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Concept: B-cell chronic lymphocytic leukemia

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Background The treatment of relapsed chronic lymphocytic leukemia (CLL) has resulted in few durable remissions. Bruton’s tyrosine kinase (BTK), an essential component of B-cell-receptor signaling, mediates interactions with the tumor microenvironment and promotes the survival and proliferation of CLL cells. Methods We conducted a phase 1b-2 multicenter study to assess the safety, efficacy, pharmacokinetics, and pharmacodynamics of ibrutinib (PCI-32765), a first-in-class, oral covalent inhibitor of BTK designed for treatment of B-cell cancers, in patients with relapsed or refractory CLL or small lymphocytic lymphoma. A total of 85 patients, the majority of whom were considered to have high-risk disease, received ibrutinib orally once daily; 51 received 420 mg, and 34 received 840 mg. Results Toxic effects were predominantly grade 1 or 2 and included transient diarrhea, fatigue, and upper respiratory tract infection; thus, patients could receive extended treatment with minimal hematologic toxic effects. The overall response rate was the same in the group that received 420 mg and the group that received 840 mg (71%), and an additional 20% and 15% of patients in the respective groups had a partial response with lymphocytosis. The response was independent of clinical and genomic risk factors present before treatment, including advanced-stage disease, the number of previous therapies, and the 17p13.1 deletion. At 26 months, the estimated progression-free survival rate was 75% and the rate of overall survival was 83%. Conclusions Ibrutinib was associated with a high frequency of durable remissions in patients with relapsed or refractory CLL and small lymphocytic lymphoma, including patients with high-risk genetic lesions. (Funded by Pharmacyclics and others; ClinicalTrials.gov number, NCT01105247 .).

Concepts: Cancer, Hematology, Leukemia, Lymphoma, Respiratory system, Blood disorders, Upper respiratory tract infection, B-cell chronic lymphocytic leukemia

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Background New treatments have improved outcomes for patients with relapsed chronic lymphocytic leukemia (CLL), but complete remissions remain uncommon. Venetoclax has a distinct mechanism of action; it targets BCL2, a protein central to the survival of CLL cells. Methods We conducted a phase 1 dose-escalation study of daily oral venetoclax in patients with relapsed or refractory CLL or small lymphocytic lymphoma (SLL) to assess safety, pharmacokinetic profile, and efficacy. In the dose-escalation phase, 56 patients received active treatment in one of eight dose groups that ranged from 150 to 1200 mg per day. In an expansion cohort, 60 additional patients were treated with a weekly stepwise ramp-up in doses as high as 400 mg per day. Results The majority of the study patients had received multiple previous treatments, and 89% had poor prognostic clinical or genetic features. Venetoclax was active at all dose levels. Clinical tumor lysis syndrome occurred in 3 of 56 patients in the dose-escalation cohort, with one death. After adjustments to the dose-escalation schedule, clinical tumor lysis syndrome did not occur in any of the 60 patients in the expansion cohort. Other toxic effects included mild diarrhea (in 52% of the patients), upper respiratory tract infection (in 48%), nausea (in 47%), and grade 3 or 4 neutropenia (in 41%). A maximum tolerated dose was not identified. Among the 116 patients who received venetoclax, 92 (79%) had a response. Response rates ranged from 71 to 79% among patients in subgroups with an adverse prognosis, including those with resistance to fludarabine, those with chromosome 17p deletions (deletion 17p CLL), and those with unmutated IGHV. Complete remissions occurred in 20% of the patients, including 5% who had no minimal residual disease on flow cytometry. The 15-month progression-free survival estimate for the 400-mg dose groups was 69%. Conclusions Selective targeting of BCL2 with venetoclax had a manageable safety profile and induced substantial responses in patients with relapsed CLL or SLL, including those with poor prognostic features. (Funded by AbbVie and Genentech; ClinicalTrials.gov number, NCT01328626 .).

Concepts: Oncology, Hematology, Leukemia, Respiratory system, Blood disorders, Upper respiratory tract, Upper respiratory tract infection, B-cell chronic lymphocytic leukemia

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ROR1 is an oncoembryonic orphan-receptor found on chronic lymphocytic leukemia (CLL) B cells, but not on normal post-partum tissues. ROR1 is a receptor for Wnt5a that may complex with TCL1, a co-activator of AKT that is able to promote development of CLL. We found the CLL cells of a few patients expressed negligible ROR1 (ROR1(Neg)), but expressed TCL1A at levels comparable to those of samples that expressed ROR1 (ROR1(Pos)). Transcriptome analyses revealed that ROR1(Neg) cases generally could be distinguished from those that were ROR1(Pos) in unsupervised gene-expression clustering analysis. Gene-set enrichment analyses demonstrated that ROR1(Neg) CLL had lower expression and activation of AKT-signaling pathways relative to ROR1(Pos) CLL, similar to what was noted for leukemia that respectively developed in TCL1 versus ROR1xTCL1 transgenic mice. In contrast to its effect on ROR1(Pos) CLL, Wnt5a did not enhance the proliferation, chemotaxis, or survival of ROR1(Neg) CLL. We examined the CLL cells from 1,568 patients, which we randomly assigned to a training or validation set of 797 or 771 cases, respectively. Using recursive partitioning, we defined a threshold for ROR1-surface-expression that could segregate samples of the training set into ROR1-Hi versus ROR1-Lo subgroups that differed significantly in their median treatment free survival (TFS). Using this threshold, we found that ROR1-Hi cases had a significantly shorter median TFS and overall survival than ROR1-Lo cases in the validation set. These data demonstrate that expression of ROR1 may promote leukemia-cell activation and survival and enhance disease progression in patients with CLL.

