Biotechnology company Genzyme Corp. said Friday it extended a $580 million tender offer for AnorMed Inc. by one day in order to coincide with the expiration of a regulatory antitrust waiting period.

Cambridge, Mass.-based Genzyme pushed the offer date to the morning of Nov. 7 from Nov. 6. The waiting period under the Hart-Scott-Rodino Act expires just before midnight Nov. 6, barring a request for more information or early termination by the Federal Trade Commission.

As of Oct. 27, just over 52,000 AnorMed shares had been tendered and not withdrawn to Genzyme, the company said.

AnorMed has already agreed to the all-cash buyout offer, which breaks down to $13.50 per share. Genzyme won a bidding war against Millennium Pharmaceuticals Inc. for the Canadian biotech firm, which is developing Mozobil, aimed at promoting stem cell production.

Shares of Genzyme fell 87 cents to $68.80 in afternoon trading on the Nasdaq while shares of AnorMed shed 2 cents to reach $13.41 per share.