Bruton Tyrosine Kinase Inhibitor Ibrutinib Research Articles

Abstract A274: Novel SYK inhibitors have demonstrated potent antiproliferative effects in both ABC- and GCB-DLBCL cell lines via suppression of multiple pathways downstream of the B-cell receptor.

Abstract Background: Diffuse large B-cell lymphoma (DLBCL) has two major subtypes with distinct biological and clinical characteristics: activated B-cell like (ABC) and germinal center B-cell like (GCB) lymphoma. A Bruton's tyrosine kinase (BTK) inhibitor has shown clinical activity in a subset of ABC-DLBCL patients. Spleen tyrosine kinase (SYK) is an upstream regulator of BTK, but the effect of SYK inhibition versus BTK inhibition in DLBCL has not been elucidated. We developed potent and selective SYK inhibitors and evaluated mechanistic differences between SYK inhibition and BTK inhibition in DLBCL cell lines. Materials and Methods: GCB-DLBCL (Pfeiffer, SU-DHL-10, SU-DHL-6, SU-DHL-5, DOHH2, OCI-LY18, OCI-LY1, VAL) and ABC-DLBCL (OCI-LY10, OCI-LY3, TMD8) cell lines were cultivated under standard cell culture conditions. For the growth inhibition assay, cells were treated with compounds for 72 hr, and the number of living cells was determined by CellTiter-Glo (Promega). Cells were treated with the compounds for 24 hr and lysates were subjected to western blotting with antibodies specific for the components of PI3K, ERK, and NFkB pathways. Results: The selective SYK inhibitors, TAS-5567 and its analogue TAS-4335, inhibited SYK with IC50 values of 0.37 nM and 0.26 nM, respectively. The SYK inhibitors demonstrated antiproliferative activities in a wide range of DLBCL cell lines including both ABC and GCB subtypes (TAS-5567 IC50=298 nM in TMD8, 128 nM in SU-DHL-6, 134 nM in SU-DHL-5, and 68 nM in SU-DHL-10). On the other hand, a BTK inhibitor Ibrutinib exhibited antiproliferative activity only in the ABC subtype (IC50=2 nM in TMD8, 1468 nM in SU-DHL-6, 1240 nM in SU-DHL-5, and 1287 nM in SU-DHL-10). We further analyzed the effect of these inhibitors on BCR signaling in GCB-DLBCL cell lines SU-DHL-6, SU-DHL-5, and SU-DHL-10 and found that the SYK inhibitor but not the BTK inhibitor robustly suppressed the PI3K pathway as detected by phospho-AKT and phospho-PRAS40. In ABC-DLBCL cell line TMD8, which is known to be NFkB pathway dependent, the level of phospho-IkBα was reduced by both the SYK and BTK inhibitors. Conclusion: Our SYK inhibitors demonstrated a broad spectrum of antiproliferative efficacy in both ABC- and GCB-DLBCL cell lines, which may be explained by the blocking of multiple downstream pathways, including PI3K and NFkB signaling. Thus SYK inhibition may be a valuable approach in the treatment of heterogeneous DLBCL. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A274. Citation Format: Aki Kawagishi, Hiroki Irie, Yoshio Ogino, Hideya Komatani, Teruhiro Utsugi. Novel SYK inhibitors have demonstrated potent antiproliferative effects in both ABC- and GCB-DLBCL cell lines via suppression of multiple pathways downstream of the B-cell receptor. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A274.

Egress of CD19+CD5+ cells into peripheral blood following treatment with the Bruton tyrosine kinase inhibitor ibrutinib in mantle cell lymphoma patients

AbstractIbrutinib (PCI-32765) is a highly potent oral Bruton tyrosine kinase (BTK) inhibitor in clinical development for treating B-cell lymphoproliferative diseases. Patients with chronic lymphocytic leukemia (CLL) often show marked, transient increases of circulating CLL cells following ibrutinib treatments, as seen with other inhibitors of the B-cell receptor (BCR) pathway. In a phase 1 study of ibrutinib, we noted similar effects in patients with mantle cell lymphoma (MCL). Here, we characterize the patterns and phenotypes of cells mobilized among patients with MCL and further investigate the mechanism of this effect. Peripheral blood CD19+CD5+ cells from MCL patients were found to have significant reduction in the expression of CXCR4, CD38, and Ki67 after 7 days of treatment. In addition, plasma chemokines such as CCL22, CCL4, and CXCL13 were reduced 40% to 60% after treatment. Mechanistically, ibrutinib inhibited BCR- and chemokine-mediated adhesion and chemotaxis of MCL cell lines and dose-dependently inhibited BCR, stromal cell, and CXCL12/CXCL13 stimulations of pBTK, pPLCγ2, pERK, or pAKT. Importantly, ibrutinib inhibited migration of MCL cells beneath stromal cells in coculture. We propose that BTK is essential for the homing of MCL cells into lymphoid tissues, and its inhibition results in an egress of malignant cells into peripheral blood. This trial was registered at www.clinicaltrials.gov as #NCT00114738.

Akt inhibitor MK2206 selectively targets CLL B‐cell receptor induced cytokines, mobilizes lymphocytes and synergizes with bendamustine to induce CLL apoptosis

<scp>Akt</scp> inhibitor <scp>MK</scp>2206 selectively targets <scp>CLL B</scp>‐cell receptor induced cytokines, mobilizes lymphocytes and synergizes with bendamustine to induce <scp>CLL</scp> apoptosis

Ibrutinib Also Inhibits ITK

Abstract The Bruton tyrosine kinase inhibitor ibrutinib targets interleukin-2 inducible kinase (ITK) in T cells.

