Changes in Multiple Sclerosis Drug Coverage under Benefit Redesign in 2025 

With the implementation of the Inflation Reduction Act (IRA) Part D redesign provision in 2025, plan sponsors are facing substantially increased liability and associated pressures to manage cost. As a result, many Part D sponsors shifted their plan offerings and formularies in 2025, leading to access changes for beneficiaries. While these changes have occurred across the market, there were more pronounced shifts in 2025 Part D formularies for therapeutic areas and plan types where liability under Part D redesign increased most. One therapeutic area that experienced notable changes in plan coverage for 2025 is multiple sclerosis (MS) treatments. 

A previous Avalere analysis found that MS treatments were already tightly managed by Part D plans in 2024. In 2025, coverage of MS drugs declined even further, with more significant changes for certain types of products and plans.  

Overall coverage of self-administered MS drugs across all Part D plans dropped by six percentage points, from 49% of the time across all plans and drugs analyzed in 2024, to 43% in 2025. While coverage decreased for both Medicare Advantage Prescription Drug Plans (MA-PDs) and standalone Prescription Drug Plans (PDPs) in 2025, coverage varies across the two plan types. In 2025, coverage of all MS drugs was 17 percentage points higher for MA-PDs compared to PDPs, with MA-PDs covering MS drugs half the time across all plans and drugs analyzed compared to only about a third of the time for PDPs (Figure 1).  

Figure 1: Coverage of MS Drugs Among Part D Plans, by Plan Type, 2024 vs. 2025 

While coverage of MS drugs with generics available remained high in 2025 for both PDPs and MA-PDs, PDPs have more limited coverage of MS drugs without generics available. In 2025, PDPs covered brand-name MS drugs without generics available 15% of the time—less than half of the coverage among MA-PDs (34%). Coverage of brand MS drugs without generics available decreased by five percentage points for PDPs and seven percentage points for MA-PDs in 2025 (Figure 2).  

Figure 2: Coverage of MS Drugs by Part D Plan Type and Generic Availability, 2024 vs. 2025 

Implications for Beneficiary Access  

Higher coverage of MS drugs among MA-PDs likely reflects differences in cost pressures faced by PDPs vs. MA-PDs and additional flexibilities MA-PDs have in managing liability shifts (e.g., management of spending across benefits, more control over prescribing, and additional MA rebate dollars from the government). As Part D plans respond to the IRA changes and enrollment continues to shift towards MA-PDs, these differences in formulary management may disproportionately impact drug access for certain beneficiary groups based on their plan enrollment.   

Additionally, while Part D plans favor generic options, declining coverage for brand-name MS drugs without any generic alternatives may create access challenges for beneficiaries who are stable on certain medications and who may need to switch to a different therapy or plan.  

To learn more about how the IRA Part D changes are impacting the Part D market, connect with us. 

Methodology 

Avalere used CMS Part D Public Use Files to assess plan coverage of Part D, self-administered MS drugs from 2024 to 2025. Avalere analyzed and summarized coverage at the contract/plan level and averaged across all plans and plan types in the year. 2024 results are weighted by enrollment as of September 2024 and 2025 results are weighted by October 2025 enrollment.  

Funding for this research was provided by Novartis. Avalere retained full editorial control.