Over three decades study populations in progressive multiple sclerosis have become older and more disabled, but have lower on-trial progression rates: A systematic review and meta-analysis of 43 randomised placebo-controlled trials.

Background: Progression is the major driver of disability and cost in multiple sclerosis (MS). However, the search for treatments in progressive multiple sclerosis (PMS) has not mirrored the success in relapsing MS. Objectives: To assess changes in PMS trials over time. Methods: PubMed, MEDLINE and Embase were searched to identify randomised, double-blind, placebo-controlled trials in PMS. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used, study quality was assessed and trends were examined by regression. Results: Placebo groups of 43 studies published between 1988 and 2018 were included. The mean age at trial entry increased by 9.8 years per decade (95% confidence interval (CI): [2.7; 4.9]; p < 0.001). Mean baseline Expanded Disability Status Scale (EDSS) scores increased by 0.36 points (95% CI: [0.09; 0.62]; p = 0.009) and disease durations at baseline were prolonged by 1.8 years (95% CI: [0.7; 2.9]; p = 0.003) per decade. The trials became larger, specifically placebo groups increased by about 222 patients (95% CI: [36; 409]; p = 0.021) and 88 patients (95% CI: [12; 165]; p = 0.025) per decade for primary progressive multiple sclerosis (PPMS) and secondary progressive multiple sclerosis (SPMS), respectively. The proportion of patients on placebo experiencing disability progression within 24 months decreased by 7.6 percentage points (95% CI: [1.2; 14.1]; p = 0.022) per year. Conclusion: Over three decades, PMS trial populations changed and are now older, with a longer disease duration and more disability, with lower on-trial progression rates.