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Chronic lymphocytic leukemia (CLL) is a quiescent B-cell malignancy that depends on transcriptional dysregulation for survival. The histone deacetylases are transcriptional regulators whose role within the regulatory chromatin and consequence on the CLL transcriptome is poorly characterized. Here, we profiled and integrated the genome-wide occupancy of HDAC1, BRD4, H3K27Ac, and H3K9Ac signals with chromatin accessibility, Pol2 occupancy, and target expression signatures in CLL cells. We identified that when HDAC1 was recruited within super-enhancers (SEs) marked by acetylated H3K27 and BRD4, it functioned as a transcriptional activator that drove the de novo expression of select genes to facilitate survival and progression in CLL. Targeting HDACs reduced BRD4 and Pol2 engagement to downregulate the transcript and proteins levels of specific oncogenic driver genes in CLL such as BLK, a key mediator of the B-cell receptor pathway, core transcription factors such as PAX5 and IKZF3, and the antiapoptotic gene, BCL2. Concurrently, HDAC1, when recruited in the absence of SEs, repressed target gene expression. HDAC inhibition reversed silencing of a defined set of protein-coding and noncoding RNA genes. We focused on a specific set of microRNA genes and showed that their upregulation was inversely correlated with the expression of CLL-specific survival, transcription factor, and signaling genes. Our findings identify that the transcriptional activator and repressor functions of HDACs cooperate within the same tumor to establish the transcriptional dependencies essential for survival in CLL., (© 2023 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma; 40% of patients relapse after a complete response or are refractory to therapy. To survive, the activated B-cell (ABC) subtype of DLBCL relies upon B-cell receptor signaling, which can be modulated by the activity of Bruton tyrosine kinase (BTK). Targeting BTK with ibrutinib, an inhibitor, provides a therapeutic approach for this subtype of DLBCL. However, non-Hodgkin lymphoma is often resistant to ibrutinib or acquires resistance soon after exposure. We explored how this resistance develops. We generated 3 isogenic ibrutinib-resistant DLBCL cell lines and investigated the deregulated pathways known to be associated with tumorigenic properties. Reduced levels of BTK and enhanced phosphatidylinositol 3-kinase (PI3K)/AKT signaling were hallmarks of these ibrutinib-resistant cells. Upregulation of PI3K-β expression was demonstrated to drive resistance in ibrutinib-resistant cells, and resistance was reversed by the blocking activity of PI3K-β/δ. Treatment with the selective PI3K-β/δ dual inhibitor KA2237 reduced both tumorigenic properties and survival-based PI3K/AKT/mTOR signaling of these ibrutinib-resistant cells. In addition, combining KA2237 with currently available chemotherapeutic agents synergistically inhibited metabolic growth. This study elucidates the compensatory upregulated PI3K/AKT axis that emerges in ibrutinib-resistant cells., (© 2020 by The American Society of Hematology.)

The Bruton tyrosine kinase (BTK) inhibitor ibrutinib improves patient outcomes in chronic lymphocytic leukemia (CLL); however, some patients experience adverse events (AEs) leading to discontinuation. Acalabrutinib is a potent, covalent BTK inhibitor with greater selectivity than ibrutinib. We evaluated the safety and efficacy of 100 mg of acalabrutinib twice daily or 200 mg once daily in patients with CLL who discontinued ibrutinib because of intolerance as determined by the investigators. Among 33 treated patients (61% men; median age, 64 years; range, 50-82 years), median duration of prior ibrutinib treatment was 11.6 months (range, 1-62 months); median time from ibrutinib discontinuation to acalabrutinib start was 47 days (range, 3-331 days). After a median of 19.0 months (range, 0.2-30.6 months), 23 patients remained on acalabrutinib; 10 had discontinued (progressive disease, n = 4; AEs, n = 3). No acalabrutinib dose reductions occurred. During acalabrutinib treatment, the most frequent AEs included diarrhea (58%), headache (39%), and cough (33%). Grade 3/4 AEs occurred in 58%, most commonly neutropenia (12%) and thrombocytopenia (9%). Of 61 ibrutinib-related AEs associated with intolerance, 72% did not recur and 13% recurred at a lower grade with acalabrutinib. Overall response rate was 76%, including 1 complete and 19 partial responses and 5 partial responses with lymphocytosis. Among 25 responders, median duration of response was not reached. Median progression-free survival (PFS) was not reached; 1-year PFS was 83.4% (95% confidence interval, 64.5%-92.7%). Acalabrutinib was well tolerated with a high response rate in patients who were previously intolerant to ibrutinib. This trial was registered at www.clinicaltrials.gov as #NCT02029443., (© 2019 by The American Society of Hematology.)

