iPSC-derived natural killer cells expressing the FcγR fusion CD64/16A can be armed with antibodies for multitumor antigen targeting

BACKGROUND

Antibody therapies can direct natural killer (NK) cells to tumor cells, tumor-associated cells, and suppressive immune cells to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). This antigen-specific effector function of human NK cells is mediated by the IgG Fc receptor CD16A (FcγRIIIA). Preclinical and clinical studies indicate that increasing the binding affinity and avidity of CD16A for antibodies improves the therapeutic potential of ADCC. CD64 (FcγRI), expressed by myeloid cells but not NK cells, is the only high affinity IgG Fc receptor and is uniquely capable of stably binding to free monomeric IgG as a physiological function. We have reported on the generation of the FcγR fusion CD64/16A, consisting of the extracellular region of CD64 and the transmembrane and cytoplasmic regions from CD16A, retaining its signaling and cellular activity. Here, we generated induced pluripotent stem cell (iPSC)-derived NK (iNK) cells expressing CD64/16A as a potential adoptive NK cell therapy for increased ADCC potency.

METHODS

iPSCs were engineered to express CD64/16A as well as an interleukin (IL)-15/IL-15Rα fusion (IL-15RF) protein and differentiated into iNK cells. iNK cells and peripheral blood NK cells were expanded using irradiated K562-mbIL21-41BBL feeder cells and examined. NK cells, ovarian tumor cell lines, and therapeutic monoclonal antibodies were used to assess ADCC in vitro, performed by a DELFIA EuTDA assay or in real-time by IncuCyte assays, and in vivo. For the latter, we developed a xenograft mouse model with high circulating levels of human IgG for more physiological relevance.

RESULTS

We demonstrate that (1) iNK-CD64/16A cells after expansion or thaw from cryopreservation can be coupled to therapeutic antibodies, creating armed iNK cells; (2) antibody-armed iNK-CD64/16A cells can be redirected by added antibodies to target new tumor antigens, highlighting additional potential of these cells; (3) cytokine-autonomous activity by iNK-CD64/16A cells engineered to express IL-15RF; and that (4) antibody-armed iNK-CD64/16A cells thawed from cryopreservation are capable of sustained and robust ADCC in vitro and in vivo, as determined by using a modified tumor xenograft model with high levels of competing human IgG.

CONCLUSIONS

iNK cells expressing CD64/16A provide an off-the-shelf multiantigen targeting platform to address tumor heterogeneity and mitigate antigen escape.

A chimeric antigen receptor uniquely recognizing MICA/B stress proteins provides an effective approach to target solid tumors

BACKGROUND

The advent of chimeric antigen receptor (CAR) T cell therapies has transformed the treatment of hematological malignancies; however, broader therapeutic success of CAR T cells has been limited in solid tumors because of their frequently heterogeneous composition. Stress proteins in the MICA and MICB (MICA/B) family are broadly expressed by tumor cells following DNA damage but are rapidly shed to evade immune detection.

METHODS

We have developed a novel CAR targeting the conserved α3 domain of MICA/B (3MICA/B CAR) and incorporated it into a multiplexed-engineered induced pluripotent stem cell (iPSC)-derived natural killer (NK) cell (3MICA/B CAR iNK) that expressed a shedding-resistant form of the CD16 Fc receptor to enable tumor recognition through two major targeting receptors.

FINDINGS

We demonstrated that 3MICA/B CAR mitigates MICA/B shedding and inhibition via soluble MICA/B while simultaneously exhibiting antigen-specific anti-tumor reactivity across an expansive library of human cancer cell lines. Pre-clinical assessment of 3MICA/B CAR iNK cells demonstrated potent antigen-specific in vivo cytolytic activity against both solid and hematological xenograft models, which was further enhanced in combination with tumor-targeted therapeutic antibodies that activate the CD16 Fc receptor.

CONCLUSIONS

Our work demonstrated 3MICA/B CAR iNK cells to be a promising multi-antigen-targeting cancer immunotherapy approach intended for solid tumors.

FUNDING

Funded by Fate Therapeutics and NIH (R01CA238039).

Quadruple gene-engineered natural killer cells enable multi-antigen targeting for durable antitumor activity against multiple myeloma

Allogeneic natural killer (NK) cell adoptive transfer is a promising treatment for several cancers but is less effective for the treatment of multiple myeloma. In this study, we report on quadruple gene-engineered induced pluripotent stem cell (iPSC)-derived NK cells designed for mass production from a renewable source and for dual targeting against multiple myeloma through the introduction of an NK cell-optimized chimeric antigen receptor (CAR) specific for B cell maturation antigen (BCMA) and a high affinity, non-cleavable CD16 to augment antibody-dependent cellular cytotoxicity when combined with therapeutic anti-CD38 antibodies. Additionally, these cells express a membrane-bound interleukin-15 fusion molecule to enhance function and persistence along with knock out of CD38 to prevent antibody-mediated fratricide and enhance NK cell metabolic fitness. In various preclinical models, including xenogeneic adoptive transfer models, quadruple gene-engineered NK cells consistently demonstrate durable antitumor activity independent of exogenous cytokine support. Results presented here support clinical translation of this off-the-shelf strategy for effective treatment of multiple myeloma.

EXTH-64. IPSC-DERIVED NK CELLS EXHIBIT POTENT IN VITRO AND IN VIVO TUMORCIDAL ACTIVITY AGAINST PATIENT-DERIVED GLIOBLASTOMA STEM CELLS (GSCS)

INTRODUCTION

Natural Killer (NK) cells play pivotal roles in cancer immune surveillance and harbor potent anti-tumor activities. We have engineered an induced pluripotent stem cells (iPSCs) derived, NK cell (termed FT538) that express 1) a high-affinity non-cleavable CD16 Fc receptor to facilitate antibody engagement, 2) a membrane-bound IL-15/IL-15 receptor fusion to enhance NK activity and persistence and 3) a knock-out of CD38 to enhance NK metabolic fitness. FT538 is produced in a GMP-compliant manner as an off-the-shelf immunotherapy. Clinical experiences with FT538 have shown evidence of durable anti-tumor immunity after single administration in select lymphoma patients.

METHODS

We performed pre-clinical studies to characterize the tumoricidal activity of FT573 against glioblastomas.

RESULTS

Without specific antibody to engage CD16, FT538 exhibited potent in vitro activity against ~80% of a panel of isocitrate dehydrogenase wild-type patient-derived xenograft (PDX) glioblastoma lines, including MGG8. When directly injected into the murine brain, 50% of the FT538 persisted for > 2 weeks without addition of exogenous cytokine. Moreover, the mice exhibited no evidence of neurologic compromise, and brains harvested after injection show no signs of FT538 activation. In vivo intratumoral injection of FT538 into an orthotopically established MGG8 glioblastoma caused a ~20 fold increase in granzyme B release by FT538, with a comparable increase of cleaved-caspase 3 in the tumor. In independent experiments, > 90% of mice orthotopically implanted MGG8 survived beyond 100 days after intra-tumoral FT538 while all mice treated with mock injection died by 60 days. For glioblastoma PDX refractory to FT538, such as MGG4, tumoricidal activity of FT583 can be induced in vitro and in vivo by the addition of a tri-specific engager targeting B7H3, a surface protein highly expressed in glioblastomas.

CONCLUSION

Our results demonstrate great promise of FT538 as a glioblastoma therapy, with plans for translation into a first-in-human clinical trial.

Abstract 2761: FT573: Preclinical development of multiplexed-engineered iPSC-derived NK cells expressing a novel camelid nanobody chimeric antigen receptor (CAR) targeting pan-cancer antigen B7-H3

Introduction: B7-H3 (CD276) has gained significant clinical interest as a pan-tumor target antigen for development of various immuno-oncology agents. Due to its broad expression on a wide variety of solid tumors and minimal expression on normal tissues, B7-H3 is an ideal tumor antigen target. Additionally, high levels of B7-H3 are found on “immunologically cold” tumors such as glioblastoma multiforme, prostate cancer, head and neck cancer and soft tissue sarcomas, which typically have poor response to approved immune therapies. To effectively target B7-H3 with an off-the-shelf cellular therapy, we describe here the development of camB7-H3 CAR-NK cell utilizing our iPSC platform to engineer multiple modalities into a clonal iPSC line, which can serve as the starting cell source for mass production of off-the-shelf, iPSC-derived CAR-NK cells (CAR-iNK cells).

