Switzerland's Addex Pharmaceuticals was dealt a blow late last week when Merck & Co decided to return the rights to a Parkinson's disease programme, adding to a run of bad luck.

Merck licensed rights to a series of orally-active metabotropic glutamate receptor 4 positive allosteric modulators (mGluR4 PAMs) in 2007. The $170.5 million deal included $3 million in upfront payments, $106.5 million in milestone payments for the lead compound and $61 million for follow-up compounds.

Addex blamed the decision on Merck's ongoing restructuring of its R&D pipeline which kicked off last year in the wake of its November 2009 merger with Schering-Plough.

The Swiss company had to embark on some restructuring of its own in July, reducing its workforce by a quarter and narrowing its R&D focus to its core therapeutic areas of central nervous system diseases, metabolism and inflammation. The aim was to cut operating costs by around 8 million francs a year, extending its cash reserves through to the end of 2013.

That announcement followed the departure in June of former chief executive Vincent Mutel, who was replaced by new incumbent Bharatt Chowrira a month later.

Just over 18 months ago Addex was forced to discontinue development of a candidate migraine drug called ADX10059 after patients in a Phase IIb trial developed liver problems whilst on treatment.

The mGluR5 inhibitor was Addex's most-advanced clinical project at the time, but its lead project is now dipraglurant (ADX48621) an mGluR5 negative allosteric modulator or NAM for levodopa-induced dyskinesias in Parkinson's disease patients, and ADX71149, a n mGluR2 PAM for schizophrenia partnered with Jannsen.  Both are currently in Phase IIa testing.

Meanwhile, Addex insists it will continue to develop mGluR4 PAMs in Parkinson's.

"We continue to strongly believe that mGluR4 is a highly attractive target for treating Parkinson's and other serious diseases," said Chowrira.