The phase 3 clinical program for Merck's (MRK -0.05%) new drug preladenant, a receptor antagonist in the treatment of Parkinson's disease, will be discontinued based on a lack of efficacy compared to a placebo, the company announced yesterday. After studying the results of three independent phase 3 clinical trials, Merck has decided to "discontinue the extension phases of these studies and no longer plans to pursue regulatory filings for preladenant," the company said in a statement.

In response to the preladenant trial results, Dr. David Michelson, vice president of clinical research, neuroscience, and ophthalmology at Merck research laboratories, said, "Parkinson's disease is very complex, making it difficult to treat patients and develop novel therapeutic approaches."

Merck intends to conduct further studies of the preladenant trial's results and will share its data with the scientific community in an effort to find "new approaches to treat this debilitating disease."