Influence of istradefylline on non-motor symptoms of Parkinson's disease: A subanalysis of a 1-year observational study in Japan (J-FIRST)

Introduction: The non-motor symptoms (NMSs) of Parkinson's disease (PD) significantly impact the patient's health-related quality of life. This subanalysis of the J-FIRST study evaluated the effect of istradefylline, a selective adenosine A_2A receptor antagonist, on NMSs in istradefylline-naïve Japanese patients with PD. Methods: Patients with PD and ≥1 NMS and ‘wearing-off’ with their current antiparkinsonian treatment were observed for up to 52 weeks. The effect of istradefylline on NMSs was measured in terms of changes in the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part 1 total, individual sub-items scores and the 8 item PD questionnaire (PDQ-8) estimated by the marginal structural model. Results: Overall, 732 patients were istradefylline-naïve prior to the study, of whom 171 were treated with istradefylline for ≥8 weeks during the observation period (istradefylline-treated patients). At baseline, istradefylline-treated patients were more likely to have a dyskinesia (49.7% vs 40.8%) and received a significantly higher daily dose of levodopa (462.8 mg vs 413.0 mg) than those who did not receive istradefylline (n = 561). MDS-UPDRS Part 1 total score at the end of the 52-week observational period slightly increased in patients who received istradefylline and those who did not (0.49 ± 0.41 vs 0.07 ± 0.20; P = 0.36). There were no statistically significant differences between the two groups of patients in terms of changes in the MDS-UPDRS Part 1 total score or any sub-items, or in the PDQ-8 total score. Conclusion: NMSs remained generally controlled in istradefylline-treated Japanese patients with PD who exhibited wearing-off with their current antiparkinsonian treatment. Istradefylline could be a feasible treatment option for patients with advanced PD, without worsening existing NMSs.