The CLARION study design and status update: a long-term, registry-based study evaluating adverse events of special interest in patients with relapsing multiple sclerosis newly started on cladribine tablets

Objective To describe the design of the CLARION post-approval safety study (EU PAS Register number, EUPAS24484) and provide a status update, including characteristics of patients included up to 1 May 2021. Methods CLARION aims to further evaluate adverse events of special interest in patients who are newly initiating treatment with cladribine tablets for relapsing multiple sclerosis (MS). The study population consists of two cohorts: patients newly initiating cladribine tablets (cladribine cohort) and patients newly initiating oral fingolimod tablets (comparator fingolimod cohort), with an aim to include 8000 patients (4000 patients per cohort). The study relies on secondary use of data from pre-existing MS registries/data sources (except in Germany, where primary data collection is performed). The study is projected to last 15 years, with an anticipated 5-year inclusion period. Study outcomes are: malignancies; severe infections; tuberculosis; progressive multifocal leukoencephalopathy; other opportunistic infections; herpes zoster; severe lymphopenia (Grade >= 3); and treatment discontinuation. Results As of 1 May 2021, 2393 patients were included in CLARION from seven participating MS registries/data sources (cladribine cohort, n = 1266; fingolimod cohort, n = 1127). The majority of patients are female (cladribine cohort, 72.5%; fingolimod cohort, 68.0%), with mean age at onset of MS of 31.5 years for the cladribine cohort and 30.9 years for the fingolimod cohort. The majority of patients in both cohorts had relapsing MS (cladribine cohort, 92.1%; fingolimod cohort, 93.5%). Conclusion By providing further information on adverse events of special interest during long-term follow-up, CLARION will assist neurologists and patients regarding treatment decision-making for management of relapsing MS.