Clinical trials show Xiaflex may reduce penile curvature in Peyronie's… (National Library of Medicine/National…)
A drug already on the market to treat severely clenched fingers may also be useful in treating the excessively curved penis caused by Peyronie's disease, researchers reported Monday. If the findings are validated in larger trials, the drug, called Xiaflex, could become the first effective medical treatment for the condition, which apart from embarrassment can cause impotence and pain. The company that manufactures the drug, Auxilium Pharmaceuticals Inc. of Malvern, Pa., said it hopes to have approval from the Food and Drug Administration to market the drug for this purpose by the end of the year.
Peyronie's disease is caused by the accumulation of collagen plaque, or scar tissue, on the shaft of the penis. The plaque can harden and contract, causing the penis to bend severely. In addition to pain and difficulty with sexual intercourse, the disease is also marked by emotional distress, loss of self-esteem and depression. No good data is available about the incidence of Peyronie's -- in part, researchers say, because many men are too embarrassed to report it -- but some estimates are that the prevalence among adult men approaches 5%. Based on medical claims data, Auxilium researchers estimate that 65,000 to 120,000 new cases are diagnosed each year.
The only approved treatment for penile curvature is surgery, in which surgeons scrape out the excess plaque manually. But the procedure can lead to erectile dysfunction and shortening of the penis, and is viewed as a last resort by both doctors and patients. No more than 6,500 U.S. men undergo such surgery each year.
Xiaflex, known generically as collagenase clostridium histolyticum, is an enzyme that attacks the collagen plaque. It was approved in 2010 for the treatment of Dupuytren's contracture, a disorder in which collagen buildup in the fingers causes them to clench permanently. Its primary side effects are hematoma (accumulation of blood), pain and swelling at the injection site.
In two separate trials sponsored by Auxilium, each enrolling 400 patients, men were treated with either Xiaflex or placebo at a 2:1 ratio. Treatment involves as many as eight injections of the drug into the penile plaque over a period of a few months. Physicians may also manipulate the penis manually to help break up the plaque. The company reported in a press release that the treatment yielded a 37.6 reduction in penile curvature in one trial and a 30.5% reduction in the second. The treatment course also improved quality of life related to the curvature. In one trial, for example, the average deformity of the penis at the beginning of the study was 48.8 degrees in men receiving the drug and 49 degrees in those receiving placebo. After 52 weeks, the deformity was only 31 degrees in men receiving Xiaflex and 39 degrees in those receiving placebo.
The results "are not overwhelming and dramatic," Dr. Culley Carson, a urologist at the University of North Carolina who was one of the trial investigators, told the New York Times. But, he added, "it's a major advantage over what we have now, which is nothing."
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