Today, Biotie Therapies is announcing positive clinical study results into a novel approach to treat the symptoms of Parkinson’s disease (PD): In a phase 2b trial, Biotie’s drug tozadenant was found to significantly limit the “off periods” that many with Parkinson’s experience when taking levodopa, the gold standard therapy for the disease. 

Levodopa works by targeting a chemical in the brain called dopamine that helps to control movement, balance and walking. Lack of dopamine is the primary cause of Parkinson's motor symptoms. Enhancing, or mimicking, its activity are the primary approaches that current drugs take to improve these symptoms. But often, the effects of levodopa wear off before patients are ready to take their next dose. 

Tozadenant works by targeting a different brain chemical altogether, called adenosine.  Specifically, the drug blocks the activity of an adenosine receptor called A2a, which in turn, seems to enhance dopamine’s effect in a particular area of the brain. At the same time, the effect of another brain chemical called glutamate, which when perturbed is thought to cause a troubling side effect called dyskinesia, may be inhibited through this process.

In short: tozadenant could mean better motor function for people with PD, with more “on” time when the drug is effective.

Biotie says that the next step for their drug is to enter into a larger scale phase 3 trial, to learn more about the efficacy of the drug. They have partnered with pharmaceutical company UCB, and will discuss next steps in early 2013. Merck already has a Parkinson’s drug targeting adenosine in the third phase of clinical testing. 

Other researchers investigating adenosine’s role in Parkinson’s are turning to a different type of therapy – coffee. Studies have shown that caffeine may also block adenosine receptors, which could lead to higher levels of dopamine in the brain.   

The results from Biotie mark the latest of several positive clinical studies into approaches to treat Parkinson’s that don’t focus on the dopamine system. Other so-called “non-dopaminergic” drug candidates that returned positive clinical results in 2012 include:

Dipraglurant, a therapy from Addex Therapeutics, targets the brain’s glutamate system to limit dyskinesia in people with PD. 

Pimavanserin, a drug from Acadia Pharmaceuticals, targets the brain’s serotonin system in treating the psychosis that is sometimes a side effect of Parkinson’s medications.