Induction of innate lymphoid cell-derived interleukin-22 by the transcription factor STAT3 mediates protection against intestinal infection.

Inhibitors of the transcription factor STAT3 target STAT3-dependent tumorigenesis but patients often develop diarrhea from unknown mechanisms. Here we showed that STAT3 deficiency increased morbidity and mortality after Citrobacter rodentium infection with decreased secretion of cytokines including IL-17 and IL-22 associated with the transcription factor RORγt. Administration of the cytokine IL-22 was sufficient to rescue STAT3-deficient mice from lethal infection. Although STAT3 was required for IL-22 production in both innate and adaptive arms, by using conditional gene-deficient mice, we observed that STAT3 expression in RORγt(+) innate lymphoid cells (ILC3s), but not T cells, was essential for the protection. However, STAT3 was required for RORγt expression in T helper cells, but not in ILC3s. Activated STAT3 could directly bind to the Il22 locus. Thus, cancer therapies that utilize STAT3 inhibitors increase the risk for pathogen-mediated diarrhea through direct suppression of IL-22 from gut ILCs.

STING-Dependent Cytosolic DNA Sensing Promotes Radiation-Induced Type I Interferon-Dependent Antitumor Immunity in Immunogenic Tumors.

Ionizing radiation-mediated tumor regression depends on type I interferon (IFN) and the adaptive immune response, but several pathways control I IFN induction. Here, we demonstrate that adaptor protein STING, but not MyD88, is required for type I IFN-dependent antitumor effects of radiation. In dendritic cells (DCs), STING was required for IFN-? induction in response to irradiated-tumor cells. The cytosolic DNA sensor cyclic GMP-AMP (cGAMP) synthase (cGAS) mediated sensing of irradiated-tumor cells in DCs. Moreover, STING was essential for radiation-induced adaptive immune responses, which relied on type I IFN signaling on DCs. Exogenous IFN-? treatment rescued the cross-priming by cGAS or STING-deficient DCs. Accordingly, activation of STING by a second messenger cGAMP administration enhanced antitumor immunity induced by radiation. Thus radiation-mediated antitumor immunity in immunogenic tumors requires a functional cytosolic DNA-sensing pathway and suggests that cGAMP treatment might provide a new strategy to improve radiotherapy.

USP22 deficiency in melanoma mediates resistance to T cells through IFNγ-JAK1-STAT1 signal axis.

Genome-wide clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated 9 (Cas9)-mediated loss-of-function screens are powerful tools for identifying genes responsible for diverse phenotypes. Here, we perturbed genes in melanoma cells to screen for genes involved in tumor escape from T cell-mediated killing. Multiple interferon gamma (IFNγ) signaling-related genes were enriched in melanoma cells resistant to T cell killing. In addition, deletion of the deubiquitinating protease ubiquitin specific peptidase 22 (USP22) in mouse melanoma (B16-OVA) cells decreased the efficacy of T cell-mediated killing, both in vitro and in vivo, while overexpression enhanced tumor-cell sensitivity to T (OT-I) cell-mediated killing. USP22 deficiency in both mouse and human melanoma cells showed impaired sensitivity to interferon pathway and USP22 was positively correlated with key molecules of interferon pathway in clinical melanoma samples. Mechanistically, USP22 may directly interact with signal transducer and activator of transcription 1 (STAT1), deubiquitinate it, and improve its stability in both human and mouse melanoma cells. Our findings identified a previously unknown function of USP22 and linked the loss of genes in tumor cells that are essential for escaping the effector function of CD8+ T cells during immunotherapy.

Adaptive immune cells temper initial innate responses.

Toll-like receptors (TLRs) recognize conserved microbial structures called pathogen-associated molecular patterns. Signaling from TLRs leads to upregulation of co-stimulatory molecules for better priming of T cells and secretion of inflammatory cytokines by innate immune cells. Lymphocyte-deficient hosts often die of acute infection, presumably owing to their lack of an adaptive immune response to effectively clear pathogens. However, we show here that an unleashed innate immune response due to the absence of residential T cells can also be a direct cause of death. Viral infection or administration of poly(I:C), a ligand for TLR3, led to cytokine storm in T-cell- or lymphocyte-deficient mice in a fashion dependent on NK cells and tumor necrosis factor. We have further shown, through the depletion of CD4+ and CD8+ cells in wild-type mice and the transfer of T lymphocytes into Rag-1-deficient mice, respectively, that T cells are both necessary and sufficient to temper the early innate response. In addition to the effects of natural regulatory T cells, close contact of resting CD4+CD25-Foxp3- or CD8+ T cells with innate cells could also suppress the cytokine surge by various innate cells in an antigen-independent fashion. Therefore, adaptive immune cells have an unexpected role in tempering initial innate responses.

