Grasustek (Pegfilgrastim)
Pegylated granulocyte colony-stimulating factor (G-CSF) — biosimilar of Neulasta
Quick Facts About Grasustek
Key Takeaways
- Grasustek (pegfilgrastim) is a biosimilar of Neulasta, used to prevent neutropenia and febrile neutropenia during chemotherapy in adult cancer patients.
- A single 6 mg subcutaneous injection is given once per chemotherapy cycle, at least 24 hours after chemotherapy completion.
- The most common side effect is bone pain, which is usually mild and manageable with standard painkillers.
- Grasustek must not be used in patients with myelodysplastic syndrome (MDS) or chronic myeloid leukaemia (CML).
- The drug has a self-regulating mechanism: it stays active longer when neutrophil counts are low and clears faster as they recover.
What Is Grasustek and What Is It Used For?
Grasustek contains the active substance pegfilgrastim, which is a pegylated form of the naturally occurring protein granulocyte colony-stimulating factor (G-CSF). G-CSF is produced by the body to regulate the production of neutrophils within the bone marrow. Neutrophils are a critical component of the immune system, serving as the body's first line of defence against bacterial and fungal infections.
Chemotherapy drugs used to treat cancer are effective because they destroy rapidly dividing cells. Unfortunately, they also damage the bone marrow, which produces blood cells including neutrophils. This leads to a condition called neutropenia — an abnormally low level of neutrophils in the blood. Neutropenia leaves patients highly vulnerable to serious and potentially life-threatening infections, a complication known as febrile neutropenia when accompanied by fever.
Grasustek works by binding to specific receptors on haematopoietic (blood-forming) cells in the bone marrow, stimulating them to produce, mature, and release neutrophils into the bloodstream more rapidly. What makes pegfilgrastim particularly effective is its self-regulating pharmacokinetic profile. The PEG (polyethylene glycol) molecule attached to filgrastim reduces renal clearance, meaning the drug is primarily cleared by neutrophils themselves. When neutrophil counts are low (when protection is most needed), the drug persists in the body longer. As neutrophil counts recover, clearance increases and drug levels naturally decline.
Grasustek is indicated for the reduction in the duration of neutropenia and the incidence of febrile neutropenia in adult patients treated with cytotoxic chemotherapy for malignancy, with the exception of chronic myeloid leukaemia and myelodysplastic syndromes. It is typically recommended when the overall risk of febrile neutropenia is 20% or greater based on chemotherapy regimen, patient age, disease stage, and comorbidities.
As a biosimilar, Grasustek was developed to be highly similar to its reference product, Neulasta (the original pegfilgrastim by Amgen). The European Medicines Agency (EMA) approved Grasustek on 20 June 2019 after reviewing comprehensive data from Phase I and Phase III clinical studies that demonstrated comparable quality, safety, and efficacy to Neulasta. The marketing authorisation holder is Juta Pharma GmbH, based in Flensburg, Germany.
What Should You Know Before Taking Grasustek?
Contraindications
Grasustek must not be used in the following situations:
- Hypersensitivity: If you have a known allergy to pegfilgrastim, filgrastim, or any of the excipients (sodium acetate, sorbitol, polysorbate 20, water for injections).
- Myelodysplastic syndromes (MDS): Pegfilgrastim should not be used in patients with MDS as it may stimulate the growth of abnormal myeloid cells.
- Chronic myeloid leukaemia (CML): Similarly contraindicated due to the risk of stimulating leukaemic cell proliferation.
- Secondary acute myeloid leukaemia (AML): Patients with secondary AML should not receive pegfilgrastim.
Warnings and Precautions
Before starting Grasustek, your doctor should be made aware of any pre-existing conditions. Several serious but rare adverse effects require vigilance:
- Capillary Leak Syndrome: A rare but potentially life-threatening condition characterised by hypotension, swelling (oedema), and low blood albumin. Patients who develop these symptoms require immediate medical intervention.
