T-cell Antitumor Activity Research Articles

Glypican-3-Specific CAR T Cells Coexpressing IL15 and IL21 Have Superior Expansion and Antitumor Activity against Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the fourth most common cause of cancer-related death in the world, and curative systemic therapies are lacking. Chimeric antigen receptor (CAR)-expressing T cells induce robust antitumor responses in patients with hematologic malignancies but have limited efficacy in patients with solid tumors, including HCC. IL15 and IL21 promote T-cell expansion, survival, and function and can improve the antitumor properties of T cells. We explored whether transgenic expression of IL15 and/or IL21 enhanced glypican-3-CAR (GPC3-CAR) T cells' antitumor properties against HCC. We previously optimized the costimulation in GPC3-CARs and selected a second-generation GPC3-CAR incorporating a 4-1BB costimulatory endodomain (GBBz) for development. Here, we generated constructs encoding IL15, IL21, or both with GBBz (15.GBBz, 21.GBBz, and 21.15.GBBz, respectively) and examined the ability of transduced T cells to kill, produce effector cytokines, and expand in an antigen-dependent manner. We performed gene-expression and phenotypic analyses of GPC3-CAR T cells and CRISPR-Cas9 knockout of the TCF7 gene. Finally, we measured GPC3-CAR T-cell antitumor activity in murine xenograft models of GPC3+ tumors. The increased proliferation of 21.15.GBBz T cells was at least in part dependent on the upregulation and maintenance of TCF-1 (encoded by TCF7) and associated with a higher percentage of stem cell memory and central memory populations after manufacturing. T cells expressing 21.15.GBBz had superior in vitro and in vivo expansion and persistence, and the most robust antitumor activity in vivo These results provided preclinical evidence to support the clinical evaluation of 21.15.GPC3-CAR T cells in patients with HCC.

Controversy in the Use of CD38 Antibody for Treatment of Myeloma: Is High CD38 Expression Good or Bad?

During a time span of just a few years, the CD38 antibody, daratumumab, has been established as one of the most important new drugs for the treatment of multiple myeloma, both in the relapsed/refractory setting and, more recently, as a first-line treatment. Although much is known about the pleiotropic modes of action of daratumumab, we are still not sure how to use it in an optimal manner. Daratumumab targets CD38 on myeloma cells and a high level of CD38 expression facilitates complement-mediated cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). Since the expression of CD38 by myeloma cells is downregulated during treatment with daratumumab, it may seem reasonable to introduce a wash-out period and retreat with daratumumab at a later time point when CD38 expression has recovered in order to gain the maximum benefit of daratumumab’s capacity to kill myeloma cells by CDC, ADCC and ADCP. In other aspects, CD38 seems to serve as a survival factor for myeloma cells by facilitating protective myeloma cell–stromal-cell interactions, contributing to the formation of nanotubes that transfer mitochondria from the stromal cells to myeloma cells, boosting myeloma cell proliferation and survival and by generation of immunosuppressive adenosine in the bone marrow microenvironment. In addition, continuous exposure to daratumumab may keep immune suppressor cells at a low level, which boosts the anti-tumor activity of T-cells. In fact, one may speculate if in the early phase of treatment of a myeloma patient, the debulking effects of daratumumab achieved by CDC, ADCC and ADCP are more important while at a later stage, reprogramming of the patient’s own immune system and certain metabolic effects may take over and become more essential. This duality may be reflected by what we often observe when we watch the slope of the M-protein from myeloma patients responding to daratumumab: A rapid initial drop followed by a slow decline of the M-protein during several months or even years. Ongoing and future clinical trials will teach us how to use daratumumab in an optimal way.

Correction: Arming an Oncolytic Herpes Simplex Virus Type 1 with a Single-chain Fragment Variable Antibody against PD-1 for Experimental Glioblastoma Therapy

Purpose: Glioblastoma (GBM) is resistant to standard of care. Immune checkpoints inhibitors (such as anti-PD-1 mAbs) efficiently restore antitumor T-cell activity. We engineered a new oncolytic herpes simplex virus (oHSV) expressing a single-chain antibody against PD-1 (scFvPD-1) to evaluate its efficacy in mouse models of GBM. Experimental Design: NG34scFvPD-1 expresses the human GADD34 gene transcriptionally controlled by the Nestin promoter to allow replication in GBM cells and a scFvPD-1 cDNA transcriptionally controlled by the CMV promoter. ELISA assays were performed to detect binding of scFvPD-1 to mouse and human PD-1. In vitro cytotoxicity and replication assays were performed to measure NG34scFvPD-1 oncolysis, and scFvPD-1 expression and secretion were determined. In vivo survival studies using orthotopic mouse GBM models were performed to evaluate the therapeutic potency of NG34scFvPD-1. Results: NG34scFvPD-1–infected GBM cells express and secrete scFvPD-1 that binds mouse PD-1. The introduction of the scFvPD-1 sequence in the viral backbone does not alter the oncolytic properties of NG34scFvPD-1. In situ NG34scFvPD-1 treatment improved the survival with a tail of durable survivorship in 2 syngeneic immunocompetent mouse models of GBM. Mice that survived the first GBM challenge rejected the second challenge of GBM when implanted in the contralateral hemisphere. However, this was not true when athymic mice were employed as the recipients of the second challenge, consistent with the need for an intact immune system to obtain a memory response. Conclusions: NG34scFvPD-1 treatment induces a durable antitumor response in 2 preclinical mouse models of GBM with evidence for antitumor memory.

