V-domain Immunoglobulin Suppressor Of T Cell Activation Research Articles

Abstract CT181: First-in-human phase I of anti-VISTA monoclonal antibody W0180 with and without anti-PD-1 pembrolizumab in patients with locally advanced or metastatic solid tumors

Abstract Background: V-domain Immunoglobulin Suppressor of T cell Activation (VISTA) is an immune checkpoint regulator highly expressed on myeloid cells. VISTA has been shown to maintain tumor microenvironment (TME) in an immunosuppressive state. Its expression is reported as a resistance mechanism to immune checkpoint blockers, making it an attractive target for cancer treatment. Preclinical data showed that VISTA blockade mediates antitumor activity by activating the antitumor immune response and is enhanced in combination with anti-PD-1. W0180 is a humanized, Fc competent, IgG1 antibody targeting VISTA with high affinity. This study investigates W0180 with/without pembrolizumab (pembro) in patients (pts) with solid tumors. Methods: Pts initially received W0180 monotherapy in dose escalation (3.5-600 mg weekly (QW)). Following evaluation of the first 3 dose levels in monotherapy, dose escalation of W0180 (60 to 300 mg QW) in combination with pembro (200 mg Q3W) started in pts treated with prior anti-PD-(L)1. Objectives were to characterize safety and tolerability of W0180, determine RDE and PK/PD on blood and paired tumor biopsies. Results: By October 2023, 33 pts were treated in dose escalation, 24 pts with W0180 monotherapy and 9 pts with W0180 + pembro. Two dose-limiting toxicities were observed, Grade 2 subacute cerebral infarction and Grade 3 infusion related reaction (IRR). Overall, 33 pts experienced ≥1 treatment-emergent AE (TEAE). Most common TEAEs were IRR (32/33), fatigue (14/33), and anemia (11/33). Grade 3/4 TEAEs occurred in 23 pts, neutropenia (6/23) and anemia (6/23) were the most common. There was no treatment-related death. 6 (18%) pts discontinued due to AEs. Following the observation of Grade 3 arterial thromboembolism (n=1) and Grade 2 subacute cerebral infarction (n=1), eligibility criteria were amended to require adequate lipid profile, troponin and exclude pts with history of arterial thrombotic events and current smoking. W0180 PK was nonlinear with a rapid clearance at 3.5-600 mg doses. No objective response was observed but 5 pts had stable disease (SD) lasting for >16 weeks. One pt with appendix cancer treated at 600mg monotherapy had SD for >15 months. One pt with head and neck cancer treated at 300mg in combination had SD for 13 months. Biomarkers data suggested evidence of PD effect with a trend for dose response through sustained increase of proliferative CD8+ T-cells in blood at the highest W0180 exposures and increased density of tumor-infiltrating lymphocytes in 10 out of 16 pts. These changes were independent of tumor VISTA expression level and correlated to high PD-L1 expression (CPS>5) for 4 pts at baseline. Conclusions: Analysis is ongoing to assess the RDE of W0180 + pembro and collect additional evidence of proof of mechanism in pts with solid tumors. NCT04564417 Citation Format: Carlos Gomez-Roca, Stéphane Champiat, Philippe Cassier, David Jegou, Marie Primard, Aurélie Pétain, Geneviève Gueguen-Dorbes, Claire Fabre, Ignacio Melero, Aurélien Marabelle. First-in-human phase I of anti-VISTA monoclonal antibody W0180 with and without anti-PD-1 pembrolizumab in patients with locally advanced or metastatic solid tumors [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 CT181.

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.

Viewing the immune checkpoint VISTA: landscape and outcomes across cancers

Optimizing immune checkpoint inhibitor (ICI) therapy may require identification of co-targetable checkpoint pathways via immune profiling. Herein, we analyzed the transcriptomic expression and clinical correlates of V-domain immunoglobulin suppressor of T-cell activation (VISTA), a promising targetable checkpoint. RNA sequencing was carried out on 514 tissues reflecting diverse advanced/metastatic cancers. Expression of eight immune checkpoint markers [lymphocyte-activation gene 3 (LAG-3), tumor necrosis factor receptor superfamily 14 (TNFRSF14), programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), programmed death-ligand 2 (PD-L2), B- and T-lymphocyte attenuator (BTLA), T-cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), cytotoxic T-lymphocyte antigen 4 (CTLA-4)], in addition to VISTA, was analyzed, along with clinical outcomes. High VISTA RNA expression was observed in 32% of tumors (66/514) and was the most common highly expressed checkpoint among the nine assessed. High VISTA expression was independently correlated with high BTLA, TIM-3, and TNFRSF14, and with a diagnosis of pancreatic, small intestine, and stomach cancer. VISTA transcript levels did not correlate with overall survival (OS) from metastatic/advanced disease in the pan-cancer cohort or with immunotherapy outcome (progression-free survival and OS from the start of ICI) in 217 ICI-treated patients. However, in ICI-treated pancreatic cancer patients (n = 16), median OS was significantly shorter (from immunotherapy initiation) for the high- versus not-high-VISTA groups (0.28 versus 1.21 years) (P= 0.047); in contrast, VISTA levels were not correlated with OS in 36 pancreatic cancer patients who did not receive ICI. High VISTA expression correlates with high BTLA, TIM-3, and TNFRSF14 checkpoint-related molecules and with poorer post-immunotherapy survival in pancreatic cancer, consistent with prior literature indicating that VISTA is prominently expressed on CD68+ macrophages in pancreatic cancers and requiring validation in larger prospective studies. Immunomic analysis may be important for individualized precision immunotherapy.

