Checkpoint Receptors Research Articles

Peripheral immune cells in metastatic breast cancer patients display a systemic immunosuppressed signature consistent with chronic inflammation

Immunotherapies blocking the PD-1/PD-L1 checkpoint show some efficacy in metastatic breast cancer (mBC) but are often hindered by immunosuppressive mechanisms. Understanding these mechanisms is crucial for personalized treatments, with peripheral blood monitoring representing a practical alternative to repeated biopsies. In the present study, we performed a comprehensive mass cytometry analysis of peripheral blood immune cells in 104 patients with HER2 negative mBC and 20 healthy donors (HD). We found that mBC patients had significantly elevated monocyte levels and reduced levels of CD4+ T cells and plasmacytoid dendritic cells, when compared to HD. Furthermore, mBC patients had more effector T cells and regulatory T cells, increased expression of immune checkpoints and other activation/exhaustion markers, and a shift to a Th2/Th17 phenotype. Furthermore, T-cell phenotypes identified by mass cytometry correlated with functionality as assessed by IFN-γ production. Additional analysis indicated that previous chemotherapy and CDK4/6 inhibition impacted the numbers and phenotype of immune cells. From 63 of the patients, fresh tumor samples were analyzed by flow cytometry. Paired PBMC-tumor analysis showed moderate correlations between peripheral CD4+ T and NK cells with their counterparts in tumors. Further, a CD4+ T cell cluster in PBMCs, that co-expressed multiple checkpoint receptors, was negatively associated with CD4+ T cell tumor infiltration. In conclusion, the identified systemic immune signatures indicate an immune-suppressed environment in mBC patients who had progressed/relapsed on standard treatments, and is consistent with ongoing chronic inflammation. These activated immuno-suppressive mechanisms may be investigated as therapeutic targets, and for use as biomarkers of response or treatment resistance.

Abstract CT274: BGB-A317-LBL-007-202: A phase 2, randomized, active-controlled, open-label study to evaluate the efficacy and safety of LBL-007 (anti-LAG-3) in combination with tislelizumab (TIS; anti-PD-1) plus chemotherapy (chemo) as first-line (1L) treatment in patients with unresectable locally advanced/metastatic esophageal squamous cell carcinoma (ESCC)

Abstract Background: ESCC is the predominant histological subtype of esophageal cancer, accounting for 85% of cases. Patients (pts) with locally advanced/metastatic ESCC have poor clinical outcomes, with a 5-year survival rate of 6.1% for pts with distant metastases. 1L treatment with programmed cell death protein-1 (PD-1) inhibitors + platinum-based chemo has become the new standard of care for metastatic ESCC, however, there is an unmet need for enhanced treatment efficacy and a prolonged life span. LBL-007 is a monoclonal antibody (mAb) against lymphocyte activation gene-3 (LAG-3), an immune checkpoint receptor that negatively regulates T-cell activity. TIS is an anti-PD-1 mAb that blocks the PD-1/programmed death-ligand 1 (PD-L1) immune checkpoint, resulting in T-cell activation. This study (NCT06010303) aims to evaluate the efficacy and safety of LBL-007 + TIS + chemo as a 1L treatment in pts with unresectable, locally advanced/metastatic ESCC. Methods: This phase 2 study will enroll approximately 116 pts with a pathologically confirmed diagnosis of unresectable, locally advanced/metastatic ESCC and no prior systemic therapy. Pts will be randomized 2:1 to either Arm A (LBL-007 600 mg intravenously [IV] every 3 weeks [Q3W] + TIS 200 mg IV Q3W + chemo doublet) or Arm B (TIS 200 mg IV Q3W + chemo doublet), stratified by PD-L1 expression (tumor area positivity score ≥10% or <10%). The chemo doublet will consist of either cisplatin (60-80 mg/m2 IV Q3W) + 5-fluorouracil (750-800 mg/m2 IV daily on Days 1-5 Q3W), or cisplatin + paclitaxel (175 mg/m2 IV Q3W), determined by the investigator before randomization. Treatments will be administered until disease progression, intolerable toxicity, or withdrawal for other reasons. The primary endpoint is the overall response rate, as assessed by the investigator per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. Secondary endpoints include progression-free survival, duration of response, and disease control rate (all by investigator per RECIST v1.1), and the incidence and severity of adverse events per National Cancer Institute-Common Terminology Criteria for Adverse Events v5.0. A safety monitoring committee is monitoring the safety of LBL-007 + TIS + chemo vs TIS + chemo. Exploratory endpoints include comparison of overall survival, assessment of predictive, prognostic, and pharmacodynamic biomarkers, pharmacokinetic evaluation of LBL-007 and TIS, and immunogenicity. The study is currently recruiting at approximately 46 sites across Asia, including Taiwan, mainland China, South Korea, and Thailand. Citation Format: Sook Ryun Park, Ming-Huang Chen, Arunee Dechaphunkul, Ningning Ding, Xiao Lin, Jinghui Zhang, Vivian Li, Qiao Li, Yi Ba. BGB-A317-LBL-007-202: A phase 2, randomized, active-controlled, open-label study to evaluate the efficacy and safety of LBL-007 (anti-LAG-3) in combination with tislelizumab (TIS; anti-PD-1) plus chemotherapy (chemo) as first-line (1L) treatment in patients with unresectable locally advanced/metastatic esophageal squamous cell carcinoma (ESCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT274.

