The manufacturer of the schizophrenia drug Asenapine has announced a delay.
According to the Dutch company, Akzo Nobel NV, the drug is its most promising experimental medication.
However the drug, which has been developed in conjunction with Pfizer, showed "mixed" results in the latest clinical trials and will not now be put forward for regulation until at least early 2007.
The results of the clinical trials will not be fully evaluated until all the results are available, Akzo has said.
"Some [trial results] still have to come in," the company's chief executive Hans Wijer told Bloomberg.
"As far as the bipolar disorder, the results look OK. As far as the results for schizophrenia, they were mixed, and those mixed results may have created some uncertainty about whether we can file in early 2007 with the FDA,"
It is hoped that the medicine could assist patients with symptoms from paranoia to self-neglect.