Blockade of V-domain immunoglobulin suppressor of T-cell activation reprograms tumour-associated macrophages and improves efficacy of PD-1 inhibitor in gastric cancer.

In gastric cancer, the response rate of programmed cell death protein-1 (PD-1) inhibitor is far from satisfactory, indicating additional nonredundant pathways might hamper antitumour immunity. V-domain immunoglobulin suppressor of T-cell activation (VISTA) has been reported in several malignancies as a novel immune-checkpoint. Nevertheless, the role of VISTA in gastric cancer still remains obscure. Our purpose is to explore the clinical significance and potential mechanism of VISTA in affecting gastric cancer patients' survival and immunotherapeutic responsiveness. Our study recruited eight independent cohorts with a total of 1403 gastric cancer patients. Immunohistochemistry, multiplex immunofluorescence, flow cytometry or intracellular flow cytometry, quantitative polymerase chain reaction, western blotting, fluorescence-activated cell sorting, magnetic-activated cell sorting, smart-seq2, in vitro cell co-culture and ex vivo tumour inhibition assays were applied to investigate the clinical significance and potential mechanism of VISTA in gastric cancer. VISTA was predominantly expressed on tumour-associated macrophages (TAMs), and indicated poor clinical outcomes and inferior immunotherapeutic responsiveness. VISTA+ TAMs showed a mixed phenotype. Co-culture of TAMs and CD8+ T cells indicated that VISTA+ TAMs attenuated effective function of CD8+ T cells. Blockade of VISTA reprogrammed TAMs to a proinflammatory phenotype, reactivated CD8+ T cells and promoted apoptosis of tumour cells. Moreover, blockade of VISTA could also enhance the efficacy of PD-1 inhibitor, suggesting that blockade of VISTA might synergise with PD-1 inhibitor in gastric cancer. Our data revealed that VISTA was an immune-checkpoint associated with immunotherapeutic resistance. Blockade of VISTA reprogrammed TAMs, promoted T-cell-mediated antitumour immunity, and enhanced efficacy of PD-1 inhibitor, which might have implications in the treatment of gastric cancer.

Identification of novel immuno-oncology compounds as VISTA-inhibitors for cancer therapy: A computational approach integrating virtual screening and molecular dynamics simulation

The landscape of cancer treatment has witnessed a paradigm shift with the emergence of immunotherapy, particularly the inhibition of immune checkpoints like programmed cell death protein 1 (PD-1) and its ligand PD-L1. While these therapies have revolutionized cancer treatment, a substantial proportion of patients still fail to respond, highlighting the need to explore alternative immune checkpoints. V-domain immunoglobulin suppressor of T cell activation (VISTA), a member of the B7 family, has orchestrated significant attention. Abundantly expressed in tumor-infiltrating lymphocytes, VISTA's role in regulating immune responses, especially in breast cancer, hints at its potential as a linchpin in breast cancer immunotherapy. This research focuses on molecular docking simulations of a diverse array of immuno-oncology compounds to identify potential VISTA inhibitors. Three promising candidates (Compound_6784, Compound_14718, and Compound_34839) exhibited favorable binding affinities with VISTA, forming key interactions with critical amino acid residues. ADME-Tox profiling revealed these compounds to be highly druggable, displaying minimal toxicity risks, making them suitable for clinical trials and drug development. Additionally, molecular dynamics simulations provided insights into the structural dynamics of these compounds. The metrics underline the superior stability of Compound_14718, making it the most promising candidate for further research and drug development. This research lays a robust foundation for the development of novel immunotherapies targeting VISTA in cancer treatment. The identified compounds present promising candidates for further investigation and drug development, offering hope for improved cancer immunotherapy strategies.

VISTA Non-redundantly Regulates Proliferation and CD69low γδ T cell Accumulation in the Intestine in Murine Sepsis.

