Merck & Co, Inc announced that the US District Court for the District of Delaware ruled against the company in a patent infringement suit against Teva Pharmaceuticals USA Inc.

"We are very disappointed with the court's ruling, and we continue to believe the patent for Temodar in the US is valid and enforceable," said Bruce N Kuhlik, executive vice president and general counsel at Merck. "Today's decision reflects a step in the lengthy patent litigation process, and we plan to appeal this decision."

Teva is seeking US FDA approval to sell a generic version of the 5, 20, 100, 140, 180 and 250 mg capsules of Temodar (temozolomide), a chemotherapeutic agent approved for the treatment of adult patients with newly diagnosed glioblastoma multiforme and for refractory anaplastic astrocytoma, two forms of brain cancer.

In her decision, Judge Sue L Robinson ruled that Merck's patent on Temodar was unenforceable due to prosecution latches and/or inequitable conduct.