CGI-1746

CGI-1746 is a selective and potent inhibitor of Bruton's tyrosine kinase (BTK) with IC50 value of 1.9 nM [1][2].
Bruton’s tyrosine kinase (BTK) is a member of the Tec tyrosine kinase family and plays an important role in differentiation, proliferation and development of B cells. It is an attractive target for the treatment of immunological disorders such as B-cell malignancies, rheumatoid arthritis (RA), multiple sclerosis (MS) and lupus [3].
CGI-1746 potently inhibits both auto- and transphosphorylation of BTK. It binds to un-phosphorylated BTK and stabilizes it in an inactive enzyme state. In cellular assays, CGI-1746 blocks BCR-mediated B-cell proliferation and suppresses the production of IL-6, IL-1βand TNF in macrophages [1].
In experimental mouse models, CGI-1746 shows a robust anti-arthritic activity [1]. In B10.RIII mice model, CGI1746 resulted in a significant inhibition (97%) of clinical arthritis scores, which were better than dexamethasone treatment (56% inhibition) [2].
References:
[1]. Akinleye A, Chen Y, Mukhi N, et al. Ibrutinib and novel BTK inhibitors in clinical development. J Hematol Oncol, 2013, 6: 59.
[2]. Di Paolo JA, Huang T, Balazs M, et al. Specific Btk inhibition suppresses B cell- and myeloid cell-mediated arthritis. Nat Chem Biol, 2011, 7(1): 41-50.
[3]. Young WB, Barbosa J, Blomgren P, et al. Potent and selective Bruton's tyrosine kinase inhibitors: discovery of GDC-0834. Bioorg Med Chem Lett, 2015, 25(6): 1333-1337.

BTK suppresses myeloma cellular senescence through activating AKT/P27/Rb signaling.[Pubmed:28915637]

Oncotarget. 2017 May 23;8(34):56858-56867.

We previously explored the role of BTK in maintaining multiple myeloma stem cells (MMSCs) self-renewal and drug-resistance. Here we investigated the elevation of BTK suppressing MM cellular senescence, a state of irreversible cellular growth arrest. We firstly discovered that an increased expression of BTK in MM samples compared to normal controls by immunohistochemistry (IHC), and significant chromosomal gain in primary samples. In addition, BTK high-expressing MM patients are associated with poor outcome in both Total Therapy 2 (TT2) and TT3 cohorts. Knockdown BTK expression by shRNA induced MM cellular senescence using beta-galactosidase (SA-b-gal) staining, cell growth arrest by cell cycle staining and decreased clonogenicity while forcing BTK expression in MM cells abrogated these characteristics. We also validated this feature in mouse embryonic fibroblast cells (MEFs), which showed that elevated BTK expression was resistant to MEF senescence after serial cultivation in vitro. Further mechanism study revealed that BTK activated AKT signaling leading to down-regulation of P27 expression and hindered RB activity while AKT inhibitor, LY294002, overcame BTK-overexpression induced cellular senescence resistance. Eventually we demonstrated that BTK inhibitor, CGI-1746, induced MM cellular senescence, colony reduction and tumorigenecity inhibition in vivo. Summarily, we designate a novel mechanism of BTK in mediating MM growth, and BTK inhibitor is of great potential in vivo and in vitro suggesting BTK is a promising therapeutic target for MM.

Bruton's tyrosine kinase is a potential therapeutic target in prostate cancer.[Pubmed:26383180]

Cancer Biol Ther. 2015;16(11):1604-15.

