The “-grastim” drug stem name
Medications that end with the suffix “-grastim” belong to a class of medications known as granulocyte colony-stimulating factors (G-CSF). This class of medications belongs to a larger drug class of CSFs with the stem suffix “-stim.” This article focuses only on “-grastim” stem name drugs.
G-CSFs are drugs that are used to stimulate hematopoietic cells in the bone marrow to produce more neutrophils (white blood cells). G-CSFs bind to specific cell surface receptors to trigger signaling pathways that stimulate proliferation, differentiation, commitment, and end-cell function activation. This leads to increased production and activity of neutrophils within the bone marrow.
Currently, there are four single-agent G-CSFs approved for use in the United States (Table 1). G-CSFs mainstay of treatment is prevention of severe neutropenia. They are typically given following a neutropenic event or the administration of cytotoxic chemotherapy. These agents are used to shorten the period of severe neutropenia and reduce the risk of bacterial and fungal infections. Filgrastim was the first approved medication in this drug class in 1991. In addition, it is also approved for recovery following hematopoietic stem cell transplant and severe chronic neutropenia (congenital, idiopathic, or cyclic). Pegfilgrastim has also been shown to increase survival in patients who experience Hematopoietic Syndrome of Acute Radiation Syndrome (H-ARS), which denotes stem cell injury following radiation exposure.
Table 1. List of G-CSFs available in the United States.
All four drugs are available in prefilled syringes for subcutaneous administration. Some brands of pegfilgrastim (Neulasta Onpro, Udenyca Onbody) are available as an on-body injector, which is a pod filled with the drug that is applied to the patient’s skin by a healthcare provider to administer the dose over a specific duration (5 minutes for Udenyca or 45 minutes for Neulasta). Udenyca is the only agent available as an autoinjector pen. Filgrastim is also available in a formulation that may be given as a short infusion over 15 to 30 minutes or a continuous infusion with a maximum duration of 24 hours to allow the body time to metabolize the cytotoxic drugs before stimulating new neutrophil production.
Filgrastim is typically dosed once daily, and dose adjustments vary depending upon duration and severity of neutropenia with a goal to obtain a specific absolute neutrophil count (ANC). Pegfilgrastim, eflapegrastim, and efbemalenograstim alfa are given once per chemotherapy cycle. When used to treat H-ARS, pegfilgrastim is given once a week for two doses. Due to potential cell sensitivity, G-CSFs should not be given earlier than 24 hours following cytotoxic chemotherapy.
Common side effects include fatigue; gastrointestinal upset; and bone, back, or limb pain. Serious adverse reactions may include splenic rupture, acute respiratory distress syndrome, sickle cell crisis, glomerulonephritis, capillary leak syndrome, leukocytosis, thrombocytopenia, myelodysplastic syndrome, acute myeloid leukemia, and aortitis. Filgrastim also has a risk of cutaneous vasculitis (purple spots or redness on the skin). Patients should inform their healthcare provider of any signs or symptoms of a serious adverse reaction. G-CSFs are contraindicated in patients with a history of serious allergic reactions to filgrastim products. Patients should be given appropriate instructions for use and counseled on injection technique depending upon the prescribed dosage form.
