Key Points Ibrutinib is the first clinically viable irreversible ITK inhibitor. Ibrutinib inhibits the formation of Th2 but not Th1 immunity.

BACKGROUND.Ibrutinib has been shown to have immunomodulatory effects by inhibiting Bruton's tyrosine kinase (BTK) and IL-2-inducible T cell kinase (ITK). The relative importance of inhibiting these 2 kinases has not been examined despite its relevance to immune-based therapies. METHODS.Peripheral blood mononuclear cells from chronic lymphocytic leukemia (CLL) patients on clinical trials of ibrutinib (BTK/ITK inhibitor; n = 19) or acalabrutinib (selective BTK inhibitor; n = 13) were collected serially. T cell phenotype, immune function, and CLL cell immunosuppressive capacity were evaluated. RESULTS. Ibrutinib markedly increased CD4+ and CD8 + T cell numbers in CLL patients. This effect was more prominent in effector/effector memory subsets and was not observed with acalabrutinib. Ex vivo studies demonstrated that this may be due to diminished activation-induced cell death through ITK inhibition. PD-1 and CTLA-4 expression was significantly markedly reduced in T cells by both agents. While the number of Treg cells remained unchanged, the ratio of these to conventional CD4 + T cells was reduced with ibrutinib, but not acalabrutinib. Both agents reduced expression of the immunosuppressive molecules CD200 and BTLA as well as IL-10 production by CLL cells. CONCLUSIONS. Ibrutinib treatment increased the in vivo persistence of activated T cells, decreased the Treg/CD4+ T cell ratio, and diminished the immune-suppressive properties of CLL cells through BTK-dependent and -independent mechanisms. These features provide a strong rationale for combination immunotherapy approaches with ibrutinib in CLL and other cancers. TRIAL REGISTRATION. ClinicalTrials.gov NCT01589302 and NCT02029443. Samples described here were collected per OSU-0025.

Key Points Ibrutinib treatment of CLL enhances the generation of CAR T cells for adoptive immunotherapy. Concurrent ibrutinib therapy improves the engraftment and therapeutic efficacy of anti-CD19 CAR T cells in mouse models.

Spinal cord injury (SCI) activates macrophages, endowing them with both reparative and pathological functions. The mechanisms responsible for these divergent functions are unknown but are likely controlled through stochastic activation of different macrophage receptor subtypes. Various danger-associated molecular patterns released from dying cells in the injured spinal cord likely activate distinct subtypes of macrophage pattern recognition receptors, including bacterial toll-like receptors (TLRs) and fungal C-type lectin receptors (e.g., dectin-1). To determine the in vivo consequences of activating these receptors, ligands specific for TLR2 or dectin-1 were microinjected, alone or in combination, into intact spinal cord. Both ligands elicit a florid macrophage reaction; however, only dectin-1 activation causes macrophage-mediated demyelination and axonal injury. Coactivating TLR2 reduced the injurious effects of dectin-1 activation. When injected into traumatically injured spinal cord, TLR2 agonists enhance the endogenous macrophage reaction while conferring neuroprotection. Indeed, dieback of axons was reduced, leading to smaller lesion volumes at the peak of the macrophage response. Moreover, the density of NG2ϩ cells expressing vimentin increased in and near lesions that were enriched with TLR2-activated macrophages. In dectin-1-null mutant (knock-out) mice, dieback of corticospinal tract axons also is reduced after SCI. Collectively, these data support the hypothesis that the ability of macrophages to create an axon growth-permissive microenvironment or cause neurotoxicity is receptor dependent and it may be possible to exploit this functional dichotomy to enhance CNS repair.

• Selinexor exhibits synergy with ibrutinib in CLL.• Selinexor is effective in vitro in ibrutinib-resistant CLL.Despite the therapeutic efficacy of ibrutinib in chronic lymphocytic leukemia (CLL), complete responses are infrequent, and acquired resistance to Bruton agammaglobulinemia tyrosine kinase (BTK) inhibition is being observed in an increasing number of patients. Combination regimens that increase frequency of complete remissions, accelerate time to remission, and overcome single agent resistance are of considerable interest. We previously showed that the XPO1 inhibitor selinexor is proapoptotic in CLL cells and disrupts B-cell receptor signaling via BTK depletion. Herein we show the combination of selinexor and ibrutinib elicits a synergistic cytotoxic effect in primary CLL cells and increases overall survival compared with ibrutinib alone in a mouse model of CLL. Selinexor is effective in cells isolated from patients with prolonged lymphocytosis following ibrutinib therapy. Finally, selinexor is effective in ibrutinib-refractory mice and in a cell line harboring the BTK C481S mutation. This is the first report describing the combined activity of ibrutinib and selinexor in CLL, which represents a new treatment paradigm and warrants further evaluation in clinical trials of CLL patients including those with acquired ibrutinib resistance. (Blood. 2015;125(20):3128-3132) IntroductionChronic lymphocytic leukemia (CLL) is a lymphoid malignancy of clonal B cells that exhibit aberrant activation of the B-cell receptor (BCR) signaling pathway. A critical component of this pathway is Bruton agammaglobulinemia tyrosine kinase (BTK), a nonreceptor tyrosine kinase expressed predominantly in B lymphocytes.3 Ibrutinib, which irreversibly binds and inhibits BTK activity, has shown promising results in CLL, mantle cell lymphoma, and a subset of diffuse large B-cell lymphoma driven by BCR signaling.4-6 Despite encouraging results, complete responses are infrequent.7 Additionally, acquired resistance to ibrutinib represents an important clinical challenge wherein no standard treatment approach currently exists. Mechanisms of ibrutinib resistance were elucidated by our group and others and involve mutations at the C481S site of BTK or in the immediate downstream target, PLCg2. 1,2,8 Exportin-1 (CRM1/XPO1) is the sole nuclear exporter of tumor suppressor proteins such as p53, inhibitory nuclear factor-kB, and FOXO3a.9,10 Selective inhibitors of nuclear export (SINEs) inhibit XPO1 and restore subcellular localization of dysregulated molecules. Our previous published work showed XPO1 is a therapeutic target for CLL 11 and has facilitated translation of selinexor, a SINE, to a phase 1 clinical trial (#NCT01607892), where antitumor activity has been observed in lymphoma, 12 CLL, 12 multiple myeloma, 13 and acute myeloid leukemia.14 We recently showed that selinexor inhibits activation of downstream BCR targets such as extracellular signal-regulated kinase and protein kinase B and suppresses BTK gene expression. 15 Based on t...