A US court has once again ruled in favour of Lilly in the long-running legal battle with Teva over generic Alimta.

Teva has been looking to make a copycat version of the blockbuster lung cancer drug, and has taken Lilly to court to try and disprove the validity of its patents.

In 2012 the courts upheld the patent for Alimta’s (pemetrexed) chemical make-up. Teva then sought to challenge a method-of-use patent that covers the co-administration of Alimta with two nutrients – folic acid and vitamin B12 – that protect against the side effects of the drug.

Teva argued that this use of nutrients is obvious and does not warrant any additional intellectual property. But in an initial court ruling last year, the judge said that at the time of Alimta’s development skilled scientists would not necessarily have expected the combination to work in this way.

"We are pleased with today's ruling on Alimta finding the vitamin regimen patent would be infringed," says Michael Harrington, senior vice president and general counsel for Lilly. "The significant scientific research that Lilly performed in support of the vitamin regimen patent deserves intellectual property protection.”

The new court ruling provides intellectual property protection for the drug until May 2022. This should technically provide Lilly market exclusivity until then, even though the compound patent expires in 2017.

This will be relief for Lilly as Alimta is one of its few strong-selling products that have not been hit by generic competition in recent years. The medicine made $2.7 billion in sales last year.

In a statement Teva says: “We are disappointed with the district court’s decision and we are evaluating our options to appeal.”