A bispecific T cell engager recruits both type 1 NKT and Vγ9Vδ2-T cells for the treatment of CD1d-expressing hematological malignancies.

Bispecific T cell engagers (bsTCEs) hold great promise for cancer treatment but face challenges due to the induction of cytokine release syndrome (CRS), on-target off-tumor toxicity, and the engagement of immunosuppressive regulatory T cells that limit efficacy. The development of Vγ9Vδ2-T cell engagers may overcome these challenges by combining high therapeutic efficacy with limited toxicity. By linking a CD1d-specific single-domain antibody (VHH) to a Vδ2-TCR-specific VHH, we create a bsTCE with trispecific properties, which engages not only Vγ9Vδ2-T cells but also type 1 NKT cells to CD1d+ tumors and triggers robust proinflammatory cytokine production, effector cell expansion, and target cell lysis in vitro. We show that CD1d is expressed by the majority of patient MM, (myelo)monocytic AML, and CLL cells and that the bsTCE triggers type 1 NKT and Vγ9Vδ2-T cell-mediated antitumor activity against these patient tumor cells and improves survival in in vivo AML, MM, and T-ALL mouse models. Evaluation of a surrogate CD1d-γδ bsTCE in NHPs shows Vγ9Vδ2-T cell engagement and excellent tolerability. Based on these results, CD1d-Vδ2 bsTCE (LAVA-051) is now evaluated in a phase 1/2a study in patients with therapy refractory CLL, MM, or AML.

A Bispecific Single-Domain Antibody Boosts Autologous Vγ9Vδ2-T Cell Responses Toward CD1d in Chronic Lymphocytic Leukemia.

PURPOSE: Although considerable progress has been made with autologous T cell-based therapy in B-cell malignancies, application in chronic lymphocytic leukemia (CLL) lags behind due to disappointing response rates as well as substantial toxicity that is of particular concern in the elderly CLL population. Vγ9Vδ2-T cells form a conserved T-cell subset with strong intrinsic immunotherapeutic potential, largely because of their capacity to be triggered by phosphoantigens that can be overproduced by CLL and other malignant cells. Specific activation of Vγ9Vδ2-T cells by a bispecific antibody may improve the efficacy and toxicity of autologous T-cell-based therapy in CLL. EXPERIMENTAL DESIGN: We evaluated CD1d expression in a cohort of 78 untreated patients with CLL and generated and functionally characterized a CD1d-specific Vγ9Vδ2-T cell engager based on single-domain antibodies (VHH). RESULTS: CD1d was expressed by CLL in the majority of patients, particularly in patients with advanced disease. The CD1d-specific Vγ9Vδ2-T cell engager induced robust activation and degranulation of Vγ9Vδ2-T cells, enabling Vγ9Vδ2-T cells from patients with CLL to lyse autologous leukemic cells at low effector-to-target ratios. Expression of CD1d on CLL cells is upregulated by all-trans retinoic acid, and sensitizes the malignant cells to bispecific VHH-induced lysis. Furthermore, we provide evidence that the Vγ9Vδ2-T cell receptor retains responsiveness to phosphoantigens when the bispecific VHH is bound, and aminobisphosphonates can therefore enhance bispecific Vγ9Vδ2-T cell engager-mediated tumor-specific killing. CONCLUSIONS: Collectively, our data demonstrate the immunotherapeutic potential of this novel CD1d-specific Vγ9Vδ2-T cell engager in CLL.

A Bispecific Antibody Antagonizes Prosurvival CD40 Signaling and Promotes Vγ9Vδ2 T cell-Mediated Antitumor Responses in Human B-cell Malignancies.

Novel T cell-based therapies for the treatment of B-cell malignancies, such as chronic lymphocytic leukemia (CLL) and multiple myeloma (MM), are thought to have strong potential. Progress, however, has been hampered by low efficacy and high toxicity. Tumor targeting by Vγ9Vδ2 T cells, a conserved T-cell subset with potent intrinsic antitumor properties, mediated by a bispecific antibody represents a novel approach promising high efficacy with limited toxicity. Here, we describe the generation of a bispecific Vγ9Vδ2 T-cell engager directed against CD40, which, due to its overexpression and biological footprint in malignant B cells, represents an attractive target. The CD40-targeting moiety of the bispecific antibody was selected because it can prevent CD40L-induced prosurvival signaling and reduce CD40-mediated resistance of CLL cells to venetoclax. Selective activation of Vγ9Vδ2 T cells in the presence of CD40+ tumor cells induced potent Vγ9Vδ2 T-cell degranulation, cytotoxicity against CLL and MM cells in vitro, and in vivo control of MM in a xenograft model. The CD40-bispecific γδ T-cell engager demonstrated lysis of leukemic cells by autologous Vγ9Vδ2 T cells present in patient-derived samples. Taken together, our CD40 bispecific γδ T-cell engager increased the sensitivity of leukemic cells to apoptosis and induced a potent Vγ9Vδ2 T cell-dependent antileukemic response. It may, therefore, represent a potential candidate for the development of novel treatments for B-cell malignancies.

