A study by IQVIA finds that first prescription rejection rates were unchanged for the first MFP negotiated drugs after implementation in January.
A notable study by IQVIA found that for the first drugs subject to Medicare maximum fair price (MFP) agreements, initial rejection rates were not significantly lower than before the new prices took effect in January 2026.
One of the main stipulations of the MFP agreements was that if the reference drug manufacturer signed an MFP agreement, Medicare Part D drug plans and Medicare Advantage plans would have to cover the drug on their formularies.
Enbrel and Stelara Rejection Rates
Enbrel and Stelara are the two Part D drugs of interest in this first round of Medicare MFP negotiations. Enbrel has no current biosimilar competition (though 2 approved products), and Stelara has plenty of it.
These two drugs comprise the immunology sector of the first 10 drugs subject to MFP. According to the IQVIA data, the initial rejection rates for those new to the brand were 59% for the first quarter of 2026. When looking forward 30 days, the average rejection rate on appeal was 22%. In the past 5 years, the initial rejection rates ranged from 61% to 73%. IQVIA did not break down the rejection rates for the two individual biologics.
In their post, IQVIA said, “Expectations for Medicare drug price negotiation to improve patient access have yet to come to fruition. Even more concerning, additional future IPAY-selected drugs are in the immunology and oncology therapeutic areas and other therapeutic areas with similar costs and treatment complexity, facing similarly high levels of payer control.”
The Result of Heavy Biosimilar Competition?
Granted, both etanercept and ustekinumab are unusual products, in that they are both subject to heavy competition from other agents within the same or similar drug categories. In fact, the MFP for Stelara is not competitive with several ustekinumab biosimilars on the market today. The existence of over 10 adalimumab biosimilars at deep discounts would be a highly attractive prior step before approval of either Enbrel or Stelara. Therefore, it is unlikely that payers will significantly change coverage policies to improve access to these two agents under current conditions.
As more Part B medications are subject to MFP negotiations, patient access may change somewhat for those particular drugs. However, one must remember that patient access improvement was not the primary goal of Medicare MFP negotiations under the Inflation Reduction Act. The real goal was cost reduction for the Centers for Medicare & Medicaid Services.
As we can see, cost reduction may not equal better patient access, even if deep price reductions on biologics are available on direct-to-consumer sites because of relatively high patient out-of-pocket costs. Therefore, this finding is not surprising. We saw the same lack of effect when the adalimumab biosimilars were first introduced in 2023: Much lower costs didn’t result in prescriptions to patients; only formulary policy changes did.
Instead, I tend to view IQVIA’s study as more supportive of a 360-degree view of the effectiveness of biosimilar competition for these two medications.
This article was written by our Director of Content, Stanton Mehr. Stan has been writing commentary and reporting news about the biosimilar industry since the submission of the first biosimilar 351(k) application to the FDA 13 years ago. Since that time, BR&R has been tracking the US biosimilar marketplace, with the industry’s original, comprehensive and updated database of biosimilar filings with the FDA.
