AstraZeneca PLC said the U. S. Food and Drug Administration (FDA) have requested them to supply additional information regarding their application for approval of the supplemental new schizophrenia drug Seroquel.

The drug Seroquel XR is currently approved in the U. S. only for the treatment of schizophrenia or bipolar disease. AstraZeneca, the Anglo-Swedish drug maker has applied to the FDA for approval to target the treatment of major depressive disorder in adult patients with the same drug.

The drug company said the FDA had asked for additional information on the drug in what is called a complete response letter (CRL) to their application.

In a statement to the London Stock Exchange, the company said, "AstraZeneca is evaluating the contents of the CRL and the proposed labeling revisions. AstraZeneca will continue discussions with the FDA and will provide a response to the agency in due course."

Seroquel XR, is one of AstraZeneca's best-selling drugs, but the company was not sure about if and when the approval from the FDA would come for the drug to be used to treat depression in adults.

Sarah Lindgreen, spokeswoman for AstraZeneca said, "At this point in time, we don't know if this means that there will or there won't be a delay, or whether this could lead to no approval."

Seroquel XR, which ranks second in the best sellers list for AstraZeneca just behind heartburn drug Nexium, would continue as an approved drug for both schizophrenia and bipolar disease. The drug clocked sales of US $ 4 billion last year.

AstraZeneca won a case in a U. S. court which meant that generic copies of the drug would not be available for a while.