Cord Blood-derived Natural Killer Research Articles

IMMU-29. B7-H3-TARGETED CAR-T AND CAR-NK CELLS AGAINST HUMAN GLIOBLASTOMA

Abstract Glioblastoma multiforme (GBM) is the most lethal primary brain tumor, necessitating novel therapies. Chimeric antigen receptor (CAR) T-cell therapy has recently shown efficacy against GBM. However, this approach is costly and time-consuming due to its personalized nature. Alternatively, CAR-transduced natural killer (NK) cells offer a potential “off-the-shelf” immunotherapy option, as they do not cause graft-versus-host disease. This study aimed to assess the anti-GBM efficacy of CAR T and NK cells targeting B7-H3, a protein highly expressed in GBM. To achieve this, CAR T cells targeting B7-H3 were developed using known anti-B7-H3 scFv sequences. Additionally, cord blood-derived NK cells were transduced with the B7-H3 CAR. Both types of CAR-modified cells were tested for their anti-GBM activity in vitro. Moreover, their anti-tumor effects were evaluated in an in vivo xenograft model using patient-derived GBM cells. The results demonstrated that both B7-H3 CAR T cells and CAR NK cells exhibited significant cytotoxicity against patient-derived GBM cells in vitro. Furthermore, intracranial injection of these CAR-modified cells into the xenograft model significantly reduced tumor growth. In conclusion, B7-H3 targeted CAR T cells and cord blood-derived CAR NK cells both show potential in eliminating GBM cells, suggesting promising avenues for future GBM treatment strategies.

Feeder cell training shapes the phenotype and function of in vitro expanded natural killer cells.

Natural killer (NK) cells are candidates for adoptive cell therapy, and the protocols for their activation and expansion profoundly influence their function and fate. The complexity of NK cell origin and feeder cell cues impacts the heterogeneity of expanded NK (eNK) cells. To explore this, we compared the phenotype and function of peripheral blood-derived NK (PB-NK) and umbilical cord blood-derived NK (UCB-NK) cells activated by common feeder cell lines, including K562, PLH, and 221.AEH. After first encounter, most PB-NK cells showed degranulation independently of cytokines production. Meanwhile, most UCB-NK cells did both. We observed that each feeder cell line uniquely influenced the activation, expansion, and ultimate fate of PB eNK and UCB eNK cells, determining whether they became cytokine producers or killer cells. In addition, they also affected the functional performance of NK cell subsets after expansion, that is, expanded conventional NK (ecNK) and expanded FcRγ- NK (eg-NK)cells. Hence, the regulation of eNK cell function largely depends on the NK cell source and the chosen expansion system. These results underscore the significance of selecting feeder cells for NK cell expansion from various sources, notably for customized adoptive cell therapies to yield cytokine-producing or cytotoxic eNK cells.

10172-IM-6 DEVELOPMENT OF CAR-NK CELL THERAPY TARGETING B7H3 AGAINST GLIOBLASTOMA

Abstract There is an urgent need to find new treatments for brain tumors with poor prognoses, such as glioblastoma (GBM). Recently, CAR-T cell therapy, which uses genetically engineered T cells to express chimeric antigen receptors (CAR) has been actively investigated. However, although CAR-T cell therapy has shown efficacy in preclinical GBM models, CAR-T cells have a number of limitations. When adapted for clinical use, it may exhibit undesirable side effects such as graft-versus-host disease or cytokine-releasing syndrome. Furthermore, generating an autologous product for each patient needs time and effort and is restrictive for widespread clinical use. In contrast, cord blood-derived natural killer (NK) cells show a robust safety profile in vivo and are an attractive therapeutic option for cancer treatment. In this study, we focused on developing CAR-NK therapy against GBM and used B7H3 which has recently been studied as a tumor antigen. First, we generated CAR-T cells expressing CAR against B7H3 and confirmed their antitumor effect in vitro and in vivo. Next, we generated CAR-NK cells with similar scFV from code blood. We generated eight donors of CAR-transfected NK cells and investigated the gene transfer and cell growth rate. We tested three donors of CAR-transfected NK cells and found that one of them had robust cytolytic activity against GBM cells in vitro. Overall, this study suggests that cord blood-derived CAR-NK cells targeting B7H3 may be a promising therapy for GBM.

IMMU-18. ESTABLISHMENT OF CAR-NK CELL THERAPY TARGETING B7-H3 AGAINST GLIOBLASTOMA

Abstract Glioblastoma (GBM) has a poor prognosis despite intensive treatment by surgery, radiation, and chemotherapy, thus new therapeutic strategies are urgently needed. Recently, CAR (chimeric antigen receptors) -T cell therapy, which uses genetically engineered T cells to express CAR has been extensively investigated. However, although CAR-T cell therapy has shown some efficacies in preclinical GBM models, it exhibited limited efficacy and undesirable side effects such as graft-versus-host disease when adapted for clinical trials. In contrast, cord blood-derived natural killer (NK) cells show a robust safety profile in preclinical models and CAR-NK cell therapy is an attractive therapeutic option for cancer treatment. In this study, we aim to analyze the therapeutic efficacy of CAR-NK therapy against GBM. We used B7-H3 as a target antigen for CAR-NK cell therapy because B7-H3 has recently been reported to be a tumor specific antigen for GBM. First, we generated CAR-T cells expressing CAR targeting B7-H3. We found that CAR-T cells targeting B7-H3 produced IL-2 and IFNɤ and exerted cytotoxicity to GBM cells by chromium 51 release assay. In addition, in an orthotopic mouse model, CAR-T cells targeting B7-H3 showed survival benefits compared with control CAR-T cells. Next, we generated CAR-NK cells targeting B7-H3 from cord blood-derived NK cells and found robust cytolytic activity against GBM cells in vitro. These results suggest that cord blood-derived CAR-NK cells targeting B7-H3 may be a promising therapy for GBM and further studies are necessary to examine whether cord blood-derived CAR-NK cells targeting B7-H3 could be a therapeutic strategy against GBM.

A pilot study of cord blood-derived natural killer cells as maintenance therapy after autologous hematopoietic stem cell transplantation.