Cetuximab-mediated tumor regression depends on innate and adaptive immune responses.

Epidermal growth factor receptor (EGFR) over-signaling leads to more aggressive tumor growth. The antitumor effect of Cetuximab, an anti-EGFR antibody, depends on oncogenic-signal blockade leading to tumor cell apoptosis and antibody dependent cell-mediated cytotoxicity (ADCC). However, whether adaptive immunity plays a role in Cetuximab-mediated tumor inhibition is unclear, as current xenograft models lack adaptive immunity and human-EGFR-dependent mouse tumor cell lines are unavailable. Using a newly developed xenograft model with reconstituted immune cells, we demonstrate that the Cetuximab effect becomes more pronounced and reduces the EGFR(+) human tumor burden when adaptive immunity is present. To further study this in a mouse tumor model, we created a novel EGFR(+) mouse tumor cell line and demonstrated that Cetuximab-induced tumor regression depends on both innate and adaptive immunity components, including CD8(+) T cells, MyD88, and FcγR. To test whether strong innate signals inside tumor tissues amplifies the Cetuximab-mediated therapeutic effect, Cetuximab was conjugated to CpG. This conjugate is more potent than Cetuximab alone for complete tumor regression and resistance to tumor rechallenge. Furthermore, Cetuximab-CpG conjugates can activate tumor-reactive T cells for tumor regression by increasing dendritic cell (DC) cross-presentation. Therefore, this study establishes new models to evaluate immune responses induced by antibody-based treatment, defines molecular mechanisms, and provides new tumor-regression strategies.

Dysregulation of Wnt/ß-catenin signaling contributes to intestinal inflammation through regulation of group 3 innate lymphoid cells.

RORγt+ group 3 innate lymphoid cells (ILC3s) are essential for intestinal homeostasis. Dysregulation of ILC3s has been found in the gut of patients with inflammatory bowel disease and colorectal cancer, yet the specific mechanisms still require more investigation. Here we observe increased ß-catenin in intestinal ILC3s from inflammatory bowel disease and colon cancer patients compared with healthy donors. In contrast to promoting RORγt expression in T cells, activation of Wnt/ß-catenin signaling in ILC3s suppresses RORγt expression, inhibits its proliferation and function, and leads to a deficiency of ILC3s and subsequent intestinal inflammation in mice. Activated ß-catenin and its interacting transcription factor, TCF-1, cannot directly suppress RORγt expression, but rather alters global chromatin accessibility and inhibits JunB expression, which is essential for RORγt expression in ILC3s. Together, our findings suggest that dysregulated Wnt/ß-catenin signaling impairs intestinal ILC3s through TCF-1/JunB/RORγt regulation, further disrupting intestinal homeostasis, and promoting inflammation and cancer.

A novel antagonist of the CCL5/CCR5 axis suppresses the tumor growth and metastasis of triple-negative breast cancer by CCR5-YAP1 regulation.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer (BC) with a high mortality rate, and few effective therapeutic strategies are available. CCL5/CCR5 is an appealing immunotherapeutic target for TNBC. However, its signaling mechanism is poorly understood and its direct antagonists have not been reported. Here, we developed a high-throughput screening (HTS) assay for discovering its antagonists. Verteporfin was identified as a more selective and potent antagonist than the known CCR5 antagonist maraviroc. Without photodynamic therapy, verteporfin demonstrated significant inhibition on TNBC tumor growth through immune regulation, remarkable suppression of lung metastasis by cell-intrinsic mechanism, and a significant extension of overall survival in vivo. Mechanistically, CCR5 was found to be essential for expression of the key hippo effector YAP1. It promoted YAP1 transcription via HIF-1α and exerted further control over the migration of CD8+ T, NK, and MDSC immune cells through chemokines CXCL16 and CXCL8 which were identified from RNA-seq. Moreover, the CCR5-YAP1 axis played a vital role in promoting metastasis by modulating ß-catenin and core epithelial-mesenchymal transition transcription factors ZEB1 and ZEB2. It is noteworthy that the regulatory relationship between CCR5 and YAP1 was observed across various BC subtypes, TNBC patients, and showed potential relevance in fifteen additional cancer types. Overall, this study introduced an easy-to-use HTS assay that streamlines the discovery of CCL5/CCR5 axis antagonists. Verteporfin was identified as a specific molecular probe of this axis with great potentials as a therapeutic agent for treating sixteen malignant diseases characterized by heightened CCR5 and YAP1 levels.

