CD40 stimulation via CD40 ligand enhances adenovirus-mediated tumour immunogenicity including 'find-me', 'eat-me', and 'kill-me' signalling

Immunostimulatory gene therapy using oncolytic viruses is currently evaluated as a promising therapy for cancer aiming to induce anti-tumour immunity. Here, we investigate the capacity of oncolytic adenoviruses (LOAd) and their transgenes to induce immunogenicity in the infected tumour cells. Oncolysis and death-related markers were assessed after infection of eight human solid cancer cell lines with different LOAd viruses expressing a trimerized, membrane-bound (TMZ)-CD40L, TMZ-CD40L and 41BBL, or no transgenes. The viruses induced transgene expression post infection before they were killed by oncolysis. Death receptors TRAIL-R1, TRAIL-R2 and Fas as well as immunogenic cell death marker calreticulin were upregulated in cell lines post infection. Similarly, caspase 3/7 activity was increased in most cell lines. Interestingly, in CD40+ cell lines there was a significant effect of the TMZ-CD40L-encoding viruses indicating activation of the CD40-mediated apoptosis pathway. Further, these cell lines showed a significant increase of calreticulin, and TRAIL receptor 1 and 2 post infection. However, LOAd viruses induced PD-L1 upregulation which may hamper anti-tumour immune responses. In conclusion, LOAd infection increased the immunogenicity of infected tumour cells and this was potentiated by CD40 stimulation. Due to the simultaneous PD-L1 increase, LOAd viruses may benefit from combination with antibodies blocking PD1/PD-L1.

Single-Cell RNA Analysis Reveals Cell-Intrinsic Functions of CAR T Cells Correlating with Response in a Phase II Study of Lymphoma Patients

PURPOSE

Although CD19 chimeric antigen receptor T cells (CAR-T) therapy has shown remarkable success in B-cell malignancies, a substantial fraction of patients do not obtain a long-term clinical response. This could be influenced by the quality of the individual CAR-T infusion product. To shed some light on this, clinical outcome was correlated to characteristics of CAR-T infusion products.

PATIENTS AND METHODS

In this phase II study, patients with B-cell lymphoma (n = 23) or leukemia (n = 1) received one or two infusions of third-generation CD19-directed CAR-Ts (2 × 108/m2). The clinical trial was registered at clinicaltrials.gov: NCT03068416. We investigated the transcriptional profile of individual CD19 CAR-T infusion products using targeted single-cell RNA sequencing and multicolor flow cytometry.

RESULTS

Two CAR-T infusions were not better than one in the settings used in this study. As for the CAR-T infusion products, we found that effector-like CD8+CAR-Ts with a high polyfunctionality, high cytotoxic and cytokine production profile, and low dysfunctional signature were associated with clinical response. An extended ex vivo expansion time during CAR-T manufacturing negatively influenced the proportion of effector CD8+CAR-Ts in the infusion product.

CONCLUSIONS

We identified cell-intrinsic characteristics of effector CD8+CAR-Ts correlating with response that could be used as an indicator for clinical outcome. The results in the study also serve as a guide to CAR-T manufacturing practices.

Immunostimulatory gene therapy targeting CD40, 4-1BB and IL-2R activates DCs and stimulates antigen-specific T-cell and NK-cell responses in melanoma models

BACKGROUND

The activation of dendritic cells (DCs) is pivotal for generating antigen-specific T-cell responses to eradicate tumor cells. Hence, immunotherapies targeting this interplay are especially intriguing. Moreover, it is of interest to modulate the tumor microenvironment (TME), as this harsh milieu often impairs adaptive immune responses. Oncolytic viral therapy presents an opportunity to overcome the immunosuppression in tumors by destroying tumor cells and thereby releasing antigens and immunostimulatory factors. These effects can be further amplified by the introduction of transgenes expressed by the virus.

METHODS

Lokon oncolytic adenoviruses (LOAd) belong to a platform of chimeric serotype Ad5/35 viruses that have their replication restricted to tumor cells, but the expression of transgenes is permitted in all infected cells. LOAd732 is a novel oncolytic adenovirus that expresses three essential immunostimulatory transgenes: trimerized membrane-bound CD40L, 4-1BBL and IL-2. Transgene expression was determined with flow cytometry and ELISA and the oncolytic function was evaluated with viability assays and xenograft models. The activation profiles of DCs were investigated in co-cultures with tumor cells or in an autologous antigen-specific T cell model by flow cytometry and multiplex proteomic analysis. Statistical differences were analyzed with Kruskal-Wallis test followed by Dunn's multiple comparison test.

RESULTS

All three transgenes were expressed in infected melanoma cells and DCs and transgene expression did not impair the oncolytic activity in tumor cells. DCs were matured post LOAd732 infection and expressed a multitude of co-stimulatory molecules and pro-inflammatory cytokines crucial for T-cell responses. Furthermore, these DCs were capable of expanding and stimulating antigen-specific T cells in addition to natural killer (NK) cells. Strikingly, the addition of immunosuppressive cytokines TGF-β1 and IL-10 did not affect the ability of LOAd732-matured DCs to expand antigen-specific T cells and these cells retained an enhanced activation profile.

CONCLUSIONS

LOAd732 is a novel immunostimulatory gene therapy based on an oncolytic adenovirus that expresses three transgenes, which are essential for mediating an anti-tumor immune response by activating DCs and stimulating T and NK cells even under imunosuppressive conditions commonly present in the TME. These qualities make LOAd732 an appealing new immunotherapy approach.

Abstract 686: Immunostimulatory gene therapy with oncolytic viruses potentiates the effect of paclitaxel and cisplatin in ovarian cancer

Ovarian cancer is commonly treated with debulking surgery, followed by a combination of a taxane and a platinum-based chemotherapy. However, >70% of patients relapse within 3 years with tumors resistant to platinum-based agents. 5-year survival is ranging from 30-40%. Thus, delaying recurrence of disease is a high unmet need in ovarian cancer. Combining the chemotherapy regime with immunostimulatory gene therapy utilizing oncolytic viruses as gene vehicles is an attractive treatment option targeting alternative pathways to induce tumor cell death, control tumor growth and prevent development of metastasis. LOAd703 is an oncolytic adenovirus derived from the LOAd platform of replication-restricted Ad5/35 adenoviruses. LOAd703 encodes for the human immunostimulatory genes trimerized, membrane-bound CD40L (TMZ-CD40L) and 4-1BBL, expressed under a CMV promotor which enables gene expression in both tumor cells and tumor stroma while replication is restricted to tumor cells. Herein, we investigated the effect of combining LOAd703 with paclitaxel and cisplatin in vitro and in vivo. Four human ovarian cancer cell lines (CAOV3, COV362, OVCAR3 and PEA2) were treated with LOAd703 alone, in combination with paclitaxel and/or cisplatin or were left untreated. LOAd703 efficiently killed the ovarian cancer cell lines by oncolysis, as evaluated by an MTS cell viability assay. This effect was further improved when LOAd703 was given in combination with paclitaxel and/or cisplatin. Flow cytometry revealed that the ability of LOAd703 to induce expression of the immunostimulatory transgenes TMZ-CD40L and 4-1BBL, was not negatively affected by the combination with paclitaxel and/or cisplatin. The combination treatment was further tested in an in vivo model where BALB/c nu/nu mice were xenografted with 5 million OVCAR3 cells. The mice were subsequently treated with LOAd703 (1 × 10e9 FFU/mouse), both alone as well as in combination with paclitaxel (6mg/kg) and cisplatin (2.5mg/mg). The treatments were given over the course of 4 weeks where LOAd703 was administered intratumorally twice per week while chemotherapy was given intraperitoneally once per week. The results showed that the combination of LOAd703 and the chemotherapeutics controlled tumor growth significantly better than either LOAd703 alone or the standard treatment with paclitaxel and cisplatin. In conclusion, LOAd703 efficiently killed ovarian cancer cell lines in vitro, and could potentiate the effect of standard-of-care chemotherapy. This effect was confirmed in vivo, in which the combination therapy had a better tumor control than the other treatment groups. A clinical trial is ongoing to confirm the effect of adding LOAd703 to different treatment regimes in ovarian cancer (NCT03225989).

Citation Format: Sedigheh Naseri, Jonas Härdin, Emma Eriksson, Tanja Lövgren, Gustav Ullenhag, Angelica Loskog. Immunostimulatory gene therapy with oncolytic viruses potentiates the effect of paclitaxel and cisplatin in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 686.

