Istradefylline Now Available for Treatment of Parkinson Off Episodes


The oral selective adenosine A 2A receptor antagonist was approved in August as adjunctive treatment to levodopa/carbidopa for patients with Parkinson disease who experience off episodes.

Peter A. LeWitt, MD

Peter A. LeWitt, MD

Less than 2 months after its FDA approval, istradefylline is now available in the United States as adjunctive treatment to levodopa/carbidopa for patients with Parkinson disease who experience off episodes.2

The drug, which is marketed as Nourianz by Kyowa Kirin, Inc., was approved by the FDA in late August based on results from 4 clinical studies that included more than 1100 participants.2 The oral selective adenosine A 2A receptor antagonist demonstrated statistically significant decreases from baseline in daily off time compared with placebo.

The treatment, which has been approved for use in Japan since May 2013, was initially rejected by the FDA in 2008. At the time, the agency requested additional clinical follow-up data, as well as a summary of nonclinical mineralization findings. Under a Special Protocol Assessment (SPA) agreement with the FDA, the manufacturer launched a phase 3, randomized, placebo-controlled, double-blind study in 2013 in patients with Parkinson disease who were taking a consistent dose of levodopa/carbidopa with or without additional medications for their disease.

Although 12-week data from that study did not demonstrate a statistically significant difference in daily off time from baseline, trends were observed for a greater decrease in off time in the treatment groups (20 mg and 40 mg) compared with placebo. Additional data from an interim analysis reported in 2018 showed that the drug was rated as effective in 61.3% of patients based on the Physician’s Global Assessment. In addition, scores on the Unified Parkinson Disease Rating Scale decreased from 33.7 at baseline to 30.3. Off time was reduced in 38.2% of patients; off-time symptoms were improved or markedly improved in 44.7% of patients; and motor dysfunction was improved or markedly improved in 48.5% of patients.

Notably, the most common adverse effects were dyskinesia, dizziness, constipation, nausea, hallucinations, and insomnia.

“In my clinical practice, I see patients who experience the troublesome effects of Parkinson disease and ‘off’ episodes that interfere with activities of daily living,” said Peter A. LeWitt, MD, professor of neurology, Wayne State University School of Medicine and director, Parkinson's Disease and Movement Disorders Program at Henry Ford Hospital, in a statement.1 “Nourianz represents an important milestone and provides US patients and their caregivers with a nondopaminergic, once-a-day oral treatment option to significantly decrease the amount of ‘off’ time.”

To help offset drug costs and access issues, Kyowa Kirin has launched the Kyowa Kirin Cares program. The program provides access and reimbursement support for patients and caregivers.


1. Kyowa Kirin announces Nourianz™ (istradefylline) now available in the US for treatment of Parkinson’s disease “off” episodes [news release]. Bedminster, NJ: Kyowa Kirin, Inc. October 14, 2019. Accessed October 15, 2019.

2. FDA approves new add-on drug to treat off episodes in adults with Parkinson’s disease [press release]. White Oak, MD: FDA. August 27, 2019. Accessed August 27, 2019.

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