• Gene transfer in LGMD2D mice bodes well for human trial
• Utrophin gene transfer was helpful in mice with severe MD
• Boosting numbers of mitochondria helped myopathy-affected mice
• Immune-system attack on MuSK signaling protein results in MG-like disease
• Experiments suggest potential therapeutic avenue in Friedreich’s ataxia
• First problem in SMA may be where nerve and muscle fibers meet
• Research Administration
• New MDA Clinical Research Network to target ALS, DMD
• PTC Therapeutics and Genzyme will collaborate on PTC124 development
• SMT C1100 development for DMD gets a boost
• Canada OKs idebenone for FA treatment
• Repligen receives MDA support to develop treatments for FA
• Clinical Trials and Studies
• Gene transfer trial under way in LGMD2D
• CellCept disappointing in two myasthenia gravis trials
• Special diet and supplement relieve symptoms in seven with CPT2 deficiency
• Cardiomyopathy with DMD, with BMD, and without MD follow different courses
• UC Irvine professor seeks people with rare muscle and bone disorder
• Parents sought for survey of genetic counseling experiences, knowledge

Gene transfer in LGMD2D mice bodes well for human trial

Experiments conducted in mice suggest gene therapy for type 2D limb-girdle muscular dystrophy (LGMD2D) has the potential to be safe and effective in humans with this serious muscle disease, says an MDA-supported study.

Longtime MDA grantee Jerry Mendell at Ohio State University coordinated the LGMD2D gene transfer study in mice and is also overseeing a human LGMD2D gene transfer trial.

Longtime MDA grantee, neurologist and clinical gene therapy specialist Jerry Mendell of Ohio State University and Nationwide Children’s Hospital in Columbus, coordinated the research team, which included investigators from those institutions and from Harvard Medical School in Boston. Mendell is also overseeing a clinical trial at Nationwide to evaluate the safety of gene transfer in six people with LGMD2D. (See “Gene transfer trial.”)

The investigators, who published their findings July 22 in Neurology, transferred human genes for the alpha-sarcoglycan protein, which is deficient in the muscles of people with LGMD2D, into mice that dont produce this muscle protein.

In contrast to a study published in 2002 that suggested overproduction of alpha-sarcoglycan could have toxic effects in muscle tissue, this new study found intramuscular injections of the alpha-sarcoglycan gene to be safe and effective in the mice.

The authors note that the difference in their results compared to the 2002 study could be related to differences in the gene delivery vehicles, the methods used to purify them or other factors.

They also say, however, that mouse studies can only go so far in answering questions about safety and efficacy for gene therapy in humans and that better understanding of these outcomes awaits the results of the clinical trial.

Utrophin gene transfer was helpful in mice with severe MD

Jeffrey Chamberlain, an MDA grantee at the University of Washington-Seattle, coordinated the utrophin gene transfer research group.

A research team coordinated by MDA grantee Jeffrey Chamberlain at the University of Washington-Seattle found intravascular gene transfer with a miniaturized utrophin gene had roughly the same benefits as intravascular gene transfer with a miniaturized dystrophin gene, in mice missing both utrophin and dystrophin and showing a severe disease resembling Duchenne muscular dystrophy (DMD). The team published its results in the September issue of Molecular Therapy.

Like dystrophin, the protein missing in boys with DMD, utrophin is a muscle protein. But unlike dystrophin, utrophin is produced by boys with DMD. The protein’s similarity to dystrophin has prompted researchers to experiment with its ability to compensate for missing dystrophin. The advantage of using utrophin instead of dystrophin for gene transfer in DMD is that patients’ immune systems are used to “seeing” it and are unlikely to reject it as foreign protein.

Boosting numbers of mitochondria helped myopathy-affected mice

In a mouse model of a mitochondrial myopathy, (a muscle disease involving defects in the cellular “energy factories” known as mitochondria), increasing the number of functional mitochondria improved symptoms and prolonged life, say researchers at the University of Miami.