Abstract 6663: Immunostimulatory gene therapy targeting CD40/4-1BB in combination with chemotherapy induces an inflammatory gene profile in tumors from patients with advanced disease

In the LOKON002 phase I/II clinical trial (NCT03225989), therapy with LOAd703 (delolimogene mupadenorepvec) is investigated in combination with gemcitabine-based chemotherapy in patients with advanced cancer. LOAd703 is an immunostimulatory gene therapy utilizing an oncolytic adenovirus that is engineered to express two transgenes (trimerized membrane-bound CD40L (TMZ-CD40L) and 4-1BBL), which are key players in the induction of an anti-tumor immune response. Herein, we present the preliminary immunological evaluation of the first 27 patients enrolled in the trial. The primary tumor was pancreatic cancer (n=16), colorectal cancer (n=5), ovarian cancer (n=3) or biliary cancer (n=3). Patients received a maximum of eight intratumoral LOAd703 treatments, given biweekly, and chemotherapy was administered at the same time according to standard protocol. Matched tumor biopsies from the injected tumor lesion were taken at baseline and after six LOAd703 treatments, and analyzed for gene expression with nCounter® PanCancer Immune Profiling Panel from NanoString (n=12; 7 patients analyzed so far). Blood samples were collected for isolation of serum samples and peripheral blood mononuclear cells, and these were analyzed with multiplex assays (Meso Scale Diagnostics) (n=15) and flow cytometry (n=27), respectively. Preliminary results indicate that after treatment, most tumors displayed a strong inflammatory profile with an upregulation of gene profiles, which have been shown to predict responses to immune checkpoint inhibitor therapy (T cell inflamed profile (Ayers et al.) & T effector and IFNγ associated profile (Fehrenbacher et al.)). We also noted an upregulation of genes connected to dendritic cell activation and antigen presentation (MHC class I and II, CD80, CD86, TAP1/2), as well as adenoviral-response genes. Moreover, we observed systemic treatment effects after three LOAd703 treatments, as shown by an increase in serum levels of pro-inflammatory cytokines and chemokines (IFNγ, IL-15, CXCL10, CCL2, IL-8, IL-6), as well as an increased percentage of CD8+ effector memory T cells (CD45RA-CCR7-) and PD-1+ CD8+ T cells in the blood. The fractions of natural killer (NK) cells (CD14-CD3-CD56+CD16+) and M2-like macrophages (CD11b+CD163+) were reduced in the blood at that time point. In conclusion, LOAd703 therapy in combination with chemotherapy generated an inflamed tumor microenvironment in tumors that are normally seen as immunologically “cold”. Hence, LOAd703 may be able to prime tumors for immune checkpoint inhibitors or other immunotherapies, such as adoptive T or NK cell transfer.

Citation Format: Jessica Wenthe, Emma Eriksson, Sedigheh Naseri, Linda Sandin, Amanda Hahn, Sandra Irenaeus, Anders Sundin, Justyna Leja-Jarblad, Gustav Ullenhag, Tanja Lövgren, Angelica Loskog. Immunostimulatory gene therapy targeting CD40/4-1BB in combination with chemotherapy induces an inflammatory gene profile in tumors from patients with advanced disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6663.

Abstract 1793: Single-cell RNA analysis reveal effector-like CD8+ CAR-T cell subpopulations associated with response in lymphoma patients

Although CD19-targeting CAR T cell therapy has shown remarkable success against B cell malignancies there is still room for improvement. To improve long-term responses amongst lymphoma patients, mechanisms underlying initial response and tumor relapses must be addressed. Recent studies have highlighted the importance of the quality of the starting cell material for CAR T cell production and the composition of the CAR T cell infusion product for clinical response. In our study, we have evaluated the clinical response to third generation anti-CD19 CAR T cell therapy in 23 patients with B cell lymphoma. Further, we evaluated the CAR T cell infusion products using targeted single-cell RNA sequencing and multi-color flow cytometry to find potential T cell subsets associating with clinical response. Patients were divided into responders (CR + PR) and non-responders (SD + PD) at the 1-month follow-up after treatment. The CAR T cell products of both responding and non-responding patients were dominated by CD8+ CAR T cells. When comparing cells from the two patient groups we found that the presence of effector-like CD8+ CAR T cells with a high cytotoxic and cytokine secretion and low dysfunction gene expression profile were associated with clinical response. Furthermore, CD8+ CAR T cells of responders displayed a higher polyfunctional gene expression profile, which has previously been shown to associate with clinical response. In contrast, CD8+ CAR T cells from the infusion products of non-responders displayed an elevated dysfunction gene expression profile. Our study reveals that single-cell RNA expression analysis of individual CAR T cell infusion product can identify subsets of effector cells correlating with clinical response. This can be used as a guidance in the CAR T cell production processes, to obtain CAR T cells with the desired characteristics.

Citation Format: Tina Sarén, Mohanraj Ramachandran, Gustav Gammelgård, Tanja Lövgren, Kristina Wikström, Jamileh Hashemi, Eva Freyhult, Claudio Mirabello, Åsa K Björklund, Håkan Ahlström, Rose-Marie Amini, Hans Hagberg, Angelica Loskog, Gunilla Enblad, Magnus Essand. Single-cell RNA analysis reveal effector-like CD8+ CAR-T cell subpopulations associated with response in lymphoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1793.

Abstract 695: Immunostimulatory gene therapy with an oncolytic virus expressing TMZ-CD40L and 4-1BBL induces oncolysis and show immunomodulatory capacity in soft tissue sarcoma

Soft-tissue sarcoma (STS) is a heterogeneous group of cancers, affecting both children and adults that develops from muscle, fat, tendons, vessels or connective tissues. Childhood STS accounts for up to 8% of all diagnosed pediatric cancer with rhabdomyosarcoma as the most common form. Prognosis depends on the type, stage and localization of the tumor, with a general 5-year survival of 70% for all STS patients. However, for patients with metastatic disease 5-year survival is 15%. The most common treatment for pediatric STS is surgery with adjuvant chemotherapy, and if possible radiotherapy. Immunotherapy, such as checkpoint blockade inhibitors (CPI), has revolutionized treatment for other malignancies such as melanoma. However, CPIs have shown limited efficacy in STS overall, and even less in pediatric patients. Thus, there is a strong need for new treatment options. Herein, we study a novel immunostimulatory gene therapy based on an oncolytic adenovirus, LOAd703, for efficacy in STS. LOAd703 is currently under clinical evaluation for several other solid cancers. LOAd703 is derived from the LOAd family of serotype 5/35 adenoviruses dependent on host cell entry via CD46. Modification of E1A has been introduced for selective replication and lysis of tumor cells. Moreover, LOAd703 is armed with the immunostimulatory genes trimerized, membrane-bound (TMZ)-CD40L and 4-1BBL expressed under control of a CMV promoter. A panel of 11 different cell lines from different STS subtypes and from both pediatric and adult patients were shown to express CD46 by flow cytometry before treatment. The cell lines were subsequently infected with LOAd703. CD46 expression was retained after infection and the infected cells upregulated the expression of the transgenes TMZ-CD40L and 4-1BBL. In addition, qPCR analysis confirmed LOAd703 replication in all tested cell lines in a time dependent manner. Replication induced oncolysis of all investigated cell lines, as analyzed by an MTS cell viability assay. In a co-culture system with peripheral blood mononuclear cells and infected sarcoma cells, preliminary results showed an alteration of markers associated with differentiation and activation among both innate and adaptive immune cells, including myeloid cells, NK cells and T cells. In conclusion, LOAd703 demonstrated a high oncolytic capacity and expression of the immunostimulatory transgenes in STS cells. Preliminary data shows that infected STS cells stimulate immune cells via the TMZ-CD40L and 4-1BBL transgenes. More in depth analysis will be performed on co-culture experiments to pinpoint the exact effect on different immune cell compartments. We are also performing multiplex analysis of proteomic changes in infected tumor cells using the OLINK® TARGET 96 assay. Finally, we willconfirm the effect of LOAd703 in vivo in a murine xenograft model for STS.

Citation Format: Ahmed Calandigary, Alireza Labani-Motlagh, Darko Tamindzic, Tanja Lövgren, Emma Eriksson, Angelica Loskog. Immunostimulatory gene therapy with an oncolytic virus expressing TMZ-CD40L and 4-1BBL induces oncolysis and show immunomodulatory capacity in soft tissue sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 695.

