To describe trends in Medicare Part D drug spending for disease-modifying therapies (DMTs) in multiple sclerosis (MS) as well as autoimmune neurological-related disorders (ANRD) from 2013 to 2021.

The number of available DMTs for MS and ANRD has increased significantly over the past several years. This study investigates the budget impact of MS and ANRD DMTs from the perspective of the Centers for Medicaid and Medicare. 

This is a retrospective analysis of prescription claims in the Medicare Part D Prescriber Public Use Files from 2013 to 2021. We included claims prescribed by clinicians with the taxonomy “Neurology”, “MS”, or “ANRD,” as well as the observed percentage change under the three categories: oral, injectable, and infusion drugs. 

79 drugs were included in the analysis, with 18 injectable, 31 oral, and 30 infusible DMTs representing 18,293,588 claims, and generating payments of $11.2 billion. The number of DMT claims increased from 15,814,057 in 2013 to 20,217,865 in 2021, a 24.3% increase, but the total payment increased by 112.2%. The proportion of total claims specifically for infusible DMTs has declined from 11.9% to 6.2%, yet the expenses associated with infusible medications have nearly tripled, climbing from 13.7% to 39.7% of the total payments across all DMTs.

Medicare Part D's payments for MS and ANRD drugs increased consistently, and above inflation, from 2013 to 2021 (24.1% of the US healthcare inflation rate of the medical care index). The Inflation Reduction Act of 2022 has several provisions to lower prescription drug costs for Medicare and reduce drug spending by the federal government; accordingly, the cost of MS and ANRD DMTs, particularly infusible medications, should be considered for potential legislative provisions with the goal of reducing the cost burden on the CMS budget.