Systemic β-Adrenergic Receptor Activation Augments the ex vivo Expansion and Anti-Tumor Activity of Vγ9Vδ2 T-Cells.

TCR-gamma delta (γδ) T-cells are considered important players in the graft-vs.-tumor effect following allogeneic hematopoietic cell transplantation (alloHCT) and have emerged as candidates for adoptive transfer immunotherapy in the treatment of both solid and hematological tumors. Systemic β-adrenergic receptor (β-AR) activation has been shown to mobilize TCR-γδ T-cells to the blood, potentially serving as an adjuvant for alloHCT and TCR-γδ T-cell therapy. We investigated if systemic β-AR activation, using acute dynamic exercise as an experimental model, can increase the mobilization, ex vivo expansion, and anti-tumor activity of TCR-γδ T-cells isolated from the blood of healthy humans. We also sought to investigate the β-AR subtypes involved, by administering a preferential β1-AR antagonist (bisoprolol) and a non-preferential β1 + β2-AR antagonist (nadolol) prior to exercise as part of a randomized placebo controlled cross-over experiment. We found that exercise mobilized TCR-γδ cells to blood and augmented their ex vivo expansion by ~182% compared to resting blood when stimulated with IL-2 and ZOL for 14-days. Exercise also increased the proportion of CD56+, NKG2D+/CD62L–, CD158a/b/e+ and NKG2A− cells among the expanded TCR-γδ cells, and increased their cytotoxic activity against several tumor target cells (K562, U266, 221.AEH) in vitro by 40–60%. Blocking NKG2D on TCR-γδ cells in vitro eliminated the augmented cytotoxic effects of exercise against U266 target cells. Furthermore, administering a β1 + β2-AR (nadolol), but not a β1-AR (bisoprolol) antagonist prior to exercise abrogated the exercise-induced enhancement in TCR-γδ T-cell mobilization and ex vivo expansion. Furthermore, nadolol completely abrogated while bisoprolol partially inhibited the exercise-induced increase in the cytotoxic activity of the expanded TCR-γδ T-cells. We conclude that acute systemic β-AR activation in healthy donors markedly augments the mobilization, ex vivo expansion, and anti-tumor activity of TCR-γδ T-cells and that some of these effects are due to β2-AR signaling and phenotypic shifts that promote a dominant activating signal via NKG2D. These findings highlight β-ARs as potential targets to favorably alter the composition of allogeneic peripheral blood stem cell grafts and improve the potency of TCR-γδ T-cell immune cell therapeutics.

Suppression of TGF-β and IL-10 receptors on self-differentiated dendritic cells by short-hairpin RNAs enhanced activation of effector T-cells against cholangiocarcinoma cells

ABSTRACT Cholangiocarcinoma (CCA) is an aggressive tumor that is associated with high rates of recurrence and mortality. This is due, in part, to the fact that CCA cells and their microenvironment secrete immunosuppressive cytokines, transforming growth factor-β (TGF-β) and interleukin-10 (IL-10), that inhibit dendritic cell (DC) functions, which, in turn, results in the decreased anti-tumor activity of T-cells. We hypothesized that the TGF-β receptor and IL-10 blockade on dendritic cells would improve DC function, thereby allowing improved activation of T cells against CCA cells. To test our hypothesis, we generated self-differentiated DCs (SD-DCs) via transduction of human peripheral blood monocytes with lentivirus expressing IL-4 and GM-CSF. SD-DCs were transduced with a second lentivirus containing short-hairpin RNAs (shRNAs) to knock-down TGF-βRII and IL-10RA mRNAs. Immunoblot confirmed the reduced expression levels of TGF-β and IL-10 receptors in both SD-DCs that were transduced with a single and/or combination of lentiviruses containing shRNAs. SD-DCs were thereafter pulsed with tumor antigens extracted from CCA cell lines in an effort to activate DC function. MHC class II (HLA-DR) and co-stimulatory molecules (CD40 and CD86) on SD-DCs were upregulated to levels comparable to those on DCs generated by the conventional method. Suppression of TGF-β and IL-10 receptors on SD-DCs influenced the effector T-cells to produce IFN-γ, which enhanced their ability to kill CCA cells. The preparation of adoptive effector T-cells holds the potential of becoming a novel therapy for cellular immunotherapy in CCA.