Sepsis is a dysregulated systemic immune response to infection that is responsible for ∼35% of in-hospital deaths at a significant fiscal health care cost. Our laboratory, among others, has demonstrated the efficacy of targeting negative checkpoint regulators (NCRs) to improve survival in a murine model of sepsis, cecal ligation and puncture (CLP). B7-CD28 superfamily member, V-domain Immunoglobulin Suppressor of T cell Activation (VISTA), is an ideal candidate for strategic targeting in sepsis. VISTA is a 35-45 kDa type 1 transmembrane protein with unique biology that sets it apart from all other NCRs. We recently reported that VISTA-/- mice had a significant survival deficit post CLP which was rescued upon adoptive transfer of a VISTA-expressing pMSCV-mouse Foxp3-EF1α-GFP-T2A-puro stable Jurkat cell line (Jurkatfoxp3 T cells). Based on our prior study, we investigated the effector cell target of Jurkatfoxp3 T cells in VISTA-/- mice. γδ T cells are a powerful lymphoid subpopulation that require regulatory fine-tuning by Tregs to prevent overt inflammation/pathology. In this study, we hypothesized that Jurkatfoxp3 T cells non-redundantly modulate the γδ T cell population post CLP. We found that VISTA-/- mice have an increased accumulation of intestinal CD69low γδ T cells which are not protective in murine sepsis. Adoptive transfer of Jurkatfoxp3 T cells, decreased the intestinal γδ T cell population, suppressed proliferation, skewed remaining γδ T cells toward a CD69high phenotype, and increased sCD40L in VISTA-/- mice post CLP. These results support a potential regulatory mechanism by which VISTA skews intestinal γδ T cell lineage representation in murine sepsis.

Immune Checkpoint Expression Patterns on T Cell Subsets in Light-Chain Amyloidosis: VISTA, PD-1, and Tigit As Potential Therapeutic Targets

Abstract Background: Systemic immunoglobulin light chain amyloidosis (AL amyloidosis) is a rare plasma cell dyscrasia with a poor prognosis. T-cell exhaustion can lead to impaired T cell-mediated antitumor immunity, but there is limited information available regarding the T-cell immunodeficiency status in AL amyloidosis. This study aims to investigate the T-cell immune checkpoint expression patterns in AL amyloidosis and its relationship with clinicobiological characteristics. Methods: Using multi-color fluorescent flow cytometry, we examined the expression levels of V-domain immunoglobulin suppressor of T cell activation (VISTA), programmed death 1 (PD-1), T cell immunoglobulin and mucin-domain-containing-3 (Tim-3), T cell immunoreceptor with Ig and ITIM domains (TIGIT) on CD3+, CD4+, CD8+ T-cell, and regulatory T cell (Treg) in peripheral blood (PB) and bone marrow (BM) from 19 patients with newly diagnosed AL amyloidosis. We used 36 PB and BM samples from patients with newly diagnosed multiple myeloma (MM) and 19 PB and 10 BM samples from healthy individuals (HIs) as controls. Results: Our results showed that PB from patients with AL amyloidosis had significantly higher percentages of VISTA+ and PD-1+ subsets within CD3+, CD4+, CD8+ T cells and Tregs when compared to HIs. No statistical differences for frequency of VISTA+, PD-1+, Tim-3+ and TIGIT+ T-cell in BM were observed between the two groups. The percentages of double-positive VISTA+ PD-1+, VISTA+ Tim-3+, VISTA+ TIGIT+, PD-1+ Tim-3+ and PD-1+ TIGIT+ T cells in PB from the patients with AL amyloidosis were also considerably higher than those in the HIs. Moreover, we discovered that the patients with renal involvement had greater percentages of PD-1+ or TIGIT+ subsets within CD3+, CD4+ T cells and Tregs than the individuals without renal involvement. Additionally, PD-1+CD3+%, PD-1+CD4+%, and PD-1+Treg% were found to be positively correlated with 24-hour proteinuria levels. Furthermore, we observed that the AL amyloidosis patients had significantly higher counts of PD-1+ Treg in PB than the MM patients, while the MM patients had significantly higher counts of TIGIT+ subsets within CD3+, CD4+ and CD8+ T cells than the AL amyloidosis patients. Conclusions: Our findings suggest that there are elevated proportions of VISTA+ and PD-1+ T cells in PB of AL amyloidosis patients, which are indicators of an immunosuppressive milieu. The rise in PD-1+ or TIGIT+ T cells was associated with renal damage. Notably, MM and AL amyloidosis have very distinct immunosuppressive patterns based on immune checkpoint alteration. Overall, VISTA, PD-1, and TIGIT may be considered as potential targets for reversing T cell exhaustion and enhancing T cell activity in AL amyloidosis.

Effective Antitumor Immunity Can Be Triggered by Targeting VISTA in Combination with a TLR3-Specific Adjuvant.