(361) - Soluble Immune Check Point Receptors Could be Feasible Markers of Rejection in Lung Transplanted Patients?

(361) - Soluble Immune Check Point Receptors Could be Feasible Markers of Rejection in Lung Transplanted Patients?

New advances in the treatment of chondrosarcoma under the PD-1/PD-L1 pathway.

Bone sarcomas encompass a group of spontaneous mesenchymal malignancies, among which osteosarcoma, Ewing sarcoma, chondrosarcoma, and chordoma are the most common subtypes. Chondrosarcoma, a relatively prevalent malignant bone tumor that originates from chondrocytes, is characterized by endogenous cartilage ossification within the tumor tissue. Despite the use of aggressive treatment approaches involving extensive surgical resection, chemotherapy, and radiotherapy for patients with osteosarcoma, chondrosarcoma, and chordoma, limited improvements in patient outcomes have been observed. Furthermore, resistance to chemotherapy and radiation therapy has been observed in chondrosarcoma and chordoma cases. Consequently, novel therapeutic approaches for bone sarcomas, including chondrosarcoma, need to be uncovered. Recently, the emergence of immunotherapy and immune checkpoint inhibitors has garnered attention given their clinical success in various diverse types of cancer, thereby prompting investigations into their potential for managing chondrosarcoma. Considering that circumvention of immune surveillance is considered a key factor in the malignant progression of tumors and that immune checkpoints play an important role in modulating antitumor immune effects, blockers or inhibitors targeting these immune checkpoints have become effective therapeutic tools for patients with tumors. One such checkpoint receptor implicated in this process is programmed cell death protein-1 (PD-1). The association between PD-1 and programmed cell death ligand-1 (PD-L1) and cancer progression in humans has been extensively studied, highlighting their remarkable potential as biomarkers for cancer treatment. This review comprehensively examines available studies on current chondrosarcoma treatments and advancements in anti-PD-1/PD-L1 blockade therapy for chondrosarcoma.

BAP1 Deficiency Inflames the Tumor Immune Microenvironment and Is a Candidate Biomarker for Immunotherapy Response in Malignant Pleural Mesothelioma

IntroductionMalignant pleural mesothelioma (MPM) is a rare and universally lethal malignancy with limited treatment options. Immunotherapy with immune checkpoint inhibitors (ICIs) has recently been approved for unresectable MPM, but response to ICIs is heterogeneous, and reliable biomarkers for prospective selection of appropriate subpopulations likely to benefit from ICIs remain elusive. MethodsWe performed multiscale integrative analyses of published primary tumor data set from The Cancer Genome Atlas (TCGA) and the French cohort E-MTAB-1719 to unravel the tumor immune microenvironment of MPM deficient in BAP1, one of the most frequently mutated tumor suppressor genes (TSGs) in the disease. The molecular profiling results were validated in independent cohorts of patients with MPM using immunohistochemistry and multiplex immunohistochemistry. ResultsWe revealed that BAP1 deficiency enriches immune-associated pathways in MPM, leading to increased mRNA signatures of interferon alfa/gamma response, activating dendritic cells, immune checkpoint receptors, and T-cell inflammation. This finding was confirmed in independent patient cohorts, where MPM tumors with low BAP1 levels are associated with an inflammatory tumor immune microenvironment characterized by increased exhausted precursor T-cells and macrophages but decreased myeloid-derived suppressor cells (MDSCs). In addition, BAP1low MPM cells are in close proximity to T cells and therefore can potentially be targeted with ICIs. Finally, we revealed that BAP1-proficient MPM is associated with a hyperactive mitogen-activated protein kinase (MAPK) pathway and may benefit from treatment with MEK inhibitors (MEKis). ConclusionOur results suggest that BAP1 plays an immunomodulatory role in MPM and that BAP1-deficient MPM may benefit from immunotherapy, which merits further clinical investigation.

Association of TRAIL receptor with phosphatase SHP-1 enables repressing T cell receptor signaling and T cell activation through inactivating Lck

BackgroundT cell receptor (TCR) signaling and T cell activation are tightly regulated by gatekeepers to maintain immune tolerance and avoid autoimmunity. The TRAIL receptor (TRAIL-R) is a TNF-family death receptor that transduces apoptotic signals to induce cell death. Recent studies have indicated that TRAIL-R regulates T cell-mediated immune responses by directly inhibiting T cell activation without inducing apoptosis; however, the distinct signaling pathway that regulates T cell activation remains unclear. In this study, we screened for intracellular TRAIL-R-binding proteins within T cells to explore the novel signaling pathway transduced by TRAIL-R that directly inhibits T cell activation.MethodsWhole-transcriptome RNA sequencing was used to identify gene expression signatures associated with TRAIL-R signaling during T cell activation. High-throughput screening with mass spectrometry was used to identify the novel TRAIL-R binding proteins within T cells. Co-immunoprecipitation, lipid raft isolation, and confocal microscopic analyses were conducted to verify the association between TRAIL-R and the identified binding proteins within T cells.ResultsTRAIL engagement downregulated gene signatures in TCR signaling pathways and profoundly suppressed phosphorylation of TCR proximal tyrosine kinases without inducing cell death. The tyrosine phosphatase SHP-1 was identified as the major TRAIL-R binding protein within T cells, using high throughput mass spectrometry-based proteomics analysis. Furthermore, Lck was co-immunoprecipitated with the TRAIL-R/SHP-1 complex in the activated T cells. TRAIL engagement profoundly inhibited phosphorylation of Lck (Y394) and suppressed the recruitment of Lck into lipid rafts in the activated T cells, leading to the interruption of proximal TCR signaling and subsequent T cell activation.ConclusionsTRAIL-R associates with phosphatase SHP-1 and transduces a unique and distinct immune gatekeeper signal to repress TCR signaling and T cell activation via inactivating Lck. Thus, our results define TRAIL-R as a new class of immune checkpoint receptors for restraining T cell activation, and TRAIL-R/SHP-1 axis can serve as a potential therapeutic target for immune-mediated diseases.

