Sanofi-Aventis, the French drugmaker, turned its USD 18.5 billion takeover bid for the US biotechnology company Genzyme hostile on Monday but stuck to the same terms, having failed to persuade the Genzyme board to allow it to conduct due diligence.Sanofi Chief Executive Officer Chris Viehbacher said, "We believe the offer will be successful. While Sanofi is still open to talks with Genzyme, he sees no particular reason to bid more." Sanofi is seeking to acquire Genzyme for its drugs that treat rare diseases, like enzyme deficiencies. The biotechnology field has proved more resistant to competition from generics, which are threatening Sanofi's product line and profits.Industry experts said the move was logical, though Sanofi might have to pay more to win the day. The CEO of a rival top-10 drugmaker told Reuters last week Viehbacher had little choice but to "fire a missile" by taking his offer direct to investors. Genzyme was once regarded as a blue chip in the biotech sector, but its shares took a plunge last year after manufacturing issues at one of its key plants led to worldwide shortages of two of its best-selling products.Sanofi said it had secured financing for the cash bid from BNP Paribas and Société Générale in France, as well as J.P. Morgan Europe. The company was advised by Evercore Partners and J.P. Morgan, and has hired Weil, Gotshal & Manges as counsel.