Functional Differences Between EBV- and CMV-Specific CD8+ T cells Demonstrate Heterogeneity of T cell Dysfunction in CLL.

Acquired T cell dysfunction is a hallmark of chronic lymphocytic leukemia (CLL), and is linked to an increased risk of infections, but also reduced immune surveillance and disappointing responses to autologous T cell-based immunotherapy. The mechanisms of T cell dysfunction in CLL are not well understood. Studying immunity against chronic viruses allows for detailed analysis of the effect of CLL on T cells chronically exposed to a specific antigen. Cytomegalovirus (CMV) reactivations are rare in CLL, which corroborates with preserved CMV-specific T cell function. Epstein-Barr virus (EBV) is another herpesvirus that results in chronic infection, but unlike CMV, is characterized by subclinical reactivations in CLL patients. Since both herpesviruses induce strong CD8+ T cell responses, but have different clinical outcomes, studying these specific T cells may shed light on the mechanisms of CLL-induced T cell dysfunction. We first analyzed the phenotype of EBV-specific CD8+ T cells in CLL and healthy controls, and found that in CLL EBV-specific CD8+ T cells are in an advanced differentiation state with higher expression of inhibitory receptors. Secondly, CLL-derived EBV-specific CD8+ T cells show reduced cytotoxic potential, in contrast to CMV-specific T cells. Finally, we performed transcriptome analysis to visualize differential modulation by CLL of these T cell subsets. While T cell activation and differentiation genes are unaffected, in EBV-specific T cells expression of genes involved in synapse formation and T cell exhaustion is altered. Our findings on the heterogeneity of antigen specific T cell function in CLL aids in understanding immune-dysregulation in this disease.

Distinct immune composition in lymph node and peripheral blood of CLL patients is reshaped during venetoclax treatment.

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.

Dissection of the Effects of JAK and BTK Inhibitors on the Functionality of Healthy and Malignant Lymphocytes.

Despite the emergence of small molecule inhibitors, current treatment strategies for chronic lymphocytic leukemia (CLL) are not curative, and the search for new therapeutic modalities continues. Prosurvival signaling derived from the microenvironment is often mediated via JAK signaling. However, whether JAK inhibitors are useful in CLL therapy has not been studied extensively. JAK inhibitors are valuable therapeutic agents in myelofibrosis and show promising results in graft-versus-host-disease. However, JAK inhibition is associated with an increased infection risk, presumably because of the effect on other immune cells, a feature shared with other kinase inhibitors used for CLL treatment, such as the BTK inhibitor ibrutinib and the PI3Kδ inhibitor idelalisib. We compared functional effects of the JAK1/2 inhibitors momelotinib and ruxolitinib, the BTK inhibitors ibrutinib and tirabrutinib, and PI3Kδ inhibitor idelalisib on malignant CLL cells but also on healthy human T, B, and NK lymphocytes. We found several interesting differences among the inhibitors, apart from expected and well-known effects. Momelotinib but not ruxolitinib blocked cytokine-induced proliferation of CLL cells. Momelotinib also reduced BCR signaling, in contrast to ruxolitinib, indicating that these JAK inhibitors in fact have a distinct target spectrum. In contrast to tirabrutinib, ibrutinib had inhibitory effects on T cell activation, probably because of ITK inhibition. Remarkably, both BTK inhibitors stimulated IFN-γ production in a mixed lymphocyte reaction. Collectively, our results demonstrate that kinase inhibitors directed at identical targets may have differential effects on lymphocyte function. Their unique profile could be strategically employed to balance desired versus unwanted lymphocyte inhibition.

Natural Killer Cell Hypo-responsiveness in Chronic Lymphocytic Leukemia can be Circumvented In Vitro by Adequate Activating Signaling.