Characterization of Pleural Mesothelioma by Hierarchical Clustering Analyses Using Immune Cells within Tumor Microenvironment

Introduction: Over the past decade, classifications using immune cell infiltration have been applied to many types of tumors; however, mesotheliomas have been less frequently evaluated. Methods: In this study, 60 well-characterized pleural mesotheliomas (PMs) were evaluated immunohistochemically for the characteristics of immune cells within tumor microenvironment (TME) using 10 immunohistochemical markers: CD3, CD4, CD8, CD56, CD68, CD163, FOXP3, CD27, PD-1, and TIM-3. For further characterization of PMs, hierarchical clustering analyses using these 10 markers were performed. Results: Among the immune cell markers, CD3 (p < 0.0001), CD4 (p = 0.0016), CD8 (p = 0.00094), CD163+ (p = 0.042), and FOXP3+ (p = 0.025) were significantly associated with an unfavorable clinical outcome. Immune checkpoint receptor expressions on tumor-infiltrating lymphocytes such as PD-1 (p = 0.050), CD27 (p = 0.014), and TIM-3 (p = 0.0098) were also associated with unfavorable survival. Hierarchical clustering analyses identified three groups showing specific characteristics and significant associations with patient survival (p = 0.016): the highest number of immune cells (ICHigh); the lowest number of immune cells, especially CD8+ and CD163+ cells (ICLow); and intermediate number of immune cells (ICInt). ICHigh tumors showed significantly higher expression of PD-L1 (p = 0.00038). Cox proportional hazard model identified ICHigh [hazard ratio (HR) = 2.90] and ICInt (HR = 2.97) as potential risk factors compared with ICLow. Tumor CD47 (HR = 2.36), tumor CD70 (HR = 3.04), and tumor PD-L1 (HR = 3.21) expressions were also identified as potential risk factors for PM patients. Conclusion: Our findings indicate immune checkpoint and/or immune cell-targeting therapies against CD70-CD27 and/or CD47-SIRPA axes may be applied for PM patients in combination with PD-L1-PD-1 targeting therapies in accordance with their tumor immune microenvironment characteristics.

Abstract 5555: Lung squamous cancer cell mTORC2 signaling suppresses antitumor immunity by up-regulation of PSGL-1, a ligand of VISTA/PD-1H checkpoint receptor

Abstract Lung squamous cell carcinoma (LUSC) represents 30% of non-small cell lung cancer (NSCLC) cases and has a high mortality rate with limited targeted therapies. Unlike lung adenocarcinoma (LUAD), which has seen advancements in targeted therapies, LUSC has not benefited from similar breakthroughs despite having similar genetic abnormalities. While immune checkpoint inhibitor therapies have shown promise in some LUSC patients, a significant portion does not respond effectively, leaving limited treatment options. In this study, we investigated vulnerabilities in NSCLC and found that a substantial number of LUSC patients have genetic alterations in the PI3K-mTORC2-AKT signaling pathway. By using CRISPR/CAS-9, we showed that disrupting mTORC2 function in LUSC cells reduced glycolysis and lactate secretion, which in turn reduced tumor growth in vivo. Remarkably, the loss of mTORC2 also enhanced the activity of CD4+ and CD8+ T cells within the tumors. To further understand the metabolic and immune changes associated with mTORC2 loss of function, we performed RNA sequencing comparing wild-type (WT) and mTORC2-deficient cells. Our results confirmed a link between mTORC2 and HIF-2α, while regulating PSGL-1, a ligand of the VISTA/PD-1H checkpoint receptor. Furthermore, introducing a stable, non-degradable form of HIF-2α in mTORC2-deficient tumor cells restored PSGL-1 expression in vitro and in vivo. These results suggest that the interaction between PSGL-1 and VISTA plays a role in suppressing the anti-tumor immune response in LUSC tumors. Indeed, anti-VISTA treatment inhibited the growth of LUSC WT tumors in vivo, suggesting that mTORC2 plays a role in regulating PSGL-1 expression in the tumor microenvironment. Together, these data demonstrate that targeting mTORC2 or inhibiting VISTA checkpoint receptor may serve as a potential therapeutic strategy for improving immunotherapy in LUSC. Citation Format: Verra M. Ngwa, Yoonha Hwang, Deanna N. Edwards, Wenqiang Song, Jin Chen. Lung squamous cancer cell mTORC2 signaling suppresses antitumor immunity by up-regulation of PSGL-1, a ligand of VISTA/PD-1H checkpoint receptor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5555.

