May 18 (Bloomberg) -- AstraZeneca Plc's once-a-day version of the schizophrenia pill Seroquel won U.S. regulatory approval, securing patent exclusivity for the U.K. drugmaker's second-best selling product for another 10 years.

The U.S. Food and Drug Administration approved Seroquel XR for use in adults with schizophrenia, London-based AstraZeneca said in a statement today. Seroquel XR will be introduced in the U.S. in the second half of the year, where it has patent protection until 2017.

AstraZeneca is expanding uses and formulations of its older best-selling products, such as ulcer pill Nexium, Seroquel and Crestor for cholesterol, to help profit after several research setbacks in the past two years. Seroquel sales are likely to jump 29 percent this year to $4.4 billion, according to David Seemungal, an analyst at Standard and Poor's in London.

``It's a patent defense strategy,'' Max Herrmann, analyst at ING Financial Markets, said in a May 15 interview. ``It should improve the profile of the product but not significantly, given that it has been very successful so far. The top priority is to try to defend the franchise from generics.''

Chief Executive Officer David Brennan said the company can expand the drug's use for schizophrenia, as well as major depression and anxiety disorder. The new version is crucial for AstraZeneca to keep market share, as it is trying to block Teva Pharmaceutical Industries Ltd. and Novartis AG, the world's two largest makers of generic medicines, from introducing cheap copies of Seroquel.

Optimistic Brennan

``I'm optimistic,'' Brennan said in an interview in Boston, where he was attending the Biotechnology Industry Organization conference. ``If predictions hold up, the Seroquel franchise should increase.''

Shares in AstraZeneca rose 3 pence to 2,748 pence at the close of trading in London. They're little changed this year.

Seroquel, which was first approved a decade ago, has been used by more than 7 million people worldwide who take the current formulation twice a day. Reaching an effective dose can take up to seven days with the current pills, compared with the new sustained release version, which is effective from day two, according to a recent study.

Schizophrenia is a brain disorder characterized by a distorted perception of reality, hallucinations and delusions. It affects over 2 million U.S. adults, or about 1 percent of the adult population.

Sales Growth

London-based analyst Datamonitor estimates sales of drugs for bipolar disorder totaled $5.8 billion in 2006, while sales for schizophrenia treatments were $3.5 billion and major depressive disorder came to $11 billion.

AstraZeneca is studying Seroquel's use in adolescent mental illness and plans to seek permission to prescribe it for generalized anxiety and major depressive disorder in 2009.

About 50 percent of Seroquel sales come from unapproved uses, such as Alzheimer's disease and adolescent mental illness and studies are looking at its use against dementia, substance dependency, children and adolescents with bi-polar disorder and children with schizophrenia, and obsessive compulsive disorders, among other conditions.

``The reason why these drugs are being used is a lack of other options,'' Datamonitor analyst Dr. Terence McManus said in March. ``I don't think they're actively doing this in an illegal way. They have no other choice than to try the options that are available to them.''

To contact the reporter on this story: Etain Lavelle in London at at elavelle1@bloomberg.net.

Last Updated: May 18, 2007 11:44 EDT