New data presented at the American Psychiatric Association meeting in Toronto show AstraZeneca's atypical antipsychotic Seroquel works rapidly and effectively in relieving bipolar depression, and could emerge as a single-agent therapy for the condition.

Seroquel (quetiapine) is already licensed as a treatment for bipolar mania and is now awaiting FDA approval to tackle depressive symptoms. An application for bipolar depression was filed with the FDA December 2005.

Results of the BOLDER II study backed up findings of the earlier BOLDER 1 study of the same design showing that either one of two doses of Seroquel (300mg or 600mg) is significantly more effective than placebo in relieving bipolar depression.

Principal investigator Dr Michael Thase of University of Pittsburgh Medical Center said the two BOLDER studies paved the way for a monotherapy approach to managing bipolar disorder in future. “Psychiatrists should be able to use one medicine instead of three or four. Currently patients can get one drug to treat manic episodes, one to stabilise mood and a combination of drugs to treat depression.”

Other data presented at APA by AstraZeneca's US medical director for Seroquel, Dr Wayne McFadden, showed the drug might help prevent suicides among bipolar patients according to measures of suicidal thoughts. Up to one half of all bipolar patients attempt suicide in their lifetime.

Seroquel is already the market-leading antipsychotic in the USA, grossing sales of $2.8 billion in 2005 for 12.65 million treatments. Atypical antipsychotics account for over 92% of all US antipsychotic sales worth $10.5 billion in total. The worldwide atypical antipsychotic market is worth $14 billion.

Bipolar depression represents a substantial market in the USA with around 1.8 million adults suffering the more severe bipolar I disorder and an estimated 3% to 5% of the population suffering from bipolar II. Patients typically experience three times as many depressive as manic episodes. “Bipolar depression accounts for a third of all depressive illness in the US,” commented Dr Thase.

AZ is now conducting an additional bipolar study programme, EMBOLDEN, for Seroquel in Europe.

From Olwen Glynn Owen in Toronto