• A little dystrophin is better than none
• Gene transfer may be a good way to block myostatin
• Gene transfer benefits mice with myotubular myopathy
• Protecting mitochondria with Debio-025 helped mice with two forms of MD
• Company to develop ‘chaperone’ molecule for Pompe disease
• MDA, SMA groups release family version of SMA Standard of Care
• MDA joins SMA groups in support of SMA Treatment Acceleration Act
• GINA gets thumbs-up from Congress
• Clinical Trials and Studies
• Compressed prednisone schedule in DMD may reduce some side effects
• Pentoxifylline benefits minimal in DMD
• Dystrophin mutation analysis predicted age of onset of cardiac problems in BMD
• Boys with DMD or BMD responded to ACE inhibitor treatment of heart problems
• Antibodies to SOX1 protein may indicate lung cancer in LEMS
• Four small studies found rituximab may help in treatment-resistant MG
• CMT1A may worsen with passage from parent to child
• Valproic acid and carnitine to be tested in SMA1
• MDA supports 1st U.S. trial of lithium in ALS

A little dystrophin is better than none

MDA grantee Dongsheng Duan at the University of Missouri at Columbia, and colleagues, have found that mice with only 5 percent of the normal level of the muscle protein dystrophin were slightly stronger, at least temporarily, than mice without any dystrophin.

The study, published online April 1 in the American Journal of Pathology, may have implications for potential gene-based and other therapies for Duchenne muscular dystrophy (DMD) that only partially restore the needed dystrophin protein to muscles.

Until now, it’s been assumed by most experts that about 20 percent of the normal level of dystrophin would be needed for therapy to be meaningful in boys with DMD, a disease in which dystrophin is missing in muscle cells.

But when Duan’s team bred mice that not only had very low dystrophin levels but made a slightly smaller-than-normal version of the protein, they were surprised to see stronger grip strength and more resistance to contraction-related injury than they did in mice without any dystrophin at all. However, they also noted the muscle protection was limited and wore off when the mice got old.

In humans, the researchers note, 30 percent of a normal dystrophin amount is thought to be sufficient to prevent MD, and 20 percent has been believed to result in mild MD. It now appears that levels perhaps even as low as 5 percent of normal might be beneficial, even if they aren’t curative.

Gene transfer may be a good way to block myostatin

Transferring the gene for a myostatin-blocking protein into muscles might be a good way to block this muscle-growth-limiting protein, say researchers coordinated by Xiao Xiao at the University of North Carolina at Chapel Hill, in a report published in the March issue of Human Gene Therapy.

Various compounds to inhibit myostatin have been proposed as possible treatments for muscle degeneration, and one such compound, MYO-029, recently was tested in a clinical trial in adults with various muscular dystrophies. MYO-029 is an immune-system protein (antibody) that blocks, or neutralizes, myostatin. It was found safe in patients. (See Research Updates, May-June 2008).

Xiao and colleagues inserted the gene for MPRO (myostatin propeptide), which blocks myostatin, into the shells of type 8 adeno-associated virus (AAV8). They then injected the AAV8-MPRO combination into a vein in mice with Duchenne muscular dystrophy (DMD).

After only one injection into each mouse, they saw an increase in skeletal muscle bulk and strength, as well as larger and more uniform muscle fibers and less inflammation and scar tissue than in untreated DMD-affected mice.

However, on a treadmill test, the treated mice showed less endurance than their untreated counterparts. The investigators say they have no clear explanation for this, but they note that stronger muscle force doesn’t necessarily mean better endurance and that blood-vessel abnormalities in these mice also might be a contributing factor.

Xiao, who has received MDA funding for other gene-transfer research, says the long-lasting nature of a gene transfer approach is an advantage over using an antibody or other protein. “Since we used AAV to produce the propeptide in a continuous way in the mice, any newly synthesized myostatin in muscle will be neutralized,” he said.

“When you use a neutralizing [disabling] antibody against myostatin, you have to keep administering it to the patients frequently to keep an effective concentration required to block myostatin activity. When using a gene therapy approach with AAV, the mice — or patients — produce their own propeptide 24 hours a day, seven days a week.”

Gene transfer benefits mice with myotubular myopathy

Anna Buj-Bello at Louis Pasteur University in Illkirch, France, with a team that included MDA grantee Alan Beggs at Children’s Hospital and Harvard Medical School in Boston, have demonstrated that gene transfer may be an effective approach to treating myotubular myopathy (MTM), which results from the lack of a protein called myotubularin.

How chaperone molecules work

Chaperone molecules like the one Amicus Therapeutics is developing for Pompe disease help damaged or malformed proteins fold into a usable shape.

A single injection of myotubularin genes into a leg muscle in myotubularin-deficient mice resulted in a large increase in muscle volume and force, as well as a normalization of microscopic appearance of the muscle fibers in the injected muscle.