Resistance to anti-PD-1/PD-L1 treatment is often associated with accumulation of intratumoral inhibitory macrophages. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is a nonredundant immune checkpoint that can induce both T-cell and myeloid-cell immunosuppression. In this study, we found that high levels of VISTA+ immune cells were associated with advanced stage bladder cancer and predicted poor survival in patients. A combination of high infiltration of VISTA+ immune cells and PD-L1+ immune cells or PD-1+ T cells predicted the worst survival. Flow cytometry and multiplex immunofluorescence analyses confirmed that VISTA expression was higher in macrophages than in T cells or neutrophils, and only VISTA+CD163+ macrophage density predicted poor prognosis in patients with bladder cancer. Toll-like receptor (TLR) agonists are known to trigger the innate immune response in macrophages. We found that the VISTA-specific mAb 13F3 augmented the ability of a TLR3-specific adjuvant to induce macrophage activation in vitro. In the MB49 syngeneic mouse model of bladder cancer, treatment with 13F3 curbed tumor growth and prolonged survival when combined with a TLR3-specific adjuvant. The combination treatment reduced the intratumoral frequency of CD206+ anti-inflammatory macrophages and levels of the immunosuppressive molecule TGFβ1, but it upregulated expression of immunostimulatory molecules (Ifna, Ifnb, and Trail) and increased the CD8+ T cell/regulatory T-cell ratio. These findings indicate that elevated VISTA expression in immune cells, particularly macrophages, is associated with an unfavorable prognosis in patients with bladder cancer and suggest that targeting VISTA in combination with a TLR3-specific adjuvant has translational potential.

Imatinib and M351-0056 enhance the function of VISTA and ameliorate the development of SLE via IFN-I and noncanonical NF-κB pathway.

V-domain immunoglobulin suppressor of T-cell activation (VISTA), an important negative checkpoint protein, participates in immunoregulation. Systemic lupus erythematosus (SLE) is an autoimmune disease in which patients exhibit high levels of autoantibodies and multi-organ tissue injury, primarily involving the kidney and skin. In wild-type (WT) mice and Vsir-/- mice with pristane-induced lupus-like disease, we found that VISTA deficiency exacerbated the lupus-like disease in mice, possibly through aberrant activation of type I interferon (IFN-I) signaling, CD4+ T cell, and noncanonical nuclear factor-κB (NF-κB) pathway. Surface plasmon resonance results showed that imatinib, an FDA-approved tyrosine kinase inhibitor, may have a high affinity for human VISTA-ECD with a KD value of 0.2009 μM. The biological activities of imatinib and VISTA agonist M351-0056 were studied in monocytes and T cells and in lupus-like disease murine model of chronic graft-versus-host disease (cGVHD) and lupus-prone MRL/lpr mice. VISTA small-molecule agonist reduced the cytokine production of peripheral blood mononuclear cells (PBMCs) and Jurkat cells and inhibited PBMCs proliferation. Moreover, they attenuated the levels of autoantibodies, renal injury, inflammatory cytokines, chemokines, and immune cell expansion in the cGVHD mouse model and MRL/lpr mice. Our findings also demonstrated that VISTA small-molecule agonist ameliorated the development of SLE through improving aberrantly activated IFN-I signaling and noncanonical NF-κB pathway. In conclusion, VISTA has a protective effect on the development and progression of SLE. VISTA agonist M351-0056 and imatinib have been firstly demonstrated to attenuate SLE, suggesting interventions to enhance VISTA function may be effective in treating SLE. VISTA deficiency exacerbates pristane-induced lupus-like disease in mice by promoting activation of the IFN-I and noncanonical NF-κB pathway. Imatinib was screened as a small-molecule VISTA agonist by molecular docking, SPR, and cellular level experiments. VISTA agonists (M351-0056 and imatinib) alleviated lupus-like disease progression in the cGVHD mouse model and MRL/lpr mice by inhibiting activation of IFN-I and noncanonical NF-κB pathway.

Clinical and research updates on the VISTA immune checkpoint: immuno-oncology themes and highlights.

Immune checkpoints limit the activation of the immune system and serve an important homeostatic function but can also restrict immune responses against tumors. Inhibition of specific immune checkpoint proteins such as the B7:CD28 family members programmed cell death protein-1 (PD-1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) has transformed the treatment of various cancers by promoting the anti-tumor activation of immune cells. In contrast to these effects, the V-domain immunoglobulin suppressor of T-cell activation (VISTA) regulates the steady state of the resting immune system and promotes homeostasis by mechanisms distinct from PD-1 and CTLA-4. The effects of VISTA blockade have been shown to include a decrease in myeloid suppression coupled with proinflammatory changes by mechanisms that are separate and distinct from other immune checkpoint proteins; in some preclinical studies these immune effects appear synergistic. Given the potential benefits of VISTA blockade in the context of cancer therapy, the second Annual VISTA Symposium was convened virtually on September 23, 2022, to review new research from investigators and immuno-oncology experts. Discussions in the meeting extended the knowledge of VISTA biology and the effects of VISTA inhibition, particularly on cells of the myeloid lineage and resting T cells, as three candidate anti-VISTA antibodies are in, or nearing, clinical development.

