The Food and Drug Administration on Wednesday asked British pharmaceutical major AstraZeneca Plc . for the supplemental New Drug Application for Seroquel XR, the extended release tablets for treating major depressive disorder , or MDD, in adult patients.

Seroquel already was approved in the U.S. in 2007 for the acute and maintenance treatment of schizophrenia in adult patients. In October, 2008, the drug was approved in U.S. for the acute treatment of the depressive episodes associated with bipolar disorder, the manic and mixed episodes associated with bipolar I disorder, and the maintenance treatment of bipolar I disorder as adjunctive therapy to lithium or divalproex.

Analysts said the FDA request for information could lead to a two-year delay.

“AstraZeneca is evaluating the contents of the CRL [the Complete Response Letter] and the proposed labeling revisions. AstraZeneca will continue discussions with the FDA and will provide a response to the agency in due course,” the company said in a statement to the London Stock Exchange.

The company added that the FDA letter does not change the current recommendations for the treatment of patients using the drug in schizophrenia and bi-polar disorder. Seroquel is AstraZeneca's second-best seller behind heartburn drug Nexium, raking in US$4 billion in sales last year.

AstraZeneca closed its trading on Tuesday at $39.72, down $0.58 or 1.44%, on a volume of 819 thousand shares. In the past 52 weeks, shares have been trading in a range of $32.58 - $49.85.

AstraZeneca is currently trading on the LSE at 2,664 pence, down 47 pence or 1.73%, on a volume of 156 thousand shares.