Methods: A camelid nanobody specific for human B7-H3 (camB7-H3) was discovered using a phage display library and validated in functional assays. camB7-H3 CAR-iNK cells were designed to 1) express membrane-bound IL-15/IL-15 receptor fusion for enhanced persistence, 2) have a CD38 knockout to improve metabolic fitness, 3) express a high-affinity non-cleavable CD16 to maximize ADCC when combined with a therapeutic antibody, and 4) express an anti-camB7-H3 CAR optimized for NK cell signaling. As the initial preclinical study, camB7-H3 CAR-iNK cells were assessed using flow cytometry-based functional assays evaluating CD107a and IFNγ or xCelligence target killing assays against B7-H3 transgenic or naturally expressing tumor cell lines.

Results: The camelid single domain B7-H3 initially tested in CAR-T exhibited B7-H3 specific binding and specific activity against several solid tumor cell lines (breast, ovarian, prostate, lung). We next produced camB7-H3 CAR-iNK cells and demonstrated superior B7-H3-specific target elimination compared to untransduced iNK cells. These results were seen across multiple tumor lines representing various solid tumor indications. Further enhancement of anti-tumor efficacy was seen when combined with therapeutic antibodies, including trastuzumab and cetuximab.

Conclusions: We have successfully produced and validated the specificity and function of an engineered camB7-H3 CAR-iNK cell exhibiting robust target killing and on-target specificity. To our knowledge, this is the first camelid nanobody antigen recognition domain reported in a CAR-NK cell to be used as an off-the-shelf immunotherapy. The combining camB7-H3 CAR-NK with monoclonal antibodies targeting HER2 and EGFR as a dual targeting approach will add additional tumor specificity, further increase the efficacy of tumor cell elimination and prevent antigen escape. Additional camB7-H3 CAR-iNK cell preclinical studies are in process and will be discussed.

Citation Format: Nicholas Zorko, Frank Cichocki, John Goulding, Bryan Hancock, Robert Blum, Mochtar Pribadi, Bjoern Gaertner, Tom Lee, Martin Felices, Ryan Bjordahl, Bahram Valamehr, Jeffrey S. Miller. FT573: Preclinical development of multiplexed-engineered iPSC-derived NK cells expressing a novel camelid nanobody chimeric antigen receptor (CAR) targeting pan-cancer antigen B7-H3 [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 2761.

Abstract 4190: Combining dual CAR iPSC-derived immune cells with antibody for multi-antigen targeting to overcome clonal resistance in multiple myeloma

Resistance to CAR-T cell therapy through antigen loss and clonal heterogeneity is a major limiting factor in achieving durable responses, even in highly persistent cell therapies. Simultaneous targeting of multiple tumor antigens with a single therapeutic modality offers the potential to treat heterogeneous tumor populations, prevent antigen escape, and induce durable clinical remission. Here, we demonstrate the application of a unique dual-CAR approach simultaneously targeting two tumor associated antigens (TAA) for the treatment of multiple myeloma (MM) using an off-the-shelf induced pluripotent stem cell (iPSC) derived NK cell platform. The iPSC background has been functionally enhanced and can be combined with therapeutic antibodies. A CAR targeting B cell maturation antigen (BCMA), a well-defined TAA in MM, was designed utilizing a previously published high-affinity binding sequence shown to exhibit high selectivity to BCMA with enhanced recognition of low-BCMA expressing myeloma cells (Bluhm et al., Molec Ther 2018). This CAR was combined with a companion CAR targeting the pan-TAAs, MICA and MICB. The CAR binding sequence targets the conserved α3 domain of MICA/MICB, which we have previously shown to inhibit MICA/B shedding by blocking the putative cleavage site (Andrade et al., Science 2018). The designed anti-MICA/B-α3 CAR exhibits selective targeting potential against a broad range of tumor types. To determine the suitability of co-targeting BCMA and MICA/B in MM, we surveyed surface expression of BCMA and MICA/B on a variety of MM cancer cell lines and observed a complimentary pattern of co-expression compatible with a dual-CAR to broaden the targeting approach of malignant plasma cells. In a reductionist approach, dual CAR-iNK cells exhibited antigen-specific activation, degranulation and cytotoxicity against a Nalm6 target line constitutively expressing the BCMA and MICA/B. Similar trends were observed in a series of long-term cytotoxicity assays against several MM lines, consistent with antibody staining on target cells, illustrating that co-targeting of MICA/B and BCMA expands the breadth of coverage against MM. Known modulators of antigen expression were tested for their ability to provide further depth of response, and therapeutic antibodies such as anti-CD38 were tested in combination to exploit the non-cleavable CD16 and CD38KO edits in the iPSC backbone. These combinations were further tested in vivo against a disseminated model of multiple myeloma where BCMA/MICA dual CAR-iNK cells demonstrated superior tumor control relative to single-CAR controls, and TGI was augmented with the addition of Daratumamab. These data highlight the applicability of a multi-targeted approach in MM patients, whereby MM dual-CAR NK and/or T cells maintain responsiveness to malignant cells that shed or downregulate tumor antigens to evade treatment.

Abstract 2828: A novel synthetic stealth receptor that redirects host immune cell alloreactivity and potentiates functional persistence of adoptively transferred off-the-shelf cell-based cancer therapy

Chimeric antigen receptor (CAR) T-cell therapies have revolutionized the treatment of hematologic malignancies and have shown significant potential in solid tumor indications. However, logistical complexities associated with patient-specific CAR T-cell therapies often limit broad accessibility. Many of these challenges can be overcome with an allogeneic cellular product, but immune cell-mediated rejection of allogeneic cellular therapies remains a significant concern. Both allogeneic and autologous cell therapies currently rely on lymphodepleting conditioning to modulate the immune system and create greater access to homeostatic cytokines. However, protracted lympho-conditioning has been associated with poor immune reconstitution and increased susceptibility to opportunistic infections. Therefore, an ideal allogeneic cell therapy would be able to avoid immune rejection while reducing or eliminating the need for chemotherapeutic conditioning to deplete host lymphocytes.

To address many of these challenges, we engineered our novel alloimmune defense receptor (ADR) that targets 41BB+ alloreactive immune cells while providing a CD3z signaling boost into our off-the-shelf iPSC derived NK cells expressing anti-CD19 CAR (CAR iNK). The ability of ADR+ CAR iNK cells to resist alloimmune rejection was tested by co-culturing ADR+ CAR iNK cells with allogeneic PBMCs from ten donors in a mixed lymphocyte reaction assay. Notably, ADR+ CAR iNK cells co-cultured with allogeneic PBMCs persisted to similar levels as the PBMC-free culture while ADR negative CAR iNK cells were eliminated when co-cultured with allogeneic PBMCs. Furthermore, all PBMC donors screened in ADR+ CAR iNK cell co-cultures showed ablation of reactive 41BB+ NK and T cells, with non-activated T cells remaining intact.

CAR iNK cells +/- ADR were then compared in a Nalm6 disseminated in vivo model for anti-tumor efficacy. ADR+ CAR iNK cells and their ADR negative counterparts were found to equivalently control tumor. Building on this tumor model, we co-infused allogeneic T cells to mimic an immuno-competent setting. The data demonstrated that ADR negative CAR iNK cells were depleted and were unable to control tumor growth while significant levels of allogeneic T cells persisted. In contrast, ADR+ CAR iNK cells were able to resist allogeneic T cell attack, control tumor, and persist when compared to the ADR negative control.

Collectively, our preliminary data suggest that ADR-armed CAR iNK cells withstand immune cell-mediated rejection with uncompromised effector function. We are actively developing models to confirm our initial finding that ADR+ effector cells also benefit from their engagement with alloreactive cells in immuno-competent settings to promote enhanced anti-tumor responses, proliferation, and persistence.

Citation Format: Alan M. Williams, Ken Hayama, Yijia Pan, Brian Groff, Rina Mbofung, Lauren Fong, Nicholas Brookhouser, Berhan Mandefro, Ramzey Abujarour, Tom Lee, Quirin Hammer, Karl-Johan Malmberg, Maksim Mamonkin, Ryan Bjordahl, Jode Goodridge, Bahram Valamehr. A novel synthetic stealth receptor that redirects host immune cell alloreactivity and potentiates functional persistence of adoptively transferred off-the-shelf cell-based cancer therapy [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 2828.

