• Open Access

Adenosine A2A receptor antagonist istradefylline reduces daily OFF time in Parkinson's disease


  • Funding agencies: This study was supported by an unrestricted research grant from Kyowa Hakko Kirin, Co. Ltd., Tokyo, Japan.

  • This study was supported by Kyowa Hakko Kirin Co., Ltd., Japan.

  • Relevant conflicts of interest/financial disclosures: Nothing to report.

  • Full financial disclosures and author roles may be found in the Acknowledgments section online.



We evaluated the efficacy and safety of istradefylline, a selective adenosine A2A receptor antagonist administered as adjunctive treatment to levodopa for 12 weeks in a double-blind manner in Parkinson's disease patients with motor complications in Japan.


A total of 373 subjects were randomized to receive placebo (n = 126), istradefylline 20 mg/day (n = 123), or istradefylline 40 mg/day (n = 124). The primary efficacy variable was the change in daily OFF time. Other secondary variables were also evaluated.


The change in daily OFF time was significantly reduced in the istradefylline 20 mg/day (−0.99 hours, P = .003) and istradefylline 40 mg/day (−0.96 hours, P = .003) groups compared with the placebo group (−0.23 hours). The most common adverse event was dyskinesia (placebo, 4.0%; istradefylline 20 mg/day, 13.0%; istradefylline 40 mg/day, 12.1%).


Istradefylline reduced daily OFF time and was well tolerated in Japanese PD patients with motor complications on levodopa treatment. © 2013 Movement Disorder Society