TANK-binding kinase 1 attenuates PTAP-dependent retroviral budding through targeting endosomal sorting complex required for transport-I.

Retroviruses need to bud from producer cells to spread infection. To facilitate its budding, some virus hijacks the multivesicular body (MVB) pathway that is normally used to cargo and degrade ubiquitylated cellular proteins, through interaction between the late domain of Gag polyproteins and the components of MVB machinery. In this study, we demonstrated that TANK-binding kinase 1 (TBK1) directly interacted with VPS37C, a subunit of endosomal sorting complex required for transport-I (ESCRT-I) in the MVB pathway, without affecting the ultrastructure or general function of MVB. Interestingly, overexpression of TBK1 attenuated, whereas short hairpin RNA interference of TBK1 enhanced HIV-1 pseudovirus release from Vero cells in type I IFN (IFN-I)-independent manner. Down-regulation of TBK1 by short hairpin RNA in TZM-bl cells also enhanced live HIV-1 NL4-3 or JR-CSF virus budding without involvement of IFN-I induction. Furthermore, infection of TBK1-deficient mouse embryonic fibroblast cells with a chimeric murine leukemia virus/p6, whose PPPY motif was replaced by PTAP motif of HIV-1, showed that lack of TBK1 significantly enhanced PTAP-dependent, but not PPPY-dependent retrovirus budding. Finally, phosphorylation of VPS37C by TBK1 might regulate the viral budding efficiency, because overexpression of the kinase-inactive mutant of TBK1 (TBK1-K38A) in Vero cells accelerated HIV-1 pseudovirus budding. Therefore, through tethering to VPS37C of the ESCRT-I complex, TBK1 controlled the speed of PTAP-dependent retroviral budding through phosphorylation of VPS37C, which would serve as a novel mechanism of host cell defense independent of IFN-I signaling.

A spike-targeting bispecific T cell engager strategy provides dual layer protection against SARS-CoV-2 infection in vivo.

Neutralizing antibodies exert a potent inhibitory effect on viral entry; however, they are less effective in therapeutic models than in prophylactic models, presumably because of their limited efficacy in eliminating virus-producing cells via Fc-mediated cytotoxicity. Herein, we present a SARS-CoV-2 spike-targeting bispecific T-cell engager (S-BiTE) strategy for controlling SARS-CoV-2 infection. This approach blocks the entry of free virus into permissive cells by competing with membrane receptors and eliminates virus-infected cells via powerful T cell-mediated cytotoxicity. S-BiTE is effective against both the original and Delta variant of SARS-CoV2 with similar efficacy, suggesting its potential application against immune-escaping variants. In addition, in humanized mouse model with live SARS-COV-2 infection, S-BiTE treated mice showed significantly less viral load than neutralization only treated group. The S-BiTE strategy may have broad applications in combating other coronavirus infections.

T cell receptor ß-chain-targeting chimeric antigen receptor T cells against T cell malignancies.

The success of chimeric antigen receptor (CAR) T cells in treating B cell malignancies comes at the price of eradicating normal B cells. Even though T cell malignancies are aggressive and treatment options are limited, similar strategies for T cell malignancies are constrained by the severe immune suppression arising from bystander T cell aplasia. Here, we show the selective killing of malignant T cells without affecting normal T cell-mediated immune responses in vitro and in a mouse model of disseminated leukemia. Further, we develop a CAR construct that carries the single chain variable fragment of a subtype-specific antibody against the variable TCR ß-chain region. We demonstrate that these anti-Vß8 CAR-T cells are able to recognize and kill all Vß8+ malignant T cells that arise from clonal expansion while sparing malignant or healthy Vß8- T cells, allowing sufficient T cell-mediated cellular immunity. In summary, we present a proof of concept for a selective CAR-T cell therapy to eradicate T cell malignancies while maintaining functional adaptive immunity, which opens the possibility for clinical development.

