Programmed Death Receptor-1 Blockade Research Articles

Combination therapy with hydrogen peroxide and irradiation promotes an abscopal effect in mouse models.

Hydrogen peroxide (H2 O2 ) induces oxidative stress and cytotoxicity, and can be used for treating cancers in combination with radiotherapy. A product comprising H2 O2 and sodium hyaluronate has been developed as a radiosensitizer. However, the effects of H2 O2 on antitumor immunity remain unclear. To investigate the effects of H2 O2 , especially the abscopal effect when combined with radiotherapy (RT), we implanted murine tumor cells simultaneously in two locations in mouse models: the hind limb and back. H2 O2 mixed with sodium hyaluronate was injected intratumorally, followed by irradiation only at the hind limb lesion. No treatment was administered to the back lesion. The H2 O2 /RT combination significantly reduced tumor growth at the noninjected/nonirradiated site in the back lesion, whereas H2 O2 or RT individually did not reduce tumor growth. Flow cytometric analyses of the tumor-draining lymph nodes in the injected/irradiated areas showed that the number of dendritic cells increased significantly with maturation in the H2 O2 /RT combination group. In addition, analyses of tumor-infiltrating lymphocytes showed that the number of CD8+ (cluster of differentiation 8) T cells and the frequency of IFN-γ+ (interferon gamma) CD8+ T cells were higher in the noninjected/nonirradiated tumors in the H2 O2 /RT group compared to those in the other groups. PD-1 (programmed death receptor 1)blockade further increased the antitumor effect against noninjected/nonirradiated tumors in the H2 O2 /RT group. Intratumoral injection of H2 O2 combined with RT therefore induces an abscopal effect by activating antitumor immunity, which can be further enhanced by PD-1 blockade. These findings promote the development of H2 O2 /RT therapy combined with cancer immunotherapies, even for advanced cancers.

PD1 blockade alters cell-cycle distribution and affects 3'-deoxy-3'-[18F]fluorothymidine uptake in a mouse CT26 tumor model.

We previously reported that alterations of the tumor microenvironment (TME) by programmed death receptor-1 (PD1) blockade affected tumor glucose metabolism and tumor 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) uptake. In cancer cells, high glycolysis allows cells to sustain rapid proliferation since glycolysis is closely related to the proliferation of cancer cells. Therefore, imaging of cellular proliferation may provide more detail of TME alterations. In this study, we investigated how TME alterations by PD1 blockade affects the uptake of 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT), which is a 18F-radiolabeled thymidine derivative and is taken up by proliferating cells. Mice inoculated with murine colon carcinoma CT26 cells were intraperitoneally administered an anti-PD1 antibody on Day 0, when the tumor volume exceeded 50 mm3, and Day 5. [18F]FLT-PET imaging was performed pre-treatment (Day 0) and post treatment (Day 7). Tumor infiltrating lymphocytes (TILs) were identified by flow cytometry. [18F]FLT accumulation and localization in tumor tissue was evaluated by autoradiography and immunohistochemistry. The cell-cycle distribution of tumors and CT26 cells exposed to cytokines (interleukin-2, interferon [INF]-γ, and tumor necrosis factor [TNF]-α) was analyzed by flow cytometry. PD1 blockade increased CD8+ and CD4+ T cells in tumor tissue and significantly suppressed tumor proliferation; however, tumor [18F]FLT uptake remained unchanged. Autoradiography and immunohistochemistry showed that [18F]FLT was mainly taken up by cancer cells, but not TILs. Flow cytometric analysis demonstrated that the population of cells in G2/M phase increased after PD1 blockade. Moreover, INF-γ and TNF-α significantly increased cells in G2/M phase in vitro. PD1 blockade-induced alteration of the TME increased CT26 tumor cells in the G2/M phase, which have high thymidine kinase 1 activity. Therefore, [18F]FLT is taken up by tumor cells even if tumor proliferation is suppressed. This observation may be useful for evaluating the response to immunotherapy.

Abstract 615: Tim-3 as an immune therapy target, mechanism and action, and prognostic values with its ligands in patient stratification

