ASTRAZENECA, the Anglo-Swedish pharmaceuticals group, sought to strengthen its grip on the anti-psychotic drugs market yesterday by asking American regulators to approve Seroquel as a one-stop treatment for bipolar disease.

Doctors already are allowed to prescribe the medicine, one of AstraZeneca’s bestselling drugs, to treat patients with bipolar disease when they slip into episodes of mania. The company’s scientists believe that they now have enough scientific data to show that Seroquel can also help sufferers to cope with depression.

If the American authorities accept the findings, Seroquel will become the only drug that can be used to treat both the manic and depressive sides of the disease.

Wayne Macfadden, AstraZeneca’s US medical director, who is in charge of Seroquel, described the regulatory filing as one of the most important milestones in the drug’s history.

Bipolar disorder, which causes sufferers to swing from long periods of depression to short bouts of euphoria, affects more than seven million people in the United States. Patients exhibit severe symptoms for almost half their adult lives and spend about two thirds of their time fighting depression.

Prolonged periods of sadness, unexplained loss of energy, persistent lethargy and recurring suicidal thoughts characterise these depressive episodes. More than half of all sufferers attempt suicide while in the depressed state. The illness is often hard to spot and sufferers can go for more than ten years before it is diagnosed correctly.

Shares in AstraZeneca, Europe’s third-largest drugmaker, jumped 41p to £28.70, a 30-month high, on news of the move. Analysts had expected the company to seek new applications for Seroquel, which already generates sales of about $2 billion (£1.15 billion) a year, after the company published the results of a trial showing that the treatment helped to ease depression.

However, the filing underlines the group’s determination to defend its market-leading position in drugs that treat mental illness. In November AstraZeneca’s lawyers launched proceedings aimed at blocking Teva Pharmaceuticals, an Israeli-based company that specialises in making cheap versions of bestselling drugs, from launching a copy-cat version of Seroquel.

AstraZeneca is committed to defending the patents supporting the science behind the medicine, which extend until 2011 in the United States and 2012 in Europe and Japan.

The filing yesterday will not bolster AstraZeneca’s case against Teva, unless the company changes the physical make-up of Seroquel into a new formulation, which analysts consider unlikely.

However, City-watchers are encouraged that the company is looking at ways to extend the natural life of the drug in the face of aggressive competition from generic manufacturers.

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