• ID of Utrophin Brake Raises DMD Treatment Hopes
• Gene Transfer Using Herpes Virus Transporter Helps Mice With Friedreich's Ataxia
• Z-Shaped Construct Has Potential for Blocking Hazardous Genes
• Research Points to New Directions In Inclusion-Body Myositis Treatment
• Caught in the Crossfire?
• Toxic Buildup
• Modified Cells to the Rescue
• Delivering Genes Via Bacteria May Become an Option
• Clinical Trials and Studies
• Researchers Will Test High-Dose Vitamin C in CMT1A
• New Myozyme Studies to Provide More Data on Pompe's Treatment
• Insmed Planning Additional Studies of Iplex in Myotonic Dystrophy
• Steroid-Treated Boys Walk Longer, Have More Leg and Vertebral Fractures
• Longer Survival in DMD With Ventilation, Scoliosis Surgery

ID of Utrophin Brake Raises DMD Treatment Hopes

by Margaret Wahl

MDA-supported researchers at the University of Pennsylvania and the University of Ottawa report finding a molecule that keeps the muscle protein known as utrophin confined to one small area of a muscle fiber and thereby limits its potential as a therapy for Duchenne muscular dystrophy (DMD). Releasing this brake by blocking this molecule could become a strategy for treating the disease.

MDA grantee Tejvir Khurana at the University of Pennsylvania and colleagues, including MDA-supported Bernard Jasmin at the University of Ottawa, say a compound called ERF (ETS-2 repressor factor) helps regulate utrophin production in mature muscles.

The utrophin protein is very similar in structure to the dystrophin protein, which is missing in boys with DMD. However, its instructions are in a gene on chromosome 6, in contrast to those for dystrophin, which are on the X chromosome and are defective in DMD-affected animals and people. The utrophin gene isn’t affected in DMD.

During fetal development and up until shortly after birth, utrophin is produced (expressed) all around muscle fibers. But as the fibers mature, most of the utrophin is replaced by dystrophin, except in the small areas where the nerve and muscle fibers meet, called the neuromuscular junctions.

Figuring out a strategy for returning utrophin expression to the whole muscle fiber has been a goal of MDA research ever since experiments in mice in the 1990s showed that utrophin can, at least in part, compensate for dystrophin deficiency.

Increasing utrophin’s presence might in some situations be easier than replacing or repairing dystrophin genes. And, utrophin would be highly unlikely to cause an unwanted immune response, since boys with DMD already make some utrophin.

The investigators, who published their findings online May 16 in Molecular Biology of the Cell, say ERF apparently interacts with a molecular switch (promoter) to repress the activation of utrophin instructions. When they reduced ERF levels, utrophin promoter activity and utrophin expression outside the neuromuscular junctions increased.

“Together, these studies suggest ‘repressing repressors’ as a potential strategy for achieving utrophin upregulation (increase) in DMD,” the researchers say.

Gene Transfer Using Herpes Virus Transporter Helps Mice With Friedreich's Ataxia

Scientists in Madrid have successfully treated mice with Friedreich's ataxia (FA) by transferring genes for the frataxin protein into their nervous systems, using a viral transporter.

FA is a progressive disease that causes weakness and incoordination. It results from mutations in the gene for frataxin, a protein needed for energy production in nerve cells.

When Filip Lim and colleagues at Autonoma University of Madrid injected human frataxin genes, encased in modified herpes simplex viruses, into the brainstems of frataxin-deficient mice, they found they had restored the animals’ ability to stay on a rotating rod.

Their functional recovery was “surprisingly complete,” the researchers say in their report, published in the June issue of Molecular Therapy.

They note that humans who are carriers of FA but have no symptoms of the disease only have about 40 percent of the normal level of frataxin, indicating that high-level frataxin restoration probably isn’t necessary.

Delivery of genes to the nervous system is perhaps the most challenging form of gene therapy, but the modified herpes simplex virus appears promising as a vehicle.

The investigators note that it naturally targets nerve cells when it causes an infection; that it’s large enough to carry a lot of therapeutic DNA; and that it doesn’t integrate into any of a cell’s chromosomes, which makes it safer than viruses that do.

“All therapeutic strategies aimed at alleviating neurodegeneration in FA and many other neurological conditions have failed so far, emphasizing the need to explore other options, such as gene therapy,” the authors write.

They also say new mice, developed by Mark Pook at Brunel University in the United Kingdom, and colleagues, will provide better tools for future studies, because they have genetic mutations exactly like those that cause human FA and have a disease that more closely mimics the human one.

Z-Shaped Construct Has Potential for Blocking Hazardous Genes

Scientists at the Karolinska Institute in Stockholm, Sweden, have developed a new way to block harmful genes, adding to an expanding array of gene-silencing strategies that have potential for treating diseases in which something toxic, rather than something missing, is the underlying problem. (See “Defensive Action,” January-February). Most dominantly inherited conditions, in which a genetic flaw from only one parent is needed to cause symptoms, are in this category.

