Engineered Natural Killer Cells Research Articles

Highlight of 2023: Unlocking the therapeutic potential of natural killer cells-advances in adaptive functions, cellular engineering and immunotherapy.

Natural killer (NK) cells possess potent cytotoxicity against infected and cancerous cells and hold promise in the development of new immunotherapies. This article for the Highlights of 2023 Series focuses on current advances in NK cell biology in cancerous and infectious settings and highlights opportunities for therapeutic interventions, including engineered NK cell therapies and advancements in feeder cell technologies.

Augmenting the Antitumor Efficacy of Natural Killer Cells via SynNotch Receptor Engineering for Targeted IL-12 Secretion.

Natural killer (NK) cells are crucial components of innate immunity, known for their potent tumor surveillance abilities. Chimeric antigen receptors (CARs) have shown promise in cancer targeting, but optimizing CAR designs for NK cell functionality remains challenging. CAR-NK cells have gained attention for their potential to reduce side effects and enable scalable production in cancer immunotherapy. This study aimed to enhance NK cell anti-tumor activity by incorporating PD1-synthetic Notch (synNotch) receptors. A chimeric receptor was designed using UniProt database sequences, and 3D structure models were generated for optimization. Lentiviral transduction was used to introduce PD1-Syn receptors into NK cells. The expression of PD1-Syn receptors on NK cell surfaces was assessed. Engineered NK cells were co-cultured with PDL1+ breast cancer cells to evaluate their cytotoxic activity and ability to produce interleukin-12 (IL-12) and interferon-gamma (IFNγ) upon interaction with the target cells. This study successfully expressed the PD1-Syn receptors on NK cells. CAR-NK cells secreted IL-12 and exhibited target-dependent IFNγ production when engaging PDL1+ cells. Their cytotoxic activity was significantly enhanced in a target-dependent manner. This study demonstrates the potential of synNotch receptor-engineered NK cells in enhancing anti-tumor responses, especially in breast cancer cases with high PDL1 expression.

Surface Engineering of Natural Killer Cells with CD44-targeting Ligands for Augmented Cancer Immunotherapy.

Adoptive immunotherapy utilizing natural killer (NK) cells has demonstrated remarkable efficacy in treating hematologic malignancies. However, its clinical intervention for solid tumors is hindered by the limited expression of tumor-specific antigens. Herein, lipid-PEG conjugated hyaluronic acid (HA) materials (HA-PEG-Lipid) for the simple ex-vivo surface coating of NK cells is developed for 1) lipid-mediated cellular membrane anchoring via hydrophobic interaction and thereby 2) sufficient presentation of the CD44 ligand (i.e., HA) onto NK cells for cancer targeting, without the need for genetic manipulation. Membrane-engineered NK cells can selectively recognize CD44-overexpressing cancer cells through HA-CD44 affinity and subsequently induce in situ activation of NK cells for cancer elimination. Therefore, the surface-engineered NK cells using HA-PEG-Lipid (HANK cells) establish an immune synapse with CD44-overexpressing MIA PaCa-2 pancreatic cancer cells, triggering the "recognition-activation" mechanism, and ultimately eliminating cancer cells. Moreover, in mouse xenograft tumor models, administrated HANK cells demonstrate significant infiltration into solid tumors, resulting in tumor apoptosis/necrosis and effective suppression of tumor progression and metastasis, as compared to NK cells and gemcitabine. Taken together, the HA-PEG-Lipid biomaterials expedite the treatment of solid tumors by facilitating a sequential recognition-activation mechanism of surface-engineered HANK cells, suggesting a promising approach for NK cell-mediated immunotherapy.

Nicotinamide-Expanded Allogeneic Natural Killer Cells with CD38 Deletion, Expressing an Enhanced CD38 Chimeric Antigen Receptor, Target Multiple Myeloma Cells.

