Venetoclax Enhances the Efficacy of Therapeutic Antibodies in B-Cell Malignancies

Abstract The application of antibodies is a promising option in the treatment of B-cell malignancies, including acute lymphoblastic leukemia (ALL) and B-cell Non-Hodgkin lymphoma (B-NHL). Although patient outcomes have improved by applying combinations of chemotherapy and antibodies, certain patients characterized by a high expression of anti-apoptotic Bcl-2 have a poor prognosis. These include adult B-NHL patients with "double-hit lymphomas" (DHLs) and pediatric ALL patients harboring a t(17;19) translocation. Furthermore, a substantial number of Burkitt´s lymphoma (BL) patients also express Bcl-2 even though the impact of this finding on prognosis is yet unclear. Here, we examine the role of low doses of the Bcl-2 inhibitor venetoclax (VTX, 1nM) on the efficacy of the therapeutic antibodies rituximab (CD20), daratumumab (CD38) and CD19-DE (a variant of the CD19 antibody MOR208 engineered for improved effector cell binding). Natural killer (NK)-cell mediated antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cell-mediated phagocytosis (ADCP) were evaluated. The CD20-expressing DHL cell line Carnaval and patient-derived xenograft (PDX) cells from two BL patients were used as target cells for rituximab, the CD20-negative/CD38-positive DHL cell line Will-2 was used with daratumumab and three PDX samples from t(17;19) positive ALL patients were used with CD19-DE. For the assessment of ADCP, human monocyte-derived macrophages were incubated with labelled target cells and microscopy assays were performed. NK-cell mediated ADCC was not enhanced by VTX in any of our models. However, 17-37% increases in ADCP by macrophages were detected when Carnaval cells were subjected to combinations of VTX/rituximab and when Will-2 cells were treated with VTX/daratumumab as compared to VTX or antibody alone (p=0.0318/p=0.0185 and p=0.0012/p=0.0068, respectively, Figure A). When BL PDX cells were subjected to ADCP assays with VTX/rituximab, mean phagocytosis levels were also enhanced by 26.0% and 21.0% in the combination treatment group as compared to VTX (p=0.0283) and rituximab alone (p=0.0282; Figure A). ADCP assays with t(17;19) positive ALL-PDX cells and CD19-DE confirmed these results as phagocytosis was increased to similar extents in the combination group as compared to VTX (p=0.0017) or CD19-DE alone (p=0.0323) (Figure A/B). In order to exclude that our observations were due to an enhancement of apoptosis in target cells only, we measured cleaved caspase-3 with VTX, antibodies alone or the combination of both. Cleaved caspase-3 levels were equal in all groups suggesting that the addition of VTX resulted in an apoptosis-independent activation of macrophages. In order to minimize heterogeneity in ADCP assays, phagocytosis was next examined using expanded macrophages from NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice for our assays. Regardless of target cells and antibody, the combination of antibody treatment with VTX resulted in enhanced phagocytosis by murine macrophages, confirming our results. The effects of VTX on the efficacy of rituximab were finally examined in vivo. Carnaval cells were injected intravenously into NSG mice and animals treated with VTX (100 mg/kg 5 days/week by oral gavage), rituximab alone (1 mg/kg once weekly intraperitoneally) or the combination of both (n=6/group). Mice were sacrificed when mice showed clinical lymphoma or leukemia engraftment and survival differences were assessed using Kaplan-Meier log-rank statistics. Compared to control, mice treated with VTX displayed a slight survival advantage, which was more marked in mice treated with rituximab (p=0.0020/p=0.0004, respectively, Figure C), suggesting a better efficacy of rituximab than VTX as monotherapy. Most importantly, mice treated with the combination VTX/rituximab showed significantly superior survival as compared to either VTX or rituximab alone (p=0.0023/p=0.0268, respectively, Figure C), suggesting additive effects in vivo. Altogether, we show that VTX enhances the efficacy of therapeutic antibodies in models of B-cell malignancies including PDX samples. The mechanism is most likely dependent on distinct influences of VTX on macrophage activation, e. g. by myeloid immune checkpoints. Our in vivo data suggest that this combination strategy may become a promising therapeutic option for the treatment of Bcl-2 expressing B-cell malignancies in the future. Figure. Figure. Disclosures Bourquin: Amgen: Other: Travel Support. Valerius:Affimed: Research Funding. Peipp:Affimed: Research Funding.

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NK Cell Line Killing of Leukemia Cells Is Enhanced By Reverse Antibody Dependent Cell Mediated Cytotoxicity (R-ADCC) Via NKp30 and NKp44 and Target Fcγ Receptor II (CD32)

Blood ◽

10.1182/blood.v124.21.2444.2444 ◽

2014 ◽

Vol 124 (21) ◽

pp. 2444-2444 ◽

Cited By ~ 1

Author(s):

Brent A. Williams ◽

Xinghua Wang ◽

Bertrand Routy ◽

Richard Cheng ◽

Sonam Maghera ◽

...

Keyword(s):