Concepts: Lymphocyte, Protein, Gene expression, B cell, Leukemia, Genetically modified organism, AKT1, B-cell chronic lymphocytic leukemia

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Ibrutinib (BTK inhibitor) has generated remarkable responses in CLL. However, the drug, to a large extent, does not cause cell death directly and does not eradicate CLL malignant clones. Inability to eradicate CLL has fostered resistance generation. Once patients become resistant, they do poorly with a median survival of 3-4 months. Novel therapeutic strategies are needed to prevent resistance, improve treatment outcome and ultimately cure the disease. Herein, we explore dual targeting of the BCR and JAK-STAT pathways with a novel single agent, cerdulatinib, which selectively inhibits both SYK (a BCR component) and JAK kinases. We demonstrated that cerdulatinib delivered potent tumor inhibition in 60 primary CLL patient samples, especially in those with poor prognostic indicators. Importantly, cerdulatinib, but not ibrutinib, is able to overcome the support of microenvironment and induces CLL cell death at clinically achievable concentrations. Notably, cerdulatinib blocked proliferation of ibrutinib-resistant primary CLL cells and of BTKC481S-transfected/ibrutinib-resistant lymphoma cells. These anti-tumor effects are well correlated with the inhibition of BCR and JAK-STAT signaling and downstream inhibition of the functions of AKT, ERK and NFκB. Collectively, our results show that simultaneous targeting of BCR and JAK-STAT pathways is a more effective strategy relative to single BTK inhibition.

Concepts: Cancer, Oncology, Poverty, Leukemia, Lymphoma, Enzyme inhibitor, Inhibitor, B-cell chronic lymphocytic leukemia

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Chemoimmunotherapy has led to improved numbers of patients achieving disease response, and longer overall survival in young patients with chronic lymphocytic leukaemia; however, its application in elderly patients has been restricted by substantial myelosuppression and infection. We aimed to assess safety and activity of ibrutinib, an orally administered covalent inhibitor of Bruton tyrosine kinase (BTK), in treatment-naive patients aged 65 years and older with chronic lymphocytic leukaemia.

Concepts: Cancer, Protein kinase, Hematology, Leukemia, B-cell chronic lymphocytic leukemia, Small lymphocytic lymphoma

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Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncoembryonic protein expressed on chronic lymphocytic leukemia (CLL) that can serve as a receptor for Wnt5a, which can promote leukemia-cell migration, proliferation, and survival. We found Wnt5a could induce ROR1 to complex with DOCK2 and induce activation of Rac1/2; these effects could be blocked by cirmtuzumab, a humanized anti-ROR1 mAb. We find that silencing DOCK2 specifically impaired the capacity of Wnt5a to induce activation of Rac1/2 or enhance CLL-cell proliferation. We generated truncated forms of ROR1 and found the cytoplasmic proline-rich domain (PRD) of ROR1 was required for Wnt5a to induce ROR1 to complex with DOCK2 and activate Rac1/2 in the CLL cell-line MEC1. We introduced single amino-acid substitutions of proline (P) to alanine (A) in the ROR1-PRD at potential binding sites for the Src-homology 3 (SH3) domain of DOCK2. In contrast to wild-type ROR1, or other ROR1 P->A variants, ROR1P808A was unable to recruit DOCK2 in response to Wnt5a. Moreover, unlike MEC1 cells transfected with wild-type ROR1 or ROR1 with P->A substitutions at positions 784, 826, or 841, MEC1 cells transfected to express ROR1P808A did not have a growth advantage over MEC1 cells that do not express ROR1. This study reveals that the recruitment of DOCK2 may be critical for the capacity of Wnt5a to enhance CLL proliferation, which may contribute to the observed increased tendency for disease progression in patients who have CLL cells that express high-levels of ROR1.