Natural killer (NK) cells are a vital component of cancer immune surveillance. They provide a rapid and potent immune response, including direct cytotoxicity and mobilization of the immune system, without the need for antigen processing and presentation. NK cells may also be better tolerated than T cell therapy approaches and are susceptible to various gene manipulations. Therefore, NK cells have become the focus of extensive translational research. Gamida Cell's nicotinamide (NAM) platform for cultured NK cells provides an opportunity to enhance the therapeutic potential of NK cells. CD38 is an ectoenzyme ubiquitously expressed on the surface of various hematologic cells, including multiple myeloma (MM). It has been selected as a lead target for numerous monoclonal therapeutic antibodies against MM. Monoclonal antibodies target CD38, resulting in the lysis of MM plasma cells through various antibody-mediated mechanisms such as antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis, significantly improving the outcomes of patients with relapsed or refractory MM. However, this therapeutic strategy has inherent limitations, such as the anti-CD38-induced depletion of CD38-expressing NK cells, thus hindering ADCC. We have developed genetically engineered NK cells tailored to treat MM, in which CD38 was knocked-out using CRISPR-Cas9 technology and an enhanced chimeric antigen receptor (CAR) targeting CD38 was introduced using mRNA electroporation. This combined genetic approach allows for an improved cytotoxic activity directed against CD38-expressing MM cells without self-inflicted NK-cell-mediated fratricide. Preliminary results show near-complete abolition of fratricide with a 24-fold reduction in self-lysis from 19% in mock-transfected and untreated NK cells to 0.8% of self-lysis in CD38 knock-out CAR NK cells. Furthermore, we have observed significant enhancements in CD38-mediated activity in vitro, resulting in increased lysis of MM target cell lines. CD38 knock-out CAR NK cells also demonstrated significantly higher levels of NK activation markers in co-cultures with both untreated and αCD38-treated MM cell lines. These NAM-cultured NK cells with the combined genetic approach of CD38 knockout and addition of CD38 CAR represent a promising immunotherapeutic tool to target MM.

Human iPSC-Derived NK Cells with Knock-in of the BCL2 G101V Mutation Are Resistant to Venetoclax and Demonstrate Improved Anti-AML Activity In Vivo

Treatment options for acute myeloid leukemia (AML) patients who are unfit for intensive chemotherapy are limited. Both targeted therapy and cellular therapy have been investigated, typically as separate treatments. For patients with AML unfit for intensive induction chemotherapy, venetoclax, a BCL-2 inhibitor, containing regimens have significantly improved treatment outcomes. However, patients treated long-term with venetoclax can develop resistance. Based on the characterization of the BCL2 G101V mutation that mediates resistance to venetoclax, we investigated the ability of homozygous BCL2 G101V knock-in in induced pluripotent stem cell (iPSC)-derived natural killer (NK) cells to promote resistance to venetoclax in these effector cells to enable concurrent treatment with venetoclax and the engineered iPSC-derived NK cells that we hypothesize will provide improved NK cell-mediated killing of AML. Our group has pioneered the production of genetically modified NK cells from human iPSCs. iPSCs provide an advantage of a stable platform for genome engineering and previous studies demonstrate we can engineer iPSCs to express or delete genes of interest to derive genetically modified iPSC-NK cells with improved anti-tumor activity. To generate iPSC-derived NK cells with resistance to venetoclax, we employed CRISPR-Cas9 technology to knock-in the BCL2 G101V mutation (BCL2 G101V) in iPSCs. iPSCs homozygous for BCL2 G101V were selected and differentiated to NK cells. Homozygous BCL2 G101V engineered iPSC-NK cells demonstrated resistance to venetoclax compared to wildtype (WT) iPSC-NK cells in vitro. BCL2 G101V iPSC-NK cells were 94-fold more resistant to venetoclax compared to wildtype iPSC NK cells with an EC50 of 6018 nM, above the serum levels of patients receiving venetoclax. Analysis of cell surface proteins demonstrated that both sets of iPSC-NK cells had a typical NK cell phenotype with no differences in expression of receptors analyzed. There was no difference seen in cytotoxicity against K562 tumor cells between BCL2 G101V iPSC-NK cells and WT-iPSC NK cells. Additional functional analyses demonstrated that activity of the BCL2 G101V iPSC NK cells was preserved upon exposure to venetoclax. Cytotoxic activity, as measured by CD107a expression on WT iPSC-NK cells stimulated by MOLM13 AML tumors cells, was reduced nearly 3-fold upon addition of venetoclax. In contrast, activation of BCL2 G101V iPSC NK cells was not significantly affected by addition of venetoclax. This resistance to venetoclax was confirmed in longer term 36-hour Incucyte cytotoxicity assays where BCL2 G101V iPSC-NK cells demonstrated more than 10-fold increase in anti-AML activity compared to the WT-iPSC-NK cells. We then conducted in vivo studies to test the WT and engineered NK cells with and without addition of venetoclax in an AML xenograft model using NSG mice (Figure Panels A-D). These studies used MOLM13 AML cells made resistant to venetoclax and demonstrated that without venetoclax treatment, both the WT and the BCL2 G101V iPSC NK cells mediate effective anti-AML killing. With addition of venetoclax, the WT NK cells were unable to effectively kill the AML cells while the BCL2 G101V iPSC cells mediated potent anti-AML activity and demonstrated significantly improved survival when the NK cells are given in combination with venetoclax. Specifically, in this system, the mice treated with WT iPSC-NK cells had a median survival of 22.8 days while the median survival of mice treated with the BCL2 G101V iPSC NK cells was not reached (p<0.01) Intriguingly, BCL2 G101V iPSC NK cells also demonstrated improved activity against MOLM13 cells resistant to venetoclax. Together our results demonstrate that iPSC-NK cells can be engineered to generate venetoclax-resistance for use in combination with concurrent venetoclax therapy to markedly improve treatment of AML. Furthermore, this work demonstrates that novel drug resistance mechanisms can be introduced via genome engineering into iPSC-derived NK cells as a new strategy to produce improved cell products for “off-the-shelf” therapy.