Esophageal Cancer ◽

Cell Line ◽

Cell Lines ◽

Nk Cell ◽

P Value ◽

Fcγ Receptor ◽

Isotype Control ◽

Nsg Mice ◽

Dependent Cell

Abstract Introduction: We are studying NK cell immunotherapy to treat acute myeloid leukemia (AML) and have focused on NK-92 and KHYG-1, CD16(-) human malignant NK cell lines. Phase I NK-92 trials show minimal toxicity; KHYG-1 has not been tested in humans. Here, we investigated modulation of cytotoxicity of NK cell lines against primary AML blasts and cell lines with monoclonal antibodies (mAb) directed against natural cytotoxicity receptors. Methods: NK cytotoxicity was assessed with a standard 4 hour Cr51 release assay at an effector to target (E:T) ratio of 10:1. NK lines were incubated with and without isotype control and mAbs against NKp30, NKp44 at various doses (0.001-10 µg/ml) for 1 hour and washed with medium prior to cytotoxicity assays. The student’s t-test was used to compare cytotoxicity data. Target cells were incubated with 100 µCi Cr51 and cell supernatants assayed on a gamma counter. NK targets (leukemic and esophageal cancer) were evaluated for Fcγ receptor expression by flow cytometry. To test the cytotoxic effect on in vivo proliferation, OCI/AML5 cells were co-incubated with irradiated KHYG-1 (iKHYG-1) +/-1 µg/ml NKp30 pretreatment for 4 hours at a 10:1 E:T ratio and injected ip into NOD/SCID gamma null (NSG) mice with survival as an endpoint analyzed with the log rank test. Results: NK-92 and KHYG-1 were both highly cytotoxic against K562 with moderate killing of OCI/AML3 and KG1 and KG1a. OCI/AML5 was highly sensitive to killing by NK-92, but resistant to KHYG-1. Pretreatment of NK-92 with mAbs against NKp30, NKp44 (10 µg/ml) yielded small increases in cytotoxicity against leukemic cell lines with NKp30 pretreatment only. Pretreatment of KHYG-1 with 10 µg/ml of anti-NKp30 or anti-NKp44 mediated fold increases in cytotoxicity above isotype control against 4 leukemia cell line targets and 4 primary AML samples (Table1). Anti-NKp30 and anti-NKp44 pretreatment of NK-92 and KHYG-1 did not enhance killing of a panel of esophageal cancer cell lines. Immunophenotyping cancer cell lines showed high expression of Fcγ receptor II (CD32), but very low expression of Fcγ receptor I (CD64) or III (CD16) on leukemia lines (K562, OCI/AML3, OCI/AML5, KG1 and KG1a), and no expression of Fcγ receptors on esophageal lines (OE-33, FLO-1, KYAE-1, SKGT-4). Regression analysis of the relationship between cytotoxic enhancement and CD32 expression of targets revealed a strong correlation for NKp30 (p<0.01; R2=0.71) and NKp44 (p<0.01; R2=0.64) pretreated KHYG-1. NSG mice injected with 2x106 OCI/AML5 cells developed progressive malignant ascites at 9 weeks requiring sacrifice, unaffected by iKHYG-1 (p=0.92). However, NKp30 pretreated iKHYG-1 improved survival versus no therapy (p<0.05) or iKHYG-1 (p<0.05) cohorts. Conclusion: We show a novel means to enhance cytotoxicity of NK cell lines many fold against primary AML cells by pretreatment with mAbs against NKp30 and NKp44. The mechanism of enhanced KHYG-1 cytotoxicity is from bound NKp30 or NKp44 becoming crosslinked when the Fc portion binds the Fcγ receptor II (CD32) on targets. This is the first demonstration of reverse antibody-dependent cell-mediated cytotoxicity (R-ADCC) with a NK cell line leading to enhanced killing of AML primary blasts in vitro and the first demonstration of R-ADCC in an in vivo model. Table 2: Effect of NKp30 or NKp44 pretreatment on KHYG-1 cytotoxicity against primary AML samples Fold lysis and p values Primary AML samples 5890 080078 0909 080179 Fold change lysis NKp30 1.7 15.7 2.7 4.9 Fold change lysis NKp44 0.9 16.3 2.8 6.2 p value NKp30 <0.05 =0.0001 <0.0001 <0.001 p value NKp44 0.9 <0.001 <0.001 <0.001 Disclosures No relevant conflicts of interest to declare.

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Engineered Interleukin-15 Autocrine Signaling Invigorates Anti-CD123 CAR-NK Cells

Blood ◽

10.1182/blood-2021-146609 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2806-2806

Author(s):

Ilias Christodoulou ◽

Michael Koldobskiy ◽

Won Jin Ho ◽

Andrew Marple ◽

Wesley J. Ravich ◽

...

Keyword(s):

Nk Cells ◽

Peripheral Blood ◽

Research Funding ◽

Nk Cell ◽

Xenograft Model ◽

Blood Analysis ◽

Target Cells ◽

Interleukin 15 ◽

Peripheral Blood Analysis

Abstract Introduction : Acute Myeloid Leukemia (AML) is an aggressive neoplastic disorder with poor outcomes in children and adults. NK cell adoptive transfer is an anti-cancer immunotherapy that has promise for AML treatment. We aimed to improve NK cell anti-tumor efficacy with expression of a Chimeric Antigen Receptor (CAR) on the cell surface. Our CAR consists of an extracellular single-chain variable fragment targeting the AML-associated antigen CD123 (IL3Rα) and intracellular domains derived from 2B4 and TCRζ. We sought to improve the persistence and long-term functionality of our CAR-NKs by introducing transgenic interleukin-15 (IL15). Methods: CD3-depleted PBMCs were first activated with lethally irradiated feeder cells, then transduced with transiently produced replication incompetent γ-retrovirus (αCD123.2B4.ζ, αCD123.2B4.ζ-IRES-sIL15, sIL15-IRES-mOrange) on day 4 of culture. CAR expression was measured on day 8 using FACS. Secretion of IL15 was verified with ELISA. Cytotoxicity was measured using ffLuc expressing target cells and bioluminescence (BL) measurement. In serial stimulation assays, target cells were repleted daily to maintain a 1:1 effector:target ratio. Immunophenotype and cell counts were assessed by FACS. Transcriptomic analysis (RNAseq) was performed on RNA derived from NK cells purified on D10. Xenograft modeling was performed using NSG mice engrafted with MV-4-11.ffLuc or MOLM-13.ffLuc AML cell lines. Mice were treated with NK cells on D4 or D4-7-10. Untreated mice served as controls. Tumor growth was serially tracked in vivo using BL imaging. NK cell persistence and expansion were measured in peripheral blood. Results: The 2B4.ζ CAR was well expressed on the surface of transduced NK cells (median transduction efficiency 95%, range 85-97%, n=3). 2B4.ζ CAR-NK treatment prolonged survival of AML engrafted mice when compared to treatment with unmodified NKs (median survival: 63 vs 55 days; n=8 mice; p=0.014). Serial peripheral blood analysis revealed a steady decline in circulating NK cells, which were undetectable in all cohorts within 21 days. NK cells were then engineered for constitutive secretion of IL15, with and without CAR expression. 2B4.ζ/sIL15 CAR-NKs had the most potent 24h-cytotoxicity against CD123+ targets (Fig. 1). After a 10-day chronic stimulation with MV-4-11, 2B4.ζ/sIL15- and sIL15-NKs expanded (x1.2 and x5.9 respectively), while NK cells without sIL15 decreased in number. In this assay, only 2B4.ζ/sIL15 CAR-NKs exhibited sustained tumor killing. Transcriptomic analysis after 10 days of serial stimulation showed sample clustering dependent on IL15 secretion. Differential gene expression analysis (DESeq2) identified upregulation of genes associated with cell cycle progression, apoptosis regulation, chemokine signaling, and NK cell mediated cytotoxicity in NK cells secreting IL15 compared to those without. In multiparameter flow cytometric analysis, 2B4.ζ/sIL15 CAR-NKs had a higher percentage of NK cells populating clusters defined by higher surface expression of NK cell activating receptors (NKp30, NKG2D, LFA-1) compared to 2B4.ζ and unmodified NK cells. In our MV-4-11 xenograft model, NKs armed with secreted IL15 expanded in vivo and had improved persistence. A single dose (D4) of 2B4.ζ/sIL15 CAR-NKs demonstrated an initial antitumor response, equivalent to that seen following 3 doses (D4-7-10) of 2B4.ζ CAR-NKs. However, mice treated with IL15-secreting NKs had short survival (Fig. 2). Compared to control mice, peripheral blood analysis showed increasing systemic hIL15 and higher levels of hTNFα. In our more aggressive MOLM-13 xenograft model, both single dose 2B4.ζ/sIL15 CAR-NK and multiple dose 2B4.ζ CAR-NK treatment prolonged survival compared to treatment with unmodified NKs. (27 and 26 vs 20 days; n=5 mice; p<0.01; Fig. 2). Conclusion: 2B4.ζ CAR-NKs have limited antitumor efficacy and short persistence in vivo. NK cells armored with secreted IL15 have enhanced anti-AML cytotoxicity and in vitro persistence. Introduction of IL15 secretion confers a distinctly activated phenotype that is maintained during chronic antigen stimulation. Constitutive local IL15 secretion improves in vivo NK cell persistence but may cause lethal toxicity when employed against AML. These results warrant further study and should impact the development of CAR-NK clinical products for patients with AML. Figure 1 Figure 1. Disclosures Ho: Rodeo Therapeutics/Amgen: Patents & Royalties; Exelixis: Consultancy; Sanofi: Research Funding. Bonifant: Kiadis Pharma: Research Funding; BMS: Research Funding; Merck, Sharpe, Dohme: Research Funding.

