AstraZeneca is seeking approval from US regulators to market an extended-release version of its blockbuster Seroquel to treat both manic and depressive episodes associated with bipolar disorder.

The Anglo-Swedish drugmaker has submitted two separate supplemental New Drug Applications to the US Food and Drug Administration for once-daily Seroquel XR (quetiapine fumarate) extended-release tablets. The new version was launched for the treatment of schizophrenia in the USA in 2007 and is available in seven other countries.

The submissions are based on clinical data which showed that 316 patients with bipolar mania and 280 patients with bipolar depression who received Seroquel XR once daily experienced significant reductions in symptom severity compared with those on placebo. The effect was seen with all of the doses (300mg up to 800mg).

Approvals for the sNDAs would provide a further boost for AstraZeneca’s Seroquel franchise which enjoyed a 15% increase in nine-month sales to $2.94 billion. Seroquel is facing generic competition and the extended-release version is seen as a valuable way of extending the product’s life cycle.