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Long-term glucocorticoids help patients with DMD

boy sitting in wheelchair

Glucocorticoids, a class of steroid hormone medications, have definite long-term benefits for patients with Duchenne muscular dystrophy, including extending muscle strength and function over years and decreasing the risk of death.

There is currently no cure for the devastating, progressive neuromuscular disease known as Duchenne muscular dystrophy (DMD). But clinics that treat patients with this disease have long relied on a class of steroid hormone medications, known as glucocorticoids, to ease its symptoms. Over weeks and months, these drugs help preserve muscle strength and function. Though these short-term benefits have been clear, some physicians have balked at using these medications over the long term – their benefits over years was unknown, making their potential side effects not worth the risk.

Now, a study published online Nov. 22, 2017 in The Lancet suggests that these medicines have definite long-term benefits, including extending muscle strength and function over years and even decreasing the risk of death. These findings support what has become the standard prescribing practice at many clinics and could help sway parents who are on the fence about their children receiving these therapies.

DMD is characterized by loss of muscle function and progressive muscle weakness that begins in the lower limbs and typically affects males due to the location of its causative genetic mutation. Patients with this devastating neuromuscular disease often receive glucocorticoids at some point as the disease progresses. Studies since the late 1980s have confirmed short-term benefits of treating with these drugs, including delaying the loss of muscle strength and function.

However, no prospective study had followed long-term glucocorticoid use in these patients, explains Heather Gordish-Dressman, Ph.D., a statistician at the Center for Genetic Medicine Research at Children’s National Health System and study senior author. The lack of long-term data led some physicians to delay treatment with these drugs since their use can lead to significant side effects, including weight gain, delayed growth and immunosuppression.

“Everyone had the idea that long-term use could be beneficial, but nobody had really rigorously tested that,” Gordish-Dressman says.

Craig McDonald, M.D., a University of California, Davis, professor and lead author of the study adds: “This long-term, follow-up study provides the most definitive evidence that the benefits of glucocorticoid steroid therapy in DMD extend over the entire lifespan. Most importantly, patients with Duchenne using glucocorticoids experienced an overall reduction in risk of death by more than 50 percent.”

To determine whether the short-term benefits of these drugs extend in the long term, Gordish-Dressman and researchers scattered across the country tapped data from the Cooperative International Neuromuscular Research Group’s Duchenne Natural History Study, the largest study to follow patients with DMD over time. They gathered data for 440 males with DMD aged 2 to 8 years old. About 22 percent had never taken glucocorticoids or had taken these medications for less than one year. The remainder had taken them for at least one year or longer.

By analyzing data for up to 10 years for these patients, the long-term benefits became clear, Gordish-Dressman adds. Glucocorticoid treatment for patients who received it for more than one year delayed loss of mobility milestones that affected the lower limbs by 2.1 to 4.4 years, such as going from supine to standing, climbing four stairs, and walking or running 10 meters, compared with boys who received the medications for less than one year. Long-term glucocorticoid therapy also delayed the loss of mobility milestones in upper limbs, such as hand function, performing a full overhead reach and raising the hands to the mouth.

Long-term use of these drugs also was associated with a decreased risk of death over the length of the study. Furthermore, deflazacort – a glucocorticoid recently approved by the Food and Drug Administration specifically for DMD – delayed loss of the ability to move from supine position to standing, walking and hand-to-mouth function significantly better than prednisone, the most popular glucocorticoid prescribed for DMD in the United States.

Gordish-Dressman says that glucocorticoids are currently a standard part of care for most patients with DMD, with some clinics prescribing these medications as soon as patients are diagnosed. However, because long-term data supporting their use was lacking, some physicians hesitate to prescribe glucocorticoids until the disease had progressed, when patients already had lost significant function.

Future studies will examine which medicines in this class of drugs and which regimens might offer the most benefits as well as how benefits differ with longer-term medication use.