Potentiation of natural killer cells to overcome cancer resistance to NK cell-based therapy and to enhance antibody-based immunotherapy.

Natural killer (NK) cells are cellular components of the innate immune system that can recognize and suppress the proliferation of cancer cells. NK cells can eliminate cancer cells through direct lysis, by secreting perforin and granzymes, or through antibody-dependent cell-mediated cytotoxicity (ADCC). ADCC involves the binding of the Fc gamma receptor IIIa (CD16), present on NK cells, to the constant region of an antibody already bound to cancer cells. Cancer cells use several mechanisms to evade antitumor activity of NK cells, including the accumulation of inhibitory cytokines, recruitment and expansion of immune suppressor cells such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs), modulation of ligands for NK cells receptors. Several strategies have been developed to enhance the antitumor activity of NK cells with the goal of overcoming cancer cells resistance to NK cells. The three main strategies to engineer and boost NK cells cytotoxicity include boosting NK cells with modulatory cytokines, adoptive NK cell therapy, and the employment of engineered NK cells to enhance antibody-based immunotherapy. Although the first two strategies improved the efficacy of NK cell-based therapy, there are still some limitations, including immune-related adverse events, induction of immune-suppressive cells and further cancer resistance to NK cell killing. One strategy to overcome these issues is the combination of monoclonal antibodies (mAbs) that mediate ADCC and engineered NK cells with potentiated anti-cancer activity. The advantage of using mAbs with ADCC activity is that they can activate NK cells, but also favor the accumulation of immune effector cells to the tumor microenvironment (TME). Several clinical trials reported that combining engineered NK cells with mAbs with ADCC activity can result in a superior clinical response compared to mAbs alone. Next generation of clinical trials, employing engineered NK cells with mAbs with higher affinity for CD16 expressed on NK cells, will provide more effective and higher-quality treatments to cancer patients.

Lipid accumulation-mediated histone hypoacetylation drives persistent NK cell dysfunction in anti-tumor immunity

Hyperlipidemia impairs anti-tumor immune responses and is closely associated with increased human cancer incidence and mortality. However, the underlying mechanisms are not well understood. In the present study, we show that natural killer (NK) cells isolated from high-fat-diet mice or treated with oleic acid (OA) invitro exhibit sustainable functional defects even after removal from hyperlipidemic milieu. This is accompanied by reduced chromatin accessibility in the promoter region of NK cell effector molecules. Mechanistically, OA exposure blunts P300-mediated c-Myc acetylation and shortens its protein half-life in NK cells, which in turn reduces P300 accumulation and H3K27 acetylation and leads to persistent NK cell dysfunction. NK cells engineered with hyperacetylated c-Myc mutants surmount the suppressive effect of hyperlipidemia and display superior anti-tumor activity. Our findings reveal the persistent dysfunction of NK cells in dyslipidemia milieu and extend engineered NK cells as a promising strategy for tumor immunotherapy.

