Background: Relapsing-remitting multiple sclerosis (RRMS) patients with high disease activity (HDA) experience more severe disease than those without HDA. This analysis describes the efficacy of cladribine tablets 3.5 mg/kg in HDA patient subgroups that were either treated with disease-modifying drugs (DMDs) prior to study entry or were treatment naïve.
Methods: Post hoc analysis of the 96 week Cladribine Tablets Treating Multiple Sclerosis Orally (CLARITY) study compared cladribine tablets 3.5 mg/kg to placebo in subgroups of patients meeting the high relapse activity plus disease activity on treatment definition of HDA. Patients were categorized into either prior DMD treatment or DMD treatment-naïve subgroups. Endpoints included annualized relapse rate (ARR), time to first relapse, time to disability progression and magnetic resonance imaging (MRI) outcomes. No inferential statistical analyses were conducted between subgroups.
Results: The DMD-naïve cohort (n = 187) was larger than the prior-DMD cohort (n = 102). In both the DMD-naïve and prior-DMD cohorts, cladribine tablets were associated with a reduction in ARR (rate ratio [RR]: 0.26; 95% confidence interval [CI]: 0.16-0.42; p < .0001 and RR: 0.55; 95% CI: 0.32-0.95; p = .0324, respectively). In both subgroups, cladribine tablets increased the time to relapse versus placebo (hazard ratio [HR]: 0.36; 95% CI: 0.21-0.62; p = .0002 for DMD-naïve cohort and HR: 0.50; 95% CI: 0.24-1.02; p = .0557 for prior-DMD cohort). Significant differences were observed for all assessed disability and MRI outcomes independently of previous treatment.
Conclusion: Post hoc evidence suggests consistent treatment benefits of cladribine tablets 3.5 mg/kg during the 96 week CLARITY study among HDA-RRMS patients who were either previously treated with DMDs or were treatment naïve.
Keywords: CLARITY; Relapsing multiple sclerosis; cladribine tablets; disease-modifying drug treatment; efficacy; high disease activity.