Abstract 89: Comprehensive cell based bioassay approaches for characterization, and clinical development of therapeutic agonistic antibodies for cancer immunotherapy and autoimmune diseases

Abstract Agonistic antibodies are emerging as promising therapeutics for targeting immune checkpoints, particularly those within the TNF Receptor Superfamily, as they play a crucial role in regulating immune cell function, especially in the context of cancer treatment. In addition, there is also a growing focus on the potential of agonistic antibodies to selectively activate co-inhibitory checkpoint receptors. This offers a promising avenue for suppressing inflammation in autoimmune diseases and restoring tolerance in graft-vs-host disease (GvHD) while avoiding the complications of global immunosuppression. While a substantial number of clinical trials are currently underway for oncology and autoimmune indications, there is a notable scarcity of commercially available assays to support the clinical development of this class of therapeutics, impacting their time-to-clinic. Existing assays frequently fail to accurately assess the agonistic activity of antibodies as they are unable to replicate the necessary physiologically relevant conditions. In this context, we present several case studies that highlight the pivotal role of cell-based bioassay approaches developed by Eurofins DiscoverX in driving the characterization and clinical development of agonistic antibody therapeutics targeting various checkpoint receptors. Additionally, we discuss our data demonstrating the indispensable role of FcyR-mediated antibody clustering in establishing the otherwise elusive agonistic activity of antibodies. Citation Format: Venkatesh Chari, Jennifer Lin-Jones, Luhan Yang, Jane E. Lamerdin, Gaurav Agrawal. Comprehensive cell based bioassay approaches for characterization, and clinical development of therapeutic agonistic antibodies for cancer immunotherapy and autoimmune diseases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 89.

Abstract 7547: Enhancers as targets for improvements in immunotherapy

Abstract Role of epigenetic elements in mediating tumor immune interaction remains poorly understood. We previously identified enrichment of active enhancer states on a set of genomic loci in non-responders to immune checkpoint blockade (ICB) therapy. We noted that the activated non-responder enhancers marked a group of key regulators of in melanoma cells that are known to mediate resistance to ICB therapy and several checkpoint receptors in T cells. Through spatial epigenomics (Spatial ATAC and CUT&amp;Tag) approaches, we identified the tumor-immune niches harboring unique gene regulatory elements and transcription factors that could mediate melanoma-T cell interaction. Further, we aimed to identify functional epigenetic elements through custom CRISPRi screening of enhancers in patient tumor-derived melanoma and T cells. CRISPRi approaches identified novel functional enhancers that mediate T cell mediated killing. For example, we identified distal c-MET enhancers as important contributors to T cell mediated killing. In T cells, we identified enhancer hubs that target multiple genes. These hubs could be targeted to activate interferon gamma, reduce T cell exhaustion, and improve T cell mediated killing of melanoma cells. Such enhancer hubs could serve as targets in the ex vivo setting to improve adoptive T cell therapy. Overall, our results suggest that enhancers with unique spatial patterns in melanoma tumors contribute to the response to immunotherapy and could be novel targets for therapy. Citation Format: Anand Singh, Veena Kochat, Emre Arslan, Suresh Satpati, Wentao Deng, Sandeep Yadav, Efthalia Bataki, Cassian Yee, Kunal Rai. Enhancers as targets for improvements in immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7547.

Abstract 5176: TIGIT expression increases with advancing clinical stages and does not differ across racial groups in resected pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) has a dismal 12% 5-year survival rate (SEER) due to a lack of early detection biomarkers and resistance to standard therapeutic options (surgery, chemotherapy, radiation). Black African Americans (BAA) have 20% increased incidence of PDAC compared to those with European Ancestry (EA). TIGIT, an immune checkpoint receptor, is a marker of T cell exhaustion and plays a key role in the inhibition of anti-tumor immune responses. Recent studies have demonstrated that immune checkpoint receptor expression (PD-1 and TIGIT) on specific T cell populations correlates to worse overall survival (OS). TIGIT inhibitors are being explored in clinical trials in pancreatic cancer due to implications of its ligand (CD155) promoting immune evasion. We hypothesize that targeted anti-TIGIT therapy, in conjunction with other therapies targeting the tumor microenvironment, could reverse the immune suppression that is characteristic of PDAC. We performed RNAscope in situ hybridization (ISH) with a probe specific for human TIGIT mRNA (combined with a nuclear counterstain) on 79 tissue samples. The cohort of tissue samples included 8 biopsies (endoscopic-guided fine needle biopsies at time of diagnosis), 66 primary (from surgical resection), and 5 metastatic (liver core biopsies from patients with a primary PDAC diagnosis) formalin-fixed paraffin-embedded (FFPE) tissue sections from patients with histologically confirmed PDAC. After cells were segmented based on nuclear recognition, the presence of TIGIT probe within the cytoplasm of each cell was determined and quantified. Percent positive cell values were then exported for statistical analysis in R. De-identified clinical metadata was obtained from REDCap, a cloud-based HIPAA-compliant database used to compile patient data for research purposes. We tested for associations between %TIGIT present and clinical covariates, using linear regression for continuous outcomes, and logistic regression for binary outcomes. ScRNAseq revealed that TIGIT mRNA is enriched in, but not exclusive to the T/NK cellular compartments in PDAC. Staining analysis showed that TIGIT expression did not differ significantly between racial groups (comparing BAA to non-BAA). The mean percentage of TIGIT positive cells was 64.0%. High expression of TIGIT was associated with clinical stage, where an increase in stage was associated with increasing %TIGIT (p &amp;lt; 0.05).The TIGIT biomarker assay can be conducted at time of diagnosis, time of surgical resection, and time of metastatic biopsy. If patients’ samples contain high levels of TIGIT expression, these patients may be candidates for anti-TIGIT drug therapy. Considering that TIGIT expression correlates with advancing clinical stage, patients with more advanced staging at diagnosis (stage IIB, III, IV) especially may benefit from anti-TIGIT therapy. Citation Format: Madison George, Julie Clark, Kendyll Gartrelle, Georges Nassif, Kailee Hartway, Daniel Long, Daniel Salas-Escabillas, Allison Wombwell, Thais Pichardo, Hui-Ju Wen, Simone Benitz, Samuel Zwernik, Rupen Shah, Hakmin Park, Philip, Gazala Khan, Howard Crawford, David Kwon, Brian Theisen, Nina Steele. TIGIT expression increases with advancing clinical stages and does not differ across racial groups in resected pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5176.