Hyper innate responses in neonates lead to increased morbidity and mortality after infection.

Neonates suffer high morbidity and mortality in infection, presumably because of the lack of a fully developed adaptive and innate immune system. Evidence of poor innate responses in neonates has been shown by using a model that sensitizes the host to Toll-like receptor (TLR)-mediated inflammation with d-galactosamine (d-GalN). However, we show that neonatal mice demonstrate much stronger inflammatory responses than adult mice in response to LPS stimulation, and such hypersensitivity extends to other TLR agonists including actual viral infection. Our study reveals that the ensuing inflammatory reaction after d-GalN sensitization reflects preferential toxicity of d-GalN to adult liver cells, rather than accurately reflecting the TLR response to LPS. We show further that an uncontrolled proinflammatory innate response due to inadequate T cells makes neonates more vulnerable to TLR agonists or viral infection. Remarkably, through transfer of T cells into neonates or depletion of T cells in adult mice, we show that T cells are sufficient and necessary to control the early inflammatory response to LPS. Therefore, neonates might suffer from the unleashed innate responses caused by an insufficient number of T cells, which leads to increased morbidity and mortality.

A CLDN18.2-Targeting Bispecific T Cell Co-Stimulatory Activator for Cancer Immunotherapy.

BACKGROUND: Co-stimulatory receptor agonist antibodies have shown promising antitumor efficacy in preclinical models. However, their clinical development lags due to systemic or local adverse effects of non-specific T cell activation. Utilization of a bispecific antibody format to reduce off-tumor immune activation is a focus of co-stimulatory receptor agonist antibody design. METHODS: In this study, a bispecific antibody with anti-CLDN18.2 and anti-CD28 moieties was produced. Its T cell costimulation ability was evaluated in T cell coculture assay in vitro. Its safety and anti-tumor efficacy were explored in mouse tumor models. RESULTS: Anti-CLDN18.2-anti-CD28 bispecific antibody could co-stimulate T cells and increase the expression of effector cytokines in a CLDN18.2-dependent manner. Treatment of anti-CLDN18.2-anti-CD28 could reduce tumor burden and increase tumor-infiltrated T cells. Immunosuppressive cells including tumor-associated macrophages and myeloid-derived suppressor cells were also reduced without systemic adverse effects. CONCLUSION: This work provided proof-of-concept evidence for a new strategy to develop a bispecific co-stimulatory activator for treating CLDN18.2+ tumors.

Type I Interferon Promotes Antitumor T Cell Response in CRPC by Regulating MDSC.

BACKGROUND: Metastatic castration-resistant prostate cancer (CRPC) is the leading cause of death among prostate cancer patients. Here, our aim was to ascertain the immune regulatory mechanisms involved in CRPC development and identify potential immunotherapies against CRPC. METHODS: A CRPC model was established using Myc-CaP cells in immune-competent FVB mice following castration. The immune cell profile of the tumor microenvironment (TME) was analyzed during CRPC development. Different immunotherapies were screened in the CRPC tumor model, and their efficacies and underlying mechanisms were investigated in vitro and in vivo. RESULTS: During CRPC development, the proportion of granulocytic myeloid-derived suppressor cells (G-MDSCs) in the TME increased. Among the immunotherapies tested, IFNα was more effective than anti-PD-L1, anti-CTLA-4, anti-4-1BB, IL-2, and IL-9 in reducing Myc-CaP CRPC tumor growth. IFNα reduced the number of G-MDSCs both in vitro during differentiation and in vivo in CRPC mice. Furthermore, IFNα reduced the suppressive function of G-MDSCs on T cell proliferation and activation. CONCLUSION: G-MDSCs are crucial to effective immunotherapy against CRPC. Treatment with IFNα presents a promising therapeutic strategy against CRPC. Besides the direct inhibition of tumor growth and the promotion of T cell priming, IFNα reduces the number and the suppressive function of G-MDSCs and restores T cell activation.

Bcl-2 Enhances Chimeric Antigen Receptor T Cell Persistence by Reducing Activation-Induced Apoptosis.