- Pulmonary adverse reactions: Interstitial pneumonia, pulmonary oedema, lung infiltrates, and acute respiratory distress syndrome (ARDS) have been reported. Report any new or worsening respiratory symptoms such as cough, fever, or difficulty breathing immediately.
- Glomerulonephritis: Kidney inflammation has been observed. Regular monitoring of renal function is advised, particularly if symptoms such as facial swelling, blood in the urine, or elevated blood pressure develop.
- Sickle cell disease: Patients with sickle cell trait or sickle cell disease are at risk of severe sickle cell crises, which can be life-threatening. Use in these patients requires careful monitoring.
- Aortitis: Inflammation of the aorta has been reported. Patients should be aware of symptoms such as fever, abdominal pain, malaise, and back pain.
- Leukocytosis: White blood cell counts exceeding 100 × 109/L have been observed in less than 1% of patients. Although generally not associated with adverse clinical effects, regular blood count monitoring is recommended.
- Sorbitol content: Each pre-filled syringe contains 30 mg of sorbitol (E420). Patients with hereditary fructose intolerance should be informed of this.
Pregnancy and Breastfeeding
Pregnancy: Grasustek is not recommended during pregnancy unless clearly necessary. There are no adequate clinical data from the use of pegfilgrastim in pregnant women. Animal reproduction studies in rabbits showed embryo/fetal toxicity (embryo loss) at cumulative doses approximately 4 times the recommended human dose, while studies in rats did not show adverse effects on offspring. Women of childbearing potential should use effective contraception during treatment. Any decision to use Grasustek during pregnancy must involve a careful risk-benefit assessment by the treating oncologist.
Breastfeeding: There is insufficient information on whether pegfilgrastim or its metabolites are excreted into human breast milk. A risk to the nursing infant cannot be excluded. A clinical decision must be made weighing the benefits of breastfeeding for the child against the benefits of Grasustek therapy for the mother. Limited data suggest minimal excretion into breast milk, with levels becoming undetectable within approximately 3 days after injection.
Fertility: Non-clinical studies have shown that pegfilgrastim did not affect reproductive performance or fertility in male or female rats at doses 6 to 9 times higher than the recommended human dose.
How Does Grasustek Interact with Other Drugs?
Although formal drug interaction studies have not been conducted with Grasustek specifically, the interaction profile of pegfilgrastim is well characterised from the reference product and class-wide data. The most important consideration is the timing of administration relative to chemotherapy.
Major Interactions
| Interacting Drug/Class | Interaction | Clinical Recommendation |
|---|---|---|
| Cytotoxic chemotherapy (all agents) | Rapidly dividing myeloid cells are sensitive to cytotoxic drugs. Concurrent administration may negate the effect of pegfilgrastim. | Administer Grasustek at least 24 hours AFTER chemotherapy. Do not give within 14 days before the next cycle. |
| 5-Fluorouracil (5-FU) and antimetabolites | Animal studies show potentiated myelosuppression when G-CSF is given with antimetabolites. | Avoid concurrent use. Ensure adequate timing separation between 5-FU and Grasustek. |
| Sodium chloride (NaCl) solutions | Pegfilgrastim is incompatible with saline solutions and may aggregate, losing biological activity. | Must NOT be diluted or mixed with sodium chloride solutions or any other medicinal products. |
Minor Interactions
| Interacting Drug/Class | Interaction | Clinical Recommendation |
|---|---|---|
| Lithium | Lithium promotes neutrophil release, potentially enhancing the effect of pegfilgrastim. Clinical significance not established. | Caution advised. Monitor blood counts more frequently if used concomitantly. |
| Clozapine | G-CSF may mitigate clozapine-induced neutropenia, but data are limited. | If used concomitantly, monitor absolute neutrophil count (ANC) closely. |
| Nitrosoureas and mitomycin C | These agents cause delayed myelosuppression. Pegfilgrastim has not been evaluated in patients receiving these drugs. | Use with caution. Timing of Grasustek administration may need adjustment. |
Patients should always provide their oncologist and pharmacist with a complete list of all medications, including over-the-counter drugs and supplements, before starting Grasustek therapy. It is also important to inform healthcare providers of all ongoing therapies before each injection.