Natural killer (NK) cell based immunotherapy is an emerging strategy in hematologic malignancies because allogeneic NK cells can provide potent antitumor immunity without inducing graft-versus-host disease. Thus, we expanded cord blood-derived NK (CB-NK) cells ex vivo from random (MHC mismatched and KIR mismatched) donors, and investigate the feasibility and efficacy of repeated infusions CB-NK cells as maintenance therapy after autologous hematopoietic stem cell transplantation (ASCT). Thirty-one patients with acute myeloid leukemia and high-risk lymphoma received ASCT and the adoptive CB-NK cell multiple infusions for maintenance therapy. Patients received a median dose of 5.98 × 107/kg (range, 1.87-17.69 × 107/kg) CB-NK cells and 23 patients completed four infusions, 8 patients received three infusions. Only mild infusion reactions occurred in 15.5% of 116 infusions. Compared to a contemporaneous cohort of 90 patients who did not receive NK cell therapy, the adoptive transfer of CB-NK cells as maintenance treatment showed a tendency of difference in decreasing the relapse rate between CB-NK group and control group (9.7% vs 24.4%). The patients who receiving NK cell infusions had a better PFS and OS than controls (4 year PFS, 84.4 ± 8.3% vs 73.5 ± 5.4%; and 4 year OS, 100% vs 78.1 ± 5.4%) . These findings demonstrate safety and validity of maintenance therapy using CB-NK cells multiple infusions after ASCT, and it is worthy of further clinical trial verification.

Lipid nanoparticle-mediated messenger RNA delivery for ex vivo engineering of natural killer cells

Natural killer (NK) cells participate in the immune system by eliminating cancer and virally infected cells through germline-encoded surface receptors. Their independence from prior activation as well as their significantly lower toxicity have placed them in the spotlight as an alternative to T cells for adoptive cell therapy (ACT). Engineering NK cells with mRNA has shown great potential in ACT by enhancing their tumor targeting and cytotoxicity. However, mRNA transfection of NK cells is challenging, as the most common delivery methods, such as electroporation, show limitations. Therefore, an alternative non-viral delivery system that enables high mRNA transfection efficiency with preservation of the cell viability would be beneficial for the development of NK cell therapies. In this study, we investigated both polymeric and lipid nanoparticle (LNP) formulations for eGFP-mRNA delivery to NK cells, based on a dimethylethanolamine and diethylethanolamine polymeric library and on different ionizable lipids, respectively. The mRNA nanoparticles based on cationic polymers showed limited internalization by NK cells and low transfection efficiency. On the other hand, mRNA-LNP formulations were optimized by tailoring the lipid composition and the microfluidic parameters, resulting in a high transfection efficiency (∼100%) and high protein expression in NK cells. In conclusion, compared to polyplexes and electroporation, the optimized LNPs show a greater transfection efficiency and higher overall eGFP expression, when tested in NK (KHYG-1) and T (Jurkat) cell lines, and cord blood-derived NK cells. Thus, LNP-based mRNA delivery represents a promising strategy to further develop novel NK cell therapies.

Abstract 3191: Genetically modified TGF-β dominant negative receptor and IL15 enhance Natural Killer (NK) cell mediated cytolytic activity in glioblastoma

Abstract Introduction: Glioblastoma (GBM) presents with a poor prognosis and dismal survival rates. While cell-based immune therapies have shown success in other malignancies, there is currently little evidence that GBM is as responsive to current approaches. Novel therapies for these patients are therefore urgently needed. The antitumor effect may be limited by GBM’s rapid progression, its extensive intertumoral heterogeneity, and its immune suppressive microenvironment. For cell-based therapies to be effective, they need to be manufactured rapidly or in advance, recognize multiple targets on GBM, and resist immune suppression. We therefore sought to develop “off-the-shelf” cord blood-derived NK cell therapies capable of recognizing multiple stress ligands on tumor cells but are protected from the microenvironment by expression of a dominant negative receptor to TGFβ (abrogating the negative effects of the cytokine) and secretion of IL15 (overcoming negative signals from the microenvironment). We investigate the therapeutic efficacy of NK cells engineered to express IL15-and/or TGFβ-DNR in glioblastoma model in-vitro and in-vivo. Methods: NK cells were isolated from umbilical cord blood by magnetic selection, and subsequently modified to express IL-15, and/or TGFβ-DNR. Engineered NK cells were expanded with feeder cells. Retroviral transduction efficiency was confirmed by flow cytometry. IL15 expression was quantified by ELISA. To determine the cytotoxicity activity of our engineered NK cells against glioblastoma, we measured lysis of the U87MG cell line. To determine in vivo efficacy of our engineered NK cells, we used xenograft NSG mouse models that were orthotopically engrafted with U87MG in the brain. Tumor growth was measured by bioluminescence. Results: CAR-NK cells were successfully transduced (with a transduction efficiency ranging from 66-83% (mean 74.55% + 10.6, n>3) from umbilical cord blood. NK cells engineered to secrete IL15 secreted a mean of 288.3 pg/mL. After exposure to TGFβ in vitro, NK cells transduced with TGFβ-DNR had a increase of killing [mean 58.25 % + 4.51 at 20:1 (E:T) 48.57% + 11.55 without TGFβ, n=3] compared to un-transduced NK cells [mean 11.98 % + 4.51 at 20:1 (E:T) 49.04% + 5.34 without TGFβ, n=3]. Mice injected with IL15 and TGFβ DNR showed better control of tumor (3.99 x 105 + 0.0007 bioluminescence Vs 1.673 x 107 + 0.160 in mice given mock-transduced NK cells and 8.44 x 109 + 28.62 in control mice). Conclusion: Our preliminary results show that cord blood NK cells modified to secrete IL15 and express TGFβ-DNR can recognize and lyse GBM cells in vitro and orthotopically implanted GBM tumors in vivo. Citation Format: Nethaji Muniraj, Kajal Chaudhry, Joshua Luke Terao, Vipin Suri, Luke Barron, Catherine Bollard, Conrad Russell Cruz. Genetically modified TGF-β dominant negative receptor and IL15 enhance Natural Killer (NK) cell mediated cytolytic activity in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3191.

