In the lawsuit, filed on Nov. 28, Bayer said that Lupin is preparing to bring a copy of the Natazia pill, also called Qlaira, to U.S. markets even though Bayer's U.S. patent on the pill runs through 2026.

The complaint said Bayer would be entitled to an award of damages and treble damages for any commercial sales of the generic product.

Lupin declined to comment on the lawsuit. "We do not comment on on-going litigations as a matter of policy," said Lupin spokesperson Shamsher Gorawara.

Natazia is approved in the U.S. as a contraceptive and for the treatment of heavy menstrual bleeding.

Birth-control is one of the most important businesses for Bayer's pharmaceuticals arm, with contraceptive sales of 1.1 billion euros in 2011.

Bayer Pharma AG v Lupin Ltd. and Lupin Pharmaceuticals Inc. (Case 1:12-cv-01592-UNA) was filed with the U.S. District Court, District of Delaware.

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