Abstract BACKGROUND: Immune checkpoint inhibitors (ICIs) have revolutionized the cancer therapy landscape in recent years. Despite the success of the checkpoint blockade strategies targeting cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed death receptor 1 (PD-1), many cancer patients cannot benefit from these therapies. T cell immunoglobulin and mucin domain 3 (TIM-3) has emerged as one of the next generation ICI targets, with potentially lower toxicity and higher safety compared to CTLA-4 and PD-1 blockades. TIM-3 is widely expressed in different immune lineages playing various roles such as mediating immune tolerance and regulating innate immune response. However, the mechanism of action of TIM-3 inhibition in different malignancies is not completely understood. Whether the expression and genomic status of TIM-3 and its ligands, Ceacam-1, galectin-9, HMGB1 and phosphatidyl serine (PtdSer) are associated with clinical outcome or any indication would be essential for patient selection for TIM-3 targeting therapies. METHODS: Human PD-1/TIM-3 double-knock-in mice (PD-1/TIM-3 dKI HuGEMM™) engrafted with CT26.WT tumor model were used to test human PD-1 antibody (Keytruda) and TIM-3 antibody (MBG453). Immune phenotyping of blood, tumor draining lymph node (TDLN) and spleen tissues were assessed by flow cytometry at different time points after dosing. Cytokine levels in serum were measured by MSD assays at 48 hours post the 3rd dose and at study termination. Patient genomic and clinical data for various cancer types such as colorectal adenocarcinoma and pancreatic adenocarcinoma were collected for prognostic biomarker analysis. RESULTS: In the in vivo efficacy study of single and combination treatment with Keytruda and MBG453, we observed that NK cells were induced by anti-TIM-3 treatment, alone and in combination, in both blood and TDLN. This indicates TIM-3 blockade may lead to NK cell proliferation in the TME to enhance tumor killing. Transcriptomic analysis on thousands of patients from TCGA showed that high expression of TIM-3 was highly associated with MSI-H and MSI/CIMP subtypes of colorectal adenocarcinoma, suggesting the potential of Tim-3 target therapy in combination with PD-1 blockade in colorectal cancers. By survival analysis, we observe that one of the TIM-3 ligands, HMGB1, expression is associated with patient OS and PFS with pancreatic adenocarcinoma, but not in colorectal cancers. Furthermore, TIM-3 expression was associated with many immune cell signatures, including macrophages, dendritic cells, CD8+ memory T cells, CD4+ memory T cells and Tregs in both colorectal and pancreatic adenocarcinoma. CONCLUSIONS: Evaluation in preclinical model demonstrated that TIM-3 blockade may cause NK cell proliferation to enhance anti-tumor immunity. In addition, the expression and genomic alteration of TIM-3 and its ligand have prognostic values for certain cancers. Citation Format: Jia Xue, Yu Zhang, Xianfei He, Henry Q. Li, Sheng Guo. Tim-3 as an immune therapy target, mechanism and action, and prognostic values with its ligands in patient stratification [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 615.

Suppression of the transforming growth factor-β signaling pathway produces a synergistic effect of combination therapy with programmed death receptor 1 blockade and radiofrequency ablation against hepatic carcinoma in mice

ABSTRACT Primary liver cancer (PLC) significantly affects the health of patients globally owing to its high morbidity and low survival rate. Radiofrequency ablation (RFA) has recently been introduced for the clinical treatment of PLC. However, significant immunosuppressive effects are induced by RFA, which limits its application. This study aimed to explore the potential of combination therapy with RFA by investigating the effects of siRNAs against programmed death receptor 1 (PD-1) and transforming growth factor-β (TGF-β) on the antitumor effect induced by RFA. We observed that compared with si-NC, cell viability was reduced, apoptosis rate was elevated, release of inflammatory factors and percentage of CD3+CD8+ cells were increased, and the PI3K/AKT/mTOR pathway was repressed in the co-culture of RFA-treated H22 cells and CD8+ T cells by transfection with si-PD-1 and si-TGF-β; these effects were further enhanced by co-transfection with si-PD-1 and si-TGF-β. Additionally, in H22 cell xenograft-bearing mice treated with RFA, compared with the si-NC group, repressed tumor growth, prolonged survival, increased production of inflammatory factors and expression of CD3 and CD8 in tumor tissues, and downregulation of the PI3K/AKT/mTOR pathway were observed in the si-PD-1 and si-TGF-β groups; these effects were further enhanced in the si-PD-1 + si-TGF-β group. Taken together, our data revealed that suppression of the TGF-β signaling pathway produced a synergistic antitumor effect of combination therapy with PD-1 blockade and RFA against PLC.

Effect of fruquintinib on programmed death receptor-1 blockade antitumor immune responses in colorectal cancer.

150 Background: Programmed death receptor-1 (PD-1) blockade shows little benefit in the patients with microsatellite-stable colorectal cancer (MSS-CRC).Fruquintinib, a China-made anti-angiogenic drug, applied for third line therapy in mCRC. However, the effects of combination of fruquintinib and PD-1 blockade on MSS-CRC and its relative mechanisms are not well determined. Methods: Syngeneic xenograft mouse models were establish using murine MC38 and CT26 colon cancer cells to assess treatment efficacy. The percentages of immune cells were detected in peripheral blood, spleen and tumor tissues in tumor-bearing mice by flow cytometry analysis. Angiogenesis in tumor tissues was detected by immunofluorescence. The safety of drug treatment was evaluated by histopathology analysis in murine main organs. The efficacy of combination of fruquintinib and sintilimab were verified in the treatment of MSS-CRC patients. Results: Our results showed the combination of fruquintinib and sintilimab exhibited strongest inhibition of tumor growth and achieved longest survival time in mice bearing MC38 or CT26 xenograft tumors, compared to fruquintinib and sintilimab alone. Mechanistically, the combination of fruquintinib and sintilimab reduced angiogenesis, reprogramed the vascular structure, enhanced the infiltration of CD8+T cells, CD8+TNFα+T cells and CD8+IFNγ+T cells and reduced the ratios of MDSCs and macrophages in mice. No obvious damage was observed in main organs in tumor-bearing mice with the combined treatment. Moreover, the treatment of combination of fruquintinib and sintilimab anti-PD-1 antibodies achieved effective response in five refractory advanced MSS CRC patients. Conclusions: Our results show that combination of fruquintinib and sintilimab synergistically inhibits CRC growth by alterating antitumor immune microenvironment.