Comparative Study of the Two High-Efficient Strategies for in vitro Generation of Human Umbilical Cord Blood-derived Natural Killer Cells

To explore the similarities and variations of biological phenotype and cytotoxicity of human umbilical cord blood natural killer cells (hUC- NK) after human umbilical cord blood-derived mononuclear cells (hUC-MNC) activated and expanded by two in vitro high-efficient strategies. Umbilical cord blood mononuclear cells (MNC) from healthy donor were enriched by Ficoll-based density gradient centrifugation. Then, the phenotype, subpopulations, cell viability and cytotoxicity of NK cells derived from Miltenyi medium (denoted as M-NK) and X-VIVO 15 (denoted as X-NK) were compared using a "3IL" strategy. After a 14-day's culture, the contents of CD3-CD56+ NK cells were elevated from 4.25%±0.04% (d 0) to 71%±0.18% (M-NK) and 75.2%±1.1% (X-NK) respectively. Compared with X-NK group, the proportion of CD3+CD4+ T cells and CD3+CD56+ NKT cells in M-NK group decreased significantly. The percentages of CD16+, NKG2D+, NKp44+, CD25+ NK cells in X-NK group was higher than those in the M-NK group, while the total number of expanded NK cells in X-NK group was half of that in M-NK group. There were no significant differences between X-NK and M-NK groups in cell proliferation and cell cycle, except for the lower percentage of Annexin V+ apoptotic cells in M-NK group. Compared with X-NK group, the proportion of CD107a+ NK cells in M-NK group were higher under the same effector-target ratio (E∶T) (P<0.05). The two strategies were adequate for high-efficient generation of NK cells with high level of activation in vitro, however, there are differences in biological phenotypes and tumor cytotoxicity.

Pre-Clinical Efficacy of AB-101, an Allogeneic Cord-Blood Derived Natural Killer (NK) Cell Therapeutic Candidate, in Combination with Anti-CD38 Antibodies in Models of Multiple Myeloma

Introduction: AB-101 is a non-engineered, allogeneic, off-the-shelf, cryopreserved cord blood-derived natural killer (NK)-cell therapy in development as a cancer therapeutic. A highly scaled manufacturing process enables production of 1000s of doses of AB-101 from a single donor cord blood unit (CBU). AB-101 is derived from CBUs selected for KIR-B haplotype and natural high-affinity variant of CD16 (158V/V), which are associated with improved anti-tumor activity and ADCC enhancement, resulting in a highly active NK cell product without the requirement for additional engineering. We are developing AB-101 for combination with monoclonal antibodies (mAbs) to enhance antibody dependent cellular cytotoxicity (ADCC) in patients, initially in an ongoing Phase I clinical trial for NHL. To further develop AB-101 as an ADCC enhancer, we assessed anti-tumor activity in combination with CD38 mAb, against multiple myeloma (MM) cell lines. CD38 is a transmembrane glycoprotein that is uniformly and highly upregulated on MM cells. Anti-CD38 mAbs exert anti-tumor activity against MM through ADCC and other mechanisms. NK cells play a key role in ADCC responses through CD16 receptor signaling. However, the majority of NK cells express CD38 and are depleted by therapeutic CD38 mAbs which could limit their therapeutic efficacy. Combining NK cell therapies with anti-CD38 mAbs, thus necessitates CD38 knockout to prevent fratricide. AB-101 has a naturally low percent and intensity of CD38 expression. Here we present data demonstrating that AB-101 are resistant to anti-CD38 mAb-induced fratricide and can elicit significant ADCC against MM cell lines both in vitro and in vivo. Since anti-CD38 mAbs are combined with glucocorticoids in the clinic, we assessed the impact of dexamethasone and methylprednisolone on ADCC by AB-101. Here we report robust ADCC following treatment of AB-101 with glucocorticoids. Methods: AB-101 was screened for CD38 expression and incubated with anti-CD38 mAb - daratumumab or hIgG1 control (300 - 0.41 µg/ml) for 4 hours to assess fratricide. In vitro ADCC assays were performed at various effector to target ratios against control (Daudi and K562) and MM cell lines (NCI-H929, RPMI 8226, MM.1S and MM.1R) using 2 µg/ml of daratumumab or hIgG1. To study the effect of glucocorticoids, AB-101 was cultured in various concentrations of dexamethasone and methylprednisolone for 48 hours in the presence of 50 or 500 IU/ml of IL-2, prior to ADCC assay. In vivo efficacy of AB-101 in combination with daratumumab was assessed in the intraperitoneal (IP) MM.1S-Luc xenograft model in NSG mice (Figure 1A). Daratumumab and AB-101 were administered by IP injection. Tumor burden was assessed by bioluminescent imaging (BLI). Results: AB-101 was over 98% CD56+/CD3- with 87% CD56+/CD16+ population. Only 22% of GMP drug product were CD38+ with low intensity of expression compared to peripheral blood NK cells (~88%). In the presence of daratumumab AB-101 viability was unaltered compared to hIgG1 control demonstrating resistance to fratricide. Daratumumab enhanced ADCC potential of AB-101 against MM cell lines and Daudi in in vitro. ADCC against MM lines and Daudi did not decrease on exposure to glucocorticoids compared to no treatment group. In vivo anti-tumor efficacy, as evidenced by reduction in BLI signal, was observed in the MM.1S model in AB-101 + daratumumab groups compared to daratumumab and AB-101 alone (Figure 1B). AB-101 + daratumumab (1 and 3mpk) led to 98 and 99% tumor growth inhibition (TGI), respectively, relative to no treatment. Daratumumab monotherapy at 1 and 3mpk showed 21% and 87% TGI respectively, and AB-101 showed 16% TGI relative to no treatment. Conclusions: AB-101 has high and consistent expression of CD16 and low CD38 expression and is resistant to daratumumab induced fratricide and hence can be combined with daratumumab without additional engineering such as CD38 knockout. Daratumumab is combined in the clinic with glucocorticoids, immunomodulatory drugs (IMiDs) and proteosome inhibitors (PI). While IMiDs and PIs are reported to enhance NK cell function, glucocorticoids have been shown to diminish NK cell cytotoxicity. Data presented here suggests that ADCC potential of AB-101 is not negatively impacted by glucocorticoids. Taken together, the in vitro and in vivo data supports further clinical development of AB-101 in combination with daratumumab to treat MM patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Trial in Progress: AB-101, an Allogeneic, Non-Engineered, Cord Blood-Derived Natural Killer (NK) Cell Therapy, As Monotherapy or in Combination with Rituximab in Patients with Relapsed or Refractory Non-Hodgkin Lymphoma

