Cladribine tablets added to IFN-β in active relapsing MS: The ONWARD study.

Objective: To evaluate the safety and efficacy of cladribine tablets in patients still experiencing active relapsing MS despite interferon (IFN)-β treatment.

Methods: A 96-week phase II study, randomizing patients treated with IFN-β to cladribine tablets 3.5 mg/kg/IFN-β or placebo/IFN-β. Patients were to receive cladribine tablets 3.5 mg/kg/IFN-β or placebo/IFN-β in a 2:1 ratio (n = 172) with safety and exploratory efficacy outcomes being assessed.

Results: Adverse events (AEs) and serious AEs were similar across treatment groups, except lymphopenia. Fifty of 124 (40.3%) cladribine/IFN-β recipients vs 0% of placebo/IFN-β recipients reported lymphopenia as an AE, with grade 3/4 lymphopenia (laboratory lymphocyte count < 500 cells/mm3 ) experienced by 79/124 (63.7%) vs 1 (2.1%), respectively. Patients treated with cladribine tablets 3.5 mg/kg/IFN-β were 63% less likely to have a qualifying relapse than placebo/IFN-β recipients, and cladribine tablets 3.5 mg/kg/IFN-β reduced most MRI measures of disease activity.

Conclusions: In patients with active relapsing MS despite IFN-β treatment, cladribine tablets 3.5 mg/kg/IFN-β reduced relapses and MRI lesion activity over 96 weeks compared with placebo/IFN-β but led to an increased incidence of lymphopenia.

Classification of evidence: This study provides Class I evidence that for patients with active relapsing MS despite IFN-β treatment, cladribine tablets added to IFN-β reduced relapses and MRI lesion activity over 96 weeks and increased the incidence of lymphopenia.

Clinical trial registration: NCT00436826.