Cedars-Sinai Heart Institute researchers have found in an initial clinical trial that a drug typically prescribed for erectile dysfunction or pulmonary hypertension restores blood flow to oxygen-starved muscles in patients with a type of muscular dystrophy that affects males, typically starting in childhood or adolescence.
Tadalafil, commonly known by brand names Cialis and Adcirca, reversed the effects of a biochemical chain of events that in Becker muscular dystrophy deprives muscles of an important chemical, nitric oxide, which normally tells blood vessels to relax during exercise, increasing blood flow and oxygenation.
With a single dose, the drug, which works downstream from nitric oxide, fully restored proper blood flow in eight of nine patients in the study, and the effects were "both marked and immediate," according to an article in the journal Science Translational Medicine.
"There is no treatment for this progressive muscle-wasting disease and there has been little research. Previous studies in laboratory mice suggested that drugs such as tadalafil could restore proper blood flow, but this is the first study showing that the drug may offer a therapeutic strategy in humans," said Ronald G. Victor, MD, director of the Cedars-Sinai Hypertension Center of Excellence and associate director of the Cedars-Sinai Heart Institute and the Burns and Allen Chair in Cardiology Research. He is the article's senior author.
Becker muscular dystrophy results from a genetic defect that reduces the amount of a protein called dystrophin in the membrane of muscle cells. With insufficient and poorly functioning dystrophin, patients lose muscle strength and have increased risk of heart failure. Affecting 1 in 19, 000 male births, Becker muscular dystrophy is less common and more slowly progressive - but still debilitating—form of Duchenne muscular dystrophy which eliminates all dystrophin, affects 1 in 3,500 male babies born, and usually appears in early childhood.
Victor led the research team that previously discovered the blood flow abnormality from loss of nitric oxide in the muscles of children with Duchenne muscular dystrophy. The new study shows the same blood flow problem is common in adult patients with Becker muscular dystrophy, thereby offering improved blood circulation as a potential avenue for treatment.