117 FT536 Path to IND: Ubiquitous targeting of solid tumors with an off-the-shelf, first-of-kind MICA/B-specific CAR-iNK cellular immunotherapy

Background

Chimeric antigen receptor (CAR)-T cell therapy has revolutionized cancer treatment, but it is associated with significant dose-limiting toxicities, restricted tumor targeting (limited by specific antigen expression), and, notably, a lack of multi-antigen targeting capability to mitigate tumor associated immune evasion and heterogeneity. Furthermore, dysfunctional starting material, product inconsistency, and small manufacturing lot size limits the application and on-demand availability of CAR-T cell therapy.

Methods

To overcome these considerable limitations, we have developed FT536, a first-of-kind, induced pluripotent stem cell (iPSC)-derived NK (iNK) cell with a novel CAR that ubiquitously targets cancer cells through canonical stress ligand recognition. We have previously reported FT536 recognizes the conserved α3 domain of the pan-tumor associated antigens MICA and MICB (MICA/B), and is derived from a renewable master iPSC line that contains multiplexed genetic edits to enhance effector cell functionality, persistence, and multi-antigen targeting capabilities via high affinity non cleavable CD16 (hnCD16) mediated antibody dependent cellular cytotoxicity (ADCC). Here we preview the nonclinical study for the investigational new drug (IND) application for FT536.

Results

Utilizing a manufacturing process analogous to pharmaceutical drug product development, we demonstrate FT536 can be consistently and uniformly produced with a greater than 4x10E7 fold cellular expansion per manufacturing campaign. Furthermore, FT536 can be cryopreserved at clinical scale to support off-the-shelf clinical application, with rapid product thaw and immediate patient infusion in an out-patient setting. Functional evaluation demonstrated that FT536 uniquely possesses potent and persistent antigen specific cytolytic activity against an array of solid and hematological tumor lines. Through its hnCD16 modality, FT536 can be utilized in combination with monoclonal antibodies to provide multi-antigen targeting capabilities and in conjunction with chemotherapeutics and/or radiation that augment surface MICA/B expression. In addition, directly thawed and infused FT536 demonstrated significant tumor growth inhibition in multiple solid and liquid in vivo xenograft models, in which tumor control was further enhanced in combination with a therapeutic antibody (figure 1). Finally, ongoing studies utilizing a lung adenocarcinoma model have highlighted the sustained persistence of FT536 in lung tissue up to 33 days following a single dose infusion without the need for exogenous cytokine support.

Abstract 117 Figure 1

FT536 provides statistically significant in vivo anti-tumor activity which is enhanced in combination with ADCC active monoclonal antibody therapy. (A-B) FT536 significantly reduced the number of lung and liver (not shown) metastases compared to CAR negative iNK control cells in a murine metastatic melanoma model using B16-F10 cells engineered to overexpress human MICA. (C-D) FT536 alone, and in combination with Herceptin, demonstrate significant tumor growth inhibition (TGI) compared to Herceptin alone in an orthotopic xenograft model of human lung adenocarcinoma.

Conclusions

Collectively, these studies demonstrate that FT536 is a highly potent, multi-tumor targeting CAR-iNK cell product that is uniform in composition and can be effectively and safely used off-the-shelf for on-demand treatment of multiple solid and hematological malignancies. An IND submission is planned for 2021, with an initial Phase 1 clinical trial to follow.

197 Novel FcyR recombinant fusion facilitates antibody arming of engineered iPSC-derived NK cells to enhance targeting and killing of ovarian cancer cells

Background

Ovarian cancer is a leading cause of cancer-related deaths among women due to the development of therapeutic resistance. Natural killer (NK) cells are cytotoxic lymphocytes that can kill neoplastic cells without prior sensitization. A key anti-tumor function of human NK cells is antibody-dependent cell-mediated cytotoxicity (ADCC), mediated exclusively by the IgG Fcy (FcyR) receptor CD16A. The mechanism of action of several clinically successful antitumor therapeutic monoclonal antibodies (mAbs) involves ADCC; however, their therapeutic efficacy is reduced due to regulatory checkpoints of CD16A, which include its low IgG binding affinity and rapid downregulation upon NK cell activation by the membrane metalloprotease ADAM17.1–3 CD64, the highest affinity FcyR, is expressed on myeloid-derived cells and not lymphocytes and is also not cleaved by ADAM17. To enhance ADCC, we generated CD64/16A, a novel recombinant FcyR consisting of extracellular CD64 and intracellular and transmembrane CD16A to mediate high affinity IgG binding and potent cell signaling.4 5

Methods

Engineered NK cells expressing CD64/16A were derived from human induced pluripotent stem-cells (iPSCs), referred to here as iNKs, which are clonal and clinically scalable NK cells. ADCC and natural cytotoxicity of three ovarian cancer cell lines were measured in vitro using Delfia EuTDA and IncuCyte cytotoxicity assays, and production of anti-tumor cytokines was determined via flow cytometry. Finally, tumor cell killing was assessed in vivo using a human xenograft mouse model of peritoneal metastatic ovarian cancer.

Results

Our data show that iNK-CD64/16A cells uniquely facilitate mAb absorption, robustly produce IFN-y and TNF-alpha, and kill several ovarian cancer cell lines in the presence of the therapeutic mAbs trastuzumab or cetuximab, which target HER2 or EGFR, respectively. We found that iNK-CD64/16A cells can capture soluble mAbs and retain antibody arming and ADCC efficacy after cryopreservation. Additionally, iNK-CD64/16A cells robustly mediate ADCC and reduce overall tumor burden of HER2+ tumor cells in vivo in the described metastatic ovarian cancer xenograft model.

Conclusions

Our findings provide new insights into using high affinity Fc receptor-based adoptive NK cell therapies and lay the preclinical foundation necessary for developing an ‘off-the-shelf’ cellular therapy that can be combined with therapeutic tumor-targeting mAbs for the treatment of ovarian cancer. Importantly, iNK-CD64/16A cells can serve as a docking platform for therapeutic antibodies that can be switched and mixed for universal tumor antigen targeting to treat multiple malignancies.

Acknowledgements

Grant support

NIH R01CA203348, HHMI Medical Research Fellows Program/Burroughs Wellcome Fund

References

Jing Y, Ni Z, Wu J, et al. Identification of an ADAM17 cleavage region in human CD16 (FcgammaRIII) and the engineering of a non-cleavable version of the receptor in NK cells. PLoS One 2015;10(3):e0121788.

Wu J, Mishra HK, Walcheck B. Role of ADAM17 as a regulatory checkpoint of CD16A in NK cells and as a potential target for cancer immunotherapy. J Leukoc Biol 2019;105(6):1297–303.

Dixon KJ, Wu J, Walcheck B. Engineering Anti-Tumor Monoclonal Antibodies and Fc Receptors to Enhance ADCC by Human NK Cells. Cancers (Basel) 2021;13(2).

Snyder KM, Hullsiek R, Mishra HK, et al. Expression of a Recombinant High Affinity IgG Fc Receptor by Engineered NK Cells as a Docking Platform for Therapeutic mAbs to Target Cancer Cells. Front Immunol 2018;9:2873.

Walcheck B, Wu J. iNK-CD64/16A cells: a promising approach for ADCC? Expert Opin Biol Ther 2019;19(12):1229–32.

Ethics Approval

This study was approved by the University of Minnesota’s Institutional Animal Care and Use Committee, protocol number 1902–36768A.

169 Off-the-shelf, engineered iPSC-derived NK cells mediate potent cytotoxic activity against primary glioblastoma cells and promote durable long-term survival in vivo

Background

Glioblastoma multiforme (GBM) is a primary brain tumor with a high mortality rate and median survival of ~14 months. Although progress has been made in the development of available therapies, the treatment of GBM remains palliative.1 Emerging results from preclinical studies support the concept that GBM cells may be highly susceptible to natural killer (NK) cell cytotoxicity.2 3 However, sourcing donor-derived NK cells for adoptive cell therapy is limited by cell number and quality. To overcome these barriers, we developed a robust manufacturing system for the generation of high-quality off-the-shelf NK cells derived from induced pluripotent stem cells (iPSCs).4

Methods

We generated triple gene-edited iPSCs designed for mass production of NK cells expressing a high affinity, non-cleavable version of the Fc receptor CD16a and a membrane-bound IL-15/IL-15R fusion protein along with knockout of the nicotinamide adenine dinucleotide (NAD+) hydrolase CD38. NK cells derived from these uniformly engineered iPSCs, termed iADAPT NK cells, displayed enhanced metabolic fitness, resistance to oxidative stress, broad natural cytotoxicity, and robust antibody-dependent cellular cytotoxicity (ADCC). To assess the cytotoxic capacity of iADAPT NK cells, we performed 3-dimensional (3-D) live imaging assays where iADAPT NK cell infiltration and cytotoxicity in response to 9 different primary, patient derived GBM spheroids was measured in real time over the course of 5 days. The in vivo persistence and antitumor function of iADAPT NK cells were also assessed using xenogeneic adoptive transfer models.

