French drug maker Sanofi-Aventis SA has extended its offer to buy Cambridge-based biotech giant Genzyme Corp. for $18.5 billion, or $69 per share.
The offer was originally set to expire Jan. 21, but it will now be in effect until Feb. 15.
When Sanofi initiated the original offer in October, Genzyme immediately dismissed it as too low. The two companies remain in negotiation over the possible sale.
Genzyme has much of its operations in Central Massachusetts.
