RN486

RN486 is a reversible inhibitor of Btk with IC50 value of 4.0 nM [1].
Bruton's tyrosine kinase (Btk) is a type of kinase protein which is expressed by immune system-related cells (B-lymphocyte, monocytes, macrophages, neutrophils and mast cells) and plays a pivotal role in cell differentiation and proliferation at the transition from pre-B to later B cell stages as well as in the process of both BCR and FcR signaling [2]. It has been reported that aberrant BCR signaling is associated with autoimmune diseases, for example, rheumatoid arthritis (RA) [3].
RN486 is a selective Btk inhibitor. When tested with human Ramos B cells or whole blood, RN486 treatment reduced the expression of CD69/B cells proliferation and IgG production by blocking BCR and FcR Signaling [1].
In NZB × NZW mouse model with systemic lupus erythematosus (SLE), compared with control group, RN486 treatment completely stopped disease progression by inhibiting BTK signaling and targeting other autoantibody-producing and effector cells [4]. In a PCA (type I hypersensitivity) mouse model or rPCA (type III hypersensitivity) mouse model, RN486 treatment significantly inhibited inflammatory response. In mouse model of RA, administration of RN486 orally could reduce both paw swelling and inflammatory markers in the blood by inhibiting both joint and systemic inflammation alone or in combination with methotrexate [1].
RN486 may also play a pivotal role in reducing immune complex-mediated activation of human monocytes and down-regulating the expression of macrophage-related and interferon-inducible genes [4].
References:
[1].    Xu, D., et al., RN486, a selective Bruton's tyrosine kinase inhibitor, abrogates immune hypersensitivity responses and arthritis in rodents. J Pharmacol Exp Ther, 2012. 341(1): p. 90-103.
[2].    Kil, L.P., et al., Btk levels set the threshold for B-cell activation and negative selection of autoreactive B cells in mice. Blood, 2012. 119(16): p. 3744-56.
[3].    Hartkamp, L.M., et al., Btk inhibition suppresses agonist-induced human macrophage activation and inflammatory gene expression in RA synovial tissue explants. Ann Rheum Dis, 2014.
[4].    Mina-Osorio, P., et al., Suppression of glomerulonephritis in lupus-prone NZB x NZW mice by RN486, a selective inhibitor of Bruton's tyrosine kinase. Arthritis Rheum, 2013. 65(9): p. 2380-91.

RN486, a selective Bruton's tyrosine kinase inhibitor, abrogates immune hypersensitivity responses and arthritis in rodents.[Pubmed:22228807]

J Pharmacol Exp Ther. 2012 Apr;341(1):90-103.

Genetic mutation and pharmacological inhibition of Bruton's tyrosine kinase (Btk) both have been shown to prevent the development of collagen-induced arthritis (CIA) in mice, providing a rationale for the development of Btk inhibitors for treating rheumatoid arthritis (RA). In the present study, we characterized a novel Btk inhibitor, 6-cyclopropyl-8-fluoro-2-(2-hydroxymethyl-3-{1-methyl-5-[5-(4-methyl-piperazin-1- yl)-pyridin-2-ylamino]-6-oxo-1,6-dihydro-pyridin-3-yl}-phenyl)-2H-isoquinolin-1-o ne (RN486), in vitro and in rodent models of immune hypersensitivity and arthritis. We demonstrated that RN486 not only potently and selectively inhibited the Btk enzyme, but also displayed functional activities in human cell-based assays in multiple cell types, blocking Fcepsilon receptor cross-linking-induced degranulation in mast cells (IC(50) = 2.9 nM), Fcgamma receptor engagement-mediated tumor necrosis factor alpha production in monocytes (IC(50) = 7.0 nM), and B cell antigen receptor-induced expression of an activation marker, CD69, in B cells in whole blood (IC(50) = 21.0 nM). RN486 displayed similar functional activities in rodent models, effectively preventing type I and type III hypersensitivity responses. More importantly, RN486 produced robust anti-inflammatory and bone-protective effects in mouse CIA and rat adjuvant-induced arthritis (AIA) models. In the AIA model, RN486 inhibited both joint and systemic inflammation either alone or in combination with methotrexate, reducing both paw swelling and inflammatory markers in the blood. Together, our findings not only demonstrate that Btk plays an essential and conserved role in regulating immunoreceptor-mediated immune responses in both humans and rodents, but also provide evidence and mechanistic insights to support the development of selective Btk inhibitors as small-molecule disease-modifying drugs for RA and potentially other autoimmune diseases.

Suppression of glomerulonephritis in lupus-prone NZB x NZW mice by RN486, a selective inhibitor of Bruton's tyrosine kinase.[Pubmed:23754328]

Arthritis Rheum. 2013 Sep;65(9):2380-91.

OBJECTIVE: Bruton's tyrosine kinase (BTK) plays a critical role in B cell development and function. We recently described a selective BTK inhibitor, RN486, that blocks B cell receptor (BCR) and Fcgamma receptor signaling and is efficacious in animal models of arthritis. The aim of this study was to examine the potential efficacy of BTK in systemic lupus erythematosus (SLE), using an NZB x NZW mouse model of spontaneous SLE. METHODS: Mice received RN486 or its vehicle (administered in chow) at a final concentration of 30 mg/kg for 8 weeks, starting at 32 weeks of age. RESULTS: The administration of RN486 completely stopped disease progression, as determined by histologic and functional analyses of glomerular nephritis. The efficacy was associated with striking inhibition of B cell activation, as demonstrated by a significant reduction in CD69 expression in response to BCR crosslinking. RN486 markedly reduced the secretion of IgG anti-double-stranded DNA (anti-dsDNA) secretion, as determined by enzyme-linked immunosorbent and enzyme-linked immunospot assays. Flow cytometric analysis demonstrated depletion of CD138(high) B220(low) plasma cells in the spleen. RN486 inhibited secretion of IgG anti-dsDNA but not IgM anti-dsDNA, suggesting that pharmacologic blockade of BTK resembles the reported transgenic expression of low levels of endogenous BTK in B cells. In addition, RN486 may also impact the effector function of autoantibodies, as evidenced by a significant reduction in immune complex-mediated activation of human monocytes in vitro and down-regulation of the expression of macrophage-related and interferon-inducible genes in both the kidneys and spleens of treated mice. CONCLUSION: Collectively, our data suggest that BTK inhibitors may simultaneously target autoantibody-producing and effector cells in SLE, thus constituting a promising therapeutic alternative for this disease.

Structure-based drug design of RN486, a potent and selective Bruton's tyrosine kinase (BTK) inhibitor, for the treatment of rheumatoid arthritis.[Pubmed:24712864]

J Med Chem. 2015 Jan 8;58(1):512-6.

Structure-based drug design was used to guide the optimization of a series of selective BTK inhibitors as potential treatments for Rheumatoid arthritis. Highlights include the introduction of a benzyl alcohol group and a fluorine substitution, each of which resulted in over 10-fold increase in activity. Concurrent optimization of drug-like properties led to compound 1 (RN486) ( J. Pharmacol. Exp. Ther. 2012 , 341 , 90 ), which was selected for advanced preclinical characterization based on its favorable properties.