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A bone marrow stimulus
Amgen markets Neupogen® for the treatment of chemotherapy-induced neutropenia. Neutropenia refers to a neutrophil deficiency. Neutrophils are the most abundant type of white blood cell, usually found in the bloodstream. They act in the immune system as early detectors of infection and are responsible for the first signs of inflammation. They are phagocytes – they attack and consume antigenic particles or microorganisms.
Neutropenia, the relative lack of these cells, results commonly from chemotherapy or bone marrow transplantation. Neupogen® ameliorates the condition by stimulating the production of neutrophils in bone marrow. It is a recombinant protein, a granulocyte colony-stimulating factor called filgrastim. It is manufactured in E. coli cells, and is identical to the natural protein except that its amino acid sequence contains an additional methionine residue (which is necessary for bacterial expression), and is non-glycosylated (because bacterial cells lack mammalian glycosylation machinery).
Initially, the FDA approves the drug for chemotherapy patients. A secondary approval in 1996 authorizes its use in bone marrow transplant cases. By 1993, Amgen owns 90% of the U.S. market for white blood cell stimulators, and Neupogen® accounts for 52% of Amgen’s sales revenues. With its second blockbuster drug in three years, the company secures it place in the biotech firmament. Amgen eventually surpasses Genentech as the world’s largest and most successful biotechnology company.