Immunohistochemical expression of programmed death-ligand 1 and CD8 in glioblastomas

BackgroundGlioblastoma is the most aggressive primary malignant brain tumor in adults and is characterized by poor prognosis. Immune evasion occurs via programmed death-ligand 1 (PD-L1)/programmed death receptor 1 (PD-1) interaction. Some malignant tumors have responded to PD-L1/PD-1 blockade treatment strategies, and PD-L1 has been described as a potential predictive biomarker. This study discussed the expression of PD-L1 and CD8 in glioblastomas.MethodsThirty cases of glioblastoma were stained immunohistochemically for PD-L1 and CD8, where PD-L1 expression in glioblastoma tumor tissue above 1% is considered positive and CD-8 is expressed in tumor infiltrating lymphocytes. The expression of each marker was correlated with clinicopathologic parameters. Survival analysis was conducted to correlate progression-free survival (PFS) and overall survival (OS) with PD-L1 and CD8 expression.ResultsDiffuse/fibrillary PD-L1 was expressed in all cases (mean expression, 57.6%), whereas membranous PD-L1 was expressed in six of 30 cases. CD8-positive tumor-infiltrating lymphocytes (CD8+ TILs) had a median expression of 10%. PD-L1 and CD8 were positively correlated (p = .001). High PD-L1 expression was associated with worse PFS and OS (p = .026 and p = .001, respectively). Correlation of CD8+ TILs percentage with age, sex, tumor site, laterality, and outcomes were statistically insignificant. Multivariate analysis revealed that PD-L1 was the only independent factor that affected prognosis.ConclusionsPD-L1 expression in patients with glioblastoma is robust; higher PD-L1 expression is associated with lower CD8+ TIL expression and worse prognosis.

Immune Checkpoint Inhibitors Regulate K+ Channel Activity in Cytotoxic T Lymphocytes of Head and Neck Cancer Patients.

Programmed death receptor-1 (PD-1) and its ligand (PD-L1) interaction negatively regulates T cell function in head and neck squamous cell carcinoma (HNSCC). Overexpression of PD-1 reduces intracellular Ca2+ fluxes, and thereby T cell effector functions. In HNSCC patients, PD-1 blockade increases KCa3.1 and Kv1.3 activity along with Ca2+ signaling and mobility in CD8+ peripheral blood T cells (PBTs). The mechanism by which PD-L1/PD-1 interaction regulates ion channel function is not known. We investigated the effects of blocking PD-1 and PD-L1 on ion channel functions and intracellular Ca2+ signaling in CD8+ PBTs of HNSCC patients and healthy donors (HDs) using single-cell electrophysiology and live microscopy. Anti-PD-1 and anti-PD-L1 antibodies increase KCa3.1 and Kv1.3 function in CD8+ PBTs of HNSCC patients. Anti-PD-1 treatment increases Ca2+ fluxes in a subset of HSNCC patients. In CD8+ PBTs of HDs, exposure to PD-L1 reduces KCa3.1 activity and Ca2+ signaling, which were restored by anti-PD-1 treatment. The PD-L1-induced inhibition of KCa3.1 channels was rescued by the intracellular application of the PI3 kinase modulator phosphatidylinositol 3-phosphate (PI3P) in patch-clamp experiments. In HNSCC CD8+ PBTs, anti-PD-1 treatment did not affect the expression of KCa3.1, Kv1.3, Ca2+ release activated Ca2+ (CRAC) channels, and markers of cell activation (CD69) and exhaustion (LAG-3 and TIM-3). Our data show that immune checkpoint blockade improves T cell function by increasing KCa3.1 and Kv1.3 channel activity in HNSCC patients.

Abstract 1671: Evaluation of total PD-1 expression using multi-color flow cytometry in metastatic non-small Cell lung cancer patients treated with multi-neoantigen vector (ADXS-503) alone and in combination of pembrolizumab to assess T-cell & T-cell memory subsets

Abstract Precision for Medicine (Precision) developed and qualified two 17 color flow immunophenotyping assays to be used as pharmacodynamic biomarkers for Advaxis clinical studies in patients with Metastatic Non-Small Cell Lung Cancer treated with ADXS-503 alone and in combination with Pembrolizumab (Pembro). ADXS-503 (A503) is an off-the-shelf, attenuated Listeria monocytogenes (Lm)-based immunotherapy bioengineered to elicit potent T-cell responses against 22 tumor antigens commonly found in NSCLC. Pembrolizumab (Pembro) is a programmed death receptor-1 (PD-1)-blocking antibody approved for the treatment of advanced lung cancer. A503 and Pembro have complementary mechanisms of immune activation and reversal of immune tolerance. Here, we qualified two multi-color flow cytometry assays to quantify total PD-1 expression in cryopreserved peripheral blood mononuclear cells (PBMCs) from individuals that were treated either with A503 only or with A503 in combination with Pembro. The detection of free PD-1 and Pembro-bound PD-1 was achieved by co-staining a partially competing αPD-1 antibody (clone PD1.3.1.3) with a biotinylated αHu-IgG4 antibody. The robustness of the assay was demonstrated using a nine-point half-log serial dilution of Pembro, where the highest concentration was 10µg/mL and the lowest concentration was 0.001µg/mL, including a no drug control. The assay conditions were optimized for sensitivity, optimal signal:noise ratio, detection of free and drug bound receptor by titrating and testing various commercial αPD-1 antibody clones and tertiary reagents to detect biotinylated αHu-IgG4. The Pembro bound receptor was detected using a biotinylated αHu-IgG4 antibody, while the free receptors were quantified using a commercial αPD-1 antibody. The assay was able to quantify free and drug bound PD-1 in the intended immune cell types without compromising the staining of other cell surface and intra-nuclear markers. Majority of the evaluable patients, 6 out of 8, had increased counts of NK, CD4+ and CD8+ T-cells, including TCM, TEM and memory stem cells after the administration of ADXS-503 ± Pembro. PD1 expression on circulating CD4+, CD8+ and NK T-cells was also increased while PD-L1 expression was elevated in on-therapy tumor biopsies in some of these patients. Measuring total PD-1 in T-cells can be more challenging in patients on Pembrolizumab therapy as no known commercial non-competing αPD-1 antibody clones are available. This novel assay will facilitate the evaluation of total PD-1 expression as a pharmacodynamic biomarker in T-cells when PD-1 blockade is being used. These results also support that combination of ADXS-503 with PD-1 blockade could lead to enhancement of efficacy of anti-tumor immunotherapy. Citation Format: Venkat Mohanram, Natalya Belkina, Angelina R. Bisconte, Jonathan W. Goldman, Gregory J. Gerstner, Missak Haigentz, Thomas Stinchcombe, Balazs Halmos, Surya Vangala, Victor Kabala, Dinesh Simkhada, Cristiane Metran, Darren Davis, Megan Parsi, Andres A. Gutierrez, Deborah Phippard, Suresh S. Ramalingam. Evaluation of total PD-1 expression using multi-color flow cytometry in metastatic non-small Cell lung cancer patients treated with multi-neoantigen vector (ADXS-503) alone and in combination of pembrolizumab to assess T-cell & T-cell memory subsets [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1671.

