Kyowa Hakko Kirin has posted (PDF) a look at proof-of-concept data on adenosine A2A receptor antagonist KW-6356 in early Parkinson’s disease patients. The data emboldened Kyowa to commit to a larger phase 2 trial, despite its one-time partner Lundbeck walking away from the program.

Tokyo-based Kyowa outlicensed the ex-Asia rights to KW-6356 to Lundbeck in 2010 and went on to move the drug into a phase 2 trial in Japan in 2016. Top-line results from the 12-week, 168-patient trial are now in.

Subjects in the high- and low-dose KW-6356 arms experienced improvements on a Parkinson’s motor examination scale of of 4.76 and 5.37, respectively. The scores in the placebo arm improved by 3.14. A 2015 paper found an improvement of 3.25 is needed for clinically pertinent changes to occur, suggesting the gains seen in the treatment arms were meaningful to the lives of the patients.

Kyowa has interpreted the data positively and stepped up plans to initiate a phase 2 trial before the end of the year. However, while that study will keep the program motoring forward in Japan, the fate of the drug is less clear outside of Asia.

Lundbeck held the rights to KW-6356 in these global markets but has opted to return them to Kyowa. Having regained all rights to the drug, Kyowa has decided "to go forward independently with the review of measures to maximize value both in Japan and globally."

Kyowa sees KW-6356 as the successor to Nouriast, another adenosine A2A receptor antagonist. The FDA rejected a filing for approval of Nouriast in 2008 amid concerns about its clinical utility. Kyowa bounced back by winning approval in Japan in 2013, only for a phase 3 flop to dial up doubts about the drug’s efficacy. Despite the phase 3 failure, Kyowa is preparing to file an NDA with the FDA.

Adenosine A2A receptor antagonists have been problematic for other companies, too. Merck took an asset deep into the clinic before data suggested it was no more effective than placebo. More recently, Acorda Therapeutics scrapped development of tozadenant after five people died of sepsis.    

The travails of these and other programs means there remains a need for better Parkinson’s drugs. Kyowa thinks it has such a drug on its hands, and is forging ahead solo. 

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