Chronic lymphocytic leukemia (CLL) is characterized by an acquired immune dysfunction, which may underlie the hampered efficacy of cellular immunotherapy. Most data on dampened immune responses in CLL come from studies investigating CLL and T cell interactions. Natural killer (NK) cells may be an attractive alternative source of effector cells in immunotherapy in CLL, provided that functionality is retained within the CLL micro-environment. Despite their important role in anti-tumor responses, NK cells are not extensively characterized in CLL. Here, we studied the expression of activating and inhibitory receptors on CLL-derived and healthy control (HC) NK cells, and their functional response towards several stimuli. NK cells from CLL patients have an increased maturation stage, with an expansion of NKG2C+ NK cells in CMV seropositive individuals. The cytotoxicity receptor NKG2D is downregulated, and the killing capacity through this receptor was markedly reduced in CLL-derived NK cells. In contrast, activation via CD16 (FCγRIII) led to adequate activation and functional responses in CLL-derived NK cells. These findings indicate that NK cells in CLL are not intrinsically defect and still perform effector functions upon adequate activating signaling. Clinical relevance of this finding was shown by treatment with novel nanobody-Fc constructs, which induced cytotoxic responses in both CLL- and HC-derived NK cells via CD16. Our results show that NK cells, in contrast to the T cell compartment, retain their function within the CLL micro-environment, provided that they receive an adequate activating signal. These findings warrant future studies on NK cell mediated immunotherapeutic strategies in CLL.

Improving CLL Vγ9Vδ2-T-cell fitness for cellular therapy by ex vivo activation and ibrutinib.

The efficacy of autologous (αß) 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 (TH1) 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.

Incidence and management of toxicity associated with ibrutinib and idelalisib: a practical approach.

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.

Safety and activity of ibrutinib plus rituximab for patients with high-risk chronic lymphocytic leukaemia: a single-arm, phase 2 study.

BACKGROUND: Ibrutinib, an orally administered covalent inhibitor of Bruton's tyrosine kinase (BTK), is an effective treatment for relapsed chronic lymphocytic leukaemia (CLL). We investigated the activity and safety of the combination of ibrutinib with the monoclonal antibody rituximab in patients with high-risk CLL. METHODS: In this single-arm phase 2 study, we enrolled adult patients with high-risk CLL at the MD Anderson Cancer Center (Houston, TX, USA). All enrolled participants had high-risk cytogenetic abnormalities (deletion 17p, TP53 mutation, or deletion 11q) or a short progression-free survival (PFS <36 months) after previous first-line chemoimmunotherapy. Patients with symptomatic disease requiring therapy received 28-day cycles of once-daily ibrutinib 420 mg together with rituximab (375 mg/m(2), intravenously, every week during cycle 1, then once per cycle until cycle 6), followed by continuous daily single-agent ibrutinib 420 mg until disease progression or until toxicities or complications precluded further treatment. The primary endpoint was progression-free survival in the intention-to-treat population. This study is registered with ClinicalTrials.gov number NCT01520519, and is no longer accruing patients. FINDINGS: Between Feb 28, 2012, and Sept 11, 2012, we enrolled 40 patients with CLL with high-risk disease features, 20 of whom had deletion 17p (del[17p]) or TP53 mutations (16 previously treated, four untreated), 13 had relapsed CLL with deletion 11q (del[11q]), and seven a PFS less than 36 months after first-line chemoimmunotherapy. 18-month PFS in all patients was 78·0% (95% CI 60·6-88·5), whereas in those with a del(17p) or TP53 mutation it was 72·4% (45·6-87·6) Toxicity was mainly mild to moderate in severity (grade 1-2). Diarrhoea occurred in ten (25%) patients (grade 1 in nine patients and grade 2 in one), bleeding events in 14 (33%) patients (eight grade 1 and five grade 2), nausea or vomiting in 15 patients (38%) (ten grade 1 and five grade 2), and fatigue in seven (18%) patients (four grade 1 and three grade 2). Five patients (13%) had grade 3 infections (two lung infections, one upper respiratory tract infection, one sepsis, and one mucositis), and no grade 4 or 5 infections occurred. One patient had grade 4 neutropenia. INTERPRETATION: The encouraging safety and activity of ibrutinib and rituximab in this population of patients with high-risk CLL merits further investigation of this combination. FUNDING: Pharmacyclics Inc, Cancer Prevention and Research Institute of Texas, Leukemia and Lymphoma Society, National Cancer Institute, MD Anderson Cancer Center.

The biological rationale and clinical efficacy of inhibition of signaling kinases in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is still incurable, with considerable resistance to the standard therapy. CLL cells receive anti-apoptotic and pro-proliferation stimuli in lymph nodes and bone marrow, mainly through B cell receptor activation and TNF-receptor family ligation. In recent years, the focus for finding new drugs has shifted to blocking signals from the microenvironment. Novel therapeutical agents interfere with these microenvironmental interactions, and include inhibitors of kinases Syk, Btk and PI3Kδ. In this review we will focus on the microenvironmental interactions of CLL and the role of tyrosine kinases. Furthermore, early results from clinical trials with kinase inhibitors are discussed.