IMMU-26. DISEASE CONTROL IN A PEDIATRIC PATIENT WITH NEWLY DIAGNOSED GLIOBLASTOMA MULTIFORME (GBM) AND SOMATIC HIGH MICROSATELLITE INSTABILITY (MSI-H) WITH PD-1 INHIBITOR NIVOLUMAB (NIVO) ONLY AND NO FOCAL RADIOTHERAPY (RT)

Immune checkpoint inhibitors that target programmed death receptor-1 (PD-1) have recently been shown to be a promising option for the management of recurrent mismatch repair (MMR) deficient GBM following radiotherapy. We report a case of a 9-year-old boy who presented with a 6 week history of frontal headaches and was found to have a left frontal lobe mass. Pathology obtained from a gross total resection (GTR) was consistent with classic GBM, WHO Grade IV. Neuroimaging four weeks following initial resection was remarkable for local recurrence. The patient underwent another GTR of the tumor at our center. While pathology again confirmed GBM, GlioSequencing of tumor tissue from second resection showed MSI-H, NF2 mutation p.R338H, NF1 mutations p.R2450* and pI193Yfs*11, TP53 mutations p.R213* and p.R273C, EGFR mutation, and multiple variants of uncertain significance. Germline testing was negative for MMR deficiency or other deleterious mutations. Parents opted to defer radiotherapy and consented to monotherapy treatment with Nivolumab (Opdivo, BMS pharmaceuticals, USA), a PD-1 inhibitor, at a dose of 3 mg/kg administered every two weeks. Our patient is now 22 months post-second resection and continues to receive Nivolumab without evidence of recurrent disease or adverse autoimmune effects from PD-1 blockade. He has remained in school with good academic performance and has exhibited no regression of functional status during the entirety of his treatment course. This case provides evidence of possible efficacy of PD-1 blockade without focal radiotherapy in this child with GBM and somatic MSI instability.

Can Personalized Neoantigens Raise the T Cell Bar?

Ott etal. report the results of a phase 1B study in which a personalized neoantigen vaccine was combined with programmed death receptor-1 blockade in patients with advanced cancers. The study provides a framework for combinatorial vaccine therapies that could mount robust Tcell responses, enhance tumor killing, and provide clinical benefit.

Abstract B89: Dual PD-1 and VEGFR-2 blockade induces vascular normalization and enhances antitumor immune responses in hepatocellular carcinoma

Abstract Introduction: Only a fraction of hepatocellular carcinoma (HCC) patients benefit from programmed death receptor-1 (PD-1) blockade. Combining PD-1 blockade with antiangiogenic treatments has been able to substantially increase the fraction of responsive HCC patients, but the mechanism of this interaction is unknown. We recapitulated these clinical outcomes (response vs. resistance) using orthotopic murine models of HCC. VEGFR2 blockade significantly delayed primary tumor growth but failed to prolong survival, while anti-PD-1 monotherapy conferred a minor survival. However, dual anti-PD-1/VEGFR-2 therapy significantly inhibited primary tumor growth and doubled survival in multiple models. Combination therapy reprogrammed the immune microenvironment by increasing CD8+ cytotoxic T-cell infiltration and activation, improving the ratio of anti- vs. pro-tumor-associated macrophages, and reducing T regulatory cell (Treg) infiltration in HCC tissue. Moreover, we found that VEGFR-2 blockade increased the PD-1 expression in tumor-infiltrating CD4+ cells. Under anti-PD-1 therapy, CD4+ cells promote normalized vessel formation in the face of antiangiogenic therapy. Conclusion: We show that dual anti-PD-1/VEGFR-2 therapy has a durable vessel fortification effect in HCC and can overcome treatment resistance to either treatment alone and increase survival in both anti-PD-1 therapy resistant and responsive HCC models. Citation Format: Meenal Datta, Kohei Shigeta, Tai Hato, Shuji Kitihara, Ivy X. Chen, Aya Matsui, Hiroto Kikuchi, Emilie Mamessier, Shuichi Aoki, Rakesh R. Ramjiawan, Hiroki Ochiai, Nabeel Bardeesy, Peigen Huang, Rakesh K. Jain, Mark Cobbold, Andrew X. Zhu, Dan G. Duda. Dual PD-1 and VEGFR-2 blockade induces vascular normalization and enhances antitumor immune responses in hepatocellular carcinoma [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B89.