The signaling and the metabolic differences of various CAR T cell designs

Chimeric antigen receptor (CAR) T cell therapy is introduced as an effective, rapidly evolving therapeutic to treat cancer, especially cancers derived from hematological cells, such as B cells. CAR T cell gene constructs combine a tumor-targeting device coupled to the T cell receptor (TCR) zeta chain domain with different signaling domains such as domains derived from CD28 or 4-1BB (CD137). The incorporation of each specific co-stimulatory domain targets the immunometabolic pathways of CAR T cells as well as other signaling pathways. Defining the immunometabolic and signaling pathways by which CAR T cells become and remain active, survive, and eliminate their targets may represent a huge step forward in this relatively young research field as the CAR gene can be tailored to gain optimal function also for solid tumors with elaborate immunosuppression and protective stroma. There is a close relationship between different signaling domains applied in CAR T cells, and difficult to evaluate the benefit from different tested CAR gene constructs. In this review, we attempt to collect the latest findings regarding the CAR T cell signaling pathways that affect immunometabolic pathways.

Whole body FDG PET/MR for progression free and overall survival prediction in patients with relapsed/refractory large B-cell lymphomas undergoing CAR T-cell therapy

BACKGROUND

To find semi-quantitative and quantitative Positron Emission Tomography/Magnetic Resonance (PET/MR) imaging metrics of both tumor and non-malignant lymphoid tissue (bone marrow and spleen) for Progression Free Survival (PFS) and Overall Survival (OS) prediction in patients with relapsed/refractory (r/r) large B-cell lymphoma (LBCL) undergoing Chimeric Antigen Receptor (CAR) T-cell therapy.

METHODS

A single-center prospective study of 16 r/r LBCL patients undergoing CD19-targeted CAR T-cell therapy. Whole body 18F-fluorodeoxyglucose (FDG) PET/MR imaging pre-therapy and 3 weeks post-therapy were followed by manual segmentation of tumors and lymphoid tissues. Semi-quantitative and quantitative metrics were extracted, and the metric-wise rate of change (Δ) between post-therapy and pre-therapy calculated. Tumor metrics included maximum Standardized Uptake Value (SUV_max), mean SUV (SUV_mean), Metabolic Tumor Volume (MTV), Tumor Lesion Glycolysis (TLG), structural volume (V), total structural tumor burden (V_total) and mean Apparent Diffusion Coefficient (ADC_mean). For lymphoid tissues, metrics extracted were SUV_mean, mean Fat Fraction (FF_mean) and ADC_mean for bone marrow, and SUV_mean, V and ADC_mean for spleen. Univariate Cox regression analysis tested the relationship between extracted metrics and PFS and OS. Survival curves were produced using Kaplan-Meier analysis and compared using the log-rank test, with the median used for dichotomization. Uncorrected p-values < 0.05 were considered statistically significant. Correction for multiple comparisons was performed, with a False Discovery Rate (FDR) < 0.05 considered statistically significant.

RESULTS

Pre-therapy (p < 0.05, FDR < 0.05) and Δ (p < 0.05, FDR > 0.05) total tumor burden structural and metabolic metrics were associated with PFS and/or OS. According to Kaplan-Meier analysis, a longer PFS was reached for patients with pre-therapy MTV ≤ 39.5 ml, ΔMTV≤1.35 and ΔTLG≤1.35. ΔSUV_max was associated with PFS (p < 0.05, FDR > 0.05), while ΔADC_mean was associated with both PFS and OS (p < 0.05, FDR > 0.05). ΔADC_mean > 0.92 gave longer PFS and OS in the Kaplan-Meier analysis. Pre-therapy bone marrow SUV_mean was associated with PFS (p < 0.05, FDR < 0.05) and OS (p < 0.05, FDR > 0.05). For bone marrow FDG uptake, patient stratification was possible pre-therapy (SUV_mean ≤ 1.8).

CONCLUSIONS

MTV, tumor ADC_mean and FDG uptake in bone marrow unaffected by tumor infiltration are possible PET/MR parameters for prediction of PFS and OS in r/r LBCL treated with CAR T-cells.

TRIAL REGISTRATION

EudraCT 2016-004043-36.

Donor-derived urologic cancers after renal transplantation: A retrospective non-randomized scientific analysis

Background

Malignancies in the urinary tract and the kidney graft are quite common after kidney transplantation. In some selected cases tumours develop from donor-derived tissue.

Objectives

We hypothesised that there is a clinical value to investigate donor/recipient origin in urologic malignancies in renal transplant recipients.

Methods

In this retrospective study, including patients transplanted between the years 1969 and 2014 at Uppsala University Hospital, Sweden, 11 patients with malignancies in urinary tract and 4 patients with malignancies in kidney transplants were investigated. Donor/recipient origin of tumour tissue was analysed by polymerase chain reaction (PCR) of human leucocyte antigen (HLA) genotypes or by fluorescence in situ hybridization (FISH analysis) of sex chromosomes. HLA genotype and sex chromosomes of the tumour were compared to the known HLA genotype and sex chromosomes of recipient and donor.

Results

Three of ten cancers in the urinary tract and three of four cancers in the kidney transplants were donor-derived.

Conclusions

We suggest that urologic malignancies in renal transplant recipients can be investigated for transplant origin. In addition to conventional therapy the allograft immune response against these tumours can be valuable to treat donor-derived cancers.

Abstract 3501: Induction of tumor cell apoptosis & immunogenic cell death by CD40L-armed oncolytic adenoviruses

Low tumor immunogenicity and a cold tumor microenvironment are two main characteristics occurring in different cancer types responsible for immunotherapy resistance. Immunostimulatory gene therapy using oncolytic viruses (OVs) has been developed as a new promising cancer therapy for its capacity to induce an anti-tumor immune response and sensitize the non-responding patients to checkpoint blockade therapy. Lokon adenoviruses (LOAds) are serotype 5/35 oncolytic adenoviruses that in addition to their oncolytic capacity encode for immunostimulatory molecules. Here we have evaluated the anti-tumor effects of trimerized membrane-bound (TMZ)-CD40L-armed LOAd700 and TMZ-CD40L/4-1BBL-armed LOAd703 in a variety of solid tumors to understand the underlying tumor modulating mechanisms. A panel of eight different human solid cancer cell lines (T24, PEA2, Mel526, H727, Skov3, MiaPaca2, H29 and A549) was infected with LOAd(-), a virus without transgenes, LOAd700 or LOAd703 and assessed for their response in different assays. MTS assay was used to measure the cell viability, flow cytometry for evaluating the cell surface markers and luminescent assay for measuring apoptosis (caspase 3/7 activity). LOAd viruses efficiently killed all tested cell lines. However, the oncolytic capacity of CD40L-armed LOAd700 and LOAd703 was significantly higher than LOAd(-) in two cell lines, T24 and PEA2, which were found to express the CD40 receptor. Death receptor TRAIL-R1 was significantly upregulated in T24 infected with LOAd703 and PEA2 infected with either LOAd700 or LOAd703. TRAIL-R2 was upregulated post LOAd infection in 7/8 cell lines where the upregulation was significant in T24, PEA2 and H29. Interestingly, the immunogenic cell death marker calreticulin, a damage-associated molecular pattern (DAMP) known as an “eat-me” signal to dendritic cells, was upregulated post LOAd infection in all cell lines. The increase in calreticulin level was statistically significant in 4/8 cell lines (T24, PEA2, Mel526 and H29) post LOAd700 and/or LOAd703 infection. Furthermore, LOAd700 and LOAd703 increased the effector caspase 3/7 activity in 5/8 cell lines (T24, PEA2, Mel526, Skov3 and MiaPaCa2) indicating an augmented apoptosis level. In conclusion, CD40L-armed LOAd viruses were, in addition to their high oncolytic capacity, demonstrated to induce apoptosis. Upregulation of cell surface calreticulin as well as the death receptors TRAIL-R1 and -R2 indicated generation of a more immunogenic phenotype of cancer cells. Thus, our findings suggest that CD40L-armed LOAd viruses could be inducers of apoptosis and immunogenic cell death in a variety of cancer types with an augmented effect in cancer cells expressing the CD40 receptor.

Citation Format: Sedigheh Naseri, Mariela Mejia Cordova, Jessica Wenthe, Ann-Charlotte Hellström, Tanja Lövgren, Angelica Loskog, Emma Eriksson, Gustav Ullenhag. Induction of tumor cell apoptosis & immunogenic cell death by CD40L-armed oncolytic adenoviruses [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 3501.

