The US based Sepracor Inc, jointly with University of Massachusetts, has moved patent infringement litigation against the Mumbai based Glenmark Pharmaceuticals, alleging violation of two patents covering the anti-allergic drug Clarinex, for which the generic drug is desloratidine.

The litigation is in response to the Glenmark's Abbreviated New Drug Application (ANDA) filing with the US FDA for approval to commercially market the bioequivalent version of the drug. The product currently has sales of USD 325 million per annum in the US market.

In the compliant, filed in the District Court of New Jersey, the company alleges infringement of the US patents 7,214,683 (the '683 patent) covering the oral pharmaceutical composition of desloratidine and 7,214,684 (the '684 patent) related to the method of treating allergic rhinitis.

Interestingly, Glenmark is already facing a patent infringement case on desloratadine from Schering-Plough Corporation. In a move to block the generic presence of the drug, Schering-Plough has sued a number of Indian drug companies, including Glenmark, Sun Pharmaceutical Industries Ltd., Dr Reddy's Laboratories Ltd, Ranbaxy Laboratories Ltd, Lupin Ltd and Orchid Chemicals and Pharmaceuticals Ltd in September 2006. The complaint was to protect the drug, from the ANDA filings of these companies, under US patents 6,100,274 (the '274 patent) and US 6,979,463 (the '463 patent).

Sepracor has issued exclusive worldwide rights on its patents relating to desloratidine to Schering Plough Corp. in December 1997. Sepracor earns royalties on sales of Clarinex in the US and other countries where the company hold patents relating to desloratidine. According to sources, the earliest that a generic version of Clarinex could be introduced is on 2020, as the drug is protected by various patents up to the period.

Glenmark spokesperson responded to Pharmabiz, This case is related to the Desloratidine filing. However, as the matter is sub-judice, we will not be able to comment on this."

Clarinex, which first received FDA approval in December 2001, is the successor to the allergy pill Claritin. The global sales of Clarinex were USD 386 million in the first six months of 2006, and the growth rate seems equal at present, according to market sources.