Summary Background Ibrutinib, an orally administered covalent inhibitor of Bruton tyrosine kinase (BTK), is an effective therapy for patients with relapsed chronic lymphocytic leukemia (CLL). We investigated the activity and safety of the combination of ibrutinib with the monoclonal antibody rituximab (iR) in patients with high-risk CLL. Methods In this single-arm, phase 2 studywe enrolled 40 patients with high-risk CLL at MD Anderson Cancer Center, Houston, Texas, USA. Patients with symptomatic CLL requiring therapy received 28 day cycles of once-daily ibrutinib 420 mg , together with rituximab (weekly during cycle 1, then once per cycle until cycle 6), followed by continuous single-agent ibrutinib. The primary endpoint was progression-free survival (PFS) in the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT01520519 and is no longer accruing patients. Findings Between February 28, 2012 and September 11, 2012, we enrolled 40 CLL patients with high-risk disease features. 20 patients had del17p or TP53 mutations (16 previously treated, 4 untreated), 13 had relapsed CLL with del11q, and 7 patients a PFS < 36 months after frontline chemo-immunotherapy. Toxicity was mainly of mild to moderate severity (grade 1–2). 10 (25%) patients had diarrhea (grade 1 in 9 [22.5%] patients, grade 2 in 1 [2.5%]), bleeding events occurred in 14 (35%) patients (8 [20%] patients with grade 1, 5 [12.5%] patients grade 2, and 1 [2.5%] grade 3), nausea in 15 (37.5) patients (10 [25%] grade 1, 5 [12.5%] grade 2), and fatigue in 7 (17.5%) patients (4 [10%] grade 1, 3 [7.5%] grade 2). Grade 3 infections occurred in 4 patients (10%), no grade 4 or 5 infections occurred. At 18 months, the Kaplan Meier estimate of progression-free survival was 78% (95% CI 60.6–88.5) (del[17p] or TP53 mutation: 72%, 95% CI: 45.6–87.6) Interpretation Ibrutinib in combination with rituximab is a well-tolerated regimen for patients with high-risk CLL. It induces high rates of remissions and has positive impact on QOL in this difficult-to-treat patient population. These encouraging data merit further investigation of the added benefit of rituximab as combination partner for ibrutinib in an ongoing randomized trial, in which single-agent ibrutinib is compared to iR combination therapy (NCT02007044). Funding Pharmacyclics, Inc., Cancer Prevention and Research Institute of Texas (CPRIT), Leukemia & Lymphoma Society, NCI Grant P30 CA016672, MD Anderson’s Moon Shot Program in CLL, and MD Anderson Cancer Center Support Grant CA016672.

The use of novel B-cell receptor signaling inhibitors results in high response rates and long progression-free survival in patients with indolent B-cell malignancies, such as chronic lymphocytic leukemia, follicular lymphoma, mantle cell lymphoma and Waldenström macroglobulinemia. Ibrutinib, the first-in-class inhibitor of Bruton tyrosine kinase, and idelalisib, the first-in-class inhibitor of phosphatidylinositol 3-kinase δ, have recently been approved for the treatment of several indolent B-cell malignancies. These drugs are especially being used for previously unmet needs, i.e., for patients with relapsed or refractory disease, high-risk cytogenetic or molecular abnormalities, or with comorbidities. Treatment with ibrutinib and idelalisib is generally well tolerated, even by elderly patients. However, the use of these drugs may come with toxicities that are distinct from the side effects of immunochemotherapy. In this review we discuss the most commonly reported and/or most clinically relevant adverse events associated with these B-cell receptor inhibitors, with special emphasis on recommendations for their management.

Morbidity and mortality due to immunosuppression remain among the foremost clinical challenges in chronic lymphocytic leukemia (CLL). Although immunosuppression is considered to originate within the lymph node (LN) microenvironment, alterations in T and natural killer (NK) cells have almost exclusively been studied in peripheral blood (PB). Whereas chemoimmunotherapy further deteriorates immune function, novel targeted agents like the B-cell lymphoma 2 inhibitor venetoclax potentially spare nonmalignant lymphocytes; however, the effects of venetoclax on nonleukemic cells have not been explored. We address these unresolved issues using a comprehensive analysis of nonmalignant lymphocytes in paired LN and PB samples from untreated CLL patients, and by analyzing the effects of venetoclax-based treatment regimens on the immune system in PB samples from previously untreated and relapsed/refractory patients. CLL-derived LNs contained twice the amount of suppressive regulatory T cells (Tregs) and CLL supportive follicular T helper (Tfh) cells compared with PB. This was accompanied by a low frequency of cytotoxic lymphocytes. The expression of PD-1 by CD8+ T cells was significantly higher in LN compared with PB. Venetoclax-based treatment led to deep responses in the majority of patients, but also to decreased absolute numbers of B, T, and NK cells. Tfh cell, Treg, and PD-1+ CD8+ T cell numbers were reduced more than fivefold after venetoclax-based therapy, and overproduction of inflammatory cytokines was reduced. Furthermore, we observed restoration of NK cell function. These data support the notion that the immunosuppressive state in CLL is more prominent within the LN. Venetoclax-based regimens reduced the immunosuppressive footprint of CLL, suggesting immune recovery after the elimination of leukemic cells.

The efficacy of autologous (αβ) T-cell-based treatment strategies in chronic lymphocytic leukemia (CLL) has been modest. The Vγ9Vδ2-T cell subset consists of cytotoxic T lymphocytes with potent antilymphoma activity via a major histocompatibility complex-independent mechanism. We studied whether Vγ9Vδ2-T cells can be exploited as autologous effector lymphocytes in CLL. Healthy control Vγ9Vδ2-T cells were activated by and had potent cytolytic activity against CLL cells. However, CLL-derived Vγ9Vδ2-T cells proved dysfunctional with respect to effector cytokine production and degranulation, despite an increased frequency of the effector-type subset. Consequently, cytotoxicity against malignant B cells was hampered. A comparable dysfunctional phenotype was observed in healthy Vγ9Vδ2-T cells after coculture with CLL cells, indicating a leukemia-induced mechanism. Gene-expression profiling implicated alterations in synapse formation as a conceivable contributor to compromised Vγ9Vδ2-T-cell function in CLL patients. Dysfunction of Vγ9Vδ2-T cells was fully reversible upon activation with autologous monocyte-derived dendritic cells (moDCs). moDC activation resulted in efficient expansion and predominantly yielded Vγ9Vδ2-T cells with a memory phenotype. Furthermore, ibrutinib treatment promoted an antitumor T helper 1 (T1) phenotype in Vγ9Vδ2-T cells, and we demonstrated binding of ibrutinib to IL-2-inducible kinase (ITK) in Vγ9Vδ2-T cells. Taken together, CLL-mediated dysfunction of autologous Vγ9Vδ2-T cells is fully reversible, resulting in potent cytotoxicity toward CLL cells. Our data support the potential use of Vγ9Vδ2-T cells as effector T cells in CLL immunotherapy and favor further exploration of combining Vγ9Vδ2-T-cell-based therapy with ibrutinib.