Background: Natural Killer (NK) cells are known to eliminate tumors directly or via antibody-dependent cellular cytotoxicity (ADCC) which is dependent on the maturation, activation and FcγRIIIA (CD16) phenotype of NK cells. Many cancer patients have low NK cell number and dysfunctional innate immunity, which has been correlated with outcomes to monoclonal antibody (mAb) therapy. AB-101 is an allogeneic, non-genetically modified cord blood-derived NK cell therapy, developed to potentially enhance patients' innate anti-tumor activity in combination with approved oncology products with known ADCC mechanism of action. AB-101 has been optimized for combination with mAbs through the novel AlloNK™ proprietary large scale manufacturing process utilizing donor cord blood units. The cord blood unit is selected for key attributes, including an immunoglobulin-like receptor B (KIR-B) haplotype and the natural high-affinity variant of CD16 (158V/V polymorphism). The AlloNK™ process results in an activated and mature NK cell product with increased cell surface expression of CD16, NKG2D, NKp30/44/46, and DNAM-1, without any requirement for genetic engineering. Additionally, the process generates sufficient NK cells to treat hundreds to thousands of patients from a single cord blood unit and produces a consistently active NK cell product, with little donor-to-donor variability. The combination of AB-101 and rituximab has demonstrated strong cytotoxic activity in preclinical studies; the combination led to improved survival over rituximab or NK cells alone in xenograft mouse models. As a cryopreserved, "off-the-shelf", and infusion-ready product, AB-101 is being evaluated for the treatment of hematologic malignancies in combination with standard of care antibody therapies. Study Design, Treatment and Methods: AB-101-01 is a first in human, Phase 1/2, multi-center, open-label study to evaluate the safety and anti-tumor activity of AB-101 as monotherapy and in combination with rituximab in patients with relapsed or refractory (R/R) non-Hodgkin lymphoma (NHL) of B-cell origin or CLL. This study has 3 parts: Phase 1, 1b, and 2. Phase 1 will evaluate 2 dose levels as monotherapy or in combination with rituximab using the 3+3 dose escalation method. Phase 1b will enroll up to 45 patients in combination with rituximab to determine the recommended phase 2 dose (RP2D). Phase 2 will enroll an additional 15 patients at the RP2D. AB-101 will be given at 1 or 4 billion cells per dose. All enrolled patients will receive at least 1 treatment cycle of 4 doses of AB-101, administered once weekly. Prior to receiving the first dose of AB-101, patients will receive 3 consecutive days of lymphodepleting chemotherapy consisting of fludarabine (30 mg/m2/day) and cyclophosphamide (250 or 500 mg/m2/day). After each AB-101 infusion, patients will receive interleukin-2 (IL-2) at 1×106 IU/m2/dose or 6×106 IU/dose to potentiate NK cell activation and persistence. If given, 375 mg/m2 of rituximab is dosed on the second day of lymphodepletion and with the second and fourth dose of AB-101. Patients who have a complete or partial response or maintain stable disease with the first cycle of the combination may receive 3 additional cycles such that cycle 2 is given with lymphodepletion and cycles 3 and 4 do not include lymphodepletion. Eligible patients must have a diagnosis of B-cell NHL or CLL and must have received at least 2 prior lines of therapy, including an anti-CD20 antibody therapy. Treatment with prior CD19 CAR T-cell therapy is permitted. Patients must be at least 18 years of age, have ECOG PS of 0 or 1, and have measurable disease per Lugano 2014 at the time of enrollment. The primary objectives of each phase are as follows: in Phase 1, the evaluation of the safety of 1 and 4 billion cells/dose of AB-101 as monotherapy or in combination with rituximab through the incidence of AEs and DLTs; in Phase 1b, determination of the RP2D based on safety and antitumor response to AB-101 with rituximab; and in Phase 2, further characterization of the efficacy profile. The study is currently enrolling at 10 U.S. centers. (ClinicalTrials.gov Identifier: NCT04673617)

Innate Cell Engager AFM13 Combined with Preactivated and Expanded Cord Blood-Derived NK Cells for Patients with Double Refractory CD30+ Lymphoma

Patients with multiple relapsed or refractory (R/R) Hodgkin lymphoma (HL) and other CD30+ lymphoma have few effective therapies available and targeted adoptive natural killer (NK) cell immunotherapy is an active area of investigation. Transfer of non-targeted NK cells has shown limited clinical benefit as target recognition of cancers by NK cells remains a substantial barrier. The innate cell engager (ICE®) construct, AFM13, is a first-in-class CD30/CD16A bispecific antibody construct that induces specific and selective killing of CD30+ tumor cells by engaging and activating NK cells. As a single agent, AFM13 has limited clinical activity against HL, likely due to the reduced effector function of autologous NK cells in these patients, which provides the rationale for the combination of AFM13 with allogeneic NK cells. Our prior preclinical work identified a promising combination of cord blood (CB)-derived NK cells that were first IL-12/IL-15/IL-18-preactivated followed by expansion (P+E) with engineered K562 feeder cells expressing membrane-bound IL-21, 4-1BB ligand and CD48 ex vivo, and subsequently complexed with AFM13 just prior to infusion (Kerbauy et al, Clin Cancer Res 2021; 27:3744-56). These cytokine-induced memory-like CB-derived NK cells precomplexed with AFM13 (AFM13-NK) presented chimeric antigen receptor (CAR)-NK cell-like features and showed an increased in vitro and in vivo antitumor activity compared to either P+E NK or AFM13 alone. Building on this work we wished to clinically study adoptive AFM13-NK cell therapy in pts with R/R CD30+ lymphomas. METHODS: This single-center phase I-II trial (NCT04074746) evaluates the safety and activity of AFM13-NK, followed by AFM13 monotherapy. Patients aged 15-75 years with R/R CD30+ lymphomas refractory to brentuximab vedotin are enrolled. The trial goals are to identify the recommended phase 2 dose (RP2D) of AFM13-NK cells, estimate the overall (ORR) and complete response (CR) rates, event-free (EFS) and overall survival (OS) rates, and studies of NK cell activation and persistence. Each treatment cycle consisted of fludarabine/cyclophosphamide (days −5 to −3), followed by infusion of the AFM13-NK cells, cultured for 14 days as described above (day 0), and three weekly IV infusions of AFM13 (200 mg, days 7, 14 and 21). Two cycles were administered to patients 1-19 and 4 cycles were given starting with patient 20. Response was evaluated on day 28 of each cycle. Patients were enrolled at 3 dose levels: DL1 (106 NK/Kg), DL2 (107NK/Kg) and DL3 (108 NK/Kg). Each patient received the same NK dose in all cycles. RESULTS: As of 7/31/22, 30 pts have been enrolled and treated (Table) at DL1 (N=3), DL2 (N=3) and DL3 (N=24), with 1 (N=1), 2 (N=24), 3 (N=3) or 4 cycles (N=3). All patients had active progressive disease at enrollment and no bridging therapy was given. The cords used for each of the 69 cycles were selected with no consideration for HLA match, which was 0/6 (N=31), 1/6 (N=31), 2/6 (N=5), 3/6 (N=1) and 4/6 (N=1). The product infused consisted of >99% NK cells (expanded >2,700 fold), with only 0.02% T cells. The NK cells were >98% viable and 92% of them were bound to AFM13. The products were infused fresh. There were no infusion-related reactions (IRR) after infusing AFM13-NK and 11 IRR in 182 infusions of AFM13 alone (6%) (1 grade 3, 10 grade 2). We saw no cases of CRS, ICANS or GVHD of any grade. DL3 (108 NK/Kg) was established as the RP2D. The ORR in the entire study is 97% with 63% CRs. All 24 patients treated at the RP2D responded (100% ORR) with 70.8% (17/24) CRs. Five patients had a response consolidated with a SCT. At median follow-up of 8 (range 1-23) months, the EFS and OS rates of all 30 patients are 57% and 83%, respectively. AFM-NK cells were detected in serum from day 1 post infusion and persisted for 3-4 weeks. Donor NK levels followed similar patterns after each cycle, which argues against a sensitization effect in the patient after the first NK infusion. Donor NK cells showed by CyTOF increased binding to AFM13 and expression of activation markers. CONCLUSIONS: This is the first clinical trial to date using an ICE® construct precomplexed with cytokine-induced memory-like CB-NK cells to treat patients with CD30+ R/R HL and NHL. Our preliminary results indicate that this ICE® precomplexed CB-NK cell therapy has an excellent tolerability profile and is highly active in patients with heavily pretreated R/R CD30+ lymphomas and warrants further investigation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Abstract 10 Interim Results of a Phase I Study Investigating a Cord Blood-Derived Natural Killer Cell Therapy for Patients Hospitalized with COVID-19

