OBJECTIVES: Formulary restriction tools can be employed to manage the utilization of therapies among beneficiaries. We examined the subsequent plan generosity on disease-modifying therapy (DMT) and its potential effect on disease outcomes among multiple sclerosis (MS) patients with Medicare.

METHODS: We used 100% of the Medicare administrative data from 2017 to 2020 including plan and formulary characteristics, beneficiary enrollment, and medical and pharmacy (Part D) claims. Beneficiaries with a diagnosis of MS and with any combination of three or more inpatient, outpatient, and /or DMT prescription were eligible for the analysis. Plans were defined as low coverage if 4 or fewer MS drug classes were covered, and high coverage if 5 or more MS drug classes were covered. We used multivariate regression models to examine MS relapse and mortality by plan restrictiveness, controlling for patient demographics and disease severities.

RESULTS: A total of 78,407 eligible beneficiaries were selected for the analysis, of which 54,626 patients were with fee-for-service (FFS) Medicare and 23,781 patients were with Medicare Advantage (MA). In binary logistic model, high plan coverage of DMT was associated with lower chances of inpatient and/ or outpatient relapse (adjusted estimate: -0.048, p < 0.05) for all patients, and was associated with lower chances of death (adjusted estimate: -0.057) for all patients as opposed to low plan coverage. In Cox survival analysis, high plan coverage of DMT was associated with lower risks of inpatient and/ or outpatient relapse (HR: 0.964, p < 0.05) for all patients, and was associated with lower risks of death (HR: 0.953) for all patients compared with low plan coverage.

CONCLUSIONS: Narrower coverage of MS treatments might lead to worse disease outcomes for beneficiaries. Formulary placement should be tailored to patient needs besides management of costs and utilization.