Abstract Details

Title Inhibition of Bruton’s Tyrosine Kinase Selectively Prevents Antigen-Activation of B cells and Ameliorates B-Cell-Mediated Experimental Autoimmune Encephalomyelitis

Topic Multiple Sclerosis

Presentation(s) P2 - Poster Session 2 (5:30 PM-6:30 PM)

Poster/Presentation
Number 15-063

Objective Evaluation of Bruton´s tyrosine kinase inhibitor (BTKi) evobrutinib (M2951) in a mouse model of experimental autoimmune encephalomyelitis (EAE).

Background B cells are key mediators of inflammatory processes in multiple sclerosis, a notion substantiated by the success of pan B-cell depletion by anti-CD20 monoclonal antibodies; however, these can affect regulatory B-cell properties, as well as targeting pathogenic B cells. BTK is centrally involved in B-cell receptor (BCR) signaling, and subsequent B-cell activation and differentiation. BTKi could therefore control pathogenic functions such as antigen presentation and cytokine release, without affecting regulatory B-cell properties.

Design/Methods C57Bl/6 mice received daily oral evobrutinib 1, 3 or 10mg/kg, or vehicle from 7 days prior to immunization with conformational MOG 1-117 protein (a B-cell-mediated model of EAE). EAE severity was assessed daily using a standard scale (0–5). Histopathology was performed at Day 60. Flow cytometry of activation markers on B cells, T cells and myeloid cells, and analysis of B-cell phenotype was performed at Day 12. Intra-cellular calcium flux analysis was performed in vitro, or after 3 days of BTKi treatment ex vivo, using Fluo-3 and Fura Red dyes and anti-IgM BCR stimulation.

Results Intermediate and highest doses (3 and 10mg/kg) of BTKi showed an amelioration of EAE severity throughout the 60-day observation period. BTKi reduced CNS inflammation and demyelination, and led to an accumulation of naïve B cells, with a corresponding reduction of antigen-activated B cells. Expression of activation markers CD80, CD86, CD69 and MHCII on B cells was significantly reduced. BCR stimulation led to reduced calcium influx in BTKi-treated B cells in vitro and ex vivo.

Conclusions BTKi reduced excitatory calcium influx in B cells upon BCR stimulation, preventing their activation and conversion from naïve to antigen-activated B cells. This translates into reduced CNS inflammation and clinical amelioration in a B-cell-mediated EAE model.

Authors/Disclosures
PRESENTER	No disclosure on file
Roland Grenningloh	Roland Grenningloh has received personal compensation for serving as an employee of EMD Serono.
Wolfgang Brueck, PhD (Zentrum Pathologie)	Dr. Brueck has nothing to disclose.
	No disclosure on file
	No disclosure on file

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