Filgrastim-Sndz

Introduction Overview

Generic Name

filgrastim-sndz

Brand Name

Zarxio

Dosage Form

Prefilled syringe, single-dose vial (some vial formulations discontinued)

Drug Class

Colony stimulating factors

Pharmacokinetics

Absorption:
Filgrastim-sndz (Zarxio) is administered via subcutaneous injection, which allows its active protein component to be absorbed through the subcutaneous tissue into systemic circulation. Following subcutaneous injection, absorption is generally complete, with peak plasma concentrations achieved within 2 to 8 hours. The rate and extent of absorption may vary according to injection site and local blood flow. Clinical studies have demonstrated that Zarxio exhibits bioavailability comparable to its reference biologic, Neupogen. Since filgrastim is a protein therapeutic, oral absorption is negligible, necessitating injection for effective delivery. Distribution:
Once absorbed, filgrastim distributes primarily within the vascular and interstitial spaces. The volume of distribution approximates plasma volume, indicating limited extravascular distribution. It binds selectively to the granulocyte colony-stimulating factor (G-CSF) receptors on hematopoietic cells in the bone marrow, which serves as its pharmacodynamic target. The binding to receptors facilitates its biological activity, and this receptor-mediated interaction plays a key role in the drug's disposition. Filgrastim does not extensively cross the blood-brain barrier. Metabolism:
Filgrastim is metabolized predominantly through receptor-mediated endocytosis and subsequent intracellular degradation by the reticuloendothelial system, mainly in the bone marrow and liver. This pathway results in the breakdown of the peptide into smaller peptide fragments and amino acids. The drug does not undergo hepatic cytochrome P450 metabolism, which reduces the potential for drug-drug interactions common with small molecule agents. The metabolic clearance is saturable and influenced by the number of circulating neutrophils and their expression of G-CSF receptors. Elimination:
Filgrastim is eliminated mainly by renal clearance and degradation within the bone marrow and liver. The elimination half-life after subcutaneous administration ranges from approximately 3.5 to 3.8 hours, though this can vary depending on neutrophil counts; higher neutrophil levels generally increase clearance. Renal excretion accounts for partial elimination of intact filgrastim, but a substantial amount is cleared by receptor-mediated endocytosis and proteolysis. Due to its peptide nature, filgrastim is not subject to biliary excretion. The elimination kinetics and short half-life necessitate daily dosing in many treatment protocols. Overall, Zarxio demonstrates pharmacokinetics analogous to its reference product Neupogen, with predictability favorable for clinical use in neutropenia management.

Dosage Forms

Available Dosage Forms:
Zarxio is available as prefilled syringes and single-dose vials. The currently marketed dosage forms include:
- Prefilled syringe (300 mcg/0.5 mL)
- Prefilled syringe (480 mcg/0.8 mL)
The single-dose vial presentations (300 mcg/mL and 480 mcg/1.6 mL) have been discontinued.
Dosages for Adults and Adolescents:
Dosing with Zarxio is weight-based and varies depending on the indication. For chemotherapy-induced neutropenia, the usual dose is 5 mcg/kg/day administered subcutaneously starting at least 24 hours after chemotherapy and continuing until postnadir neutrophil recovery. In acute myeloid leukemia patients receiving induction or consolidation chemotherapy, dosing may range from 5–10 mcg/kg/day as determined by the treating physician. For peripheral blood progenitor cell mobilization in patients undergoing bone marrow transplantation, higher single-day doses may be used (e.g., 10 mcg/kg/day). The duration and dosing schedule should be individualized based on blood cell counts and clinical response. Specific Patient Populations:
In patients with renal impairment, no specific dosage adjustment is typically required, but clinical monitoring is prudent. In pediatric use, dosing is also weight-based and typically mirrors adult regimens but must be defined by the treating hematologist/oncologist. There is limited data on use during pregnancy and breastfeeding; risk-benefit assessment is critical before administration. Zarxio dosing may require modification in patients with sickle cell anemia or other hematologic conditions due to potential adverse effects. The drug is contraindicated in patients with known hypersensitivity to filgrastim or similar granulocyte colony-stimulating factors. Patients receiving chemotherapy should not be given Zarxio within 24 hours before or after chemotherapy to avoid interference with cytotoxic agents.

