Cladribine tablets for relapsing-remitting multiple sclerosis: Efficacy across patient subgroups from the phase III CLARITY study

Background: In the phase III CLARITY study, treatment with cladribine tablets at cumulative doses of 3.5 or 5.25 mg/kg over 96 weeks led to significant reductions in annualized relapse rates (ARR) versus placebo in patients with relapsing-remitting multiple sclerosis. Further post hoc analyses of CLARITY study data were conducted to determine the efficacy of cladribine tablets across patient subgroups stratified by baseline characteristics. Methods: Relapse rates over the 96-week CLARITY study were analyzed in cohorts stratified by demographics; disease duration; treatment history and disease activity at baseline. Results: In the intent-to-treat population (n=437, 433 and 456 in the placebo, cladribine 3.5 and 5.25 mg/kg groups, respectively), treatment with cladribine tablets 3.5 and 5.25 mg/kg led to consistent improvements in ARR versus placebo in patients stratified by gender; age ( ≤ 40/ > 40 years); disease duration ( <3/3-10/ > 10 years); prior disease-modifying drug treatment (treated/naive); relapses in the prior year ( ≤ 1/2/ > 3); Expanded Disability Status Scale score ( <3.5/ > 3.5); T1 gadolinium- enhancing lesions (presence, absence); and T2 lesion volume ( ≤ median/ > median) at baseline (all Pr 0.05 for reduction in the relative risk of relapse [cladribine tablets versus placebo]). Significant effects were also observed in patients who had only one relapse in the year prior to study entry (n=306, 303 and 323 in the placebo, cladribine 3.5 and 5.25 mg/kg groups, respectively) and who were further stratified according to other measures of disease activity at baseline. Conclusions: Treatment with cladribine tablets provides consistent reductions in ARR compared with placebo across the spectrum of baseline demographics and disease characteristics represented in the CLARITY study.