Sanofi-Aventis said it has completed its takeover of U.S. biotechnology company Genzyme. The companies agreed in February on a deal worth about $20.1 billion. The acquisition gives Sanofi access to Genzyme's business in treating rare diseases and is expected to help the company combat sales erosion from drugs facing cheap generic competition.

Sanofi said more than 237 million Genzyme shares were tendered in the transaction, representing 89.4% of outstanding shares. Sanofi then exercised a top-up option, resulting in ownership of more than 90% of Genzyme's shares.

Sanofi is funding the deal with the proceeds of its $7 billion notes offering, about $7 billion raised through its U.S. commercial paper program, a drawing of $4 billion on a bridge facility and available cash.