Pharmaceutical company SkyePharma PLC (SKP.LN) warned Tuesday the launch of its asthma treatment Flutiform is likely to be delayed by another year after U.S. regulators demanded more research.

London-based SkyePharma received a letter from the U.S. Food and Drug Administration in June, following its submission of Flutiform for marketing approval. The company said at the time the letter suggested further work might be required for Flutiform before the FDA approves it for sale.

SkyePharma said Tuesday that a meeting has now been held with the FDA and additional clinical work will be required to provide more data on the effect of the drug at various doses.

SkyePharma had hoped Flutiform would go on sale in 2010 but Tuesday said it is now unlikely the drug will be approved in the U.S. before the second half of 2011.

Matrix Corporate Capital analyst Navid Malik said the FDA's stance was not wholly surprising. Asthma treatments are a tough area to gain approval, he said with "high hurdle rates" for safety. "It's a pretty tough call," he said, "but there was always a risk of delay."

The company had held talks about a submission as early as 2007 but had to perform an additional Phase III trial after the FDA asked for more data then.

It doesn't look like another big trial will be required but the latest delay is yet another frustration for investors, said Singer Capital Markets analyst Shawn Manning.

At 1101 GMT, SkyePharma shares traded down 12 pence, or 11% lower at 101 pence in a broadly weaker London market. The stock has lost 42% of its value over the past three months.

Still, Manning said he reckons Flutiform could do brisk business once it does get to market. Products similar to Flutiform generate sales of about $29 billion a year, and Manning said he estimates Flutiform could sell between $300 million and $400 million a year.

However, other drug makers are working on newer products too, notably Schering-Plough Corp. (SGP) and Novartis AG (NOVN.VX), and aren't far from getting their regulatory submissions in.

When it does get to market, Flutiform might also have to compete with cheaper generic versions of some of today's blockbuster asthma drugs, like GlaxoSmithKline PLC's (GSK.LN) Advair.

The additional research required by the FDA is not expected to have an impact on the Flutiform development in Europe or Japan, Skyepharma added Tuesday.

Marketing partner Abbott Laboratories (ABT) is responsible for paying for additional clinical or other trials required by the FDA, and is entitled to recoup such costs once approval is granted.

Company Web site: www.SkyePharma.com

-By Michael Carolan, Dow Jones Newswires; 44-20-7842-9278; michael.carolan@dowjones.com