Magazine article Drug Topics

New G-CSF Product Treats Neutropenia Following Chemo

Magazine article Drug Topics

New G-CSF Product Treats Neutropenia Following Chemo

Article excerpt



In late January, the Food & Drug Administration approved Neulasta (pegfilgrastim, Amgen), a longacting form of Neupogen (filgrastim, Amgen), for decreasing the incidence of infection, as manifested by febrile neutropenia, in patients with nonmyeloid malignancies receiving myelosuppressive chemotherapy.

As its name suggests, pegfilgrastim is essentially filgrastim, or recombinant human granulocyte-- colony stimulating factor (G-CSF), with a large polyethylene glycol (PEG) molecule covalently bound to it. Since the PEG tail is too large to fit through kidney pores, said Frankie Ann Holmes, M.D., associate director of breast cancer research at US Oncology in Houston, "the only way for this molecule to be cleared is by going to the site where it is most needed," the white blood cell.

As a self-regulating drug, whose blood concentrations fall as the neutrophil count rebounds, pegfilgrastim needs to be administered only once in each chemotherapy cycle. Filgrastim must be administered daily for up to 14 days, until absolute neutrophil count (ANC) reaches 10,000/mm^sup 3^.

In double-blind clinical trials, pegfilgrastim was compared with filgrastim in patients with breast cancer, lung cancer, and lymphoma. Duration of severe neutropenia was shown to be equal, within a few hours, for both treatment groups. In studies in which Holmes was involved, patients in both groups required an average of 11 days of injections (filgrastim or placebo), with daily blood counts, until target ANC was achieved. While for patients on filgrastim, the counts rose and fell following each injection, ANC in pegfilgrastim-treated patients rose smoothly and "just coasted right in" without overshooting, she reported. In fact, the incidence of neutropenic infections was 50% lower in the pegfilgrastim arm, at 9% as compared with 18% in the filgrastim group.

Pegfilgrastim's once-per-cycle dosing offers several advantages, including "fewer office visits, less time missed from work and family, and fewer reminders of the disease," said George Jaresko, Pharm.D., assistant professor, department of pharmacy, University of Southern California in Los Angeles.

About half of the patients taking filgrastim inject themselves, said Jaresko, an infectious disease pharmacist who has served as a consultant to Amgen on filgrastim; the rest of the patients have someone else administer the drug or go to a physician's office or an infusion center. Holmes noted that going to a clinic might be the only option for patients insured by Medicare, which covers only injectable drugs administered by healthcare professionals. …

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