Persistence and adherence to disease modifying drugs among patients with multiple sclerosis

Objective: This retrospective database study aimed to evaluate the adherence of multiple sclerosis (MS) patients on immunomodulatory treatments using claims data, and to identify differences between compliance and persistency measurements in the context of this disease. Methods: Continuously enrolled MS patients treated with subcutaneous IFN beta-1b (Betaseron*), subcutaneous IFN beta-1a (Rebif dagger), intramuscular IFN beta-1a (Avonex double dagger), and subcutaneous glatiramer acetate (Copaxone ).) were identified from the PharMetrics patient-centric database, and all information related to patient demographics and pharmacy claims for the drugs of interest were extracted. Outcome measures: The main outcomes were treatment switches and discontinuations for patients initiated on the drugs of interest. Various compliance and persistency metrics including the proportion of days covered, treatment prevalence at 6-monthly time points after initiation, and the continuous time on drug were also examined. Results: A total of 6134 MS patients were started on one of the four drugs of interest. The number of patients switching or discontinuing therapy rose over the study period. The proportion of patients switching was similar between study drugs, by the different metrics, with the highest switch rates for subcutaneous IFN beta-1b and the lowest for subcutaneous glatiramer acetate. Discontinuation rates were highest for subcutaneous IFN beta-1b and lowest for intramuscular IFN Chi-1a. Regression models showed that intramuscular IFN beta-1a and subcutaneous IFN beta-1a had similar and higher persistency compared to subcutaneous IFN beta-1b and subcutaneous glatiramer acetate. Conclusions: Although treatment switching and discontinuation is common in MS patients, there is some noticeable variability between drugs and across measures of persistency and adherence. Also, claims data do not allow distinguishing between clinical patterns of MS, direct estimation of disease severity and observation of care that occurs outside of insurance coverage, and results need to be cautiously interpreted. The compliance to the various MS drugs was 80% or higher at all times for all four drugs. The highest rate of treatment persistency existed in the intramuscular IFN beta-1a initiator group, while subcutaneous IFN beta-1b was associated with a significantly lower persistence (p<0.0001).