Myeloid cell–targeted miR-146a mimic inhibits NF-κB–driven inflammation and leukemia progression in vivo

AbstractNF-κB is a key regulator of inflammation and cancer progression, with an important role in leukemogenesis. Despite its therapeutic potential, targeting NF-κB using pharmacologic inhibitors has proven challenging. Here, we describe a myeloid cell–selective NF-κB inhibitor using an miR-146a mimic oligonucleotide conjugated to a scavenger receptor/Toll-like receptor 9 agonist (C-miR146a). Unlike an unconjugated miR146a, C-miR146a was rapidly internalized and delivered to the cytoplasm of target myeloid cells and leukemic cells. C-miR146a reduced expression of classic miR-146a targets (IRAK1 and TRAF6), thereby blocking activation of NF-κB in target cells. IV injections of C-miR146a mimic to miR-146a–deficient mice prevented excessive NF-κB activation in myeloid cells, and thus alleviated myeloproliferation and mice hypersensitivity to bacterial challenge. Importantly, C-miR146a showed efficacy in dampening severe inflammation in clinically relevant models of chimeric antigen receptor (CAR) T-cell–induced cytokine release syndrome. Systemic administration of C-miR146a oligonucleotide alleviated human monocyte-dependent release of IL-1 and IL-6 in a xenotransplanted B-cell lymphoma model without affecting CD19-specific CAR T-cell antitumor activity. Beyond anti-inflammatory functions, miR-146a is a known tumor suppressor commonly deleted or expressed at reduced levels in human myeloid leukemia. Using The Cancer Genome Atlas acute myeloid leukemia data set, we found an inverse correlation of miR-146a levels with NF-κB–related genes and with patient survival. Correspondingly, C-miR146a induced cytotoxic effects in human MDSL, HL-60, and MV4-11 leukemia cells in vitro. The repeated IV administration of C-miR146a inhibited expression of NF-κB target genes and thereby thwarted progression of disseminated HL-60 leukemia. Our results show the potential of using myeloid cell–targeted miR-146a mimics for the treatment of inflammatory and myeloproliferative disorders.

P095 PD-1 expressing T cells in patients with different types of colitis

Abstract Background Immunotherapy-related colitis is a frequent adverse event in patients with malignancies, treated with inhibitors targeting programmed death-1 (PD-1). This treatment leads to enhancement of lymphocyte activity, thereby generating antitumor T-cell activity. The role of PD-1+ T cells in the pathophysiology of different types of colitis is unclear. Therefore, we aimed to study the presence of PD-1+ T cells in inflammatory bowel disease (IBD), infectious colitis and healthy controls compared with anti-PD-1-related colitis. Methods We performed a prospective cohort study. Newly diagnosed patients with ulcerative colitis (UC, n = 51), Crohn’s disease (CD, n = 29), infectious colitis (n = 4), anti-PD-1-related colitis (n = 5) and healthy controls (n = 6) were included. Baseline colonic biopsy specimens were collected for immunohistochemistry identifying PD-1+ and PD-L1+ lymphocytes in the epithelium and lamina propria separately and for immunophenotyping by flow cytometry identifying PD-1+ T-cell subsets. Results Using immunohistochemistry, PD-1 was not present on lymphocytes in the epithelium of patients with any type of colitis, nor in healthy controls. Of all lymphocytes in the lamina propria, % PD-1 expression was 40% in UC, 5% in infectious colitis, 3% in anti-PD-1-related colitis and 0% in healthy controls. PD-L1 was expressed on lymphocytes in the epithelium and lamina propria of UC patients (12.5% and 40%) and in infectious colitis (1% and 30%), whereas in anti-PD-1-related colitis (0% and 15%) and healthy controls (0% and 15%) no PD-L1+ lymphocytes were demonstrated in the epithelium. Flowcytometry showed higher percentages of PD-1+ T cells in biopsy specimens of UC patients (25.2% (IQR 17.9–35.6)) compared with all other groups; CD patients (13.5% (5.0–25.3), p = 0.001), infectious colitis (9.8% (4.7–17.4), p = 0.005), anti-PD-1-related colitis (1.5% (1.1–2.1), p = 0.001) and healthy controls (14.3% (4.9–28.2), p = 0.08). In IBD and infectious colitis, the majority of PD-1+ T cells were CD4+ (84.8% (76.5–90.5), while in anti-PD-1-related colitis the majority of PD-1+ T cells were CD8+ (76.2% (68.5–82.1)). PD-1+ T cells in all patient groups were mainly effector T cells (CD45Ro+). Conclusion In patients with different types of colitis and in healthy controls, PD-1 was only expressed on T cells in the lamina propria and not in the epithelium. The percentage of PD-1+ T cells was significantly higher in patients with UC compared with patients with CD or infectious colitis and healthy controls. As expected PD-1+ T cells were nearly absent in patients with anti-PD-1-related colitis.

Abstract I12: CD40 immunotherapy for pancreatic cancer

Abstract CD40 is a cell-surface member of the TNF receptor superfamily that upon activation can license dendritic cells (DC) to promote antitumor T-cell activation and re-educate macrophages to destroy tumor stroma. Mechanistically, the combination of chemotherapy followed by CD40 mAb functions as an “in situ” vaccine; in addition, destruction of stroma by CD40-activated macrophages may enhance chemotherapy delivery. In a recent study sponsored by the Parker Institute of Cancer Immunotherapy of gemcitabine and nab-paclitaxel chemotherapy plus CD40 mAb APX005M, with or without PD-1 nivolumab mAb, we found the objective response rate among 30 patients with untreated, metastatic pancreatic cancer was more than 50% in the DLT-evaluable population. 13 patients experienced an AE leading to discontinuation, and 10 patients experienced a treatment-related serious AE. Two DLTs were observed, grade 3 and 4 febrile neutropenia, respectively. A three-arm randomized study of gemcitabine, nab-paclitaxel with APX005M, or with nivolumab, or with both APX005M and nivolumab has completed enrollment. Evidence to date suggests that CD40 activation is a critical and nonredundant mechanism to convert “cold” tumors to “hot” (with prominent tumor infiltration of T cells), sensitizing them to checkpoint inhibition. Citation Format: Robert H. Vonderheide. CD40 immunotherapy for pancreatic cancer [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 I12.

