Medications
Tbo-filgrastim (Granix)
An injection given under the skin that helps the body make more white blood cells (neutrophils) after certain chemotherapy, so the chance of infection while counts are low is smaller and the low-count period is shorter.
How Medicare covers it
Split path: Granix given in a clinic follows Part B (J1447 — see the Part B basis in this package); self-injected at home it is listed in Part D formularies, and the Part D aggregation in this package is carried exactly as computed. Part A during a covered inpatient stay.
| Coverage details | |
|---|---|
| Part B status | CMS Part B Spending by Drug HCPCS file (RY26, data through 2024) carries J1447 (tbo-filgrastim, Granix): the clinician-administered path is Part B. Tbo-filgrastim is its own RxNorm ingredient — originator filgrastim (J1442, Neupogen) and the filgrastim biosimilars (filgrastim-sndz Q5101, filgrastim-aafi Q5110, filgrastim-ayow Q5125) are different products and are explicitly NOT matched. |
| Medicare Advantage | Most Medicare Advantage plans that include drug coverage (MAPD plans) use the same formulary-and-tier system; the plan's own drug list decides coverage and copay — check the plan's formulary. |
| Medicare Supplement (Medigap) | Medicare Supplement (Medigap) plans sold today do not include prescription drug coverage; drug coverage comes from Part D or an MAPD plan. |
What it treats
GRANIX is indicated to reduce the duration of severe neutropenia in adult and pediatric patients 1 month and older with non-myeloid malignancies receiving myelosuppressive anticancer drugs associated with a clinically significant incidence of febrile neutropenia.
What it is for, in depth
Granix is supportive care for cancer chemotherapy, not a cancer treatment itself. Many chemotherapy drugs temporarily shut down the bone marrow's production of neutrophils — the white blood cells that fight bacterial infection. When counts fall to their lowest point (the nadir), even a fever can signal a dangerous infection (febrile neutropenia). Granix is a lab-made copy of the body's own G-CSF signal that tells the marrow to make neutrophils; given daily after each chemotherapy cycle, starting at least a day after chemo, it shortens the number of days the patient spends with severe neutropenia. The labeled population is adults and children 1 month and older with non-myeloid cancers (cancers that are not of the bone marrow/blood-forming type) receiving myelosuppressive chemotherapy regimens associated with a clinically significant incidence of febrile neutropenia. Tbo-filgrastim is its own ingredient: it is not filgrastim (Neupogen) and it is not one of the filgrastim biosimilars (Zarxio, Nivestym, Releuko), which are separate products with their own packages in this category, although all are G-CSF products used at the same 5 mcg/kg dose. It comes as single-dose prefilled syringes and vials, and the label allows trained patients or caregivers to give the under-the-skin injections at home.
How it works
Tbo-filgrastim is a human granulocyte colony-stimulating factor (G-CSF) produced by recombinant DNA technology. It binds to G-CSF receptors and stimulates proliferation of neutrophils; G-CSF also stimulates differentiation commitment and some end-cell functional activation, which increases neutrophil counts and activity.
How it is taken
The recommended dose is 5 mcg/kg per day administered as a subcutaneous (under the skin) injection. The first dose is given no earlier than 24 hours following myelosuppressive chemotherapy, and GRANIX is not given within 24 hours prior to chemotherapy; daily dosing continues until the expected neutrophil nadir is passed and the neutrophil count has recovered to the normal range, with complete blood counts monitored prior to chemotherapy and twice per week until recovery. GRANIX may be administered by a healthcare professional, or by a patient or caregiver after proper training. It is supplied as single-dose prefilled syringes (300 mcg/0.5 mL and 480 mcg/0.8 mL, the formulary concepts in this package are the Granix prefilled syringes and the 300 mcg/mL vial) and single-dose vials (300 mcg/mL and 480 mcg/1.6 mL); injection sites include the abdomen (except the two-inch area around the navel), the front of the middle thighs, the upper outer buttocks, and the upper back portion of the upper arms, varied daily.
Common side effects
The most common adverse reaction to GRANIX is bone pain. Other adverse reactions known to occur following administration of filgrastim products include myalgia (muscle aches), headache, vomiting, cutaneous vasculitis, and thrombocytopenia. In the pediatric study, the most common (more than 5%) adverse reactions were thrombocytopenia (34%), pyrexia (fever, 8%), pain in extremity (6%), headache (6%), and diarrhea (6%). White blood cell counts above 100,000 were observed in less than 1% of patients receiving GRANIX, with no complications attributed to leukocytosis in clinical studies.
Serious warnings
Splenic rupture, including fatal cases, can occur following administration of filgrastim products — patients who report upper abdominal or shoulder pain should be evaluated for an enlarged spleen or splenic rupture. Acute respiratory distress syndrome (ARDS) can occur; patients who develop fever and lung infiltrates or respiratory distress after receiving GRANIX should be evaluated for ARDS. Serious allergic reactions, including anaphylaxis, can occur, including on initial exposure, and GRANIX must be permanently discontinued in patients with serious allergic reactions. Severe and sometimes fatal sickle cell crises can occur in patients with sickle cell disorders receiving filgrastim products. Glomerulonephritis and capillary leak syndrome (hypotension, hypoalbuminemia, edema, and hemoconcentration, which may be life-threatening if treatment is delayed) can occur. The label also warns about myelodysplastic syndrome and acute myeloid leukemia in certain settings, aortitis, alveolar hemorrhage, and that the G-CSF receptor has been found on tumor cell lines, so a growth-factor effect on tumors (including myeloid malignancies and myelodysplasia, for which GRANIX is not approved) cannot be excluded. GRANIX is contraindicated in patients with a history of serious allergic reactions to filgrastim products or pegfilgrastim products.