Abstract 7539: First-in-class anti-PVR mAb NTX1088 advancing through Phase I: Safe and potent in restoring DNAM1 expression to enhance antitumor immunity

Abstract NTX1088, a first-in-class anti-PVR (CD155) mAb, is currently evaluated in a Phase 1, open-label, multi-center study (NCT05378425). The trial initiated at MD Anderson Cancer Center, and was expanded into additional sites, including City of Hope, Ochsner Health, Sheba Medical Center and Hadassah Medical Center. Study objectives are safety, dose-finding, and efficacy with focus on pharmacokinetics, pharmacodynamics, and biomarker discovery. NTX1088 is investigated as a single agent and in combination with the anti-PD1 mAb, pembrolizumab (Keytruda) in patients with advanced solid malignancies. Ongoing dose escalation demonstrates a safe profile across ascending dose levels. NTX1088 is a high affinity humanized IgG4-S228P mAb that binds PVR and blocks all known interacting receptors at a single nM EC50. PVR, is a highly upregulated membrane protein on numerous tumor cells. PVR expression has been associated with worse patient outcome, due to its central role in immune suppression. PVR’s impact is mediated through interaction with the key stimulatory receptor, DNAM1 (CD226), on T and NK cells, leading to internalization and degradation of DNAM1. PVR also interacts with the inhibitory immune checkpoint receptors, TIGIT, CD96 and KIR2DL5A. Blocking PVR by NTX1088 has multiple immune-stimulating roles, through restoration of DNAM1 immune activation function, while simultaneously neutralizing TIGIT, CD96 and KIR2DL5A inhibitory signals in immune cells. Importantly, DNAM1 downmodulation was recently identified as a key resistance mechanism to approved immune checkpoint inhibitors, and its restoration by NTX1088 is a novel MoA, not demonstrated previously by other therapies.In vitro, as a monotherapy, NTX1088 significantly increased immune cell activation, superior to TIGIT, CD112R, and PD1 antibody blockade, leading to a greater immune-mediated tumor cell killing, IFNγ secretion, and CD137 induction. Importantly, only NTX1088 was able to restore DNAM1 to the surface of immune cells. Synergy was obtained when NTX1088 was combined with PD1 blockers, or with the anti-CD112R mAb, NTX2R13.Syngeneic models of PVRK.O, demonstrated a complete immune-mediated tumor regression. Numerous humanized murine xenograft models were investigated whereby NTX1088 exhibited robust tumor growth inhibition as a standalone and in combination with PD1 blockade.In conclusion, PVR blockade by NTX1088 has a remarkable pre-clinical efficacy, suggesting a potential clinical breakthrough, based on its ability to simultaneously overcome multiple tumor escape mechanisms. First-in-human (FIH) trial is currently ongoing and biomarker analysis is showing initial mechanistic proof of concept for NTX1088 mode of action, including the restoration of DNAM1 surface expression on patients’ immune cells. This is the first case of surface DNAM1 elevation in clinical settings. Citation Format: Anas Atieh, Akram Obeidat, Alon Vitenshtein, Guy Cinamon, Keren Paz, Tihana Roviš, Paola Brilc, Ofer Mandelboim, Stipan Jonjic, Pini Tsukerman. First-in-class anti-PVR mAb NTX1088 advancing through Phase I: Safe and potent in restoring DNAM1 expression to enhance antitumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7539.