Research reported in this news release was supported by the U.S. Department of Education/NIDRR, H133B031118 and H133B090001; the U.S. Department of Defense, W81XWH-12-1-0417; National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under award number R01AR061875; and Parent Project Muscular Dystrophy.

macrophage

Improving treatment success for Duchenne muscular dystrophy

macrophage

Macrophages, white blood cells involved in inflammation, readily take up a new medicine for Duchenne muscular dystrophy and promote its sustained delivery to regenerating muscle fibers long after the drug has disappeared from circulation.

Chronic inflammation plays a crucial role in the sustained delivery of a new type of muscular dystrophy drug, according to an experimental model study led by Children’s National Health System.

The study, published online Oct. 16, 2017 in Nature Communications, details the cellular mechanisms of morpholino antisense drug delivery to muscles. Macrophages, white blood cells involved in inflammation, readily take up a new medicine for Duchenne muscular dystrophy (DMD) and promote its sustained delivery to regenerating muscle fibers long after the drug has disappeared from circulation.

Until recently, the only approved medicines for DMD targeted its symptoms, rather than the root genetic cause. However, in 2016 the Food and Drug Administration approved the first exon-skipping medicine to restore dystrophin protein expression in muscle: Eteplirsen, an antisense phosphorodiamidate morpholino oligomer (PMO). The drug had shown promise in preclinical studies but had variable and sporadic results in clinical trials.

The Children’s National study adds to the understanding of how this type of medicine targets muscle tissue and suggests a path to improve treatments for DMD, which is the most common and severe form of muscular dystrophy and currently has no cure, explains study co-leader James S. Novak, Ph.D., a principal investigator in Children’s Center for Genetic Medicine Research.

Because the medication vanishes from the blood circulation within hours after administration, Children’s research efforts have focused on the mechanism of delivery to muscle and on ways to increase its cellular uptake – and, by extension, its effectiveness. However, researchers understand little about how this medication actually gets delivered to muscle fibers or how the disease pathology impacts this process, knowledge that could offer new ways of boosting both its delivery and effectiveness, says Terence Partridge, Ph.D., study co-leader and principal investigator in Children’s Center for Genetic Medicine Research.

To investigate this question, Novak, Partridge and colleagues used an experimental model of DMD that carries a version of the faulty DMD gene that, like its human counterparts, destroys dystrophin expression. To track the route of the PMO into muscle fibers, they labeled it with a fluorescent tag. The medicine traveled to the muscle but only localized to patches of regenerating muscle where it accumulated within the infiltrating macrophages, immune cells involved in the inflammatory response that accompanies this process. While PMO is rapidly cleared from the blood, the medication remained in these immune cells for up to one week and later entered muscle stem cells, allowing direct transport into regenerating muscle fibers. By co-administering the PMO with a traceable DNA nucleotide analog, the research team was able to define the stage during the regeneration process that promotes heightened uptake by muscle stem cells and efficient dystrophin expression in muscle fibers.

“These macrophages appear to extend the period of availability of this medication to the satellite cells and muscle fibers at these sites,” Partridge explains. “Since the macrophages are acting as long-term storage reservoirs for prolonged delivery to muscle fibers, they could possibly represent new therapeutic targets for improving the uptake and delivery of this medicine to muscle.”

Future research for this group will focus on testing whether macrophages might be used as efficient delivery vectors to transport eteplirsen to the muscle, which would avert the rapid clearance currently associated with intravenous delivery.

“Understanding exactly how different classes of exon-skipping drugs are delivered to muscle could open entirely new possibilities for improving future therapeutics and enhancing the clinical benefit for patients,” Novak adds.

mitochondria

Mitochondria key for repairing cell damage in DMD

mitochondria

A research team led by Jyoti K. Jaiswal, M.S.C., Ph.D., found that dysfunctional mitochondria prevent repair of muscle cells in Duchenne muscular dystrophy.

What’s known

Duchenne muscular dystrophy (DMD), one of the most severe forms of muscular dystrophy, is caused by a defect in the dystrophin gene. The protein that this gene encodes is responsible for anchoring muscle cells’ inner frameworks, or cytoskeletons, to proteins and other molecules outside these cells, the extracellular matrix. Without functional dystrophin protein, the cell membranes of muscle cells become damaged, and the cells eventually die. This cell death leads to the progressive muscle loss that characterizes this disease. Why these cells are unable to repair this progressive damage has been unknown.

