Report on Part D Tiering Shows Low Coverage Rates for Biosimilars

Despite the US having more biosimilar options than ever before, Medicare Part D plans still prefer reference insulin glargine (Lantus) and adalimumab (Humira) over lower-priced biosimilar alternatives, according to a report from the Association for Accessible Medicines (AAM).

The report looked at results from Avalere’s analysis on understanding the distribution of biosimilars relative to their originators on Medicare Part D formulary tiers for program year (PY) 2023. Avalere synthesized public use files (PUFs) from PY 2024 to assess coverage, tiering, and utilization management of drugs covered under Part D plans, including Medicare Advantage plans, focusing specifically on the insulin glargine, adalimumab, epoetin alfa, pegfilgrastim, and filgrastim markets.

Avalere included over 5500 plans across all 50 states and Washington, DC, and the 5 largest Part D parent organizations in 2023 (United Healthcare, Humana, CVS, Centene, Cigna), regardless of whether they covered any of the studied products.

By parent organization, the researchers looked at:

• 893 United plans
• 758 Humana plans
• 793 CVS plans
• 475 Centene plans
• 339 Cigna plans

Results showed that Lantus generally had higher coverage, preferred tiering, and less restrictive utilization management (UM) compared with its biosimilars. While 80% of plans covered branded or unbranded Lantus, less than 10% of plans covered branded or unbranded insulin biosimilars. There were also no differences in coverage for prefilled pens vs prefilled syringes for coverage, tiering, or UM. United Healthcare, CVS, Centene, and Cigna did not cover any insulin biosimilars.

Similarly, immunological agent biosimilars were significantly less likely to be covered by plans compared with their reference products. When covered, immunological agent biosimilars were typically placed on specialty tiers, indicating a higher level of restriction or management compared with reference products.

Humira biosimilars were not covered, and prior authorization was required for Humira, suggesting that plans were more inclined to cover the reference product rather than its biosimilars. UM strategies like prior authorization were commonly applied to control access to Humira. However, CVS, Cigna, and Centene did not cover any adalimumab biosimilars despite 8 products entering the market by the end of July 2023.

Although some biosimilars, such as Cyltezo, were covered by a higher number of plans compared with other Humira biosimilars, overall coverage of Humira biosimilars remained low across all plans, likely because it was the first adalimumab biosimilar to be granted interchangeability status.