The researchers, who published their results online April 22 in Human Molecular Genetics, used modified adeno-associated viruses (AAVs) as delivery vehicles for the genes. AAV vehicles have been used in human gene-transfer trials to target muscle fibers.

They note that their results “indicate that gene therapy by local [myotubularin] transfer in skeletal muscle improves the strength of the targeted muscle in a mouse model of myotubular myopathy and might open novel strategies for treating this disorder.”

Protecting mitochondria with Debio-025 helped mice with two forms of MD

A compound that protects cellular structures known as mitochondria from damage is beneficial in mice with two forms of muscular dystrophy, investigators have found.

Jeffery Molkentin at Cincinnati Children’s Hospital Medical Center, and colleagues, including H. Lee Sweeney at the University of Pennsylvania, who has MDA funding for related work, published their findings online March 16 in Nature Medicine.

First, the investigators analyzed mice with two forms of MD that also were bred not to produce a protein called cyclophilin D.

The lack of cyclophilin D prevented much of the damage that would have been expected in the delta-sarcoglycan-deficient mouse model of type 2F limb-girdle MD (LGMD2F) and the laminin-2-deficient mouse model of congenital MD. This is due to its apparent protection of mitochondria, the energy-producing structures inside cells.

In both these forms of MD, as well as in Duchenne MD (DMD), the membrane surrounding each muscle fiber allows excess calcium to flow into muscle cells, which, in part through cyclophilin D’s actions, causes swelling and destruction of mitochondria. Without cyclophilin D, the researchers found, the mitochondria of MD-affected mice demonstrated resistance to this type of damage.

They next tested Debio-025 (made by DebioPharm of Lausanne, Switzerland), a known inhibitor of cyclophilin D, in the mouse model of LGMD2F and in mice missing the dystrophin protein that have a disease resembling DMD.

The mitochondria of these mice also were protected. In addition, the DMD mice treated with Debio-025 from four to 10 weeks of age showed better muscle-fiber organization and less scar tissue than was seen in untreated DMD mice.

Similar effects were seen in the LGMD2F mice treated with Debio-025 from age four to age 10 weeks, and these mice also showed better cardiac muscle health than did untreated LGMD2F mice.The researchers say their results suggest that protecting muscle-fiber mitochondria by inhibiting cyclophilin D could become a new approach for treating muscular dystrophies that are associated with defective muscle-fiber membranes.

Company to develop ‘chaperone’ molecule for Pompe disease

A new approach to treating Pompe disease (acid maltase deficiency), a genetic muscle disorder resulting from a lack of functional acid maltase enzyme, has yielded encouraging findings to researchers at Amicus Therapeutics (www.amicustherapeutics.com), a biopharmaceutical company in Cranbury, N.J.

The company presented results of tests in patients’ cells and in healthy volunteers of its experimental compound AT2220 at the American College of Human Genetics annual meeting in Phoenix in March. (Amicus presented an earlier stage of its research to MDA’s Translational Research Advisory Committee.)

AT2220 is a small, orally administered molecule that Amicus terms a “pharmacological chaperone,” one of several the company is developing to treat genetic diseases.

Pharmacological chaperones, like their natural counterparts in cells, stick to specific proteins and help them fold into the correct three-dimensional shape. Many genetic diseases, including Pompe disease, can be caused at least some of the time by genetic mutations that result in improper folding of a protein. (In Pompe disease, the protein is the acid maltase enzyme, made from the acid maltase gene.) An improperly folded enzyme doesn’t locate itself or function properly.

The Amicus researchers collected blood and skin samples from 30 people with Pompe disease (26 adults, three children and one infant) due to a variety of mutations in the acid maltase gene.

They then tested cells from these samples to see whether AT2220 could increase the level of functional acid maltase.

Of 26 patients analyzed, 24 had cells that responded to the experimental treatment.

The company also tested AT2220 in 72 healthy volunteers and found it to be safe and well tolerated at all doses studied.

In November, Amicus announced it plans to further develop AT2220 in partnership with Shire Human Genetic Therapies, part of the multinational Shire biopharmaceutical company (www.shire.com).

MDA, SMA groups release family version of SMA Standard of Care

The Patient Advisory Group of the International Coordinating Committee (ICC) for SMA Clinical Trials has published a family-friendly set of guidelines for care in spinal muscular atrophy (SMA) to complement the physician guidelines published in August. (See Research Updates, November-December 2007.)

The ICC includes representatives of MDA, the SMA Foundation, FightSMA and Families of SMA.

The new publication, “A Family Guide to the Consensus Statement for Standard of Care in Spinal Muscular Atrophy,” is designed to guide patients and families in their discussions with doctors and health-care specialists. The committee emphasizes that these guidelines are only suggestions and should not be considered absolute requirements for care.

