Spleen tyrosine kinase inhibition restores myeloid homeostasis in COVID-19

Spleen tyrosine kinase (SYK) is a previously unidentified therapeutic target that inhibits neutrophil and macrophage activation in coronavirus disease 2019 (COVID-19). Fostamatinib, a SYK inhibitor, was studied in a phase 2 placebo-controlled randomized clinical trial and was associated with improvements in many secondary end points related to efficacy. Here, we used a multiomic approach to evaluate cellular and soluble immune mediator responses of patients enrolled in this trial. We demonstrated that SYK inhibition was associated with reduced neutrophil activation, increased circulation of mature neutrophils (CD10⁺CD33^-), and decreased circulation of low-density granulocytes and polymorphonuclear myeloid-derived suppressor cells (HLA-DR^-CD33⁺CD11b^-). SYK inhibition was also associated with normalization of transcriptional activity in circulating monocytes relative to healthy controls, an increase in frequency of circulating nonclassical and HLA-DR^hi classical monocyte populations, and restoration of interferon responses. Together, these data suggest that SYK inhibition may mitigate proinflammatory myeloid cellular and soluble mediator responses thought to contribute to immunopathogenesis of severe COVID-19.

1072. SARS-CoV-2 Antibody Levels Associate with Neutrophil Activation

Background

COVID-19 disease severity and outcomes have been linked to high antibody titers and a dysregulated neutrophil immune response. Here we query associations and connections between the endogenous SARS-CoV-2 antibody response and neutrophil activation in COVID-19.

Methods

Baseline serum or plasma samples from 57 patients hospitalized on oxygen with COVID-19 were used to perform; 1) quantitative measurements of SARS-CoV-2 specific antibodies using a luciferase-based immunoprecipitation system assay, 2) quantitative measurements of neutrophil specific biomarkers using Luminex technology, and 3) neutrophil extracellular traps (NETs) as measured by myeloperoxidase-DNA (MPO-DNA) complexes by ELISA. Absolute neutrophil count (ANC) and immature granulocyte count (IGC) were measured from complete blood counts (CBC). Antibody levels were compared by disease severity using Wilcoxon rank-sum test and correlations were generated between antibody levels and neutrophil activation markers using Spearman’s correlation (SC).

Results

In a cohort of hospitalized patients, severe/critical COVID-19 was associated with higher levels of nucleocapsid-IgA (p=0.011) as well as spike-IgG (p= 0.0007) compared to moderate disease, while spike-IgA and nucleocapsid-IgG showed similar associations, trending towards significance (Figure 1A). Levels of IgG-spike and IgG-nucleocapsid both had significant correlations with the ANC (SC 0.33, p = 0.029; SC 0.38 p = 0.012). All four antibody titers showed strong correlations with IGC, lactoferrin and lipocalin-2, evidence of emergency granulopoiesis. Further, S100A9, a component calprotectin correlated with spike-IgG and nucleocapsid-IgA levels (SC 0.29, p = 0.030, SC 0.29 p = 0.029). Lastly, we found circulating NETs correlated with spike IgA levels (SC 0.38 p = 0.006), and its correlations with IgG-spike and IgA-nucleocapsid additionally approached significance with NETs levels as well (Figure 1B).

Antibody Levels Correlate with Disease Severity and Neutrophil Activation Markers

Figure 1: A) Levels of anti-Spike and anti-Nucleocapsid IgA and IgG levels measured in the serum of 57 unvaccinated hospitalized COVID-19 patients. Moderate illness represents ordinal scale 5 requiring low flow oxygen, while severe/critical patients represent ordinal scale 6 and 7, requiring high flow oxygen, non-invasive or mechanical ventilation, respectively. P values are compared by a Wilcoxon ranked sum test. B) Heatmap showing Spearman correlations between levels of anti-Spike and anti-Nucleocapsid IgA and IgG and markers of neutrophil activation. P values for individual correlations are represented in parentheses. MPO (myeloperoxidase), ANC (absolute neutrophil count), S100A9 (S100 calcium binding protein A9).

Conclusion

Higher anti-spike and anti-nucleocapsid IgG and IgA levels associate with more severe COVID-19 illness. Further, endogenous SARS-CoV-2 specific antibody levels associate with markers of emergency granulopoiesis and neutrophil activation. Inhibiting antibody mediated neutrophil activation may improve outcomes in COVID-19.

Disclosures

All Authors: No reported disclosures.

High-affinity CD16 integration into a CRISPR/Cas9-edited CD38 locus augments CD38-directed antitumor activity of primary human natural killer cells

Background

Adoptive transfer of natural killer (NK) cells with augmented antibody-dependent cellular cytotoxicity (ADCC) capabilities and resistance to CD38 targeting has the potential to enhance the clinical anti-myeloma activity of daratumumab (DARA). Therefore, we sought to develop an efficient CRISPR/Cas9-based gene editing platform to disrupt CD38 expression (CD38 knockout (KO)) in ex vivo expanded NK cells and simultaneously arm CD38^KO NK cells with a high-affinity CD16 (CD16-158V) receptor.

