals, Inc., of Washington, DC, is the U.S. manufacturer of tetrabenezine. The drug has been available in Europe for several years.
Other treatment for Huntington's disease is symptomatic and supportive. There are some treatments that may alleviate various symptoms temporarily. Neuroleptic medication such as haloperidon can partially suppress the involuntary movement, especially in the early stages. Other medication can often help depression and other emotional symptoms. Special high calorie food preparations may help an affected individual maintain weight and avoid choking during the later stages of Huntington's disease.
Genetic counseling will be of benefit for affected individuals and their families. Family members of affected individuals should also receive clinical evaluations to detect any symptoms and physical characteristics that may be potentially associated with Huntington's disease.
Medivation is conducting the Huntington’s disease trial in collaboration with the Huntington Study Group (HSG), a network of more than 250 experienced clinical trial investigators, coordinators and consultants from more than 60 academic and research institutions throughout the United States, Canada, Europe and Australia.
The Phase 2 portion will be conducted at approximately 17 HSG sites in the United States and Europe and is being led by principal investigator Karl Kieburtz, M.D., M.P.H., professor of neurology at the University of Rochester and director of the HSG Clinical Trials Coordination Center.
For more information please contact
Patrick Machado, Chief Financial of Officer Medivation, Inc.,
Jani Bergan of WeissComm Partners, +1-415-946-1064,
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (860) 411-1010
Email: [email protected].nih.gov
For information about clinical trials sponsored by private sources, contact:
In 2006, the U.S. Food and Drug Administration (FDA) granted orphan drug status for the drug candidate, HD-02. This designation followed successful phase I and phase II trials in which HD-02 seemed to reduce the serum 8OH2’dG, a chemical that is found in high levels in patients with Huntington’s disease. It also appeared to elevate brain levels of creatine. HD-02 is produced by Avicena. For information, contact the company at:
The Avicena Group
228 Hamilton Ave., 3rd Floor
Palo Alto, CA 94301
Phone: (415) 397-2880
Fax: (415) 397-2898
Email: [email protected]
The drug ethyl-EPA (Miraxion) is currently (2006) in a phase III trial co-sponsored by its manufacturer, Amarin Neuroscience. Miraxion has FDA “fast-track” status as a potential treatment for the signs and symptoms of Huntington’s disease. Amarin is currently conducting two phase III clinical trials, one in the United States and one in Europe, involving Miraxion. The one in the U.S. is being run by the Huntington’s Study Group (HSG), based at the University of Rochester. For information, call the Huntington Study Group at (800) 487-7671 or go to www.amarincorp.com.
A study of the effects of music therapy on the psychological, somatic, and social symptoms of patients with Huntington’s disease is currently (2006) in a phase I trial at the University of Rochester. This study was launched in 2005.
A May 2004 report from the Department of Medical Genetics at Cambridge University maintains that rapamycin, a drug used to prevent organ rejection after transplants, appears to slow the progress of Huntington’s disease. The report details studies with animals, but studies involving rapamycin and humans now are planned.
Researchers are studying mice with the HD gene and the use of a type of bile acid called TUDCA in possibly preventing the death of brain neurons. However, more research is needed before this approach can be tested in humans.
The National Society of Genetic Counselors has suggested the following classification of genetic test results may be predictive of Huntington’s Disease: tests showing fewer than 26 repeats of the gene suggests that a person will not get Huntington’s Disease; testing showing between 27 and 35 repeats of the gene suggests that a person is unlikely to develop Huntington Disease, but his/her offspring may be at risk; those who test between 36 and 39 repeats of the gene appear to be positive for Huntington’s Disease but with reduced penetrance; and over 40 repeats of the gene are considered positive for Huntington’s Disease.
The FDA Office of Orphan Products Development is sponsoring a randomized, double-blind and placebo-controlled Phase I and Phase II clinical trial of the antibiotic minocycline to determine whether it is safe and tolerable in patients with Huntington’s disease and whether it reduces symptoms of the disease. This trial is being conducted at the Massachusetts General Hospital in Boston. The principal investigator is Merit E. Cudkowicz, MD. More information may be obtained by contacting:
Dr. Merit E. Cudkowicz
e-mail: [email protected]
Study ID Number: FD-R-1968-01
NLM Identifier: NCT00029874
In 2001, the anti-oxidant Coenzyme Q10 received an orphan drug designation by the FDA. Additional study is needed to determine the safety and effectiveness of this treatment for Huntington disease.
In 2000, the FDA granted ethyl eicosapentaenoate orphan drug status for the treatment of Huntington disease.
Information about current clinical trials related to Huntington disease may be accessed through the Huntington Study Group, a non-profit organization of physicians and other healthcare providers in the United States, Europe, Canada, and Australian. The organization’s web site is at: www.Huntington-Study-Group.org.
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FROM THE INTERNET
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