Medications
Bosutinib (Bosulif)
A once-daily tablet or capsule (Bosulif) for chronic myeloid leukemia (CML) that carries the Philadelphia chromosome; it blocks the BCR-ABL growth signal that drives the leukemia.
How Medicare covers it
Part D (forms used at home). Part A during a covered inpatient stay. No Part B clinician-administered form in the CMS Part B spending file.
| Coverage details | |
|---|---|
| Part B status | No bosutinib row in the CMS Part B Spending by Drug HCPCS file (RY26, data through 2024) — no J-code basis; coverage path is Part D. |
| 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
Philadelphia chromosome-positive chronic myelogenous leukemia (Ph+ CML): chronic phase disease in adults and children 1 year and older, either newly diagnosed or resistant/intolerant to prior therapy; and accelerated or blast phase disease in adults with resistance or intolerance to prior therapy.
What it is for, in depth
Bosulif is a targeted leukemia tablet for chronic myelogenous leukemia that carries the Philadelphia chromosome (Ph+ CML). It fits two places in the treatment path: as an initial (first-line) treatment for newly diagnosed chronic-phase CML in adults and children age 1 and older, and as a later-line treatment at any phase when an earlier kinase inhibitor stopped working or could not be tolerated (including accelerated and blast phase disease in adults). Because it blocks most imatinib-resistant forms of BCR-ABL — though not the T315I form — mutation testing and prior-treatment history shape where it is used. It comes as 100 mg, 400 mg, and 500 mg tablets and 50 mg and 100 mg capsules (all in this package), which lets the 400 mg, 500 mg, and up-to-600 mg daily doses and dose reductions be built exactly.
How it works
Bosutinib is a tyrosine kinase inhibitor (TKI): it blocks BCR-ABL, the abnormal kinase created by the Philadelphia chromosome that drives CML, and also blocks Src-family kinases. It inhibited 16 of 18 imatinib-resistant forms of BCR-ABL in laboratory models (it does not block the T315I or V299L mutant forms).
How it is taken
By mouth once a day with food; tablets swallowed whole (do not cut, crush, break, or chew). Adults: 400 mg a day for newly diagnosed chronic phase CML; 500 mg a day when prior therapy failed or was not tolerated; the dose can rise by 100 mg steps to a maximum of 600 mg a day for incomplete response. Capsules (50 mg and 100 mg) can be swallowed whole or opened and mixed with applesauce or yogurt for patients who cannot swallow them. Treatment continues until the leukemia progresses or the drug is not tolerated.
Common side effects
The most common reactions (at least 20%) were diarrhea, abdominal pain, vomiting, nausea, rash, fatigue, liver dysfunction, headache, fever, decreased appetite, respiratory tract infection, and constipation. The most common laboratory abnormalities (at least 20%) included raised creatinine, low hemoglobin, low lymphocyte and platelet counts, raised liver enzymes (ALT/AST), low calcium, low white cell counts, and raised glucose, lipase, and amylase.
Serious warnings
Gastrointestinal toxicity (diarrhea, nausea, vomiting, abdominal pain) is managed with supportive care and dose holds or reductions. Myelosuppression requires regular blood-count monitoring. Liver toxicity requires liver-enzyme checks at least monthly for the first 3 months. Other labeled risks: cardiovascular toxicity, fluid retention, kidney toxicity, and embryo-fetal toxicity — Bosulif can cause fetal harm, and effective contraception is advised.
Who should be careful
Blood counts, liver enzymes, and kidney function are monitored during treatment (liver enzymes at least monthly for the first 3 months). Dose adjustments are made for toxicity and for liver or kidney impairment. Females of reproductive potential must use effective contraception because of fetal-harm risk.
Major interactions
Bosutinib is broken down by CYP3A: the label's interaction program centers on strong CYP3A inhibitors raising bosutinib levels and strong CYP3A inducers lowering them, so those combinations are avoided or dose-adjusted per the label, and acid-reducing drugs (proton pump inhibitors) can lower absorption. Readers should have their full medication list reviewed against the Bosulif label before starting.
Cost and saving notes
This is a Tier 5 specialty drug in most plans: Medicare's 2027 Part D out-of-pocket cap ($2,400 for the year) and Extra Help (the Part D low-income subsidy) are the main Medicare cost routes.
Why it is in its tier
Bosutinib (Bosulif) sits on Tier 5 — the specialty tier — in 96.91% of the plans that list it, and every Part D plan in the 2027 file lists it (100%). Tier 5 is the highest tier: patients usually pay a percentage of the drug's cost (coinsurance) rather than a flat copay. The data-visible drivers match that placement: Bosulif is a brand-only cancer medicine with no generic, and CMS dashboard average spending is about $118,784 per beneficiary for 2024 — among the highest-cost drugs in Part D, exactly the cost level the specialty tier exists for. The tier shown is the most common one; individual plans vary.
Sources
What official patient guides say
This text covers the tablet form only, because that is the form the MedlinePlus page describes; this package also includes bosutinib capsules, and the page gives no daily-life directions for the capsules. In daily life, bosutinib tablets are taken by mouth with food, usually once a day, at about the same time every day. Swallow the tablets whole and do not split, chew, or crush them, and do not touch a broken or crushed tablet with your bare hands. Keep taking it even if you feel well, and do not stop it without talking to your doctor; your doctor may pause your treatment or change your dose based on how you respond and any side effects. If you forget a dose, take the missed dose with food as soon as you remember it. If it has been more than 12 hours since your last dose, skip the missed dose and go back to your regular schedule. Do not take a double dose to make up for a missed one. Keep it in the container it came in, tightly closed, at room temperature and away from extra heat and moisture (not in the bathroom), and out of the sight and reach of children. Get rid of medicine you no longer need through a medicine take-back program and do not flush it down the toilet.
Source: MedlinePlus — Bosutinib
Part D formulary coverage
| Formulary summary | |
|---|---|
| Most common tier | 5 |
| Plans listing this drug | 5495 |
| Total Part D plans | 5495 |
| Share of plans listing it | 100 |
| Formularies listing it | 286 |
| Tier | Plans |
|---|---|
| Tier 1 | 123 plans |
| Tier 2 | 1 plans |
| Tier 4 | 46 plans |
| Tier 5 | 5325 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 copay | $0 — half of plans charge between $0 and $0 |
| Typical coinsurance | 26.0% of the price |
| Based on | 5237 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 2026-11-07
Similar medications
Other medications in the same FDA pharmacologic class (Kinase Inhibitor):
Read next
Part D spending averages (2024)
| Brand name | Generic name | Total claims 2024 | Total spending 2024 | Total beneficiaries 2024 | Rank by beneficiaries 2024 |
|---|---|---|---|---|---|
| Bosulif | Bosutinib | 15541 | 2.35312e+08 | 1981 | 1531 |
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
5,495 plans from 509 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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