Pegfilgrastim — Drug Monograph

Brand names: Neulasta, Fulphila (biosimilar), Udenyca (biosimilar), Ziextenzo (biosimilar), Nyvepria (biosimilar), Stimufend (biosimilar)

Drug class: Supportive Care Agent

Mechanism of Action

PEGylated recombinant human G-CSF — filgrastim covalently conjugated with a 20 kDa polyethylene glycol (PEG) moiety at the N-terminus. PEGylation dramatically reduces renal clearance (tubular secretion), extending the serum half-life from ~3.5 h (filgrastim) to ~15–80 h (pegfilgrastim). Uniquely self-regulating pharmacokinetics: when neutrophil counts are low (nadir), G-CSFR-mediated uptake by neutrophils is minimal and systemic exposure is highest — providing maximal G-CSF stimulus precisely when needed. As neutrophils recover and receptor-mediated clearance resumes, serum levels fall…

FDA Indications

• Prophylaxis of chemotherapy-induced febrile neutropenia in patients with non-myeloid malignancies receiving myelosuppressive anti-cancer drugs associated with a ≥17% incidence of febrile neutropenia (FDA approved January 2002)
• Hematopoietic subsyndrome of acute radiation syndrome (H-ARS) to increase survival (FDA approved 2015)

Common Side Effects

• Bone / medullary pain (26–31% — most common; reflects bone marrow stimulation; managed with NSAIDs, loratadine)
• Injection site reactions
• Fatigue
• Headache
• Nausea
• Leukocytosis (expected; hold if WBC >100,000)

Clinical Pearl

Pegfilgrastim has largely replaced daily filgrastim for primary febrile neutropenia prophylaxis in most chemotherapy regimens — a single dose per cycle vs 7–14 daily injections dramatically improves adherence. Loratadine (non-sedating antihistamine) 10 mg daily for 5–7 days starting the day after injection significantly reduces bone pain. The on-body Onpro injector placed on day of chemo and auto-firing at 27 h offers the most convenient delivery. Biosimilars are FDA-designated as…

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