Increasing formulary adoption of adalimumab biosimilars and differential cost-sharing in Medicare Part D plans.
By 2026, 45.9% of Medicare Part D plans provided biosimilar-exclusive coverage for adalimumab, with median specialty-tier coinsurance at 25% for these plans.
Where it sits
this study against the rest of the survodutide (bi 456906) corpusSummary and findings
This study evaluated the adoption of adalimumab biosimilars in Medicare Part D plans and their associated cost-sharing requirements. The analysis revealed that by 2026, 45.9% of plans provided biosimilar-exclusive coverage. Median specialty-tier coinsurance varied by coverage type, with percentages reported for different plans.
Abstract
<h4>Objectives</h4>Adalimumab was among the first biologics to face widespread biosimilar competition following US market entry of multiple adalimumab biosimilars in 2023. However, Medicare Part D formulary adoption of these products and their associated specialty-tier cost-sharing requirements remain unknown.<h4>Methods</h4>To evaluate adalimumab biosimilar adoption and associated cost-sharing patterns across Medicare Part D formularies, Centers for Medicare & Medicaid Services (CMS) Medicare Part D Formulary and Plan Benefit Package files were analyzed. Plans were categorized as covering originator adalimumab-only, both originator and biosimilar products (dual coverage), or biosimilars-only.<h4>Results</h4>In 2023, all Medicare Part D plans covering adalimumab listed only the originator product. By 2024, 52.5% of plans provided dual coverage, increasing to 79.9% in 2025. Biosimilar-exclusive coverage increased from 8.6% of plans in 2025 to 45.9% in 2026, while originator-only coverage declined to 0.8%. Median specialty-tier coinsurance differed according to coverage strategy. In 2026, median specialty-tier coinsurance was 33% among originator-only plans, 27% among dual-coverage plans, and 25% among biosimilar-only plans.<h4>Conclusions</h4>Medicare Part D formularies rapidly included adalimumab biosimilars following market entry, with substantial growth in biosimilar-exclusive coverage by 2026. Specialty tier coinsurance varied by medication coverage type, suggesting that evolving formulary strategies may influence beneficiary cost-sharing requirements.
Background
This paper addresses the adoption of adalimumab biosimilars in Medicare Part D plans following the entry of multiple biosimilars into the market in 2023. Prior to this study, the extent of formulary adoption and cost-sharing implications for beneficiaries were not well understood. Understanding these dynamics is crucial for evaluating the impact of biosimilars on healthcare costs and access.
Methods
The study analyzed Centers for Medicare & Medicaid Services (CMS) Medicare Part D Formulary and Plan Benefit Package files. Plans were categorized based on their coverage of adalimumab as either originator-only, dual coverage (originator and biosimilars), or biosimilars-only. The analysis focused on coverage patterns and specialty-tier cost-sharing.
Results
In 2023, all Medicare Part D plans covering adalimumab listed only the originator product. By 2024, 52.5% of plans provided dual coverage, which increased to 79.9% in 2025. Biosimilar-exclusive coverage rose from 8.6% in 2025 to 45.9% in 2026. In 2026, median specialty-tier coinsurance was 33% for originator-only plans, 27% for dual-coverage plans, and 25% for biosimilar-only plans.
Interpretation
The findings indicate a significant shift towards the adoption of biosimilars in Medicare Part D plans, with a notable increase in biosimilar-exclusive coverage by 2026. While the statistical significance of these changes is evident, the clinical relevance may depend on individual patient circumstances and the overall impact on healthcare costs. Limitations include the lack of detailed information on beneficiary outcomes and potential confounding factors related to plan design.
Key findings
- In 2023, all Medicare Part D plans covering adalimumab listed only the originator product.
- By 2024, 52.5% of plans provided dual coverage, increasing to 79.9% in 2025.
- Biosimilar-exclusive coverage increased from 8.6% of plans in 2025 to 45.9% in 2026.
- In 2026, median specialty-tier coinsurance was 33% among originator-only plans, 27% among dual-coverage plans, and 25% among biosimilar-only plans.
Limitations
- Not reported in abstract.