clinicaltrials.gov identifier: NCT00753792.

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Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) that results in signi cant neurodegeneration in the majority of those affected and is a common cause of chronic neurological disability in young adults. To provide insight into the mechanisms determining progression, we conducted a genome-wide association study of the age-related MS severity score in 12,584 cases and replicated our ndings in a further 9,805 cases. We identi ed a signi cant association with rs10191329 in the DYSF-ZNF638 locus (P=3.6×10-9), the risk allele shortening the median time to require a walking aid by up to 3.7 years. We also identi ed suggestive association with rs149097173 in the DNM3-PIGC locus (P=2.3×10-7) and signi cant enrichment for expression in CNS tissues. Mendelian randomization analyses indicated a protective role for higher educational attainment. In contrast to immune-driven susceptibility, these ndings indicate a key role of CNS resilience and neurocognitive reserve in determining outcome in MS.

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Background and ObjectivesCladribine tablets cause a reduction in lymphocytes with a predominant effect on B-cell and T-cell counts. The MAGNIFY-MS substudy reports the dynamic changes on multiple peripheral blood mononuclear cell (PBMC) subtypes and immunoglobulin (Ig) levels over 12 months after the first course of cladribine tablets in patients with highly active relapsing multiple sclerosis (MS).MethodsImmunophenotyping was performed at baseline (predose) and at the end of months 1, 2, 3, 6, and 12 after initiating treatment with cladribine tablets. Assessments included lymphocyte subtype counts of CD19+B cells, CD4+and CD8+T cells, CD16+natural killer cells, plasmablasts, and Igs. Immune cell subtypes were analyzed by flow cytometry, and serum IgG and IgM were analyzed by nephelometric assay. Absolute cell counts and percentage change from baseline were assessed.ResultsThe full analysis set included 57 patients. Rapid reductions in median CD19+, CD20+, memory, activated, and naive B-cell counts were detected, reaching nadir by month 2. Thereafter, total CD19+, CD20+, and naive B-cell counts subsequently reconstituted, but memory B cells remained reduced by 93%–87% for the remainder of the study. The decrease in plasmablasts was slower, reaching nadir at month 3. Decrease in T-cell subtypes was also slower and more moderate compared with B-cell subtypes, reaching nadir between months 3 and 6. IgG and IgM levels remained within the normal range over the 12-month study period.DiscussionCladribine tablets induce a specific pattern of early and sustained PBMC subtype dynamics in the absence of relevant Ig changes: While total B cells were reduced dramatically, T cells were affected significantly less. Naive B cells recovered toward baseline, naive CD4 and CD8 T cells did not, and memory B cells remained reduced. The results help to explain the unique immune depletion and repopulation architecture regarding onset of action and durability of effects of cladribine tablets while largely maintaining immune competence.Trial Registration InformationClinicalTrials.govIdentifier:NCT03364036. Date registered: December 06, 2017.