Bruton's tyrosine kinase (BTK) is a non-receptor tyrosine kinase that has mainly been studied in haematopoietic cells. We have investigated whether BTK is a potential therapeutic target in prostate cancer. We find that BTK is expressed in prostate cells, with the alternate BTK-C isoform predominantly expressed in prostate cancer cells and tumors. This isoform is transcribed from an alternative promoter and results in a protein with an amino-terminal extension. Prostate cancer cell lines and prostate tumors express more BTK-C transcript than the malignant NAMALWA B-cell line or human lymphomas. BTK protein expression is also observed in tumor tissue from prostate cancer patients. Down regulation of this protein with RNAi or inhibition with BTK-specific inhibitors, Ibrutinib, AVL-292 or CGI-1746 decrease cell survival and induce apoptosis in prostate cancer cells. Microarray results show that inhibiting BTK under these conditions increases expression of apoptosis related genes, while overexpression of BTK-C is associated with elevated expression of genes with functions related to cell adhesion, cytoskeletal structure and the extracellular matrix. These results are consistent with studies that show that BTK signaling is important for adhesion and migration of B cells and suggest that BTK-C may confer similar properties to prostate cancer cells. Since BTK-C is a survival factor for these cells, it represents both a potential biomarker and novel therapeutic target for prostate cancer.

Bruton's Tyrosine Kinase Inhibitors Prevent Therapeutic Escape in Breast Cancer Cells.[Pubmed:27256378]

Mol Cancer Ther. 2016 Sep;15(9):2198-208.

We have reported that a novel isoform of BTK (BTK-C) expressed in breast cancer protects these cells from apoptosis. In this study, we show that recently developed inhibitors of BTK, such as ibrutinib (PCI-32765), AVL-292, and CGI-1746, reduce breast cancer cell survival and prevent drug-resistant clones from arising. Ibrutinib treatment impacts HER2(+) breast cancer cell viability at lower concentrations than the established breast cancer therapeutic lapatinib. In addition to inhibiting BTK, ibrutinib, but not AVL-292 and CGI-1746, efficiently blocks the activation of EGFR, HER2, ErbB3, and ErbB4. Consequently, the activation of AKT and ERK signaling pathways are also blocked leading to a G1-S cell-cycle delay and increased apoptosis. Importantly, inhibition of BTK prevents activation of the AKT signaling pathway by NRG or EGF that has been shown to promote growth factor-driven lapatinib resistance in HER2(+) breast cancer cells. HER2(+) breast cancer cell proliferation is blocked by ibrutinib even in the presence of these factors. AVL-292, which has no effect on EGFR family activation, prevents NRG- and EGF-dependent growth factor-driven resistance to lapatinib in HER2(+) breast cancer cells. In vivo, ibrutinib inhibits HER2(+) xenograft tumor growth. Consistent with this, immunofluorescence analysis of xenograft tumors shows that ibrutinib reduces the phosphorylation of HER2, BTK, Akt, and Erk and histone H3 and increases cleaved caspase-3 signals. As BTK-C and HER2 are often coexpressed in human breast cancers, these observations indicate that BTK-C is a potential therapeutic target and that ibrutinib could be an effective drug especially for HER2(+) breast cancer. Mol Cancer Ther; 15(9); 2198-208. (c)2016 AACR.

The NLRP3 inflammasome and bruton's tyrosine kinase in platelets co-regulate platelet activation, aggregation, and in vitro thrombus formation.[Pubmed:28034752]

Biochem Biophys Res Commun. 2017 Jan 29;483(1):230-236.

Cleavage of interleukin-1beta (IL-1beta) is a key inflammatory event in immune cells and platelets, which is mediated by nucleotide-binding domain leucine rich repeat containing protein (NLRP3)-dependent activation of caspase-1. In immune cells, NLRP3 and caspase-1 form inflammasome complexes with the adaptor proteins apoptosis-associated speck-like protein containing a CARD (ASC) and bruton's tyrosine kinase (BTK). In platelets, however, the regulatory triggers and the functional effects of the NLRP3 inflammasome are unknown. Here, we show in vitro that the platelet NLRP3 inflammasome contributes to platelet activation, aggregation, and thrombus formation. NLRP3 activity, as monitored by caspase-1 activation and cleavage and secretion of IL-1beta, was upregulated in activated platelets, which was dependent on platelet BTK. Pharmacological inhibition or genetic ablation of BTK in platelets led to decreased platelet activation, aggregation, and in vitro thrombus formation. We identify a functionally relevant link between BTK and NLRP3 in platelets, with potential implications in disease states associated with abnormal coagulation and inflammation.