Proceedings From the Clinical and Scientific Innovations in Oral and Maxillofacial Surgery Conference 2019

Proceedings From the Clinical and Scientific Innovations in Oral and Maxillofacial Surgery Conference 2019

Next Generation NKG2D-based CAR T-cells (CYAD-02): Co-expression of a Single shRNA Targeting MICA and MICB Improves Cell Persistence and Anti-Tumor Efficacy in vivo

Background The Natural Killer Group 2D (NKG2D) receptor is a NK cell activating receptor that binds to eight different ligands (NKG2DL) commonly over-expressed in cancer, including MICA and MICB. The product candidate CYAD-01 are chimeric antigen receptor (CAR) T-cells encoding the full length human NKG2D fused to the intracellular domain of CD3ζ. Data from preclinical models have shown that CYAD-01 cells specifically target solid and hematological tumors. Encouraging preliminary results from the Phase I clinical trial THINK, assessing CYAD-01 safety, showed initial signals of objective clinical responses in patients with r/r AML and MDS. The clinical development of CAR T-cells has been limited by several challenges including achieving sufficient numbers of cells for clinical application. We have previously shown that NKG2D ligands are transiently expressed on activated T cells and that robust cell yields are generated through the addition of a blocking antibody and a PI3K inhibitor during cell manufacture. Here, we investigated the ability of an optimized short hairpin RNA (shRNA) technology to modulate NKG2DL expression on CYAD-01 cells and to determine if there is an increase in the anti-tumor activity of NKG2D-based CAR T-cells (termed CYAD-02). Methods Molecular and cellular analyses identified MICA and MICB as the key NKG2DL expressed on activated T-cells and highly likely to participate in driving fratricide. In silico analysis and in vitro screening allowed the identification of a single shRNA targeting the conserved regions of MICA and MICB, thus downregulating both MICA and MICB expression. The selected shRNA was incorporated in the NKG2D-based CAR vector, creating the next-generation NKG2D-based CAR T-cell candidate, CYAD-02. In addition, truncated versions of the NKG2D receptor were generated to explore the mechanisms of action of NKG2D receptor activity in vivo. The in vivo persistence and anti-tumor activity of CYAD-02 cells was evaluated in an aggressive preclinical model of AML. Results Injection of CAR T-cells bearing truncated forms of the NKG2D-CAR in immunosuppressed mice resulted in similar persistence to the control T-cells. In contrast, CYAD-01 cells had reduced persistence, suggesting that the recognition of the NKG2DL by the NKG2D receptor could contribute to this effect. Analysis of cell phenotype upon CAR T-cell activation showed that MICA and MICB were transiently expressed on T-cells during manufacturing. These results collectively suggested that downregulating MICA and MICB expression in CYAD-01 cells could be a mean to increase CAR T-cell persistence in vivo. Candidate shRNA were screened for efficient targeting of both MICA and MICB at the mRNA and protein level. T-cells transduced with a single vector encoding for the NKG2D-based CAR and the selected shRNA targeting MICA and MICB (CYAD-02) demonstrated 3-fold increased expansion during in vitro culture in the absence of the blocking antibody used to increase cell yield during manufacture. When injected into immunosuppressed mice, CYAD-02 cells generated with the Optimab process showed 10-fold higher engraftment one week after injection and potent anti-tumor activity resulting in 2.6-fold increase of mouse survival in an aggressive AML model. Conclusions By using a single vector encoding the NKG2D-based CAR next to a shRNA targeting MICA and MICB and combined with improved cell culture methods, CYAD-02, the next-generation of NKG2D-based CAR T-cells, demonstrated enhanced in vivo persistence and anti-tumor activity. Following FDA acceptance of the IND application, a Phase 1 dose-escalation trial evaluating the safety and clinical activity of CYAD-02 for the treatment of r/r AML and MDS is scheduled to start in early 2020. Disclosures Fontaine: Celyad: Employment. Demoulin:Celyad: Employment. Bornschein:Celyad: Employment. Raitano:Celyad: Employment. Machado:Horizon Discovery: Employment. Moore:Avvinity Therapeutics: Employment, Other: Relationship at the time the work was performed; Horizon Discovery: Employment, Equity Ownership, Other: Relationship at the time the work was performed; Centauri Therapeutics: Consultancy, Other: Current relationship. Sotiropoulou:Celyad: Employment. Gilham:Celyad: Employment.

Safety and Anti-Tumor Activity of CD5 CAR T-Cells in Patients with Relapsed/Refractory T-Cell Malignancies

Safety and Anti-Tumor Activity of CD5 CAR T-Cells in Patients with Relapsed/Refractory T-Cell Malignancies

STING Signaling in Melanoma Cells Shapes Antigenicity and Can Promote Antitumor T-cell Activity.

