Forest Laboratories has won a lawsuit aiming to keep a generic version of its best-selling antidepressant product Lexapro off the US market.

Teva Pharmaceutical Industries failed in a bid to overturn the patent protection for Lexapro (escitalopram oxalate), the last barrier to launching its generic which was approved by the US Food and Drug Administration in May.

This is a crucial victory for Forest, as Lexapro brought in sales of $464 million in the first quarter of this year and is its biggest product, accounting for more than half its total sales. And it is also good news for Danish drugmaker H Lundbeck, which sells the antidepressant in Europe as Cipralex and supplies the bulk active ingredient to Forest.

The ruling in the US District Court of Delaware means that Forest can still claim patent protection for Lexapro out to March 2012.

Teva still has leave to appeal the ruling, and could launch its copycat product in the interim as it has full approval, although in this case it would lay itself open to substantial damages if the appeal failed.

Earlier this month, Forest and Lundbeck filed a patent infringement lawsuit against Caraco Pharmaceutical Laboratories after they received notice that the latter had submitted a Lexapro clone for approval with the FDA. It has previously settled a lawsuit with Alphapharm by agreeing to make the company an exclusive distributor of generic escitalopram.

News of the verdict came too late yesterday to have an effect on Forest’s share price, which closed down fractionally to $38.40, although after-hours trading indicated that the stock should be in the ascendency today.

- Meanwhile, Teva said that the FDA has tentatively approved its Abbreviated New Drug Application in relation to the marketing of a generic version of Novartis' hypertension treatment Lotrel (amlodipine besylate and benazepril HCL).

The company added that it is still involved in a patent litigation suit in the US District Court in New Jersey, which was filed against it in 2004. A trial date has not yet been set.