<p>Pegfilgrastim, a Granulocyte Colony-Stimulating Factor (G-CSF) is a pegylated glycoprotein that regulates the production and release of functional neutrophils from bone marrow. Pegfilgrastim is a covalent conjugate of recombinant methionyl human G-CSF (Filgrastim) and monomethoxy polyethylene glycol. Filgrastim is a water soluble 175 amino acid protein with a molecular weight of approximately 19 kilodaltons (kD) and a 20 kD monomethoxy polyethylene glycol molecule is covalently bound to the N-terminal methionyl residue of filgrastim. The average molecular weight of pegfilgrastim is approximately 39 kD.</p>