The U.S. Food and Drug Administration has approved Teva Pharmaceutical Industries Ltd.’s application to market a drug that boosts the production of infection-fighting white blood cells in certain cancer patients undergoing chemotherapy, the Israeli drug maker said Thursday.

The Tel Aviv company’s drug is a direct competitor to Amgen Inc.’s second oldest drug, Neupogen, which faces expiration of its main U.S. patents next year. To settle a patent infringement lawsuit by the Thousand Oaks biotech giant, Teva last year agree to delay launching its drug in the United States until November 2013.

The introduction of the Teva drug is not expected to have a significant impact on total Amgen sales, which reached nearly $15.6 billion last year. A new version of Neupogen called Neulasta, which has stronger patent protection, now accounts for 80 percent of sales in that product group. Combined Neulasta and Neupogen sales last year rose 8 percent to $5.2 billion.

Amgen shares closed down 57 cents, or less than 1 percent, to $83.15 on the Nasdaq. Teva shares closed down 64 cents, or 1.5 percent, to $39.56 on the New York Stock Exchange.

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