Dr Reddy's Laboratories today said Aventis Pharmaceuticals inc had filed a lawsuit against it alleging patent infringement on six Orange Book patents.

This follows Dr Reddy's filing an abbreviated new drug application with the US Food and Drug Administration for Fexofenadine HCl Tablets, equivalent to 30 mg, 60 mg and 180 mg of base, with Paragraph IV certifications on all the seven Orange Book patents listed for Allegra tablets.

Allegra is the branded version of Aventis' patented drug Fexofenadine HCl. The product is indicated for the relief of symptoms associated with seasonal allergic rhinitis. The brand has annual sales of approximately $1.35 billion in the US as per IMS 2002 report.

Dr Reddy's said it notified Aventis on the ANDA filing and the latter filed a lawsuit against the company in the United States District Court of New Jersey.

With the filing of the ANDA for Fexofenadine HCl Tablets, the total number of ANDA filings of Dr Reddy's with the US FDA increased to 31. Of these, 18 are Para IV filings that involve patent challenges and 14 address a total market value of $12.7 billion.