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The JAK Inhibitor Ruxolitinib Substantially Affects NK Cells in MPN Patients

Blood ◽

10.1182/blood.v124.21.3169.3169 ◽

2014 ◽

Vol 124 (21) ◽

pp. 3169-3169

Author(s):

Kathrin Schönberg ◽

Janna Rudolph ◽

Maria Vonnahme ◽

Isabelle Cornez ◽

Sowmya Parampalli Yajnanarayana ◽

...

Keyword(s):

Nk Cells ◽

Research Funding ◽

Nk Cell ◽

Receptor Expression ◽

Target Cells ◽

Jak Inhibitor ◽

Advisory Committees ◽

Nk Cell Differentiation

Abstract Introduction: Ruxolitinib (INCB018424) is the first JAK inhibitor approved for treatment of myelofibrosis (MF). Ruxolitinib-induced reduction of splenomegaly and symptoms control is linked to a substantial suppression of MF-associated circulating pro-inflammatory and pro-angiogenic cytokines. However, an increased rate of infections in ruxolitinib-exposed patients with MF was recently described. Natural killer (NK) cells are innate immune effector cells eliminating malignant or virus-infected cells. Thus, the aim of this project was to define in more detail the impact of JAK inhibition on NK cell biology both in vitro and in vivo. Methods: 28 patients with myeloproliferative neoplasms (MPN) with or without ruxolitinib therapy and 12 healthy donors were analyzed for NK cell frequency, NK receptor expression and function. Phenotypic and functional NK cell markers (e.g. CD11b, CD27, KIR, NKG2A, NKG2D, NKp46, CD16, granzyme B, and perforin) were analyzed by FACS. NK cell function was evaluated by classical killing assays upon stimulation with MHC class I-deficient target cells K562. Finally, a set of additional in vitro experiments (e.g. analysis of lytic synapse formation by FACS and confocal microscopy) were performed to define in more detail the characteristics and potential mechanisms of ruxolitinib-induced NK cell dysfunction. Results: In addition to our recent finding that ruxolitinib induces NK cell dysfunction in vitro (e.g. reduced killing, degranulation and IFN-γ production), we here demonstrate that NK cell proliferation and cytokine-induced receptor expression as well as cytokine signalling are drastically impaired by ruxolitinib. Interestingly, reduced killing is at least in part due to a reduced capacity to form a mature lytic synapse with target cells. The significance of the in vitrofindings is underscored by a dramatically reduced proportion and absolute number of NK cells in ruxolitinib-treated MPN patients when compared to treatment-naïve patients or to healthy controls (mean percentage of NK cell frequency: ruxolitinib-naïve MPN patients 12.63% ±1.81; healthy donors 13.51% ±1.44; ruxolitinib-treated patients 5.47% ±1.27). A systematic analysis of NK cell receptor expression revealed that the reduction of NK cells in ruxolitinib-exposed individuals is most likely due to an impaired NK cell differentiation and maturation process, as reflected by a significantly increased ratio of immature to mature NK cells. Finally, the endogenous functional NK cell defect in MPN is further aggravated by intake of the JAK inhibitor ruxolitinib. Conclusion: We here provide compelling in vitro and in vivo evidence that inhibition of the JAK/STAT-pathway by ruxolitinib exerts substantial effects on the NK cell compartment in MPN patients due to the inhibition of NK cell differentiation and NK cell key functions. Our data may help to better understand the increased rate of severe infections and complement recent reports on ruxolitinib-induced immune dysfunction. Disclosures Koschmieder: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Travel, Accomodation, Expenses Other. Brümmendorf:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Wolf:Novartis: Consultancy, Honoraria, Research Funding, Travel and Accommodation Other.

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127 Preclinical evaluation of NKX019, a CD19-targeting CAR NK Cell

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2020-sitc2020.0127 ◽

2020 ◽

Vol 8 (Suppl 3) ◽

pp. A140-A140

Author(s):

Nadege Morisot ◽

Sarah Wadsworth ◽

Tina Davis ◽

Nicole Dailey ◽

Kyle Hansen ◽

...

Keyword(s):

