On Monday, sanofi-aventis (Paris) began a hostile tender offer of $69 per share for all outstanding shares of Genzyme (Cambridge, MA). The transaction is valued at approximately $18.5 billion. sanofi-aventis’s board of directors unanimously approved the offer, which is scheduled to expire on Dec. 10, 2010.

sanofi’s latest offer is similar to previous public and nonpublic offers that it made to Genzyme in July and August of 2010. In company press releases, Henri Termeer, Genzyme’s CEO, rejected both previous offers as “opportunistic.”

In a press statement, Christopher A. Viehbacher, CEO of sanofi-aventis, said that his company had intended to reach an agreement about the acquisition with Genzyme’s board, “but our attempts to do so have been blocked at every turn.” After sanofi requested a meeting with Genzyme several times, the two companies met on Sept. 20, 2010. In a letter to Termeer, Viehbacher said that “this meeting was not productive.”

“Our recent meetings with Genzyme shareholders demonstrate that they support a transaction and are frustrated by Genzyme’s unwillingness to engage in constructive discussions with us,” Viehbacher said in the press statement. “This has left us with no choice but to present the offer directly to Genzyme’s shareholders. We strongly believe our offer price of $69 per share in cash represents a compelling value for Genzyme shareholders,” he added.

After an acquisition, sanofi would invest in developing new treatments for Genzyme, enhancing the latter company’s penetration in existing markets, and helping it expand into emerging markets. In his letter, Viehbacher said that sanofi was well positioned to help Genzyme address its manufacturing problems. Upon completion of the transaction, Genzyme would become sanofi’s global center for excellence in rare diseases. sanofi would manage Genzyme as a stand-alone division with its own research and development, manufacturing, and commercial infrastructure, said Viehbacher.

After hearing of the hostile offer, Genzyme’s board of directors urged the company’s shareholders to take no action on it. On Monday, Genzyme’s board said it would review the offer with its financial and legal advisors and would advise shareholders of its formal position within 10 business days.

See related PharmTech articles:

Genzyme Rejects Sanofi-Aventis's Acquisition Proposal (ePT)

Sanofi’s Courtship of Genzyme in Limbo (blog post)

Will Sanofi Bag Genzyme? (blog post)