Rongbin Ge and colleagues, who published their results in the June issue of the FASEB (Federation of American Societies for Experimental Biology) Journal, have created a Z-shaped construct that sticks to DNA and thereby specifically silences genes in cells grown in laboratory containers. Other silencing strategies are aimed at blocking RNA, the genetic “message” derived from DNA instructions (genes). The cell uses the RNA message to create protein molecules.

The Swedish scientists have dubbed their compound Zorro locked nucleic acid (LNA) and say it sticks to each of the two strands that make up a typical stretch of DNA, as the DNA begins to “unzip” just before RNA synthesis.

RNA silencing will probably be an effective treatment for some conditions, in which only the protein product of the gene is toxic. But for disorders in which the RNA itself appears to be toxic, blocking DNA instructions is likely to be a better option. Types 1 and 2 myotonic dystrophy (MMD) are in this category.

“It’s still very early days when it comes to this technology,” said study co-author C.I. Edvard Smith, “but we are working hard to find out more about its potential. At least in the test tube and following microinjection into cells, we believe that the Zorro LNA construct has strand-invading properties. However, we still have a long way to go before we know about the clinical efficacy of this potential drug.”

Researchers Will Test High-Dose Vitamin C in CMT1A

An MDA-supported multicenter trial of high-dose ascorbic acid (vitamin C) in the type 1A form of Charcot-Marie-Tooth (CMT) disease, initiated by Richard Lewis, associate chairman of the Department of Neurology at Wayne State University in Detroit, has begun patient enrollment. The study is being conducted at three sites: Wayne State University in Detroit; the University of Rochester (N.Y.) Medical Center; and Johns Hopkins University in Baltimore.

Type 1A CMT is a disorder of nerve fibers that affects sensation and movement, particularly in the forearms, hands, lower legs and feet, and it results from a partial duplication of chromosome 17. This partial duplication causes overproduction of a protein called PMP22.

Studies in mice with CMT1A have shown that high doses of ascorbic acid can lead to partial recovery of strength and reduction of activity of the PMP22 gene in the animals.

A brief report of a small pilot study at the American Academy of Neurology meeting in May said that ascorbic acid at 5 grams a day was toxic in six of 12 people with this disorder. The trial wasn’t large enough or long enough to detect efficacy of the vitamin. (See Researchers Share New Findings at AAN Meeting,” in “Research Updates,” July-August.)

Cory Toth, assistant professor of neurosciences at the University of Calgary in Canada and principal investigator on the pilot study, said he’s very much in favor of a larger trial.

“Although a number of patients did not tolerate the high dose of vitamin C given, this does not mean that the use of different vitamin C preparations, or administration schedules, or lower doses of vitamin C (which may still be effective), would not be tolerated,” Toth said in a letter to MDA.

“I would like to emphasize that the results of my small study should not, in any way, prevent larger scale studies in order to find a therapy for this disabling disease which is currently without therapy.”

Toth also said he has talked with the U.S. investigators and that they’ll use smaller doses of ascorbic acid and watch carefully for side effects, which were mainly gastrointestinal.

Commenting on the pilot study findings, Lewis said, “It is impossible to discern anything about the effectiveness of high-dose vitamin C from a small study of 12 people for one year.

“Research done by ourselves and others demonstrates that disease progression in CMT1A is so slow that it would take at least 100 patients followed for two years in a carefully designed study to determine potential benefits from vitamin C or any other agent. We are excited that our study to determine efficacy has now started.”

For more information about the new study, contact Lisa Rowe at (313) 577-1689 or lrowe@med.wayne.edu, or see “High-Dose Ascorbic Acid Treatment of CMT1A” in the Clinical Trials section of the MDA Web site.

New Myozyme Studies to Provide More Data on Pompe's Treatment

Genzyme, the Cambridge, Mass., biopharmaceutical company that developed Myozyme, will continue to test this laboratory-engineered enzyme, which compensates for missing acid maltase, in people with Pompe’s disease (acid maltase deficiency).

A new study will test higher and more frequent dosing regimens of Myozyme in 12 patients who are at least 6 months old and have shown less than optimal improvement on the standard Myozyme regimen, which is an intravenous infusion every other week of 20 milligrams per kilogram of body weight.

Contact Deya Corzo, senior medical director at Genzyme, at (800) 745-4447 or (617) 252-7832, or write to medinfo@genzyme.com.

The company is also planning a study to evaluate the long-term growth and development of patients with infantile-onset Pompe’s disease treated with Myozyme before they’re a year old.

