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Merck marks another failure in elusive hunt for Parkinson's disease drugs

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Merck has cut one of most advanced efforts to develop a new therapy for Parkinson's disease. Its Phase III clinical trials of preladenant for the prevalent neurological disorder failed to beat placebo, prompting the U.S. drug giant ($MRK) to halt extension studies of the experimental A2A receptor agonist and abandon plans to file for regulatory approvals for the treatment.

The setback closely follows positive news for Merck's R&D pipeline late Wednesday, when an FDA advisory panel recommended that the regulator approve the company's prized sleep drug suvorexant. Though in late-stage trials, preladenant wasn't one of the hottest prospects from Merck. And analysts had only expected the drug to bring in about $200 million in annual revenue by 2018, ISI Group analyst Mark Schoenebaum wrote in a note to investors.

Nevertheless, the preladenant pratfall underscores the difficulty of finding new treatments for Parkinson's disease, which affects as many as 1 million patients in the U.S. who lack treatments to reverse the chronic illness. Merck tested preladenant in three Phase III trials, two of which combined the experimental drug with standard levodopa and one dosed patients with preladenant alone. Yet none of the studies provided evidence of ample efficacy. 

"Parkinson's disease is very complex, making it difficult to treat patients and develop novel therapeutic approaches," Dr. David Michelson, a vice president of clinical research for neuroscience and ophthalmology at Merck, said in a statement. "We are committed to neuroscience research and will be conducting further analyses of the data to inform the scientific community's efforts in finding new approaches to treat this debilitating disease.

Merck has given up on multiple approaches to treat Parkinson's, which causes the destruction of dopamine-producing brain cells and leads to loss of motor control. Last month the company licensed away an NR2B antagonist called MK-0657 after work on the compound as a Parkinson's treatment. Cerecor, the Baltimore-based licensee of MK-0657, aims to advance the compound for other neurological ailments.

Yet the disease has received some high-profile support from the actor and Parkinson's patient Michael J. Fox, whose foundation has awarded $325 million in research of stem cell treatments and other potential remedies for the disease. Google ($GOOG) co-founder Sergey Brin, who carries a gene for increased risk of developing Parkinson's, has pumped millions of dollars from his personal fortune to advance gene-targeted treatments for the disease.

- here's Merck's release
- see Bloomberg's article

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