Structure based virtual screening and molecular simulation study of FDA-approved drugs to inhibit human HDAC6 and VISTA as dual cancer immunotherapy

Cancer immunotherapy has significantly contributed to the treatment of various types of cancers mainly by targeting immune checkpoint inhibitors (ICI). Among them, V-domain immunoglobulin suppressor of T cell activation (VISTA) has been explored as a promising therapeutic target. Besides, histone deacetylase 6 (HDAC6) has been demonstrated to be efficacious target for several cancers. The current theoretical work was performed to explore the virtual repurposing of the FDA-approved drugs as inhibitors against these two (VISTA and HDAC6) cancers therapeutic targets. The crystal structure of the two proteins were downloaded from PDB and subjected to virtual screening by DrugRep webserver while using FDA-approved drugs library as ligands database. Our study revealed that Oxymorphone and Bexarotene are the top-ranked inhibitors of VISTA and HDAC6, respectively. The docking score of Bexarotene was predicted as − 10 kcal/mol while the docking score of Oxymorphone was predicted as − 6.2 kcal/mol. Furthermore, a total of 100 ns MD simulation revealed that the two drugs Oxymorphone and Bexarotene formed stable complexes with VISTA and HDAC6 drug targets. As compared to the standard drug the two drugs Oxymorphone and Bexarotene revealed great stability during the whole 100 ns MD simulation. The binding free energy calculation further supported the Root Mean Square Deviation (RMSD) result which stated that as compared to the ref/HDAC6 (− 18.0253 ± 2.6218) the binding free energy score of the Bexarotene/HDAC6 was good (− 51.9698 ± 3.1572 kcal/mol). The binding free energy score of Oxymorphone/VISTA and Ref/VISTA were calculated as − 36.8323 ± 3.4565, and − 21.5611 ± 4.8581 respectively. In conclusion, the two drugs deserve further consideration as cancer treatment option.

CD39 inhibition and VISTA blockade may overcome radiotherapy resistance by targeting exhausted CD8+ T cells and immunosuppressive myeloid cells

Although radiotherapy (RT) has achieved great success in the treatment of non-small cell lung cancer (NSCLC), local relapses still occur and abscopal effects are rarely seen even when it is combined with immune checkpoint blockers (ICBs). Here, we characterize the dynamic changes of tumor-infiltrating immune cells after RT in a therapy-resistant murine tumor model using single-cell transcriptomes and Tcell receptor sequencing. Atthe early stage, the innate and adaptive immune systems are activated. At the late stage, however, the tumorimmune microenvironment (TIME) shifts into immunosuppressive properties. Our study reveals that inhibition of CD39 combined with RT preferentially decreases the percentage of exhausted CD8+ Tcells. Moreover, we find that the combination of V-domain immunoglobulin suppressor of T cell activation (VISTA) blockade and RT synergistically reduces immunosuppressive myeloid cells. Clinically, high VISTA expression is associated with poor prognosis in patients with NSCLC. Altogether, our data provide deep insight into acquired resistance to RT from an immune perspective and present rational combination strategies.

Full spectrum flow cytometry-powered comprehensive analysis of PBMC as biomarkers for immunotherapy in NSCLC with EGFR-TKI resistance.

Clinical studies suggest that immune checkpoint inhibitor (ICI) monotherapy has limited benefits in non-small cell lung cancer (NSCLC) patients after epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) failure. However, data about efficacy of ICI plus chemotherapy remain controversial, probably attributed to the heterogeneity among such population, and robust efficacy biomarkers are urgent to explore. A total of 60 eligible patients who received ICI plus chemotherapy after EGFR-TKI treatment failure were enrolled, 24 of whom peripheral blood mononuclear cell (PBMC) samples were collected at baseline and after 2 cycles oftreatment. We have designed a 23-color-antibody panel to detect PBMC by full spectrum flow cytometry. For EGFR-TKI resistant NSCLC patients: 1) ICI plus chemotherapy achieved an objective response rate (ORR) of 21.7% and a median progression-free survival (PFS) of 6.4months. 2) clinical characteristics associated with worse efficacy included liver metastasis and platelet-to-lymphocyte ratio (PLR) > 200. 3) the proportion of immune cell subset associated with better efficacy was higher baseline effective CD4+T cells (E4). 4) the baseline expression of immune checkpoint proteins (ICPs) on cell subsets associated with better efficacy included: higher expression of CD25 on dendritic cells (DC) and central memory CD8+T cells (CM8), and higher expression of Lymphocyte activation gene 3 (LAG-3) on effective memory CD8+T cells (EM8). 5) the expression of ICPs after 2 cycles of treatment associated with better efficacy included: higher expression of CD25 on CD8+T/EM8 /natural killer (NK) cells. 6) the dynamic changes of ICPs expression associated with worse efficacy included: significantly decrease of T cell immunoglobulin and ITIM domain (TIGIT) expression on regular T cells (Tregs) and decrease of V-domain immunoglobulin suppressor of T cell activation (VISTA) expression on Th1. 7) a prediction model for the efficacy of ICI plus chemotherapy was successfully constructed with a sensitivity of 62.5%, specificity of 100%, and area under curve (AUC) = 0.817. Some EGFR-TKI-resistant NSCLC patients could indeed benefit from ICI plus chemotherapy, but most patients are primary resistant to immunotherapy. Comprehensive analysis of peripheral immune cells using full spectrum flow cytometry showed that compared to the proportion of cell subsets, the expression type and level of ICPs on immune cells, especially CD25, were significantly correlated with the efficacy of immunotherapy.