The investigators, including MDA-supported Carlos T. Moraes and Francisca Diaz, published their findings in the Sept. 3 issue of Cell Metabolism.

In one set of experiments, the investigators developed mice with extra genes for PGC-1-alpha, a metabolism regulator that increases production of mitochondria. In a second set, they gave the mice the drug bezafibrate, which stimulates PGC-1-alpha activity. With both approaches, the mice experienced milder disease symptoms with later onset and longer life spans.

The findings offer a new avenue for research aimed at treating mitochondrial diseases.

Immune-system attack on MuSK signaling protein results in MG-like disease

Destruction of acetylcholine receptors at neuromuscular junctions is a major cause of myasthenia gravis, but interference with the MuSK enzyme can also cause the disease.

Immune-system proteins called antibodies that stick to and destroy an enzyme known as muscle-specific kinase (MuSK) have been identified beyond a reasonable doubt as the cause of myasthenia gravis (MG) in about 10 percent of people with MG.

MDA grantee William Phillips at the University of Sydney (Australia) coordinated a team of researchers at his institution and at Concord (Australia) Hospital to investigate the mechanism by which anti-MuSK antibodies cause MG, publishing results in the June issue of Annals of Neurology.

Since the 1970s, it’s been known that a major cause of MG are antibodies that can destroy acetylcholinereceptors, which are molecular “landing pads” on muscle cells that receive signals from nerve cells. Without adequate numbers of these receptors, signals can’t jump from nerve to muscle, and severe weakness results.

Antibodies are a normal part of the immune system’s defenses against bacteria, viruses and other threats to an organism’s well-being, but when they attack normal tissue, the result is an autoimmune (self-immune) disease, such as MG.

Some patients with autoimmune MG don’t have anti-acetylcholine receptor antibodies, but have antibodies to MuSK, an enzyme important for maintaining the neuromuscular junction, the place where nerve and muscle cells interact and where the acetylcholine receptors are located.

Phillips and co-workers have shown that, when anti-MuSK antibodies from patients with symptoms of MG but no anti-acetylcholine receptor antibodies are injected into healthy mice daily for two weeks, the mice develop an MG-like disease.

When examined microscopically, the neuromuscular junctions of the MuSK antibody-treated mice showed far fewer acetylcholine receptors and an abnormally long distance between the nerve-cell fibers and the receptors.

The scientists say they’ve shown that transfer of human anti-MuSK antibodies to mice results in an MGlike disease and that MG patients who have anti-MuSK antibodies can be certain these are the cause of their disease.

Together with work by others, these experiments provide evidence that MuSK is needed to maintain the health of the neuromuscular junctions, and suggest that boosting the MuSK signal may, in the long term, be another approach to treating MG.

Experiments suggest potential therapeutic avenue in Friedreich’s ataxia

In Friedreich’s ataxia, a deficiency of the frataxin protein changes the way the body regulates iron levels, leading to toxic levels of iron in the cellular mitochondria. Chelators designed to penetrate the mitochondria target the iron accumulation and reduce it.

Experiments examining the effects of iron “chelation,” a process that removes toxic levels of iron from cells, have provided insight to the potential therapeutic value of the process in Friedreich’s ataxia (FA).

A deficiency of the frataxin protein, the underlying cause of FA, changes the way the body regulates iron levels and leads to toxic levels of iron in the cellular “energy factories” known as mitochondria. The disease damages the heart and nervous system.

Iron chelation limits the harmful increase in cell size in the muscle tissue of the heart (“myocardial hypertrophy”) in mice with a disease that closely mimics FA, say researchers at the University of Sydney, New South Wales, Australia.

The investigators, who also added to the understanding of FA at the molecular level, published their findings in the July 15 issue of Proceedings of the National Academy of Sciences. MDA supported Des Richardson at the University of Sydney for this work.

