Potential new drug may slow the progression of the Parkinson's disease

An international team of Parkinson's disease researchers has shown that a potential new drug is effective at treating patients in the early stages of Parkinson's and may even slow the progression of the disease. The results from the Parkinson Study Group are in the April 19 issue of the Archives of Neurology.

The effects of the compound rasagiline were measured in a study of 371 patients with early Parkinson's disease. Using a common method to measure the effects of the disease, researchers with the Parkinson Study Group showed that the drug helps treat many of the symptoms of the disease, allowing people to better carry out such everyday tasks like cutting food, writing, and dressing oneself.

While the improvement in symptoms was in line with that offered by other medications on the market, the drug generally caused fewer side effects than many Parkinson's drugs, researchers say, including less sleepiness and nausea and fewer hallucinations.

In this study the researchers also sought to separate out the short-term and long-term effects of the medication. While physicians can assess the impact of a medication on a patient's symptoms, it's difficult to know whether it is actually slowing the progression of Parkinson's disease, says neurologist Ira Shoulson, M.D., of the University of Rochester, the principal investigator of the study.

"With cancer, for instance, you can look at a tumor and watch what happens – if the tumor shrinks, you know the medication is having an effect on the cause of the patient's symptoms. But we don't have such clear biomarkers for Parkinson's disease, though we're working to develop them."

So the investigators created a unique type of study to address the question. Some people in the "delayed-start study" received the medication for the entire year of the study, while others received it only for the last six months. The investigators found that the people who received rasagaline for only the last six months improved compared with their own performance in first 6 months, but they never reached the level of improvement attained by the people who received rasagiline continuously for the entire 12 months. The result could be a sign that the medication actually helps to protect the brain cells targeted by the disease.

"Very frequently drugs will reduce symptoms of Parkinson's disease in the short term, but it's also possible that they have long-term consequences such as possibly slowing the rate of progression of the disease," says Andrew Siderowf, M.D., the corresponding author and assistant professor of neurology at the University of Pennsylvania. "This study helps disentangle the short-term and long-term consequences of therapy and tease out whether an effect on the underlying disease process could be present."

Other scientists have shown in the laboratory that rasagaline appears to protect nerve cells affected by Parkinson's disease from apoptosis, or programmed cell death.

"The innovative design of the study suggests that the medication may modify the course of the disease. But this is just a first hint of this clinically – more studies need to be done to see if rasagaline truly modifies the course of Parkinson's disease," adds Shoulson.

The study was done at 32 sites of the Parkinson Study Group in the United States and Canada. The PSG is an independent group of investigators at academic institutions around the world led by physicians at the University of Rochester Medical Center. The group is committed to improving treatment for persons affected by Parkinson's disease, which affects an estimated 1 million people in North America. Hallmarks of the neurodegenerative disease include tremors, rigidity, and stiff or slow movement.

The study was funded by the maker of rasagaline, Teva Pharmaceuticals, which has applied to the U.S. Food and Drug Administration for approval of the drug.