PURPOSE: To evaluate the potential added value of integrating anti-apoptotic molecules for improving the anti-tumor activity of CAR-T cells. METHODS: Four small molecules inhibiting apoptosis were tested for their ability to prevent activated induced CAR-T cell death. Five CD20-targeting, CD137 (4-1BB) and CD3ζ integrated CAR-T cells (20BBZ) with constitutively expressed anti-apoptotic genes were established, and we screened out the strongest proliferation enhancer: Bcl-2. The memory subtype and the exhaustion markers of CAR-T cells were analyzed. The anti-tumor activities of Bcl-2 integrating CAR-T cells (20BBZ-Bcl-2) were evaluated in vitro and in a mouse xenograft lymphoma model. CONCLUSION: The 20BBZ-Bcl-2 CAR-T cells showed improved proliferation ability compared to 20BBZ CAR-T cells in vitro. In addition, activation-induced apoptosis was reduced in the 20BBZ-Bcl-2 CAR-T cells. Consistent with the enhanced proliferation in vitro, 20BBZ-Bcl-2 CAR-T cells exhibited improved anti-tumor activity in a mouse xenograft lymphoma model.

Engineering mesenchymal stromal cells with neutralizing and anti-inflammatory capability against SARS-CoV-2 infection.

The emergence of the novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to the pandemic of coronavirus disease 2019 (COVID-19), which has markedly affected global health and the economy. Both uncontrolled viral replication and a proinflammatory cytokine storm can cause severe tissue damage in patients with COVID-19. SARS-CoV-2 utilizes angiotensin-converting enzyme 2 (ACE2) as its entry receptor. In this study, we generated ACE2 extracellular domain-Fc and single-chain variable fragment-interleukin 6 (IL-6) single-chain variable fragment against IL-6 receptor (scFv-IL6R)-Fc fusion proteins to differentially neutralize viruses and ameliorate the cytokine storm. The human ACE2 (hACE2)1-740-Fc fusion protein showed a potent inhibitory effect on pseudo-typed SARS-CoV-2 entry and a good safety profile in mice. In addition, scFv-IL6R-Fc strongly blocked IL-6 signal activation. We also established a mesenchymal stromal cell (MSC)-based hACE21-740-Fc and scFv-IL6R-Fc delivery system, which could serve as a potential therapy strategy for urgent clinical needs of patients with COVID-19.

A chimeric antigen receptor with antigen-independent OX40 signaling mediates potent antitumor activity.

Although chimeric antigen receptor (CAR)-modified T cells have shown great success in the treatment of B cell malignancies, this approach has limited efficacy in patients with solid tumors. Various modifications in CAR structure have been explored to improve this efficacy, including the incorporation of two costimulatory domains. Because costimulatory signals are transduced together with T cell receptor signals during T cell activation, we engineered a type of CAR-T cells with a costimulatory signal that was activated independently from the tumor antigen to recapitulate physiological stimulation. We screened 12 costimulatory receptors to identify OX40 as the most effective CAR-T function enhancer. Our data indicated that these new CAR-T cells showed superior proliferation capability compared to current second-generation CAR-T cells. OX40 signaling reduced CAR-T cell apoptosis through up-regulation of genes encoding Bcl-2 family members and enhanced proliferation through increased activation of the NF-κB (nuclear factor κB), MAPK (mitogen-activated protein kinase), and PI3K-AKT (phosphoinositide 3-kinase to the kinase AKT) pathways. OX40 signaling not only enhanced the cytotoxicity of CAR-T cells but also reduced exhaustion markers, thereby maintaining their function in immunosuppressive tumor microenvironments. In mouse tumor models and in patients with metastatic lymphoma, these CAR-T cells exhibited robust amplification and antitumor activity. Our findings provide an alternative option for CAR-T optimization with the potential to overcome the challenge of treating solid tumors.

4-1BB Signaling Boosts the Anti-Tumor Activity of CD28-Incorporated 2nd Generation Chimeric Antigen Receptor-Modified T Cells.

