FDA Highlights: ED drugs could help boys with duchenne muscular dystrophy

by Bruce Sylvester – Treatment with tadalafil or sidenafil appears to improve blood flow in the muscles of boys with Duchenne muscular dystrophy, according to research published in the May 7, 2014 online issue of Neurology.  

Tadalafil (Cialis and Adcirca) and sildenafil (Viagra and Revatio), are FDA-approved to treat erectile dysfunction and pulmonary hypertension.

“The effect was immediate and dramatic. The result also was more pronounced with higher doses,” said investigator and author Ronald G. Victor, MD, of Cedars-Sinai Heart Institute in Los Angeles.

Duchenne muscular dystrophy is a genetic, progressive and fatal muscle disease affecting boys and young men which causes loss of muscle function. There is no approved treatment for the disease, though corticosteroids reduce muscle degeneration and lung and heart dysfunction. However, many patients find the side effects intolerable.

In the new study, investigators reported that when young male subjects, ages 8 to 13, with Duchenne muscular dystrophy performed handgrip exercises, the major artery of the arm and the blood vessels in muscles of the forearm did not respond like those in healthy boys of similar ages. But when the boys with Duchenne received a single dose of tadalafil, they achieved normal vessel function and blood flow. And similar results appeared when sildenafil was substituted for tadalafil.

First, the investigators evaluated 10 boys age 8 to 13 with Duchenne muscular dystrophy who were taking corticosteroids and 10 healthy boys of the same age. The measured the blood flow in each subject’s muscles while at rest and while performing a handgrip exercise. The tests indicated that the subjects with Duchenne had blood flow abnormalities, even with corticosteroid treatment.

Then subjects with Duchenne received either tadalafil or sildenafil, and the tests were repeated. After two weeks, subjects with Duchenne received the other drug, and they were tested again.

After taking either drug, the boys’ blood flow response during exercise was the same as that of the boys who did not have the disease.

Victor noted that more research is needed before suggesting either drug for persons with Duchenne muscular dystrophy. “This is not a cure, but it is the first stop toward identifying potential treatments,” he said.

“We do not know whether this improved blood flow regulation can be sustained with long-term use of the drug,” Victor added. “This proof-of-concept study also does not address the crucial question of whether restoring normal blood flow regulation will preserve muscle and slow disease progression. If so, this would offer a new therapeutic strategy for Duchenne muscular dystrophy, and a Phase III clinical trial has been launched to find out.”

The study was supported by Parent Project Muscular Dystrophy and the National Institutes of Health/National Center for Advancing Translational Sciences.