The Guide has recommendations on confirming the diagnosis; managing breathing, eating and nutrition, movement and daily activities; and preparing for illness.

The entire document can be read and printed out on the MDA Web site at www.mda.org/publications/family_guide_sma_standard_of_care.pdf.

MDA joins SMA groups in support of SMA Treatment Acceleration Act

MDA has joined the SMA Foundation, Families of SMA, and FightSMA in endorsing the SMA Treatment Acceleration Act (H.R. 3334/S.2042). The Act, if passed by Congress, will aid investigators in conducting national clinical trials to identify treatments for spinal muscular atrophy (SMA). It would provide federal support to complement the substantial private funding that national nonprofit organizations, including MDA, are now providing.

GINA gets thumbs-up from Congress

Under the provisions of legislation approved by Congress this spring, insurance companies now are prohibited from requiring people to undergo genetic tests, and from denying them health care insurance or increasing their premiums based on genetic test results.

The Genetic Information Nondiscrimination Act (GINA) also prohibits employers from using genetic test results when making hiring, compensation, assignment or promotion decisions.

President George Bush signed the act on May 21.

Clinical Trials and Studies

For details about clinical trials and studies and disease registries, see www.mda.org, click on Clinical Trials, and use the search boxes.

Several of the following announcements, designated AAN, are from the 60th annual meeting of the American Academy of Neurology, held in April in Chicago.

Compressed prednisone schedule in DMD may reduce some side effects

Two days a week of the corticosteroid prednisone at a high dose appears to be almost as beneficial as a daily moderate dose of the drug in boys with Duchenne muscular dystrophy (DMD), and some side effects may be less severe, investigators reported.

The yearlong, multicenter study, supported by MDA and the National Institutes of Health, was conducted by Diana Escolar at Children’s National Medical Center in Washington, with colleagues at many institutions.

The investigators analyzed data from 64 boys with DMD who were 4 to 10 years old, had not previously taken corticosteroids, and were still walking.

The boys were randomly assigned to take prednisone at 0.75 milligrams per kilogram every day, or to take prednisone at 10 milligrams per kilogram per day two days a week. Neither the boys nor the investigators knew who was on which schedule. (Boys on the two-day prednisone schedule received “dummy” pills on the no-prednisone days.)

Effects on strength maintenance were similar in the two groups, but time required to get up from the floor was better in the daily prednisone group.

Growth retardation, a known prednisone side effect, was less severe in the two-day, high-dose prednisone group, but weight gain, another serious side effect, was the same in both groups after a year. AAN

Pentoxifylline benefits minimal in DMD

Two studies of the drug pentoxifylline in Duchenne muscular dystrohy (DMD) have yielded somewhat disappointing results, investigators reported. It had been hoped that pentoxifylline might slow disease progression by increasing blood flow, reducing scar tissue formation and countering inflammation.

A multicenter study in the United States conducted by Diana Escolar at Children’s National Medical Center in Washington, with many others at different clinics, tested pentoxifylline for a year in 17 boys with DMD who were between 4 and 9 years old and who hadn’t taken corticosteroids (like prednisone). Of 17 patients initially enrolled, only nine completed the study. Strength measurements didn’t show a significant change during the study. Five of the eight participants who withdrew did so because of intolerable side effects, such as nausea and vomiting and reduction of white blood cell numbers.

The investigators said the lack of deterioration in strength in a year’s time suggests a possible beneficial effect on disease progression and warrants further study with a different formulation of pentoxifylline. AAN

A separate DMD study conducted at centers in the United States, Italy, Canada, Israel, Australia and Argentina tested the effect of pentoxifylline plus prednisone.

Diana Escolar and many others tested this drug combination against prednisone plus a placebo in 64 boys with DMD, 57 of whom completed the study. The average age was 10.

Strength measurements at one year were not significantly different between the two groups, but the pentoxifylline-treated patients had more coagulation abnormalities, skin problems and gastrointestinal side effects.

The investigators concluded that pentoxifylline was well tolerated in this group but had no effect in slowing DMD disease progression compared to prednisone alone. AAN

Dystrophin mutation analysis predicted age of onset of cardiac problems in BMD

Investigators reported the age of onset of cardiac problems in boys with Becker muscular dystrophy (BMD) can be approximately predicted from the location and type of mutation in the gene for the muscle protein dystrophin.

