Filgrastim

Filgrastim

Chemical structure of Filgrastim.

Filgrastim is a therapeutic drug primarily used to combat neutropenia, a condition characterized by an abnormally low count of neutrophils, a type of white blood cell crucial for fighting infections. Marketed under various brand names such as Neupogen, Zarxio, and Granix, Filgrastim stimulates the bone marrow to produce more white blood cells. It belongs to the class of drugs known as colony-stimulating factors, specifically granulocyte colony-stimulating factor (G-CSF).

Overview

Filgrastim's primary role is to promote the production and maturation of white blood cells in the bone marrow, thereby strengthening the immune system and aiding the body in fighting infections, especially in patients undergoing certain types of chemotherapy.

Brand Names and Uses

• Neupogen and Zarxio: Used both to treat neutropenia resulting from chemotherapy and to prevent infections in patients diagnosed with specific cancer types.
• Granix: Primarily employed for treating chemotherapy-induced neutropenia.
• All three brands of Filgrastim are also used for the treatment of severe chronic neutropenia and to prime the blood for the collection of particular blood cell types.

Mechanism of Action

Filgrastim functions as a granulocyte colony-stimulating factor (G-CSF), effectively aiding the bone marrow in the accelerated production and maturation of granulocytes, a category of white blood cells. This increase in white blood cells enhances the body's ability to combat infections and recover faster from certain treatments that might reduce white blood cell counts, such as chemotherapy.

Side Effects

Like all drugs, Filgrastim can have side effects. Common side effects include:

• Bone pain
• Muscle aches
• Headache
• Fatigue

It's crucial to consult with a healthcare professional about potential risks and benefits before commencing Filgrastim treatment.

Considerations for Patients

Patients considering Filgrastim treatment should discuss the following with their doctor:

• The potential risk of spleen enlargement or rupture.
• Any history of allergic reactions to medications.
• Other medications or treatments currently being used.
• Any existing lung or breathing problems.

Filgrastim (fil gra' stim) is a recombinant, non-glycosylated form of the 175 amino acid protein, granulocyte colony stimulating factor (G-CSF) that induces the proliferation and maturation of neutrophils.  G-CSF is normally produced by multiple cell types including monocytes, fibroblasts, macrophages and stromal cells.  It acts on specific receptors found on granulocyte progenitors and causes an increase in circulating neutrophils.  Recombinant filgrastim has been shown to increase total neutrophil counts and to protect, in part, against severe infections in patients with neutropenia for various causes.

FDA approval information for Filgrastim

Filgrastim was approved for use in the United States in 1991, and current indications are for chemotherapy induced neutropenia, in hematopoietic cell transplantation after myeloablation and in congenital and cyclic neutropenias.  Filgrastim is also used in patients undergoing autologous peripheral blood progenitor (stem) cell collection.  Filgrastim is available as a solution in single use vials or prefilled syringes (300 and 600 mcg each) for subcutaneous or intravenous administration under the brand name Neupogen. 

Dosage and administration for Filgrastim

Dose regimens vary by indication (5 or 10 mcg/kg per day) and route of administration (intravenous or subcutaneous).

Pegylated longacting form - pegfilgrastim

A pegylated, long acting form of G-CSF (pegfilgrastim) became available in 2002 under the brand name Neulasta which can be given once weekly and has similar efficacy and safety as filgrastim.  The current formal indications for pegfilgrastim are limited to prevention of febrile neutropenia during myelosuppressive cancer chemotherapy for non-myeloid malignancies.  Pegfilgrastim is available in solution of 6 mg/0.6 mL in prefilled syringes.  The typical dose is 6 mg subcutaneously once per chemotherapy cycle.  Common side effects of filgrastim and pegfilgrastim include fever, musculoskeletal pain, rash, cough and shortness of breath.  Rare side effects include acute allergic reactions, splenic rupture and acute respiratory distress syndrome.

Sargramostim

Sargramostim (sar gra' moe stim) is a recombinant form of granulocyte-macrophage stimulating factor (GM-CSF) that stimulates the proliferation and maturation of neutrophils and macrophages.  Sargramostim is prepared in yeast (S. cerevisae) and is a 127 amino acid glycoprotein that is 98% identical to native, human GM-CSF.  Sargramostim increases the number and activity of circulating neutrophils and monocytes.  Sargramostim was approved in the United States in 1991 for use in patients with acute myelogenous leukemia after chemotherapy induced neutropenia.  Current indications also include support of patients undergoing hematopoietic cell transplantation as well as for patients undergoing autologous peripheral blood progenitor (stem) cell collection.  Sargramostim is available in liquid and lyophilized forms under the brand names Leukine and Prokine.  Sargramostim is given either intravenously or subcutaneously daily or three times weekly, the dose and regimen varying by indication.  Common side effects include fever, headache, fatigue, bone pain, nausea and weakness, but similar rates of these symptoms are reported with placebo or comparator therapies.

Conclusion

Filgrastim stands as a vital tool in oncology and hematology, offering patients an enhanced ability to combat infections and endure intensive treatments, such as chemotherapy. It's crucial to understand its uses, benefits, and potential risks.

See Also

• Neutropenia
• Chemotherapy
• White Blood Cells

References

• Clinical Overview of Filgrastim. National Cancer Institute.
• Filgrastim Treatment Protocols. American Society of Clinical Oncology.

Hematologic Agents Eculizumab, Emapalumab, Emicizumab, Lanadelumab, Ravulizumab

Hematologic Growth Factors

• Granulocyte colony stimulating factors
  • Filgrastim, Pegfilgrastim

• Granulocyte-Macrophage Colony Stimulating Factors
  • Sargramostim

• Erythropoiesis stimulating agents
  • Epoetin, Darbepoetin, Peginesatide

Thrombopoietin receptor agonists and Thrombopoiesis Stimulators

• • Avatrombopag, Eltrombopag, Fostamatinib, Lusutrombopag, Romiplostim, Oprelvekin (IL-11)

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