Teva Pharmaceutical Industries said it will bring a generic version of Viagra® (sildenafil citrate) to market two years sooner than previously planned, after the Israeli drug giant’s U.S. subsidiary and Pfizer agreed to resolve a longtime patent lawsuit over the male sexual dysfunction drug.

The companies have entered into a settlement of the litigation that will allow Teva to launch its generic Viagra on December 11, 2017 or “earlier under certain circumstances,” which were undisclosed in a company statement. Teva is among drugmakers that have been selling generic Viagra in parts of Europe since June.

As part of the deal, Teva agreed to pay Pfizer an undisclosed sum in royalties through the expiration of Pfizer’s patent for Viagra in April 2020, Pfizer said in a separate statement.

Other terms of the settlement agreement are confidential.

The patent, issued in 2002 for the drug’s method of action in treating impotence, was at the center of a lawsuit that met with partial success in 2010, when federal courts invalidated portions of the patent because of the drug’s similarity to horny goat weed, a Chinese herb.

A year later, however, Pfizer won a key victory when a U.S. District Court judge in Norfolk, VA, upheld the method patent, extending protection that was once expected to end in 2012 when the drug’s composition of matter patent expired.

Teva sought to invalidate the remainder of the patent, but yesterday lost its appeal in the U.S. Court of Appeals for the Federal Circuit.

The patent was extended six months after Pfizer tested the drug in young patients.

Despite the litigation, Teva has already won the FDA’s tentative approval for 25 mg, 50 mg, and 100 mg dosages of generic Viagra tablets.

Teva cited IMS sales data showing Viagra with annual sales of about $1.2 billion in the United States as of September 2013. According to Pfizer, Viagra generated $2.051 billion in global sales last year, up 3.5% from 2011.

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