IntroductionIn the setting of viral infections, including infection with SARS-CoV-2, lymphocyte exhaustion and lymphopenia are common. Patients with COVID-19 who develop lymphopenia, particularly low numbers of circulating natural killer (NK) cells, are at high risk for disease progression. Thus, strategies that overcome profound lymphopenia and restore innate immune function may reduce the severity of COVID-19. One approach is the direct infusion of an exogenous source of healthy, functional NK cells intended to boost the patient’s immune system during the viral infection, enabling elimination of infected cells. “DVX201” is a cord blood-derived allogeneic NK cell therapy that is cryopreserved and intended for “off-the-shelf use” without HLA-matching.ObjectiveThe primary objective of this study is to investigate the safety and to identify the recommended phase II dose and/or the maximum tolerated dose (MTD) of DVX201 in patients hospitalized with COVID-19.MethodsWe are conducting an open-label, nonrandomized phase I safety and dose-finding (modified 3+3) study of DVX201 at three dose levels in patients hospitalized with COVID-19. Adult patients with documented SARS-CoV-2 infection were eligible if they were admitted to the hospital, were receiving ≤6 L supplemental oxygen by low flow delivery, and did not have other evidence of cytokine storm based on levels of serum IL-6, C-reactive protein, and ferritin.ResultsTo date, 9 patients have been enrolled: 3 subjects at each dose level. All dose levels have been well tolerated, with no dose-limiting toxicities, infusion toxicities, or cytokine release syndrome observed. All patients were discharged from the hospital at an average of 5 days post infusion. Blood samples were drawn for correlative studies including persistence of DVX201, pre- and post-infusion immune system characterization, and cytokine panels. Accrual is continuing at the MTD.DiscussionThis trial will serve as the proof of concept for the use of DVX201 as an anti-viral treatment for COVID-19. These results will inform the potential role of DVX201 for treatment of other life-threatening viral infections by harnessing NK cells’ innate function to kill virally infected cells, regardless of the etiology of the infection.

Phase II study of umbilical cord blood–derived natural killer (CB-NK) cells with elotuzumab, lenalidomide, and high-dose melphalan followed by autologous stem cell transplantation (ASCT) for patients with high-risk multiple myeloma (HRMM).

8009 Background: Despite the introduction of several novel agents over the past decade, patients with HRMM continue to have relatively poor outcomes. In a first-in-human study, we previously showed the feasibility of using CB-NK cells up to a dose of 1 x 108 cells/kg in MM patients undergoing high-dose melphalan (200 mg/m2; Mel200) plus lenalidomide and ASCT (NCT01729091). Lenalidomide enhances NK cell function and antibody-mediated cell toxicity against tumor targets. Our preclinical data showed that ex vivo expanded NK cells demonstrated higher elotuzumab-mediated cytotoxicity against myeloma targets than non-expanded cells, and the addition of elotuzumab to lenalidomide augmented the CB-NK cell ADCC against MM1.S myeloma targets. Hence, we aimed from this expansion part of the phase 2 clinical trial to determine the efficacy of CB-NK cells combined with elotuzumab/lenalidomide for HRMM undergoing ASCT. Methods: Patients with HRMM, ages 18-75 years, were eligible. HRMM defined as: disease relapse within 18 months of ASCT; fluorescence in situ hybridization (FISH) showing t(4:14), t(14:16), t(14:20), deletion (del) 17/17p or gain (amp) 1q; del(13) by conventional cytogenetic analysis; high-risk signatures as determined by the GEP-70 or EMC-92 gene expression profiles. With day 0 defined as day of stem cell infusion, treatment consisted of IV elotuzumab 10 mg/kg (days -15 and -8), oral lenalidomide 10 mg (days -8 to -2 prior to ASCT), Mel200 on day -7, and CB-NK cells on day -5. The primary endpoints were best response rate (≥VGPR) and minimal residual disease (MRD) at 3 months after ASCT, as defined per the IMWG criteria. MRD was tested by using 8-color multiparametric flow cytometry validated to a sensitivity level of 0.001% (1 cell in 100,000). Results: Thirty patients, with a median age of 63 (range, 40-72) years, were enrolled between 03/2018 and 01/2021. 97% had R-ISS stages 2/3, 40% had ≥2 high-risk genetic abnormalities, and 23% had del TP53. Most (80%) received induction therapy with bortezomib or carfilzomib + lenalidomide + dexamethasone, 1 patient had prior ASCT, and 4 received &gt;1 prior line of therapy. Before ASCT, 73% had VGPR or better (40% in CR/sCR) and 40% had negative MRD. At 3 months after transplant, 97% achieved ≥VGPR (76%, CR/sCR) and 75% had negative MRD. At median follow-up of 26 (range, 12-44) months, only 4 patients progressed (3 had positive MRD after ASCT). The 2-year PFS and OS rates were 83% and 97%, respectively. No unexpected serious adverse effects attributable to NK cells were noted. Conclusions: CB-derived expanded NK cells plus elotuzumab/lenalidomide combined with Mel200 and ASCT results in excellent and durable hematologic and MRD responses in HRMM patients. Furthermore, PFS and OS rates compare favorably to published outcomes for HRMM patients. Clinical trial information: NCT01729091.

