UPDATE 1-Lundbeck delays US drug application, shares dive

* New anti-depressant drug application delayed 18-24 months

* Phase III trial show insignificant effect vs placebo

* Shares fall 16 percent at 1302 GMT

(Add detail, company and analyst comments, share price)

By Peter Levring

COPENHAGEN, June 8 (Reuters) - Drug maker Lundbeck (LUN.CO) said on Monday a U.S. application for its anti-depressant Lu AA21004 would be delayed after Phase III trials showed insignificant effects compared to placebo, knocking its shares.

The Danish group said development of the new drug, which is eyed to fill part of a revenue gap once patents for Lundbeck's blockbuster anti-depressant Cipralex, called Lexapro in the United States, expire in 2012, would be delayed by 18-24 months.

Lexapro revenues were 626 million Danish crowns ($116.3 million) and Cipralex 1.36 billion in the first quarter of 2009, making up 61 percent of a total revenue of 3.23 billion.

"As a result, the most appropriate dose for Lu AA21004 needs to be established. It is anticipated that this work will postpone submission of the new drug application (NDA)," Lundbeck said in a statement.

Lundbeck now expects to file its NDA in the United States at the earliest in late 2011 or early 2012, its Chief Scientific Officer Anders Pedersen said.

"Studies of lower doses did not show an adequate effect. Thus we don't have sufficient data to support the timetable for registering the drug," Pedersen said.

Pedersen said that the candidate drug did not show significant response compared with placebo in testing with 2.5 milligrams doses in Phase III trials, but did show a substantial effect when tested with 5 and 10 milligrams doses.

Lundbeck shares dropped sharply on the news and remained down nearly 16 percent at 1302 GMT, against a 1.7 percent drop in the wider Copenhagen market and modestly firming in the DJ Stoxx Health Index .SXDP.

"This is very negative. It shows the tested doses didn't have any effect and raises questions whether Lu21004 will ever reach the market," Sydbank analyst Rune Dahl said.

"It's impossible to avoid a decline in revenues when the lexapro patent runs out in 2012... This is probably the most important drug in the company's pipeline.

($1=5.384 Danish Crown)

(Additional reporting by Karin Jensen and Teis Jensen, editing by David Cowell)