Abstract 3562: LOAd732 - a novel oncolytic adenovirus with enhanced immunostimulatory properties and resistance to immunosuppression

Immunotherapy aims at activating or re-activating the immune system to create an anti-tumor response that could lead to eradication of the tumor cells. Central is the activation of dendritic cells (DCs) capable of presenting tumor antigens to T cells that can expand and kill tumor cells. However, the tumor is a harsh environment for the adaptive immune system and many of the conditions needed for the establishment of an immune response are lacking. Oncolytic viral therapy presents an opportunity to overcome the immunosuppression in tumors by destroying tumor cells, releasing antigens and immunostimulatory factors. The effects of the oncolytic virus can be further amplified by the introduction of transgenes expressed by the virus. LOAd oncolytic adenoviruses belong to a platform of Ad5/35 adenoviruses that have replication restricted to tumor cells. The viruses express human immunostimulatory transgenes under a CMV promotor that enables expression in all infected cells. LOAd703, encoding trimerized (TMZ)-CD40L and 4-1BBL, is under clinical investigation in solid tumors. Herein we present the data from the investigation of our novel oncolytic adenovirus LOAd732 that encodes for three human transgenes; TMZ-CD40L, 4-1BBL and IL-2. Infection of the human cell lines Mel526 and Mel624 with LOAd732 led to cell killing as was evaluated by MTS viability assay and to expression of the transgenes, TMZ-CD40L, 4-1BBL and IL-2 evaluated by flow cytometry and ELISA. Moreover the immmunostimulatory function of LOAd732 was investigated by infecting immature dendritic cells, differentiated from CD14+ monocytes using GM-CSF and IL-4. Flow cytometry assay revealed that DCs infected with LOAd732 showed a mature profile with expression of activation markers and co-stimulatory molecules such as CD80, CD83, CD86, CD70, ICAM-1, and MHC molecules. Analysis of supernatants from the cultures with multiplex immunoassay (MDS technology) showed that LOAd732 DCs produce IL-12p70, IL-15, IL-21 and CXCL10. To assess the functionality of the DCs infected by LOAd732, the capacity of the cells to expand antigen-specific T cells were investigated in a CMV model system where DCs from CMV positive donors are pulsed with a CMV peptide and co-cultured with autologous T cells. LOAd732 infected DCs could expand CMV-specific CD8+ T cells. Since the tumor microenvironment often is immunosuppressive, TGF-β and IL-10 was added to the co-cultures to model these conditions. The addition of the immunosuppressing cytokines did not affect LOAd732 capacity to expand the antigen-specific T cells.

In conclusion, LOAd732 infected DCs express activation markers and co-stimulatory molecules and produce cytokines necessary for the initiation of an immune response. Moreover the DCs are functional and can expand antigen-specific T cells and protect them from TGF-β and IL-10 suppression.

Citation Format: Jessica Wenthe, Emma Eriksson, Tanja Lövgren, Rafael Moreno, Ramon Alemany, Angelica Loskog. LOAd732 - a novel oncolytic adenovirus with enhanced immunostimulatory properties and resistance to immunosuppression [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 3562.

Immune priming using DC- and T cell-targeting gene therapy sensitizes both treated and distant B16 tumors to checkpoint inhibition

Immune checkpoint inhibitors have revolutionized the treatment of metastatic melanoma, but most tumors show resistance. Resistance is connected to a non-T cell inflamed phenotype partially caused by a lack of functional dendritic cells (DCs) that are crucial for T cell priming. Herein, we investigated whether the adenoviral gene vehicle mLOAd703 carrying both DC- and T cell-activating genes can lead to inflammation in a B16-CD46 model and thereby overcome resistance to checkpoint inhibition therapy. B16-CD46 cells were injected subcutaneously in one or both flanks of immunocompetent C57BL/6J mice. mLOAd703 treatments were given intratumorally alone or in combination with intraperitoneal checkpoint inhibition therapy (anti-PD-1, anti-PD-L1, or anti-TIM-3). Tumor, lymph node, spleen, and serum samples were analyzed for the presence of immune cells and cytokines/chemokines. B16-CD46 tumors were non-inflamed and resistant to checkpoint blockade. In contrast, mLOAd703 treatment led to infiltration of the tumor by CD8⁺ T cells, natural killer (NK) cells, and CD103⁺ DCs, accompanied by a systemic increase of pro-inflammatory cytokines interferon γ (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin-27 (IL-27). This response was even more pronounced after combining the virus with checkpoint therapy, in particular with anti-PD-L1 and anti-TIM-3, leading to further reduced tumor growth in injected lesions. Moreover, anti-PD-L1 combination also facilitated abscopal responses in non-injected lesions.

Abstract PO-018: Inflaming advanced solid tumors including pancreatic cancer using LOAd703, a TMZ-CD40L/4-1BBL-armed oncolytic virus

Pancreatic ductal adenocarcinoma (PDAC) is resistant to PD1/PDL1 blocking antibodies. The purpose of this study was to evaluate if immunotherapy with LOAd703, an oncolytic adenovirus armed with trimerized CD40L and 4-1BBL, can sensitize PDAC to mAbs targeting PD1/PDL1. The high content of myeloid-derived suppressor cells (MDCSs) in the tumor microenvironment may in part explain the limited anti-tumor T cell response in PDAC. We have previously shown that gemcitabine can reduce MDSCs in patients with PDAC, with the T cell proliferative capacity remaining intact. Further, LOAd703 has been demonstrated to efficiently and robustly kill PDAC cells and stimulate the maturation of dendritic cells (DCs), which, in turn, induces T cell activation. Patients with advanced PDAC, colorectal, biliary, and ovarian cancer (NCT03225989) were treated with intratumoral injections of LOAd703 combined with appropriate chemotherapy such as gemcitabine ± nab-paclitaxel for PDAC patients, or combined with gemcitabine if there was no standard of care. Blood sampling was performed for immune cell profiling and anti-adenovirus antibodies (flow cytometry, ELISA). Tumor biopsies were also analyzed for mRNA expression (NanoString; PanCancer Immune Profiling Panel). The study was approved by the ethical review board and the Swedish Medical Products Agency. The dose of LOAd703 was escalated (5 × 10e10 VP, 1 × 10e11 VP, 5 × 10e11VP) in separate cohorts of new patients and administered every other week. To date, blood samples from 23 patients have been analyzed by flow cytometry to profile immune cells. The mean percentages of monocytic- and granulocytic MDSCs, Tregs and M2-like myeloid cells were significantly decreased after treatment initiation. The effector memory (EM) and central memory (CM) CD8+ T cells were significantly increased, while naïve and CM cells were increased among CD4 T cells. Both CD4 and CD8 T cells expressing ICOS were present post-treatment but only CD8 T cells showed significant elevation of PD1. The NanoString data were analyzed using published mRNA immune signatures (bioinformatics). LOAd703 in combination with chemotherapy inflamed tumor lesions as shown by increased markers of the T cell inflamed signature (16 genes), T effector cell signature (19 genes), expanded immune signature (25 genes) and IFNg-related gene signature (12 genes) (week 1 versus week 13). Anti-adenovirus antibody titers increased in all patients after treatment initiation. The antibody levels did not correlate with the dose of virus, radiological response to treatment, nor overall survival. The results presented herein show that LOAd703 combined with chemotherapy enhances immune reactivity in patients with immune cold tumors as demonstrated by increases in EM and CM T cells in the peripheral blood, while suppressive immune cells were decreased. Further, the tumor milieu was inflamed post treatment as shown by mRNA profiling. Hence, LOAd703 may sensitize immune cold tumors to mAbs targeting PD1/PDL1.

Citation Format: Jessica Wenthe, Emma Eriksson, Linda Sandin, Tanja Lövgren, Justyna Leja Jarblad, Hanna Dahlstrand, Ulla Olsson-Strömberg, Aglaia Schiza, Anders Sundin, Sandra Irenaeus, Eric Rowinsky, Gustav Ullenhag, Angelica Loskog. Inflaming advanced solid tumors including pancreatic cancer using LOAd703, a TMZ-CD40L/4-1BBL-armed oncolytic virus [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-018.