Mechanism Of Action

Zarxio (filgrastim-sndz) is a recombinant granulocyte colony-stimulating factor (G-CSF) analog that mimics the endogenous human G-CSF responsible for modulating neutrophil production. Upon subcutaneous injection, filgrastim binds with high affinity to specific G-CSF receptors located on hematopoietic progenitor cells within the bone marrow. This receptor binding triggers intracellular signaling cascades primarily via the JAK/STAT and PI3K pathways, leading to increased proliferation, differentiation, and survival of neutrophil precursors.
By promoting the maturation of neutrophil progenitor cells, filgrastim enhances the functional capacity of neutrophils, thereby boosting innate immune defense. This is crucial in patients undergoing chemotherapy who are at risk of neutropenia-induced infections due to myelosuppression. Filgrastim also accelerates the release of mature neutrophils from the bone marrow into the bloodstream, shortening the duration of neutropenia.
At the molecular level, the binding of filgrastim to its receptor induces receptor dimerization and activation, leading to phosphorylation events that regulate gene transcription involved in cell cycle progression and anti-apoptotic pathways. This includes upregulation of Bcl-2 family proteins that enhance neutrophil survival. Additionally, filgrastim promotes phagocytic and oxidative burst functions of mature neutrophils, augmenting their ability to combat pathogens.
Comparatively, other colony-stimulating factors like sargramostim (GM-CSF) act on a broader spectrum of myeloid cells, whereas filgrastim selectively targets neutrophil lineage. Clinical trials have demonstrated that filgrastim reduces the incidence of febrile neutropenia, infection-related complications, and hospitalization duration in oncology patients. The biosimilar filgrastim-sndz (Zarxio) has shown equivalent efficacy and safety profiles to the reference biologic Neupogen, supporting its interchangeable clinical use.

Pharmacological Actions

Stimulates proliferation and differentiation of neutrophil progenitor cells in the bone marrow.
Enhances functional activity of mature neutrophils, including chemotaxis, phagocytosis, and bacterial killing.
Accelerates neutrophil recovery following myelosuppressive chemotherapy.
Increases peripheral blood neutrophil counts, reducing the risk of infection.
Mobilizes hematopoietic stem cells and progenitor cells into peripheral blood for collection during leukapheresis.
Mitigates severity and duration of chemotherapy-induced neutropenia.
Reduces incidence of febrile neutropenia in patients receiving cytotoxic therapy.
Supports recovery of neutrophil populations following bone marrow transplantation.
Improves survival in individuals exposed to acute radiation by enhancing hematopoietic recovery.
Does not interfere with other hematopoietic lineages unlike broader colony-stimulating factors.
Well tolerated with pharmacodynamic effects dose-dependent and reversible upon discontinuation.

Therapeutic Or Clinical Uses

Prevention and treatment of neutropenia in patients receiving myelosuppressive chemotherapy for non-myeloid malignancies.
Mobilization of peripheral blood progenitor cells prior to autologous stem cell transplantation.
Treatment of severe chronic neutropenia including congenital, cyclic, or idiopathic forms.
Shortening the duration of neutropenia and associated fever in patients with acute myeloid leukemia undergoing induction or consolidation chemotherapy.
Supportive care to accelerate neutrophil recovery post bone marrow transplantation.
Reduction of infection rates and associated morbidities in immunocompromised oncology patients.
Management of hematopoietic syndrome of acute radiation syndrome (ARS) following radiation exposure.
Adjunctive therapy to decrease febrile neutropenia incidence in high-risk chemotherapy regimens.
Alternative treatment to biosimilar products for patients requiring filgrastim therapy.
Used in patients undergoing myelosuppressive treatment to maintain chemotherapy dose intensity by reducing neutropenia-related delays.