While chimeric antigen receptor-modified T (CAR-T) cells have shown great success for the treatment of B cell leukemia, their efficacy appears to be compromised in B cell derived lymphoma and solid tumors. Optimization of the CAR design to improve persistence and cytotoxicity is a focus of the current CAR-T study. Herein, we established a novel CAR structure by adding a full length 4-1BB co-stimulatory receptor to a 28Z-based second generation CAR that targets CD20. Our data indicated that this new 2028Z-4-1BB CAR-T cell showed improved proliferation and cytotoxic ability. To further understand the mechanism of action, we found that constitutive 4-1BB sensing significantly reduced the apoptosis of CAR-T cells, enhanced proliferation, and increased NF-κB pathway activation. Consistent with the enhanced proliferation and cytotoxicity in vitro, this new structure of CAR-T cells exhibited robust persistence and anti-tumor activity in a mouse xenograft lymphoma model. This work provides evidence for a new strategy to optimize the function of CAR-T against lymphoma.

cGAS-STING-mediated DNA sensing maintains CD8+ T cell stemness and promotes antitumor T cell therapy.

Although cGAS-STING-mediated DNA sensing in tumor cells or phagocytes is central for launching antitumor immunity, the role of intrinsic cGAS-STING activation in T cells remains unknown. Here, we observed that peripheral blood CD8+ T cells from patients with cancer showed remarkably compromised expression of the cGAS-STING cascade. We demonstrated that the cGAS-STING cascade in adoptively transferred CD8+ T cells was essential for antitumor immune responses in the context of T cell therapy in mice. Mechanistically, cell-autonomous cGAS and STING promoted the maintenance of stem cell-like CD8+ T cells, in part, by regulating the transcription factor TCF1 expression. Moreover, autocrine cGAS-STING-mediated type I interferon signaling augmented stem cell-like CD8+ T cell differentiation program mainly by restraining Akt activity. In addition, genomic DNA was selectively enriched in the cytosol of mouse CD8+ T cells upon in vitro and in vivo stimulation. STING agonism enhanced the formation of stem-like central memory CD8+ T cells from patients with cancer and potentiated antitumor responses of CAR-T cell therapy in a xenograft model. These findings advance our understanding of inherent cGAS-STING activation in T cells and provide insight into the development of improved T cell therapy by harnessing the cGAS-STING pathway for cancer immunotherapy.

Genome-Wide CRISPR Screening Identifies JAK1 Deficiency as a Mechanism of T-Cell Resistance.

Somatic gene mutations play a critical role in immune evasion by tumors. However, there is limited information on genes that confer immunotherapy resistance in melanoma. To answer this question, we established a whole-genome knockout B16/ovalbumin cell line by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease technology, and determined by in vivo adoptive OT-I T-cell transfer and an in vitro OT-I T-cell-killing assay that Janus kinase (JAK)1 deficiency mediates T-cell resistance via a two-step mechanism. Loss of JAK1 reduced JAK-Signal transducer and activator of transcription signaling in tumor cells-resulting in tumor resistance to the T-cell effector molecule interferon-and suppressed T-cell activation by impairing antigen presentation. These findings provide a novel method for exploring immunotherapy resistance in cancer and identify JAK1 as potential therapeutic target for melanoma treatment.

Optimization of 4-1BB antibody for cancer immunotherapy by balancing agonistic strength with FcγR affinity.

Costimulation of T cell responses with monoclonal antibody agonists (mAb-AG) targeting 4-1BB showed robust anti-tumor activity in preclinical models, but their clinical development was hampered by low efficacy (Utomilumab) or severe liver toxicity (Urelumab). Here we show that isotype and intrinsic agonistic strength co-determine the efficacy and toxicity of anti-4-1BB mAb-AG. While intrinsically strong agonistic anti-4-1BB can activate 4-1BB in the absence of FcγRs, weak agonistic antibodies rely on FcγRs to activate 4-1BB. All FcγRs can crosslink anti-41BB antibodies to strengthen co-stimulation, but activating FcγR-induced antibody-dependent cell-mediated cytotoxicity compromises anti-tumor immunity by deleting 4-1BB+ cells. This suggests balancing agonistic activity with the strength of FcγR interaction as a strategy to engineer 4-1BB mAb-AG with optimal therapeutic performance. As a proof of this concept, we have developed LVGN6051, a humanized 4-1BB mAb-AG that shows high anti-tumor efficacy in the absence of liver toxicity in a mouse model of cancer immunotherapy.