CAR-NK Cells Generated with mRNA-LNPs Kill Tumor Target Cells In Vitro and In Vivo.

Natural killer (NK) cells are cytotoxic lymphocytes that are critical for the innate immune system. Engineering NK cells with chimeric antigen receptors (CARs) allows CAR-NK cells to target tumor antigens more effectively. In this report, we present novel CAR mRNA-LNP (lipid nanoparticle) technology to effectively transfect NK cells expanded from primary PBMCs and to generate functional CAR-NK cells. CD19-CAR mRNA and BCMA-CAR mRNA were embedded into LNPs that resulted in 78% and 95% CAR expression in NK cells, respectively. BCMA-CAR-NK cells after transfection with CAR mRNA-LNPs killed multiple myeloma RPMI8226 and MM1S cells and secreted IFN-gamma and Granzyme B in a dose-dependent manner in vitro. In addition, CD19-CAR-NK cells generated with CAR mRNA-LNPs killed Daudi and Nalm-6 cells and secreted IFN-gamma and Granzyme B in a dose-dependent manner. Both BCMA-CAR-NK and CD19-CAR-NK cells showed significantly higher cytotoxicity, IFN-gamma, and Granzyme B secretion compared with normal NK cells. Moreover, CD19-CAR-NK cells significantly blocked Nalm-6 tumor growth in vivo. Thus, non-viral delivery of CAR mRNA-LNPs can be used to generate functional CAR-NK cells with high anti-tumor activity.

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.

Generation and Functional Characterization of Anti-CD19 Chimeric Antigen Receptor-Natural Killer Cells from Human Induced Pluripotent Stem Cells.

Natural killer (NK) cells are a part of innate immunity that can be activated rapidly in response to malignant transformed cells without prior sensitization. Engineering NK cells to express chimeric antigen receptors (CARs) allows them to be directed against corresponding target tumor antigens. CAR-NK cells are regarded as a promising candidate for cellular immunotherapy alternatives to conventional CAR-T cells, due to the relatively low risk of graft-versus-host disease and safer clinical profile. Human induced pluripotent stem cells (iPSCs) are a promising renewable cell source of clinical NK cells. In the present study, we successfully introduced a third-generation CAR targeting CD19, which was validated to have effective signaling domains suitable for NK cells, into umbilical cord blood NK-derived iPSCs, followed by a single-cell clone selection and thorough iPSC characterization. The established single-cell clone of CAR19-NK/iPSCs, which is highly desirable for clinical application, can be differentiated using serum- and feeder-free protocols into functional CAR19-iNK-like cells with improved anti-tumor activity against CD19-positive hematologic cancer cells when compared with wild-type (WT)-iNK-like cells. With the feasibility of being an alternative source for off-the-shelf CAR-NK cells, a library of single-cell clones of CAR-engineered NK/iPSCs targeting different tumor antigens may be created for future clinical application.

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.

Abstract 2904: CAT-179, an allogeneic NK cell product expressing HER2-CAR, IL-15 and TGFβ dominant negative receptor, durably regresses HER2-expressing xenograft tumors in mice

