US drug giant Pfizer is taking a stand against a decision by the Court of Appeal of The Hague in the Netherlands which ruled that its enantiomer patent for the world’s number one selling drug Lipitor is invalid.

The group is locked in an ongoing global battle with Indian generics maker Ranbaxy over the intellectual property surrounding Lipitor (atorvastatin), but stressed that the latter’s victory with this particular patent (EP 409,281), which expires in July 2010, actually has no commercial impact because the basic patent protect the drug remains in tact until November 2011.

Just last week the same court concluded that the basic patent would be infringed by Ranbaxy’s proposed generic atorvastatin product, thereby preventing its launch until the patent expires in 2011.

Pfizer is certainly having to work hard to protect its super-blockbuster. Last month, a court in Canada ruled in favour of generic drugmaker Apotex by turning down Pfizer’s bid to stop the launch of its generic version of Lipitor before the expiry of the same enantiomer patent in July 2010.

But the New York-based drug giant has also racked up a fair few successes under its belt, the most recent being the Court of Appeal of Barcelona upholding the patent in Spain last autumn, and the group has vowed to continue to vigorously defend its intellectual property.