Methods

CD38^KO human NK cells were generated using Cas9 ribonucleoprotein complexes. The platform was expanded by incorporating messenger RNA (mRNA) transfection of CD38^KO NK cells and targeted gene insertion at the CD38 locus to mediate gene knockin (KI). The capacity of these gene-edited NK cells to persist and mediate ADCC in the presence of DARA was tested in vitro and in a MM.1S xenograft mouse model.

Results

Highly efficient CD38 gene disruption was achieved in ex vivo expanded NK cells without affecting their proliferative or functional capacity. CD38 KO conferred resistance to DARA-induced NK cell fratricide, enabling persistence and augmented ADCC against myeloma cell lines in the presence of DARA in vitro and in a MM.1S xenograft mouse model. CD38^KO NK cells could be further modified by transfection with mRNA encoding a CD16-158V receptor, resulting in augmented DARA-mediated ADCC. Finally, we observed that a homology-directed repair template targeted to the CD38 locus facilitated an efficient 2-in-1 CD38 KO coupled with KI of a truncated CD34 reporter and CD16-158V receptor, with CD38^KO/CD16^KI NK cells demonstrating a further enhancement of DARA-mediated ADCC both in vitro and in vivo.

Conclusions

Adoptive immunotherapy using ex vivo expanded CD38^KO/CD16^KI NK cells has the potential to boost the clinical efficacy of DARA. By incorporating complementary genetic engineering strategies into a CD38 KO manufacturing platform, we generated NK cells with substantially augmented CD38-directed antitumor activity, establishing a strong rationale for exploring this immunotherapy strategy in the clinic.

170 Novel gene editing approach to enhance CD38-directed antitumor activity of primary human natural killer cells

Background

Natural killer (NK) cells play an important role in the antitumor responses of therapeutic monoclonal antibodies (mAbs) by mediating antibody-dependent cellular cytotoxicity (ADCC). ADCC occurs when tumor-ligated mAbs trigger NK cell killing by engaging CD16 on NK cells. Further, infusions of ex vivo expanded NK cells to potentiate the antitumor effects of mAbs is a promising immunotherapeutic approach. Daratumumab (DARA) is an anti-CD38 mAb used in the treatment of multiple myeloma (MM) that efficiently induces NK-mediated ADCC. However, CD38 is also expressed on NK cells, which leads to DARA-mediated NK cell destruction and impaired ADCC against MM. Harnessing NK cells to fully exploit the ADCC mechanism of DARA has the potential to improve DARA’s efficacy.

Methods

We developed a novel approach to maximize DARA-mediated ADCC against MM by protecting NK cells from DARA targeting while simultaneously boosting their ADCC capacity. We designed a CRISPR/Cas9-based gene editing platform to couple the disruption of CD38 expression with site-specific insertion of a gene encoding a high-affinity variant of CD16 at the CD38 locus in ex vivo expanded NK cells. To achieve this, we delivered a ribonucleoprotein composed of a single guide RNA and Cas9 nuclease to induce a double strand break within CD38, followed by infection with engineered AAV particles to deliver a homology directed repair template encoding either a truncated CD34 reporter or a FLAG-tagged high-affinity CD16 to be integrated at the site of CD38 gene disruption. Gene editing and insertion efficiency were assessed by flow cytometry for CD38, CD34, and/or FLAG. Transgene integration was confirmed by junction PCR.

Results

High CD38 knockout efficiency was achieved (90.1 ± 4.1%). Using an EF-1 alpha promoter-containing CD34 donor template, stable CD34 expression was seen in 90.2 ± 5.1% NK cells. Insertion of high-affinity CD16, as assessed by FLAG expression, was observed in 47.7 ± 6.1% of edited NK cells. NK cells modified to express high-affinity CD16 also exhibited a higher number of CD16-positive NK cells compared to unedited control NK cells (10.94 ± 1.8%). Functionally, CD38 knockout NK cells expressing high-affinity CD16 demonstrated augmented degranulation in ADCC assays and killing of daratumumab-treated MM cells compared to unedited control and CD38 knockout NK cells.

Conclusions

Novel gene editing techniques can be successfully applied to generate NK cells with enhanced antitumor capabilities. We established an efficient gene editing platform that can be utilized to produce NK cells optimized for adoptive combination with daratumumab.

LIR-1 educates expanded human NK cells and defines a unique antitumor NK cell subset with potent antibody-dependent cellular cytotoxicity

Objective

KIR and NKG2A receptors educate human NK cells to stay responsive to cells with diminished HLA class I. Here, we addressed whether the HLA class I-binding receptor LIR-1 (LILRB1/ILT2/CD85j), which is widely expressed on human NK cells, can mediate education and contribute to antitumor functions of NK cells.

