Genzyme Corp. (GENZ) on Wednesday said it has signed an agreement to buy Bone Care International (BCII) for $600 million in cash, and acquire a drug for kidney disease that would complement its own popular kidney medicine.

The deal would give Genzyme (search), which sells the drug Renagel (search) for late-stage kidney disease, Bone Care's Hectorol (search) line of vitamin D2 pro-hormone products used to treat secondary hyperparathyroidism in patients on dialysis.

Genzyme said it hopes to complete the purchase in the third quarter and that the deal should be neutral to 2005 earnings, and afterward boost earnings.

It said Bone Care would return $119 million in cash to Genzyme, which initially will put about $719 million on the table.

Renagel, which has annual sales of about $400 million, helps limit the buildup of phosphorus levels among those undergoing dialysis. Hectoral, Bone Care's only marketed product which has annual sales of over $80 million, helps restore vitamin D levels of patients undergoing dialysis as well as those with earlier-stage kidney disease.

Patients with kidney failure gradually lose the ability to convert vitamin D from sunlight and other sources into an active form that can be used by the body.

Many dialysis patients receive injections of an activated form of vitamin D to counteract secondary hyperparathyroidism — a side effect of vitamin D deficiency that can harm bones and muscles and cause cardiovascular disease and increased risk of death.

Genzyme said it will sell Hectoral in the United States, and will begin preparations to seek marketing approval for the product in other countries.

Shares of Genzyme were down 70 cents, or 1.2 percent, to $59.20, in morning trade on the Nasdaq. Shares of Bone Care jumped $8.48, or 36 percent, to a 52-week high of $32.31, also on the Nasdaq.