Safety and effectiveness of istradefylline in patients with Parkinson's disease: interim analysis of a post-marketing surveillance study in Japan

Background: Istradefylline is a first-in-class, non-dopaminergic, selective adenosine A(2A) receptor antagonist for the treatment of Parkinson's disease (PD) in patients experiencing the wearing-off phenomenon with levodopa (L-DOPA). The authors present an interim report from a post-marketing surveillance (PMS) evaluating the safety and effectiveness of long-term istradefylline in a real-world setting.Research design and methods: Istradefylline safety was assessed by the incidence of adverse events (AE) and adverse drug reactions (ADRs). Effectiveness was assessed using the physician's assessment of off-time, off-time symptoms and motor dysfunction, unified PD rating scale (UPDRS) Part III score, and the physician's global assessment.Results: This analysis evaluated 476 patients. Istradefylline was generally well tolerated, despite dyskinesia and hallucination being the most common ADRs. Reduction in off-time was observed in 38.2% of patients, off-time symptoms were improved or markedly improved in 44.7%, and motor dysfunction was improved or markedly improved in 48.5%. The mean UPDRS Part III score decreased from 33.7 to 30.3 at the end of the study. The physician's global assessment rated the drug as effective in 61.3% of patients.Conclusions: This PMS provides useful safety and effectiveness data for long-term treatment with istradefylline in a real-world setting for patients with PD exhibiting the wearing-off phenomenon with L-DOPA.