Organon, the healthcare business of The Netherlands’s Akzo Nobel, has presented promising late-stage data for its experimental antipsychotic asenapine.

Phase III data, presented at the American Psychiatric Association's annual meeting in San Diego, revealed that asenapine significantly improved acute mania symptoms in patients with bipolar I disorder compared to placebo, and had a lower risk of weight gain than Eli Lilly's Zyprexa (olanzapine).

As part of the three-week study, 488 patients with bipolar I disorder experiencing mania or a mixed episode were randomised to three weeks of treatment with either asenapine twice-daily, Zyprexa once-daily, or placebo. 3.1% of patients who received asenapine reported weight gain, compared with 6.9% of those taking the Lilly drug and 1% of patients in the placebo group.

61% of patients taking asenapine reported adverse events, most of which were mild to moderate, including sedation, dizziness, headache and fatigue, compared with 53% on of those taking Zyprexa -- whose reported side effects included sedation, dry mouth and weight gains -- and 36 percent of those given placebos

Robert Hirschfeld, at the Department of Psychiatry and Behavioural Sciences at The University of Texas, said that the results of this trial suggest that “asenapine is an attractive option for the acute treatment of mania because of its rapid onset of action and modest side effect profile.” However Organon was keen to highlight the brevity of the study and more trials need to be done. The drug is also being studied in schizophrenia, and late-stage results for this indication are expected later this year.

The data is a boost for Organon which was jointly developing asenapine with Pfizer before the drugs giant pulled out of the agreement in November, citing commercial interests. The compound is regarded as the most promising in the pipeline at Organon, which is set to be acquired by Schering-Plough.