Closing the Part D Coverage Gap and Out-of-Pocket Costs for Multiple Sclerosis Drugs

To determine whether closing the Part D coverage gap (donut hole) between 2010 and 2019 lowered patients' out-of-pocket costs for disease-modifying therapies (DMTs) for multiple sclerosis (MS).

Using nationwide Medicare Formulary and Drug Pricing Files, we analyzed Part D drug benefit design and DMT prices in 2010, 2016, and 2019. We calculated average monthly list prices for DMTs available in each year (4 DMTs in 2010, 11 DMTs in 2016, and 14 DMTs in 2019). We projected patients' annual out-of-pocket cost for each DMT alone under a standard Part D plan in that year. We estimated potential savings attributable to closing the coverage gap between 2010 and 2019 (beneficiaries' cost sharing dropped from 100% to 25%) under 3 scenarios: no increase in price, an inflation-indexed price increase (3% annually), and the observed price increase.

Median monthly DMT prices rose from $2,804 to $5,987 to $7,009 over the years 2010, 2016, and 2019, respectively. Median projected annual out-of-pocket costs rose from $5,916 to $6,229 to $6,618. With unchanged or inflation-indexed DMT price changes, closing the coverage gap would have reduced annual out-of-pocket costs by $2,260 (38% reduction) and $1,744 (29% reduction), respectively. Despite having the lowest monthly price, generic glatiramer acetate had among the highest out-of-pocket costs ($6,731 to $6,939 a year) in 2019.

Medicare Part D beneficiaries can pay thousands of dollars yearly out of pocket for DMTs. Closing the Part D coverage gap did not reduce out-of-pocket costs for patients because of simultaneous increases in DMT prices.