Abstract 3903: Discovery of ULBP6 as a novel immuno-oncology target using pleiotropic signals from 23andMe’s genetic and health survey database

Abstract 23andMe has assembled one of the largest platforms for human genetics research that combines genotypes from 14 million individuals, 80% of which are consented to participate in research, with billions of phenotypic data points collected from health survey data. Using these large scale genetic and phenotypic datasets, we have developed a unique target discovery platform that has identified hundreds of pleiotropic genetic variants with opposing directionality of effects in cancer and immune diseases. These immune-oncology (I/O) genetic associations point to already clinically validated immune checkpoint receptors (e.g., CTLA4) and those currently in clinical trials (e.g., CD200R1). This suggests that these I/O genetic associations could be linked to genes that are broadly utilized by tumor cells to evade the immune system and could be used to identify novel therapeutic targets involved in regulating anti-tumor immune response. Here, we utilized expression quantitative trait loci (eQTLs) and annotation of coding single nucleotide polymorphisms (SNPs) to link one of these signals to a causal gene, and identified ULBP6, a stress-induced ligand for the activating immunoreceptor NKG2D found on NK and T cells. ULBP6 is known to be shed from the cell surface of tumor cells to block its interaction with NKG2D to evade immune surveillance. Expression profiling of ULBP ligands in various tumor types using MSD, IHC, bulk and single-cell RNA-seq revealed tumor-intrinsic up-regulation of ULBP6 in squamous cancer subtypes. Collectively, these data suggest that ULBP6 is a promising therapeutic target, and that can potentially enhance anti-tumor immunity. Citation Format: Susanne Tilk, Pierre Fontanillas, Wei-Jen Chung, Clifford Hom, Shi Shi, Anh Diep, Kim Gerrick, Mauro Poggio, Pranidhi Sood. Discovery of ULBP6 as a novel immuno-oncology target using pleiotropic signals from 23andMe’s genetic and health survey database [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3903.

Abstract 6345: In vitro characterization of a dual antagonistic anti-LILRB2/LILRB4 monoclonal antibody

Abstract Introduction: Myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment are a potential therapeutic target in immune checkpoint cancer therapy, but MDSC-targeted therapies have yet been shown to improve survival. The leukocyte immunoglobulin (Ig)-like receptor B2 is a member of the leukocyte Ig-like receptor (LILR) family and is predominantly expressed on the surface of cells of the myelomonocytic lineage (monocytes, macrophages and dendritic cells). LILRB2 is a negative regulator of myeloid cells and is an immune checkpoint receptor. We chose to generate mAbs against LILRB2 as a potential immunotherapeutic for cancer. Methods: PentaMice® strains (5 WT mouse strains comprising 9 MHC class II haplotypes to maximize Ab diversity) were immunized with human LILRB2. Lymphocytes were fused with a myeloma partner to generate lead monoclonal hybridomas. 24 purified anti-LILRB2 mAbs were generated and evaluated by arrayed surface plasma resonance (SPR, Carterra® LSA® instrument) to assign epitope bins. mAb humanization was performed in silico to maximize T20 “humanness” scores (algorithm developed by Curia). Humanized mAbs were transiently expressed using Curia’s TunaCHO™ platform and tested in in vitro MDSC assays. Autologous co-cultures of magnetic bead enriched-human blood-derived MDSC (HLA-DR-CD14+) model cells and T cells (CD3+) were stimulated with plate-bound anti-CD3/CD28 to induce T cell activation. Cytokine secretion was assessed 4 days later. Results: A total of 384 hybridoma supernatants were selected from the primary screen. 245 were confirmed by ELISA and 178 stained HEK293 cells expressing LILRB2 cells by flow cytometry (FACS). 24 hybridomas were further selected, cloned and sequenced. Five epitope bins were identified via Carterra® LSA® instrument. Two clones were chosen for humanization, designated 6-I11A and 4-O19A and were recombinantly expressed with the human IgG4 isotype. FACS analysis on HEK293 cells expressing either huLILRB2 or huLILRB4 revealed that clone hu4-O19A-IgG4 was specific for huLILRB2. Surprisingly, clone hu6-I11A-IgG4 stained both huLILRB2 and huLILRB4. FACS analysis with hu4-O19A-IgG4 on human MDSCs exhibited an EC50 of 11.9 nM and a KD of 1.5 nM in binding to recombinant huLILRB2 antigen, while hu6-I11A-IgG4 had an EC50 of 3.2 nM and a KD of 0.6 nM. In co-cultures with human MDSCs and T cells, both hu6-I11A-IgG4 and hu4-O19A-IgG4 reversed cytokine suppression by the MDSCs by increasing GM-CSF, IL-10, TNFα, and IL-6, while suppressing IL-13, and had little effect on IL-17A, MIP-3α, IL-4, IL-2 and IFNγ compared to treatment with the isotype control, with hu6-I11A-IgG4 having a greater effect as an antagonist than hu4-O19A-IgG4. Conclusions: We have identified a dual anti-LILRB2/LILRB4 antagonist. Targeting MDSCs with this antibody offers great promise for immunotherapy for cancer as well as its immense potential for synergy with PD-1 blockade. Citation Format: Bruce L. Daugherty, Xiaomei Ge, Christine L. Hsieh, Brian A. Zabel, Seth Lederman. In vitro characterization of a dual antagonistic anti-LILRB2/LILRB4 monoclonal antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6345.