Increased Tim-3 expression on TILs during treatment with the Anchored GM-CSF vaccine and anti-PD-1 antibodies is inversely correlated with response in prostate cancer.

Programmed death receptor-1 (PD-1) and T cell immunoglobulin and mucin domain-containing protein-3 (Tim-3) play important roles in tumor immune evasion. PD-1 blockade could produce an effective antitumor effect in many solid tumors except prostate cancer (PCa) because of rare programmed death ligand-1 (PD-L1) expression on PCa cells. Streptavidin (SA)-GM-CSF surface-anchored tumor cell (Anchored GM-CSF) vaccines could increase the number of tumor-infiltrating lymphocytes (TILs) and induce specific antitumor immune responses. The Anchored-GM-CSF vaccine and anti-PD-1 antibodies exerted synergistic effects in mouse models of PCa metastasis. However, the response rate was low due to the presence of other negative regulatory pathways. Tim-3 expression could be upregulated at resistance to combination therapy with anti-PD-1 antibodies and the Anchored GM-CSF vaccine. Sequential administration of anti-PD-1 and anti-Tim-3 antibodies could further improve the efficacy of the Anchored GM-CSF vaccine therapy, and tumor regression was noted in over 60% of animals. This triple therapy improved the specific cytotoxic activity, proliferation and secretion of CD8+ TILs and reduced the production of tumor-promoting cytokines. These findings indicated that this triple therapy could induce a robust antitumor immune response in mouse models of PCa.

Abstract A58: Notch signaling is a key regulator for immune-suppressive function of tumor-associated macrophages in pancreatic adenocarcinoma

Abstract Objective: Pancreatic ductal adenocarcinoma (PDA) has the most dismal prognosis among all human cancers. The poor survival rate has been attributed to high rate of metastasis and low efficacy of current therapies, which may result from the complex immunosuppressive tumor microenvironment. We explored the role of Notch signaling, a key regulator of immune responses, within the PDA microenvironment. Our goal is to better define these immunosuppressive pathways and to develop effective therapies for patients with PDA. Methods: Two primary mouse PDA cell lines (7940B and mT3-2D) were used for implantation into the pancreata of transgenic CBF:H2B-Venus mice; this enabled single-cell reporting of Notch signaling within the PDA microenvironment. Flow cytometry was used to assess Venus expression in different cell populations. In addition, tumor-associated macrophages (TAMs) were sorted by Notch activity [Venus (+) vs. Venus (-)] to analyze expression of Notch targets and macrophage polarization markers by qPCR. Next, a bone marrow-derived macrophage (BMDM) culture system was developed to investigate Notch activation in vitro. Lastly, we evaluated the therapeutic effect of Notch pathway inhibition as monotherapy and in combination with immune checkpoint programmed death receptor-1 (PD-1) blockade in an orthotopic PDA model. Results: Flow cytometry revealed that TAMs were the most abundant immune cell population in the orthotopic PDA microenvironment. About 50% of TAMs were Venus (+), which had significant enrichment in M2 polarization markers such as Arginase 1 (Arg1) and Notch targets (such as Hes1) when compared to Venus (-) TAMs by qPCR. Immunofluorescence showed co-localization of Venus and Hes1 in F4/80+ TAMs. In vitro experiments identified that Notch activation was only present in BMDMs from Venus mice when co-cultured directly with 7940B PDA cells and that Arg1 expression was only found in Venus (+) macrophages. Notch inhibitor LY3039478 led to decreased expression of both M2 polarization markers such as Arg1, Mrc1, Ym1, and immunosuppressive cytokine TGFβ in co-cultured BMDM. In the orthotopic PDA mouse model, neither LY3039478 nor anti-PD1 was effective in treating PDA in vivo, whereas combined inhibition of the Notch pathway and immune checkpoint resulted in significant reduction in tumor growth. Conclusion: Our data demonstrate that Notch activation within TAMs from murine PDAs is associated with an immunosuppressive (M2-like) phenotype, thereby suggesting that Notch signaling plays a role in macrophage polarization within the PDA microenvironment. While pharmacologic inhibition of the Notch pathway was ineffective in treating orthotopic murine PDA in vivo, the combination of Notch inhibition with PD-1 blockade resulted in a therapeutic effect. Targeting the Notch signaling pathway may lessen the immunosuppressive phenotype of TAMs within the PDA microenvironment and improve the efficacy of immune-based therapies for patients with PDA. Citation Format: Wei Yan, Yaqing Zhang, Rosa Menjivar, Filip Bednar, Marina Pasca di Magliano, William Reece Burns. Notch signaling is a key regulator for immune-suppressive function of tumor-associated macrophages in pancreatic adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr A58.

