Drug major Wockhardt has challenged the US patent of Stalevo, a new generation combination drug for the treatment of Parkinson's disease, originated by Finland-based Orion Corporation and marketed by Novartis [Get Quote].

Wockhardt has filed an abbreviated new drug-marketing application (ANDA) with the US Food and Drug Administration (FDA), seeking authorisation to produce and market a generic version of Stalevo in 12.5, 200 and 50 mg strengths, said Orion Corporation.

Approximately 6.5 million people worldwide suffer from Parkinson's disease, a disabling neurological condition. Stalevo simplifies the treatment process by combining levodopa, the most widely-used agent for treating Parkinson's disease, with enzyme inhibitors carbidopa and entacapone.

"Orion, together with Novartis, is currently evaluating legal options to protect its rights, and at this point. The ANDA review process is just beginning and the realisation of generic competition is neither certain, nor imminent," the company said.

When reached for comments, Wockhardt chose not to make any.

In early January this year, another Indian drug major, Sun Pharmaceutical Industries [Get Quote], had challenged three patents of Stalevo. The latest of Stalevo's six US patents are to expire by October 31, 2010. The drug was given marketing permission by the FDA in June 2003.

Orion had previously sued Wockhardt for challenging the patents on Comtan (entacapone), another version of Parkinson's disease drug marketed by Novartis. Wockhardt is believed to be the first to challenge the patent on this drug, which will give the company a six-month exclusivity to sell the drug on patent expiry.

The case is pending in the Delaware district court, US, and may come up for hearing in November 2009. Sun Pharma also had challenged the patent on Comtan's 200 mg version.

Wockhardt's challenges are for Orion's four US patents (numbers 5,135,950; 5,446,194; 6,500,867 and 6,797,732) listed in the Orange Book, the FDA's official listing of approved drug products.

As per US laws on generic drug sales, a patent owner has to sue a generic challenger within 45 days to force a 30-month stay on the final FDA approval for the application. During that time, the FDA can give only a tentative approval to the ANDA applicant unless the applicant obtains a favourable decision on all challenged patents in the lawsuit.