They say their analysis of 126 BMD patients identified dystrophin mutations that predispose boys to cardiac muscle deterioration (cardiomyopathy). The team included John Kissel and Jerry Mendell, codirectors of the MDA clinic at Nationwide Children’s Hospital in Columbus, Ohio. AAN

Boys with DMD or BMD responded to ACE inhibitor treatment of heart problems

A research group that included Jerry Mendell and John Kissel, co-directors of the MDA clinic at Nationwide Children’s Hospital in Columbus, Ohio, found treatment with angiotensin converting enzyme (ACE) inhibitors reversed heart-muscle dysfunction in 12 of 19 boys with DMD or BMD, had no effect on four, and didn’t have a sustained effect in three. The investigators said more data are required before they can make definitive recommendations about ACE inhibitors in these diseases and that cardiac magnetic resonance images (MRIs) might be better than echocardiograms in assessing DMD- and BMD-related heart dysfunction. AAN

Antibodies to SOX1 protein may indicate lung cancer in LEMS

The presence of immune-system proteins (antibodies) formed against a cell protein called SOX1 is correlated with the presence of lung cancer in patients with Lambert-Eaton myasthenic syndrome (LEMS), according to a multinational study.

LEMS, which involves debilitating weakness, results from a mistaken immune-system attack on calcium channels on the ends of nerve fibers. These calcium channels are needed for transmission of chemical signals from nerve to muscle fibers, and immune-system antibodies destroy them.

Doctors have long known that people with LEMS also have lung cancer about 40 percent to 60 percent of the time, and it’s known that the inadvertent attack on nerve-fiber calcium channels is an unfortunate “side effect” of the immune system’s attack on similar calcium channels on the surface of lung-cancer cells.

Now, Francesc Graus at the University of Barcelona (Spain) and colleagues, who published their findings March 18 in Neurology, have identified SOX1, a protein found inside lung-cancer tumor cells, as another target of the immune system as it tries to fight the tumor. (Antibodies against SOX1 don’t affect the nerve or muscle fibers.)

When Graus and colleagues studied 55 people with LEMS and a type of lung cancer called small-cell lung carcinoma, and 50 with LEMS alone, they found SOX1 antibodies in the blood of 35 (64 percent) of those with both conditions and in none of those with LEMS alone.

The investigators conclude that detection of SOX1 antibodies may become a useful tool in early detection of lung cancer in patients with LEMS.

Four small studies found rituximab may help in treatment-resistant MG

Four research groups reported improvement of treatment-resistant myasthenia gravis (MG) with the drug rituximab.

A group based in Barcelona, Spain, reported a dramatic improvement with rituximab in six patients with MG who had not responded to other medications. AAN.

When a group that included Rup Tandan, director of the MDA clinic at the Fletcher Allen Health Care Center in Burlington, Vt., tested rituximab in six female patients, all of whom had not responded well to other treatments, they found a trend toward improvement in muscle strength scores after rituximab treatment and “significant and continuous” improvement in scores on a scale measuring activities of daily living. AAN

A group that included Alan Pestronk, MDA clinic director at Washington University in St. Louis, reported using rituximab to successfully treat two patients with MG who had not responded to other forms of therapy. AAN

A French research team reported following five patients with MG who had not responded to other treatments. After two years of treatment with rituximab, all patients had stopped corticosteroid medications and reduced their dose of cholinesterase inhibitor medications (two common treatments for MG). AAN

CMT1A may worsen with passage from parent to child

An Israeli group reported that type 1A Charcot-Marie-Tooth disease (CMT1A), which results from a mutation on chromosome 17 that causes an excess of the PMP22 protein, appears to worsen as it’s passed from parent to child. In 21 out of 23 parent-child pairs, and in 14 out of 16 families studied, there was an earlier age of symptom onset in the children than in their parents, and the average severity in the younger generation was slightly higher than in the parental generation. The researchers said they don’t know what the underlying mechanism of this phenomenon might be. AAN

Valproic acid and carnitine to be tested in SMA1

A trial of valproic acid and carnitine in 36 infants with type 1 spinal muscular atrophy (SMA1) who are 2 weeks to 9 months old opened in April at the University of Utah in Salt Lake City, with additional sites in Baltimore; Detroit; Columbus, Ohio; Madison, Wisc.; Montreal; and Cologne, Germany. Valproic acid may increase production of the needed SMN protein in children with SMA, and carnitine has been added because valproic acid depletes it in the body. The study will last about a year. See www.projectcuresma.org; or contact Sandra Reyna at (801) 581-3551 or sandra.reyna@genetics.utah.edu.

MDA supports 1st U.S. trial of lithium in ALS

An MDA-supported clinical trial of lithium carbonate, a medication commonly used to treat bipolar disorder, is set to begin in people with ALS following reports the drug may dramatically slow the progress of this disease. The study will involve 10 sites throughout the United States. Principal investigator is neurologist Robert Miller, director of the Forbes Norris MDA/ALS Research Center at California Pacific Medical Center in San Francisco. The study is an effort to confirm or refute the findings of a recent Italian trial of lithium carbonate in ALS conducted at the University of Pisa and other institutions. For more information: www.mda.org/research/view_ctrial.aspx?id=219