Chimeric antigen receptors (CARs) have been used to redirect the specificity of autologous T cells against leukemia and lymphoma with promising clinical results. Extending this approach to allogeneic T cells is problematic as they carry a significant risk of graft-versus-host disease (GVHD). Natural killer (NK) cells are highly cytotoxic effectors, killing their targets in a non-antigen-specific manner without causing GVHD. Cord blood (CB) offers an attractive, allogeneic, off-the-self source of NK cells for immunotherapy. We transduced CB-derived NK cells with a retroviral vector incorporating the genes for CAR-CD19, IL-15 and inducible caspase-9-based suicide gene (iC9), and demonstrated efficient killing of CD19-expressing cell lines and primary leukemia cells in vitro, with marked prolongation of survival in a xenograft Raji lymphoma murine model. Interleukin-15 (IL-15) production by the transduced CB-NK cells critically improved their function. Moreover, iC9/CAR.19/IL-15 CB-NK cells were readily eliminated upon pharmacologic activation of the iC9 suicide gene. In conclusion, we have developed a novel approach to immunotherapy using engineered CB-derived NK cells, which are easy to produce, exhibit striking efficacy and incorporate safety measures to limit toxicity. This approach should greatly improve the logistics of delivering this therapy to large numbers of patients, a major limitation to current CAR-T-cell therapies.

Key Points• Human IgM memory B cells possess immunoregulatory properties analogous to transitional B cells.• IL-10-producing B cells are deficient in cGVHD.A subset of regulatory B cells (Bregs) in mice negatively regulate T-cell immune responses through the secretion of regulatory cytokines such as IL-10 and direct cell-cell contact and have been linked to experimental models of autoimmunity, inflammation, and cancer. However, the regulatory function of Bregs in human disease is much less clear.Here we demonstrate that B cells with immunoregulatory properties are enriched within both the CD19 1 IgM 1 CD27 1 memory and CD19 1 CD24 hi CD38 hi transitional B-cell subsets in healthy human donors. Both subsets suppressed the proliferation and interferon-g production of CD3/CD28-stimulated autologous CD4 1 T cells in a dose-dependent manner, and both relied on IL-10 secretion as well as cell-cell contact, likely mediated through CD80 and CD86, to support their full suppressive function. Moreover, after allogeneic stem cell transplantation, Bregs from patients with chronic graft-versus-host disease (cGVHD) were less frequent and less likely to produce IL-10 than were Bregs from healthy donors and patients without cGVHD. These findings suggest that Bregs may be involved in the pathogenesis of cGVHD and support future investigation of regulatory B cell-based therapy in the treatment of this disease. (Blood. 2014;124(13):2034-2045

Summary Multiple myeloma (MM) is a disease with known immune dysregulation. Natural killer (NK) cells have shown preclinical activity in MM. We conducted a first-in-human study of umbilical cord blood-derived (CB) NK cells for MM patients undergoing high dose chemotherapy and autologous haematopoietic stem cell transplantation (auto-HCT). Patients received lenalidomide (10 mg) on days −8 to −2, melphalan 200 mg/m2 on day −7, CB-NK cells on day −5 and auto-HCT on day 0. Twelve patients were enrolled, 3 on each of four CB-NK cell dose levels: 5×106, 1×107, 5×107 and 1×108 CB-NK cells/kg. Ten patients had either high-risk chromosomal changes or a history of relapsed/progressed disease. There were no infusional toxicities and no graft-versus-host disease. One patient failed to engraft due to poor autologous graft quality and was rescued with a back-up autologous graft. Overall, 10 patients achieved at least a very good partial response as their best response, including 8 with near complete response or better. With a median follow-up of 21 months, 4 patients have progressed or relapsed, 2 of whom have died. CB-NK cells were detected in vivo in 6 patients, with an activated phenotype (NKG2D+/NKp30+). These data warrant further development of this novel cellular therapy.

SUMMARY JC virus, the cause of progressive multifocal leukoencephalopathy (PML), and the BK virus are genetically similar and share sequence homology in immunogenic proteins. We treated three immunosuppressed patients with PML with ex vivo- expanded, partially HLA-matched, third-party–produced, cryopreserved BK virus–specific T cells. The immunosuppression in these patients was due to the conditioning regimen for cord-blood transplantation in one patient, a myeloproliferative neoplasm treated with ruxolitinib in another, and acquired immunodeficiency syndrome in the third. After T-cell infusion in two of the patients, alleviation of the clinical signs and imaging features of PML was seen and JC virus in the cerebrospinal fluid (CSF) cleared. The other patient had a reduction in JC viral load and stabilization of symptoms that persisted until her death 8 months after the first infusion. Two of the patients had immune reconstitution syndrome. Donor-derived T cells were detected in the CSF after infusion. (Funded by the M.D. Anderson Cancer Center Moon Shots Program and the National Institutes of Health; ClinicalTrials.gov number, NCT02479698.)

Ibrutinib, a covalent inhibitor of Bruton Tyrosine Kinase (BTK), is approved for treatment of patients with relapsed/refractory or treatment-naïve chronic lymphocytic leukemia (CLL). Besides directly inhibiting BTK, ibrutinib possesses immunomodulatory properties through targeting multiple signaling pathways. Understanding how this ancillary property of ibrutinib modifies the CLL microenvironment is crucial for further exploration of immune responses in this disease and devising future combination therapies. Here, we investigated the mechanisms underlying the immunomodulatory properties of ibrutinib. In peripheral blood samples collected prospectively from CLL patients treated with ibrutinib monotherapy, we observed selective and durable downregulation of PD-L1 on CLL cells by 3 months post-treatment. Further analysis showed that this effect was mediated through inhibition of the constitutively active signal transducer and activator of transcription 3 (STAT3) in CLL cells. Similar downregulation of PD-1 was observed in CD4+ and CD8+ T cells. We also demonstrated reduced interleukin (IL)-10 production by CLL cells in patients receiving ibrutinib, which was also linked to suppression of STAT3 phosphorylation. Taken together, these findings provide a mechanistic basis for immunomodulation by ibrutinib through inhibition of the STAT3 pathway, critical in inducing and sustaining tumor immune tolerance. The data also merit testing of combination treatments combining ibrutinib with agents capable of augmenting its immunomodulatory effects.