The US Food and Drug Administration has
approved Amgen’s pegfilgrastim (Neulasta) for use in decreasing the incidence
of infection, as manifested by febrile neutropenia. The agent, administered in a
single fixed dose per chemotherapy cycle, is indicated for patients with
nonmyeloid malignancies who are receiving myelosuppressive chemotherapy
associated with a significant incidence of febrile neutropenia.
Nearly 50% of cancer chemotherapy patients develop severe
neutropenia, and, on average, less than 10% receive proactive protection from
neutropenia. Studies have shown that 30% to 40% of patients who receive certain
types of chemotherapy and are not given a white blood cell booster will
experience neutropenia with fever.
Less Frequent Dosing
Until now, granulocyte colony-stimulating factor (G-CSF,
filgrastim, [Neupogen]) was the only agent shown to decrease the risk of
infection and hospitalization as a result of chemotherapy-induced neutropenia.
However, the burden of frequent daily dosing (for as many as 14 consecutive
days) led many health-care professionals to delay intervention with filgrastim
until after a neutropenic infection developed.
"The less frequent dosing of Neulasta means that
patients will require fewer painful injections, fewer office visits for those
injections, and fewer disruptions to their lives at a time when they are
overwhelmed with a serious disease," said Frankie Ann Holmes, md, a lead
clinical trial investigator and associate director of research at US Oncology in
Houston. "This approval means that hundreds of thousands of chemotherapy
patients at risk for infection may now receive Neulasta as protection at the
onset of each treatment cycle before complications arise."
Proven in Clinical Trials
Data from two pivotal phase III studies in breast cancer
patients (310 receiving a 100-µg/kg dose, 157 receiving a fixed 6-mg dose)
demonstrated that a single dose of pegfilgrastim provided protection from
infection comparable to a mean of 11 daily injections of standard G-CSF (5
µg/kg/d). The randomized, double-blind trials were conducted in breast cancer
patients undergoing as many as four cycles of chemotherapy with doxorubicin and
Days of severe neutropenia were comparable between treatment
groups in all cycles. The mean duration of severe neutropenia in cycle 1
appeared to be equivalent for patients in the pegfilgrastim and filgrastim
groups: an average of 1.8 vs 1.6 days, respectively, in the fixed-dose trial,
and 1.7 vs 1.6 days in the by-weight dosing trial. The average weight of
patients was 160 lb (72.4 kg), with more than 76% weighing 154 lb (70 kg)
or more. Pegfilgrastim was comparable to filgrastim with respect to rates of
febrile neutropenia across all chemotherapy cycles in both studies.
Data from phase II studies in patients with various
malignancies receiving a variety of chemotherapy regimens further supported the
safety and efficacy of pegfilgrastim. These studies in patients with breast
cancer, thoracic tumors (including lung cancer), non-Hodgkin’s lymphoma, and
Hodgkin’s disease demonstrated that the efficacy of a single injection of
pegfilgrastim (100 µg/kg) was similar to that of daily injections of
filgrastim (5 µg/kg/d).
Pegfilgrastim was found to be safe and well-tolerated. In clinical trials,
the most common adverse event following combination chemotherapy in 465 patients
with lymphoma and solid tumors was bone pain, which was reported in 26% of
patients. In most cases, the bone pain was controlled with nonnarcotic
analgesics. The most serious adverse event was low oxygen in the blood, reported
in one patient. In addition, although not reported in patients receiving
pegfilgrastim, rare events of respiratory distress syndrome, splenic rupture,
and sickle cell crisis occurred in patients receiving the parent compound,