* Genzyme says 6-month delay could crimp 2009 profit

* Says post-approval study still in planning stage

* Says working on plan to ensure appropriate use of drug (Describes reasons for rejection, delay)

NEW YORK, March 2 (Reuters) - U.S. regulators have declined to approve Genzyme Corp's (GENZ.O: Quote, Profile, Research) new Lumizyme treatment for Pompe disease, a setback the drugmaker said could delay its approval for six months and crimp 2009 earnings.

Genzyme, whose shares fell more than 5 percent in after-hours activity, currently sells Myozyme to treat the rare and often-fatal inherited disorder. But because Myozyme is made in relatively small 160-liter batches in the United States, the drug is only commercially available to children and infants.

The biotechnology company had asked the U.S. Food and Drug Administration for permission to make Myozyme in 2000-liter batches, in order to ease supply restraints and make the product available to adult patients. It is approved by more than 40 countries from such larger batches.

But the FDA determined that the drug coming out of the 2000-liter batches was chemically slightly different than Myozyme, and that it needed to be approved as a separate medicine under a separate name.

Genzyme on Monday said several remaining issues need to be addressed before the FDA can approve its marketing application for Lumizyme.

"Assuming a six-month delay, Genzyme anticipates the impact on 2009 non-GAAP earnings will be approximately 12 cents per share," Genzyme said in a release.