What’s new

A research team led by Jyoti K. Jaiswal, M.S.C., Ph.D., a principal investigator in the Center for Genetic Medicine Research at Children’s National Health System, investigated this question in two experimental models of DMD that carry different mutations of the dystrophin gene. The researchers monitored the effects of the lack of functional dystrophin protein in these preclinical models on the level and function of muscle cell. They found that mitochondria – organelles that act as powerhouses to supply the chemical energy to drive cellular activities – are among the first to be affected. They found that the decline in mitochondrial level and activity over time in these experimental models preceded the onset of symptoms. The research team also looked at the ability of the experimental models’ muscle cells to repair damage. As the muscle cell mitochondria lost function, the cells’ ability to repair damage also declined. Efforts to increase mitochondrial activity after these organelles became dysfunctional did not improve muscle repair. This suggests that poor muscle repair may not be caused by a deficit in energy production by mitochondria.

Questions for future research

Q: Does similar mitochondrial dysfunction occur in human patients with DMD?
Q: How can the mitochondrial dysfunction be prevented?
Q: Is there a way to reverse mitochondrial dysfunction to better preserve the ability of muscle cells to repair from DMD-related damage?

Source: “Mitochondria mediate cell membrane repair and contribute to Duchenne muscular dystrophy.” Vila, M.C., S. Rayavarapu, M.W. Hogarth, J.H. Van der Meulen, A. Horn, A. Defour, S. Takeda, K.J. Brown, Y. Hathout, K. Nagaraju and J.K. Jaiswal. Published by Cell Death and Differentiation February 2017.

Muscular Dystrophy Association awards grants to two Children’s National scientists

Marshall Hogarth, Ph.D

Marshall Hogarth, Ph.D

James Novak, Ph.D.

James Novak, Ph.D.

Two Children’s National Health System research scientists, Marshall Hogarth, Ph.D. and James Novak, Ph.D., have received Post-Doctoral Development Grants from the Muscular Dystrophy Association (MDA) as part of funding awarded to young, rising researchers who are poised to become independent investigators.

Over the next three years, Hogarth and Novak will be allotted $180,000 each to underwrite their individual research projects.

Hogarth’s research is focused on limb-girdle muscular dystrophy (LGMD), a disease which presents as muscle weakness when patients are in their late teens before rapidly progressing to severe debilitation. The MDA grant will allow Hogarth to continue his research investigating the replacement of muscle with fatty tissue and the role this plays in the late onset and subsequent progression of LGMD in patients.

Novak focuses mainly on researching Duchenne Muscular Dystrophy (DMD), a severely debilitating form of MD, that leads to progressive muscle weakness and respiratory and cardiac failure. Currently, the only Food and  Drug Administration (FDA)  approved treatment for DMD is exon-skipping. The MDA grant will support Novak’s study of the mechanisms that regulate the delivery of exon-skipping drugs in muscle, in order to identify new therapeutic targets and improve drug efficacy for patients with DMD.

While Hogarth and Novak focus on different aspects of neuromuscular disease, both look forward to making significant contributions that lead to overall improvements in the treatment of patients impacted by muscular dystrophy.

Children’s National spin-off ReveraGen announces agreement with actelion for Duchenne Muscular Dystrophy treatment

Earlier this month, ReveraGen BioPharma announced an exclusive option agreement with Actelion Ltd for lead compound vamorolone, a non-hormonal steroid modulator that is primarily used for the treatment of Duchenne Muscular Dystrophy (DMD). ReveraGen, the first Children’s National private spin-off company, is engaged in the discovery and development of proprietary therapeutic products for neuromuscular and inflammatory diseases.

Under the terms of the license agreement, Actelion and ReveraGen will partner to research and co-develop the novel compound vamorolone, which holds the potential to preserve muscle function and prolong ambulation in DMD patients, without some of the side effects that are commonly associated with glucocorticoid therapy. Those commonly associated include growth stunting and immune suppression, which can pose significant challenges for very young patients.