Expression of PD-L1 and VISTA in Intraductal Papillary Mucinous Neoplasm With Associated Invasive Carcinoma of the Pancreas

Early detection and treatment of invasive carcinoma arising in association with intraductal papillary mucinous neoplasm (IPMN), which is biologically and (epi)genetically distinct from conventional pancreatic ductal adenocarcinoma, provide an opportunity to improve the prognosis of this lethal disease. Despite the successful application of programmed death (ligand) 1 (PD-[L]1)-blocking strategies in numerous cancers, the immune microenvironment of IPMN with associated invasive carcinoma remains elusive. Here, we investigated CD8+ T cells, CD68+ macrophages, PD-L1, and V-domain immunoglobulin suppressor of T-cell activation (VISTA) in 60 patients with IPMN with associated invasive carcinoma using immunohistochemistry, explored their correlations with clinicopathologic variables and prognosis, and compared them with those in 76 patients with IPMN without invasive carcinoma (60 low-grade and 16 high-grade lesions). Using antibodies against CD8, CD68, and VISTA, we evaluated tumor-infiltrating immune cells in 5 high-power fields (×400) and calculated the corresponding mean counts. PD-L1 with a combined positive score of ≥1 was regarded as positive, and VISTA expression on tumor cells (TCs) was deemed positive when ≥1% of TCs showed membranous/cytoplasmic staining. A reduction of CD8+ T cells and an increase of macrophages were observed during carcinogenesis. Positive PD-L1 combined positive score and VISTA expression on TCs were 13% and 11% in the intraductal component of IPMN with associated invasive carcinoma, 15% and 12% in the associated invasive carcinoma, and 6% and 4% in IPMN without an invasive carcinoma, respectively. Interestingly, the PD-L1 positivity rate was the highest in a subset of associated invasive carcinomas (predominantly gastric-type-derived) and was associated with higher counts of CD8+ T cells, macrophages, and VISTA+ immune cells. Accumulation of VISTA+ immune cells was observed in the intraductal component of IPMN with associated invasive carcinoma compared with that of low-grade IPMN, whereas in intestinal-type IPMN with associated invasive carcinoma, the number of these cells decreased during the transition from the intraductal component to the associated invasive carcinoma. Survival analysis revealed that a higher number of macrophages predicted poorer prognosis. In conclusion, our results might help in individualized immunotherapeutic strategies for these patients.

342 The Implications of High Expression of VISTA, a Negative Check Point Regulator, on Prognosis Across Malignant Solid Tumors: a Systematic Review and Meta-Analysis

OBJECTIVES/GOALS: Targeting the V-domain immunoglobulin suppressor of T cell activation (VISTA) signaling pathway has been suggested as a promising approach for overcoming resistance to current immune checkpoint therapies in advanced cancer. This review will synthesize the rapidly-expanding literature on VISTA protein expression on prognosis in various cancers. METHODS/STUDY POPULATION: To determine the prognostic significance of high VISTA expression across treatment-naïve malignant tumors, a systematic review and meta-analysis will be performed of published cohort studies which measured VISTA protein expression on solid tumors. Primary and secondary outcome endpoints of overall survival (OS) and disease-specific survival (DSS) will be compared across cohort studies using a random effects model to calculate pooled hazard ratios (HRs) for each time-to-event end point with 95% CIs. For articles that only provide Kaplan-Meier (KM) curves, the Engauge Digitizer software will be used to measure the time and survival probability coordinates on the KM curves to estimate the HRs. Correlations of VISTA expression and clinicopathological characteristics will be evaluated by pooled risk ratios. RESULTS/ANTICIPATED RESULTS: A search of 4 electronic databases including Pubmed, Embase, Web of Science and Cochrane resulted in 5578 publications of which 66 containing a broad spectrum of malignant solid tumors will undergo full-text review for study inclusion. Tumor types most represented with at least 3 articles include lung, pancreas, skin, head & neck, colorectal, mesothelioma, cervix, soft tissue, breast, liver and ovarian. Our working hypothesis is that the pooled HR for high VISTA expression on overall survival will be approaching 1.0 given conflicting reports across the cancer literature. Risk of bias will be assessed across studies. Quantifications of heterogeneity will be assessed by visual exploration of forest plots as well as by multiple statistical metrics including the Q statistic and the I²coefficient. DISCUSSION/SIGNIFICANCE: The results of this systematic review and meta-analysis will provide a more comprehensive understanding of VISTA’s prognostic role both across all malignant tumors and for subgroups of similar tumor types which may impact the types of tumors and tumor microenvironments selected for early trials of anti-VISTA therapy.