Abstract While chimeric antigen receptor (CAR)-engineered immune cell therapies have been at the forefront of cancer immunotherapy for hematological malignancies, patients with solid tumors have yet to benefit from such therapies. Engineered, off-the-shelf, allogeneic natural killer (NK) cells are particularly attractive as cell therapies for solid tumors given their clinical safety, efficacy, and multimodal recognition of tumor cells. We describe here the pre-clinical pharmacokinetics, efficacy, biodistribution and safety of CAT-179, a novel allogeneic, cryopreserved CAR-NK cell therapy, in naïve animals as well as multiple xenograft models of HER2-amplified ovarian and gastric cancer. CAT-179 cells are engineered to express an optimized HER2-directed CAR to effectively target tumor cells, a transforming growth factor b (TGFβ) dominant negative receptor (DNR) to protect against TGFβ-mediated immunosuppression, and interleukin-15 (IL-15) to enhance NK cell persistence. A single intravenous (IV) dose of CAT-179 resulted in IL-15-dependent (p<0.0001) expansion and persistence of CAT-179 cells for at least 140 days in NOD-scid IL2Rgnull (NSG) mice, peaking at approximately 15,000 cells/µL of blood (by day 60). Persisting CAT-179 NK cell levels at day 60 were functionally active and significantly reduced tumor burden when challenged intraperitoneally (IP) with HER2+ SKOV3-luc tumor cells. No significant changes in body weight or condition were observed during this study. The therapeutic anti-tumor activity of CAT-179 against established tumors was assayed using two different xenograft models. In the first model, NSG mice were given an IP dose of 1 million SKOV3-luc tumor cells (derived from ovarian cancer) followed by either 4 million CAT-179 or control NK cells on days 4, 11 and 18. CAT-179 dosed animals showed a rapid and sustained 95% decline in tumor burden (p<0.0001) and a significant extension in survival relative to animals dosed with control NK cells (p<0.0001). In the second model, 1 million HER2+ N87 cancer cells (derived from gastric cancer) were implanted subcutaneously into the right flank of NSG mice. When tumors reached 70mm3, a single IV dose of 2M CAT-179 or control NK cells was administered. CAT-179 dosed animals showed a 96% durable tumor regression and significant survival benefit relative to animals dosed with control NK cells (p<0.0001). Efficacy strongly correlated with the circulating levels of CAT-179, which significantly infiltrated the tumor xenograft. Our pre-clinical results demonstrate the potential of CAT-179 as a novel, durable, and off-the-shelf cell therapy to overcome the challenges associated with solid tumors and provide quantitative insights into pharmacokinetics, pharmacodynamics and anti-tumor activity of engineered NK cells expressing CAR, TGFb DNR and IL-15. Citation Format: Bashar Hamza, Angela Nunez, Marilyn Marques, Alexia Barandiaran, Henry Moreno, Finola Moore, Meghan Walsh, Eugene Choi, Kisha Pradhan, Krista Daniel, Jennifer Johnson, Charlotte Franco, Andres Alvarez, Karl Malakian, Keith H. Wong, Joseph Gold, Vipin Suri, Dominic Picarella. CAT-179, an allogeneic NK cell product expressing HER2-CAR, IL-15 and TGFβ dominant negative receptor, durably regresses HER2-expressing xenograft tumors in mice [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 2904.

Abstract 2902: Off-the-Shelf CAR-NK cells engineered to express calibrated release IL-15 exhibit enhanced persistence and anti-tumor activities

Abstract Chimeric antigen receptor (CAR) natural killer (NK) cell therapy is an attractive immunotherapy strategy due to potential for increased anti-tumor activity and favorable safety. Allogeneic donor derived NK cells have shown promising clinical outcomes in both hematological and solid tumor malignancies but have a short lifespan in the absence of cytokine support. Interleukin (IL)-15 is a pleiotropic cytokine that promotes the survival, proliferation, and cytotoxicity of NK cells. In this study, we engineered human peripheral blood-derived NK cells to co-express a CAR and calibrated release (cr) IL-15 and studied how crIL-15 affected CAR-NK cell functions. Senti Bio has designed the calibrated release technology to simultaneously produce membrane bound and secreted cytokines, such as IL-15 and IL-12, to provide autocrine and paracrine activity. We further validated crIL-15 activity in vitro and demonstrated enhanced NK cell persistence, tumor killing and autocrine activity in CAR NK cells as well as paracrine stimulation of neighboring T cells and NK cells via pSTAT5 activation. Additionally, we examined in vivo persistence and biodistribution of NK cells engineered with crIL-15 and a nanoluc reporter. crIL-15 NK cells were intravenously (i.v.) injected into NSG mice. These NK cells were detected in the lung, femur, spleen, liver and stomach 1 day post injection by bioluminescence imaging and polymerase chain reaction (PCR) and lasted up to 20 days in the lung. In addition, crIL-15 increased CAR-NK cells persistence in a dose-dependent manner compared to unengineered NK cells. Injection of higher CAR-NK cell numbers (15× 106 vs 7.5× 106 CAR+ cells per mouse) or multiple NK dosages (1 vs 3 doses) both contributed to prolonged persistence. Finally, we studied how crIL-15 affected CAR-NK cell anti-tumor function in acute myeloid leukemia (AML) xenograft models. MV4-11-Fluc AML tumor cells were co-injected with engineered NK cells expressing a FLT3 and/or CD33 bivalent activating CAR, a EMCN inhibitory CAR and crIL-15 into NSG-Tg (Hu-IL15) mice via i.v. injection. Our data showed that these CAR-NK cells significantly reduced MV4-11 tumor burden and prolonged mouse survival compared to unengineered NK cells. The improved anti-tumor functions correlated with IL-15 levels produced by the CAR-NK cells. In conclusion, our results demonstrated that crIL-15 can improve persistence and anti-tumor activity of CAR-NK cells. Citation Format: Chen-Ting Lee, Michelle Hung, Andrew Banicki, Wenqi Song, Niran Almudhfar, Deepika Kaveri, Priscilla Wong, Lawrence Naitmazi, Marcela Guzman, Alice Lam, Gozde Yucel, Timothy Lu, Alba G. Junca, Brian Garrison, Philip Lee. Off-the-Shelf CAR-NK cells engineered to express calibrated release IL-15 exhibit enhanced persistence and anti-tumor activities [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 2902.