Methods

Healthy donor NK cells either unstimulated, overnight cytokine-activated or ex vivo-expanded were used to target human cell lines. Phenotype and function were analysed using flow cytometry and ⁵¹Cr-release assays.

Results

We found that the inhibitory receptor LIR-1 can mediate NK cell education under specific conditions. This novel finding was exclusive to expanded NK cells and further characterisation of the cells revealed high expression of granzyme B and DNAM-1, which both previously have been linked to NK cell education. Corroborating the rheostat education model, LIR-1 co-expression with an educating KIR further increased the responsiveness of expanded NK cells. Inversely, antibody masking of LIR-1 decreased the responsiveness. LIR-1⁺ expanded NK cells displayed high intrinsic ADCC that, in contrast to KIR and NKG2A, was not inhibited by HLA class I.

Conclusion

These findings identify a unique NK cell subset attractive for adoptive cell therapy to treat cancer. Given that LIR-1 binds most HLA class I molecules, this subset may be explored in both autologous and allogeneic settings to innately reject HLA class I^- tumor cells as well as HLA class I⁺ target cells when combined with antitumor antibodies. Further studies are warranted to address the potential of this subset in vivo.

Fostamatinib for the Treatment of Hospitalized Adults With Coronavirus Disease 2019: A Randomized Trial

BACKGROUND

Coronavirus disease 2019 (COVID-19) requiring hospitalization is characterized by robust antibody production, dysregulated immune response, and immunothrombosis. Fostamatinib is a novel spleen tyrosine kinase inhibitor that we hypothesize will ameliorate Fc activation and attenuate harmful effects of the anti-COVID-19 immune response.

METHODS

We conducted a double-blind, randomized, placebo-controlled trial in hospitalized adults requiring oxygen with COVID-19 where patients receiving standard of care were randomized to receive fostamatinib or placebo. The primary outcome was serious adverse events by day 29.

RESULTS

A total of 59 patients underwent randomization (30 to fostamatinib and 29 to placebo). Serious adverse events occurred in 10.5% of patients in the fostamatinib group compared with 22% in placebo (P = .2). Three deaths occurred by day 29, all receiving placebo. The mean change in ordinal score at day 15 was greater in the fostamatinib group (-3.6 ± 0.3 vs -2.6 ± 0.4, P = .035) and the median length in the intensive care unit was 3 days in the fostamatinib group vs 7 days in placebo (P = .07). Differences in clinical improvement were most evident in patients with severe or critical disease (median days on oxygen, 10 vs 28, P = .027). There were trends toward more rapid reductions in C-reactive protein, D-dimer, fibrinogen, and ferritin levels in the fostamatinib group.

CONCLUSION

For COVID-19 requiring hospitalization, the addition of fostamatinib to standard of care was safe and patients were observed to have improved clinical outcomes compared with placebo. These results warrant further validation in larger confirmatory trials.

CLINICAL TRIALS REGISTRATION

Clinicaltrials.gov, NCT04579393.

Pre-vaccination and early B cell signatures predict antibody response to SARS-CoV-2 mRNA vaccine

SARS-CoV-2 mRNA vaccines are highly effective, although weak antibody responses are seen in some individuals with correlates of immunity that remain poorly understood. Here we longitudinally dissected antibody, plasmablast, and memory B cell (MBC) responses to the two-dose Moderna mRNA vaccine in SARS-CoV-2-uninfected adults. Robust, coordinated IgA and IgG antibody responses were preceded by bursts of spike-specific plasmablasts after both doses, but earlier and more intensely after dose two. Distinct antigen-specific MBC populations also emerged post-vaccination with varying kinetics. We identified antigen non-specific pre-vaccination MBC and post-vaccination plasmablasts after dose one and their spike-specific counterparts early after dose two that correlated with subsequent antibody levels. These baseline and response signatures can thus provide early indicators of serological efficacy and explain response variability in the population.

Combined haploidentical and cord blood transplantation for refractory severe aplastic anaemia and hypoplastic myelodysplastic syndrome

