A unit of Johnson & Johnson that is a rival to and customer of Amgen Inc. is seeking to be added as a co-plaintiff in Amgen's patent infringement lawsuit against drugmaker Roche Holding AG concerning anemia drugs that both U.S. companies market.

Thousand Oaks-based Amgen sued Roche in November in an effort to prevent the Swiss drugmaker from introducing its anemia drug Cera into the U.S. market. Cera would compete with Amgen's Epogen and Aranesp. Johnson & Johnson's Ortho Biotech Products L.P. sells a version of Epogen called Procrit under a 1985 licensing agreement with Amgen.

Ortho and Amgen have a complex commercial relationship and a lengthy history of disputes over Procrit. Attorneys for New Brunswick, N.J.- based Johnson & Johnson say the company is seeking to intervene in the suit because despite its status as an exclusive licensee, the company can't depend on Amgen to represent its interests.

"Ortho has ample reason for concern that its interests in this proceeding are not being fully protected by Amgen,'' the company said in documents filed last week in U.S. District Court in Boston, noting that Amgen did not inform it in advance of filing the suit and later rejected its request to be included as a co-plaintiff.

Amgen spokesman Dan Whelan confirmed his company had turned down Ortho's request to be included in the suit, and was preparing a response to latest request. "Amgen has great confidence in its intellectual property portfolio and proven ability to protect its products from infringers," Whelan said.

Roche plans to seek U.S. regulatory approval this year to sell Cera in the United States as a treatment for kidney-disease-related anemia, and seek additional approval for chemotherapy-related anemia in 2009. Aranesp, a second-generation Epogen, competes with Procrit in the chemotherapy market. Both Epogen and Aranesp are sold in the kidney disease market.

Aranesp and Epogen had $4.5 billion in combined U.S. sales in 2005, while estimated Procrit sales were $3.3 billion.

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