T Cells ◽

B Cell ◽

Nk Cells ◽

Half Life ◽

Nk Cell ◽

Cytolytic Activity ◽

Nsg Mice ◽

Animal Care

BackgroundNatural killer (NK) cells are highly effective and fast-acting cytolytic cells capable of eradicating target cells with limited adverse effects such as cytokine release syndrome (CRS) or graft-versus-host disease. Chimeric antigen receptors (CARs)-engineered NK cells have been recently used against leukemia with encouraging clinical outcomes.1 The surface antigen CD19, expressed by B-lymphoblasts, represents an ideal CAR target against B cell acute lymphoblastic leukemia (B-ALL). We developed a highly potent CD19 -directed CAR NK cell therapy, NKX019, with an extended in vivo half-life aimed at killing CD19-expressing target.MethodsNK cells isolated from healthy PBMCs were expanded in the presence of NKSTIM cells, IL-2, IL-12, IL-18 and transduced with both a CD19-targeted CAR construct and a membrane-bound form of IL-15 (mbIL-15). Control (non-engineered) NK cells were produced in parallel. Cytotoxic activity of NKX019 against CD19+ B-ALL cell line (REH), pre-B ALL cell line (Nalm-6), allogeneic PBMCs was assessed using Incucyte® or flow cytometry. NSG mice bearing either Nalm-6.fluc (Nalm6) or REH.fluc (REH) tumor received different concentrations of NKX019 or control NK cells. In-life analysis of tumor-bearing and naïve NSG mice include: 1) bioluminescence imaging, 2) clinical observations, 3) serum cytokines and 4) CAR+ NK cell persistency.ResultsNKX019 showed enhanced cytolytic activity against REH and Nalm-6 tumor cells compared to control NK cells and CAR19+ T cells. The superiority of NKX019 over CAR19+ T cells was more pronounced at the earlier time point (24 hours) with near identical calculated EC50 observed at 72 hours for both cell types. Increased cytolytic activity of NKX019 was limited to CD19+ cells in bulk PBMCs. Consistent with our in vitro observations, NKX019 controlled Nalm-6 and REH tumor growth in doses as low as 2 × 106 cells/kg for up to 30 days with no apparent increase in cytokines commonly associated with CRS. Increased Nalm-6 tumor growth coincided with an apparent decrease in measurable NKX019 in the periphery. In tumor-naïve NSG mice, NKX019 was detectable in the blood for up to 9 weeks post-infusion consistent with its extended half-life.ConclusionsNKX019 expresses mbIL-15 and is produced in the presence of IL-12 and IL-18, resulting in enhanced in vitro expansion and longer in vivo half-life than non-engineered NK cells. NKX019 also exhibited advantages compared to CAR19+ T cells including faster cytotoxic kinetics and limited production of cytokines associated with CRS. A first-in-human trial of NKX019 in B cell malignancies is planned for 2021.Ethics ApprovalThe animal procedures described in this abstract were conducted in accordance with Explora BioLabs Animal Care and Use Protocol approved by Explora BioLabs Institutional Animal Care and Use Committee.ReferenceLiu, et al. 2020 NEJM

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Enhanced In Vivo Persistence and Proliferation of NK Cells Expanded in Culture with the Small Molecule Nicotinamide: Development of a Clinical-Applicable Method for NK Expansion

Blood ◽

10.1182/blood.v130.suppl_1.657.657 ◽

2017 ◽

Vol 130 (Suppl_1) ◽

pp. 657-657 ◽

Cited By ~ 1

Author(s):

Tony Peled ◽

Guy Brachya ◽

Nurit Persi ◽

Chana Lador ◽

Esti Olesinski ◽

...

Keyword(s):

Nk Cells ◽

Board Of Directors ◽

Research Funding ◽

Nk Cell ◽

Culture Method ◽

Employment Equity ◽

Advisory Committees ◽

Nsg Mice ◽

Equity Ownership

Abstract Adoptive transfer of cytolitic Natural Killer (NK) cells is a promising immunotherapeutic modality for hematologic and other malignancies. However, limited NK cell in vivo persistence and proliferation have been challenging clinical success of this therapeutic modality. Here we present a reliable, scalable and GMP-compliant culture method for the expansion of highly functional donor NK cells for clinical use. Nicotinamide (NAM), a form of vitamin B-3, serves as a precursor of nicotinamide adenine dinucleotide (NAD) and is a potent inhibitor of enzymes that require NAD including ADP ribosyltransferases and cyclic ADP ribose/NADase. As such, NAM is implicated in the regulation of cell adhesion, polarity, migration, proliferation, and differentiation. We have previously reported that NAM augments tumor cytotoxicity and cytokine (TNFα and IFN-γ) secretion of NK cells expanded in feeder-free culture conditions stimulated with IL-2 or IL-15. Immunophenotype studies demonstrated NK cells expanded with NAM underwent typical changes observed with cytokine only-induced NK cell activation with no significant differences in the expression of activating and inhibitory receptors. CD200R and PD-1 receptors were expressed at low levels in resting NK cells, but their expression was up-regulated following activation in typical cytokine expansion cultures. Interestingly, the increase in CD200R and PD-1 was reduced by NAM, suggesting these NK cells to be less susceptible to cancer immunoevasion mechanisms (Fig 1). In vivo retention and proliferation is a pre-requisite for the success of NK therapy. We have reported that NK expanded with NAM displayed substantially better retention in the bone marrow, spleen and peripheral blood of irradiated NSG mice. Using a carboxyfluorescein succinimidyl ester (CFSE) dilution assay, we demonstrated increased in vivo proliferation of NAM-cultured NK cells compared with cells cultured without NAM. These results were recently confirmed using a BrdU incorporation assay in irradiated NSG mice (Fig.2). These findings were mechanistically supported by a substantial increase in CD62L (L-selectin) expression in cultures treated with NAM. CD62L is pivotal for NK cell trafficking and homeostatic proliferation and its expression is down regulated in IL-2 or IL-15 stimulated cultures (Fig. 3). These data provided the foundation for the development of a feeder cell-free scalable culture method for clinical therapy using apheresis units obtained from healthy volunteers. CD3+ cells were depleted using a CliniMACS T cell depletion set. Following depletion, the CD3- fraction was analyzed for phenotypic markers and cultured in closed-system flasks (G-Rex100 MCS, Wilson Wolf) supplemented with 20ng/ml IL-15 or 50ng/ml IL-2 GMP, 10% human serum, minimum essential medium-α and NAM USP for two weeks. While at seeding, NK cells comprised 5-20% of total culture seeded cells, at harvest, NK cells comprised more than 97% of the culture. Although overall contamination of the NK cultures was low with either IL-15 or IL-2, a lower fraction of CD3+ and CD19+ cells was observed with IL-15 vs IL-2 (0.2±0.1% vs. 0.4±0.2% and 1.3±0.4% vs. 2.4±0.6%, respectively). Consequently, we decided to use IL-15 for clinical manufacturing. Optimization of NAM concentration studies showed similar expansion with 2.5 and 5 mM and a decrease in expansion with 7.5 mM NAM. Since NAM at 5 mM had a stronger impact on CD62L expression and on the release of IFNγ and TNFα than NAM at 2.5 mM, we selected 5mM NAM for clinical manufacturing. Overall median NK expansion after two weeks in closed G-Rex flasks supplemented with IL-15 and 5mM NAM was 50-fold (range 37-87). An additional and significant increase in expansion was obtained after doubling the culture medium one week post seeding. While there was a marked advantage for single culture feeding, more feedings had less impact on NK expansion and had a negative effect on the in vivo retention potential. Our optimized expansion protocol therefore involved one feeding during the two weeks expansion duration resulting in 162±30.7-fold expansion of NK cells relative to their input number in culture. Based on these data, we have initiated a clinical trial at University of Minnesota, to test the safety and efficacy of escalating doses (2 x 107/kg - 2 x 108/kg) of our novel NAM NK cell product in patients with refractory non-Hodgkins lymphoma and multiple myeloma (NCT03019666). Disclosures Peled: Gamida Cell: Employment, Equity Ownership. Brachya: Gamida Cell: Employment. Persi: Gamida Cell: Employment. Lador: gamida Cell: Employment, Equity Ownership. Olesinski: gamida cell: Employment. Landau: gamida cell: Employment, Equity Ownership. Galamidi: gamida cell: Employment. Peled: Biokine: Consultancy; Biosight: Consultancy. Miller: Celegene: Consultancy; Oxis Biotech: Consultancy; Fate Therapeutics: Consultancy, Research Funding. Bachanova: Oxis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Zymogen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle-Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno: Membership on an entity's Board of Directors or advisory committees.

