Merck & Co. has ended development of preladenant, an experimental drug for Parkinson's disease, after initial data from three late-stage trials proved disappointing.

New Jersey-based Merck said the decision to discontinue the studies was not based on any safety findings.

"Parkinson's disease is very complex, making it difficult to treat patients and develop novel therapeutic approaches," David Michelson, vice president, clinical research, Neuroscience and Ophthalmology at Merck Research Laboratories, 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."

The company said results of the studies will be presented at an upcoming scientific meeting and submitted for publication in a medical journal.

Cowen & Co. had estimated annual sales for preladenant of $200 million by 2016.