Stereotactic Ablative Radiation Therapy in 3 Fractions Induces a Favorable Systemic Immune Cell Profiling in Prostate Cancer Patients

ABSTRACT The impact of radiotherapy (RT) on immune cell status in prostate cancer (PCa) is only partially determined. The aim of this study was to assess the effect of different RT strategies on peripheral B, T, and Natural killer (NK) lymphocytes at precise longitudinal time-points in PCa. 18 patients treated with stereotactic body radiation therapy (SBRT) (40 Gy/3FRX), definitive moderate-hypofractionation (62 Gy/20FRX), or post-operative conventional-fractionation RT (66–69 Gy/30FRX) were prospectively evaluated for the immune cell profile in terms of immune cell composition, differentiation stage, cytokine production and inhibitory receptor (IR) expression. The immune-monitoring of the 18 patients revealed that RT affects the balance of systemic immune cells, with the main differences observed between SBRT and conventionally fractionated RT. SBRT favorably impacts immune response in term of increased B cells, central-memory and effector-memory CD8+ T cells, along with decreased Treg cells after treatment. On the contrary, conventional fractionated RT had a long-term negative effect on the systemic immune profile, including a decrease of total lymphocyte counts accompanied by an increase of neutrophils-to-lymphocytes ratio. Total B and T cells decreased and Treg-to-CD8+ ratio increased. Functionality of T lymphocytes were not affected by any of the 3-fractionation schedules. Interestingly, SBRT significantly up-regulates the expression of V-domain immunoglobulin suppressor of T-cell activation (VISTA) in CD8+ T cells in the absence of other IRs. Our results indicate the relevance of systematic immunomonitoring during RT to identify novel immune-related target to design trials of combined radio-immunotherapy as a promising strategy in the clinical management of PCa.

Expression of Galectin-9-related immune checkpoint receptors in B-cell acute lymphoblastic leukemia.

Exhausted CD8+ T-cells over-express immune checkpoint receptors (ICRs), which interact with their ligands on malignant cells. However, some ICRs have been reported to be expressed on both T-cells and tumor cells, including V-domain immunoglobulin suppressor of T cell activation (VISTA), Galectin-9, and T-cell immunoglobulin mucin-3 (TIM-3). We aimed to evaluate the mRNA expression of VISTA, Galectin-9, and TIM-3 on CD8+ T-cells and leukemic cells in B-cell acute lymphoblastic leukemia (B-ALL). Samples were obtained from 26 untreated B-ALL patients and 25 control subjects. CD8+ T-cells were isolated using Magnetic Activated Cell Sorting (MACS). Relative gene expression was then evaluated by qRT-PCR with specific primers for VISTA, Galectin-9, and TIM-3. Also, the mRNA expression profile and clinical data of 154 B-ALL patients were obtained from the TARGET. mRNA expression of Galectin-9 on CD8+ T-cells in B-ALL patients was significantly lower than those in the control group (P=0.043), while VISTA expression was not significantly different between the two study groups (P=0.259). Besides, TIM-3 expression was significantly higher in B-ALL patients than in the control group (P<0.001). Also, data obtained from TARGET showed that the relapse incidence was not significantly different between patients with high and low expression of Galectin-9 and TIM-3 in leukemic cells (P=0.360 and P=0.655, respectively). Collectively, gene expression results suggest an important role for TIM-3, but not VISTA and Galectin-9, in B-ALL and it seems that TIM-3 could be a candidate for immune checkpoint therapy.

A Suboptimal Response in CML Is Associated with Expression of the Immune Checkpoint VISTA

Introduction: Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML) leading to molecular remission in most patients. The next challenges are decreasing resistance and improving the odds of treatment-free remission. Understanding determinants of disease persistence and suboptimal responses is critical for improving these probabilities. The role of the immune system in the control or eradication of CML has been demonstrated in multiple settings including successful graft-vs-leukemia effect and the requirement of active T-cells and natural killer (NK) cells for sustained remission prior to therapy discontinuation. Herein, we aim to demonstrate a comparison of immune determinants of response in CML in those who achieve a deep molecular response (MR4.5) compared to suboptimal responders. Methods: We prospectively collected longitudinal blood and bone marrow samples from patients receiving treatment for CML and characterized them using cytometry by time of flight (CyTOF). 20 patients that achieved MR4.5 at any time during their treatment were compared to a cohort of 32 patients with suboptimal response to therapy according to the European LeukemiaNet (ELN) response milestones (Table 1). We custom-designed this CyTOF panel (36-plex) to include markers of leukemia/stem progenitor cells, lineage defining, intracellular signaling, immune exhaustion and activation markers. Samples were barcoded, pooled and processed simultaneously to overcome technical variations and batch effects. CD45hi cells (leukocytes) were grouped using PhenoGraph clustering, based on expression of these markers in the earliest samples available, collected at various timepoints during treatment. Results: Analysis of differential expression patterns revealed 25 distinct clusters. Patients with suboptimal response to therapy had a higher proportion of CD45hiCD3+ cells (T-cells) compared to those with an optimal response (median of 59% vs 53%, P=0.04). Notably, this included a higher proportion of exhausted CD8+ cytotoxic T-cells in patients with suboptimal response characterized by high Eomes and low Tbet expression (median of 8.0% vs 1.9%, P=0.04). In contrast, CD56+ NK-cells were more prevalent in the optimal response group (median of 5.5% vs 3.2%, P=0.04), particularly an interferon gamma releasing (CD56hiCD16loTbet+) subpopulation (median of 4.1% vs 2.5%, P=0.04). While CD68+ cells (macrophages) were detected at similar rates in both the optimal and suboptimal response groups (median of 16.5% vs 15.5%, P=0.07), the phagocytic subpopulation (CD16-CD14+CD68+HLA-DRlo) was more prevalent in those who achieved an optimal response (median of 15.1% vs 13.2%, P=0.02). Patients with suboptimal response had a higher proportion of CD68+HLA-DRloVISTAhi cells (median of 5.6% vs 1.8%, P=0.004), referring to macrophages expressing the immune regulatory ligand V-domain immunoglobulin suppressor of T cell activation (VISTA). Like PD-L1 and other B7 family ligands, VISTA attenuates T-cells response to antigens and VISTA overexpression has been associated with resistance to immune checkpoint inhibitors in solid tumors. Furthermore, cells characterized by CD66b+CXCR4+VISTAlo were increased in patients with optimal response (median of 20.6% vs 0.6%, P=0.01), indicating a higher proportion of mature granulocytes with low expression of VISTA in the optimal response group (Figure 1). Conclusion: We found that higher expression of the immune checkpoint VISTA, in addition to markers of T-cells exhaustion is associated with suboptimal response to therapy in CML. These findings highlight the importance of the immune microenvironment in response to targeted therapies such as TKIs. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Expression and Prognostic Value of B7 Family Immune Checkpoints in Pancreatic Neuroendocrine Tumors.

