Penis-Straightening Drug Xiaflex May Provide Relief for Peyronie's

Feb. 5, 2010— -- A new drug for claw hand, a condition that causes bent fingers, may serve double-duty as a penis-straightener. Pfizer's drug Xiaflex was not approved for this, but it may provide much needed relief for those suffering from Peyronie's Disease -- a hard-to-treat condition in which the penis becomes permanently and painfully bent.

"It's a disease that's very frustrating," says Dr. Robert Davis, professor of urology at the University of Rochester, "hitting men in the prime of life," causing pain, sometimes erectile dysfunction, and making it difficult to impossible to have sexual intercourse.

The drug was approved by the Food and Drug Administration Tuesday night explicitly for use against claw hand, but research suggests that Xiaflex is effective in Peyronie's patients as well. The release of the drug this spring may lead to off-label use for Peyronie's Disease.

But Auxilium Pharmaceuticals, Inc., the company developing the drug, says that -- as a safety precaution -- it will do everything it can to discourage off-label use of Xiaflex for Peyronie's.

That is a prospect urologists and patients will find frustrating, Davis says.

In both Peyronie's and claw hand, known clinically as Dupuytren's contracture, an excess buildup of collagen creates scar tissue, preventing normal movement and functioning of the hand or penis.

Xiaflex, delivered in a series of injections to the affected area, works by breaking down the excess collagen with the enzyme collagenase, providing more movement to the extremity.

Painful Penile Problem

Peyronie's Disease, which affects an estimated 1 to 2 percent of the adult male population, is still a bit of a mystery for urologists. One cause is thought to be a poor healing response after there is trauma to the penis, but since it tends to be more common in men of northern European descent, Davis says "there's probably also a genetic component."

"There really aren't any other effective treatments available short of surgery," says Dr. Michael O'Leary, senior urologic surgeon at Brigham and Women's Hospital in Boston.

And surgery is not a particularly attractive option, Davis says. Surgeries, either to shorten the long side of the penis or to lengthen the shorter side with a graft, "have unenviable long-term results," he says, and "you can have damage to the sensory nerves or the skin can stick to the scar and create pain during sex."

While many non-surgical treatments have been tried in the past, from vitamin E supplements to creams to physical therapy with penis pumps, Davis says most have been no more effective than a placebo. He says there is great demand for any drug that could be shown to work.

Xiaflex may be that drug. In current clinical trials, vice president of communications at Auxilium, William Sargent, notes that there was an average 29.7 percent improvement in curvature of the penis, compared with an 11 percent improvement in patients receiving a placebo injection.

But Auxilium has also made it clear that, until the drug is FDA approved for Peyronie's Disease, it will take all necessary precautions to ensure that it is distributed only for use in the hand and not as an off-label drug for urologists.

Auxilium will distribute the drug only to specialists who currently treat Dupuytren's contracture -- hand surgeons, plastic surgeons, rheumatologists and general orthopedic surgeons.

"No one is going to be 100 percent able to prevent [off-label] distribution," Sargent says. "What we're trying to do is limit its use to prevent Dupuytren's disease exclusively -- patient safety is our first priority."

This precaution is "not surprising" says O'Leary, given that any adverse effects from inappropriate use of the drug for Peyronie's "would torpedo any chance that they'll get approval."

But Davis says Peyronie's sufferers may be "very motivated" to take risks, especially since few other treatments work.

"I'm sure there will be pressure [on urologists] to use it off-label, they have been aware of the trials for this drug and certainly have a cohort of patients waiting," he says.

Relief Will Have to Wait

But safety concerns may be justified, says Dr. Tom Lue, professor of urology at the University of California, San Francisco.

"It is an invasive procedure with potential bad side effects [such as] impotence [or] penile fracture. I don't think too many urologists will do off-label use until FDA approval for use in Peyronie's Disease," he says.

Bruising, pain, and swelling at the injection site has also been reported in clinical trials of Xiaflex.

For the moment, doctors and patients will have to await the phase III clinical trial later in the year to see if these side effects will be a deal-breaker for the use of the drug in patients with Peyronie's.

If all goes well, Auxilium says they hope to have the drug approved for Peyronie's within two years.