Article Text
Abstract
Background The CLARITY study demonstrated the benefit of cladribine tablets 3.5 mg/kg (CT3.5) for patients with relapsing MS (RMS). Patients with high disease activity (HDA) RMS are at risk of clinical activity and disability progression.
Objective Post-hoc analysis of MRI outcomes in CLARITY for CT3.5 vs placebo.
Methods Retrospective analysis using HDA definitions based on relapse history, prior treatment, and MRI characteristics: high relapse activity (HRA) and HRA plus disease activity on treatment (HRA+DAT).
Results For cumulative new T1 Gd+ lesions, relative risk ratios (RRR) for both subgroups (HRA: 0.087; 95% CI: 0.052 to 0.144; p<0.0001) (HRA+DAT: 0.077; 95% CI: 0.046 to 0.128; p<0.0001) were lower for CT3.5 vs placebo. Risk reductions (RR) (91% and 92%, respectively) were similar to the 90% reduction in the overall CLARITY population (0.097; 95% CI: 0.070 to 0.134; p<0.0001). Cumulative active T2 lesions RRR favoured CT3.5 vs placebo for both subgroups (HRA: 0.263; 95% CI: 0.180 to 0.383, p<0.0001) (HRA+DAT: 0.254; 95% CI: 0.178 to 0.363; p<0.0001): RRs of 74% and 75%, reflecting the 73% overall population reduction (0.272; 95% CI: 0.221 to 0.335; p<0.0001). Cumulative combined unique lesions RRR favoured CT3.5 vs placebo for HRA (0.212; 95% CI: 0.145 to 0.311; p<0.0001) and HRA+DAT (0.203; 95% CI: 0.141 to 0.291; p<0.0001): RRs were 79% and 80%, reflecting the 77% overall population reduction (0.234; 95% CI: 0.190 to 0.290; p<0.0001). There were no significant interactions between HDA and non-HDA subgroups.
Conclusions The treatment benefit of CT3.5 on MRI outcomes was similar in HDA RMS subgroups and the overall CLARITY study population.
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