The US-based Genzyme Corporation has filed a patent infringement suit against the Mumbai-based Lupin Ltd and its US subsidiary against the latters' Abbreviated New Drug Application (ANDA) filing for manufacturing and marketing of generic version of Genzyme's Renvela (sevelamer carbonate) used for the control of serum phosphorus in chronic kidney patients on dialysis.

In a petition filed in the District Court of Maryland, US, on May 14, 2009, Genzyme alleges that by attempting to manufacture and market the generic form of the product, Lupin has tried to infringe six patent claims of the company. Genzyme holds US Patent Nos. 5,496,545 (`545), 5,667,775 (`775), 7,014,846 (`846) and 7,459,151 (`151) for phosphate-binding polymers for oral administration issued on 1996, 1997, 2006 and 2008 respectively. Another two patents, Patent Nos 6,509,013 (`013) and 6,858,203 (`203), for the method of making phosphate-binding polymers for oral administration issued on 2003 and 2009 respectively, were also questioned by Lupin.

Renvela, a non-calcium, non-metal, non-absorbed phosphate binder available in 800 mg, has been developed by Genzyme as a next generation phosphate binder to replace its sevelamer hydrochloride product Renagel, claimed to be the most-prescribed phosphate binder in the United States.

The company is currently working on a transition programme to switch patients using Renagel to Renvela, as the new product has shown free from some of the side effects found with Renagel. The transition is expected to complete by September 30, 2009, according to Genzyme announcements.

The company claims that the added benefit of a carbonate buffer in Renvela, when compared to Renagel, will improve the serum bicarbonate levels, improve overall gastrointestinal (GI) tolerability and also offers the company the ability to develop a new formulation in powder form. The product is also a stepping stone for the company to expand into third and fourth stages of chronic kidney disease. Both the products are protected by the same core patents, which will expire in 2014, as per the reports.

The products, Renvela and Renagel have produced revenue of USD 678 million for Genzyme in last financial year and the company expects that the products would produce revenues if USD 725 to 735 million in 2009. Anticipated key drivers include EU approval of Renvela and the expansion of the product's US indication to include the treatment of patients with chronic kidney disease who are not on dialysis, both of which are expected in mid-2009.

Sevelamer is contraindicated in patients with hypophosphatemia or bowel obstruction and the company alerts that caution should be exercised in patients with dysphagia, swallowing disorders, severe gastrointestinal (GI) motility disorders including severe constipation or major GI tract surgery. Common adverse events reported with sevelamer include vomiting, nausea, diarrhoea, dyspepsia, abdominal pain, and constipation.

Lupin has recently entered into a patent settlement agreement with Wyeth Ltd over the latter's USD 1.8 billion antidepressant drug Effexor XR, agreeing that it will be licensed to launch a generic version of the drug in US after June 1, 2011, or earlier under certain circumstances.