Results

In 3-D live imaging assays, iADAPT NK cell efficiently infiltrated and eliminated patient-derived GBM spheroids (figure 1A, B). These in vitro results were recapitulated in vivo in xenogeneic experiments where human GBM cells were implanted intracranially into immunodeficient mice (n=19) followed by adoptive transfer of either 1.5x106 or 3x106 iADAPT NK cells. We show that adoptive transfer of iADAPT NK cells promoted survival in a dose-dependent manner (figure 1C). Importantly, we also found that iADAPT NK cells persisted at high levels in the brain for at least 21 days in the absence of exogenous cytokine support (figure 1D).

Abstract 169 Figure 1

Conclusions

Triple gene-edited iPSCs can be used to robustly manufacture iADAPT NK cells. These off-the-shelf engineered NK cells exhibit potent cytotoxicity against primary, patient derived GBM cells. Work is in progress to further engineer iADAPT NK cells with chimeric antigen receptors incorporating defined targeting motifs to further enhance cytotoxicity against GBM cells. Our preclinical data provides proof-of-concept for a planned phase I clinical trial.

References

Jin J, Grigore F, Chen CC, Li M. Self-renewal signaling pathways and differentiation therapies of glioblastoma stem cells (Review). Int J Oncol 2021;59:45.

Castriconi R, Daga A, Dondero A, Zona G, Luigi Poliani P, Melotti A, Griffero F, Marubbi D, Spaziante R, Bellora F, et al. NK cells recognize and kill human glioblastoma cells with stem cell-like properties. J Immunol 2009;182:3530–3539.

Shiam H, Shanley M, Basar R, Daher M, Gumin J, Zamler DB, Uprety N, Wang F, Huang Y, Gabrusiewicz K, et al. Targeting the αv integrin/TGF-β axis improves natural killer cell function against glioblastoma cells. J Clin Invest 2021;131:e142116.

Cichocki F, Bjordahl R, Gaidarova S, Mahmood S, Abujarour R, Wang H, Tuininga K, Felices M, Davis ZB, Bendzick L, et al. iPSC-derived NK cells maintain high cytotoxicity and enhance in vivo tumor control in concert with T cells and anti-PD-1 therapy. Sci Transl Med 2020;12:eaaz5618.

Ethics Approval

This project has been approved by the University of Minnesota IACUC. Approval ID: 1812-36595A

Abstract 1591: FT536: Preclinical development of a novel off-the-shelf CAR-MICA/B NK cell immunotherapy combined with radiation and antibody treatments as a first-of-kind pan-cancer targeting strategy

Cancer immunotherapies have revolutionized cancer treatment by showing clinical efficacy across multiple cancer indications. However, tumor heterogeneity and evasion from host immune cell surveillance often limit the durability and efficacy of these strategies as monotherapies. Consequently, it is becoming common practice to combine existing anticancer treatments and novel immunotherapies to maximize clinical efficacy. The pan tumor-associated antigens MICA and MICB (MICA/B) are surface proteins induced by cellular stress, often associated with tumorigenesis, and are recognized by the NK cell activating receptor NKG2D. To evade immune recognition, cancer cells often proteolytically shed the membrane distal domains of MICA/B, leading to reduced NKG2D recognition. To combat this pervasive tumor escape mechanism and create a ubiquitous cancer targeting platform, we have developed a novel CAR-iPSC-derived NK (iNK) cell that targets the conserved α3 domain of MICA/B, rendering it resistant to inhibition by shed MICA/B. To enhance effector cell function, persistence and multi-antigen capacity, further genetic editing at the iPSC stage was conducted to equip the CAR-iNK cells with a unique IL-15/IL-15 receptor fusion, the knockout of CD38 and a novel high-affinity, non-cleavable CD16 (hnCD16) to enhance antibody-dependent cellular cytotoxicity (ADCC). In this study, we evaluated the function of multiplexed engineered MICA/B CAR iNK cells (termed FT536) in combination with monoclonal antibodies (mAbs), to elicit multi-antigen targeting, and radiation therapy, to augment surface MICA/B expression. FT536 showed superior in vitro cytotoxicity and in vivo tumor control against an array of MICA/B expressing tumor lines. Furthermore, ADCC, induced in combination with cetuximab or trastuzumab, enhanced the potency of FT536 against various solid tumor lines (p <0.05). To demonstrate the capability of FT536 to synergize with irradiation therapy, we utilized a panel of tumor lines, divergent in tissue origin and MICA/B expression profiles. This approach highlighted that irradiation of the SK-BR-3 tumor line, a breast adenocarcinoma that expresses low levels of surface MICA/B and high levels of EGFR, induced the upregulation of MICA/B expression (p <0.05). As anticipated, FT536 exhibited enhanced, CAR-dependent cytotoxicity against irradiated SK-BR-3 cells. Ongoing work is focused on the development of in vivo models that combine FT536 with in situ tumor irradiation and mAbs in order to promote durable responses and the elimination of resistant and heterogenous cancer cells. These data demonstrate successful targeting of MICA/B positive tumors by FT536 can be augmented by mAb and radiation therapies as first-of-kind combinatorial strategies to broadly target escape-prone tumors.

Citation Format: John Goulding, Robert Blum, Bryan Hancock, Moyar Ge, Brian Groff, Soheila Shirinbak, Joy Grant, Martin Hosking, Mochtar Pribadi, Yijia Pan, Hui-Yi Chui, Shohreh Sikaroodi, Lauren Fong, Janel Huffman, Wen-I Yeh, Chia-Wei Chang, Thomas Dailey, Miguel Meza, Cokey Nguyen, Lucas Ferrari de Andrade, Tom Lee, Ryan Bjordahl, Kai W. Wucherpfennig, Bahram Valamehr. FT536: Preclinical development of a novel off-the-shelf CAR-MICA/B NK cell immunotherapy combined with radiation and antibody treatments as a first-of-kind pan-cancer targeting strategy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1591.

Abstract 1539: Development of off-the-shelf B7H3 chimeric antigen receptor NK cell therapeutic with broad applicability across many solid tumors

Although chimeric antigen receptor (CAR) T cell therapies have demonstrated impressive efficacy in a number of hematological malignancies, successful application of CAR T cells in solid tumor indications has been challenging due to difficulty identifying and targeting suitable tumor associated antigens (TAA) without eliciting significant on-target, off-tumor toxicity. Furthermore, the challenges of tumor heterogeneity and antigen escape need to be addressed when treating bulky solid tumors. Successful development of CAR-targeted cellular therapies for solid tumor indications will consequently require careful selection of target antigen, effector cell, and cell engineering to balance on-tumor efficacy with potential for off-tumor toxicities. In contrast to CAR-T cell therapies, adoptive natural killer (NK) cell immunotherapies have been well tolerated, but conventional, donor-derived strategies have had limited efficacy.

B7H3 is an immune checkpoint molecule of the B7 protein superfamily and an ideal TAA; B7H3 has broad expression in cancer and limited expression on healthy tissues. Clinically, upregulation of B7H3 is often associated with metastatic cancer and poor patient prognosis. To target B7H3 with a multifaceted effector cell population, we selected the use of NK cells to leverage their clinical safety profile and versatile innate tumor recognition and cytotoxicity features. Here we describe the optimization and characterization of a novel anti-B7H3 CAR and its application in an induced pluripotent stem cell-derived, off-the-shelf NK (iNK) cell immunotherapy. These anti-B7H3 CAR iNK cells utilize multiplexed genetic engineering to enhance persistence, effector function, and to enable multi-antigen targeting through combinations with monoclonal antibody therapy.