STING (stimulator of IFN genes) signaling is an innate immune pathway for induction of a spontaneous antitumor T-cell response against certain immunogenic tumors. Although antigen-presenting cells are known to be involved in this process, insight into the participation of tumor cell-intrinsic STING signaling remains weak. In this study, we find diversity in the regulation of STING signaling across a panel of human melanoma cell lines. We show that intact activation of STING signaling in a subset of human melanoma cell lines enhances both their antigenicity and susceptibility to lysis by human melanoma tumor-infiltrating lymphocytes (TIL) through the augmentation of MHC class I expression. Conversely, defects in the STING signaling pathway protect melanoma cells from increased immune recognition by TILs and limit their sensitivity to TIL lysis. Based on these findings, we propose that defects in tumor cell-intrinsic STING signaling can mediate not only tumor immune evasion but also resistance to TIL-based immunotherapies.

1900P - Activated effector T cells co-expressing multiple inhibitory receptors (IRs) are enriched in the tumor immune microenvironment in high grade serous ovarian cancer (HGSOC)

BackgroundIn HGSOC, the positive association between tumor-infiltrating lymphocytes (TILs) and survival suggests that immunotherapy might be beneficial. Despite this, initial attempts had limited efficacy. The pattern of IRs expression displayed by HGSOC TILs has not been fully determined. We characterized the phenotype of TILs in HGSOC to identify immunosuppressive pathways limiting anti-tumor T-cell activity. MethodsPeripheral blood (PB), primary tumor and ascites were retrieved from HGSOC patients admitted for primary surgery in our Institute. Tumor immune infiltrate was characterized on 34 formalin-fixed paraffin-embedded specimens by immunohistochemistry (IHC) for lineage markers (CD20, CD3, CD8, CD4, CD163) and inhibitory molecules (PD-1, PD-L1, LAG-3, TIM-3, VISTA).T cells isolated from tumor, ascites and PB of 14 patients were also characterized by flow cytometry for the expression of lineage and memory markers (CD3, CD4, CD8, CD45RA, CD62L, CD95), inhibitory molecules (PD1, CTLA-4, LAG-3, TIGIT, TIM-3, 2B4, GITR, KLRG1, CD39, CD160) and the activation marker CD137. ResultsThe entity of immune infiltration was heterogeneous: 2/34 of cases (6%) were immune desert; all other cases displayed a wide range of immune cell density, dominated by T lymphocytes and macrophages. B cells were scanty. Intratumoral T cells (ITTCs) were present in 30/34 cases (88.2%), almost constantly CD8. PD-1, LAG-3 and TIM-3 were expressed by 61.9%, 61.7% and 61.7% of ITTCs respectively. VISTA was rarely expressed. PD-L1 was expressed by neoplastic cells and immune cells (mainly macrophages) in 40% and 82.3% of samples, respectively. Flow cytometry confirmed the expression by TILs of several IRs (mainly PD-1, CD39, TIM-3 and LAG-3), with variable percentages of positive cells. Compared with corresponding PB and ascites, TILs were enriched in effector memory lymphocytes and in cells co-expressing PD-1, CD39 and CD137. ConclusionsThese data suggest that HGSOC is infiltrated by antigen-experienced T lymphocytes displaying features of both activation and partial exhaustion. The anti-tumor activity of such cells still needs to be determined. Legal entity responsible for the studyThe authors. FundingAIRC Associazione Italiana Ricerca sul Cancro. DisclosureAll authors have declared no conflicts of interest.

CD8+ T-cells of CLL-bearing mice acquire a transcriptional program of T-cell activation and exhaustion

Chronic lymphocytic leukemia (CLL) is associated with an accumulation of oligoclonal CD8+ effector T-cells, which control leukemia progression in mice, but gradually acquire a dysfunctional phenotype along with disease progression. Exhaustion of CD8+ T-cells is characterized by increased expression of inhibitory receptors like PD-1, decreased proliferation, and reduced effector function such as cytokine production, which reduces anti-tumor control. Despite the accumulation of exhausted PD-1+ CD8+ T-cells in secondary lymphoid organs of CLL patients, immune checkpoint blockade as a means to reinvigorate anti-tumor T-cell activity has not shown the expected efficacy. This highlights the need for a better understanding of T-cell exhaustion in CLL. Here, we uncover the transcriptional program of T-cell exhaustion in CLL by comparing naïve with dysfunctional effector CD8+ T-cells with high PD-1 expression from mice after adoptive transfer of Eµ-TCL1 leukemic cells. Our data provide clear evidence for activation-induced dysfunction of CD8+ T-cells in the CLL microenvironment and assess the heterogeneity in the expression of functionally relevant proteins in specific clusters of CD8+ T-cells at a single-cell level.

Dissecting the Stromal Signaling and Regulation of Myeloid Cells and Memory Effector T Cells in Pancreatic Cancer.

