When Medicare’s second round of drug price negotiations made headlines last year, the attention went almost entirely to Ozempic and its sister weight-loss drugs. Lost in that coverage were two cancer treatments on the same list: Xtandi, used mainly for advanced prostate cancer, and Ibrance, used for certain breast cancers, both of which carry negotiated prices that take effect January 1, 2027. Together with a dozen other medicines, they represent Medicare’s attempt to bring down costs on drugs that, unlike a monthly diabetes prescription, can run tens of thousands of dollars for a single course of treatment.
The list goes well beyond the diabetes and weight-loss drug
Under the Inflation Reduction Act, the Centers for Medicare & Medicaid Services selects Part D drugs for negotiation based on how much Medicare spends on them and how long they have gone without generic or biosimilar competition. On January 17, 2025, CMS published its second list of 15 drugs, and Ozempic, Rybelsus and Wegovy topped it by a wide margin, accounting for $14.4 billion in Part D spending and 2.29 million enrollees in the year of data CMS used to build the list.
Xtandi and Ibrance sit further down the same list, but their inclusion reflects a different kind of cost problem. According to CMS’s own figures, Xtandi accounted for roughly $3.16 billion in Part D spending despite only about 35,000 enrollees using it, and Ibrance accounted for close to $1.98 billion in spending among just 16,000 users — a per-patient cost far higher than the drugs that dominate headlines. The full list of 15 also includes treatments for multiple myeloma, lung disease, leukemia and bipolar disorder, covering roughly 5.26 million Medicare Part D enrollees in total.
All 15 drugs combined accounted for about $40.7 billion in Part D spending, or roughly 14 percent of total Part D drug costs, during the 12-month period CMS used to determine eligibility — a scale that put pressure on the program well before any one drug’s name became a talking point.
Free prescription checklist: When a drug’s price or coverage rule changes, the next refill is where it shows up. Get the free coverage and pharmacy checklist.
Free download from RetireShield. Getting it also signs you up for the free Retirement Money Brief, a weekday email. Unsubscribe anytime.
What changes for two specific cancer drugs
Xtandi, known generically as enzalutamide, is an oral medication prescribed for prostate cancer that has spread or resists standard hormone therapy, and it is typically taken indefinitely rather than for a fixed course. Because it is a daily pill rather than an infusion, its cost falls more heavily on Part D drug coverage than on the medical-benefit side of Medicare, which is exactly the spending pattern that made it a target for negotiation.
Ibrance, known generically as palbociclib, is prescribed for certain forms of metastatic breast cancer and is often combined with hormone therapy. Tracking by AARP places Ibrance’s list price at well over $16,000 a month before any negotiation, which explains why a comparatively small group of 16,000 enrollees generated nearly $2 billion in Part D spending in a single year.
For both drugs, the negotiated price CMS agreed to with the manufacturer becomes the price Part D plans and pharmacies must use starting January 1, 2027, regardless of what a patient’s specific plan currently charges. Neither drug disappears from formularies or requires a new prior authorization process because of the negotiation; the change is strictly to what Medicare and, by extension, the patient’s cost-sharing are based on.
How large the combined price cut could be
Across all 15 drugs on the second negotiation list, AARP’s tracking of the program reports an average reduction of roughly 44 percent from list prices, translating to an estimated $685 million in out-of-pocket savings for Part D enrollees who use these medications once the new prices take effect. Because Xtandi and Ibrance carry some of the highest per-patient costs on the list, patients taking either drug stand to see a larger dollar reduction than someone on a lower-cost medication from the same list, even if the percentage cut is similar.
CMS’s own timeline shows the negotiation period for this group of drugs closed in the fall of 2025, with any agreed-upon prices due to be published by the end of November 2025 and a fuller public explanation of each negotiated price due by March 1, 2026 — well ahead of the January 1, 2027 effective date, giving both Medicare plans and patients a runway to adjust before the new prices apply.
The practical effect for someone currently on Xtandi or Ibrance is that any 2027 cost estimate built on this year’s price is likely to overstate what the drug will actually cost once the negotiated price takes hold, a distinction worth raising directly with a plan’s customer service line or a pharmacist rather than assuming next year’s bill will simply track this year’s.
That gap between an old estimate and the negotiated number also matters for anyone comparing Part D plans during Open Enrollment this fall. A plan’s current formulary pricing tool may not yet reflect the January 2027 negotiated price, so a side-by-side plan comparison built entirely on today’s numbers could steer a Xtandi or Ibrance patient toward a plan chosen for the wrong reason, particularly if a competing plan’s premium and the drug’s post-negotiation cost would have pointed to a different choice.
Planning Around a Cancer-Drug Cost That Is About to Change
A negotiated price arriving on a fixed date is easy to miss until a pharmacy bill either drops sharply or stays the same for reasons that have nothing to do with the news coverage a drug got the year before.
The Medicare Cost & Coverage Protection Kit includes the new Part D out-of-pocket cap and the prior-authorization appeal steps, along with a medication and cost tracker built for comparing what a plan charged last year against what it should charge once a new price takes effect.
Compare last year’s drug costs with the new Part D cap using the medication and cost tracker in The Medicare Cost & Coverage Protection Kit.
This article was produced with the assistance of AI and reviewed by The Money Overview editorial team before publication.