Starting at age 4.5 weeks, before disease effects were present, and continuing until they reached 8.5 weeks and had pronounced symptoms, the FA mice received iron chelation therapy five days a week with a compound that penetrates mitochondria. The chelation-treated mice showed a marked and significant decrease in cardiac iron levels compared to those treated with a placebo.

The investigators note that, although chelation reduced iron levels and limited cardiac hypertrophy in the FA mice, the animals still had decreased cardiac function as well as the weight loss and hunched stance typical of those with the FA-like defect.

Importantly, however, the chelation didn’t lead to overall body iron depletion in the mouse, or toxicity, making it a potential therapeutic strategy for the disease.

The study results are “very important in understanding and treatment of the highly aggressive neurodegenerative and cardiodegenerative disease Friedreich’s ataxia,” said Richardson.

“We’ve demonstrated for the first time the processes responsible for the iron loading that underlies Friedreich’s ataxia and uncovered a possible treatment strategy to target the toxic iron accumulation and remove it.”

First problem in SMA may be where nerve and muscle fibers meet

Spinal muscular atrophy (SMA), long believed to be caused by the loss of motor neurons (nerve cells that control muscle) in the spinal cord, may begin with events preceding motor neuron loss, according to a group of researchers coordinated by MDA grantee Umrao Monani at Columbia University in New York.

Monani and colleagues, who published their results Aug. 15 in Human Molecular Genetics, say the findings could have important implications for development of SMA treatments.

The underlying cause of SMA is a deficiency of the SMN (survival of motor neuron) protein. The more SMN one has, the better, with very low levels resulting in severe disease and somewhat higher levels resulting in less severe disease. Until recently, the steps between SMN depletion and loss of motor neurons were obscure.

The new findings point to the meeting place of nerve and muscle fibers — the neuromuscular junction — as the first casualty in SMA, with the loss of motor neuron cell bodies coming as a later event. (Motor neurons have cell bodies in the spinal cord and long, thin fibers called axons that travel outside the cord and activate muscle fibers by sending them chemical signals.)

Working with SMA mice with varying levels of SMN and disease of varying severity, the researchers found the first detectable signs of SMA to be abnormalities at the tip of the axon as it nears the muscle fiber. In the SMA mice, clumps of cellular material accumulated in these axon tips on the nerve side of the neuromuscular junction. On the muscle side, the receptors (receivers) of the nerve signals formed abnormal clusters and didn’t mature properly. The extent and severity of these defects correlated with disease severity and with SMN levels.

An analysis of diaphragm muscle tissue taken from severely affected SMA patients revealed neuromuscular junction defects similar to those seen in the SMA mice.

The researchers say their findings “warrant the search for strategies that would maintain function at the neuromuscular junctions as a means of treating the disease.”

Clinical Trials and Studies

Gene transfer trial under way in LGMD2D

A small, MDA-supported study to test the safety of injecting alpha-sarcoglycan genes into a leg muscle in children and adults with type 2D limb-girdle muscular dystrophy (LGMD2D) is under way at Nationwide Children’s Hospital in Columbus, Ohio. LGMD2D results from a lack of the muscle protein alpha-sarcoglycan. (See “Gene transfer in LGMD2D mice bodes well for human trial.”) Participants must be at least 5 years old and meet other criteria. Contact Xiomara Rosales-Quintero at (614) 722-6961 or Xiomara.Rosales-Quintero@nationwidechildrens.org.

CellCept disappointing in two myasthenia gravis trials

Two large trials of the potent immunosuppressant myocophenolate mofetil (CellCept) in the autoimmune disease myasthenia gravis (MG) have, surprisingly, yielded results that suggest the drug is no better than standard treatment with the corticosteroid prednisone in treating this disease. The findings from both studies were published in the Aug. 5 issue of Neurology.