Dual Programmed Death Receptor-1 and Vascular Endothelial Growth Factor Receptor-2 Blockade Promotes Vascular Normalization and Enhances Antitumor Immune Responses in Hepatocellular Carcinoma.

Activation of the antitumor immune response using programmed death receptor-1 (PD-1) blockade showed benefit only in a fraction of patients with hepatocellular carcinoma (HCC). Combining PD-1 blockade with antiangiogenesis has shown promise in substantially increasing the fraction of patients with HCC who respond to treatment, but the mechanism of this interaction is unknown. We recapitulated these clinical outcomes using orthotopic-grafted or induced-murine models of HCC. Specific blockade of vascular endothelial receptor 2 (VEGFR-2) using a murine antibody significantly delayed primary tumor growth but failed to prolong survival, while anti-PD-1 antibody treatment alone conferred a minor survival advantage in one model. However, dual anti-PD-1/VEGFR-2 therapy significantly inhibited primary tumor growth and doubled survival in both models. Combination therapy reprogrammed the immune microenvironment by increasing cluster of differentiation 8-positive (CD8+ ) cytotoxic T cell infiltration and activation, shifting the M1/M2 ratio of tumor-associated macrophages and reducing T regulatory cell (Treg) and chemokine (C-C motif) receptor 2-positive monocyte infiltration in HCC tissue. In these models, VEGFR-2 was selectively expressed in tumor endothelial cells. Using spheroid cultures of HCC tissue, we found that PD-ligand 1 expression in HCC cells was induced in a paracrine manner upon anti-VEGFR-2 blockade in endothelial cells in part through interferon-gamma expression. Moreover, we found that VEGFR-2 blockade increased PD-1 expression in tumor-infiltrating CD4+ cells. We also found that under anti-PD-1 therapy, CD4+ cells promote normalized vessel formation in the face of antiangiogenic therapy with anti-VEGFR-2 antibody. We show that dual anti-PD-1/VEGFR-2 therapy has a durable vessel fortification effect in HCC and can overcome treatment resistance to either treatment alone and increase overall survival in both anti-PD-1 therapy-resistant and anti-PD-1 therapy-responsive HCC models.

PD1 blockade modulates Ca2+ fluxes in T cells of head and neck cancer patients

Abstract Immunotherapy offers promising results in head and neck cancer (HNC) albeit it faces the problem of high resistance. PD1 (programmed death receptor-1) and its ligand (PD-L1/PD-L2) interaction reduces T cell receptor (TCR)-stimulated Ca2+ fluxes. Ion channels regulate Ca2+ entry in T cells downstream to the TCR (store-operated Ca2+ entry, SOCE). We hypothesized that anti-PD1 antibody (Pembrolizumab, Pembro) increases SOCE. We studied the effect of Pembro and PD-L1 on SOCE in CD8+ peripheral blood T cells (PBTs) of HNC patients and healthy donors (HD) using Thapsigargin (TG). Additionally, we tested the effect of Pembro on KCa3.1, Kv1.3 and Ca2+ release activated Ca2+ (CRAC) channels in PBTs of HNC patients using patch-clamp electrophysiology. TCR-mediated Ca2+ fluxes were assessed in PD1-expressing NFAT-reporter Jurkat cells. In these cells, Pembro increased the number of cells that responded to TCR stimulation with a sustained increase in Ca2+ (30%, p<0.001). Pembro increased SOCE by 55% (p<0.02) in PBTs of a subset of HNC patients (5/9). Baseline SOCE (before Pembro) was lower in the HNC PBTs that positively responded to Pembro compared to untreated HD PBTs (p<0.006). PD-L1 decreases the Ca2+ response, which was reversed by Pembro in HD PBTs (p<0.05). Pembro did not alter the expression of ion channels, but significantly increased KCa3.1 and Kv1.3 conductance in a subset of patients (5–6/8) while it increased divalent free (DVF) currents through CRAC channels only in 2/5 patients. These data suggest that Pembro enhances SOCE in T cells by modulating ion channels activity. This mechanism may contribute to the improved functionality of T cells in cancer patients undergoing immunotherapy. (DoD CA160714; 2-R01-CA95286)

Hyperresponsiveness to interferon gamma exposure as a response mechanism to anti-PD-1 therapy in microsatellite instability colorectal cancer.

Colorectal cancer (CRC) with high-level microsatellite instability (MSI-H) tends to be associated with a better response to programmed death receptor-1 (PD-1) blockade than does microsatellite stable CRC. However, emerging evidence makes the use of programmed death ligand-1 (PD-L1) as a biomarker problematic. Here, we sought to characterize the interactions between PD-L1 expression and the response to PD-1 blockade therapy in BALB/c mice with a subcutaneous tumor challenge. We further focused on interferon gamma (IFNγ)-induced PD-L1 expression in an in vitro setting to evaluate the responsiveness to IFNγ exposure and the specific signaling of PD-1 in HCT116 and SW480 cell lines. In this study, enhanced PD-L1 expression increased survival in CT26 cells, and PD-1 blockade increased the CTL profile and apoptotic cells in mice with CRC. Our in vitro findings showed that PD-L1 expression was significantly upregulated by a low-dose IFNγ treatment, and the MSI-H cell line might exhibit hyperresponsiveness to IFNγ exposure partly through the JAK-STAT pathway. These results suggest that intrinsic PD-L1 in cooperation with extrinsic IFNγ exposure in CRC may be more responsive to anti-PD-1 therapy, mainly through the CTL profile in the tumor microenvironment.

