Our current understanding of demographic and clinical modifiers of the effectiveness of multiple sclerosis (MS) therapies is limited.
To assess whether patients’ response to disease modifying therapies (DMT) in MS varies by disease activity (annualised relapse rate, presence of new MRI lesions), disability, age, MS duration or disease phenotype.
Using the international MSBase registry, we selected patients with MS followed for ≥1 year, with ≥3 visits, ≥1 visit per year. Marginal structural models (MSMs) were used to compare the hazard ratios (HR) of 6-month confirmed worsening and improvement of disability (EDSS), and the incidence of relapses between treated and untreated periods. MSMs were continuously re-adjusted for patient age, sex, pregnancy, date, time from first symptom, prior relapse history, disability and MRI activity.
Among 23 687 patients with relapsing MS, those on DMT experienced 20% greater chance of disability improvement [HR 1.20 (95% CI 1.0-1.5)], 47% lower risk of disability worsening [HR 0.53 (0.39-0.71)] and 51% reduction in relapses [HR 0.49 (0.43-0.55)]. The effect of DMT on relapses and EDSS worsening was attenuated with longer MS duration and higher prior relapse rate. The effect of DMT on EDSS improvement and relapses was more evident in low EDSS categories. DMT was associated with 51% EDSS improvement in patients without new MRI lesions [HR 1.51 (1.00-2.28)] compared to 4% in those with MRI activity [HR 1.04 (0.88-1.24)]. Among 26329 participants with relapsing or progressive MS, DMT was associated with 25% reduction in EDSS worsening and 42% reduction in relapses in patients with relapsing MS [HR 0.75 (0.65-0.86) and HR 0.58 (CI 0.54-62), respectively], while evidence for such beneficial effects of treatment in patients with progressive MS was not found [HR 1.11 (0.91-1.46) and HR 1.16 (0.91-1.46), respectively].
DMTs are associated with reduction in relapse frequency, progression of disability, and increased chance of recovery from disability. In general, the effectiveness of DMTs was most pronounced in subgroups with shorter MS duration, lower EDSS, lower relapse rate and relapsing MS phenotype.