Umbilical cord blood (UCB) transplantation is a potentially curative treatment for patients with refractory severe aplastic anaemia (SAA), but has historically been associated with delayed engraftment and high graft failure and mortality rates. We conducted a prospective phase 2 trial to assess outcome of an allogeneic transplant regimen that co-infused a single UCB unit with CD34⁺ -selected cells from a haploidentical relative. Among 29 SAA patients [including 10 evolved to myelodysplastic syndrome (MDS)] who underwent the haplo cord transplantation (median age 20 years), 97% had neutrophil recovery (median 10 days), and 93% had platelet recovery (median 32 days). Early myeloid engraftment was from the haplo donor and was gradually replaced by durable engraftment from UCB in most patients. The cumulative incidences of grade II-IV acute and chronic graft-versus-host disease (GVHD) were 21% and 41%, respectively. With a median follow-up of 7·5 years, overall survival was 83% and GVHD/relapse-free survival was 69%. Patient- and transplant-related factors had no impact on engraftment and survival although transplants with haplo-versus-cord killer-cell immunoglobulin-like receptor (KIR) ligand incompatibility had delayed cord engraftment. Our study shows haplo cord transplantation is associated with excellent engraftment and long-term outcome, providing an alternative option for patients with refractory SAA and hypoplastic MDS who lack human leucocyte antigen (HLA)-matched donors.

A pilot trial of complement inhibition using eculizumab to overcome platelet transfusion refractoriness in human leukocyte antigen allo-immunized patients

Heavily transfused patients frequently develop human leukocyte antigen (HLA) allo-immunization resulting in platelet transfusion refractoriness and a high risk for life-threatening thrombocytopenia. Data suggest complement activation leading to the destruction of platelets bound by HLA allo-antibodies may play a pathophysiologic role in platelet refractoriness. Here we conducted a pilot trial to investigate the use of eculizumab, a monoclonal antibody that binds and inhibits C5 complement, to treat platelet transfusion refractoriness in allo-immunized patients with severe thrombocytopenia. A single eculizumab infusion was administered to 10 eligible patients, with four (40%) patients overcoming platelet refractories assessed measuring the corrected platelet count increment (CCI) 10-60 min and 18-24 h post transfusion. Responding patients had a reduction in the requirement for subsequent platelet transfusions and had higher post-transfusion platelet increments for 14 days following eculizumab administration. Remarkably, three of the four responders met CCI criteria for response despite receiving HLA-incompatible platelets. Our results suggest that eculizumab has the ability to overcome platelet transfusion refractoriness in patients with broad HLA allo-immunization. This study establishes proof of principle that complement inhibition can treat platelet transfusion refractoriness, laying the foundation for a large multicentre trial to assess the overall efficacy of this approach (ClinicalTrials.gov, identifier: NCT02298933).

In Vivo Tracking of Adoptively Transferred Natural Killer Cells in Rhesus Macaques Using 89Zirconium-Oxine Cell Labeling and PET Imaging

PURPOSE

Trials of adoptive natural killer (NK)-cell immunotherapy for hematologic malignancies have thus far shown only marginal effects, despite the potent in vitro antitumor activity of these cells. Homing of infused cells to tumor microenvironments is critical for efficacy, but has not been well characterized. We established a novel method to track and quantify the distribution of adoptively transferred NK cells using rhesus macaques (RM) as a clinically relevant preclinical model.

EXPERIMENTAL DESIGN

RM NK cells were expanded ex vivo for 14-21 days, labeled with ⁸⁹Zr-oxine complex, and assessed for phenotype, function, and survival. Trafficking of ⁸⁹Zr-labeled ex vivo-expanded NK cells infused into RMs was monitored and quantitated by serial positron emission tomography (PET)/CT (n = 3, 2.05 ± 0.72 MBq, 23.5 ± 2.0 × 10⁶ NK cells/kg) and compared with that of ⁸⁹Zr-labeled nonexpanded NK cells, apoptotic NK cells, and hematopoietic stem and progenitor cells (HSPC).

RESULTS

NK cells retained sufficient levels of ⁸⁹Zr for accurate in vivo tracking for 7 days. ⁸⁹Zr labeling did not alter cellular phenotype, viability, or function. PET/CT showed NK cells initially localized in the lungs, followed by their migration to the liver, spleen, and, at low levels, bone marrow. One day following transfer, only 3.4% of infused NK cells localized to the BM versus 22.1% of HSPCs. No clinical side effects were observed, and dosimetry analysis indicated low organ radioexposures of 6.24 mSv/MBq (spleen) or lower.

CONCLUSIONS

These data support translation of this technique to humans to track the distribution of adoptively infused cells and to develop novel techniques to improve immune cell homing to tumor microenvironments.

Abstract 1434: The Costimulatory Signal Domains 4-1BB and CD3ζ Do Not Improve the Function of CD16A Chimeric Antigen Receptor Transduced NK Cells

Chimeric Antigen Receptors (CAR)-T cells are genetically modified to express an extracellular binding domain, transmembrane domain and intracellular signaling domain. The extracellular binding domain is usually derived from antibodies; however, it can be replaced with other ligand-receptor binding systems, such as with an Fc receptor. CD16A has been tested in second-generation 4-1BB-CD3ζ CAR T cells and NK cell lines (NK-92) and enhances tumor killing; however, it is not clear whether these cells provide superior tumor killing compared to cells modified to express CD16A alone.