Using a novel B7H3 binding domain, CAR constructs were first screened in primary T cells for the optimal spacer length by in vitro and in vivo cytotoxicity assays. Following optimized CAR selection, in vitro proof of concept studies demonstrated broad B7H3 CAR reactivity against an array of tumor cell line targets of both hematologic and solid organ cancers. B7H3 CAR-T cells were highly reactive against cell lines derived from ovarian, prostate, bone, and breast cancers as demonstrated by cytotoxicity and production of IFNγ and TNFα. iNK cells carrying the optimized CAR design were evaluated in vitro for B7H3 specificity using cytotoxicity assays and intracellular cytokine staining. In addition, B7H3 CAR iNK cells synergized with anti-EGFR and anti-HER2 monoclonal antibodies to produce antibody-dependent cellular cytotoxicity, leading to further enhancement of tumor targeting. In summary, these data demonstrate successful targeting of B7H3 using an off-the-shelf, engineered NK cell platform for the effective elimination of multiple tumor types.

Citation Format: Ryan Bjordahl, John Goulding, Hui-Yi Chu, Frank Cichocki, Nicholas Zorko, Zachary Davis, Martin Felices, Alex Garcia, Svetlana Gaidarova, Wen-I Yeh, Tom T. Lee, Jeffrey S. Miller, Bahram Valamehr. Development of off-the-shelf B7H3 chimeric antigen receptor NK cell therapeutic with broad applicability across many solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1539.

Abstract 1550: FT576 path to first-of-kind clinical trial: translation of a versatile multi-antigen specific off-the-shelf NK cell for treatment of multiple myeloma

Chimeric antigen receptor (CAR) directed therapies have been used successfully to treat a variety of hematological malignancies. With the advent of multi-modal engineering, adoptive cell therapy offers the opportunity to tackle increasingly complex disease settings such as multiple myeloma (MM), where targeting of single tumor associated antigen by CAR or monoclonal antibodies (mAb) is confounded by antigen loss and clonal heterogeneity. Further, expanding treatment options beyond primary T and NK cell based therapies has multiple advantages, including the use of induced pluripotent stem cells (iPSC) to derive effector cells using precision genetic engineering that can be uniformly manufactured at scale from a clonally-derived master cell bank (MCB).FT576 is a multiplex-edited, iPSC-derived CAR-NK (CAR-iNK) cell therapy designed for treatment of Multiple Myeloma. FT576 is engineered 1) to express a recombinant IL-15/IL-15 receptor signaling complex (IL-15RF) for enhanced persistence; 2) to express an enhanced high-affinity, non-cleavable CD16 (hnCD16) ; 3) to disrupt expression of CD38, allowing for enhanced ADCC without NK cell fratricide; and 4) to express a BCMA-targeted CAR with NK-cell optimized signaling.CAR-directed specificity of the FT576 cells for BCMA was demonstrated using a short-term cytotoxicity assay (90.8% cytotoxicity against BCMA+ vs 22.1% BCMA- cells, p<0.0001). Utilizing a long-range tumor clearance assay without exogenous cytokine support, serial restimulation by repeated rounds of exposure to fresh MM target cells showed remarkable persistence and antigen-mediated expansion of FT576 by CAR alone or combined with anti-CD38 mAb. Continuous long-range clearance assays demonstrated levels of BCMA targeting activity of FT576 alone was equivalent to primary BCMA-targeted CAR-T cells against a panel of BCMA+ target cells. BCMA-CAR targeting was tested in combination with multiple therapeutic mAbs to explore breadth of tumor clearance in primary bone marrow samples.In xenograft models, dosing of FT576 as a monotherapy was highly protective against MM progression, resulting in deeper tumor regression and delayed outgrowth. The treatment of MM-bearing mice with both FT576 and daratumumab produced greater myeloma control than either agent alone, demonstrating combined CAR and antibody-directed cytotoxicity. Additionally, FT576 demonstrated enhanced persistence compared to peripheral blood NK cells, suggestive of antigen mediated expansion. Together, these studies demonstrate the versatility of FT576 as a highly effective multi-antigen targeting and cost-effective, off-the-shelf BCMA-CAR iNK cell product and support the rational for a first-of-kind Phase I Study of FT576 as a monotherapy or in combination with therapeutic mAbs targeted to MM-associated surface antigens.

Citation Format: Jode P. Goodridge, Ryan Bjordahl, Sajid Mahmood, John Reiser, Svetlana Gaidarova, Robert Blum, Frank Cichocki, Hui-yi Chu, Greg Bonello, Tom Lee, Brian Groff, Miguel Meza, Thomas Daley, Yu-waye Chu, Bruce Walcheck, Karl-Johan Malmberg, Jeffrey S. Miller, Armin Rehm, Bahram Valamehr. FT576 path to first-of-kind clinical trial: translation of a versatile multi-antigen specific off-the-shelf NK cell for treatment of multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1550.

iPSC-derived NK cells maintain high cytotoxicity and enhance in vivo tumor control in concert with T cells and anti-PD-1 therapy

The development of immunotherapeutic monoclonal antibodies targeting checkpoint inhibitory receptors, such as programmed cell death 1 (PD-1), or their ligands, such as PD-L1, has transformed the oncology landscape. However, durable tumor regression is limited to a minority of patients. Therefore, combining immunotherapies with those targeting checkpoint inhibitory receptors is a promising strategy to bolster antitumor responses and improve response rates. Natural killer (NK) cells have the potential to augment checkpoint inhibition therapies, such as PD-L1/PD-1 blockade, because NK cells mediate both direct tumor lysis and T cell activation and recruitment. However, sourcing donor-derived NK cells for adoptive cell therapy has been limited by both cell number and quality. Thus, we developed a robust and efficient manufacturing system for the differentiation and expansion of high-quality NK cells derived from induced pluripotent stem cells (iPSCs). iPSC-derived NK (iNK) cells produced inflammatory cytokines and exerted strong cytotoxicity against an array of hematologic and solid tumors. Furthermore, we showed that iNK cells recruit T cells and cooperate with T cells and anti-PD-1 antibody, further enhancing inflammatory cytokine production and tumor lysis. Because the iNK cell derivation process uses a renewable starting material and enables the manufacturing of large numbers of doses from a single manufacture, iNK cells represent an "off-the-shelf" source of cells for immunotherapy with the capacity to target tumors and engage the adaptive arm of the immune system to make a "cold" tumor "hot" by promoting the influx of activated T cells to augment checkpoint inhibitor therapies.

Abstract 2216: Combinational strategy targeting B cell malignancy using iPSC engineered CAR-NK (FT596) and CAR-T cell (FT819) platforms with therapeutic antibody to achieve an effective deep and durable response

The use of induced pluripotent stem cells (iPSCs) to derive immune effector cells offers distinct advantages for immune therapy over existing patient- or donor- derived platforms, not only in terms of scalable manufacturing and precision genetic engineering at the clonal level, but also in allowing the generation and combinational use of multiple effector cell types each with distinct characteristics. Taking cues from the natural propagation of innate to adaptive effector responses, here we describe the combined use of multi-engineered iPSC derived Natural Killer (iNK) and T (iT) cell platforms in order to exploit the unique properties of each cell type to achieve both depth and durability of response for hematological malignancies. As innate cells, NK cells are characterized by the capacity for spontaneous reactivity, either in response to cell surface antigen or downregulation of class I MHC, and the rapid kinetic under which NK cells operate make them an ideal candidate to achieve a depth of response that outpaces the limiting effects of cytokine support. FT596 was developed as a dual-targeted iNK cell platform engineered to express both a CD19-directed, NK cell-optimized (NKG2D-2B4-CD3ζ) chimeric antigen receptor (CAR) and a high-affinity, non-cleavable Fc receptor (hnCD16), enabling multi-targeting through combination with therapeutic antibodies. The activity of each receptor is further enhanced by the expression of an IL15-IL15Ra fusion receptor, which also allows the cells to expand in the absence of exogenous cytokine support and prolongs cell survival in vitro and in vivo. T cells are exquisitely specific and undergo rapid clonal expansion and differentiation in response to target antigen, and antigen driven persistence has been demonstrated as a key determinant in efficacy in primary CAR-T cell immune therapy. FT819 is an iT cell platform engineered to express a functionally optimized CD19-CAR (1XX) that has been genome edited into the T cell receptor (TCR) alpha constant (TRAC) locus to provide ideal CAR activity and to prevent TCR expression, thereby avoiding the complications of GVH reactivity in an allogeneic setting. In vivo, both FT596 and FT819 showed stable levels of tumor cell clearance against the CD19+ acute lymphoblastic leukemia cell line NALM6, comparable to that of primary CAR19 T cells (p*<0.0001 for FT596, FT819 or Primary CART vs NALM6 alone). FT596 also shows enhanced clearance of CD19+CD20+ Burkitts lymphoma cell line RAJI when used in combination with rituximab (p=0.0002 vs rituximab alone). Collectively, these studies suggest a compounded anti-tumor effect can be achieved utilizing the inherent properties of engineered CAR-iNK cells together with therapeutic antibody combined with engineered CAR-iT cells which will be highlighted in this presentation.