Allogeneic, CD34 +, Umbilical Cordblood-Derived NK Cell Adoptive Immunotherapy for the Treatment of Acute Myeloid Leukemia Patients with Measurable Residual Disease

Although the majority of patients with acute myeloid leukemia (AML) achieve complete remission (CR), most of them relapse due to measurable residual disease (MRD), leading to poorer prognosis. The elimination of MRD before morphological relapse in patients who achieved CR is therefore an important therapeutic strategy to achieve improved long term outcomes in AML.A promising approach is targeting MRD via natural killer (NK) cell adoptive immunotherapy. NK cells can be used without HLA matching (allogeneic), enabling the transfer of high numbers of immune effector cells, which were not exposed to cytotoxic chemotherapy. A phase I dose-escalation trial in ten elderly subjects with AML in morphologic CR after induction chemotherapy showed that a single infusion of an allogeneic NK cell product generated from umbilical cord blood-derived CD34 + cells, following cyclophosphamide/fludarabine (Cy/Flu) pre-conditioning, was safe and well tolerated, with some patients (2 of 4) achieving MRD negativity (Dolstra et al. 2017).Currently, our dose escalation and expansion trial with the “off-the shelf”, cryopreserved, allogeneic NK cell product GTA002 (NCT04632316) is ongoing in adults with AML who are in morphologic CR (including CRi) with MRD and who are not proceeding to allogeneic hematopoietic stem cell transplantation.Two patients have been dosed with a single GTA002 infusion of approximately 5 x 10 8 viable NK cells and completed 6- and 3-month follow-up, respectively. Patient #1 is a 73-year-old male, with AML with recurrent genetic abnormalities (including NPM1mut and FLT3-ITD), who initially received azacitidine and gilteritinib, leading to stable disease. Upon progression, the patient received further treatment with decitabine, followed by 3 cycles of azacitidine/venetoclax (aza/ven), which led to CRi with MRD persistence (confirmed by centralized multiparameter flow cytometry (MFC) on bone marrow (BM)). The patient then received cyclophosphamide (Cy) and fludarabine (Flu) as preconditioning regimen from day -6 to day -3 (Cy: 900 mg/m 2; Flu:15 mg/m 2/day; Flu adjusted for renal impairment), followed by a single intravenous infusion of GTA002 on day 0. The patient experienced a serious adverse event (SAE) on day 5 (grade 3 febrile neutropenia) deemed related to Cy/Flu, which fully resolved on day 16. MRD results by MFC on BM showed that patient #1 converted to MRD negativity (<0.1%) on day 0, which was sustained at 1, 2, 3 and 6 months. Interestingly, NPM1 MRD was detectable by next generation sequencing (MRD-NGS) up to month 1 in peripheral blood (PB), but was cleared by month 2, 3 and 6 in PB (<0.01%VAF). In line with the PB results, NPM1 MRD was detectable in BM at month 1 and was cleared at months 3 and 6.Patient #2 is a 78 year old male with a history of MDS with pancytopenia and IDH2, SRSF2 and PTPN11 mutations that evolved into AML with myelodysplasia-related changes. The patient achieved CR after receiving aza/ven, with MRD positivity after 3 cycles, leading to clinical trial inclusion. He was preconditioned with an adjusted dose of Cy/Flu (Cy 300 and Flu 30 mg/m 2/day from day -5 to day -3), with no SAEs reported. Analysis of BM by MFC showed MRD positivity at screening and on day 0, which turned to MRD negativity at month 1, turning positive again at month 2 and 3. Follow up in PB and BM by MRD-NGS showed that the IDH2 and SRSF2 clones persisted after preconditioning and GTA002 infusion, but the PTPN11 clone became undetectable in PB by Day 0 and in BM by month 2 and month 3.Taken together, these cases describe clearance of MRD by MFC and NGS in AML with a single dose infusion of allogeneic, CD34+ cord blood derived NK cells in one patient and clearance of the PTPN11 mutated clone in another one, reconfirming the excitement to further investigate this treatment strategy for disease control. The delayed clearance of MRD could suggest an ongoing immunotherapeutic effect that will be further investigated. DisclosuresHeuser: Karyopharm: Research Funding; Daichi Sankyo: Honoraria, Research Funding; Bayer AG: Honoraria, Research Funding; BMS/Celgene: Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; BergenBio: Research Funding; Astellas: Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Research Funding; Tolremo: Honoraria; AbbVie: Honoraria; Janssen: Honoraria. Thol: Abbvie: Honoraria; Astellas: Honoraria; Novartis: Honoraria; Jazz: Honoraria; Pfizer: Honoraria; BMS/Celgene: Honoraria, Research Funding. Schwarzer: Bantam Pharmaceutical: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Pinkernell: Medigene AG: Ended employment in the past 24 months; Glycostem Therapeutics: Current Employment. Ganser: Jazz Pharmaceuticals: Honoraria; Novartis: Honoraria; Celgene: Honoraria.

Combining AFM13, a Bispecific CD30/CD16 Antibody, with Cytokine-Activated Blood and Cord Blood-Derived NK Cells Facilitates CAR-like Responses Against CD30+ Malignancies.