Both trials were double-blind, meaning neither participants nor investigators knew which substance was being taken; and randomized, meaning each participant had an equal chance of being assigned to receive the study drug or a placebo (inactive substance).

The first, a 13-center, U.S.-based study of 80 people with MG, compared 2.5 grams per day of mycophenolate mofetil plus 20 milligrams a day of prednisone, to a placebo plus 20 milligrams a day of prednisone, over three months.

The investigators, coordinated by Donald Sanders at Duke University, were members of the Muscle Study Group, which includes several MDA clinic directors. They measured changes in muscle strength and function between the start and end of the study, using the “quantitative myasthenia gravis” standardized scale.

The average change in score on the MG scale was similar in the prednisoneplus mycophenolate and the prednisoneplus-placebo groups.

The second study, an international trial that included 88 participants from 43 centers in several countries, included patients with MG who had been taking prednisone for at least four weeks. Donald Sanders coordinated the publication group.

For nine months, participants were randomly assigned to additional treatment with either 2 grams per day of mycophenolate mofetil or a placebo, while their prednisone dosage was gradually reduced on a predetermined schedule.

They were evaluated on the quantitative MG scale, as well as on scales of activities of daily living and a general health survey.

Mycophenolate mofetil wasn’t any better than a placebo at maintaining MG control during the nine months of prednisone dose reduction.

In the same issue of Neurology, Michael Benatar, co-director of the MDA clinic at Emory University in Atlanta and an MDA research grantee, and Lewis Rowland, former director of the MDA/ALS Center at Columbia University in New York and a former MDA research grantee, probed some of the explanations the investigators offered as an alternative to concluding that mycophenolate mofetil simply isn’t any more effective than prednisone in MG.

They note that the MG studies may have been too short to show an effect of mycophenolate; that prednisone may have been more effective than expected in these study participants, leading to an obliteration of any difference between the groups treated with mycophenolate and those treated with prednisone alone; that, in one or both studies, the criteria used to judge change may have been so stringent that small changes that patients might consider significant were overlooked; and/or that the patients in these trials may not represent the general MG population.

Special diet and supplement relieve symptoms in seven with CPT2 deficiency

Seven people with carnitine palmityl transferase 2 deficiency (CPT2) who took a special dietary supplement and followed a prescribed diet for seven months to five years found their exerciseassociated muscle pain, as well as dangerous episodes of acute muscle breakdown, resolved.

Without the CPT2 enzyme, compounds called long-chain fatty acids can’t enter cellular structures known as mitochondria, where they normally would be utilized for energy production.

The energy deficit experienced by people with CPT2 deficiency makes exercise difficult or impossible and can cause frequent episodes of rapid muscle destruction that leads to kidney damage. A low-fat, high-carbohydrate diet is a standard therapy, but it’s only moderately effective.

Charles Roe at the Institute of Metabolic Disease at Baylor University Medical Center in Dallas, and colleagues, who published their results in the July 22 issue of Neurology, gave study participants a compound called triheptanoin as a substitute for most dietary fat in a special diet.

Triheptanoin is a molecule containing three medium-chain fatty acids (heptanoate) attached to a carbohydrate (glycerol) backbone. Unlike long-chain fatty acids, which require CPT2 or other enzymes to enter mitochondria, heptanoate can enter these structures by itself.

The study participants, who ranged in age from 10 to 55, ate a diet that was 13 percent protein, 37 percent carbohydrates and 20 percent fat, with triheptanoin oil making up the remaining 30 percent of daily calories. They mixed the oil in foods such as yogurt or pudding and ingested it slowly at each meal and at bedtime, as well as 30 minutes before strenuous activity.

Participants who adhered to the triheptanoin diet avoided hospitalization and muscle breakdown, and only two experienced even mild muscle pain with exercise. All seven reported they could perform strenuous activities, including team sports, swimming, aerobics, skiing and hiking.