Abstract 3825: INCAGN02390, a novel antagonist antibody that targets the co-inhibitory receptor TIM-3

Abstract Unprecedented rates of durable clinical responses have been observed for antibody-based therapeutics targeting immune checkpoint proteins such as cytotoxic T lymphocyte antigen-4 (CTLA-4) or programmed death receptor-1 (PD-1). Nonetheless, a significant number of patients experience de novo resistance or relapse due to adaptive resistance mechanisms. T-cell immunoglobulin and mucin domain containing-3 (TIM-3) is an inhibitory receptor involved in immune tolerance often co-opted by tumors to prevent successful antitumor responses. Accordingly, TIM-3 is frequently expressed on myeloid and so-called exhausted T and NK cells within the tumor microenvironment. Targeting the TIM-3 pathway in preclinical models has provided additional rationale for pharmacologic modulation of this axis in cancer patients. INCAGN02390 is a novel and fully human Fc-engineered IgG1κ antibody developed to antagonize the TIM-3 pathway for the treatment of human malignancies. INCAGN02390 forms a high-affinity interaction with TIM-3, occluding access to the CC'-FG binding cleft and blocking phosphatidylserine binding. In addition, INCAGN02390 elicits rapid receptor internalization, potentially obviating interactions with other described or undescribed ligands. INCAGN02390 also enhances IFN-γ production from T cells undergoing tonic TCR stimulation when combined with PD-1 blockade. Finally, to demonstrate combinatorial potential, we show potent antitumor activity of an anti-mouse TIM-3 antibody in concert with other checkpoint antibodies in vivo. In summary, these data support assessment of INCAGN02390 in patients with advanced or metastatic solid tumors. Citation Format: Jeremy Waight, Priyadarshini Iyer, Ekaterina Breous-Nystrom, Christina Riordan, Mark Findeis, Dennis Underwood, Joseph Connolly, Michele Sanicola-Nadel, Horacio Nastri, Peggy Scherle, Gregory Hollis, Reid Huber, Robert Stein, Mark van Dijk, Nicholas S. Wilson. INCAGN02390, a novel antagonist antibody that targets the co-inhibitory receptor TIM-3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3825.

Abstract 2568: CAR T cells secreting an immune checkpoint blockade scFv have enhanced anti-tumor efficacy

Abstract T cell therapies have had valuable clinical responses in patients with cancer. Chimeric antigen receptor (CAR) T cells are genetically engineered to recognize tumor cells and CAR T cell therapy has had impressive results in the setting of B cell acute lymphoblastic leukemia but has been less effective in treating other types of hematologic and solid tumors. The inhibitory tumor microenvironment (TME), including expression of ligands that bind inhibitory receptors on T cells, e.g. programmed death receptor 1 (PD-1), can dampen CAR T cell responses. To prevent PD-1-mediated dampening of CAR T cell function, we have co-modified CAR T cells to secrete PD-1 blocking single chain variable fragments (scFv). We first designed mouse constructs with which we could investigate the scFv-secreting CAR T cells in the context of a syngeneic immune-competent intact TME. CAR constructs were engineered directed against either human CD19 or MUC-16 (ecto) and an anti-mouse PD-1 scFv. Mouse T cells transduced with these constructs expressed the CAR on the surface and secreted detectable amounts of scFv that bound to mouse PD-1. The scFv-secreting CAR T cells were cytotoxic and produced IFN- γ when co-cultured with PD-L1 expressing tumors in vitro. We utilized a syngeneic mouse model to study scFv secreting CAR T cells in a model with an intact TME. In tumor-bearing mice treated with CAR T cells, scFv-secreting CAR T cells enhanced survival as compared to second generation CAR T cells. The survival benefit achieved with scFv-secreting CAR T cells was comparable to that achieved with systemic infusion of PD-1 blocking antibody, but with localized delivery of PD-1 blockade. Mice treated with scFv-secreting CAR T cells had detectable scFv in vivo in the TME. Lastly, long term surviving mice had detectable CAR T cells in the bone marrow by PCR, demonstrating persistence and suggesting an immunological memory. We next aimed to translate PD-1 blocking scFv CAR T cells to a clinically relevant human model utilizing a novel anti-human PD-1 blocking scFv. Human T cells modified with the CAR constructs express the CAR on the surface and secrete detectable amounts of PD-1 blocking scFv. The scFv binds to human PD-1 and scFv-secreting CAR T cells are cytotoxic to PD-L1 expressing tumors. Expression of PD-1-blocking scFv enhances CAR T cell function against PD- L1 expressing tumors in xenograft models of hematological and solid tumors by enhancing survival in tumor-bearing mice as compared to second generation CAR T cells. Furthermore, scFv-secreting CAR T cells exhibit in vivo bystander T cell enhancement of function, suggesting scFv-secreting CAR T cells can reactivate endogenous TILs in the TME. These data support the novel concept that localized delivery of scFv by CAR T cells can successfully block PD-1 binding to PD-L1 to enhance the overall anti-tumor efficacy of CAR T cell therapy. Citation Format: Sarwish Rafiq, Oladapo Yeku, Hollie Jackson, Terence purdon, Dayenne van Leeuwen, Su Yan, Pei Wang, Jingyi Xiang, Cheng Liu, Venkatraman Seshan, Renier Brentjens. CAR T cells secreting an immune checkpoint blockade scFv have enhanced anti-tumor efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2568.