Abstract 1377: The role of TIM3 and PD1 blockades in head and neck cancer

Abstract Background: Our group has recently developed and validated a novel prognostic score for human papillomavirus (HPV+) oropharyngeal cancer called UWO3, which stratifies patients into low risk (immune rich), intermediate risk (immune mixed), and high risk (immune desert) groups. The high-risk immune desert group had a paucity of immune cells, however, that population of lymphocytes expressed high levels of the checkpoint molecule TIM3. To follow up on this, we assessed the therapeutic effect of anti-TIM3 mAb alone and in combination with anti-PD-1 in a syngenic murine HPV+ head and neck cancer model using the mERR. T-cell immunoglobulin mucin 3 (TIM3) and Programmed death 1 (PD-1) are negative immune checkpoint receptors that are expressed on tumor-infiltrating lymphocytes (TIL), play a crucial role in tumor-induced immune suppression. Given the critical role that the tumour microenvironment (TME) has on the prognosis of head and neck squamous cell carcinoma (HNSCC), immune checkpoint inhibitor immunotherapy approaches, specifically anti-PD1 and/or anti-TIM3 antibody therapy, may be very effective treatment strategies and may offer improved survival outcomes. Methods:Immunocompetent C57BL/6 mice were injected in one flank with the syngeneic mouse HPV+ cell line, mEERL (106 cells), for tumour generation. Mice were then treated with either IgG2a isotype control, anti-PD1 (200μg), anti-TIM3 (200 μg) antibodies or a combination of anti-PD-1 and anti-TIM3 were administered via intraperitoneal injection 3 times per week following tumour establishement for 6 weeks (n = 7 mice per arm, total of 28 mice). Tumour volumes were measured every 2 days. Three representative tumors from each treatment group were collected for bulk RNA sequencing, scRNA-seq, and flow cytometry to characterise immune cell populations and transcriptional changes and monitor their impact on the TME of HNSCC. Results:Anti-PD1 and anti-TIM3 both restricted tumour growth by size and weight relative to the IgG2a control (p&amp;lt;0.01, linear mixed model [lmm]). The combination of anti-PD1 and anti-TIM3 was more effective than either monotherapy alone (p&amp;lt;0.05, lmm). RNA sequencing analysis revealed differential abundance in CCL6, CCL9, CFD, and MAP3K5 transcripts relative to control for anti-PD1, anti-TIM3, and combination checkpoint inhibition. Conclusion:Targeting both PD-1 and TIM3 enhanced the anti-tumor immune response in HPV+ head and neck tumours, providing further support for dual targeting of these molecules for more effective cancer immunotherapy. Our results suggest that immune checkpoint inhibitor therapy (PD1 and TIM3 blockades) could be a promising treatment strategy for HPV+ HNSCC, and the expression of these immune checkpoint molecules could serve as a predictive biomarker of patient outcome in HPV+ HNSCC. Citation Format: Mushfiq Shaikh, Amir Karimi, Peter Zeng, Harrison Pan, John Barrett, Anthony Nichols. The role of TIM3 and PD1 blockades in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1377.

Abstract 1358: Elucidating the contribution of T cell-intrinsic VISTA to the suppression of antitumor T cell immunity

Abstract Immune checkpoint receptors (ICRs) negatively regulate antitumor immune responses. While significant advances have been made in understanding the mechanisms of well-established ICRs such as PD-1 and CTLA-4, other checkpoint proteins remain incompletely characterized and may be targeted to synergistically boost antitumor immunity. One such protein is V-domain immunoglobulin suppressor of T-cell activation (VISTA), an ICR whose expression curtails the function of several lymphoid and myeloid lineages, including tumor-reactive cytotoxic T cells. Globally blocking VISTA elicits potent T cell-mediated antitumor immunity and systemic myeloid cell-mediated inflammatory responses. Mechanistically, VISTA has been shown to inhibit T cell activation by acting as an inhibitory ligand on antigen-presenting cells. However, the impact of T cell-intrinsic VISTA on modulating tumor-reactive T cell responses has not been thoroughly investigated, and it remains unclear whether blocking T cell-specific VISTA is adequate for revitalizing T cell-mediated tumor control. In this study, we utilized VISTA conditional knockout mice models to examine the relative contribution of T cell-intrinsic VISTA versus myeloid-derived VISTA in the regulation of antitumor immunity. We present evidence that blocking VISTA on T cells alone is insufficient to induce strong antitumor immune responses, whereas blocking VISTA on myeloid cells counteracts its dominant role in orchestrating T cell suppression. Citation Format: Sachin Patnaik, Elizabeth Delaney, Cassandra Gilmour, Keman Zhang, Amin Zakeri, Hieu M. Ta, Prerana B. Parthasarathy, Tyler Alban, Timothy Chan, Li Lily Wang. Elucidating the contribution of T cell-intrinsic VISTA to the suppression of antitumor T cell immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1358.

