UPDATE 2-Genzyme's Pompe drug review set for June 17

* Genzyme's Lumizyme gets 6-month review

* Shares of Genzyme down 1 pct, less than broader index (Updates with background related to approval process)

BOSTON Jan 21 (Reuters) - Genzyme Corp GENZ.O said on Thursday that U.S. regulators have agreed to rule on whether to approve its Pompe disease drug Lumizyme by June 17.

Lumizyme is a scaled-up version of the company's Pompe disease drug Myozyme, which was approved in 2006.

Lumizyme is produced in 4,000-liter bioreactors at the company's manufacturing plant in Geel, Belgium, and is sold outside the United States as Myozyme.

Myozyme was approved for use in the United States when made at a 160-liter scale. Because supplies were small, the drug was reserved for infants, in whom the disease tends to be more severe.

Genzyme subsequently applied for U.S. approval for a 2,000-liter version of the drug, but the U.S. Food and Drug Administration said that when produced in larger quantities, the drug has a different carbohydrate structure and therefore needs to be approved separately.

The drug would therefore need to be marketed under a different name - Lumizyme.

Pompe disease affects some 5,000 to 10,000 people worldwide, and often kills babies before they reach the age of two.

People with the disease are deficient in an enzyme known as acid alpha-glucosidase, which is responsible for breaking down glycogen, a form of sugar stored in muscle cells. When glycogen builds up in these cells it can cause swelling of the heart and other organs and lead to disability and death.

ALLSTON PLANT

The 2,000-liter product, made in the company's Allston Landing plant in Boston, was approved in other countries and Genzyme supplied the rest of the world out of Allston.

In the meantime, it built a new facility in Belgium, with two 4,000-liter bioreactors. Patients outside the United States have been transitioned from the 2,000-liter version of the drug to the 4,000-liter version.

The FDA declined to approve the 2,000-liter version in the United States until the company fixed a series of quality control failures. Genzyme subsequently stopped making the 2,000-liter version in Boston and now only makes the 4,000-liter version, in Belgium.

In December, Genzyme said it had agreed with the FDA on a plan that could lead to approval of the 4,000-liter version, skipping the need for approval of the 2,000-liter version.

The company, which submitted its revised application in December, said the FDA has given the drug a six-month review period from the date of the resubmission - or June 17.

Unless Lumizyme is approved, the company will not have enough commercial product to meet demand in the United States. In the meantime it is providing severely affected adults with Lumizyme free of charge.

Genzyme's shares were down 1 percent to $54.29 in early afternoon trading on Nasdaq, outperforming a 2 percent decline in the NYSE Arca Biotech Index .BTK. (Reporting by Toni Clarke; Editing by Gerald E. McCormick and Tim Dobbyn)