Citation Format: Jode P. Goodridge, John W. Reiser, Ryan Bjordahl, Milli Mandal, Chia-wei Chang, Raedun Clarck, Sajid Mahmood, Huang Zhu, Svetlana Gaidarova, Robert Blum, Frank Cichocki, Hui-ting Hsu, Greg Bonello, Tom Lee, Brian Groff, Karl-Johan Mamlberg, Bruce Walcheck, Jeffrey S. Miller, Dan Kaufman, Bahram Valamehr. Combinational strategy targeting B cell malignancy using iPSC engineered CAR-NK (FT596) and CAR-T cell (FT819) platforms with therapeutic antibody to achieve an effective deep and durable response [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2216.

Pluripotent stem cell-derived NK cells with high-affinity noncleavable CD16a mediate improved antitumor activity

Antibody-dependent cellular cytotoxicity (ADCC) is a key effector mechanism of natural killer (NK) cells that is mediated by therapeutic monoclonal antibodies (mAbs). This process is facilitated by the Fc receptor CD16a on human NK cells. CD16a appears to be the only activating receptor on NK cells that is cleaved by the metalloprotease a disintegrin and metalloproteinase-17 upon stimulation. We previously demonstrated that a point mutation of CD16a prevents this activation-induced surface cleavage. This noncleavable CD16a variant is now further modified to include the high-affinity noncleavable variant of CD16a (hnCD16) and was engineered into human induced pluripotent stem cells (iPSCs) to create a renewable source for human induced pluripotent stem cell-derived NK (hnCD16-iNK) cells. Compared with unmodified iNK cells and peripheral blood-derived NK (PB-NK) cells, hnCD16-iNK cells proved to be highly resistant to activation-induced cleavage of CD16a. We found that hnCD16-iNK cells were functionally mature and exhibited enhanced ADCC against multiple tumor targets. In vivo xenograft studies using a human B-cell lymphoma demonstrated that treatment with hnCD16-iNK cells and anti-CD20 mAb led to significantly improved regression of B-cell lymphoma compared with treatment utilizing anti-CD20 mAb with PB-NK cells or unmodified iNK cells. hnCD16-iNK cells, combined with anti-HER2 mAb, also mediated improved survival in an ovarian cancer xenograft model. Together, these findings show that hnCD16-iNK cells combined with mAbs are highly effective against hematologic malignancies and solid tumors that are typically resistant to NK cell-mediated killing, demonstrating the feasibility of producing a standardized off-the-shelf engineered NK cell therapy with improved ADCC properties to treat malignancies that are otherwise refractory.

Abstract 3191: FT516, an off-the-shelf engineered NK cell therapeutic product for universal anti-tumor targeting strategy in combination with monoclonal antibodies

Monoclonal antibody (mAb) treatment is an effective therapeutic strategy for many cancer types, with significant opportunity to optimize natural killer (NK) cell and mAb interaction to improve antibody-dependent cellular cytotoxicity (ADCC). NK cells are critical mediators of ADCC, where they recognize and kill malignant cells coated with antibody through the Fc receptor CD16. However, NK cell function is often impaired in cancer patients, which limits the induction of ADCC in mAb therapy. To enhance ADCC in combination with commercialized mAb therapies, we have developed FT516; a novel, off-the-shelf NK cell immunotherapeutic engineered to uniformly express a high-affinity, non-cleavable version of CD16 (hnCD16).

FT516 is manufactured from a renewable master induced pluripotent stem cell (iPSC) line with the potential to generate hundreds to thousands of doses of allogeneic NK cells uniformly expressing hnCD16 (hnCD16 iNK cells) per manufacturing run. In an in vivo xenograft model of disseminated lymphoma, FT516 reduced tumor burden below the limit of detection at day 28 after transplant when delivered in combination with rituximab, which was significantly more potent than peripheral blood NK cells (p = 0.03). This was attributed to enhanced CD16-mediated activation of FT516, as observed through improved calcium flux and enhanced activation of signaling pathways such as ERK (p = 0.016), LAT (p = 0.0007), and ZAP70 (p = 0.0003), leading to enhanced ADCC and cytokine production. FT516 also maintained tumor cell specificity, with preferential targeting of K562 leukemia cells when presented with a mixture of K562 and normal PBMC targets (p < 0.0001).

We also explored strategies to further engineer therapeutic function to enhance FT516 efficacy. Combined expression of hnCD16 with an IL-15/IL-15ra fusion construct enhanced the persistence of iNK cells and allowed survival of up to 8 weeks in vivo without exogenous cytokine (p < 0.0001), with correlation to improved efficacy.

In vitro modeling of FT516 with daratumumab demonstrated ADCC against multiple myeloma (MM) targets. However, as reported, daratumumab induced NK cell fratricide through binding of CD38 on NK cells. To rescue daratumumab-mediated fratricide, we specifically deleted CD38 at the iPSC level and demonstrated that fratricide was undetectable in hnCD16 CD38-/- iNK cells (<1% vs. 35% for peripheral blood NK). By avoiding fratricide, hnCD16 CD38-/- iNK cells had improved persistence and efficacy against MM cells in vitro and in a disseminated xenograft model of MM. These data support clinical development of FT516 in combination with rituximab for the treatment of B cell malignancies and demonstrate a targeting platform that enables further modifications to address challenges related to efficacy, safety, and persistence of allogeneic adoptive immunotherapies.

Citation Format: Ryan Bjordahl, Huang Zhu, Paul Rogers, Svetlana Gaidarova, Moyar Q. Ge, Robert Blum, Frank Cichocki, Jode Goodridge, Helen Chu, Greg Bonello, Tom Lee, Brian Groff, Ramzey Abujarour, Bruce Walcheck, Jeffrey Miller, Dan Kaufman, Bahram Valamehr. FT516, an off-the-shelf engineered NK cell therapeutic product for universal anti-tumor targeting strategy in combination with monoclonal antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3191.

Abstract 3207: Preclinical development of first-of-kind dual-targeted off-the-shelf CAR-NK cell product with engineered persistence for an effective treatment of B cell malignancies

The unprecedented success of chimeric antigen receptor (CAR) and monoclonal antibody (mAb) -based immune-therapies has provided a clear indication that a system as complex as human immunity can be harnessed, even enhanced, toward a growing number of hematological cancers. Here we describe pre-clinical progress to develop a multi-functional induced pluripotent stem cell (iPSC)-derived natural killer (iNK) cell platform that combines engineered longevity with CAR and mAb-based modalities to leverage the intrinsic polyfunctionality of NK cells. As frontrunners of immune surveillance, NK cells employ a diverse array of germline encoded receptors in distinct combinations, which engage multiple signaling pathways to deliver potent effector responses that can be directed toward tumor cells, drive rapid proliferation, and pave the way for recruitment of adaptive immunity. Specific engagement of multiple signaling pathways was achieved in iNK cells through design of an NK cell-centric CAR combining the transmembrane domain of activating receptor NKG2D with intracellular signaling domains of 2B4 and CD3ζ. Recombining an anti-CD19 scFv onto this signaling platform, CAR modified iNK cells produced specific in vitro recognition of CD19+ B cell lymphoma cells in short term and long term cytotoxicity assays (84% vs 40% clearance of tumor cells at 60H, p<0.001). Further introduction of a fusion receptor consisting of Interleukin-15 (IL15) with IL15 receptor α, enabling autonomous IL15 stimulation, greatly improved iNK longevity and functional persistence in animal models. Moreover, iNK cells modified with IL15 fusion receptor showed enhanced functional maturation including KIR expression and effector molecules such as granzyme B ( ≥2 fold). While iNK cells with anti-CD19 CAR delayed tumor progression in vivo prior to relapse, iNK cells engineered with anti-CD19 CAR and IL15/IL15 receptor were curative against B cell lymphoma, (p<0.002). Expression of CAR and IL15 fusion receptor was then combined with a third modality, a high affinity CD16a receptor modified to prevent proteolytic cleavage (hnCD16). These multifunctional iNK cells demonstrated enhanced directed cytotoxicity in vitro in combination with rituximab against CD19+ targets (>99% vs 90% clearance of tumor cells) and CD19- targets (>99% vs 50% clearance of tumor cells by iNK with anti-CD19 CAR alone, p<0.0001), revealing a unique opportunity to combine CAR with a universal targeting modality to mitigate antigen escape and address heterogeneity in the tumor population by a multi-node targeting strategy. The resulting product, FT519, is designed to provide a flexible, potent and persistent engineered immune cell that utilizes the intrinsic versatility of NK cells to enable a highly effective combination therapy in a single, standardized, scalable, off-the-shelf platform.