Natural killer (NK)-cell recognition and function against NK-resistant cancers remain substantial barriers to the broad application of NK-cell immunotherapy. Potential solutions include bispecific engagers that target NK-cell activity via an NK-activating receptor when simultaneously targeting a tumor-specific antigen, as well as enhancing functionality using IL12/15/18 cytokine pre-activation. We assessed single-cell NK-cell responses stimulated by the tetravalent bispecific antibody AFM13 that binds CD30 on leukemia/lymphoma targets and CD16A on various types of NK cells using mass cytometry and cytotoxicity assays. The combination of AFM13 and IL12/15/18 pre-activation of blood and cord blood-derived NK cells was investigated in vitro and in vivo. We found heterogeneity within AFM13-directed conventional blood NK cell (cNK) responses, as well as consistent AFM13-directed polyfunctional activation of mature NK cells across donors. NK-cell source also impacted the AFM13 response, with cNK cells from healthy donors exhibiting superior responses to those from patients with Hodgkin lymphoma. IL12/15/18-induced memory-like NK cells from peripheral blood exhibited enhanced killing of CD30+ lymphoma targets directed by AFM13, compared with cNK cells. Cord-blood NK cells preactivated with IL12/15/18 and ex vivo expanded with K562-based feeders also exhibited enhanced killing with AFM13 stimulation via upregulation of signaling pathways related to NK-cell effector function. AFM13-NK complex cells exhibited enhanced responses to CD30+ lymphomas in vitro and in vivo. We identify AFM13 as a promising combination with cytokine-activated adult blood or cord-blood NK cells to treat CD30+ hematologic malignancies, warranting clinical trials with these novel combinations.

Designing Magnetically Responsive Biohybrids Composed of Cord Blood-Derived Natural Killer Cells and Iron Oxide Nanoparticles.

We report the generation of magnetically responsive, cord blood-derived natural killer (NK) cells using iron oxide nanoparticles (IONPs). NK cells are a promising immune cell population for cancer cell therapy as they can target and lyse target tumor cells without prior education. However, NK cells cannot home to disease sites based on antigen recognition, instead relying primarily on external stimuli and chemotactic gradients for transport. Hence, we hypothesized that conjugating IONPs onto the surface of NK cells provides an added feature of magnetic homing to the NK cells, improving their therapeutic function. We describe a robust design for conjugating the IONPs onto the surface of NK cells, which maintains their intrinsic phenotype and function. The conferred magnetic-responsiveness is utilized to improve the cytolytic function of the NK cells for target cells in 2D and 3D models. These findings demonstrate the feasibility of improving NK cell homing and therapeutic efficacy with our NK:IONP "biohybrid".

Ontogeny As a Critical Determinant of Natural Killer Cell Potential and Function

Hematopoietic development during mammalian embryogenesis is comprised of a restricted primitive program of primitive erythroid, megakaryocytic, and macrophage lineages, and a definitive program of definitive erythroid, myeloid and lymphoid potential emerging from hematopoietic stem cell (HSC)-independent and dependent processes. Interestingly, progenitors of natural killer (NK) cells, but not B- or T-cells, have been found in the early human yolk sac, suggesting that NK cells may arise from HSC-independent sources.NK cells recognize and kill virally infected cells and tumor cells, making them a highly desirable cell-type for adoptive immunotherapy. To bypass donor-related issues, human pluripotent stem cell (hPSC)-derived NK cells offer the possibility of uniform activity in a renewable “off-the-shelf” cell product. As the differentiation of hPSCs recapitulates early developmental processes, we sought to characterize the developmental origin of hPSC-derived NK cells. Studies in mice indicate that NK cells in the adult are derived from hematopoietic stem cells (HSCs) that commit to a lymphoid differentiation pathway. However, while NK cells, like HSCs, have been found in the fetal liver, the developmental origin of the fetal NK cell lineage remains poorly understood.We have developed a stage-specific hPSC differentiation method that separates WNT-independent (WNTi) hematopoietic progenitors that harbor “primitive” hematopoietic potential from WNT-dependent (WNTd) erythro-myeloid-(T-)lymphoid “definitive” hematopoietic progenitors. Using this system, we find that CD34+ cells from both populations harbor NK cell potential. NK cells from hPSC WNTi progenitors (WNTi-NK cells) mature rapidly, are significantly more granular, and express very high levels of CD16 in comparison to their hPSC WNTd counterparts (WNTd-NK cells) and cord blood-derived NK (cbNK) cells. Further, WNTi CD34+ progenitors always gave rise to a granulocyte population alongside NK cells, suggesting they may be derived from a myeloid progenitor. Both WNTi-NK and WNTd-NK cells robustly respond to tumor targets, antibody-dependent cell-mediated cytotoxicity (ADCC), and PMA/ionomycin stimulation in comparison to cbNK cells. In all cases, WNTi-NK cells exhibited a strong bias for cytolytic degranulation over cytokine production, while WNTd-NK cells were biased for IFNg secretion. Similarly, WNTi-NK cells exhibit superior ADCC-mediated cell killing of Raji cells.We then turned to the well-characterized murine embryo to determine whether HSC-independent NK cell progenitors are developmentally conserved. Assessing NK cell potential via explant culture, we found that as early as E7.5, yolk sac explants give rise to NK cells, as well as primitive and definitive erythroid progenitors. Further, we find that murine E9.5 yolk sac kit+CD41+CD16/32+ erythro-myeloid progenitors (EMP) give rise to NK cells ex vivo. Similar to hPSC WNTi-NK cells, EMP-derived NK cells were larger and more granular, and emerged alongside a granulocyte population in explant culture. Thus, the murine yolk sac harbors unique NK cell potential, from a committed myeloid progenitor, prior to HSC emergence.Collectively, these studies suggest that ontological origin is an unexpectedly important consideration in the design of hPSC-derived NK cell-based therapeutics, and raise new questions regarding the potential of early hematopoietic progenitors in the mammalian embryo. DisclosuresFehniger:Celgene: Research Funding; Cyto-Sen Therapeutics: Consultancy; Altor BioScience: Research Funding; Affimed: Research Funding; NIH/NCI: Other: R01 CA205239, P50CA171963. Palis:Rubies Therapeutics: Consultancy.

Umbilical Cord Blood-Derived Natural Killer Cells Combined with Bevacizumab for Colorectal Cancer Treatment.