In this study, we designed three CAR constructs containing the extracellular binding domain of high affinity mutant CD16A (CD16A-V158) and intracellular signal through 4-1 BB-CD3ζ that differed in leader sequences and transmembrane domains. CAR1 contained the CD16A leader and CD16A transmembrane domain; CAR2 had the CD16A leader and CD8α transmembrane domain; CAR3 contained the CD8α leader and CD8α transmembrane domain. When transduced into Jurkat cells via lentivirus, CD16A V158 and all three CARs showed stable high surface expression of CD16A (> 70%). In contrast, NK-92 cells were only successfully transduced to express CD16 by CD16A V158 (29.8%), CAR2 (42.3%), and CAR3 (42.5%) with no expression of CD16A by CAR1. Transduced cells were sorted by FACs based on CD16A expression. All sorted cells showed >90% stable expression of the constructs for up to 42 days post sorting. We observed a much higher CD16 MFI in cells transduced with CAR2 and CAR3 compared with CD16A V158. Western blotting with anti-CD3ζ identified the full assembly of CARs.

We then tested the function of the transduced cells by a Rituximab binding assay. Although there was no difference in binding to Rituximab at 0.01 and 0.1 mg/mL; CAR2 and CAR3 showed better binding at the 1 and 10 mg/mL. In a 4-hour coculture toxicity assay with 721.221 LCLs, CD16A V158 and CAR3 increased the target lysis by two-fold while CAR2 only showed a 50% increase. When cocultured with 721.221 HLA-E+ LCLs, a 721.221 subclone more resistant to killing by NK-92 cells, we observed similar tumor killing with CD16A V158 and CAR3 (killing doubled) in contrast to CAR2(killing increased by only 50%). We next tested against the B-cell line Raji and found that there was only a mild increase of target lysis with transduced NK-92 cells; however, the CD16A V158 and CAR3 still showed higher toxicity (around a 40% increase).

In summary, CAR2 and CAR3 expressed a higher CD16 MFI in NK cells and demonstrated better binding to Rituximab at1 and 10 mg/mL compared to CD16A V158; however, CAR3 and CD16A V158 had similar killing of target cells that was higher than was observed with CAR2. Our data indicate that NK cells transduced to have a CAR structure combining CD16A with 4-1BB-CD3ζ have augmented ADCC, although this augmentation is not superior to NK cells that are simply transduced to express CD16A alone.

Citation Format: Long Chen, Vicky Li, David Allan, Robert Reger, Elena Cherkasova, Stephanie Pierre, Stefan Barisic, David Granadier, Emily Levy, Giacomo Waller, Susan Doh, Mala Chakraborty, Kate Stringaris, Richard Childs. The Costimulatory Signal Domains 4-1BB and CD3ζ Do Not Improve the Function of CD16A Chimeric Antigen Receptor Transduced NK Cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1434.

Enhanced Bone Marrow Homing of Natural Killer Cells Following mRNA Transfection With Gain-of-Function Variant CXCR4R334X

Adoptive transfer of natural killer (NK) cells can induce remission in patients with relapsed/refractory leukemia and myeloma. However, to date, clinical efficacy of NK cell immunotherapy has been limited to a sub-fraction of patients. Here we show that steps incorporated in the ex vivo manipulation/production of NK cell products used for adoptive infusion, such as over-night IL-2 activation or cryopreservation followed by ex vivo expansion, drastically decreases NK cell surface expression of the bone marrow (BM) homing chemokine receptor CXCR4. Reduced CXCR4 expression was associated with dampened in vitro NK cell migration toward its cognate ligand stromal-derived factor-1α (SDF-1α). NK cells isolated from patients with WHIM syndrome carry gain-of-function (GOF) mutations in CXCR4 (CXCR4^R334X). Compared to healthy donors, we observed that NK cells expanded from WHIM patients have similar surface levels of CXCR4 but have a much stronger propensity to home to BM compartments when adoptively infused into NOD-scid IL2Rgamma^null (NSG) mice. Therefore, in order to augment the capacity of adoptively infused NK cells to home to the BM, we genetically engineered ex vivo expanded NK cells to express the naturally occurring GOF CXCR4^R334X receptor variant. Transfection of CXCR4^R334X-coding mRNA into ex vivo expanded NK cells using a clinically applicable method consistently led to an increase in cell surface CXCR4 without altering NK cell phenotype, cytotoxic function, or compromising NK cell viability. Compared to non-transfected and wild type CXCR4-coding mRNA transfected counterparts, CXCR4^R334X-engineered NK cells had significantly greater chemotaxis toward SDF-1α in vitro. Importantly, expression of CXCR4^R334X on expanded NK cells resulted in significantly greater BM homing following adoptive transfer into NSG mice compared to non-transfected NK cell controls. Collectively, these data suggest up-regulation of cell surface CXCR4^R334X on ex vivo expanded NK cells via mRNA transfection represents a novel approach to improve homing and target NK cell-based immunotherapies to BM where hematological malignancies reside.