Citation Format: Jode Goodridge, Sajid Mahmood, Huang Zhu, Svetlana Gaidarova, Robert Blum, Ryan Bjordahl, Frank Cichocki, Hui-Yi Chu, Greg Bonello, Tom Lee, Brian Groff, Karl-Johan Malmberg, Bruce Walcheck, Jeffrey Miller, Dan Kaufman, Bahram Valamehr. Preclinical development of first-of-kind dual-targeted off-the-shelf CAR-NK cell product with engineered persistence for an effective treatment of B cell malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3207.

GSK3 Inhibition Drives Maturation of NK Cells and Enhances Their Antitumor Activity

Maturation of human natural killer (NK) cells as defined by accumulation of cell-surface expression of CD57 is associated with increased cytotoxic character and TNF and IFNγ production upon target-cell recognition. Notably, multiple studies point to a unique role for CD57⁺ NK cells in cancer immunosurveillance, yet there is scant information about how they mature. In this study, we show that pharmacologic inhibition of GSK3 kinase in peripheral blood NK cells expanded ex vivo with IL15 greatly enhances CD57 upregulation and late-stage maturation. GSK3 inhibition elevated the expression of several transcription factors associated with late-stage NK-cell maturation including T-BET, ZEB2, and BLIMP-1 without affecting viability or proliferation. When exposed to human cancer cells, NK cell expanded ex vivo in the presence of a GSK3 inhibitor exhibited significantly higher production of TNF and IFNγ, elevated natural cytotoxicity, and increased antibody-dependent cellular cytotoxicity. In an established mouse xenograft model of ovarian cancer, adoptive transfer of NK cells conditioned in the same way also displayed more robust and durable tumor control. Our findings show how GSK3 kinase inhibition can greatly enhance the mature character of NK cells most desired for effective cancer immunotherapy. Cancer Res; 77(20); 5664-75. ©2017 AACR.

Abstract 3752: FATE-NK100: A novel NK cell-mediated cancer therapy

Natural killer (NK) cells are innate lymphoid cells that mediate immune responses against pathogens and cancer. Human NK cells are distinguished by the surface phenotype CD3-CD56+, and maturation of CD56dim NK cells is associated with acquisition of CD57. Rather than being an immunosenescence marker, CD57 acquisition represents a shift toward greater effector function, including increased CD16 signaling (Fc receptor responsible for triggering antibody-dependent cellular cytotoxicity), more potent cytotoxicity and enhanced inflammatory cytokine production after target cell engagement.

The main challenge in enriching for CD57+ NK cells using current ex vivo expansion protocols is that interleukin (IL)-15, the cytokine that drives NK cell proliferation and is critical for NK cell survival, preferentially expands less mature NK subsets that fail to terminally differentiate in culture. Our group has developed a novel NK cell expansion method that overcomes this barrier. Peripheral blood mononuclear cells from are depleted of CD3+ T cells and CD19+ B cells and cultured for 7 days with IL-15 and a small molecule inhibitor of glycogen synthase kinase 3-beta (GSK3β), a multifunctional kinase downstream of the PI(3)K pathway. Compared to vehicle control, addition of the GSK3β inhibitor led to a substantial increase (2.2-fold ± 0.19, n=23, p<0.0001) in the CD57+ NK cell population, and total CD3-CD56+ NK cells were highly enriched (90.9% ± 2.2) relative to pre-culture CD3/CD19 depletion (23.3% ± 2.5) (p<0.0001). We used a high-resolution imaging approach to analyze in vitro NK cell-mediated killing of the ovarian tumor cell line SKOV-3 and the lung carcinoma line A549. We demonstrate that NK cells from CD3/CD19-depleted peripheral blood products cultured for 7 days with the GSK3β inhibitor exhibit significantly more rapid killing kinetics and overall tumor killing relative to NK cells cultured for 7 days with IL-15 and the vehicle control. Superior tumor control of NK cells cultured with IL-15 and the GSK3β inhibitor was also observed against SKOV-3 tumor cells in a murine xenogeneic adoptive transfer model that included IL-2 injections.

We have scaled our process to manufacture a GMP product (referred to as FATE-NK100) for clinical use. Using an apheresis product from a donor containing 21.5 x 108 CD57+ NK cells, we achieved 6.4-fold NK cell expansion resulting in a final GMP-grade product containing 158 x 108 CD57+ NK cells. The cytotoxicity of these ex vivo expanded NK cells in response to SKOV-3 cells is superior to that of CD3/CD19-depleted haploidentical NK cells activated overnight with either IL-2 or IL-15 (representing the NK products used in current clinical trials). These data have been presented to the FDA in preparation for a clinical trial of FATE-NK100 in lymphodepleted patients with advanced AML anticipated for Q1 2017.

Citation Format: Frank Cichocki, Barham Valamehr, Ryan Bjordahl, Bin Zhang, Dhifaf Sarhan, Sarah Cooley, Bruce Blazar, Betsy Rezner, Paul Rogers, Chad Green, Stewart Abbot, Daniel Shoemaker, Scott Wolchko, Jeffrey S. Miller. FATE-NK100: A novel NK cell-mediated cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3752. doi:10.1158/1538-7445.AM2017-3752

Abstract 3755: Renewable and genetically engineered natural killer cells for off-the-shelf adoptive cellular immunotherapy

The unique attributes of a combinatorial tumor recognition system, diminished off-tumor cytotoxicity, and multifaceted effector function make natural killer (NK) cells a prime candidate for a universal approach to cancer immunotherapy. In addition, NK cells are the principal mediator of antibody-directed cellular cytotoxicity (ADCC). However, NK cell function is often impaired in the setting of cancer, reducing the effectiveness of the endogenous immune system and the therapeutic efficacy of monoclonal antibodies. To address the need for advanced and combinatorial cancer therapies, we developed a unique and effective strategy to create a renewable source of engineered “off-the-shelf” NK cells with augmented function, including enhanced ADCC and persistence. Key challenges associated with genetic editing, limited expansion, persistence and variability of peripheral blood (PB)-derived NK cells were overcome by utilizing our induced pluripotent stem cell (iPSC) technology as the unlimited starting material for the reproducible and consistent derivation of engineered NK cells. Through targeted transgene integration, we produced a clonal iPSC master cell line to continuously produce NK cells engineered to uniformly express a high affinity, non-cleavable version of CD16 (hnCD16-NK). In directed differentiation, the hnCD16-NK cells displayed homogeneous expression of CD16 (>95%) and a mature CD56+ NK cell phenotype, as exhibited by expression of KIR, NCRs, DNAM-1, and NKG2D. In contrast to endogenous CD16 expression, the engineered hnCD16 molecule was shown to be cleavage resistant upon NK cell activation (>95% CD16+ hnCD16-NK vs. <10% CD16+ PB-derived NK cell, upon target cell-mediated activation), and demonstrated enhanced antibody binding compared to PB-derived NK cells expressing the low-affinity variant. In addition to increased expression of the cytolytic molecules perforin and granzyme B and enhanced direct cytotoxicity against tumor targets, hnCD16-NK cells displayed superior ADCC capacity and cytokine production in response to CD16 stimulation. Importantly, manufacture of hnCD16-NK cells was proven to be highly scalable, delivering up to 107 fold expansion over a 35 day period. The maintained proliferative capacity can be in part associated with longer telomere length seen in hnCD16-NK cells. Furthermore, deletion of classical human leukocyte antigen molecules and ectopic expression of immunosuppressive proteins engineered at the iPSC level provided the ability of hnCD16-NK cells to potentially overcome the host histocompatibility barrier and to improve persistence in the allogeneic setting. In conclusion, the preclinical data presented herein highlight the therapeutic value of hnCD16-iNK cells as an ideal ADCC-mediated “off-the-shelf” NK cell-based immunotherapeutic product with augmented persistence, anti-tumor capacity, manufacturing reliability and preclinical efficacy.