Side Or Adverse Effects

Bone pain, commonly mild to moderate, believed related to marrow expansion.
Fever and chills occurring during treatment.
Headache and dizziness, sometimes related to injection.
Fatigue and weakness reported in some patients.
Nausea and diarrhea as non-specific gastrointestinal effects.
Injection site reactions including redness, swelling, and tenderness.
Splenomegaly with rare cases of spleen rupture; symptoms include left upper quadrant pain and left shoulder pain.
Acute respiratory distress syndrome (ARDS), a rare but potentially fatal lung injury.
Capillary leak syndrome, characterized by rapid weight gain, edema, and hypotension.
Allergic reactions ranging from rash and itching to severe anaphylaxis including swelling of face and airways.
Transient leukocytosis and elevated neutrophil counts.
Rare development or exacerbation of sickle cell anemia crises in susceptible individuals.
Potential for myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) with prolonged use in certain patient populations.
Vasculitis including symptoms of skin rash, numbness, and systemic signs like fever and night sweats.
Kidney impairment characterized by swelling, decreased urine output, and shortness of breath.

Precautions

Avoid use in patients with known hypersensitivity to filgrastim or other granulocyte colony-stimulating factors.
Use cautiously in patients with sickle cell anemia due to risk of vaso-occlusive crisis.
Monitor patients with history of radiation exposure or underlying hematologic disorders for risk of MDS or AML.
Carefully assess kidney function before and during therapy; dose adjustment may be necessary.
Avoid injection into areas of skin that are tender, bruised, red, hard, scarred, or with stretch marks.
Do not administer filgrastim within 24 hours before or after chemotherapy to prevent interference with cytotoxic effects.
Use with caution in patients with latex allergy if injection components contain latex.
Ensure proper injection technique to minimize injection site reactions and avoid contamination.
Instruct patients to report any symptoms indicative of splenic enlargement or respiratory distress immediately.
Pregnancy and lactation use only when clearly needed; assess benefits versus potential risks.
Monitor blood counts regularly to adjust dosing and detect adverse hematologic effects.
Educate patients on recognizing signs of infection despite filgrastim use; neutropenia may still occur.
Inform patients about storage conditions to maintain drug stability and effectiveness.
Use careful clinical judgement when switching between biosimilars or reference biologics.
Review all concomitant medications to prevent potential interactions.

Warnings

Risk of acute respiratory distress syndrome (ARDS), a serious and potentially fatal lung condition.
Capillary leak syndrome, presenting with sudden weight gain, swelling, rapid breathing, fatigue, and decreased urination.
Splenic enlargement with potential for rupture; emergency medical attention required for left upper abdominal or shoulder pain.
Hypersensitivity reactions including anaphylaxis; discontinue therapy and seek immediate care if they occur.
Potential induction or exacerbation of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) with prolonged exposure.
Avoid administering Zarxio within 24 hours before or after chemotherapy or bone marrow transplantation.
Increased risk of sickle cell anemia crisis in patients with underlying hemoglobinopathies.
Filgrastim may mask signs of infection; patients must be monitored closely despite treatment.
Use caution in patients with pre-existing renal impairment due to potential nephrotoxicity.
May cause transient leukocytosis; laboratory monitoring is essential to differentiate from infection or malignancy.
Injection site infections are possible; aseptic technique must be strictly followed.
Use caution in patients prone to inflammatory or autoimmune vascular disorders due to rare vasculitis reports.
Zarxio may interfere with certain laboratory tests; inform healthcare providers of ongoing treatment.
Discontinue if capillary leak syndrome or ARDS is suspected and seek urgent medical management.
Safety in pediatric patients under certain ages or in pregnant women has not been fully established.

