Cedars-Sinai study: Common drug restores blood flow in deadly form of muscular dystrophy

PUBLIC RELEASE DATE:

7-May-2014

Contact: Sally Stewart sally.stewart@cshs.org 310-248-6566 Cedars-Sinai Medical Center

LOS ANGELES (May 7, 2014) Cedars-Sinai Heart Institute researchers have found that a commonly prescribed drug restores blood flow to oxygen-starved muscles of boys with Duchenne muscular dystrophy, a genetic muscle-wasting disease that rarely is seen in girls but affects one in 3,500 male babies, profoundly shortening life expectancy. It is the most common fatal disease that affects children.

Muscle weakness begins in early childhood, often causing deformity of the arms, legs and spine. Heart and respiratory muscles often begin to fail before children reach early teen years. Although steroid medications which often are not well tolerated and other therapies may ease symptoms and delay the most severe effects, no disease-specific treatment exists, and patients rarely survive into their 30s.

But in this case study of 10 boys with Duchenne muscular dystrophy, also called DMD, a single dose of a drug often prescribed for erectile dysfunction or pulmonary hypertension corrected defective blood vessel mechanisms and restored blood flow to exercising muscles.

"The effects were immediate and dramatic, raising the question: If a single dose restores blood flow to muscle while the drug is in the patient's system, could ongoing tadalafil administration provide sustained benefits, possibly preserve muscle and slow disease progression? If so, this would offer a new therapeutic strategy for DMD, and we have launched a randomized Phase III clinical trial to find out," said Ronald Victor, MD, director of the Cedars-Sinai Center for Hypertension, associate director of clinical research at the Heart Institute and the Burns and Allen Chair in Cardiology Research. He is the senior author of a highlighted article in the May 7 online edition of Neurology.

Duchenne muscular dystrophy results from a genetic defect that eliminates a protein called dystrophin in the membranes of muscle cells. For more than 25 years, Victor has studied DMD and a less aggressive but debilitating variant called Becker muscular dystrophy. This form of muscular dystrophy, usually diagnosed in early adulthood, is caused by a reduction, but not absence, of dystrophin.

Victor led a research team that in 2000 discovered that the blood flow abnormality in the muscles of children with DMD was caused by a loss of nitric oxide, a signaling chemical that normally tells blood vessels to relax during exercise, increasing blood flow and oxygenation.

In studies of mice bred to represent diseases of dystrophin deficiency, the researchers found that drugs prescribed for other disorders of blood vessel function could restore muscle blood flow and enable the animals to exercise more, with less muscle injury. Tadalafil, known by the brand names Cialis and Adcirca, and sildenafil, called Viagra and Revatio, have long been approved by the Food and Drug Administration to treat erectile dysfunction and pulmonary hypertension, a serious illness that restricts blood flow to the lungs.

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Cedars-Sinai study: Common drug restores blood flow in deadly form of muscular dystrophy