Bortezomib sensitizes multiple myeloma to NK cells via ER-stress-induced suppression of HLA-E and upregulation of DR5

Although the proteasome inhibitor bortezomib has significantly improved the survival of patients with multiple myeloma (MM), the disease remains fatal as most patients eventually develop progressive disease. Recent data indicate that MM cells can evade bortezomib-induced cell death by undergoing autophagy as a consequence of endoplasmatic reticulum (ER)-stress induced by proteasome inhibition. Here we show that bortezomib sensitizes MM cells to NK cell killing via two distinct mechanisms: a) upregulation of the TRAIL death receptor DR5 on the surface of MM cells and b) ER-stress induced reduction of cell surface HLA-E. The latter mechanism is completely novel and was found to be exclusively controlled by the inhibitory receptor NKG2A, with NKG2A single-positive (NKG2A^SP) NK cells developing a selective augmentation in tumor killing as a consequence of bortezomib-induced loss of HLA-E on the non-apoptotic MM cells. In contrast, the expression of classical HLA class I molecules remained unchanged following bortezomib exposure, diminishing the augmentation of MM killing by NK cells expressing KIR. Further, we found that feeder cell-based ex vivo expansion of NK cells increased both NK cell TRAIL surface expression and the percentage of NKG2A^SP NK cells compared to unexpanded controls, substantially augmenting their capacity to kill bortezomib-treated MM cells. Based on these findings, we hypothesize that infusion of ex vivo expanded NK cells following treatment with bortezomib could eradicate MM cells that would normally evade killing through proteasome inhibition alone, potentially improving long-term survival among MM patients.

Erratum: iPS-derived MSCs from an expandable bank to deliver a prodrug-converting enzyme that limits growth and metastases of human breast cancers

[This corrects the article DOI: 10.1038/cddiscovery.2016.64.].

Checkpoint Inhibition of KIR2D with the Monoclonal Antibody IPH2101 Induces Contraction and Hyporesponsiveness of NK Cells in Patients with Myeloma

PURPOSE

Immune checkpoint inhibitors have recently revolutionized cancer immunotherapy. On the basis of data showing KIR-ligand mismatched natural killer (NK) cells reduce the risk of leukemia and multiple myeloma relapse following allogeneic hematopoietic stem cell transplantation, investigators have developed a checkpoint inhibition antibody that blocks KIR on NK cells. Although in vitro studies suggest the KIR2D-specific antibody IPH2101 induces KIR-ligand mismatched tumor killing by NK cells, our single-arm phase II clinical trial in patients with smoldering multiple myeloma was prematurely terminated due to lack of clinical efficacy. This study aimed at unveiling the underlying mechanisms behind the lack of clinical efficacy.

EXPERIMENTAL DESIGN

Treatment-naïve patients received an intravenous infusion of 1 mg/kg IPH2101 every other month for up to a year. Peripheral blood was collected at baseline and 24 hours after first infusion, followed by weekly samples for the first month and monthly samples thereafter. NK cell phenotype and function was analyzed using high-resolution flow cytometry.

RESULTS

Unexpectedly, infusion of IPH2101 resulted in rapid reduction in both NK cell responsiveness and KIR2D expression on the NK cell surface. In vitro assays revealed KIR2D molecules are removed from the surface of IPH2101-treated NK cells by trogocytosis, with reductions in NK cell function directly correlating with loss of free KIR2D surface molecules. Although IPH2101 marginally augmented the antimyeloma cytotoxicity of remaining KIR2D^dull patient NK cells, the overall response was diminished by significant contraction and reduced function of KIR2D-expressing NK cells.

CONCLUSIONS

These data raise concerns that the unexpected biological events reported in this study could compromise antibody-based strategies designed at augmenting NK cell tumor killing via checkpoint inhibition. Clin Cancer Res; 22(21); 5211-22. ©2016 AACRSee related commentary by Felices and Miller, p. 5161.

Effect of high-dose plerixafor on CD34+ cell mobilization in healthy stem cell donors: results of a randomized crossover trial