Colorectal cancer (CRC) is among the cancers with the highest incidence globally, and it currently ranks as the fourth leading cause of cancer-related deaths worldwide. Novel strategies for the treatment of advanced CRC are urgently needed, and adoptive transfer of allogeneic natural killer (NK) cells represents an attractive option. In this study, we successfully expanded NK cells from umbilical cord blood (UCB) with membrane-bound interleukin (IL)-21, termed eUCB-NK cells. eUCB-NK cells efficiently lysed CRC cell lines in vitro and secreted significantly higher levels of interferon-γ, tumor necrosis factor-α, granulocyte-macrophage colony stimulating factor, and chemokine ligand 3 compared with IL-2-stimulated NK cells. Adoptive transfer of these NK cells significantly inhibited the growth of HT29 xenografts, whereas LoVo tumors were not effectively controlled with eUCB-NK cells. Higher numbers of NK cells inside HT29 tumors, not seen in LoVo tumors, might contribute to the differences in response to eUCB-NK cells. Bevacizumab increased extravasation of adoptively transferred NK cells into LoVo tumors and improved the therapeutic activity of eUCB-NK cells. These results justify clinical translation of UCB-derived NK cell-based therapeutics, used alone or in combination with bevacizumab, as a novel treatment option for patients with CRC.

3175 - Ontogeny as a Critical Determinant of Natural Killer Cell Potential and Function

Hematopoietic development during mammalian embryogenesis is comprised of a restricted primitive program of primitive erythroid, megakaryocytic, and macrophage lineages, and a definitive program of definitive erythroid, myeloid and lymphoid potential and hematopoietic stem cell (HSC)-independent and dependent processes. Interestingly, progenitors of natural killer (NK) cells, but not B- or T-cells, have been found in the early human yolk sac, suggesting that NK cells may arise from HSC-independent sources. NK cells are innate lymphoid cells and their derivation from human pluripotent stem cells (hPSCs) is an exciting alternative for adoptive immunotherapy strategies. We have developed an hPSC differentiation method that separates primitive-like hematopoietic progenitors from HSC-independent erythro-myeloid-(T)lymphoid definitive-like potential. Using this system, we find that CD34+ cells from both populations harbor NK cell potential. Further, we find that murine E9.5 yolk sac kit+CD41+CD16/32 + erythro-myeloid progenitors give rise to NK cells ex vivo. As early as E7.5, yolk sac explants give rise to NK cells, as well as primitive and definitive erythroid progenitors. Thus, the murine yolk sac harbors NK cell potential prior to HSC emergence. NK cells from hPSC primitive-like progenitors (pNK cells) mature rapidly, are significantly more granular, and express very high levels of CD16 in comparison to their hPSC definitive-like counterparts (dNK cells) and cord blood-derived NK (cbNK) cells. Both pNK and dNK cells robustly respond to tumor targets and antibody-dependent cell-mediated cytotoxicity (ADCC) in comparison to cbNK cells. In response to K562 cells, pNK cells exhibit a 3-fold preference for cytolytic degranulation, while dNK cells are 3-fold more biased for IFNg secretion. Similarly, in response to ADCC pNK cells display 3-fold more TNFa and degranulation than dNK or cbNK cells. Collectively, these studies suggest that ontological origin is an unexpectedly important consideration in the design of hPSC-derived NK cell-based therapeutics, and raise new questions regarding the potential of early hematopoietic progenitors in the mammalian embryo.

Infusion of Umbilical Cord Blood-Derived Natural Killer Cells in Immune-Deficient Mice for the Treatment of Resistant Acute Myeloid Leukaemia

Adoptive transfer of allogeneic natural killer (NK) cells represents a promising treatment approach against acute myeloid leukaemia (AML). Success of this NK cell immunotherapy is dependent on obtaining high numbers of functional NK cells that have the potential to survive in vivo. The use of umbilical cord blood (UCB) CD34+ cells as a source of allogenic NK cells is an interesting method that can generate a readily available, non-invasive, off the shelf cellular product.We developed a cytokine-based culture method for the generation of NK cell products derived from CD34+hematopoietic progenitor cells (HPC) isolated from fresh UCB units. Immuno-phenotyping of ex vivo expanded NK cells showed typical inhibitory and activating NK receptors except for CD16 and the KIR receptors.UCB-derived NK cells displayed good cytolytic activity against NK-sensitive K562 cells with a percentage of specific lysis varying from 30 to 50%. Cytolysis was directly correlated to CD94 expression since CD94-sorted NK cells were responsible for all the in vitro cytolytic function of differentiated NKs against K562 cells. There was an inconstant susceptibility of patient-derived primary AML cells to UCB-derived NK lysis in vitro with a specific lysis ranging from 0 to 25%.We further characterized UCB-derived NK cells by investigating their toxicity, biodistribution, and anti-leukemic potential in vivo. As adoptive transfer of NK cells is an attractive approach for treating refractory leukemia, immune deficient mice were engrafted with a patient derived AML strain resistant to NK-mediated lysis and doxorubicin.After successful engraftment and randomization, leukemic mice were injected with either UCB- derived NK cells or NK cells from healthy donors (NKhds) or doxorubicin, with one control group that didn't receive any treatment. Mice were sacrificed after 2 weeks of treatment and leukemia load along with NK distribution were evaluated by flow cytometry in the blood, bone marrow (BM) and spleen.There was no evidence of toxicity of UCB-derived or healthy donors NK cells in mice. Both types of cells were preferentially found in the blood and in the spleen, even though NKhds reached much higher levels than UCB-derived NKs.As for treatment efficacy, none of our treatment showed anti-leukemic potential based on the absence of decrease of leukemic cells in BM, blood, and spleen. In vivo microenvironment didn't overcome resistance of the patient derived AML cell to NK lysis or to doxorubicin.Remarkably, all of the UCB derived NK cells founded in vivo expressed the CD94 whereas not more than 20% of the injected cells were positive for this marker. Whether it was by in vivo selection or by in vivo differentiation must be investigated.Interestingly, a small cell population with CD56 and CD34 double staining was distinguished in UCB-derived NK and NK healthy donor treated leukemic mice suggesting in vivo interaction between leukemic and NK cells. Further characterization of this population may help to understand the molecular mechanism of leukemic recognition by NK cells and resistance of leukemic cells to cytolysis.In conclusion, UCB-derived NK generation is feasible. Investigation of the role of CD94 in these cells is needed, as cell sorting by CD94 selection in addition to the CD56 could be an interesting approach in the future to select highly functional expanded NK cells before therapeutic use. Furthermore, infusion of UCB-derived NK cells into immune-deficient mice is achievable and non-toxic. However, in vivo environment didn't overcome primary in vitro resistance of AML cells despite an established interaction. Additional elucidation of AML resistance mechanisms to NK lysis is mandatory before therapeutic application. DisclosuresNo relevant conflicts of interest to declare.