Abstract 1367: PD1 signaling uncovers a pathogenic subset of cytotoxic T cells

Abstract PD-1 drives its fame for serving as a pivotal immune checkpoint receptor on T cells. Within the realm of cancer immunotherapy, blocking this receptor triggers the T cell activation, leading to the immune response against tumors. Conversely, in autoimmunity, PD-1 agonist is a prime candidate for effectively suppressing the T-cell-driven auto-reactivity and self-tissue damage. Despite a decade of exploration and unlike cancer immunotherapy, the efficacy of PD-1 agonists in treating autoimmunity remains a challenge. To overcome this hurdle, innovative methods must be devised to look beyond the PD-1 receptor engagement and uncover the downstream effectors involved in PD-1 signal transduction. A comprehensive genome-wide CRISPR/Cas9 screen was also conducted to pinpoint genes linked to PD-1 signaling. An in-depth exploration of genes associated with PD-1 signaling was undertaken, utilizing publicly accessible bulk and single-cell RNA sequencing datasets of patients with melanoma treated with PD-1 blockade and in patients with inflammatory arthritis. We employed flow cytometry of T cells derived from peripheral blood and synovial fluid to validate the results.Our screening process validated established regulators in the proximal PD-1 signaling pathway and unveiled an additional 1,112 unique genes associated with PD-1's capacity to hinder T-cell functions. These genes demonstrated a robust correlation with the response of cancer patients to PD-1 blockades and exhibited high scores for tumor immune dysfunction and exclusion, affirming their downstream involvement in PD-1 signaling. Functional annotation underscored the significance of these genes in established immune regulation processes. Intriguingly, T cells isolated from patients with inflammatory arthritis exhibited a significant downregulation of the same genes, emphasizing their overarching inhibitory role. Examining single-cell RNA sequencing data revealed that five specific genes, KLRG1, CRTAM, SLAMF7, PTPN2, and KLRD1, were notably downregulated in activated and effector T cells from synovial fluids. Back-gating these genes to canonical cytotoxic T cell signatures identified PD-1+ HLA-DRHIGH KLRGLOW T cells as a novel inflammatory T cell subset that should be targeted with immunotherapies. Our findings suggest that PD-1+ HLA-DRHIGH KLRGLOW T cells are promising targets for prospective PD-1 antagonists and agonists in treating inflammatory diseases. This study not only reveals novel genes linked to PD-1 downstream functions but also serves as a valuable resource, offering insights for further investigations essential to delineate the role of PD-1 within immune responses. Citation Format: Shoiab Bukhari, Shalom Lerrer, Johanna Straube, Robert Winchester, Brian Henick, Matthew Dragovich, Adam Mor. PD1 signaling uncovers a pathogenic subset of cytotoxic T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1367.

Mechanistic Insights into the Inhibition of a Common CTLA-4 Gene Mutation in the Cytoplasmic Domain.

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is a pivotal immune checkpoint receptor, playing a crucial role in modulating T-cell activation. In this study, we delved into the underlying mechanism by which a common mutation, G199R, in the cytoplasmic domain of CTLA-4 impacts its inhibitory function. Utilizing nuclear magnetic resonance (NMR) spectroscopy and biochemical techniques, we mapped the conformational changes induced by this mutation and investigated its role in CTLA-4 activity. Our findings reveal that this mutation leads to a distinct conformational alteration, enhancing protein-membrane interactions. Moreover, functional assays demonstrated an improved capacity of the G199R mutant to downregulate T-cell activation, underscoring its potential role in immune-related disorders. These results not only enhance our understanding of CTLA-4 regulatory mechanisms but also provide insights for targeted therapeutic strategies addressing immune dysregulation linked to CTLA-4 mutations.

Transmembrane domain-driven PD-1 dimers mediate T cell inhibition.

Programmed cell death-1 (PD-1) is a potent immune checkpoint receptor on T lymphocytes. Upon engagement by its ligands, PD-L1 or PD-L2, PD-1 inhibits T cell activation and can promote immune tolerance. Antagonism of PD-1 signaling has proven effective in cancer immunotherapy, and conversely, agonists of the receptor may have a role in treating autoimmune disease. Some immune receptors function as dimers, but PD-1 has been considered monomeric. Here, we show that PD-1 and its ligands form dimers as a consequence of transmembrane domain interactions and that propensity for dimerization correlates with the ability of PD-1 to inhibit immune responses, antitumor immunity, cytotoxic T cell function, and autoimmune tissue destruction. These observations contribute to our understanding of the PD-1 axis and how it can potentially be manipulated for improved treatment of cancer and autoimmune diseases.

ImmunoPET imaging of TIGIT in the glioma microenvironment

Glioblastoma (GBM) is the most common primary malignant brain tumor. Currently, there are few effective treatment options for GBM beyond surgery and chemo-radiation, and even with these interventions, median patient survival remains poor. While immune checkpoint inhibitors (ICIs) have demonstrated therapeutic efficacy against non-central nervous system cancers, ICI trials for GBM have typically had poor outcomes. TIGIT is an immune checkpoint receptor that is expressed on activated T-cells and has a role in the suppression of T-cell and Natural Killer (NK) cell function. As TIGIT expression is reported as both prognostic and a biomarker for anti-TIGIT therapy, we constructed a molecular imaging agent, [89Zr]Zr-DFO-anti-TIGIT (89Zr-αTIGIT), to visualize TIGIT in preclinical GBM by immunoPET imaging. PET imaging and biodistribution analysis of 89Zr-αTIGIT demonstrated uptake in the tumor microenvironment of GBM-bearing mice. Blocking antibody and irrelevant antibody tracer studies demonstrated specificity of 89Zr-αTIGIT with significance at a late time point post-tracer injection. However, the magnitude of 89Zr-αTIGIT uptake in tumor, relative to the IgG tracer was minimal. These findings highlight the features and limitations of using 89Zr-αTIGIT to visualize TIGIT in the GBM microenvironment.