Concepts: Protein, Gene, Amino acid, Signal transduction, Leukemia, Blood disorders, Nuclear receptor, B-cell chronic lymphocytic leukemia

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Chronic lymphocytic leukemia (CLL) is a highly heterogeneous disease. Deregulation of apoptosis is a major pathogenetic feature, and represents a therapeutic target. TP53 disrupted patients are categorized as high risk patients and are treated with novel target therapies. Among these new drugs, venetoclax, an orally bioavailable BCL2 inhibitor, has shown high efficacy also in relapsed/refractory CLL with TP53 disruption. Venetoclax has also been tested in combination with other drugs without compromising venetoclax dose and with a good safety profile. Areas covered. This article covers the biology of apoptosis in CLL from a translational viewpoint and deals with the mode of action of BCL2 inhibitors, in particular venetoclax. On this biological rationale, the review then focuses on the results obtained in clinical trials with venetoclax in CLL. Expert commentary. The availability of venetoclax represents a major advance in CLL treatment and offers new opportunities to further improve the results obtained until now by combining venetoclax with other agents. Venetoclax has achieved responses also in patients with TP53 disruption. These results strongly suggest that the mechanism by which venetoclax kills CLL cells might overcome a dysfunctional TP53 that is a major hallmark of chemorefractoriness to conventional antineoplastic agents.

Concepts: Immune system, Medicine, Cancer, Biology, Apoptosis, Leukemia, Blood disorders, B-cell chronic lymphocytic leukemia

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In the Asia-Pacific region, treatment options are limited for patients with relapsed/refractory chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). Rituximab is widely used in this setting when purine analog-based therapies are not appropriate. We evaluated the efficacy and safety of ibrutinib compared with rituximab in a randomized, open-label phase 3 study in predominantly Asian patients with relapsed/refractory CLL/SLL. Patients (N = 160) were randomly assigned 2:1 to receive 420 mg ibrutinib (n = 106) until disease progression (PD) or unacceptable toxicity or up to six cycles of rituximab (n = 54). The primary endpoint was investigator-assessed progression-free survival (PFS); key secondary endpoints were overall response rate (ORR), overall survival (OS), and safety. Rituximab-treated patients could crossover to receive ibrutinib after confirmed PD. At data cutoff, median treatment duration was 16.4 months for ibrutinib and 4.6 months for rituximab. Ibrutinib significantly improved PFS (hazard ratio [HR] = 0.180, 95% confidence interval [CI]: 0.105-0.308). ORR was significantly higher (P < 0.0001) with ibrutinib (53.8%) than with rituximab (7.4%). At a median follow-up of 17.8 months, ibrutinib improved OS compared with rituximab (HR = 0.446; 95% CI: 0.221-0.900; P = 0.0206). Overall incidence of adverse events (AEs) was similar between treatments and was not exposure-adjusted. With ibrutinib, most common AEs were diarrhea and platelet count decreased; with rituximab, most common AEs were neutrophil count decreased and platelet count decreased. Grade ≥3 AEs were reported in 82.7% of ibrutinib-treated patients and 59.6% of rituximab-treated patients. Ibrutinib improved PFS, ORR, and OS compared with rituximab and displayed a manageable safety profile in Asian patients with relapsed/refractory CLL/SLL.

Concepts: Chemotherapy, Types of cancer, Leukemia, Lymphoma, Blood disorders, B-cell chronic lymphocytic leukemia, Asia-Pacific, Small lymphocytic lymphoma

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Although the progression of chronic lymphocytic leukemia (CLL) requires the cooperation of the microenvironment, the exact cellular and molecular mechanisms involved are still unclear. We investigated the interleukin (IL)-23 receptor (IL-23R)/IL-23 axis and found that circulating cells from early-stage CLL patients with shorter time-to-treatment, but not of those with a more benign course, expressed a defective form of the IL-23R complex lacking the IL-12Rβ1 chain. However, cells from both patient groups expressed the complete IL-23R complex in tissue infiltrates and could be induced to express the IL-12Rβ1 chain when cocultured with activated T cells or CD40L+cells. CLL cells activated in vitro in this context produced IL-23, a finding that, together with the presence of IL-23 in CLL lymphoid tissues, suggests the existence of an autocrine/paracrine loop inducing CLL cell proliferation. Interference with the IL-23R/IL-23 axis using an anti-IL-23p19 antibody proved effective in controlling disease onset and expansion in xenografted mice, suggesting potential therapeutic strategies.

Concepts: Immune system, White blood cell, Protein, Medicine, Natural killer cell, B cell, Leukemia, B-cell chronic lymphocytic leukemia

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We previously showed that MMP-9 overexpression impairs migration of primary CLL cells and MEC-1 cells transfected with MMP-9. To determine the contribution of non-proteolytic activities to this effect we generated MEC-1 transfectants stably expressing catalytically inactive MMP-9MutE (MMP-9MutE-cells). In xenograft models in mice, MMP-9MutE-cells showed impaired homing to spleen and bone marrow, compared to cells transfected with empty vector (Mock-cells). In vitro transendothelial and random migration of MMP-9MutE-cells were also reduced. Biochemical analyses indicated that RhoAGTPase and p-Akt were not downregulated by MMP-9MutE, at difference with MMP-9. However, MMP-9MutE-cells or primary cells incubated with MMP-9MutE had significantly reduced p-ERK and increased PTEN, accounting for the impaired migration. Our results emphasize the role of non-proteolytic MMP-9 functions contributing to CLL progression.

Concepts: White blood cell, Blood, Bone marrow, Hematology, Leukemia, In vitro, Blood disorders, B-cell chronic lymphocytic leukemia