Myeloid cells are a prominent immunosuppressive component within the stroma of pancreatic ductal adenocarcinoma (PDAC). Previously, targeting myeloid cells has had limited success. Here, we sought to target the myeloid cells through modifying a specific stromal component. A murine model of metastatic PDAC treated with an irradiated whole-cell PDAC vaccine and PDAC specimens from patients treated with the same type of vaccine were used to assess the immune-modulating effect of stromal hyaluronan (HA) degradation by PEGPH20. Targeting stroma by degrading HA with PEGPH20 in combination with vaccine decreases CXCL12/CXCR4/CCR7 immunosuppressive signaling axis expression in cancer-associated fibroblasts, myeloid, and CD8+ T cells, respectively. This corresponds with increased CCR7- effector memory T-cell infiltration, an increase in tumor-specific IFNγ, and improved survival. In the stroma of human PDACs treated with the same vaccine, decreased stromal CXCR4 expression significantly correlated with decreased HA and increased cytotoxic activities, suggesting CXCR4 is an important therapeutic target. This study represents the first to dissect signaling cascades following PDAC stroma remodeling via HA depletion, suggesting this not only overcomes a physical barrier for immune cell trafficking, but alters myeloid function leading to downstream selective increases in effector memory T-cell infiltration and antitumor activity.

Abstract 1963: Feasibility and efficacy of using self-delivering RNAi against TGFB1 to reduce TME immunosuppression

Abstract One of the leading causes of non-responding tumors with existing immunotherapies is an immunosuppressive tumor micro-environment (TME). The suppressive nature of the TME is, in part, mediated by immunoregulatory cells (e.g. MDSC cells) and cytokines/chemokines. TGFB1 has recently been shown to be a key suppressive factor responsible for facilitating “cold” or immune-excluded tumors. In these tumors, T cell activity is restricted and by reducing TGFB1 levels we aim to support anti-tumor T cell activity. We evaluated if downregulation of TGFB1 with a self-delivering RNAi (sd-rxRNA) in MDSCs (in vitro) or TME (in vivo) promotes T cell activity and increase anti-tumor activity. sd-rxRNA is a chemically modified RNAi which incorporates drug like properties allowing for self-delivery of RNAi compounds to immune cells (including MDSC, DC, T and NK cells) in the absence of electroporation or formulation in a delivery vehicle. Tumor induced MDSCs were incubated with sd-rxRNA targeting TGFB1, its downstream target COX2 or in combination for 2 days. The cells were washed and added to a co-culture with OT-1 T cells and OVA expressing B16 melanoma. The anti-tumor activity of T-cells was monitored using a Real-Time Cell Activity assay (RTCA). TGFB1 and COX2 downregulated MDSCs had reduced immune-suppressive activity as shown by the enhanced B16-OVA tumor cell killing by CD8 OT-1 T cells in the RTCA assay while the combination of TGFB1 and COX2 MDSCs did not further improve the anti-tumor activity. To evaluate the effect of anti-TGFB1 sd-rxRNA in vivo, we first studied the tumor distribution and TGFB1 downregulation by intratumoral injection of sd-rxRNA to immunocompetent Balbc mice bearing 4T1-RL-GFP breast cancer in a fat pad model. DY547 labeled sd-rxRNA targeting PPIB or unlabeled sd-rxRNA targeting TGFB1 was injected into tumors. Two days later, tumors were resected, and fluorescence signal was analyzed by microscopy and TGFB1 downregulation was evaluated by RT-PCR. Efficient delivery of the DY547 labeled sd-rxRNA was observed in the vast majority of cells as shown by fluorescence microscopy. In addition, fluorescence signal could be detected in tumors up to 28 days after intratumoral injection, suggesting that sd-rxRNA was stable in tumors. Downregulation of TGFB1 in resected tumors, and an increased anti-tumor activity, was seen after three injections of sd-rxRNA. A follow up study was initiated investigating the efficacy of TGFB1 sd-rxRNA in combination with local tumor radiation on anti-tumor and metastatic activities in a 4T1 orthotopic breast cancer model. Preliminary data shows promising results. Our results suggest that sd-rxRNA compounds targeting TGFB1 can enhance the anti-tumor activity of T cells. Local injection of sd-rxRNA into tumors can effectively target TGFB1 in the TME resulting in less immunosuppression and increased anti-tumoral activity. Citation Format: Winnie F. Tam, Dingxue Yan, Melissa Maxwell, James Cardia, Gerrit Dispersyn. Feasibility and efficacy of using self-delivering RNAi against TGFB1 to reduce TME immunosuppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1963.

Abstract 936: Regulation of CD8+ T-cell function and antitumor activity by DGKα and DGKζ

