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 persons with MS (PwMS) with relapsing MS (RMS). AntiCD20 (aCD20) and Natalizumab (NTZ) are the two most used MS drugs in Sweden. The effects of switching from these drugs to CladT needs further investigations to understand the impact on the clinical effectiveness of such a switch.

CladT is included in the Swedish post-market surveillance study “Immunomodulation and Multiple Sclerosis Epidemiology 10” (IMSE 10).

Objectives/Aims: To assess the effectiveness of CladT with focus on PwMS treated with NTZ or aCD20 prior to CladT.

Methods: The cohort was divided into 3 groups based on treatment prior to CladT; NTZ, aCD20 and other. Data on Extended Disability Status Scale (EDSS), relapses and lesions were collected from the Swedish Neuro Registry. Wilcoxon Signed Rank Test and the McNemar’s statistical tests were used.

Results: A total of 459 CladT exposed PwMS have been included in IMSE 10. 82 PwMS were treated with NTZ prior to CladT and 87 with aCD20. The remaining 290 PwMS defined as other included 142 treatment naïve, 48 with dimethyl fumarate and 23 with missing data on prior treatment.

Mean EDSS values did not change significantly for the three groups over the 3-year follow-up period.

The ARR decreased significantly from 1 year prior to TS compared to the first and third year with CladT for all three groups (NTZ: 0.26 to 0.03 (yr1)/0.03(yr2)/0(yr3), aCD20: 0.16 to 0.05(yr1)/0.08(yr3), other: 0.38 to 0.08(yr1)/0.03(yr2)/0.01(yr3)). However, the aCD20 group had a significantly lower ARR the year prior to TS than the other two groups resulting in a non-significant decrease during the second follow-up year. The remaining two groups had significant decreases in ARR all three years.

The proportion of PwMS with new T2 lesions during CladT treatment dropped from 12% the first treatment year to 3% the following two years. This decrease was greater for PwMS previously treated with NTZ or other than aCD20. However, none of these differences were significant.

Conclusion: CladT was generally effective for the cohort as a whole. When the cohort was divided by previous treatment data showed greater improvements for PwMS previously treated with NTZ or other than aCD20. However, it is important to note that patients switching from aCD20 had a different profile with a higher initial EDSS level, lower ARR and fewer lesions than the remaining two groups.