Pancreatic neuroendocrine tumors (PanNETs) are rare malignancies with heterogeneous clinical courses requiring novel prognosticators and therapies. B7 family molecules have an important role in various cancers; however, these have not been distinguished in PanNETs. To investigate the expression and clinical significance of programmed death ligand-1 (PD-L1), programmed death ligand-2 (PD-L2), B7 homolog 3 (B7-H3), B7 homolog 4 (B7-H4), and V-domain immunoglobulin suppressor of T-cell activation (VISTA) in 182 PanNETs (with a high proportion of functioning versus nonfunctioning PanNETs: 51% versus 49%). Molecules were immunostained by using tissue microarrays from 182 patients with grade 1/2 PanNETs. VISTA-positive microvessel density (VISTA+ MVD) was evaluated in 4 high-power fields (HPFs) (×200) and mean count was calculated; immune cells with 1% or greater VISTA staining were considered positive. PD-L1 tumoral expression was considered positive in samples with 5% or more membranous staining. Tumoral VISTA, stromal PD-L1, PD-L2, B7-H3, and B7-H4 expression were deemed positive if any staining was observed. VISTA+ MVD was high (≥10.8/HPF) in 45 patients (25%), while VISTA stained positively on immune and tumor cells in 121 (66%) and 0 patients, respectively. Positive PD-L1 tumoral and stromal expression was observed in 23 (13%) and 0 patients, with positive B7-H3 expression in 76 (42%) and 98 (54%) patients, respectively, in these cells; PD-L2 and B7-H4 were not detected. PD-L1 positivity rate was high in functioning PanNETs. Stromal B7-H3 and high VISTA+ MVD correlated with unfavorable clinicopathologic features. Moreover, high VISTA+ MVD was an independent predictor of shorter progression-free survival. VISTA may serve as a prognosticator and immunotherapeutic target for patients with pancreatic neuroendocrine tumor (PanNET).

Macrophage Differentiation and Polarization Regulate the Release of the Immune Checkpoint Protein V-Domain Ig Suppressor of T Cell Activation.

Recently, the V-domain immunoglobulin suppressor of T-cell activation (VISTA) was identified as a negative immune checkpoint regulator (NCR) that is mainly expressed in hematopoietic cells. Preclinical studies have shown that VISTA blockade results in impeded tumor growth and improved survival. Nevertheless, little is known about the physiological role of VISTA expression in macrophages. This study focused on the differential expression of VISTA in human monocytes and macrophages in order to elucidate a putative role of VISTA regulation upon macrophage polarization and activation. We observed that human peripheral monocytes constitutively release soluble VISTA, which was regulated via matrix metalloproteinases. However, monocyte stimulation with cytokines that induce macrophage differentiation, such as granulocyte-macrophage colony–stimulating (GM-CSF) and macrophage colony-stimulating factor (M-CSF), substantially reduced soluble VISTA release. VISTA release was further affected by various pro- and anti-inflammatory stimuli that led to macrophage polarization, where activated M1 macrophages generally released more VISTA than M2 macrophages. Additionally, we observed that stimulation of activated macrophages with the toll-like receptor 4 ligand lipopolysaccharide (LPS) led to a further decrease of soluble VISTA release. Moreover, we found that soluble VISTA impairs T cell cytotoxic activity but did not induce their programmed death. Our results suggest that VISTA is constantly produced and released in the peripheral blood where it may contribute to peripheral tolerance.