LOS ANGELES (Reuters) - Genzyme Corp (GENZ.O: Quote, Profile, Research) said on Monday U.S. regulators asked the company to submit a new drug application before it can market a larger-scale version of Pompe disease treatment Myozyme, which will reduce 2008 sales.

The biotechnology company's shares fell nearly 3 percent in after hours trading.

Genzyme had been seeking approval to market Myozyme produced at a 2000L scale, but said the Food and Drug Administration believes it should be classified as a different product because of the carbohydrate structure of the molecule.

Currently, Genzyme has U.S. approval to sell Myozyme manufactured at the 160L scale.

The company now expects 2008 Myozyme sales of $275 million to $285 million, down from a previous estimate of $320 million to $330 million and said the delay will reduce 2008 adjusted earnings by about 10 cents per share.

Genzyme now expects 2008 adjusted earnings of about $3.90 per share and net earnings of about $2.65 per share.

Myozyme is the only treatment for Pompe disease -- a progressively debilitating and life-threatening inherited disorder affecting a very small number of people throughout the world.

"We are extremely disappointed in the FDA's decision because it will further delay broad patient access to Myozyme," Henri Termeer, Genzyme's chairman and chief executive officer, said in a statement.

The company expects the FDA to act on the application by the end of the year and it expects to begin providing U.S. patients with commercial 2000L Myozyme during the first quarter of 2009.