Merck Stops Developing Parkinson's Drug After Lackluster Clinical Results

Merck & Co. has ceased development of its experimental therapy for Parkinson’s disease after the drug failed to show superiority to placebo in initial data from a series of phase III clinical trials.

In a statement announcing the pharmaceutical company’s plans to halt its clinical program for preladenant — an investigational adenosine A2_A receptor antagonist intended to treat Parkinson’s disease — David Michelson, vice president of clinical research in neuroscience and ophthalmology at Merck Research Laboratories, explained that the neurological disorder “is very complex, making it difficult to treat patients and develop novel therapeutic approaches.”

Nevertheless, Michelson said preladenant’s clinical program was “an important example of Merck’s continued commitment to pursue promising science with the goal of bringing forward medicines that address important unmet medical needs.”

Merck said its decision to abandon plans to pursue regulatory approvals of preladenant was not based on any safety findings, but rather initial results from three late-stage clinical trials showing no difference in efficacy for preladenant compared to placebo.

Two of those studies launched in July 2010 and added the drug to levodopa therapy in patients with early or moderate-to-severe forms of Parkinson’s disease, while the third study launched in November 2010 and tested preladenant as monotherapy in moderate-to-severe forms of the neurological disorder.

Though Merck said it will discontinue the extension portions of those studies, Michelson noted the company is still “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 also said it will present the primary outcomes of preladenant’s three late-stage clinical trials at a future scientific meeting, as well as submit them for publication in a medical journal.