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Preclinical Evidence for the Efficacy of CD79b Immunotherapy in B Cell Precursor Acute Lymphoblastic Leukemia

Blood ◽

10.1182/blood-2021-148429 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2388-2388

Author(s):

Lennart Lenk ◽

Dorothee Winterberg ◽

Fotini Vogiatzi ◽

Anna Laqua ◽

Lea Spory ◽

...

Keyword(s):

B Cell ◽

Therapeutic Target ◽

Research Funding ◽

Lymphoblastic Leukemia ◽

Advisory Board ◽

Research Support ◽

Nsg Mice ◽

Significant Survival ◽

Survival Prolongation

Abstract Patients with B cell precursor acute lymphoblastic leukemia (BCP-ALL) have a favorable prognosis, yet current treatment protocols are based on intensive cytotoxic chemotherapy and therapy options are limited when patients relapse. Novel immunotherapy approaches are therefore needed. We recently reported that the preB cell receptor signaling unit CD79a (known as Igα) is crucial for BCP-ALL engraftment in vivo, particularly in the central nervous system (CNS) employing BCR-ABL + and E2A-PBX1 + patient derived xenograft (PDX) models (Lenk et al., Communications Biology, 2021). CD79a forms a heterodimer with CD79b (known as Igß), which is also expressed on the surface of mature B cells as part of the B cell antigen receptor. Accordingly, the CD79b antibody drug conjugate (ADC) Polatuzumab Vedotin (PolVed) has shown therapeutic efficacy in the treatment of refractory/relapsed (r/r) diffuse large B cell lymphoma. Moreover, CD79a/CD79b may also be present on the cell surface at the pro/pre B cell stage. We therefore hypothesize that CD79b can serve as a therapeutic target in BCP-ALL. First, to substantiate that CD79b is important for BCP-ALL engraftment in vivo, a murine/murine transplantation model was applied. B cell precursors were isolated from mice harboring CD79b with a non-functional signaling domain (CD79b-ITAM-KO) or wildtype mice, malignantly transformed with a BCR-ABL fusion construct and transplanted into NSG-mice. Whereas control cells caused overt leukemia in all animals within 25 days, no animal injected with CD79b-ITAM-KO cells had developed leukemia by the time of sacrifice at 162 days (P<0.001). To investigate the frequency of surface (s)CD79b expression in BCP-ALL patients, we measured sCD79b levels via flow cytometry in diagnostic samples of pediatric BCP-ALL patients with different cytogenetic backgrounds. We detected sCD79b-positivity (defined as ≥10% sCD79b + BCP-ALL cells) in 23/94 patients including BCR-ABL +, E2A-PBX1 +, MLL-rearranged (MLLr), TEL-AML1 + and B-other BCP-ALL patients indicating a population of sCD79b + patients within different cytogenetic BCP-ALL subgroups (Figure 1a). To validate CD79b as a therapeutic target, we applied an unconjugated monoclonal CD79b antibody (CD79b-mAB) to PDX mice bearing either pediatric BCR-ABL + or E2A-PBX1 + PDX samples with high sCD79b expression (49.6% sCD79b + cells and 37.7% sCD79b + cells, respectively). Treatment was initiated one day after BCP-ALL injection, modelling a minimal residual disease (MRD) situation. Therapy with CD79b-mAB (1mg/kg) resulted in a mild reduction of leukemia burden in the spleen (SP) and bone marrow (BM) of PDX mice and a significant reduction of CNS-involvement in both PDX-models as compared to control treated mice (P<0.05 and P<0.01, respectively). To test the hypothesis that treatment of BCP-ALL with a CD79b-ADC outperforms CD79b-mAB, we applied PolVed (1mg/kg) in NSG mice bearing the same E2A-PBX1 + and BCR-ABL + PDX cells. PolVed therapy resulted in a significant reduction of BCP-ALL engraftment in SP, BM and CNS (P<0.01, respectively) and a significant survival prolongation compared to control treated mice in both models (P<0.01, respectively). Of note, 4/5 PolVed-treated E2A-PBX1-PDX animals were free of leukemia by the time of sacrifice (236 days) (Figure 1B). To test the efficacy of PolVed on different BCP-ALL subgroups, we conducted a preclinical phase II-like PDX study, using sCD79b high and sCD79b low PDX samples (defined by sCD79b-expression above or below the median) (5E2A-PBX1 +, 3 BCR-ABL +, 2 MLLr, 1 E2A-HLF + and 1 ETV6-NTRK3 +). Two NSG mice per patient were injected with PDX cells, randomly assigned into treatment groups and PolVed therapy was initiated when 1% PDX-cells were detected in the peripheral blood, modelling an overt leukemia situation. sCD79b low PDX mice did not respond to PolVed treatment (Figure 1c), but we detected a response to therapy and a significant survival prolongation in 5/6 sCD79b high PDX samples irrespective of the cytogenetic background (P<0.05) (Figure 1d). Taken together, our data indicate that a subgroup of BCP-ALL patients is sCD79 + positive and may respond to PolVed treatment. Therefore, we suggest CD79b as a novel therapeutic target in BCP-ALL and propose PolVed as a potential therapeutic agent in r/r disease. *LL and DW contributed equally to this work Figure 1 Figure 1. Disclosures Lenk: OSE Immunotherapeutics: Research Funding. Richter: HTG Molecular Diagnostics, Inc.: Current Employment, Research Funding. Schrappe: SHIRE: Other: research support; JazzPharma: Honoraria, Other: research support; Servier: Honoraria, Other: research support; SigmaTau: Other: research support; Novartis: Honoraria; JazzPharma: Honoraria; Novartis: Honoraria, Other: research support; Servier: Honoraria; Amgen: Other: research support. Cario: Novartis: Other: Lecture Fee. Brüggemann: Incyte: Other: Advisory Board; Amgen: Other: Advisory Board, Travel support, Research Funding, Speakers Bureau; Janssen: Speakers Bureau. Schewe: Jazz Pharmaceuticals: Other: Advisory Board; SOBI: Other: Advisory Board; Bayer: Other: Advisory Board; OSE Immunotherapeutics: Research Funding.

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Off-the-Shelf Natural Killer Cells with Multi-Functional Engineering Using a Novel Anti-CD19 Chimeric Antigen Receptor Combined with Stabilized CD16 and IL15 Expression to Enhance Directed Anti-Tumor Activity

Blood ◽

10.1182/blood-2018-99-113701 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 4541-4541

Author(s):

Dan S Kaufman ◽

Ryan Bjordahl ◽

Huang Zhu ◽

Robert Blum ◽

Andres Bahena ◽

...