Efficient Redirection of NK Cells by Genetic Modification with Chemokine Receptors CCR4 and CCR2B

Natural killer (NK) cells are a subset of lymphocytes that offer great potential for cancer immunotherapy due to their natural anti-tumor activity and the possibility to safely transplant cells from healthy donors to patients in a clinical setting. However, the efficacy of cell-based immunotherapies using both T and NK cells is often limited by a poor infiltration of immune cells into solid tumors. Importantly, regulatory immune cell subsets are frequently recruited to tumor sites. In this study, we overexpressed two chemokine receptors, CCR4 and CCR2B, that are naturally found on T regulatory cells and tumor-resident monocytes, respectively, on NK cells. Using the NK cell line NK-92 as well as primary NK cells from peripheral blood, we show that genetically engineered NK cells can be efficiently redirected using chemokine receptors from different immune cell lineages and migrate towards chemokines such as CCL22 or CCL2, without impairing the natural effector functions. This approach has the potential to enhance the therapeutic effect of immunotherapies in solid tumors by directing genetically engineered donor NK cells to tumor sites. As a future therapeutic option, the natural anti-tumor activity of NK cells at the tumor sites can be increased by co-expression of chemokine receptors with chimeric antigen receptors (CAR) or T cell receptors (TCR) on NK cells can be performed in the future.

Abstract A021: Chimeric antigen receptor armored natural killer cell immunotherapy for osteosarcoma

Abstract Over the last decade, Chimeric Antigen Receptor based T cell (CAR-T) therapy has developed into an effective immunotherapy for several cancers, primarily limited to those of hematological origin. In other cancers, especially solid tumors, CAR-T cell therapies have several shortcomings and clinical success has been underwhelming. Challenges of CAR-T cell therapy include tumor immune evasion through loss of target antigen expression by tumor cells and inhibition of CAR-T cell function by tumor expressed inhibitory molecules. Natural killer (NK) cells present an alternative to T cells that could be more effective due to their ability to perform both antigen dependent and independent killing. NK cells can mediate the direct killing of transformed cells with reduced or absent MHC expression in addition to carrying out antibody dependent cell mediated cytotoxicity (ADCC) of cells bound by antibodies via the NK cell CD16A receptor. Engineering NK cells to express CARs will effectively enable them with additional antigen specific killing. Due to the multiple modalities for cancer cell killing, there is an increased interest in NK cells for cancer immunotherapy. As NK cells are not associated with graft versus host disease, neurotoxicity, long-term autoimmunity, nor cytokine release syndrome, they are more suited for use in allogeneic settings than T cells and have significant clinical potential for use as off-the-shelf products. However, previous publications and clinical trials have demonstrated that the use of unmanipulated NK cells to treat cancer is minimally effective, likely due to limited engraftment, little in vivo expansion or persistence, and suppression by the tumor microenvironment. NK cells activated and expanded with engineered feeder cells expressing membrane bound interleukin-21 (mbIL-21) and 4-1BBL have shown promising results clinically with high-risk myeloid malignancies and preclinically in several solid tumor models. Therefore, we hypothesize that activated/expanded CAR-NK cells that have been genetically edited can be used to successfully treat osteosarcoma, a disease for which patient outcome has not improved in over forty years. Our proposed objective is to evaluate the non-viral KI of several CARs, either alone or in combination, that optimally activate NK cell antigen-specific killing. Genetically engineered CAR-NK cells will be evaluated for enhanced therapeutic efficacy and safety in osteosarcoma models. Our preliminary data strongly supports the hypothesis that CAR-NK cell-based cancer immunotherapy can be fully realized using activated, genome engineered CAR-NK cells. Citation Format: Gabrielle Robbins, Kenta Yamomoto, Walker Lahr, Joseph Skeate. Chimeric antigen receptor armored natural killer cell immunotherapy for osteosarcoma [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A021.

