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Prevention of the anti-factor VIII memory B-cell response by inhibition of the Bruton's tyrosine kinase in experimental hemophilia A
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Edité par CCSD ; Ferrata Storti Foundation -
International audience. Hemophilia A is a rare hemorrhagic disorder due to the lack of functional pro-coagulant factor VIII. Factor VIII replacement therapy in patients with severe hemophilia A results in the development of inhibitory anti-factor VIII IgG in up to 30% of the cases. To date, immune tolerance induction upon daily injection of large amounts of factor VIII is the only strategy to eradicate factor VIII inhibitors. It is however efficient in only 60-80% of the patients. Here, we investigated whether blocking B-cell receptor signaling upon inhibition of the Bruton's tyrosine kinase prevents anti-factor VIII immune responses in a mouse model of severe hemophilia A. Naive and factor VIII-sensitized factor VIII-deficient mice were fed with the selective inhibitor of the Bruton's tyrosine kinase, (R)-5-amino-1-(1-cyanopiperidin-3-yl)-3-(4-[2,4-difluorophenoxyl] phenyl)-1H pyrazole-4-carboxamide (PF-06250112), to inhibit B-cell receptor signaling prior to challenge with exogenous factor VIII. The consequences on the anti-factor VIII immune response were studied. Inhibition of the Bruton's tyrosine kinase during the primary anti-factor VIII immune response in naïve mice did not prevent the development of inhibitory anti-factor VIII IgG. In contrast, the anti-factor VIII memory B-cell response was consistently reduced upon treatment of factor VIII-challenged mice with the Bruton's tyrosine kinase inhibitor. The Brutonvs tyrosine kinase inhibitor reduced the differentiation of memory B cells ex vivo and in vivo following adoptively-transferred to naïve animals. Taken together, our data identify inhibition of the Bruton's tyrosine kinase using PF-06250112 as a strategy to limit the reactivation of factor VIII-specific memory B cells upon re-challenge with therapeutic factor VIII.
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