New frontiers in the pharmacological management of Parkinson's disease

Abstract

Rasagiline, a selective COMT inhibitor, and rotigotine, a transdermal dopamine (D2) agonist, are two new agents that have been approved in the U.S. and Europe for the treatment of Parkinson's disease. Rasagiline is approved in the U.S. for both monotherapy and as an adjunct to levodopa. Its role in preventing disease progression has yet to be proven, but a large-scale study (ADAGIO) is under way. Rotigotine is approved for early-stage disease in Europe and the U.S. but is only approved in Europe for late-stage disease. It has recently been recalled due to the formation of insoluble crystals that interfere with absorption and may reduce its efficacy. Measures are being taken by the manufacturer to solve this problem. Istradefylline, and adenosine receptor antagonist, showed early promise but efficacy has not been demonstrated consistently, possibly due to higher than expected placebo effect. This has resulted in a nonapprovable letter from the FDA. With regard to perampanel, additional studies are needed to demonstrate safety and efficacy. Sanifamide and pardoprunox are agents that target multiple receptors that may modulate dyskinesia and other nonmotor symptoms in addition to motor symptoms, but phase III data are not yet available. Lusuride is an older dopamine agonist that has been reformulated as a transdermal patch and as a subcutaneous injection and may offer advantages in refractory patients with motor fluctuations. Sphermaine is a novel cell therapy designed to provide a localized source of levodopa directly to the brain. Gene therapies including AAV-GAD, AAV-AADC and AAV2-neurturin are in early stages of development in patients with advanced-stage disease but early safety data are promising.