Keyword(s):

B Cell ◽

Nk Cells ◽

Natural Killer ◽

Chimeric Antigen Receptor ◽

Research Funding ◽

Nk Cell ◽

B Cell Malignancies ◽

Renewable Source ◽

Cell Immunotherapy ◽

Anti Tumor Activity

Abstract T lymphocytes that express an anti-CD19 chimeric antigen receptor (CAR) to redirect target specificity exhibit remarkable remissions in B cell malignancies. However, these cells are typically produced in a patient-specific manner that is relatively inefficient and expensive. Additionally, CAR-T cell treatment can lead to severe adverse events (SAEs) such as cytokine release syndrome (CRS) and neurotoxicity, as well as graft versus host disease (GvHD) when given in allogeneic setting. To circumvent these safety issues while maintaining multi-faceted anti-tumor activity, we developed an off-the-shelf natural killer (NK) cell consisting of a novel CAR combined with other effector mechanisms to enhance targeted cytotoxicity. NK cells are potent anti-tumor effector cells that play an important role in innate and adaptive immunity. Multiple clinical studies have demonstrated that adoptive transfer of allogeneic NK cells can induce durable remissions in patients with cancers that have relapsed or are refractory to standard therapies without detection of SAEs such as CRS. However, NK cells are challenging to genetically engineer, and are dependent on cytokine support for persistence and exhibit donor-to-donor variability factors that make it difficult to create a consistent clinical product from NK cells. Here we report the use of human induced pluripotent stem cells (iPSCs) to produce a renewable source of precisely engineered NK cells. This iPSC platform was utilized to evaluate a combination of CARs comprised of distinct NK-cell specific signaling and transmembrane domains with an autonomous protein to create a persistent and targeted NK cell immunotherapy. The selected NK cell optimized CAR (NK-CAR) backbone contains an NKG2D transmembrane domain, a 2B4 co-stimulatory domain, and a CD3ζ signaling domain to mediate a potent NK cell activating signal. To provide directed anti-tumor activity, anti-CD19 scFv was added to the NK-CAR backbone, engineered at the iPSC stage and subsequently differentiated on-demand to produce a uniform population of CAR-expressing NK cells. In addition, an IL-15RF fusion transgene was introduced to provide self-stimulating signals to support NK cell function and persistence. The IL-15RF construct was created by fusing IL-15Rα to IL-15 at the C-terminus through a flexible linker. As a third modality, a metalloprotease ADAM17-resistant version of the high-affinity CD16a (hnCD16) 158V variant was introduced at the iPSC stage to augment antibody-dependent cellular-cytotoxicity (ADCC) when used in combination with monoclonal antibodies. The selected iPSC clone exhibits stable expression of all three modalities and represents a renewable source of starting material for the reproducible generation of NK cells consisting of NK-CAR, IL-15RF and hnCD16 with product purity that is greater than 95% CD45+CD56+ with a product expansion greater than one million-fold over the course of the manufacturing process. In preclinical studies, these multi-functional engineered NK cells demonstrated enhanced directed cytotoxicity against CD19+ tumor targets when compared to non-engineered NK cells or iPSC-derived NK cells engineered with other CAR constructs. Additionally, the multi-functional engineered iPSC-CAR-NK cells significantly reduced tumor burden in a xenograft model of B acute lymphoblastic leukemia (p<0.05 at day 28). NK cells with IL-15RF inclusion demonstrated improved proliferation in the absence of cytokine support, as well as improved potency when immediately thawed and tested for efficacy. NK-CAR + IL-15RF eliminated 94% and 86% of target cells in the presence and absence of IL-2, respectively, while NK-CAR efficacy was reduced from 98% target elimination in the presence of IL-2 to 56% in the absence of IL-2. In conclusion, these studies demonstrate iPSCs serve as an optimal platform to provide a renewable multi-engineered NK cell product suitable for an "off-the-shelf" approach and serve as preclinical proof of concept for program FT519, a standardized CAR-targeted NK cell immunotherapy against B cell malignancies. Disclosures Kaufman: Fate Therapeutics: Consultancy, Research Funding. Bjordahl:Fate Therapeutics Inc.: Employment. Mahmood:Fate Therapeutics Inc.: Employment. Bonello:Fate Therapeutics Inc.: Employment. Lee:Fate Therapeutics Inc.: Employment. Cichocki:Fate Therapeutics Inc.: Consultancy, Research Funding. Valamehr:Fate Therapeutics Inc.: Employment.

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Eomes and T-Bet Expression Are Required By Mature Primary Human NK Cells for Anti-Leukemia Responses In Vivo

Blood ◽

10.1182/blood-2021-149693 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 194-194

Author(s):

Pamela Wong ◽

Carly C. Neal ◽

Lily Chang ◽

Julia A Wagner ◽

Melissa M. Berrien-Elliott ◽

...

Keyword(s):

