One molecule, eight Medicare prices, one cash price

What Medicare Part B pays per milligram in the July 2026 quarter, by label, next to what one milligram costs in cash at Cost Plus. The Part B amount is the payment limit CMS publishes for each billing code. The Cost Plus amount is the syringe price divided by its milligrams.

Seven ustekinumab biosimilars carry a Part B code in July 2026. Six of them appear in the January 2026 file at far higher amounts than they carry now. CMS prices a new code from the manufacturer's list price until it has two quarters of sales data. The list-price quarters are visible: Selarsdi was paid $43.20 per mg in January and $11.14 in April. Yesintek went from $24.68 to $3.21. The October column is the preliminary file CMS published on 2026-09-08.

Most ustekinumab is a subcutaneous maintenance dose, one 45 mg or 90 mg syringe every 8 to 12 weeks, and it runs through Part D. Part D gross spending on Stelara tripled from 2020 to 2024. It reached $3.38 billion for 24,754 beneficiaries: $136,464 per person and $25,424 per claim, before manufacturer rebates. The cash price of the same dose, as a Starjemza syringe at Cost Plus, is $360.

Adalimumab (Humira) went through the same transition in 2023. By 2024 nine biosimilars were on the market. Part D still paid $5.72 billion for Humira on 652,028 claims, $8,766 per claim. The biosimilars together drew $162 million on 51,072 claims, $3,173 per claim. Humira kept 92.7% of adalimumab claims in its second year of competition. Cost Plus sells a two-pen adalimumab-fkjp kit, a month at the standard 40 mg every-other-week dose, for $423.25.

Every biosimilar and interchangeable product licensed by FDA under section 351(k), with its reference product, and the Part B payment limit for each where a billing code exists in the July 2026 file. "Ratio" is the biosimilar limit divided by the reference limit when both are priced per the same unit. 50 pairs have both codes. 17 biosimilars are paid at under half the reference. 10 are paid at or above it. 48 biosimilars have no Part B code, mostly because they are pharmacy-dispensed (adalimumab, etanercept, insulins) or too new.

Sources. Medicare Part B payment limits come from the CMS ASP Pricing Files, quarterly, July 2026 final and October 2026 preliminary. Biosimilar and interchangeable licensure comes from the FDA Purple Book. Medicare spending comes from the CMS Medicare Part B and Part D Spending by Drug files, calendar years 2020 to 2024. Cost Plus Drugs prices were captured from the company's medication pages on 2026-09-10 and are the listed price for one syringe or kit, before shipping and dispensing fees.

Matching. Each Purple Book product is matched to a Part B billing code through the CMS NDC-to-HCPCS crosswalk for the same quarter, by brand name. The reference product is matched the same way. Where a brand maps to more than one code, the code with the most NDCs is used.

Caveats. The payment limit is what Medicare pays a physician or hospital outpatient department per billing unit. It includes the statutory add-on, which for a biosimilar is computed on the reference product's average sales price, so a biosimilar limit is not the biosimilar's own sales price. A new code is paid from the list price until sales data exist, which explains the high first-quarter amounts in 2026. Part D figures are gross drug cost before manufacturer rebates, which for Stelara and Humira are large and confidential. Part B and Part D reach different patients through different channels; the comparison here is the price of the same milligrams, not a claim that one could replace the other. Otulfi's Cost Plus price ($877.50 for 45 mg, $1,350 for 90 mg) is higher per mg than its Part B limit; Starjemza's is lower than every Part B ustekinumab limit.