Sept 4 (Reuters) - Alexion Pharmaceuticals Inc said the U.S. Food and Drug Administration would delay by three months its decision on approving a key drug the company got through the acquisition of Synageva BioPharma Corp.

European health regulators on Tuesday approved the drug, Kanuma, to treat lysosomal acid lipase deficiency (LAL-D), a progressive metabolic disease that often leads to liver failure, multi-organ damage and premature death.

The FDA, which has granted the drug "breakthrough therapy" status for LAL deficiency in infants, was expected to make its decision by Sept. 8.

Alexion said on Friday it had submitted some additional "chemistry, manufacturing and controls" information that the FDA asked for, and that the timing of the submission had caused the delay.

The regulator has not asked for any addition clinical data on the enzyme-replacement therapy for the ultra-rare, life threatening disease, the company said.

An application to market Kanuma in Japan has also been submitted.

Kanuma could eventually bring in than $1 billion in annual sales, Alexion Chief Executive David Hallal told Reuters earlier this week.

On Tuesday, European health regulators also approved Alexion's Strensiq to treat pediatric-onset hypophosphatasia (HPP), a potentially fatal disease that can lead to bone deformity, fractures and other skeletal abnormalities.

Prior to these approvals, Alexion's sole approved drug was Soliris, which treats two rare and life-threatening diseases: Paroxysmal nocturnal hemoglobinuria, and Atypical hemolytic uremic syndrome. It raked in sales of $2.23 billion last year.

Alexion's shares closed at $175.28 on Thursday.

(Reporting by Natalie Grover in Bengaluru; Editing by Savio D'Souza)