Abstract 1689: Exosomes derived from tumor cells treated with immunostimulatory oncolytic virotherapy exert immune activation instead of immunosuppression

Immunostimulatory gene therapy using oncolytic viruses - OV - for combined gene transfer and tumor-specific oncolysis is a promising immunotherapy for cancer. Due to neutralizing antibodies in the blood, OVs are commonly administered by intratumoral delivery. The immune activation is both local and systemic as activated dendritic cells in the injected lesion travel to lymph nodes to activate tumor-reactive T cells that can in turn act on both injected and non-injected lesions. In the present project, we demonstrate that OV-infected tumor cells released exosomes that cargo mRNA and protein coded by the human immunostimulatory genes expressed by the OV. Tumor cell-derived exosomes are commonly immunosuppressive because they cargo immunosuppressive molecules expressed by the tumor. We hypothesized that exosomes derived from OV-infected tumor cells may instead be immunostimulatory. To investigate the role of exosomes derived from OV-treated tumors, human melanoma Mel526 cells were infected by delolimogene mupadenorepvec -LOAd703 - which is an adenoviral serotype 5/35 OV armed with costimulatory molecules CD40L and 4-1BBL. LOAd703 could induce expression of CD40L and 4-1BBL on the melanoma cell surface and kill the cells by replication-induced oncolysis after 48-72 hours culture as evaluated by MTS. Exosomes were purified prior oncolysis and investigated for the presence of CD40L and 4-1BBL mRNA and protein, and for their capacity to stimulate immune responses. The results demonstrated that the exosomes can indeed cargo CD40L and 4-1BBL both as mRNA as shown by PCR, and protein as shown by ELISA, western blot, flow cytometry and electron microscopy post LOAd703 tumor cell infection. Furthermore, the exosomes from CD40L and 4-1BBL-expressing tumor cells could stimulate robust dendritic cell activation with enhanced levels of MHC class I and II as well as costimulatory molecules CD80, CD86 and CD83. In contrast, MHC class I and the costimulatory molecules were reduced on dendritic cells stimulated with exosomes derived from non-infected tumor cells, which is in line with previous knowledge of exosomes as immunosuppressants in the tumor. However, PD-L1 was increased on dendritic cells stimulated with the exosomes from CD40L and 4-1BBL-expressing tumor cells. Hence, LOAd703 therapy may benefit from combination with PD-L1 or PD-1 checkpoint blockade. In conclusion, tumor-derived exosomes released by OV-infected tumor cells can cargo the immunostimulatory transgenes expressed by the OVs and are then converted from immunosuppressive to immune activating exosomes as shown by their capacity to activate immune cells such as dendritic cells. Exosomes that cargo immunostimulatory transgenes from OV-infected tumor cells may support the systemic immunity gained by OVs after local intratumoral delivery.

Citation Format: Alireza Labani-Motlagh, Sedigheh Naseri, Jessica Wenthe, Emma Eriksson, Angelica Loskog. Exosomes derived from tumor cells treated with immunostimulatory oncolytic virotherapy exert immune activation instead of immunosuppression [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 1689.

Systemic immunity upon local oncolytic virotherapy armed with immunostimulatory genes may be supported by tumor-derived exosomes

Immunostimulatory gene therapy utilizing oncolytic viruses (OVs) as gene vehicles is a promising immunotherapy for cancer. Since viruses are immunogenic, systemic delivery can be troublesome due to neutralizing antibodies. Nevertheless, local delivery by intratumoral injection seems to induce systemic immune reactions. In this study, we demonstrate a novel mechanism of action of armed OV therapy suggesting that exosomes released by tumor cells infected with armed OV may participate to activate the immune system and this may also support systemic immunity. Tumor cell-derived exosomes commonly exert immunosuppressive functions. We hypothesized that exosomes derived from OV-infected tumor cells may instead be immunostimulatory. Human melanoma cells were infected by OVs armed with costimulatory molecules CD40 ligand (CD40L) and 4-1BB ligand (4-1BBL). Exosomes were purified and investigated for the presence of CD40L/4-1BBL mRNA and protein, and for their capacity to stimulate immune responses. The results show that the exosomes cargo transgenes. The exosomes from CD40L/4-1BBL-expressing tumor cells, or the viruses themselves, could stimulate robust dendritic cell (DC) activation with an enhanced level of major histocompatibility complex (MHC) and costimulatory molecules. Hence, exosomes after OV infection can locally activate immune responses at the tumor site and encounter immune cells such as DCs.

Intratumoral immunostimulatory AdCD40L gene therapy in patients with advanced solid tumors

AdCD40L is a replication-deficient virus carrying the gene for CD40 ligand which has previously been evaluated in patients with urothelial cancer and malignant melanoma. Herein, we present the results of repeated intratumoral injections of AdCD40L in seven patients with metastatic solid cancer. One patient who developed urothelial cancer derived from a renal transplant was treated with repeated injections of AdCD40L alone. The remaining patients suffered from cholangiocarcinoma, kidney, breast, rectal, or ovarian cancer and received AdCD40L repeatedly (4x) in combination with cyclophosphamide. The treatment was safe and generally well-tolerated. Two patients had clinical benefit of the treatment and one of them was accepted for re-treatment. Circulating proinflammatory cytokines were commonly increased after treatment, but save for TNFα, significances were not reached which could be due to the low number of patients. Similar to earlier findings in AdCD40L-treated melanoma patients, IL8 plasma levels were high in the present study. In conclusion, gene therapy by repeated intratumoral AdCD40L injections alone, or in combination with cyclophosphamide, is feasible and safe in patients with solid cancers. The potential of intratumoral CD40L gene transfer as treatment of cancer was illustrated by the clinical improvement in two out of seven patients.

Abstract 915: Abscopal effect using intratumoral oncolytic virotherapy (LOAd703) is enhanced by anti-PD-1 or anti-PD-L1

The purpose of this study was to evaluate the anti-tumor immune response using an oncolytic adenovirus encoding TMZ-CD40L and 4-1BBL (LOAd703) with or without PD-1 or PD-L1 checkpoint blockade. Oncolytic immunostimulatory viruses are currently being evaluated for their capacity to sensitize checkpoint blockade resistant patients to checkpoint blockade therapy since resistance is associated with a non-inflamed tumor phenotype. Herein we evaluated LOAd703, with or without PD-1 or PD-L1 blockade, in preclinical melanoma models. A murine version of LOAd703 (mLOAd703) expressing murine TMZ-CD40L and 4-1BBL was evaluated in the B16-hCD46/C57BL6 model. Immune activation was determined by flow cytometry and multiplex assays from Meso Scale Discovery. Note that adenoviruses do not replicate in murine cells, hence, the treatment effect of mLOAd703 in animal models is only due to expression of the immunostimulatory transgenes. Single and twin-tumor models were used to evaluate the effect of mLOAd703 (1 × 10e9 ffu/treatment) by repeated intravenous (i.v.) or intratumoral (i.t.) injections (one lesion). I.v. treatment did not control tumor growth likely due to the anti-adenovirus antibodies post LOAd703 exposure as evaluated by ELISA. In contrast, i.t. treatment could control growth of the injected tumor as well as hamper growth of the non-injected tumor demonstrating that it is more important to induce systemic immunity from a highly active tumor site (high virus load) than to reach all lesions with a small number of viral particles as shown by PCR. Further, mice with single or twin-tumors were treated with i.t. mLOAd703 (1 × 10e9 ffu), anti-PD-1 or anti- PD-L1 (intraperitoneal 5 mg/kg/injection), or a combination of either antibody and mLOAd703. Anti-PD-1 and PD-L1 monotherapy had only a limited effect on tumor growth in this model, whereas the combination with mLOAd703 could control the growth of the injected tumor and further delay the growth of the non-injected tumor compared to mLOAd703 alone. In agreement, flow cytometry analysis of the tumor biopsies showed an increase of CD8+ T cells in both tumors. In line with tumor inflammation, serum levels of T effector cytokines such as IFNg and TNFa were highest in animals treated with the combination. In conclusion, local mLOAd703 virotherapy induced a systemic anti-tumor immune response in the B16-hCD46 melanoma model. The abscopal effect was further increased by combining mLOAd703 with anti-PD-1 or anti-PD-L1. LOAd703 (i.t.) is currently in clinical development with and without PD-L1.

Citation Format: Jessica Wenthe, Sedigheh Naseri, Ann-Charlotte Hellström, Rafael Moreno, Gustav Ullenhag, Ramon Alemany, Tanja Lövgren, Emma Eriksson, Angelica Loskog. Abscopal effect using intratumoral oncolytic virotherapy (LOAd703) is enhanced by anti-PD-1 or anti-PD-L1 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 915.

Mebendazole is unique among tubulin-active drugs in activating the MEK-ERK pathway

We recently showed that the anti-helminthic compound mebendazole (MBZ) has immunomodulating activity in monocyte/macrophage models and induces ERK signalling. In the present study we investigated whether MBZ induced ERK activation is shared by other tubulin binding agents (TBAs) and if it is observable also in other human cell types. Curated gene signatures for a panel of TBAs in the LINCS Connectivity Map (CMap) database showed a unique strong negative correlation of MBZ with MEK/ERK inhibitors indicating ERK activation also in non-haematological cell lines. L1000 gene expression signatures for MBZ treated THP-1 monocytes also connected negatively to MEK inhibitors. MEK/ERK phosphoprotein activity testing of a number of TBAs showed that only MBZ increased the activity in both THP-1 monocytes and PMA differentiated macrophages. Distal effects on ERK phosphorylation of the substrate P90RSK and release of IL1B followed the same pattern. The effect of MBZ on MEK/ERK phosphorylation was inhibited by RAF/MEK/ERK inhibitors in THP-1 models, CD3/IL2 stimulated PBMCs and a MAPK reporter HEK-293 cell line. MBZ was also shown to increase ERK activity in CD4+ T-cells from lupus patients with known defective ERK signalling. Given these mechanistic features MBZ is suggested suitable for treatment of diseases characterized by defective ERK signalling, notably difficult to treat autoimmune diseases.