What Is the Correct Dosage of Grasustek?
Grasustek is supplied as a pre-filled syringe containing 6 mg of pegfilgrastim in 0.6 mL of solution (10 mg/mL based on protein content). The dosing regimen is straightforward, reflecting the drug's self-regulating pharmacokinetic profile which ensures prolonged activity precisely when neutrophil counts are at their lowest.
Adults
Standard Adult Dose
Dose: 6 mg (one pre-filled syringe) subcutaneously, once per chemotherapy cycle.
Timing: At least 24 hours after completion of cytotoxic chemotherapy. Must not be given within 14 days before the start of the next chemotherapy cycle.
Injection sites: Thigh, abdomen, or upper arm.
Preparation: Remove the syringe from the refrigerator and allow it to reach room temperature for approximately 30 minutes before injection. Inspect visually — the solution should be clear and colourless. Do not use if cloudy, discoloured, or containing particles. Do not shake vigorously as this may aggregate the pegfilgrastim protein and render it biologically inactive.
Children
Paediatric Use
The safety and efficacy of Grasustek have not been established in children and adolescents. No dosing recommendation can be made for the paediatric population. Use in patients under 18 years of age is not currently supported by available clinical data.
Elderly
Elderly Patients (>65 years)
No dose adjustment is required in elderly patients. Pharmacokinetic studies have shown similar drug behaviour in older adults compared to younger adults. However, elderly patients may be at increased risk for febrile neutropenia overall and should be monitored closely during chemotherapy treatment.
Missed Dose
Grasustek is typically administered in a clinical setting under medical supervision. If a dose is missed or not given at the expected time after chemotherapy, contact your oncology team as soon as possible. They will advise on the best course of action based on where you are in your chemotherapy cycle. Because each dose corresponds to a chemotherapy cycle, timing is critical for optimal neutrophil recovery.
Overdose
The maximum tolerated dose of pegfilgrastim has not been determined. In clinical studies, single subcutaneous doses of up to 300 micrograms per kilogram of body weight have been administered without dose-limiting toxicity. Adverse events observed at higher doses were similar to those at the recommended 6 mg dose. There is no specific antidote for pegfilgrastim overdose. Treatment is supportive and should include monitoring of white blood cell and platelet counts. Leukocytosis (excessively high white blood cell counts) may occur but typically resolves without intervention as the drug is cleared.
What Are the Side Effects of Grasustek?
Like all medicines, Grasustek can cause side effects, although not everybody gets them. Most side effects are mild to moderate and typically resolve on their own or with supportive treatment. However, some rare side effects can be serious and require immediate medical attention. The side effects listed below are categorised by how commonly they occur, based on clinical trial data and post-marketing surveillance.
Very Common
Affects more than 1 in 10 patients
- Bone pain (generally mild to moderate, transient, controllable with standard analgesics such as paracetamol or ibuprofen)
Common
Affects 1 in 10 to 1 in 100 patients
- Musculoskeletal pain (myalgia, arthralgia, extremity pain, back pain, neck pain)
- Injection site pain or redness
- Thrombocytopenia (low platelet count)
- Leukocytosis (elevated white blood cells)
- Nausea
- Headache
- Elevated uric acid, alkaline phosphatase, and lactate dehydrogenase (LDH) levels
- Transient liver function test elevations (ALT/AST)
Uncommon
Affects 1 in 100 to 1 in 1,000 patients
- Hypersensitivity reactions (skin rash, urticaria, angioedema, dyspnoea, flushing, hypotension)
- Serious allergic reactions and anaphylaxis
- Capillary leak syndrome (potentially life-threatening)
- Splenomegaly (enlarged spleen, generally asymptomatic)
- Pulmonary adverse reactions (interstitial pneumonia, pulmonary oedema, lung infiltrates)
- Sweet's syndrome (acute febrile neutrophilic dermatosis)
- Cutaneous vasculitis
- Glomerulonephritis (kidney inflammation)
- Non-cardiac chest pain
Rare
Affects fewer than 1 in 1,000 patients
- Splenic rupture (including fatal cases — seek immediate medical attention for upper left abdominal or left shoulder pain)
- Aortitis (inflammation of the aorta)
- Pulmonary haemorrhage or haemoptysis (coughing up blood)
- Acute respiratory distress syndrome (ARDS — may be life-threatening)
- Stevens-Johnson syndrome (very rare, severe skin reaction)
- Sickle cell crises (in patients with sickle cell trait or disease — can be severe and fatal)
If you experience any side effects, including those not listed above, talk to your doctor, pharmacist, or nurse. You can also report side effects directly to your national adverse drug reaction reporting system. By reporting side effects, you help provide more information on the safety of this medicine.