PD-1 blockade potentially enhances adoptive cytotoxic T cell potency in a human acute myeloid leukaemia animal model

ABSTRACTObjectives: Acute myeloid leukaemia (AML) is a malignant haematological disease that remains difficult to cure. Cytotoxic T cell (CTL) adoptive infusion therapy may be conducive to tumour remission by boosting physical immunity. Furthermore, programmed death receptor-1 (PD-1) blockade immunotherapy has shown tremendous success in many cancer therapies.Method: We attempted to combine these two immunotherapy strategies to intervene in AML by generating AML cellspecific cytotoxic T lymphocytes in vitro and in vivo with an AML cell strain expressing specific antigens.Results: First, we observed that peripheral blood mononuclear cells (PBMCs) could be induced to generate large numbers of CD8+ CTL cells through immune stimulation. In addition, these CD8+ cells could effectively recognize a human AML cell line and exert cytotoxicity. In animal tests, PD-1 blockade combined with CTL infusion could induce significantly more AML tumour reduction than either treatment alone. This synergistic effect was thought to be connected to immune modulation enhancement, as regulatory T cells (Tregs) in the peripheral blood (PB) were found to be suppressed.Conclusions: This finding suggested the potential application of PD-1 blockade in AML. The present work demonstrated an excellent synergistic tumour therapeutic effect of PD-1 blockade and CTL therapy compared with either treatment alone.

Enhancing CAR T Cell Anti-Tumor Efficacy through Secreted Single Chain Variable Fragment (scFv) Immune Checkpoint Blockade

T cell therapies have had valuable clinical responses in patients with cancer. Chimeric antigen receptor (CAR) T cells can be genetically engineered to recognize tumor cells and CAR T cell therapy has shown impressive results in the setting of B cell acute lymphoblastic leukemia but has been less effective in treating other types of hematologic and solid tumors. The inhibitory tumor microenvironment (TME), including expression of ligands that bind inhibitory receptors on T cells, e.g. programmed death receptor 1 (PD-1), can dampen CAR T cell responses. Separately, immune checkpoint blockade therapy involving the disruption of PD-1 and programmed death receptor ligand1 (PD-L1) interaction allows for re-activation of tumor-infiltrating lymphocytes (TIL) to have anti-tumor function. This approach has shown clinical responses in a range of malignancies, but has been less efficacious in poorly immunogenic tumors.To prevent PD-1-mediated dampening of CAR T cell function, we have co-modified CAR T cells to secrete PD-1 blocking single chain variable fragments (scFv). We first designed mouse constructs with which we could investigate the scFv-secreting CAR T cells in the context of a syngeneic immune-competent intact TME. CAR constructs were engineered directed against either human CD19 or MUC-16 (ecto) with mouse signaling domains and a anti-mouse PD-1 scFv. Mouse T cells transduced with these constructs expressed the CAR on the surface and secreted detectable amounts of scFv that bound to mouse PD-1. The scFv-secreting CAR T cells were cytotoxic and produced IFN-g when co-cultured with PD-L1 expressing tumors in vitro . We utilized a syngeneic mouse model to study scFv secreting CAR T cells in a model with an intact TME. In tumor-bearing mice treated with CAR T cells, scFv-secreting CAR T cells enhanced survival as compared to second generation CAR T cells. The survival benefit achieved with scFv-secreting CAR T cells was comparable to that achieved with systemic infusion of PD-1 blocking antibody, but with localized delivery of PD-1 blockade. Mice treated with scFv-secreting CAR T cells had detectable scFv in vivo in the TME. Lastly, long term surviving mice had detectable CAR T cells in the bone marrow by PCR, demonstrating persistence and suggesting an immunological memory.We next aimed to translate PD-1 blocking scFv CAR T cells to a clinically relevant human model utilizing a novel anti-human PD-1 blocking scFv. CAR constructs were engineered with recognition domains directed against human CD19 or MUC-16 (ecto) and human signaling domains. Human T cells modified with the CAR constructs express the CAR on the surface and secrete detectable amounts of PD-1 blocking scFv. The scFv binds to human PD-1 and scFv-secreting CAR T cells are cytotoxic to PD-L1 expressing tumors. Expression of PD-1-blocking scFv enhances CAR T cell function against PD-L1 expressing tumors in xenograft models of hematological and solid tumors by enhancing survival in tumor-bearing mice as compared to second generation CAR T cells. Furthermore, scFv-secreting CAR T cells exhibit in vivo bystander T cell enhancement of function, suggesting scFv-secreting CAR T cells can reactivate endogenous TILs in the TME.These data support the novel concept that localized delivery of scFv by CAR T cells can successfully block PD-1 binding to PD-L1 and work in an autocrine manner to prevent dampening of CAR T cell responses as well as a paracrine manner to activate endogenous tumor infiltrating lymphocytes to enhance the overall anti-tumor efficacy of CAR T cell therapy. DisclosuresCurran:Juno Therapeutics: Research Funding; Novartis: Consultancy. Yan:Eureka Therapeutics Inc: Employment. Wang:Eureka Therapeutics Inc.: Employment, Equity Ownership. Xiang:Eureka Therapeutics Inc.: Employment. Liu:Eureka Therpeutics Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Brentjens:Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.