The Tumor Microenvironment: A Milieu Hindering and Obstructing Antitumor Immune Responses

The success of cancer immunotherapy relies on the knowledge of the tumor microenvironment and the immune evasion mechanisms in which the tumor, stroma, and infiltrating immune cells function in a complex network. The potential barriers that profoundly challenge the overall clinical outcome of promising therapies need to be fully identified and counteracted. Although cancer immunotherapy has increasingly been applied, we are far from understanding how to utilize different strategies in the best way and how to combine therapeutic options to optimize clinical benefit. This review intends to give a contemporary and detailed overview of the different roles of immune cells, exosomes, and molecules acting in the tumor microenvironment and how they relate to immune activation and escape. Further, current and novel immunotherapeutic options will be discussed.

Immunostimulatory oncolytic virotherapy for multiple myeloma targeting 4-1BB and/or CD40

Multiple myeloma (MM) is a plasma cell malignancy that is characterized by immune dysregulation. MM is commonly treated with immunomodulating agents, but still remains incurable. Herein, we proposed and evaluated immunostimulatory Lokon oncolytic adenoviruses (LOAd) for MM treatment. LOAd viruses are serotype 5/35 chimera, which enables infection of hematopoietic cells. Oncolysis is restricted to cells with a dysregulated retinoblastoma protein pathway, which is frequently observed in MM. Further, LOAd viruses are armed with human immunostimulatory transgenes: trimerized membrane-bound CD40L (LOAd700, LOAd703) and 4-1BBL (LOAd703). LOAd viruses were assessed in a panel of MM cell lines (ANBL-6, L363, LP-1, OPM-2, RPMI-8226, and U266-84). All cells were sensitive to infection, leading to viral replication and cell killing as analyzed by quantitative PCR and viability assay. Transgene expression was verified post infection with flow cytometry. Cell phenotypes were further altered with a downregulation of markers connected to MM progression (ICAM-1, CD70, CXCL10, CCL2, and sIL-2Rα) and an upregulation of the death receptor Fas. In a co-culture of immune and MM cells, LOAd viruses promoted activation of cytotoxic T cells as seen by higher CD69, CD107a, and IFNγ expression. This was most prominent with LOAd703. In conclusion, LOAd viruses are of interest for MM therapy.

Phase 1 study of the protein deubiquitinase inhibitor VLX1570 in patients with relapsed and/or refractory multiple myeloma

This phase 1 study sought to characterize the safety, tolerability, and pharmacokinetic behavior of VLX1570, a small molecule inhibitor of the deubiquitinases (DUBs) that remove sterically bulky ubiquitin chains from proteins during processing in the19S regulatory subunit of the proteasome, in patients with relapsed and refractory multiple myeloma (MM). Fourteen patients were treated with escalating doses of VLX1570 ranging from 0.05 to 1.2 mg/kg as a brief intravenous (IV) infusion on Days 1, 2, 8, 9, 15, and 16 of a 28-day cycle. Due to its poor aqueous solubility, VLX1570 was formulated in polyethylene glycol, polyoxyethylated castor oil, and polysorbate 80 and administered as a brief intravenous (IV) infusion via a central venous catheter. Anti-myeloma effects were noted at doses at or above 0.6 mg/kg, however, two patients treated at the 1.2 mg/kg dose level experienced severe, abrupt, and progressive respiratory insufficiency, which was associated with diffuse pulmonary infiltrates on imaging studies, similar to those rarely noted with bortezomib and other inhibitors of the 20S proteasome, culminating in death. Although the contribution of VLX1570’s formulation to the pulmonary toxicity could not be ruled out, the severity and precipitous nature of the toxicity and the steep relationship between dose and toxicity, the study was discontinued. Despite the severe pulmonary toxicity noted with VLX1570, efforts directed at identifying DUB inhibitors with greater therapeutic indices appear warranted based on the unique mechanism of action, robustness of preclinical antitumor activity, and activity of the DUB inhibitors in MM resistant to PIs targeting the 20S proteasome subunit.

Abstract 5018: Activation of dendritic cells by immunostimulatory CD40L/4-1BBL-encoding oncolytic virotherapy in melanoma

Checkpoint blockade antibody therapy has revolutionized the treatment of metastatic melanoma. However, up to 50% of patients establish treatment resistance, which is frequently connected to a non-T cell inflamed phenotype. Poor T cell activation and infiltration is suggested to be caused by a lack of functional dendritic cells (DCs) that are crucial for T cell priming. Indeed, in progressing melanoma patients, immature DCs are often increased in the tumor lesion and draining lymph node. Herein, we investigated the effect of an immunostimulatory oncolytic adenovirus LOAd703 in a humanized melanoma-DC model. LOAd703 (serotype Ad5/35) carries two immunostimulatory transgenes; trimerized membrane-bound (TMZ)-CD40 ligand and 4-1BBL. Viral replication is restricted to tumor cells but transgene expression is controlled by a CMV promoter, which allows expression also in healthy cells of the surrounding tumor microenvironment (TME).

LOAd703 efficiently infected and killed the human melanoma cell line 526-mel as evaluated by MTS viability assay. Infected 526-mel cells expressed both TMZ-CD40L and 4-1BBL as verified by flow cytometry. To investigate LOAd703’s effect on DC maturation, immature DCs were differentiated from CD14+ monocytes using GM-CSF and IL-4 and infected with LOAd703 or stimulated with MEGACD40L®, which is a highly active CD40L oligomer. Flow cytometry analysis revealed that LOAd703-infected DCs upregulated the expression of maturation markers and co-stimulatory molecules in a similar manner as high doses of MEGACD40L®. These included CD83, CD80, CD86, CCR7, ICAM-1 and MHC molecules. Interestingly, CD70 that is required for CD27 stimuli of T cells and lowers T cell receptor signaling threshold, was highly upregulated on the DCs using LOAd703, but not MEGACD40L®. Tumor cells are often immunosuppressive which may reduce the capacity of LOAd703 to activate DCs. To model this, immature DCs were co-cultured with LOAd703-infected 526-mel cells, which is also better mimicking the events in the TME. Co-cultured DCs upregulated the same markers as before, but this upregulation was twofold higher for CD83 and CD80. In agreement with the previous observation that CD40L signaling alone did not induce CD70 expression, CD70 expression on DCs was lower in the co-culture, indicating that a direct infection of the virus and potentially signaling through TLRs together with CD40L signaling is required to induce CD70 on DCs or that it may be inhibited by immunosuppressive factors released by the tumor. LOAd703-matured DCs also upregulated PD-L1 and thus it would be of interest to combine LOAd703 therapy with PD-L1/PD-1 blockade.

In conclusion, LOAd703 killed human melanoma cells and induced the expression of TMZ-CD40L and 4-1BBL in infected cells. Moreover, LOAd703 infection activated DCs to express costimulatory molecules, as well as CCR7, which is essential for a systemic immune response.

Citation Format: Jessica Wenthe, Tanja Lövgren, Mantas Šilanskas, Emma Eriksson, Angelica Loskog. Activation of dendritic cells by immunostimulatory CD40L/4-1BBL-encoding oncolytic virotherapy in melanoma [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 5018.

Abstract 4092: CD40L/4-1BBL virotherapy enhances efficacy of checkpoint blockade therapy in a resistant melanoma model

Despite the impressive effects of checkpoint blockade antibody therapy seen across indications, many patients remain resistant to treatment. PD-1/PD-L1 blockade aims to restore the function of anergic tumor-infiltrating T cells, thereby inducing an efficient anti-tumor response. Thus, a prerequisite to benefit from checkpoint blockade is the presence of T cells in the tumor. One promising strategy to prime non-inflamed tumors for checkpoint blockade is the use of oncolytic viruses, which can additionally be engineered to express immunostimulatory molecules to further induce immune activation and T cell infiltration. In this study, we are investigating the use of the oncolytic adenovirus mLOAd703 expressing a murine trimerized membrane-bound (TMZ)-CD40L and 4-1BBL in the syngeneic murine B16 melanoma model. Adenoviruses cannot replicate in murine cells, but the immunostimulatory effect of the murine transgenes TMZ-CD40L and 4-1BBL can still be evaluated. LOAd703 (serotype 5/35) targets human CD46 for viral entry. Thus, a B16 cell line expressing human CD46 was used to allow infection.

