America's Impax Laboratories has begun the challenging process against the suit filed by two companies for patent infringement over a generic version of Opana® ER (oxymorphone hydrochloride extended-release) drug.
Impax Laboratories and its subsidiary ThoRx Laboratories have been challenged by US-based Endo Pharmaceuticals and German's Grunenthal on 14 November 2012, regarding the patents of Opana® ER tablets, 5 mg, 7.5 mg, 10 mg, 15 mg, 20 mg, 30 mg, and 40 mg, listed in the Orange Book.
The drug is expected to help patients, who need around-the-clock opioid treatment for longer periods, by way of relieving them from moderate to severe pain, according to Impax.
The company also said that ThoRX has informed the New Drug Application holder and patent owner of paragraph IV certification, which forms part of Abbreviated New Drug Application (ANDA) submitted to USFDA recently.
Upon securing ANDA approval, the company plans to commercialize the drug through Global Pharmaceuticals division, which markets the generic products of Impax.
Opana ER posted US sales of about $90m for the quarter ending September 2012, as per Wolters Kluwer Health's report, said the company.