Parkinson's Patch Nears U.S. Approval
A once-a-day patch is a safe and effective treatment for early Parkinson's disease, a clinical trial shows.
Transdermal rotigotine is the patch's scientific name. Under the brand name Neupro, it's already sold in Europe by manufacturer Schwarz Pharma.
Study leader Ray L. Watts, M.D., chairman of the neurology department at the University of Alabama at Birmingham, says that what makes the patch unique is its continuous, steady delivery of an effective Parkinson's drug.
"This was the pivotal clinical trial [of the patch] in North America for early Parkinson's disease," Watts tells WebMD. "It showed that this treatment provided a very good benefit for Parkinson's disease symptoms."
Watts and colleagues report the results of the initial six-month study of the Parkinson's patch in the Jan. 23 issue of the journal Neurology. The study shows that 48 percent of people with early Parkinson's disease responded to the drug, vs. 19 percent who responded to an inactive placebo patch. Overall, patients had significantly improved scores on a test of motor function.
Parkinson's disease is caused by the death of brain cells that make an important chemical messenger called dopamine. The drug L-dopa is still the gold standard Parkinson's treatment. It works by giving the brain a precursor compound that brain cells turn into dopamine. It works well — but after about five years, patients have a wearing-off effect at the end of each dose. This effect results in an "on/off" phenomenon when patients suddenly experience erratic, involuntary motions.
The Parkinson's patch gives patients a kind of drug known as a dopamine agonist. It directly plugs in to dopamine receptors on brain cells. This doesn't work quite as well as dopamine itself — but because these drugs have a longer half-life than L-dopa, they smooth out the on/off effect. Half-life is the time that it takes for half of the drug to be broken down by the body.
"There have been several pivotal studies that show if you start patients on a dopamine agonist, you get less of these motor complications after five years," Watts says. "The two currently leading dopamine agonists, Mirapex and Requip, are oral drugs that are shown to do that."
Unfortunately, patients on these drugs may begin to experience the on/off effect as well. It's been thought that this happens because oral medicines can't deliver a steady stream of the drug to the brain. The Parkinson's patch is designed to solve this problem. It bypasses the digestive system and gives a steady supply of the drug to the brain.
"From a potency standpoint, no, this compound is no more potent than other agonists," Watts says. "But this delivery system is unique. Studies in animals show long-acting delivery over short-acting delivery reduces Parkinson's disease symptoms. This long-acting delivery system will be very important, but the longer-term studies have not yet been done."
Parkinson's expert Curt R. Freed, M.D., heads the division of clinical pharmacology and toxicology at the University of Colorado Health Science Center in Denver. In an e-mail interview, Freed says that it's by no means sure that the patch will eliminate the "off" periods seen with L-dopa and oral dopamine agonists.
"The other dopamine agonists have half-lives in the six-hour range, which is nearly as good as continuous administration," Freed tells WebMD. "Patients with advanced Parkinson's disease may have only two clinical states, immobile 'off' and [involuntary movement] 'on.' Whether rotigotine by patch will change this scenario remains to be seen."
Schwarz Pharma Product Director Michael Davis tells WebMD that the FDA has given the Parkinson's patch an "approvable letter." Such letters usually mean that the agency thinks it has enough information to approve the drug.
Davis says the company hopes to hear good news from the FDA in the first half of 2007.
So who will use the drug? Freed says that won't be known until doctors have a chance to see what the drug can do in widespread clinical use.
Watts says that the patch is very likely to be helpful "for an important subset of patients."
"As with any new development and any new treatment for Parkinson's disease, the patch expands the options for patients," Watts says. "This is an important step in the treatment of Parkinson's disease. But there are also many other lines of investigation that will lead to new treatments."
SOURCES: Watts, R.L. Neurology, Jan. 23, 2007; Vol. 68: pp. 272-276. Ray L. Watts, M.D., professor and chairman, department of neurology, University of Alabama at Birmingham. Michael Davis, product director, Schwarz Pharma, Milwaukee. Curt R. Freed, M.D., head, division of clinical pharmacology and toxicology, University of Colorado Health Science Center, Denver.
By Daniel DeNoon
Reviewed by Louise Chang, M.D