Citation Format: Ryan Bjordahl, Frank Cichocki, Raedun Clarke, Svetlana Gaidarova, Brian Groff, Paul Rogers, Stacey Moreno, Ramzey Abujarour, Greg Bonello, Tom Lee, Weijie Lan, Matthieu Bauer, Dave Robbins, Betsy Rezner, Sarah Cooley, Bruce Walcheck, Stewart Abbot, Bruce Blazar, Scott Wolchko, Daniel Shoemaker, Jeffrey S. Miller, Bahram Valamehr. Renewable and genetically engineered natural killer cells for off-the-shelf adoptive cellular immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3755. doi:10.1158/1538-7445.AM2017-3755

Abstract 609: Overcoming host histocompatibility barrier to create a renewable source of off-the-shelf effector lymphocytes for adoptive immunotherapy

Encouraging clinical outcomes in autologous cellular immunotherapy have garnered hope and excitement. However, limitations of patient-derived cancer immunotherapies remain to be addressed to deliver reliable and efficacious therapies with broader applicability. Induced pluripotent stem cells (iPSCs) are a unique, renewable source for the continuous generation of cellular therapeutics and represent a highly promising approach for overcoming many of the limitations of autologous therapy. To advance the promise of iPSC technology as an “off-the-shelf” (OTS) source of cellular therapeutics, several considerations need to be addressed. Ensuring the persistence of allogeneic OTS therapies after adoptive cell transfer across histocompatibility barriers is a key requirement. Establishing a master cell line from genetically engineered clonal iPSC lines with the capacity to continuously generate homogenous populations of highly functional effector cells will also be necessary. Here we demonstrate a comprehensive approach for the generation of immune tolerant effector cells derived from a genetically engineered iPSC master cell line. We successfully combined deletion of classical human leukocyte antigen molecules with expression of immunosuppressive proteins to generate clonal iPSC lines with the ability to escape immune rejection. Utilizing in vitro quantitative live cell analysis we show that OTS-iPSCs elicit a significantly decreased cytotoxic response from both peripheral blood (PB)-NK cells (47.9 vs. 91.4% survival at 3:1 E:T ratio) and PB-T cells (>2.7-fold greater number of OTS-iPSC derived cells remaining at 88 hrs). Additionally, mixed lymphocyte reactions employing unfractionated PB mononuclear cells resulted in significantly decreased activation and proliferation of CD8+ T cells (63.4 vs. 29.6%), CD4+ T cells (70.9 vs. 17.3%) and NK cells (46.8 vs. 11.6%). In preclinical mouse models we demonstrate that OTS-iPSCs exhibit improved persistence in vivo. Bilateral engraftments were established in non-conditioned, fully immune-competent recipient mice using luciferized wildtype and OTS-iPSCs. Daily bioluminescence imaging revealed a significant increase in persistence of OTS-iPSCs during the 48-196 hour post injection window (>5.5 fold greater luminescence at 96 hrs). Using our potent chemically-defined stage-specific monolayer hematopoietic differentiation platform, we demonstrate that OTS-iPSC derived CD34 expressing hematopoietic cells are reproducibly scaled and readily give rise to functional lymphocytes carrying the engineered targeted modality in a homogenous manner (95 +/- 5%). The outlined preclinical data illustrate that iPSCs are an ideal renewable source for OTS hematopoietic cell-based immunotherapies and represent a potentially exponential advancement in adoptive immunotherapy.

Citation Format: Raedun L. Clarke, Matthieu Bauer, Ryan Bjordahl, Jeffrey Sasaki, Brian Groff, Svetlana Gaidarova, Tom Tong Lee, Weijie Lan, Michelle Burrascano, Ramzey Abujarour, Greg Bonello, Megan Robinson, Stewart Abbot, Scott Wolchko, Daniel Shoemaker, Bob Valamehr. Overcoming host histocompatibility barrier to create a renewable source of off-the-shelf effector lymphocytes for adoptive immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 609. doi:10.1158/1538-7445.AM2017-609

Cancer Mutations Targeting TNFRSF14 alter Microenvironment Checkpoint Interactions to Limit Tumor Clearance by Cytotoxic Cells

The roles of many non-oncogenic mutations in cancer may influence tumor growth, survival, or how tumors interact with their surroundings. Here we characterize the functional relevance of missense mutations within the gene encoding the tumor necrosis receptor family member HVEM (TNFRSF14), a locus frequently targeted within human lymphoma and other cancers. We find that point mutations identified in human lymphoma were localized to the extracellular domain and specifically target ligand binding, resulting in preferential loss of CD160 and BTLA interactions compared to LIGHT (TNFSF14). Missense mutations were associated with alterations in cytotoxic effector cell signatures within tumor biopsies, while deletion mutations were associated with changes in myeloid cell signatures. Finally, we find that mutated HVEM proteins retained the capacity to inhibit T cell signaling through BTLA, while reducing costimulation of cytolysis in NK cells through CD160. Together, these data provide evidence for how immune selective pressures may drive mutation of TNFRSF14 resulting in greater tumor fitness.

Development of a new mouse/human FoxP3 antibody using rabbit recombinant antibody technology (IRC4P.477)

Tregs play a key role in immune system suppression during autoimmunity and tumor development. Tregs are classified as CD4+CD25+FoxP3+, and exist as either nTregs originating from the thymus, or iTregs derived from CD4+ effector T cells in the periphery. Reduction in Treg numbers leads to autoimmunity; this is clearly shown in scurfy mice where FoxP3 has been deleted, Treg numbers are severely reduced, and mice succumb to autoimmunity early in life. In contrast, Tregs play a debilitating role in cancer biology when the Treg numbers are elevated, and the immune response is dampened allowing cancer cells to evade the immune system. Thus, the correct balance of Tregs is essential for maintaining immune homeostasis. FoxP3 has been widely used as a marker of Tregs, and many antibodies are available on the market that distinguish the Treg population in human or mouse cells. We developed a novel FoxP3 antibody and Fix and Perm buffer system that is comparable to current clones, but recognizes both mouse and human FoxP3 equally well, eliminating the need for separate antibodies. The ms/hu FoxP3 antibody was generated using our Rabbit Recombinant antibody technology, which allows for selecting high specificity, high affinity antibodies, lot to lot consistency and detection of both mouse and human nTregs and iTregs. This allows researchers to extend their mouse models into clinical studies without a change in the antibody clone eliminating a variable and streamlining the process.

Expression of the p60 autolysin enhances NK cell activation and is required for listeria monocytogenes expansion in IFN-gamma-responsive mice

Both peptidoglycan and muropeptides potently modulate inflammatory and innate immune responses. The secreted Listeria monocytogenes p60 autolysin digests peptidoglycan and promotes bacterial infection in vivo. Here, we report that p60 contributes to bacterial subversion of NK cell activation and innate IFN-gamma production. L. monocytogenes deficient for p60 (Deltap60) competed well for expansion in mice doubly deficient for IFNAR1 and IFN-gammaR1 or singly deficient for IFN-gammaR1, but not in wild-type, IFNAR1(-/-), or TLR2(-/-) mice. The restored competitiveness of p60-deficient bacteria suggested a specific role for p60 in bacterial subversion of IFN-gamma-mediated immune responses, since in vivo expansion of three other mutant L. monocytogenes strains (DeltaActA, DeltaNamA, and DeltaPlcB) was not complemented in IFN-gammaR1(-/-) mice. Bacterial expression of p60 was not required to induce socs1, socs3, and il10 expression in infected mouse bone marrow macrophages but did correlate with enhanced production of IL-6, IL-12p70, and most strikingly IFN-gamma. The primary source of p60-dependent innate IFN-gamma was NK cells, whereas bacterial p60 expression did not significantly alter innate IFN-gamma production by T cells. The mechanism for p60-dependent NK cell stimulation was also indirect, given that treatment with purified p60 protein failed to directly activate NK cells for IFN-gamma production. These data suggest that p60 may act on infected cells to indirectly enhance NK cell activation and increase innate IFN-gamma production, which presumably promotes early bacterial expansion through its immunoregulatory effects on bystander cells. Thus, the simultaneous induction of IFN-gamma production and factors that inhibit IFN-gamma signaling may be a common strategy for misdirection of early antibacterial immunity.