Insmed Planning Additional Studies of Iplex in Myotonic Dystrophy

Insmed Inc., a Richmond, Va., biotechnology company, is planning to extend studies of its experimental drug Iplex in adults with type 1 myotonic dystrophy (MMD1). Iplex is based on the natural compound insulin-like growth factor 1 (IGF1), which may improve muscle mass and strength.

Assessments will include measurements of muscle wasting, weakness, pain, fatigue, gastrointestinal disturban-ces and cognitive impairment. Insmed requests that patients contact the company through a physician, who should send an e-mail to clinicaltrials@insmed.com.

Steroid-Treated Boys Walk Longer, Have More Leg and Vertebral Fractures

Boys with Duchenne muscular dystrophy (DMD) who were treated daily for at least a year with corticosteroid medications walked longer and were less likely to develop a spinal curvature (scoliosis), but they were more likely than untreated boys to experience fractures of their vertebrae and long leg bones.

Neurologists Jerry Mendell and John Kissel, co-directors of the MDA clinic at Ohio State University Medical Center in Columbus, with Wendy King, physical therapist associated with the clinic, and colleagues, published these results May 8 in Neurology, after reviewing the records of 143 patients seen at the MDA clinic between 2000 and 2003.

Seventy-five of the boys took prednisone at 0.75 milligrams per kilogram per day or deflazacort at 0.9 milligrams per kilogram per day, and 68 boys either had never taken corticosteroids or received only brief, low-dose treatment.

The treated boys walked independently for an average of 3.3 years longer than did the untreated boys.

Nearly three times as many untreated compared to treated young men developed a spinal curvature serious enough to be referred for surgery. The authors speculate that the lower frequency of scoliosis in the treated group may reflect stronger muscles supporting the spine and/or prolonged walking. They said they couldn’t determine whether corticosteroids truly prevent scoliosis or just delay its onset.

About a third of the treated boys experienced fractures of the vertebrae related to compression in the spine, whereas no untreated boy did. The authors note, however, that about 80 percent of these fractures were discovered incidentally during scoliosis screening and not because of pain reported by patients. The authors say the increased risk of compression fractures could be related to more walking and greater body weight.

Almost a third of the boys in the steroid group had a fracture of a long leg bone (femur), compared with only 7 percent of the untreated boys. However, fractures of the upper arm bone (humerus) occurred in only 9 percent of the steroid-treated boys compared with 25 percent of the untreated.

Interestingly, many of the boys in this study, whether steroid-treated or not, were smaller than average for their age and had bones that were abnormally narrow and below average in density, suggesting that other factors besides corticosteroids may influence the skeleton in DMD.

The investigators note, however, that osteoporosis (bone thinning) and damage to the bones are important considerations when corticosteroid treatment is undertaken. They prescribe calcium supplements for their patients and monitor them with bone density scans. (See “Not Always Smooth Sailing: Charting a Corticosteroid Course,” May-June.)

Velimir Matkovic, a physician in the Physical Medicine and Rehabilitation Department at OSU who was part of this study, now has an MDA grant to study skeletal development in boys with DMD and its relationship to steroid treatment.

Longer Survival in DMD With Ventilation, Scoliosis Surgery

A British study has found that adding spinal surgery to nighttime assisted ventilation in Duchenne muscular dystrophy (DMD) improves median survival from 22.2 years to 30 years. (“Median” survival was calculated as the time at which half the study subjects remained alive.)

Michelle Eagle at the University of Newcastle and Newcastle Upon Tyne Hospitals Trust, and colleagues, conducted the study by analyzing the records of boys with DMD born between 1970 and 1990 and followed at the Newcastle Muscle Centre.

They reviewed the records of 27 boys who had surgery to correct a spinal curvature and used noninvasive (nontracheostomy) ventilation during the night; 13 who used ventilation but didn’t have spinal surgery; and 35 who received neither treatment.

The median survival time for the first group (surgery and ventilation) was 30 years; for the second group (ventilation only), it was 22.2 years; and for the third group (neither intervention), it was 17.1 years.

“Our current results suggest that the combination of spinal correction and the provision of home nocturnal ventilation have an additive effect on survival for boys with DMD with a progressive scoliosis [spinal curvature] and respiratory failure but without severe progressive cardiomyopathy [cardiac muscle disease],” the investigators say in their report, published in the June issue of Neuromuscular Disorders.

They say the two interventions together enhance longevity to a greater extent than either one alone.

The researchers also note that longer survival in DMD since the 1960s is the result of many factors. Among them are better management of chest infections with antibiotics beginning in the 1970s and 1980s; and, starting in the 1990s, better monitoring of respiratory function and the introduction of home nocturnal ventilation, wider use of  surgery to correct spinal curvatures, and a lower threshold for both detection and treatment of cardiac muscle disease.

They note that the recent introduction of corticosteroids (the prednisone family of medications) to the standard treatment of boys with DMD improves strength and prolongs walking, but they say it’s too early to tell whether steroids will also affect survival.