Patterns in Patient Access to MS Drugs

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Avalere analysis finds that less clinically efficacious MS drugs have better coverage, more advantageous tiering, and lower UM compared to more efficacious drugs.

Medicare Part D and commercial plans face pressure to curate a formulary for pharmacy benefit drugs amidst growing healthcare costs. The Centers for Medicare and Medicaid Services (CMS) offers various flexibilities for Part D plans to manage their benefit through formulary design (e.g., drug coverage, tiering) and utilization management (UM) (e.g., prior authorization, step therapy). These flexibilities are common across most markets of health insurance coverage for prescription drugs and are increasingly used in Part D. While CMS has oversight over Part D plan formularies, plans have considerable flexibility to design formularies that aim to balance patient access and plan cost.

While Part D plans are required to cover all drugs and are limited in the use of utilization management (UM) in the six protected classes, they are free to exclude products from their formularies or implement UM requirements in other classes to manage their spending and reduce premiums. In particular, non-protected classes that include higher cost drugs, including those for multiple sclerosis (MS), can be a formulary area of focus for Part D plans aiming to limit drug costs.

Analysis Details

Avalere was commissioned to evaluate Part D vs. commercial plan coverage and access for drugs used to treat Multiple Sclerosis (MS). Specifically, Avalere’s analysis aimed to evaluate trends in formulary coverage and access to MS therapies across Part D and commercial plans to assess how formulary coverage has changed over time and how it varies based on plan type, approval year, availability of a generic alternative, and drug efficacy. The analysis leveraged a study where the efficacy of MS drug therapies was evaluated based on the drug’s ability to reduce annualized relapse rates in Phase III clinical trials.

Avalere categorized drugs based on the following:

  • Approval year: Pre-2015 (older) vs. 2015 and later (newer)
  • Generic availability
  • Efficacy of drug: Low, moderate, or high

Analysis Findings

Drug Coverage

Coverage of MS drugs with earlier (pre-2015) approvals, generic availability, and lower efficacy is higher, on average, compared to newer MS drugs, those with no generics available, and MS drugs with higher efficacy (see Figure 1). Coverage of MS drugs was generally higher among commercial plans compared to Part D plans, although Medicare Advantage Prescription Drug plans (MA-PDs) cover these drugs more frequently than Prescription Drug Plans (PDPs).

  • Coverage of drugs approved prior to 2015 is 15 percentage points higher than drugs approved in 2015 or later among commercial plans in 2024 (88% vs. 73% covered). The difference in coverage jumps to 48 percentage points among MA-PDs (81% vs 33% covered) and 55 percentage points among PDPs (66% vs 11%).
  • Coverage for drugs with generics and without generics mirrored results based on approval year.
  • Drugs categorized as low- and high-efficacy are covered more frequently compared to moderate-efficacy drugs among commercial and MA-PDs. PDPs, however, cover low-efficacy drugs 58% of the time, moderate-efficacy 28% of the time, and high-efficacy drugs 7% of the time.

Figure 1: MS Drug Coverage by Subgroup and Plan Type, 2024

Formulary Tiering

Plans generally place MS drugs on higher, non-preferred or specialty tiers. Commercial plans place MS drugs on lower tiers compared to Part D plans. There are limited differences in tiering based on approval year or generic availability. Within those limited differences, MS drugs approved pre-2015 or with generics available are more frequently placed on the specialty tier than the non-preferred tiers compared to more recently approved drugs or those without generics available, respectively.

Utilization Management

For covered MS drugs, all plan types included in this analysis commonly apply UM across all sub-groups of drugs. Prior authorization is the predominant type of UM used, although a small proportion also use step therapy. On average, plans do not require UM as frequently for MS drugs approved pre-2015, drugs with generics available, and low-efficacy drugs, compared to their subgroup counterparts. Commercial plans and MA-PDs cover MS drugs with open access more frequently than PDPs.

  • Commercial plans apply UM 56% of the time for covered, low-efficacy drugs, 67% of the time for moderate-efficacy drugs, and 74% of the time for high-efficacy drugs.
  • MA-PDs apply UM similarly across efficacy levels for covered drugs (ranging from 56% to 62% of the time).
  • Although PDPs have lower coverage of MS drugs compared to commercial and MA-PDs, when these drugs are covered, UM is applied 84% (low-efficacy drugs) to 100% (high-efficacy drugs) of the time.

Figure 2: Plan Use of UM for Covered MS Drugs by Efficacy Level and Plan Type, 2024


The findings from this analysis highlight some of the ongoing challenges in Part D coverage across PDPs and MA-PDs relative to the commercial market. Part D plan liability coupled with permittable plan flexibilities are driving pressure on Part D plans—specifically PDPs—that result in differences in coverage across various MS drug characteristics. These distinctions in coverage across the types of Part D plans are expected to increase as the larger benefit design shifts of the Inflation Reduction Act (IRA) are implemented.

Stakeholders will likely continue to engage CMS on interventions that the agency might undertake related to Part D plan oversight. Stakeholders will likely pursue plan payment adequacy as they urge CMS to revisit its risk adjustment parameters. Alternatively, CMS’s formulary review process may be considered as a pathway to improve patient accessibility to treatments.

Given Part D plans’ increased liability under the IRA and other policy changes, it is unclear how plans will mitigate the additional risks and the subsequent impact on formularies. Specifically, the ongoing concern regarding the viability of the PDP market highlights the greater risk PDPs may face relative to MA-PDs.

To learn more about the Medicare Part D benefit and potential changes as a result of the Inflation Reduction Act, connect with us.


Avalere used CMS Part D Public Use Files (PUFs) and Clarivate formulary coverage data available from 2018 to 2024 for this analysis. Monthly Part D PUFs contain formulary, cost sharing and pharmacy network data for PDPs and MA-PDs. Avalere utilized formulary and policy restrictions information available through Clarivate to assess coverage, tiering and UM for drugs on commercial plans. Ingredient efficacy was assigned based a peer-reviewed research study. Avalere analyzed and summarized coverage at the contract/plan level and averaged across all plans and plan types in the year. All results are weighted based on plan enrollment.

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



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