Hematopoietic stem cells can be mobilized from healthy donors using single-agent plerixafor without granulocyte colony-stimulating factor and, following allogeneic transplantation, can result in sustained donor-derived hematopoiesis. However, when a single dose of plerixafor is administered at a conventional 240 μg/kg dose, approximately one-third of donors will fail to mobilize the minimally acceptable dose of CD34⁺ cells needed for allogeneic transplantation. We conducted an open-label, randomized trial to assess the safety and activity of high-dose (480 μg/kg) plerixafor in CD34⁺ cell mobilization in healthy donors. Subjects were randomly assigned to receive either a high dose or a conventional dose (240 μg/kg) of plerixafor, given as a single subcutaneous injection, in a two-sequence, two-period, crossover design. Each treatment period was separated by a 2-week minimum washout period. The primary endpoint was the peak CD34⁺ count in the blood, with secondary endpoints of CD34⁺ cell area under the curve (AUC), CD34⁺ count at 24 hours, and time to peak CD34⁺ following the administration of plerixafor. We randomized 23 subjects to the two treatment sequences and 20 subjects received both doses of plerixafor. Peak CD34⁺ count in the blood was significantly increased (mean 32.2 versus 27.8 cells/μL, P=0.0009) and CD34⁺ cell AUC over 24 hours was significantly increased (mean 553 versus 446 h cells/μL, P<0.0001) following the administration of the 480 μg/kg dose of plerixafor compared with the 240 μg/kg dose. Remarkably, of seven subjects who mobilized poorly (peak CD34⁺ ≤20 cells/μL) after the 240 μg/kg dose of plerixafor, six achieved higher peak CD34⁺ cell numbers and all achieved higher CD34⁺ AUC over 24 hours after the 480 μg/kg dose. No grade 3 or worse drug-related adverse events were observed. This study establishes that high-dose plerixafor can be safely administered in healthy donors and mobilizes greater numbers of CD34⁺ cells than conventional-dose plerixafor, which may improve CD34⁺ graft yields and reduce the number of apheresis procedures needed to collect sufficient stem cells for allogeneic transplantation. (ClinicalTrials.gov, identifier: NCT00322127)

Efficient mRNA-Based Genetic Engineering of Human NK Cells with High-Affinity CD16 and CCR7 Augments Rituximab-Induced ADCC against Lymphoma and Targets NK Cell Migration toward the Lymph Node-Associated Chemokine CCL19

For more than a decade, investigators have pursued methods to genetically engineer natural killer (NK) cells for use in clinical therapy against cancer. Despite considerable advances in viral transduction of hematopoietic stem cells and T cells, transduction efficiencies for NK cells have remained disappointingly low. Here, we show that NK cells can be genetically reprogramed efficiently using a cGMP-compliant mRNA electroporation method that induces rapid and reproducible transgene expression in nearly all transfected cells, without negatively influencing their viability, phenotype, and cytotoxic function. To study its potential therapeutic application, we used this approach to improve key aspects involved in efficient lymphoma targeting by adoptively infused ex vivo-expanded NK cells. Electroporation of NK cells with mRNA coding for the chemokine receptor CCR7 significantly promoted migration toward the lymph node-associated chemokine CCL19. Further, introduction of mRNA coding for the high-affinity antibody-binding receptor CD16 (CD16-158V) substantially augmented NK cell cytotoxicity against rituximab-coated lymphoma cells. Based on these data, we conclude that this approach can be utilized to genetically modify multiple modalities of NK cells in a highly efficient manner with the potential to improve multiple facets of their in vivo tumor targeting, thus, opening a new arena for the development of more efficacious adoptive NK cell-based cancer immunotherapies.

Transcriptional terminators of RNA polymerase II are associated with yeast replication origins

The compact organization of the Saccharomyces cerevisiae genome necessitates that non-coding regulatory sequences reside in close proximity to one another. Here we show there is an intimate association between transcription terminators and DNA replication origins. Four replication origins were analyzed in a reporter gene assay that detects sequences that direct 3' end formation of mRNA transcripts. All four replication origins function as orientation-independent transcription terminators in this system, producing truncated polyadenylated mRNAs. Despite this close association, the cis-acting elements that confer replication origin function are genetically separable from those required for transcription termination. Several models are explored in an attempt to address how and why the signals specifying transcription termination and replication initiation overlap.

The incidence and progression of pneumoconiosis over nine years in U.S. coal miners: I. Principal findings

Chest radiographs, taken at a 9-year interval for 1,261 U.S. coal miners, were read for pneumoconiosis side-by-side by six readers in a controlled trial. Incidence and progression of small, rounded opacities were consistent with levels predicted from dose-response curves developed by the British Pneumoconiosis Field Research interpolated at a concentration derived from U.S. compliance levels mandated over the last 9 years. The results imply that the level of pneumoconiosis in U.S. miners is being reduced through application of the current 2 mg/m3 standard. The long developmental period for pneumoconiosis necessitates that further study be undertaken to verify this finding and to determine whether 2 mg/m3 is an appropriate regulatory dust level for the prevention of category 2 or greater simple pneumoconiosis over a 35-year period.