Upon infection with mLOAd703, B16-hCD46 cells not only expressed the transgenes TMZ-CD40L and 4-1BBL, but also changed their phenotype to become more immunogenic by upregulating co-stimulatory molecules CD80 and CD86, as well as MHC molecules. Moreover, expression of the death receptor Fas was increased, altogether potentially making the tumor cells more susceptible to T cell-mediated killing. Strikingly, two markers (CD44 and beta-3 integrin) associated with metastasis were reduced upon virus infection. Previous in vivo studies in immunocompetent C57BL6 mice with a predecessor of mLOAd703, which only expresses murine TMZ-CD40L, led to an increase of CD8+ T cells and CD11b+MHCII+ antigen presenting cells in the tumors. However, these cells also upregulated PD-1 or PD-L1, respectively, which warrants a combination with P-D1/PD-L1 checkpoint blockade. To evaluate this combination, mice with established B16-hCD46 tumors were treated with mLOAd703 (intratumoral 6x, 1x10e9 IU/mouse/injection), checkpoint blockade antibody (anti-mouse PD-1 or PD-L1, i.p. 6x 5mg/kg/mouse/injection; BioXcell), or treated in combination with mLOAd703 plus anti-PD-1 or mLOAd703 plus anti-PD-L1. Monotherapy with checkpoint blockade antibodies did not reduce tumor growth in this model. However, mLOAd703 reduced tumor growth as a monotherapy, but this reduction was even further enhanced in combination with both anti-PD-1 and anti-PD-L1 therapy.

In conclusion, mLOAd703 could infect B16 cells expressing CD46, leading to TMZ-CD40L and 4-1BBL transgene expression. In addition, infected tumor cells became more immunogenic and reduced molecules involved in metastasis. In vivo studies revealed that mLOAd703 therapy sensitized PD-1/PD-L1-resistant mice to checkpoint blockade therapy.

Citation Format: Jessica Wenthe, Sedigheh Naseri, Ann-Charlotte Hellström, Emma Eriksson, Angelica Loskog. CD40L/4-1BBL virotherapy enhances efficacy of checkpoint blockade therapy in a resistant melanoma model [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 4092.

Mebendazole-induced M1 polarisation of THP-1 macrophages may involve DYRK1B inhibition

OBJECTIVE

We recently showed that the anti-helminthic compound mebendazole (MBZ) has immunomodulating activity by inducing a M2 to M1 phenotype switch in monocyte/macrophage models. In the present study we investigated the potential role of protein kinases in mediating this effect.

RESULTS

MBZ potently binds and inhibits Dual specificity tyrosine-phosphorylation-regulated kinase 1B (DYRK1B) with a Kd and an IC50 of 7 and 360 nM, respectively. The specific DYRK1B inhibitor AZ191 did not mimic the cytokine release profile of MBZ in untreated THP-1 monocytes. However, in THP-1 cells differentiated into macrophages, AZ191 strongly induced a pro-inflammatory cytokine release pattern similar to MBZ and LPS/IFNγ. Furthermore, like MBZ, AZ191 increased the expression of the M1 marker CD80 and decreased the M2 marker CD163 in THP-1 macrophages. In this model, AZ191 also increased phospho-ERK activity although to a lesser extent compared to MBZ. Taken together, the results demonstrate that DYRK1B inhibition could, at least partly, recapitulate immune responses induced by MBZ. Hence, DYRK1B inhibition induced by MBZ may be part of the mechanism of action to switch M2 to M1 macrophages.

Altered profile of immune regulatory cells in the peripheral blood of lymphoma patients

BACKGROUND

Regulatory immune cells may modulate the lymphoma microenvironment and are of great interest due to the increasing prevalence of treatment with immunotherapies in lymphoma patients. The aim was to explore the composition of different immune regulatory cell subsets in the peripheral blood of newly diagnosed lymphoma patients in relation to treatment outcome.

METHODS

Forty-three newly diagnosed patients with lymphoma were included in the study; 24 with high-grade B-cell lymphoma (HGBCL) and 19 with classical Hodgkin lymphoma (cHL). Peripheral blood was prospectively collected and immune regulatory cells were identified by multi-color flow cytometry and analyzed in relation to healthy blood donors and clinical characteristics and outcome.

RESULTS

The percentage of CD3-positive T-cells was lower (p = 0.03) in the peripheral blood of lymphoma patients at diagnosis compared to healthy blood donors regardless of lymphoma subtype, although statistically, neither the percentage of monocytes (p = 0.2) nor the T-cell/monocyte ratio (p = 0.055) differed significantly. A significant decrease in the percentage of a subset of regulatory NK cells (CD7⁺/CD3^-/CD56^bright/CD16^dim/-) was identified in the peripheral blood of lymphoma patients compared to healthy blood donors (p = 0.003). Lymphoma patients also had more granulocytic myeloid-derived suppressor cells (MDSCs) (p = 0.003) compared to healthy blood donors, whereas monocytic MDSCs did not differ significantly (p = 0.07). A superior disease-free survival was observed for cHL patients who had an increase in the percentage of granulocytic MDSCs (p = 0.04).

CONCLUSIONS

An altered profile of immune cells in the peripheral blood with a decrease in T-cells and regulatory NK-cells was observed in newly diagnosed lymphoma patients. CHL patients with higher percentages of regulatory NK cells and higher percentages of granulocytic MDSCs might have a better outcome, although the number of patients was low.

Abstract A119: Combating primary and secondary checkpoint blockade resistance using immunostimulatory CD40L/4-1BBL-encoding oncolytic virotherapy for melanoma

In recent years, cancer immunotherapies significantly advanced the clinical management of metastatic melanoma. In particular, treatment with immune checkpoint inhibitors increased survival rates compared with standard therapy. However, not all patients benefit from checkpoint blockade. Primary treatment resistance is connected to poor T-cell infiltration in the tumors. This can be due to limited activation of antigen-presentation cells such as dendritic cells (DCs) and the high threshold of activating low-affinity T-cells that may respond to the tumor antigens. CD27 signaling in T-cells during activation lowers the T-cell receptor signaling threshold, which may be important to activate tumor-targeting T-cells. Secondary resistance to checkpoint blockade therapy includes loss of MHC-I on the tumor cells. Hence, inducing natural killer (NK) cell activation in parallel to antitumor T-cells may be crucial. LOAd703 was designed to optimize antitumor immune activation. LOAd703 is an oncolytic adenovirus (serotype Ad5/35) carrying two immunostimulatory transgenes; a trimerized membrane-bound CD40 ligand (TMZ-CD40L) and the full-length 4-1BB ligand (4-1BBL) (patent filed: PCT/EP2015/057489). The viral replication is restricted to tumor cells with a hyperphosphorylated retinoblastoma pathway due to a deletion in E1A, but transgenes are expressed under the control of a cytomegalovirus (CMV) promoter, which enables transgene expression even in the surrounding tumor microenvironment. Herein, we investigated LOAd703 in a melanoma model and its immunostimulatory effect on DC maturation to induce antigen-specific T-cell responses. LOAd703 infected the human melanoma cell line 526-mel and efficiently induced tumor cell death as evaluated by MTS viability assay. The viability of infected cells was reduced to 15% at 72 hours post infection compared to uninfected cells. Transgene expression of both TMZ-CD40L and 4-1BBL was confirmed by flow cytometry post infection. To evaluate the immunostimulatory capacity of LOAd703, immature DCs were differentiated from CD14+ monocytes using granulocyte-macrophage colony-stimulating factor and interleukin-4 and infected with virus. LOAd703-infected DCs upregulated the expression of maturation markers, such as CD83, CD86 and MHC molecules as analyzed by flow cytometry. Interestingly, CD70 that is required for CD27 stimuli of T-cells was highly upregulated on the DCs using LOAd703. Furthermore, the chemokine receptor CCR7 and the adhesion molecule ICAM-1 were increased upon LOAd703 infection, which are crucial for lymph node homing and the initiation of a systemic response. Next, the functional capacity of LOAd703-matured DCs to induce antigen-specific T-cell responses was assessed in a CMV model, in which CMV-peptide pulsed DCs are utilized to induce expansion of CMV-specific T-cells. LOAd703-matured DCs from CMV+ donors were pulsed with CMV-peptide and co-cultured with autologous peripheral blood mononuclear cells for 11 days. LOAd703-matured DCs were able to expand CMV-specific T-cells, but to a lower degree than the positive control Poly I:C matured DCs. However, the CMV-specific T-cells expanded from the positive control had higher expression of PD-1 compared to the LOAd703 group, indicating that LOAd703 leads to the expansion of less exhausted and potentially more functional T-cells. Moreover, LOAd703 also induced a massive expansion of NK cells, which is probably driven by 4-1BBL. In conclusion, LOAd703 killed human melanoma cells by oncolysis and induced the expression of TMZ-CD40L and 4-1BBL in infected cells. Furthermore, LOAd703 infection activated DCs to express costimulatory molecules including high levels of CD70 and CCR7, which in turn could promote the expansion of antigen-specific T-cells with low PD-1 expression, as well as the potent expansion of NK cells.

