What Is Releuko? Uses, Dosage, and What You Need to Know in 2026

If you or a family member has been prescribed Releuko (filgrastim-ayow), you probably have questions. What is it? Why do I need it? How is it given? This guide covers the essentials of Releuko in plain language — what it does, who takes it, how it's dosed, and what makes it different from similar medications.

What Is Releuko?

Releuko is the brand name for filgrastim-ayow, a recombinant human granulocyte colony-stimulating factor (G-CSF). In plain terms, it is a laboratory-made version of a protein your body naturally produces to stimulate white blood cell (specifically neutrophil) production in your bone marrow.

Releuko is a biosimilar to Neupogen (filgrastim), the original FDA-approved G-CSF medication. It was developed by Kashiv Biosciences and is marketed by Amneal Pharmaceuticals. It received FDA approval on February 25, 2022, becoming the third filgrastim biosimilar available in the United States, joining Zarxio and Nivestym.

What Is Releuko Used For?

Releuko has several FDA-approved indications:

Chemotherapy-induced neutropenia: The most common use. Chemotherapy kills cancer cells but also reduces white blood cells, leaving patients vulnerable to infection. Releuko is given after chemotherapy to stimulate the bone marrow to make more neutrophils, reducing the risk of life-threatening infections (febrile neutropenia).

Acute myeloid leukemia (AML) support: Given after induction or consolidation chemotherapy for AML to accelerate neutrophil recovery.

Bone marrow transplant support: Given to help the body recover its white blood cell production after myeloablative chemotherapy and bone marrow transplantation.

Stem cell (PBPC) mobilization: Used before leukapheresis to mobilize stem cells from the bone marrow into the blood for collection and later transplantation.

Severe chronic neutropenia (SCN): For patients with congenital, cyclic, or idiopathic neutropenia, Releuko is used as ongoing therapy to maintain adequate neutrophil levels and prevent recurrent infections.

Hematopoietic acute radiation syndrome: Used to increase survival in patients acutely exposed to myelosuppressive doses of radiation.

How Is Releuko Given?

Releuko is given as an injection — either under the skin (subcutaneous injection) or directly into a vein (intravenous infusion). It is never taken as a pill.

Subcutaneous injection (SQ): Can be self-administered by the patient or caregiver at home after training. Common injection sites include the belly, thighs, or upper arms.

Intravenous infusion (IV): Administered as a 15–30 minute infusion or continuous drip in a hospital or infusion center. Used when higher doses are needed (e.g., for BMT support).

Important: Releuko should NOT be given within 24 hours before or after cytotoxic chemotherapy.

What Are the Common Doses?

Dosing for Releuko is individualized based on body weight and indication:

Chemotherapy-induced neutropenia: 5 mcg/kg/day SC or IV, starting at least 24 hours after the last chemotherapy dose

Bone marrow transplant: 10 mcg/kg/day IV infusion

PBPC mobilization: 10 mcg/kg/day SC for at least 4 days before leukapheresis

Congenital neutropenia: Starting dose 6 mcg/kg twice daily SC (individualized based on clinical response and ANC)

Idiopathic/cyclic neutropenia: Starting dose 5 mcg/kg once daily SC

How Is Releuko Different From Neupogen?

Releuko is a biosimilar to Neupogen, meaning it is highly similar to the reference product and has no clinically meaningful differences in safety or effectiveness. The key differences are:

Releuko has the suffix "-ayow" added to its nonproprietary name to distinguish it as a biosimilar

Releuko is typically less expensive than brand Neupogen

Like other biosimilars, Releuko cannot be automatically substituted for Neupogen at the pharmacy — a new prescription is required

For a deeper look at how Releuko works at the molecular level, read our article on how Releuko works. And if you're having trouble finding it, medfinder calls pharmacies near you to locate it.