Contraindication

Known hypersensitivity to filgrastim-sndz or any component of the product.
Hypersensitivity to other granulocyte colony-stimulating factors including pegfilgrastim, tbo-filgrastim, sargramostim, and eflapegrastim.
History of severe allergic reactions to filgrastim or similar biologics.
Patients with active sickle cell anemia crisis or unstable sickle cell disease without close monitoring.
Use within 24 hours before or after cytotoxic chemotherapy or bone marrow transplantation.
Patients with hypersensitivity to any excipients such as polysorbate 80 or sorbitol found in the formulation.
Subjects with untreated splenic enlargement or splenic rupture should avoid administration until resolved.
Individuals with active severe pulmonary disease associated with ARDS are contraindicated.
Patients with capillary leak syndrome should not receive Zarxio until medically cleared.
Patients concurrently receiving other experimental hematopoietic agents without established safety.
Contraindicated in patients with latex allergies if product components contain natural rubber.
Individuals with myelodysplastic syndrome or AML at risk without prior hematologic evaluation.
Patients with known hypersensitivity to water for injection or sodium hydroxide as excipients.
Subjects exhibiting acute infection with severe systemic symptoms until stable.
Children or pregnant women unless benefits clearly outweigh potential risks as per physician discretion.

Drug Interactions

Avoid using Zarxio within 24 hours before or after chemotherapy to minimize antagonistic effects.
Concomitant use with other colony-stimulating factors may increase risk of hematologic toxicity and is not recommended without clinical justification.
Use caution with drugs that affect renal function as clearance of filgrastim may be altered.
No significant interactions with cytochrome P450 enzymes; low risk of interaction with CYP substrates.
Potential pharmacodynamic interactions with immunosuppressive agents, requiring close monitoring of neutrophil counts.
Drugs affecting bone marrow function (e.g., myelosuppressive agents) may alter Zarxio's efficacy.
Concurrent administration with corticosteroids may modify immune response and hematopoietic effects.
Interactions with live vaccines are theoretically possible due to effects on immune cell populations; caution advised.
Medications causing fluid retention or edema may exacerbate capillary leak syndrome when combined with Zarxio.
Drugs with pro-inflammatory vascular effects may increase risk of vasculitis in Zarxio-treated patients.
Certain antibiotics and antifungals administered during neutropenic episodes may influence neutrophil recovery assessment.
Herbal supplements with immune-modulating properties should be disclosed to healthcare providers due to unpredictable interactions.
Interactions with analgesics or anti-inflammatory drugs are minimal but should be monitored for additive side effects.
Potential for increased side effects if combined with other proteins or biologics affecting immune or hematopoietic systems.
Use with nephrotoxic agents requires monitoring of renal function to prevent accumulation or toxicity.

Preparations Of The Drug

Zarxio is supplied as a sterile, preservative-free, clear and colorless to slightly yellow solution for subcutaneous injection.
Available as prefilled syringes containing 300 mcg/0.5 mL and 480 mcg/0.8 mL concentrations.
Single-dose vials of 300 mcg/mL and 480 mcg/1.6 mL were previously available but have been discontinued.
Inactive ingredients include glutamic acid, polysorbate 80, sorbitol, sodium hydroxide, and water for injection USP.
Packaged in temperature-controlled, light-protected containers; must be refrigerated at 2-8°C (36-46°F).
Prefilled syringes are provided with safety needles or needle caps for ease of administration.
Do not freeze, shake, or expose the product to heat; allow it to reach room temperature prior to injection.
Dispose of used needles and syringes in approved puncture-resistant sharps containers.
Available through prescription with specific storage and handling instructions to maintain protein stability.
Manufactured by Sandoz Inc., Princeton, NJ, USA, with production in Grenzach-Wyhlen, Germany.
Biosimilar status ensures high similarity in structure, safety, and efficacy compared to the reference product Neupogen.
Each preparation is intended for single-use only; any remaining product must be discarded after administration.
Supplied without preservatives; aseptic technique is essential during preparation and administration.
Packaging includes patient information leaflets detailing dosing, storage, and administration guidelines.
Prefilled syringes are designed for subcutaneous administration with instructions for patients and caregivers.
Product is subject to regulatory controls regarding interchangeability and biosimilarity per FDA guidelines.