Lipid-mediated ex vivo cell surface engineering for augmented cellular functionalities.

Once administrated, intercellular adhesion to recognize and/or arrest target cells is essential for specific treatments, especially for cancer or tumor. However, immune cells administrated into the tumor-microenvironment could lose their intrinsic functionalities such as target recognition ability, resulting in an ineffective cancer immunotherapy. Various manipulation techniques for decorating functional moieties onto cell surface and enhancing target recognition have been developed. A hydrophobic interaction-mediated ex-vivo cell surface engineering using lipid-based biomaterials could be a state-of-the-art engineering technique that could achieve high-efficiency cell surface modification by a single method without disturbance of intrinsic characteristics of cells. In this regard, this review provides design principles for the development of lipid-based biomaterials with a linear structure of lipid, polyethylene glycol, and functional group, strategies for the synthesis process, and their practical applications in biomedical engineering. Especially, we provide new insights into the development of a novel surface coating techniques for natural killer (NK) cells with engineering decoration of cancer targeting moieties on their cell surfaces. Among immune cells, NK cells are interesting cell population for substituting T cells because of their excellent safety and independent anticancer efficacy. Thus, optimal strategies to select cancer-type-specific targeting moieties and present them onto the surface of immune cells (especially, NK cells) using lipid-based biomaterials could provide additional tools to capture cancer cells for developing novel immune cell therapy products. Enhanced anticancer efficacies by surface-engineered NK cells have been demonstrated both in vitro and in vivo. Therefore, it could be speculated that recent progresses in cell surface modification technology via lipid-based biomaterials could strengthen immune surveillance and immune synapses for utilization in a next-generation cancer immunotherapy, beyond currently available genetic engineering tool such as chimeric antigen receptor-mediated immune cell modulation.

Natural Killer Cell-targeted Immunotherapy for Cancer.

Natural Killer (NK) cells were initially described in the early 1970s as major histocompatibility complex unrestricted killers due to their ability to spontaneously kill certain tumor cells. In the past decade, the field of NK cell-based treatment has been accelerating exponentially, holding a dominant position in cancer immunotherapy innovation. Generally, research on NK cell-mediated antitumor therapies can be categorized into three areas: choosing the optimal source of allogeneic NK cells to yield massively amplified "off-the-shelf" products, improving NK cell cytotoxicity and longevity, and engineering NK cells with the ability of tumor-specific recognition. In this review, we focused on NK cell manufacturing techniques, some auxiliary methods to enhance the therapeutic efficacy of NK cells, chimeric antigen receptor NK cells, and monoclonal antibodies targeting inhibitory receptors, which can significantly augment the antitumor activity of NK cells. Notably, emerging evidence suggests that NK cells are a promising constituent of multipronged therapeutic strategies, strengthening immune responses to cancer.

Engineered natural killer cells impede the immunometabolic CD73-adenosine axis in solid tumors.

Immunometabolic reprogramming due to adenosine produced by CD73 (encoded by the 5'-ectonucleotidase gene NT5E) is a recognized immunosuppressive mechanism contributing to immune evasion in solid tumors. Adenosine is not only known to contribute to tumor progression, but it has specific roles in driving dysfunction of immune cells, including natural killer (NK) cells. Here, we engineered human NK cells to directly target the CD73-adenosine axis by blocking the enzymatic activity of CD73. In doing so, the engineered NK cells not only impaired adenosinergic metabolism driven by the hypoxic uptake of ATP by cancer cells in a model of non-small-cell lung cancer, but also mediated killing of tumor cells due to the specific recognition of overexpressed CD73. This resulted in a 'single agent' immunotherapy that combines antibody specificity, blockade of purinergic signaling, and killing of targets mediated by NK cells. We also showed that CD73-targeted NK cells are potent in vivo and result in tumor arrest, while promoting NK cell infiltration into CD73+ tumors and enhancing intratumoral activation.

