Specific Btk inhibition suppresses B cell- and myeloid cell-mediated arthritis.
ABSTRACT Bruton's tyrosine kinase (Btk) is a therapeutic target for rheumatoid arthritis, but the cellular and molecular mechanisms by which Btk mediates inflammation are poorly understood. Here we describe the discovery of CGI1746, a small-molecule Btk inhibitor chemotype with a new binding mode that stabilizes an inactive nonphosphorylated enzyme conformation. CGI1746 has exquisite selectivity for Btk and inhibits both auto- and transphosphorylation steps necessary for enzyme activation. Using CGI1746, we demonstrate that Btk regulates inflammatory arthritis by two distinct mechanisms. CGI1746 blocks B cell receptor-dependent B cell proliferation and in prophylactic regimens reduces autoantibody levels in collagen-induced arthritis. In macrophages, Btk inhibition abolishes FcγRIII-induced TNFα, IL-1β and IL-6 production. Accordingly, in myeloid- and FcγR-dependent autoantibody-induced arthritis, CGI1746 decreases cytokine levels within joints and ameliorates disease. These results provide new understanding of the function of Btk in both B cell- or myeloid cell-driven disease processes and provide a compelling rationale for targeting Btk in rheumatoid arthritis.
- SourceAvailable from: Martin JS Dyer[Show abstract] [Hide abstract]
ABSTRACT: Although expressed in several haematological lineages and involved in multiple different signalling pathways, Bruton tyrosine kinase (BTK) plays an indispensible role in B cells in signalling from the B cell receptor (BCR) for antigen. Many B cell malignancies remain dependent on constitutive BCR signalling, making BTK a functional therapeutic target. Several BTK inhibitors (BTKi) with different kinomes and modes of action are being assessed clinically. This review documents the efficacy and toxicity of BTKi in chronic lymphocytic leukaemia (CLL). Clinically, the furthest in development is ibrutinib (trade name, Imbruvica), an irreversible BTKi, which has shown spectacular preliminary efficacy, with rapid reductions in lymph nodes accompanied by peripheral blood lymphocytosis. The lymphocytosis resolves slowly and most patients do not enter a complete remission. Nevertheless, it is possible to maintain many CLL patients, even those with adverse cytogenetic features, on drug for many months with minimal toxicities, thus potentially transforming the therapeutic paradigms for CLL. The efficacy, lack of toxicity and oral administration of BTKi will ensure their adoption in a wide range of B cell malignancies. An outstanding challenge is to incorporate BTKi with other precision medicines in a mechanism-based manner in order to dispense with conventional chemotherapy.British Journal of Haematology 04/2014; · 4.94 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The role of the Bruton tyrosine kinase (Btk) protein in neutrophil function has been evaluated using neutrophils from healthy volunteers after incubation with a Btk inhibitor, leflunomide metabolite analog (LFM-A13), suggesting an important role for Btk in neutrophil function. We sought to determine the role of Btk protein on neutrophil superoxide generation and chemotaxis stimulated by N-formyl-methionine-leucine-phenylalanine (fMLP). Chemotaxis was assayed on agarose gel and superoxide generation by cytochrome C reduction. The affects of LFM-A13 on chemotaxis and superoxide generation in unstimulated and fMLP stimulated neutrophils were studied in Btk deficient neutrophils from XLA patients compared with matched controls analyzed simultaneously. Chemotaxis and stimulated superoxide production were similar in the normal and Btk deficient neutrophils and were similarly inhibited by LFM-A13. In one patient, LFMA13 had no effect on superoxide generation in Btk deficient neutrophils up to a concentration of 25 microM, while inhibited superoxide production by control neutrophils. Our results suggest that Btk does not have a specific role in neutrophil fMLP-stimulated superoxide generation and chemotaxis since these activities were similarly inhibited by LFM-A13 in Btk deficient and normal neutrophils. The lack of superoxide generation following Btk inhibition by LFM-A13 in Btk deficient neutrophils from one patient may suggest some heterogeneity in the role of Btk in fMLP induced neutrophil superoxide generation.Journal of Clinical Immunology 04/2014; · 2.65 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: B cells mediate multiple functions that influence immune and inflammatory responses in rheumatoid arthritis. Production of a diverse array of autoantibodies can happen at different stages of the disease, and are important markers of disease outcome. In turn, the magnitude and quality of acquired humoral immune responses is strongly dependent on signals delivered by innate immune cells. Additionally, the milieu of cells and chemokines that constitute a niche for plasma cells rely strongly on signals provided by stromal cells at different anatomical locations and times. The chronic inflammatory state therefore importantly impacts the developing humoral immune response and its intensity and specificity. We focus this review on B cell biology and the role of the innate immune system in the development of autoimmunity in patients with rheumatoid arthritis.Expert Review of Clinical Immunology 04/2014; · 3.34 Impact Factor