ReveraGen completed Phase I clinical trials for vamorolone in late 2015, and a Phase IIa program is currently underway to investigate the safety and efficiency of vamorolone in male DMD patients between four and seven years of age who have not taken deflazacort or prednisone. A Phase IIb program is also in early planning stages.

ReveraGen Co-Founder and CEO Eric Hoffman, PhD, has worked on DMD since the late 1980’s and has led his own research group for nearly 20 years at Children’s National. He co-founded ReveraGen back in 2008 with John McCall, PhD and Kanneboyina Nagaraju, PhD, DVM, before being named CEO in 2014. Children’s National maintains a 38 percent stake in ReveraGen.

Biomarkers sensitive to daily corticosteroid use

Using a mass spectrometer, Yetrib Hathout, Ph.D., is able to quantify 3,000 to 4,000 proteins from a tissue sample to identify proteins associated with cancer.

Using a Somascan proteomics assay – which simultaneously analyzes 1,129 proteins in a small volume of serum – a team led by Children’s National Health System researchers identified 21 biomarkers that respond to corticosteroids taken daily by children with Duchenne muscular dystrophy (DMD) and inflammatory bowel disease.

Corticosteroids are commonly prescribed to treat inflammatory conditions. High daily doses of corticosteroids are considered the standard of care for DMD, a type of muscular dystrophy characterized by worsening muscle weakness that affects 1 in 3,600 male infants. However, depending on the age of the child and drug dosage, chronic use is associated with such side effects as changes in bone remodeling that can lead to stunted growth, weight gain, facial puffiness caused by fat buildup, mood changes, sleep disturbances, and immune suppression. The research team sought to identify blood biomarkers that could be leveraged to create a fast, reliable way to gauge the safety and efficacy of corticosteroid use by children. The biomarkers also could guide development of a replacement therapy with fewer side effects.

“Ten pro-inflammatory proteins were elevated in untreated patients and suppressed by corticosteroids (MMP12, IL22RA2, CCL22, IGFBP2, FCER2, LY9, ITGa1/b1, LTa1/b2, ANGPT2 and FGG),” Yetrib Hathout, Ph.D., Proteomic Core Director at Children’s National, and colleagues write in the journal Scientific Reports. “These are candidate biomarkers for anti-inflammatory efficacy of corticosteroids.”

The blood biomarkers sensitive to corticosteroids fit into three broad groups, according to the authors. The children taking corticosteroids were matched with children of the same age who had never taken the medicine. Five biomarkers significantly increased in this corticosteroid-naïve group and decreased in kids prescribed corticosteroids. The biomarkers generally were inflammatory proteins and included chemokine, insulin-like growth factor binding protein 2, and integrin alpha-I/beta-1 complex.

The second group of biomarkers included nine proteins associated with macrophage and T-lymphocytes that were significantly reduced in concentration in kids taking corticosteroids. According to the study, this finding hints at corticosteroids blunting the ability of the immune system’s most able fighters to respond to infection.

In the third group were five proteins that were significantly increased by corticosteroid treatment in DMD and included matrix metalloproteinase 3, carnosine dipeptidase 1, angiotensinogen, growth hormone binding protein, insulin, and leptin, a hormone linked to appetite.

What researchers learned with this study will help them more accurately design the next phase of the work, Hathout says.

“We are the first team to report a number of novel discoveries, including that growth hormone binding protein (GHBP) levels increase with corticosteroid use. This represents a candidate biomarker for stunted growth. In order to use that new information effectively in drug development, the next studies must corroborate the role of serum GHBP levels as predictors of diminished stature,” he adds. “The study finding that four adrenal steroid hormones are depressed in kids taking corticosteroids raises additional questions about the broader impact of adrenal insufficiency, including its role in the delay of the onset of puberty.”

This work was supported by National Institutes of Health grants (R01AR062380, R01AR061875, P50AR060836, U54HD071601, K99HL130035, and R44NS095423) and Department of Defense CDMRP program grant W81XWH-15-1-0265. Additional support was provided by AFM-Telethon (18259) and the Muscular Dystrophy Association USA (MDA353094).