Nk Cells ◽

Research Funding ◽

Nk Cell ◽

Ex Vivo ◽

T Box ◽

Nsg Mice ◽

Healthy Donors ◽

And Function

Abstract Natural Killer (NK) cells are innate lymphoid cells that respond to hematologic cancers via cytotoxicity (perforin/granzyme and death receptors) and cytokine/chemokine production, yet the molecular determinants underlying their proliferation, function, and persistence are poorly understood. There are promising reports of pre-clinical and clinical NK cell responses to leukemia and lymphoma, which represent a nascent cellular therapy for these blood cancers. The T-box transcription factors (TFs) Eomes and T-bet are expressed by NK cells throughout their lifespan, and are required for development as evidenced by NK cell loss in Eomes and T-bet deficient mice. However, the roles of these TFs in mature human NK cell molecular programs and functions remain unclear. We hypothesized Eomes and T-bet, which are the only T-box TFs expressed in NK cells, are critical regulators of NK cell homeostasis and functionality, and are necessary for proper mature NK cell responses. To address this, we utilized the CRISPR-Cas9 system to genetically delete both Eomes and T-bet in primary human NK cells isolated from healthy donors, and investigated their role beyond guiding NK cell development, specifically in the anti-leukemia response. Gene-editing of primary human NK cells has been technically challenging, thus most reports that modified NK cells were performed with cell lines, in vitro-differentiated, or highly expanded NK cells that likely do not reflect primary human NK cell biology. Here, we introduced Cas9 mRNA and sgRNA targeting T-bet and Eomes by electroporation into unexpanded primary human NK cells isolated from healthy donors using the MaxCyte GT system. We observed highly efficient reductions of Eomes and T-bet protein expression, quantified by flow cytometry (p < 0.0001, Fig A-B) without viability differences between control (sgRNA targeting TRAC, an unexpressed locus in NK cells), and Eomes/T-bet double CRISPR-edited (DKO) cells after one week in vitro. To study Eomes and T-bet in NK cell anti-leukemia response, control or DKO primary human NK cells were engrafted into NSG mice, supported with human IL-15, and challenged with K562 leukemia cells. Utilizing bioluminescent imaging to visualize leukemia burden, we observed that NK cells lacking both TFs were unable to suppress leukemia growth in vivo. To understand the mechanism responsible for impaired leukemia control, we investigated in vivo persistence and proliferation, cytotoxic effector molecule expression, as well as ex vivo degranulation and cytokine production of DKO NK cells compared to control NK cells. DKO or control human NK cells were transferred into NSG mice and supported with human IL-15. After 2-3 weeks, significantly fewer (<30%) DKO NK cells persisted compared to control NK cells: spleen (5-fold decrease, control 240e3±65e3 vs DKO 47e3±15e3 NK cells, p<0.01, Figure C), blood (6-fold decrease, p<0.01), and liver (4-fold decrease, p<0.05). Using intracellular flow cytometry, double T-bet/Eomes CRISPR-edited NK cells that lacked both Eomes and T-bet protein after in vivo transfer were identified. A proliferative defect was evident in flow-gated DKO (62±6% undivided), compared to unedited (WT) NK cells (4±2% undivided) assessed by CellTrace Violet dilution (Figure D). In addition, there were marked reductions in granzyme B and perforin protein (p<0.001) in flow-gated DKO NK cells compared to controls. To assess DKO NK cell functional capacity, we performed an ex vivo functional assay on NK cells from spleens of the NSG mice as effectors, and K562 targets or IL-12/15/18 stimulation for 6 hours. Degranulation to K562 targets was impaired (p<0.05), and IFN-γ production was reduced (p<0.0001) after cytokine stimulation in flow-gated DKO NK cells (Figure E). Thus, CRISPR-editing of unexpanded, primary human NK cells revealed that Eomes and T-bet are required by mature human NK cells for their function and homeostasis, distinct from their role in development. This is translationally relevant, as defects in proliferation and function of human DKO NK cells manifested markedly reduced response against human leukemia cells in vivo in xenografts. These findings expand our understanding of key molecular regulators of mature NK cell homeostasis and function, with the potential to provide new avenues to enhance NK cell therapy. Figure 1 Figure 1. Disclosures Berrien-Elliott: Wugen: Consultancy, Patents & Royalties: 017001-PRO1, Research Funding. Foltz-Stringfellow: Kiadis: Patents & Royalties: TGFbeta expanded NK cells; EMD Millipore: Other: canine antibody licensing fees. Fehniger: HCW Biologics: Research Funding; Compass Therapeutics: Research Funding; Affimed: Research Funding; ImmunityBio: Research Funding; Wugen: Consultancy, Current equity holder in publicly-traded company, Patents & Royalties: related to memory like NK cells, Research Funding; Kiadis: Other; OrcaBio: Other; Indapta: Other.

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CD16-IL15-CD33 Trispecific Killer Engager (TriKE) Overcomes Cancer-Induced Immune Suppression and Induces Natural Killer Cell-Mediated Control of MDS and AML Via Enhanced Killing Kinetics

Blood ◽

10.1182/blood.v128.22.4291.4291 ◽

2016 ◽

Vol 128 (22) ◽

pp. 4291-4291 ◽

Cited By ~ 4

Author(s):

Martin Felices ◽

Dhifaf Sarhan ◽

Ludwig Brandt ◽

Karolin Guldevall ◽

Ron McElmurry ◽

...

Keyword(s):

Nk Cells ◽

Immune Suppression ◽

Research Funding ◽

Nk Cell ◽

Tumor Control ◽

Target Cells ◽

Antigen Specificity ◽

Cell Counts ◽

Tumor Killing

Abstract Although adoptive transfer of NK cells with IL-2 can induce complete remissions in 30-50% of patients with refractory AML, efficacy is limited by IL-2 mediated induction of Tregs and by lack of antigen specificity. Thus we generated a 161533 trispecific killer engager (TriKE) molecule containing an anti-CD16 scFv to engage NK cells, an anti-CD33 scFv to engage myeloid targets (including myelodysplastic syndrome [MDS]), and a modified IL-15 linker. We have previously shown that this molecule is superior to a 1633 bispecific killer engager (BiKE) in killing of AML targets and that it promotes enhanced survival and in vivo expansion of NK cells. We questioned the mechanism for the increased potency of the 161533 TriKE and if the TriKE could activate the dysfunctional and suppressed NK cells found in patients with MDS. Cryopreserved mononuclear cells (obtained from the NMDP Sample Repository) collected from 8 patients with advanced MDS were tested to investigate how the TriKE might enhance functionality in this setting. Previously we reported that MDS patients have significantly decreased frequencies of NK cells due to increased CD33+ myeloid derived suppressor cells. Our 161533 TriKE enhanced the function of NK cells derived from MDS patients against acute promyelocytic CD33+ leukemia HL-60 tumor targets (Figure 1A), when compared to 1633 BiKE, in a flow cytometry assay measuring NK cell degranulation (% CD107a: 41.8±3.8 vs. 30.3±3.2, p=0.004), and inflammatory cytokine production (% IFNg: 40.7±5.0 vs. 30.0±4.9, p=0.009; % TNFa: 36.9±5.5 vs. 28.4±4.8, p=0.009). State of the art microchip-based live cell imaging was then employed to evaluate NK cell function and contact-to-target dynamics (Figure 1B). Briefly, resting NK cells and HL-60 target cells were stained with distinct dyes and then co-incubated in the presence of BiKE or TriKE in microwells at 37°C and 5% CO2. Cells were then imaged for 12 hours using a Zeiss 880 microscope and analyzed by Matlab. In contrast to those incubated with BiKE, NK cells cultured in the presence of TriKE had augmented cytotoxicity (37%±6% vs. 59%±6%, p=0.02) and killed their targets remarkably faster (time to first target kill = 148±30 min vs. 75±26 min, p< 0.0001). In addition, NK cell serial killers were more common in the presence of TriKE compared to BiKE (number of killed targets ≥3: 18%±7% vs. 9%±1%, p=0.04). Having shown the robust killing dynamics of TriKE primed NK cells, we next designed an in vivo dose escalation study to evaluate HL-60 tumor control in our xenogeneic mouse model. NSG (NOD scid gamma) mice were conditioned with a sub-lethal dose of radiation (275 cGy) and engrafted with 750,000 HL-60luc cells, which allow for tracking of tumor growth using bioluminescent imaging (BLI). Mice were infused with 1 million fresh healthy donor human NK cells and treated daily with recombinant IL-15 (5 ug/injection), 20-200 ug of 161533 TriKE, or left untreated. Higher doses of TriKE provided better tumor control (6.3x109±2.9x109 [200 ug 1615133] vs. 1.6 x1010±2.7x109 [20 ug 161533] p/sec/cm2/sr) demonstrating dose responsiveness at days 14 and 21 This was not due to increased proliferation of effectors (NK cell numbers) induced by the IL-15 segment of the TriKE as the absolute PBNK cell counts in mice were not different across the TriKE concentrations. However, the day 14 and 21 absolute PBNK counts were higher in all of the TriKE groups when compared to the IL-15 treated mice, including in the 20 ug 161533 TriKE group which best matched the 5 ug IL-15 dose. These data indicated that the TriKE molecule mediates superior NK cell expansion or maintenance in vivo. Taken together the in vivo data suggests that 161533 TriKE not only mediates tumor control by inducing NK cell proliferation and survival in a methodology that exceeds signals provided by IL-15 alone, but also increases tumor killing through enhanced killing kinetics. In summary, we have shown that the 161533 TriKE can rescue dysfunctional NK cells suppressed in patients with MDS and can mediate potent in vivo tumor killing presumably through better NK cell maintenance and enhanced killing kinetics This is of translational importance and demonstrates that the cancer induced immune suppression is reversible by the activating signals induced by the TriKE molecule. The 161533 TriKE represents a promising modality to maximizing NK cell based immunotherapies against MDS and AML and will be in phase I clinical testing the first half of 2017. Disclosures Cooley: Fate Therapeutics: Research Funding. Vallera:Oxis Biotech: Consultancy, Membership on an entity's Board of Directors or advisory committees. Miller:Fate Therapeutics: Consultancy, Research Funding; Oxis Biotech: Consultancy, Other: SAB.