The incidence and progression of pneumoconiosis over nine years in U.S. coal miners: II. Relationship with dust exposure and other potential causative factors

Examination of the incidence and progression of pneumoconiosis over 9 years in 1,261 nationally distributed U.S. coal miners has been undertaken in relationship to potential causative factors. Use has been made of a large body of data on dust levels collected by the Mine Safety and Health Administration principally for compliance purposes. Reported dust levels were low and generally under the current 2 mg/m3 standard. No link between dust level and disease progression could be detected. Some evidence was seen that radiological change was related to dust exposures prior to the study in both coal and noncoal mines, and thus experienced before the current dust standards were mandated. Neither migration of miners nor mining method appeared to be associated with disease incidence or progression. None of these findings can be taken as final, as the period of study is short and the number of cases of pneumoconiosis few. Further study is under way to obtain more reliable information over a longer period of follow-up.

Occupational safety and health implications of increased coal utilization

An area of major concern in considering increased coal production and utilization is the health and safety of increased numbers of workers who mine, process, or utilize coal. Hazards related to mining activities in the past have been especially serious, resulting in many mine related accidental deaths, disabling injuries, and disability and death from chronic lung disease. Underground coal mines are clearly less safe than surface mines. Over one-third of currently employed underground miners experience chronic lung disease. Other stresses include noise and extremes of heat and cold. Newly emphasized technologies of the use of diesel powered mining equipment and the use of longwall mining techniques may be associated with serious health effects. Workers at coal-fired power plants are also potentially at risk of occupational diseases. Occupational safety and health aspects of coal mining are understood well enough today to justify implementing necessary and technically feasible and available control measures to minimize potential problems associated with increased coal production and use in the future. Increased emphasis on safety and health training for inexperienced coal miners expected to enter the work force is clearly needed. The recently enacted Federal Mine Safety and Health Act of 1977 will provide impetus for increased control over hazards in coal mining.

Small airways disease in coal miners. A longitudinal study

Seventeen of an original cohort of 25 non-smoking working coal miners and 6 age-matched controls studied in 1969 were re-examined in 1973. Measurements included lung volumes, maximal expiratory flow-volume curves, and closing volumes. Miners, when compared with controls, showed a marked decline in maximal expiratory flow at mid-vital capacity (V 50%) over the 4-year period which took place without significant change in the 1-second forced expiratory volume (FEV1). Frequency dependence of dynamic compliance (Cdyn) in association with an increased upstream airways resistance (Rus), and also loss of lung elastic recoil (PL(St)) which were present at the time of the original study led to similar declines in V 50%. An abnormally elevated closing capacity expressed as a percentage of total lung capacity (CC/TLC)% was found in 9 miners (53%) and none of the controls. Closing volume as a percentage of vital capacity (CV/VC)% was abnormal in 4 miners (23.5)% and no controls. Measurement of closing volume did not relate well to the variety of mechanical abnormality present on the original study; namely, loss of recoil or small airways obstruction. The presence of an elevated (CC/TLC)% and (CV/VC)% correlated mainly with the presence of hyperinflation as indicated by an elevated residual volume.

Polyvinyl chloride pyrolysis products. A potential cause for respiratory impairment

A limited investigation of respiratory and other symptom prevalence, plus before and after shift ventilatory capacity was conducted among a group of 17 meat wrappers exposed to pyrolysis products of polyvinyl chloride and a group of 21 control subjects. Exposed meat wrappers showed a higher prevalence of cough, phlegm, hay fever, and asthma than did the control group. The exposed group also demonstrated relative decreases in forced expiratory volume, one second (FEV1.0) and forced expiratory flow 50% (FEF50) after one shift of work; whereas, the controls showed an opposite tendency. These findings suggest that meat wrappers exposed to pyrolysis products of polyvinyl chloride might be adversely affected. The results, while suggestive, are not totally conclusive owing to the fact that there was not ideal matching of the exposed and control groups in regard to age, height, race, sex, and smoking status.

Determination of lung volumes from chest films

The results obtained from two radiological methods of determining total lung capacity (TLC) (Kovach's parabo oid and Barnhard's ellipsoid) were compared with those obtained with the body plethysmograph. Determinations of TLC were made in four groups of subjects: group 1 consisted of 26 miners most of whom had simple pneumoconiosis; group 2 consisted of 12 normal subjects; group 3 consisted of eight subjects who had a variety of chest disease, but with no demonstrable parenchymal or pleural opacification; and group 4 consisted of 19 subjects with miscellaneous diseases, all showing demonstrable infiltration or opacification.

The values obtained by the method of Kovach and his colleagues often differed markedly from the plethysmographic determinations, and it became apparent that this method was not sufficiently accurate. On the other hand, the technique of Barnhard and his colleagues gave results that were essentially similar to, and as far as we can say interchangeable with, those obtained by the body plethysmograph in groups 1, 2, and 3. In subjects with marked pulmonary opacification or infiltration, the disparity between Barnhard's method and the plethysmograph tended to be more sizeable. It was concluded that Barnhard's method for determining total lung capacity is accurate and could be applied to epidemiological surveys.