Use of tumor genomic profiling to reveal mechanisms of resistance to the BTK inhibitor ibrutinib in chronic lymphocytic leukemia (CLL).

7014 Background: Ibrutinib interacts covalently with cysteine 481 of Bruton tyrosine kinase (BTK), resulting in targeted inhibition of B cell receptor signaling. Early trials of ibrutinib mono- or combination therapy enrolled 246 CLL patients receiving a median of 14 months of ibrutinib. 20 patients (8%) experienced progressive disease (PD), including 8 patients with Richter's transformation. Here we examine changes to the CLL genome in 3 patients that acquired resistance to ibrutinib. Methods: Ibrutinib resistance was defined as patients achieving partial response (PR) or better lasting ≥ 6 months, then developing PD without Richter’s transformation. RNAseq and whole exome sequencing (WES) followed by comparative genome analysis was performed at baseline and after PD and confirmed by Sanger sequencing. RNAseq and WES data were aligned using TopHat and BWA software. Single nucleotide variations (SNVs) were identified using SAMtools mpileup. Results: Compared to patients who relapsed from conventional chemotherapy, minimal genomic changes were acquired in ibrutinib resistant patients, reflecting relative genomic stability. SNVs were discovered in 3 patients specific to the relapse sample (Table). 2 out of 3 patients had distinct SNVs that each encode a cysteine-to-serine substitution at position 481of BTK (C481S). Homologous cysteine residues in BMX, ITK, TEC and BLK were wild-type (WT). Ibrutinib inhibited recombinant C481S 25 fold less potently than WT, and could not covalently bind C481S expressed in cells. The third patient had WT BTK, but acquired a potential gain-of-function mutation encoding a R665W substitution in PLCg2, a substrate of BTK, consistent with constitutive PLCg2 activation. Conclusions: Although rare, the acquisition of C481S BTK and R665W PLCg2 mutations in the setting of resistance confirms BTK as an important pharmacologic target of ibrutinib, and suggests mechanisms of ibrutinib resistance. [Table: see text]

Ibrutinib Impresses in Early Trials

Abstract The Bruton tyrosine kinase inhibitor ibrutinib demonstrated efficacy and safety in early clinical trials for chronic lymphocytic leukemia reported at the annual meeting of the American Society of Hematology.

Targeting Lymphomas Through MALT1 Inhibition

Targeting Lymphomas Through MALT1 Inhibition

BTK inhibitor ibrutinib is cytotoxic to myeloma and potently enhances bortezomib and lenalidomide activities through NF-κB

Ibrutinib (previously known as PCI-32765) has recently shown encouraging clinical activity in chronic lymphocytic leukaemia (CLL) effecting cell death through inhibition of Bruton's tyrosine kinase (BTK). In this study we report for the first time that ibrutinib is cytotoxic to malignant plasma cells from patients with multiple myeloma (MM) and furthermore that treatment with ibrutinib significantly augments the cytotoxic activity of bortezomib and lenalidomide chemotherapies. We describe that the cytotoxicity of ibrutinib in MM is mediated via an inhibitory effect on the nuclear factor-κB (NF-κB) pathway. Specifically, ibrutinib blocks the phosphorylation of serine-536 of the p65 subunit of NF-κB, preventing its nuclear translocation, resulting in down-regulation of anti-apoptotic proteins Bcl-xL, FLIPL and survivin and culminating in caspase-mediated apoptosis within the malignant plasma cells. Taken together these data provide a platform for clinical trials of ibrutinib in myeloma and a rationale for its use in combination therapy, particularly with bortezomib.

PII: S0212-8241(06)71745-5

The present review is part of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Infections in Compromised Hosts (ESGICH) Consensus Document on the safety of targeted and biologic therapies.To review, from an infectious diseases perspective, the safety profile of therapies targeting different intracellular signaling pathways and to suggest preventive recommendations.Computer-based Medline searches with MeSH terms pertaining to each agent or therapeutic family.Although BCR-ABL tyrosine kinase inhibitors modestly increase the overall risk of infection, dasatinib has been associated with cytomegalovirus and hepatitis B virus reactivation. BRAF/MEK kinase inhibitors do not significantly affect infection susceptibility. The effect of Bruton tyrosine kinase inhibitors (ibrutinib) among patients with B-cell malignancies is difficult to distinguish from that of previous immunosuppression. However, cases of Pneumocystis jirovecii pneumonia (PCP), invasive fungal infection and progressive multifocal leukoencephalopathy have been occasionally reported. Because phosphatidylinositol-3-kinase inhibitors (idelalisib) may predispose to opportunistic infections, anti-Pneumocystis prophylaxis and prevention strategies for cytomegalovirus are recommended. No increased rates of infection have been observed with venetoclax (antiapoptotic protein Bcl-2 inhibitor). Therapy with Janus kinase inhibitors markedly increases the incidence of infection. Pretreatment screening for chronic hepatitis B virus and latent tuberculosis infection must be performed, and anti-Pneumocystis prophylaxis should be considered for patients with additional risk factors. Cancer patients receiving mTOR inhibitors face an increased incidence of overall infection, especially those with additional risk factors (prior therapies or delayed wound healing).Specific preventive approaches are warranted in view of the increased risk of infection associated with some of the reviewed agents.