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Therapy of B-Cell Malignancies by Anti-HLA-DR Humanized Monoclonal Antibody, IMMU-114, Is Mediated through Hyperactivation of ERK and JNK MAP Kinase Signaling Pathways.

Blood ◽

10.1182/blood.v114.22.3738.3738 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3738-3738

Author(s):

Pankaj Gupta ◽

Rhona Stein ◽

Thomas M Cardillo ◽

Richard R Furman ◽

Susan Chen ◽

...

Keyword(s):

B Cell ◽

Signaling Pathways ◽

Cell Lines ◽

Target Cells ◽

B Cell Malignancies ◽

Term Survival ◽

Hla Dr ◽

Induction Of Apoptosis

Abstract Abstract 3738 Poster Board III-674 Introduction HLA-DR is currently under investigation as a target for antibody (mAb) therapy of B-cell malignancies. IMMU-114, a humanized IgG4 form of the murine anti-HLA-DR mAb, L243, recognizes a conformational epitope in the a-chain of HLA-DR. We have previously reported that IMMU-114 lacks effector-cell functions while displaying potent antitumor activity against B-cell lymphomas in vitro and in vivo. Here, we further investigated the cytotoxic effects of IMMU-114 on leukemia, lymphoma, and multiple myeloma (MM) cell lines, as well as clinical specimens of CLL, and explored the signaling pathways involved. Methods Binding and cytotoxicity of IMMU-114 was examined on a panel of NHL, AML, MCL, ALL, and CLL cell lines. Induction of apoptosis (Annexin V binding), ROS generation (dihydoehidium staining), changes in mitochondrial membrane potential (ψM, TMRE staining) and effects on the ERK1/2 and JNK pathways (immunoblot analyses) were evaluated on selected cell lines. The effects of various inhibitors on IMMU-114-mediated apoptosis also were determined. Studies were performed in tumor-bearing SCID mice. Results High expression of HLA-DR was detected on the cell surface of all MCL, ALL, HC, CLL, and NHL cell lines tested, as well as 2/3 AML and 5/6 MM cell lines. IMMU-114 was cytotoxic to 2/2 MCL, 2/2 CLL, 2/4 ALL, 1/1 HC, 2/2 NHL and 2/2 MM cell lines without any added anti-Fc second crosslinking antibody. IMMU-114 was consistently more cytotoxic than anti-CD20 mAbs on these cell lines, as well as on rituximab-resistant variants of Raji and SU-DHL-4. Despite positive staining, AML cell lines, Kasumi-3 and GDM-1, were not killed by IMMU-114. Four of 6 CLL patient samples expressed HLA-DR at markedly higher levels than CD20, with the remaining 2 showing similar HLA-DR and CD20 expression. Approximately 60% cytotoxicity was obtained after incubation with IMMU-114 in CLL patient cells. Induction of apoptosis as well as changes in ψM and ROS correlated with sensitivity of cell lines to IMMU-114-mediated cytotoxicity. Time-course analyses demonstrated that IMMU-114 induced approximately 46% change of ψM and 24% enhancement of ROS in as little as 30 min in Raji cells. These changes were abrogated in the presence of ROS inhibitor, N-acetyl cysteine. Immunoblot analyses revealed that IMMU-114 induces phosphorylation of ERK and JNK mitogen-activated protein (MAP) kinases in all cells defined as IMMU-114-sensitive by the cytotoxicity assays, but not IMMU-114-resistant cell lines. The p38 pathway was found to be constitutively active in these cell lines. Inhibition of ERK, JNK, or ROS by their respective inhibitors decreased apoptosis, although the inhibition was not complete when any single inhibitor was used. This could be due to activation of multiple pathways, since inhibition of 2 or more pathways by specific inhibitors abolishes the apoptosis induced by IMMU-114. Activation (5-fold increases of phosphorylation) of ERK1/2 and JNK signaling pathways also was observed in CLL patient samples following IMMU-114 incubation. Further studies revealed caspase-independent apoptosis and activation of apoptosis-inducing factor (AIF) mediated by IMMU-114. The therapeutic activity of IMMU-114 was evaluated in vivo in 3 NHL models, WSU-FSCCL, Namalwa, and Raji. IMMU-114 was more effective than anti-B-cell mAbs such as rituximab, in all models. For example, in WSU-FSCCL, IMMU-114 treatment yielded 100% long-term survival. Although rituximab also induced significant responses compared to untreated mice (median survival time of 87.5 vs. 36 days for untreated controls, P<0.0001), no long-term survivors were seen. Conclusion IMMU-114 is cytotoxic to a variety of hematological malignancies, and its potent activity can be related to high antigen expression of target cells and hyperactivation of ERK and JNK pathways upon binding to HLA-DR. Clinical evaluation of IMMU-114 is planned. Disclosures: Gupta: Immunomedics Inc.: Employment. Stein:Garden State Cancer Center: Employment. Cardillo:Immunomedics Inc.: Employment. Chang:Immunomedics Inc.: Employment. Goldenberg:Immunomedics Inc.: Consultancy, Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

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