Who should be careful
Patients with a history of serious allergic reactions to filgrastim or pegfilgrastim products must not receive GRANIX (contraindicated). Patients with sickle cell disorders are at risk of severe and sometimes fatal sickle cell crises. GRANIX is indicated only for patients with non-myeloid malignancies receiving myelosuppressive chemotherapy — the diagnosis of severe chronic neutropenia should be confirmed before initiating therapy in that setting, and the label notes MDS and AML have been reported in the natural history of severe chronic neutropenia. Patients given the drug at home must be appropriate candidates for self-administration, with proper training on storage, preparation, and administration technique; otherwise a healthcare professional should administer it.
Major interactions
The GRANIX label has no drug-interaction section naming interacting medicines. Its labeled combination cautions are about timing and setting: do not administer GRANIX within 24 hours prior to chemotherapy or earlier than 24 hours following myelosuppressive chemotherapy, and simultaneous use with chemotherapy and radiation therapy is not recommended.
Why it is in its tier
In the CMS 2027 formulary aggregation, the most common (modal) tier for tbo-filgrastim is Tier 5 — the specialty tier — the tier it sits on in 59.73% of the plans that list it, and only 149 plans (2.71%) list it at all. Tier 5 usually means the patient pays a percentage of the cost (coinsurance) rather than a flat copay. The data-visible drivers: Granix is a brand-only biologic — tbo-filgrastim has no generic version and is not a biosimilar of filgrastim — used by a small population (2,050 Part D beneficiaries in 2024), with CMS dashboard average spending of $2,171.91 per beneficiary in 2024 (a program average, not a reader's copay). Brand biologics in the G-CSF class are the kind of product plans place on the specialty tier, and most plans instead list one or more filgrastim biosimilars. When Granix is administered in a clinic, the Part B path in this package applies; the tier shown is the most common Part D placement among the few listing plans, and individual plans vary.
Sources
What official patient guides say
The MedlinePlus page for this drug is a shared page titled Filgrastim Injection. It lists Granix (tbo-filgrastim) by name as one of the products it covers, and it also covers other filgrastim products and other uses that are not part of this package — this text is scoped to Granix given under the skin after chemotherapy. A nurse or other healthcare provider may give the injection, or you or a caregiver may be taught to inject it under the skin at home; make sure you understand the directions and ask your provider if you have questions. Use it exactly as directed and do not use more, less, or more often than your doctor prescribed. Do not shake the vial or syringe. Before each injection, look at the liquid: do not use it if the date has passed, or if the liquid has particles or looks foamy, cloudy, or discolored. Use each syringe or vial only once, even if liquid is left over, and throw used needles, syringes, and vials away in a hard, puncture-proof container. Store Granix in the refrigerator, out of reach of children. The page states the Granix-specific storage rule: Granix can be taken out of the refrigerator and put back, but it should not be out of the refrigerator for more than 5 days in total, and it should be protected from light. If you inject at home and forget a dose, the page does not give a make-up rule — it says to talk to your doctor about what you should do if you forget to inject the medication on schedule.
Source: MedlinePlus — Filgrastim Injection (Granix / tbo-filgrastim)
Part D formulary coverage
| Formulary summary | |
|---|---|
| Most common tier | 5 |
| Plans listing this drug | 149 |
| Total Part D plans | 5495 |
| Share of plans listing it | 2.71 |
| Formularies listing it | 10 |
| Tier | Plans |
|---|---|
| Tier 1 | 1 plans |
| Tier 3 | 44 plans |
| Tier 4 | 15 plans |
| Tier 5 | 89 plans |
Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.
What you pay
| With Medicare Part D | |
|---|---|
| Most common tier | Tier 5 |
| Typical coinsurance | 25.0% of the price |
| Based on | 88 plans that cover this drug · 2027 plan year |
A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.
Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-08
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Part D spending averages (2024)
| Brand name | Generic name | Total claims 2024 | Total spending 2024 | Total beneficiaries 2024 | Rank by beneficiaries 2024 |
|---|---|---|---|---|---|
| Granix | Tbo-Filgrastim | 5220 | 4.45242e+06 | 2050 | 1517 |
Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30
Companies covering this drug
149 plans from 23 companies list this drug on a formulary for 2027. Search by company or plan name, or filter by tier. Cost sharing is the plan's published amount for this drug's tier in the initial coverage stage (1-month retail supply), where the plan publishes it; a blank means the plan does not publish it.
| Company | Plan | Tier | Copay | Coinsurance |
|---|
A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.
Coverage and costs change. Drug lists (formularies), tiers, and copays can change during the year and differ by plan. Always check with your insurance company or plan directly to confirm what is covered and what you will pay.
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