How Should You Store Grasustek?
Proper storage of Grasustek is essential to maintain its biological activity and ensure patient safety. As a biological medicine containing a protein-based active substance, pegfilgrastim is sensitive to temperature extremes and physical stress.
- Refrigeration: Store in a refrigerator at 2°C to 8°C. This is the recommended long-term storage condition.
- Do not freeze: If the syringe is accidentally frozen once for less than 24 hours, it can be thawed in the refrigerator and used. If frozen for longer, or frozen more than once, discard the syringe.
- Room temperature: The syringe may be left at room temperature (not above 30°C) for a maximum single period of up to 72 hours. If not used within this 72-hour window, the syringe must be discarded and should not be returned to the refrigerator.
- Light protection: Keep the pre-filled syringe in the outer carton to protect from light at all times until use.
- Shelf life: 3 years from the date of manufacture when stored correctly.
- Before injection: Allow the syringe to reach room temperature naturally for approximately 30 minutes. Do not use microwave or hot water to warm the syringe.
- Visual inspection: Before each use, check that the solution is clear and colourless. Do not use if it appears cloudy, discoloured, or contains visible particles.
Keep this medicine out of the sight and reach of children. Do not use after the expiry date stated on the carton and syringe label. Dispose of used syringes in an approved sharps container — do not recap needles. Do not throw away via household waste. Ask your pharmacist about proper disposal of medicines no longer required.
What Does Grasustek Contain?
Understanding the full composition of Grasustek is important for identifying potential allergies to any component and for understanding the pharmaceutical formulation.
Active Ingredient
Pegfilgrastim 6 mg per 0.6 mL (concentration: 10 mg/mL based on protein content). Pegfilgrastim is a covalent conjugate of recombinant human granulocyte colony-stimulating factor (r-metHuG-CSF, also known as filgrastim) with a single 20 kDa polyethylene glycol (PEG) molecule. It is produced by recombinant DNA technology in Escherichia coli cells, followed by covalent PEGylation.
Excipients (Inactive Ingredients)
| Excipient | Function | Notes |
|---|---|---|
| Sodium acetate | Buffer (maintains pH) | Formed by titrating glacial acetic acid with sodium hydroxide. Contains sodium. |
| Sorbitol (E420) | Stabiliser | 30 mg per syringe. Caution in patients with hereditary fructose intolerance. |
| Polysorbate 20 | Surfactant | Prevents protein aggregation and maintains solution stability. |
| Water for injections | Solvent | Provides the aqueous base for the solution. |
The syringe itself is made of Type I glass with a stainless steel needle and a needle cap containing dry natural rubber (a derivative of latex). Patients with known latex allergies should inform their healthcare provider before administration, though the risk of an allergic reaction is considered very low due to the minimal latex content.
Frequently Asked Questions About Grasustek
Grasustek (pegfilgrastim) is used to reduce the duration of neutropenia and the incidence of febrile neutropenia in adult patients receiving cytotoxic chemotherapy for cancer. It stimulates the bone marrow to produce more neutrophils, helping the immune system recover faster between chemotherapy cycles. It is administered as a single 6 mg subcutaneous injection once per chemotherapy cycle, at least 24 hours after chemotherapy completion.
