OBJECTIVES: To estimate the budget impact of adding peginterferon beta-1a, a new interferon requiring injections only every two weeks for the treatment of relapsing forms of multiple sclerosis (MS), to a managed care formulary in the US.

METHODS: An Excel model was developed to compare the drug-related costs of the current mix of treatments with the costs of an estimated treatment mix including peginterferon beta-1a for a managed care organization (MCO) with 1,000,000 covered lives. The number of people with relapsing forms of MS was estimated using published prevalence data. Treatment share of peginterferon beta-1a was assumed to increase from 3% in 2014 to 7% in 2018 taken proportionately by treatment shares from the other interferons indicated for MS. Drug costs included: acquisition costs adjusted by patient payments and dispensing fees as well as administration, monitoring, and adverse event costs. Annual relapse treatment costs were estimated using the relative risk reduction of a relapse for each DMT derived using a mixed-treatment comparison analysis A one-way sensitivity analysis was performed.

RESULTS: The estimated budget impact of adding peginterferon beta-1a to the formulary was negative for the first 5 years: in 2014, with a treatment share of 3.0%, the estimated budget decrease was 0.07% of the total annual costs for DMT-related and relapse treatment costs and a decrease of $0.005 per member per month (PMPM); in 2018, with a treatment share of 7%, the estimated budget decrease was 0.23% of the total annual costs and a decrease of $0.014 PMPM. Sensitivity analyses showed that the model was most sensitive to the acquisition costs of peginterferon beta-1a.

CONCLUSIONS: Under model assumptions for market shares, adding peginterferon beta-1a  to the MCO formulary would result in a small decrease in MCO costs for patients with relapsing forms of MS.