OBJECTIVES: To estimate prescription drug cost for disease modifying therapy (DMT) and its impact on health care cost among individuals with Multiple Sclerosis (MS) enrolled in commercial insurance.

METHODS: This is a population based retrospective study using 2011-2015 Truven MarketScan data. We estimated prescription drug cost for DMT and its share of overall health care spending. Individuals aged <65 and with 12 month continuous enrollment for both medical and pharmacy benefits in any of measurement years were included. We identified individuals with MS who had at least two inpatient or outpatient claims with a diagnosis for MS with ICD-9-CM (340) /ICD-10-CM (G35) or one outpatient pharmacy claims for DMT during the measurement year. The cost was computed using total paid amounts by the insurance and patient and was inflation adjusted to 2015 dollars.

RESULTS: The average percentage of MS patients who were on DMT drugs was 72.3% and has grown from 70.9% to 74.1% over the 5 year study period. The mean annual health care cost (in 2015 adjusted dollars) for MS patients increased from $43,049 in 2011 to $59,096 in 2015 with 8.2% average annual growth rate. The mean annual prescription drug expense for DMT increased from $22,095 to $36,546 with 13.4% average annual growth rate while inpatient and outpatient costs remained steady or decreased. The proportion of DMT drug cost in annual health care cost constantly increased from 53.5% in 2011 to 61.8% in 2015. These trends were not only limited to MS patients on new DMT drugs approved by FDA but also applied to those on previously available DMT drugs.

CONCLUSIONS: Health care cost for MS patients rapidly increased, primarily due to the increase in the proportion of DMT cost and its increased utilization.