The Bruton tyrosine kinase inhibitor (BTKi) ibrutinib has transformed chronic lymphocytic leukemia (CLL) therapy but requires continuous administration. These factors have spurred interest in combination treatments. Unlike with chemotherapy, CD20-directed antibody therapy has not improved the outcome of BTKi treatment. Whereas CD20 antigen density on CLL cells decreases during ibrutinib treatment, the B-cell activating factor (BAFF) and its receptor (BAFF-R) remain elevated. Furthermore, BAFF signaling via noncanonical NF-κB remains elevated with BTKi treatment. Blocking BAFF interaction with BAFF-R by using VAY-736, a humanized defucosylated engineered antibody directed against BAFF-R, antagonized BAFF-mediated apoptosis protection and signaling at the population and single-cell levels in CLL cells. Furthermore, VAY-736 showed superior antibody-dependent cellular cytotoxicity compared with CD20- and CD52-directed antibodies used in CLL. VAY-736 exhibited in vivo activity as a monotherapy and, when combined with ibrutinib, produced prolonged survival compared with either therapy alone. The in vivo activity of VAY-736 is dependent upon immunoreceptor tyrosine-based activation motif (ITAM)-mediated activation of effector cells as shown by using an ITAM-deficient mouse model. Collectively, our findings support targeting the BAFF signaling pathway with VAY-736 to more effectively treat CLL as a single agent and in combination with ibrutinib., (© 2019 by The American Society of Hematology.)

Atrial fibrillation (AF) has been reported in up to 16% of patients taking ibrutinib. Data regarding the management of AF in this patient population are limited, and stroke prevention poses a challenge because of increased risk of bleeding with ibrutinib treatment. Our study sought to describe the incidence of AF in adult patients treated with ibrutinib for a hematologic malignancy, assess management strategies, evaluate stroke and bleeding outcomes, and identify risk factors for occurrence. Of 582 patients treated with ibrutinib, 76 developed AF. With a median follow-up of 32 months, the estimated cumulative incidence at 6 months, 1 year, and 2 years was 5.9% (95% confidence interval [CI]: 4.2-8.0), 7.5% (95% CI: 5.5-9.9), and 10.3% (95% CI: 8.0-13.0), respectively. Median time to onset of AF was 7.6 months. History of AF and Framingham Heart Study (FHS) AF risk score were found to be significant risk factors for development of AF. Most patients were treated with rate control-only strategies (61.8%), and concomitant aspirin or anticoagulant therapy with ibrutinib was used in 52.6% and 28.9% of patients, respectively. One patient on aspirin developed symptoms consistent with stroke. Nine major bleeds were noted in 7 patients, and 34 clinically relevant nonmajor bleeds were noted in 24 patients. Twenty-one bleeds (4 major bleeds) occurred in 18 patients on aspirin, and 10 bleeds (all clinically relevant nonmajor bleeds) occurred in 6 patients with anticoagulant therapy. These results provide risk factor assessment, impact of management strategies, and outcomes of patients with AF on ibrutinib and serve as basis for formal guidelines., Competing Interests: Conflict-of-interest disclosure: K.M. has received research funding from Merck Oncology and Pharmacyclics, Inc and has provided consulting services for Bristol Myers Squibb, Seattle Genetics, Janssen, and Pharmacyclics, Inc. B.C. has received research funding from Janssen and Pharmacyclics, Inc. L.A.A. has received research funding from Sanofi. S.J. has received research funding from Pharmacyclics, Inc and has provided consulting services for Seattle Genetics and Pharmacyclics, Inc. J.W. received research funding from Acerta Pharma, Karyopharm Therapeutics, and Morphosys. J.J. has received research funding from Acerta Pharma, Abbvie, Gilead Sciences, Pharmacyclics, Inc, Genentech, and Janssen Pharmaceutical and has provided consulting services for Gilead Sciences, Pharmacyclics, Inc, Genentech, and Janssen Pharmaceutical. M.G. has served in an advisory role for Pharmacyclics, Inc and serves on the Data and Safety Monitoring Board for Acerta Pharma. K.A.B. has received research funding from Janssen and Pharmacyclics, Inc. J.C.B. has received research funding from Acerta Pharma, Pharmacyclics, Inc, and Genentech. F.T.A. has received research funding from Innate Pharma and provided consulting services to Gilead Sciences, Pharmacyclics, Inc and Novartis Oncology. The remaining authors declare no competing financial interests.