At least four Indian gen­eric drug-makers – Lupin, Sun Pharma, Ranbaxy and Wockhardt —

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were hit with a flurry of US patent infringement suits by different foreign companies in the past 10 days as these companies had expressed a desire to market generic copies of branded drugs ahead of th­eir patent expiry dates, court filings show.

On February 17 and 18, Bayer Schering Pharma AG filed two similar patent in­fringement suits against Lu­pin following a Paragraph IV certification as part of Lup­in’s filing of a generic drug application. This generic dr­ug application is necessary for Lupin to manufacture a generic version of Bayer’s Cipro Oral Suspen­sion (cip­rofloxacin, used to treat in­fections). In the last 12 mo­nths, Bayer AG has recorded around $ 430 million in Ci­pro global sales. Lupin does not comment on patent litigations.

If a generic company is the first to file its Abbreviated New Drug Application (ANDA) with a Paragraph IV certification and prevails in the subsequent lawsuit, that generic company is granted a period of market exclusivity of 180 days. "The 180-day exclusivity incentive can be significant for a generic firm as it would be the only generic version on the market," said a senior pharma analyst with a foreign brokerage.

Daiichi-Sankyo owned Ranbaxy faced a patent suit from Medicis Pharmaceutical Corp. which alleged in its filing in Delaware on February 16 that its patent for "Method for the Treatment of Acne" was infringed following a Paragraph IV certification as part of Ranbaxy's filing of a generic drug ap­plication to manufacture a ge­neric version of Medics' So­lodyn (minocycline hydr­ochloride extended release tablets, used to treat acne).

Skin care medicines including Solodyn, accounted for $ 325 million of Medicis’ sales last year and it has already settled with Teva, Sandoz, Glenmark and Impax for Solodyn while it remains in litigation with Lupin.

A Ranbaxy US spokesperson did not return calls seeking comment.

Alcon Research sued Wockhardt in the Southern District of Indiana on February 12 wherein Alcon said that Wockhardt's Paragraph IV certification in its generic drug application of Patanol infringes on Alcon's patent. Alcon is also fighting with other generic companies such as Apotex, Barr and Sandox on its $ 200 million-a-year brand Patanol, whose earliest patent expires in June 2011.

On February 12 and 16, Abbott Laboratories filed two similar patent infringement suits against Sun Pharmaceutical Industries following a Paragraph IV certification as part of Sun's filing of a generic drug application to make a generic version of Abbott's Niaspan (niacin extended-release tablets.