Tozadenant (SYN115) is an adenosine A2A receptor antagonist initially developed for treatment of Parkinson's disease but may also have utility in other CNS disorders. A2a receptors are expressed in high concentration in the striatum of the brain and play an important role in regulating motor function. Tozadenant blocks the effect of endogenous adenosine at the A2a receptors, resulting in the potentiation of the effect of dopamine at the D2 receptor and inhibition of the effect of glutamate at the mGluR5 receptor. This enables restoration of motor function in Parkinson’s disease. Tozadenant has the potential for use as mono-therapy or adjunctive therapy in combination with L-Dopa and dopamine agonists for the treatment of the motor and non-motor symptoms associated with Parkinson’s disease. may also have neuroprotective effects, which raises the possibility that it could slow the deterioration of dopamine producing cells and modify disease progression. As was reported in international, multicentre, phase 2b, randomised, double-blind, placebo-controlled, parallel-group, dose-finding clinical trial of tozadenant in levodopa-treated patients with Parkinson's disease who had motor fluctuations tozadenant at 120 or 180 mg twice daily was generally well tolerated and was effective at reducing off-time.