To Örebro University

Introduction: Cladribine is a deoxyadenosine analogue prodrug targeting proliferating B- and T-lymphocytes. Cladribine tablets (CladT) are administered in two courses, 12 months apart, for patients with remitting multiple sclerosis (RMS). CladT is included in the Swedish post-market surveillance study “Immunomodulation and Multiple Sclerosis Epidemiology substudy 10” (IMSE 10).

Objectives/Aims: To assess effectiveness of CladT with focus on age at treatment start. Two subgroups in the IMSE 10 study will be compared, below <45 or above ⩾ 45 years of age at treatment start.

Methods: Data on Extended Disability Status Scale (EDSS), Multiple Sclerosis Severity Scale (MSSS), Symbol Digit Modalities Test (SDMT), Multiple Sclerosis Impact Scale (MSIS-29), European Quality of Life -5 Dimensions Test (EQ-5D), Visual Analog Scale (VAS) scores, and relapses and Adverse Events (AEs) were collected from the nationwide Swedish Neuro Registry (NeuroReg). Effectiveness measures and relapse rates were assessed using Wilcoxon Signed Rank Test.

Results: By September 2023, a total of 313 CladT exposed Persons with MS (PwMS) have been included in IMSE 10 since the launch of CladT in April 2018. This cohort was divided into two subgroups, Below <45 (n=233) and Above ⩾45 (n=80) years of age at treatment start. The mean age was 33 and 51 years in the two subgroups, respectively.There were a higher proportion of SPMS (13%) in the older subgroup compared to the younger subgroup (1 %). The proportion of PwMS that discontinued their treatments was twice as high in the younger subgroup (13%) and the main cause of discontinuation was “Lack of effect” (81%) whereas for the older subgroup “other reasons” (40%) was the main cause of discontinuation.Both subgroups demonstrated clinical stability in mean EDSS that was kept stable during the first two treatment years. For both subgroups the mean annual relapse rate (ARR) decreased significantly (p<0.05) during the first two treatment years compare to the ARR one-year prior to cladribine treatment start. During the first year of treatment 5.7% of PwMS in the younger subgroup had new T2 lesions compared to 2.2% in the older subgroup (non-significant). During the second treatment year, 2.1 % of PwMS in the younger subgroup and, 0% of PwMS in the older subgroup had new T2 lesions (non-significant).

Conclusion: This data shows that PwMS below and above 45 years at treatment start exposed to CladT display clinical stability and a tendency for improvement compared with baseline in several of the investigated outcomes. The subgroup of PwMS with a treatment start above 45 years showed a tendency for less MRI activity compared to the subgroup below 45.