Filgrastim
Recombinant G-CSF that stimulates neutrophil production and mobilization for chemotherapy-induced neutropenia and stem cell collection.
Chemical Identity
| Property | Value |
|---|---|
| Molecular Weight | ~18.8 kDa |
| Amino Acids | 174 (mature protein) |
| CAS Number | 121181-53-1 |
| Gene | CSF3 (G-CSF) |
| Route | SC, IV |
Structure
Filgrastim (Neupogen) is recombinant human granulocyte colony-stimulating factor (G-CSF) produced in E. coli. It differs from endogenous G-CSF by having an N-terminal methionine and no glycosylation. Despite lacking glycosylation, it retains full biological activity.
Mechanism of Action
G-CSF binds G-CSF receptors on neutrophil precursors, activating JAK/STAT, Ras/MAPK, and PI3K pathways. This stimulates proliferation, differentiation, and survival of neutrophil progenitors, shortens neutrophil maturation time, and enhances neutrophil function (phagocytosis, ADCC, migration).
Clinical Applications
- Chemotherapy-induced neutropenia: Reduction of febrile neutropenia
- Chronic neutropenia: Severe congenital and cyclic neutropenia
- Stem cell mobilization: Peripheral blood stem cell collection
- Bone marrow transplant: Engraftment acceleration
- Acute radiation syndrome: Hematopoietic recovery
Pharmacokinetics
- Half-life: 3.5 hours (IV), 4-6 hours (SC)
- Tmax: 2-6 hours (SC)
- Bioavailability: 60-70% (SC)
- Onset: ANC increase within 24 hours
- Route: SC (preferred), IV
Safety and Side Effects
Bone pain (20-30%), splenomegaly, headache, fatigue, and rare splenic rupture. Sickle cell crisis in patients with sickle cell disease. WBC counts >100,000 seen occasionally.
References
- Crawford, J., et al. (1991). Filgrastim for chemotherapy-induced neutropenia. New England Journal of Medicine, 325, 164-170.
- Welte, K., et al. (1996). Filgrastim for severe chronic neutropenia. New England Journal of Medicine, 329, 190-195.
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