Experimental drug therapy might slow Duchenne muscular dystrophy
A small safety trial has suggested that a new type of therapy for Duchenne muscular dystrophy may partially replace a missing protein and -- at the very least -- slow the course of the disease, Dutch researchers reported Thursday in the New England Journal of Medicine.
The experimental drug, developed by the Dutch pharmaceutical company Prosensa, is an “antisense” fragment of ribonucleic acid (RNA) that can mitigate the effects of a genetic mutation.
Patients with muscular dystrophy have one of several mutations in the gene that serves as the blueprint for a protein called dystrophin, which plays an essential role in muscle activity. Those afflicted are usually in a wheelchair by age 12 and die by early adulthood.
The antisense drug, PRO051, binds to messenger RNA produced from the defective gene and enables the body’s protein-making machinery to produce a more effective form of dystrophin. Though the newly produced dystrophin is not as active as that produced by an intact gene, doctors believe it will alleviate many symptoms of the disease, perhaps converting it to a milder form such as Becker’s muscular dystrophy.
Geneticist Judith C. van Deutekom of Leiden University Medical Center and her colleagues studied four boys with a specific mutation in the dystrophin gene. A biopsy before the experiment showed they had no dystrophin at all in the tibialis anterior muscles of their legs.
Each received a single injection of PRO051 into those muscles. A biopsy of the site 28 days later showed that as much as 12% of the biopsied tissue was composed of functional dystrophin.
Because of the localized area of the injection, not enough was present to alter muscle strength. The patients suffered no adverse effects other than pain at the injection site.
The team now must devise a way to get the drug to muscle tissue throughout the body, perhaps by injecting it under the skin.
Experts cautioned that the therapy could be expensive -- as much as $250,000 per treatment -- and that it would need to be repeated at regular intervals during a patient’s life.
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