Abstract Diacylglycerol kinases (DGKs) are a family of enzymes that metabolize the lipid diacylglycerol (DAG) to form phosphatidic acid. In T cells, two isoforms of DGK, DGKα and DGKζ, serve an important role in dampening signal transduction downstream of the T cell receptor (TCR), where they phosphorylate DAG generated by PLCγ1 after activation of proximal signaling molecules. DAG generated downstream of TCR binds to Protein Kinase C θ (PKCθ) and Ras Guanyl Releasing Protein 1 (RasGRP1), facilitating T cell activation. Elimination of either DGK isoform leads to increased generation of DAG and subsequent strengthened signaling downstream of RasGRP1 and PKCθ. Functionally, this results in formation of CD8+ T cells with enhanced cytokine production and proliferation after TCR stimulation. While mice or CD8+ T cells deficient in DGKα or DGKζ are both known to demonstrate enhanced immune responses to tumor, there has not been, to date, a direct comparison of the anti-tumor activity between mice lacking the two isoforms. We sought to determine which isoform of DGK more intensely attenuated anti-tumor immunity in order to identify which would be a better target for immune-based cancer therapies. We inoculated C57BL/6 mice with a variety of syngeneic tumor cell lines - MC38 colon carcinoma, B16F1 melanoma, and C1498 leukemia - and directly compared survival and tumor growth between mice deficient in DGKα or DGKζ in the presence or absence of anti-PD1 treatment. We found that DGKζ-/- mice more efficiently suppressed growth of subcutaneously implanted tumor cells when compared with DGKα-/- mice across the three model systems and further observed that the combination of DGKζ-deficiency and anti-PD1 were additive in tumor control. Additionally, relative to wildtype CD8+ T cells, we found that DGKζ-/- CD8+ T cells demonstrated qualitatively enhanced mRNA changes as assessed by RNA-seq analysis of cells after TCR stimulation. Pathway analyses from RNA-seq similarly indicated enhanced quantitative changes in DGKζ-/- T cells relative to DGKα-/- T cells, findings confirmed with in vitro biochemical and functional assays. Lastly, using CRISPR-based approaches to eliminate DGKα or DGKζ, we observed similar biochemical changes in human T cells when compared with T cells from gene-deficient mice. Our data, employing genetic approaches to modulate DGKα or DGKζ in both human and mouse models, suggests that DGKζ is a dominant regulator of TCR driven T cell activation and is consistent with the observed superior anti-tumor immune response. Citation Format: Susan Wee, Junchen Gu, Cindy Wang, Carolyn Cao, Sandra Holzhauer, Heshani Desilva, Erin Wesley, Susan Tsai, Douglas Evans, Matthew Riese. Regulation of CD8+ T-cell function and antitumor activity by DGKα and DGKζ [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 936.

Abstract CT120: A randomized, open-label, open-platform, Phase II study evaluating the efficacy and safety of novel spartalizumab (PDR001) combinations in previously treated unresectable or metastatic melanoma (PLATforM)

Abstract Background: Significant advancements, including development of immune checkpoint inhibitors and targeted therapies, have transformed outcomes in patients (pts) with unresectable or metastatic melanoma. However, pts who do not respond or who progress while receiving these regimens have limited options. Spartalizumab (PDR001) is a high-affinity, humanized monoclonal antibody blocking the programmed cell death 1 (PD-1) receptor. This study is evaluating combinations of spartalizumab with novel compounds to restore antitumor T-cell activity in pts with melanoma progressing after prior PD-1 blockade therapy. Methods: This randomized, open-label, 2-part, multicenter, open-platform, Phase II study (NCT03484923; PLATforM) will evaluate the safety and efficacy of spartalizumab combination treatment in pts with unresectable or metastatic melanoma progressing after prior anti-PD-1/L1 therapy and, if the tumor harbors a BRAF V600 mutation, a BRAF inhibitor. The primary endpoint is objective response rate per RECIST v1.1, with duration of response and assessment of paired tumor biopsies for biomarkers of antitumor T-cell activity as part of the secondary endpoints. Part 1, “selection”, will begin with 3 combination arms: (1) spartalizumab + LAG525 (LAG-3 antibody), (2) spartalizumab + capmatinib (c-MET inhibitor), and (3) spartalizumab + canakinumab (IL-1β antagonist). The PLATforM study will use an adaptive design during the selection part that allows for dropping arms for futility, adding new arms, and selecting 1 or multiple arms for further expansion. Bayesian methodology will be used with specific probability criteria for futility and efficacy assessments at each interim analysis. Pts (≈ 60-85) will be stratified by baseline lactate dehydrogenase level and randomized equally to all open arms during the selection part. Part 2, “expansion”, will further investigate the efficacy and safety of treatment combination(s) selected during part 1. The sample size for part 2 will be adaptive and based on predictive power calculations considering the results from part 1. Previously presented at ESMO 2018, FPN 1304TiP, Weber et al. Reused with permission. Citation Format: Caroline Robert, Reinhard Dummer, Ana Arance, Antoni Ribas, Jeffrey Weber, Georgina V. Long, John Haanen, Paul Nathan, Paolo A. Ascierto, Eduard Gasal, Anthony D'Amelio, Severine Bettinger, Aislyn D. Boran, Dirk Schadendorf. A randomized, open-label, open-platform, Phase II study evaluating the efficacy and safety of novel spartalizumab (PDR001) combinations in previously treated unresectable or metastatic melanoma (PLATforM) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT120.