Abstract 6070: Functional natural killer cells derived from engineered hiPSC with hypoimmunity gene combo demonstrate hypoimmunity features in evading host attacks

Abstract Engineered human induced pluripotent stem cells (hiPSC)-derived allogeneic Natural Killer (NK) cells are emerging as promising safe and effective off-the-shelf cell therapy drugs. Repeated dosing of NK cells can partly compensate the relatively shorter persistence of NK cells compared with chimeric antigen receptor T cells (CAR-T); However, with each repeat, the persistence and efficacy are increasingly challenged by activation of host innate and adaptive immunity. Thus, reducing immunogenicity of allogeneic NK cells holds promise for better efficacy. In this study, we report a combination of “hypoimmunity” gene edits including multiple transgene knock-ins and both class I and class II MHC knockouts (2KO). We show that hiPSC engineered by the hypoimmunity combo can be efficiently differentiated into NK cells, comparable to the non-engineered ones. This is contrary to the notion from mouse studies that NK cells devoid of class I molecules are hypo-responsive, these engineered NK cells can be expanded by aAPC (artifitial Antigen Presenting Cells, a K562 cell line with surface expression of mbIL-21 and CD137L) and are capable of killing tumor cells, Additionally, we show that the engineered NK cells can evade T cell immunity, as examined by in vitro T cell proliferation and cytotoxicity assays. A humanized mouse model with transplanted CD34-positive human hematopoietic stem cells confirmed that the engineered NK cells can persist longer than WT and 2KO NK cells. Hypoimmune-QN-019 NK cells are generated by incorporating hypoimmunity gene combo edits into our hiPSC-derived NK cell clinical candidate QN-019 which has 3 transgenes including membrane-bound IL-15, high affinity non-cleavable CD16 and CAR targeting CD19. Comparing to QN-019, hypoimmune-QN-019 displayed better efficacy in humanized CDX mouse model in clearing CD19-positive cancer cells. Taken together, we have engineered hiPSC-derived allogeneic NK cells with hypoimmunity features, which hold great promise in becoming an off-the-shelf drug with improved in vivo persistence and efficacy for repeated dosing. Citation Format: Jiabiao Hu, Xiangjun He, Jing Xu, Yixuan Zhou, Yanan Yue, Yangbin Gao, George Church, Luhan Yang. Functional natural killer cells derived from engineered hiPSC with hypoimmunity gene combo demonstrate hypoimmunity features in evading host attacks [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6070.

DAP10 integration in CAR-T cells enhances the killing of heterogeneous tumors by harnessing endogenous NKG2D

Although chimeric antigen receptor T (CAR-T) cells have achieved remarkable successes in hematological malignancies, the efficacies of CAR-T cells against solid tumors remains unsatisfactory. Heterogeneous antigen expression is one of the obstacles on its effective elimination of solid cancer cells. DNAX-activating protein 10 (DAP10) interacts with natural killer group 2D (NKG2D), acting as an adaptor that targets various malignant cells for surveillance. Here, we designed a DAP10 chimeric receptor that utilized native NKG2D on T cells to target NKG2D ligand-expressing cancer cells. We then tandemly incorporated it with anti-glypican 3 (GPC3) single-chain variable fragment (scFv) to construct a dual-antigen-targeting system. T cells expressing DAP10 chimeric receptor (DAP10-T cells) displayed with an enhancement on both cytotoxicity and cytokine secretion against solid cancer cell lines, and its tandem connection with anti-GPC3 scFv (CAR GPC3-DAP10-T cells) exhibited a dual-antigen-targeting capacity on eliminating heterogeneous cancer cells in vitro and suppressing the growth of heterogeneous cancer in vivo. Thus, this novel dual-targeting system enabled a high efficacy on killing cancer cells and extended the recognition profile of CAR-T cells toward tumors, which providing a potential strategy on treatment of solid cancer clinically.