Risk of early relapse following the switch from injectables to oral agents for multiple sclerosis

Background and Purpose: Early relapse outcomes in long-term stable patients switching from interferon β/glatiramer acetate (IFNβ/GA) to oral therapy are unknown. Objective: The objective of this study was to compare early relapse and progression in multiple sclerosis (MS) patients switching to oral therapy following a period of stable disease on IFNβ/GA, relative to a propensity-matched comparator of patients remaining on IFNβ/GA. Methods: The MSBase cohort study is a global, longitudinal registry for MS. Time to first 6-month relapse in previously stable MS patients switching from platform injectables ('switchers') to oral agents were compared with propensity-matched patients remaining on IFNβ/GA ('stayers') using a Cox marginal model. Results: Three-hundred and ninety-six switchers were successfully matched to 396 stayers on a 1:1 basis. There was no difference in the proportion of patients recording at least one relapse in the first 1-6 months by treatment arm (7.3% switchers, 6.6% stayers; P = 0.675). The mean annualized relapse rate (P = 0.493) and the rate of first 6-month relapse by treatment arm (hazard ratio 1.22, 95% confidence interval 0.70, 2.11) were also comparable. There was no difference in the rate of disability progression by treatment arm (hazard ratio 1.43, 95% confidence interval 0.63, 3.26). Conclusion: This is the first study to compare early relapse switch probability in the period immediately following switch to oral treatment in a population previously stable on injectable therapy. There was no evidence of disease reactivation within the first 6 months of switching to oral therapy.