Grasustek is a biosimilar of Neulasta. This means it contains the same active substance (pegfilgrastim) and has been shown to be highly similar to Neulasta in terms of quality, safety, and efficacy through rigorous comparative studies reviewed by the European Medicines Agency. Biosimilars undergo strict regulatory evaluation and must demonstrate that there are no clinically meaningful differences from the reference product. Grasustek was approved in the EU in June 2019.
The most common side effect is bone pain, which affects more than 1 in 10 patients. This is typically mild to moderate in severity, transient, and can be managed effectively with standard over-the-counter painkillers such as paracetamol (acetaminophen) or ibuprofen. Other common side effects include musculoskeletal pain, injection site reactions, nausea, headache, and changes in blood test results (thrombocytopenia, elevated liver enzymes, elevated uric acid).
Grasustek is administered as a single subcutaneous (under the skin) injection using a pre-filled syringe. It should be injected into the thigh, abdomen, or upper arm. The syringe must be allowed to reach room temperature for about 30 minutes before injection. It is given at least 24 hours after chemotherapy and should not be given within 14 days before the next chemotherapy cycle. Your healthcare team will demonstrate the correct injection technique if you will be self-administering at home.
Grasustek is not recommended during pregnancy unless the potential benefit justifies the potential risk to the foetus. There are no adequate clinical data from the use of pegfilgrastim in pregnant women. Animal studies have shown embryo/fetal toxicity at high doses. Women of childbearing potential should use effective contraception during treatment. If pregnancy occurs during treatment, inform your doctor immediately for a thorough risk-benefit assessment.
Store Grasustek in a refrigerator at 2–8°C. Do not freeze. Keep the syringe in the outer carton to protect from light. If needed, the syringe can be left at room temperature (below 30°C) for up to 72 hours, after which it must be discarded if not used. The shelf life is 3 years when stored according to these recommendations. Always check the expiry date and inspect the solution before use.
References
This article is based on the following peer-reviewed sources and authoritative medical guidelines:
- European Medicines Agency (EMA). Grasustek — EPAR Summary for the Public. EMA/360643/2019. European Medicines Agency, 2019.
- European Medicines Agency (EMA). Grasustek — Product Information (SmPC). Marketing authorisation: EU/1/19/1375/001. Last updated 2025.
- Aapro MS, Bohlius J, Cameron DA, et al. 2010 update of EORTC guidelines for the use of granulocyte-colony stimulating factor to reduce the incidence of chemotherapy-induced febrile neutropenia in adult patients with lymphoproliferative disorders and solid tumours. Eur J Cancer. 2011;47(1):8-32.
- Smith TJ, Bohlke K, Lyman GH, et al. Recommendations for the Use of WBC Growth Factors: American Society of Clinical Oncology Clinical Practice Guideline Update. J Clin Oncol. 2015;33(28):3199-3212.
- National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Hematopoietic Growth Factors. Version 1.2025. NCCN, 2025.
- Cornes P. The economic pressures for biosimilar drug use in cancer medicine. Target Oncol. 2012;7(Suppl 1):S57-S67.
- Blackwell K, Semiglazov V, Krasnozhon D, et al. Comparison of EP2006, a filgrastim biosimilar, to the reference: a pharmacokinetics-focused Phase III study. Ann Oncol. 2015;26(10):2103-2109.
- World Health Organization (WHO). WHO Expert Committee on Biological Standardization: Guidelines on evaluation of biosimilars. WHO Technical Report Series. Geneva: WHO, 2009.
- European Society for Medical Oncology (ESMO). Management of febrile neutropenia: ESMO Clinical Practice Guidelines. Ann Oncol. 2016;27(suppl_5):v111-v118.
- Pegfilgrastim. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing. Updated 2024. PMID: NBK532893.
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iMedic Medical Editorial Team — Specialists in oncology, haematology, and clinical pharmacology with documented academic background and clinical experience in chemotherapy support and biosimilar medicines.
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