Abstract CT167: A Phase Ib study to assess safety, tolerability, pharmacokinetics, and preliminary antitumor activity of sitravatinib in combination with tislelizumab in patients with advanced solid tumors

Abstract Background: Sitravatinib is an investigative, orally bioavailable, spectrum-selective receptor tyrosine kinase (RTK) inhibitor with potential antitumor activity that has been shown to potently inhibit split kinase receptors (eg, VEGFR2, KIT) and TAM receptors (eg, AXL, MER). Inhibition of RTKs by sitravatinib may also modulate effects on the tumor microenvironment to overcome resistance to checkpoint inhibitors, including enhanced M1/suppressed M2 macrophage cytokine response, abrogated negative regulation of antitumor NK cell activity, and depleted regulatory T- and myeloid-derived suppressor cells with enhanced antitumor cytotoxic T-cell activity. Tislelizumab is an investigational, humanized IgG4 monoclonal antibody that has been shown to have high affinity and binding specificity for programmed cell death receptor-1 (PD-1). Combining an agent that has both immune modulatory and antitumor properties with an immunotherapeutic PD-1 checkpoint inhibitor could enhance the antitumor efficacy observed with either agent alone. The primary objective of this trial is to examine the safety and tolerability of sitravatinib combined with tislelizumab in patients with advanced solid tumors. Methods: Adult patients with histologically or cytologically confirmed, locally advanced or metastatic, non-small cell lung cancer (NSCLC), renal cell carcinoma (RCC), or ovarian cancer (OC) are enrolling in the open-label, multicenter, nonrandomized, phase 1b clinical trial. Entry criteria include Eastern Cooperative Oncology Group Performance Status ≤ 1 and adequate end-organ function. All patients will receive sitravatinib 120 mg PO QD in combination with tislelizumab 200 mg IV Q3W until progressive disease, unacceptable toxicity, death, withdrawal of consent, or study termination by the sponsor. Approximately 100 patients are expected to be enrolled in 5 cohorts (n=20 patients per cohort): Cohort A: anti-PD-(L)1 antibody-refractory/-resistant, metastatic, nonsquamous NSCLC; Cohort B: anti-PD-1(L)1 antibody-naive, metastatic, nonsquamous NSCLC; Cohort C: anti-PD-(L)1 antibody-refractory/-resistant, metastatic, clear cell RCC; Cohort D (China only): metastatic or advanced RCC without prior therapy; Cohort E: anti-PD-(L)1 antibody-naive, recurrent, platinum-resistant, epithelial OC. The primary endpoint is to assess safety and tolerability of the combination by monitoring adverse events (AEs) and serious AEs. Secondary endpoints include overall response rate, duration of response, disease control rate, progression-free survival assessed by RECIST version 1.1, and plasma concentrations and derived pharmacokinetic parameters of single- and repeated-dose sitravatinib. Seven patients have enrolled as of 3 January 2019 at the sites in Australia and China. Clinical trial registry number: NCT03666143 Citation Format: Jeffrey Goh, Ben Gao, Ben Markman, Hui Gan, Mark Voskoboynik, Yi-Long Wu, Jun Guo, Qing Zhou, Jun Zhao, Cheng Chen, Jingjun Qiu, Yingying Xu, Liu Yang, Michael Millward. A Phase Ib study to assess safety, tolerability, pharmacokinetics, and preliminary antitumor activity of sitravatinib in combination with tislelizumab in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT167.

Abstract 2372: Tumoral p53 mutations differentially mediate poor T-cell infiltration and autologous T-cell killing in preclinical models

Abstract Harnessing the immune system through the attenuation of endogenous immune checkpoints on T-cells has led to dramatic, durable tumor rejection in multiple solid tumors; however, most cancer types remain resistant to immunotherapy. It is imperative to understand the unique mechanisms by which these lethal malignancies evade the immune system in order to design efficacious therapies. Research by several groups is elucidating how overall mutational burden, tumor stroma, and patient microbiome predict response to immunotherapies in immune-resistant cancers. However, the frequency and distribution of driver mutations in the tumors themselves differ between immunogenic and non-immunogenic cancer types and may play a role in immune escape. Whereas p53, the most commonly mutated gene in cancer, is mutated in 70-90% of non-immunogenic tumors like pancreatic adenocarcinoma (PDAC), it is mutated in only 10-15% of immunogenic skin cutaneous melanoma cases. Loss of p53 through truncating mutations mediates tumor escape from apoptosis and senescence. Furthermore, many p53 missense mutations (mtp53) not only lose wild-type activity (LOF), but acquire novel gain-of-function (GOF) activities which promote oncogenesis and resistance to therapy. Pre-clinical data suggest that mtp53 differentially mediates tumor escape from immune surveillance by altering the innate immune response, including NK cell function and macrophage phenotype, thereby allowing tumorigenesis through chronic local immunosuppression. Few studies have been completed, however, to demonstrate the role of mtp53 in regulating the adaptive immune response. Understanding the role of p53 and its mutants in the regulation of T-cell function in cancer would provide a novel framework by which to understand and overcome resistance to cancer immunotherapy in many deadly cancer types. We hypothesize that mtp53 mediates evasion of T-cell anti-tumor activity, and that gain-of-function pathways downstream of mtp53 drive this process. Here we elaborate on previously presented work, elucidating how GOF vs. LOF mtp53 influences T-cell infiltration and killing using both novel model systems. Ultimately, these results may define a new role for mtp53 in influencing the immune system, and provide a rationale for developing effective combination strategies to improve response to immunotherapy. Citation Format: Deborah A. Silverman, Emily Ashkin, Benjamin Whitfield, Simone Punt, Soraya Zorro Manrique, Yunfei Wang, Anil Korkut, Leila Williams, Minying Zhang, Eran Kotler, Moshe Oren, Anirban Maitra, Patrick Hwu. Tumoral p53 mutations differentially mediate poor T-cell infiltration and autologous T-cell killing in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2372.