Triheptanoin oil is not available except in research studies. However, it has been granted “orphan product status,” which fast-tracks development of drugs for rare diseases, by the U.S. Food and Drug Administration.

Roe and colleagues are collaborating with corporations to develop a powder form of triheptanoin that can be taken orally or dissolved for use as an intravenous therapy.

People with CPT2 deficiency should consult their physicians before taking a dietary supplement or starting a special diet.

Cardiomyopathy with DMD, with BMD, and without MD follow different courses

Cardiac muscle deterioration (cardiomyopathy) tends to follow a different course in children with Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD), and both courses are different from the progression of cardiomyopathy from other causes, according to a report published in the June issue of the American Heart Journal.

Data for the report were gathered from 57 pediatric cardiac centers by the Pediatric Cardiomyopathy Registry, a database sponsored by the National Institutes of Health in Bethesda, Md. MDA helped support the study.

Steven Lipshultz at the University of Miami Miller School of Medicine coordinated the study team, which analyzed medical records of patients with a diagnosis of cardiomyopathy who visited a pediatric cardiologist between 1990 and 2005.

Fifteen children and adolescents with BMD-associated cardiomyopathy, 128 with DMD-associated cardiomyopathy, and 312 with cardiomyopathy from other causes were included. All were 18 or younger when their cardiac condition was diagnosed.

Patients with BMD were less likely to experience marked cardiomyopathy as children, but when they did, they generally had more severe symptoms than those with DMD, the investigators say.

They found there may be two separate groups of children with BMD, one with very rapid cardiac deterioration and one with more stable function. The authors recommend cardiac evaluations for BMD patients in their childhood and mid-teen years and, if indicated, early treatment.

At the time of diagnosis, children with DMD and BMD had better function of the left ventricle (lower left pumping chamber) of the heart on some measures than did children with other types of cardiomyopathies, but the walls of their left ventricles were thinner and smaller.

Children with MD, the investigators note, have ongoing loss of cardiac muscle cells, which is less likely to occur in children with cardiomyopathy from other causes. The MD-affected children generally had a more severe cardiomyopathy disease course than the non-MD-affected children, which the investigators say may be related to this cell loss.

Children with cardiomyopathies without DMD or BMD, however, had a higher incidence of a condition known as congestive heart failure at the time of diagnosis than those with MD.

Children with DMD had a shorter survival time after diagnosis of cardiomyopathy than did children with either BMD or no MD, which the authors say may result in part from their lack of access to heart transplantation compared to the other groups.

“Although large studies have not been performed in these [MD] patients, many experts in this field believe that the initiation of medical treatment at or even before the first signs of cardiomyopathy may delay the appearance of heart failure symptoms,” Lipshultz said.

Until specific treatments for MD are developed, the investigators say, children with DMD- or BMD-associated cardiac dysfunction should be cared for using current guidelines, such as those developed by the American Academy of Pediatrics (see “Let the Beat Go On,” Quest March-April 2006).

UC Irvine professor seeks people with rare muscle and bone disorder

Virginia Kimonis, a professor of pediatrics at the University of California-Irvine, is conducting a study of people with hereditary inclusion-body myopathy (IBM) accompanied by either bone pain and susceptibility to fractures and/or by mental deterioration. The combination of these three conditions has been traced to mutations in the VCP gene. Contact Kimonis at (714) 456-5791, (949)-824-0571 or vkimonis@uci.edu.

Parents sought for survey of genetic counseling experiences, knowledge

A graduate student in the Genetic Counseling Program at the University of Maryland School of Medicine in Baltimore is conducting a large-scale survey of what parents of children with neuromuscular disorders know about the genetic basis of their child’s condition and how this information was obtained. The investigators hope to improve parental education in this area. The survey is available online at www.surveymonkey.com/s.aspx?sm=px33yKo77QFithmcfY1sag_3d_3d. Contact Jacquelyn Francis at jfran007@umaryland.edu with questions or concerns.