Three studies on new treatments for Parkinson’s disease address common concerns for patients currently undergoing treatment.
Dr. Robert A. Hauser of the University of South Florida and a fellow of the American Academy of Neurology authored all three studies and will present them at the American Academy of Neurology's 65th Annual Meeting in San Diego next week.
“All of these treatments are promising news for people with Parkinson's disease, which is the second most common neurodegenerative disease after Alzheimer's,” he said in a press release.
Medication is a fact of life for Parkinson’s patients. Because no cure is currently available, treatments only address symptoms, namely motor issues such as tremors, slow movements, stiffness, and lack of balance.
Celebrities like Muhammad Ali, Johnny Cash, and Michael J. Fox have helped raise awareness of the condition, with help from charities that have funneled money into Parkinson's research.
The studies Hauser authored address numerous gaps in current Parkinson’s treatments, paving the way for more effective medications to control the most debilitating symptoms.
None of these treatments, however, has received approval from the U.S. Food and Drug Administration (FDA), so they’re not yet available to patients outside of clinical trials.
When Levodopa "Wears Off"
One new study addressed the “wearing off” effect of levodopa, the most common drug treatment for Parkinson’s. The effect occurs in patients who have been taking the drug for several years and involves a period between doses—sometimes up to six hours—during which the drug is ineffective.
“As each dose wears off, people experience longer periods of time where the motor symptoms do not respond to levodopa,” researchers said in a press release.
Researchers supplemented levodopa treatments with a new trial drug called tozadenant. Half of the 420 patients in the study were given two doses of tozadenant with levodopa, while others were given levodopa and a placebo.
After 12 weeks, those taking levodopa and tozadenant experienced slightly more than one hour of decreased "wear-off" time, along with fewer involuntary muscle movements.
The drug, licensed by Biotie Therapies, will now move into the third phase of development, and patient enrollment in studies is expected to begin in early 2015, according to the company website.
When a Rapid Drop in Blood Pressure Leads to Falls
Many Parkinson’s patients have trouble with balance, particularly a sense of dizziness when standing up. This is caused by a rapid drop in blood pressure when moving from a sitting to a standing position.
This blood pressure drop affects about 18 percent of people with Parkinson’s because their autonomic nervous system—which controls involuntary functions such as heart rate and breathing—fails to release enough norepinephrine, a signalling chemical in the brain.
Researchers administered the drug droxidopa (L-DOPS), which the body converts into norepinephrine, and placebos to 225 Parkinson’s patients in randomized trials. After one week, those taking droxidopa had a two-fold decrease in dizziness and lightheadedness, which translated into fewer falls. After 10 weeks, patients taking droxidopa saw an even greater decrease in their likelihood of falling.
Chelsea Therapeutics, which owns the rights to droxidopa, supported the research after it was accepted for review by the FDA in November of 2011, according to their website.
Rasagiline for Early-stage Parkinson’s Patients
Dopamine agonist drugs are commonly used to treat Parkinson’s because they imitate the way that dopamine, an important neurotransmitter, works in the brain. These drugs include bromocriptine, pramipexole, and ropinirole. They are not considered as effective as levodopa, but are often used when levodopa doesn't work for a particular patient.
Hauser's third study examined 321 patients in the early stages of Parkinson’s disease whose symptoms weren’t controlled by a dopamine agonist drug. For 18 weeks, patients either took the drug rasagiline, an MAOI inhibitor, or a placebo along with their dopamine agonist treatment.
At the end of the study, those patients taking rasagiline improved by 2.4 points on the Parkinson’s disease rating scale, the standard measurement of the severity of a patient's condition. Researchers also said that the side effects of the drug were similar to those of a placebo.
Teva Pharmaceuticals of Israel, which manufactures rasagiline under the brand name Azilect, supported the research. The company began enrollment for a phase IV clinical trial last month, according to a news release.