Citation Format: Jessica Wenthe, Mantas Šilanskas, Emma Eriksson, Angelica Loskog. Combating primary and secondary checkpoint blockade resistance using immunostimulatory CD40L/4-1BBL-encoding oncolytic virotherapy for melanoma [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A119.

IL-6 Signaling Blockade during CD40-Mediated Immune Activation Favors Antitumor Factors by Reducing TGF-β, Collagen Type I, and PD-L1/PD-1

IL-6 plays a role in cancer pathogenesis via its connection to proteins involved in the formation of desmoplastic stroma and to immunosuppression by driving differentiation of myeloid suppressor cells together with TGF-β. Inhibition of IL-6 signaling in the tumor microenvironment may, thus, limit desmoplasia and myeloid suppressor cell differentiation. CD40 signaling can further revert myeloid cell differentiation toward antitumor active phenotypes. Hence, the simultaneous use of IL-6 blockade with CD40 stimuli may tilt the tumor microenvironment to promote antitumor immune responses. In this paper, we evaluated the mechanisms of LOAd713, an oncolytic adenovirus designed to block IL-6R signaling and to provide myeloid cell activation via a trimerized membrane-bound isoleucine zipper (TMZ) CD40L. LOAd713-infected pancreatic cancer cells were killed by oncolysis, whereas infection of stellate cells reduced factors involved in stroma formation, including TGF-β-1 and collagen type I. Virus infection prevented IL-6/GM-CSF-mediated differentiation of myeloid suppressors, but not CD163 macrophages, whereas infection of dendritic cells led to upregulation of maturation markers, including CD83, CD86, IL-12p70, and IFN-γ. Further, IL-6R blockade prevented upregulation of programed death ligand 1 (PD-L1) and PD-1 on the stimulated dendritic cells. These results suggest that LOAd713 can kill infected tumor cells and has the capacity to affect the tumor microenvironment by stimulating stellate cells and myeloid suppressors with TMZ-CD40L and IL-6R blockade. Gene transfer of murine TMZ-CD40L prolonged survival in an animal model. LOAd713 may be an interesting therapeutic option for cancers connected to IL-6 signaling, such as pancreatic cancer.

Abstract B07: Immunostimulatory gene therapy enhances PD-1 blockade antibody therapy in experimental lung cancer

This study aims to evaluate if immunostimulatory gene therapy is a good enhancer of checkpoint blockade therapy. Lung cancer is a deadly disease responding poorly to conventional therapy. Checkpoint blockade antibodies inhibiting PD-1/PD-L1 signaling have shown significant clinical benefit. Nevertheless, there is still room for improving overall survival rates. Since the success of PD-1 blockade therapy prerequisites the presence of tumor-reactive T cells, we hypothesized that an activating immunotherapy with high potency to stimulate T cell responses would be an ideal candidate to combine with anti-PD-1 antibody treatment. LOAd703 is a replication-restricted adenovirus serotype 5/35. It is armed with two immunostimulatory transgenes, 4-1BB ligand (4-1BBL) and a trimerized, membrane-bound human CD40 ligand (TMZ-CD40L) (PCT/EP2015/057489). Both molecules are key co-stimulatory molecules in the dendritic cell (DC)/T cell synapse. The capacity of LOAd703 was tested using the lung cancer cell lines A549 and H727. Infected tumor cells were killed by oncolysis in a 72hr MTS viability assay with high dose virus (100MOI) which also translated into tumor control in a xenograft mouse model. In tumor cell co-culture with peripheral blood mononuclear cells (PBMCs) (Incucyte), the PBMCs were rapidly tolerized by the tumor microenvironment and did not proliferate, nor kill, the allogeneic tumor. Addition of anti-PD-1 antibody did not increase tumor cell apoptosis as a monotherapy. If OKT3/IL2 was added to the co-culture, apoptosis was confirmed in the cultures peaking at day 5. Combination of OKT3/IL2 with anti-PD-1 antibody significantly enhanced the effect. LOAd703 was added to tumor cell/PBMC co-cultures at a low MOI to delay oncolysis but allow transgene expression. LOAd703 rapidly induced caspase activation in the tumor cells, starting already at day 2 and the activity was continuously rising throughout the experiment. Combining LOAd703 with anti-PD-1 antibody significantly increased apoptosis induction of tumor cells. A control virus lacking immunostimulatory transgenes was less efficient. At endpoint, LOAd703 plus anti-PD-1 was twice as effective as OKT3/IL2 plus anti-PD-1. Immune cells were analyzed by flow cytometry and supernatants taken for cytokine analysis. The T cells were increased in the same groups as tumor cell killing was previously noted. IFNg, TNF, IL2 were all enhanced by LOAd703 and OKT3/IL2. The LOAd703 virus does not infect murine cells since it targets human CD46. However, murine B cells can take up the virus by another route albeit with poor efficacy. Nevertheless, the murine A20 B cell lymphoma was used as a surrogate syngeneic model to test the ability of LOAd703 to potentiate aPD-1 therapy. In line with in vitro data, LOAd703 could enhance in vivo tumor control of anti-PD-1 therapy. IFNg and TNF were enhanced in serum of combination animals. In conclusion, LOAd703 is a potent stimulator of T cell responses and potentiates the effect of aPD-1 therapy. LOAd703 is currently in clinical phase I investigation prior initiating combination studies in suitable indications such as lung cancer.

Citation Format: Jessica Wenthe, Emma Eriksson, Ann-Charlotte Hellström, Angelica Loskog. Immunostimulatory gene therapy enhances PD-1 blockade antibody therapy in experimental lung cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B07.

A Phase I/IIa Trial Using CD19-Targeted Third-Generation CAR T Cells for Lymphoma and Leukemia

PURPOSE

The chimeric antigen receptor (CAR) T-cell therapy has been effective for patients with CD19⁺ B-cell malignancies. Most studies have investigated the second-generation CARs with either CD28 or 4-1BB costimulatory domains in the CAR receptor. Here, we describe the first clinical phase I/IIa trial using third-generation CAR T cells targeting CD19 to evaluate safety and efficacy.

PATIENTS AND METHODS

Fifteen patients with B-cell lymphoma or leukemia were treated with CAR T cells. The patients with lymphoma received chemotherapy during CAR manufacture and 11 of 15 were given low-dose cyclophosphamide and fludarabine conditioning prior to CAR infusion. Peripheral blood was sampled before and at multiple time points after CAR infusion to evaluate the persistence of CAR T cells and for immune profiling, using quantitative PCR, flow cytometry, and a proteomic array.

RESULTS

Treatment with third-generation CAR T cells was generally safe with 4 patients requiring hospitalization due to adverse reactions. Six of the 15 patients had initial complete responses [4/11 lymphoma and 2/4 acute lymphoblastic leukemia (ALL)], and 3 of the patients with lymphoma were in remission at 3 months. Two patients are still alive. Best predictor of response was a good immune status prior to CAR infusion with high IL12, DC-Lamp, Fas ligand, and TRAIL. Responding patients had low monocytic myeloid-derived suppressor cells (MDSCs; CD14⁺CD33⁺HLA^-DR^-) and low levels of IL6, IL8, NAP3, sPDL1, and sPDL2.

CONCLUSIONS

Third-generation CARs may be efficient in patients with advanced B-cell lymphoproliferative malignancy with only modest toxicity. Immune profiling pre- and posttreatment can be used to find response biomarkers.

Mebendazole stimulates CD14+ myeloid cells to enhance T-cell activation and tumour cell killing

Mebendazole (MBZ) was recently shown to induce a tumor suppressive M1 phenotype in THP-1 monocytes and macrophages. In the present study the immune effects of MBZ was further investigated using human peripheral blood mononuclear cells (PBMCs) co-cultured with tumour cells. The Biomap platform was used to screen for biomarkers induced from MBZ exposed co-cultures of T-cell receptor activated PBMCs, HT29 colon cancer cells and either human fibroblasts or human umbilical vein endothelial cells (HUVEC) cells. In these co-culture systems MBZ at 0.3-10 μM induced significant increases in TNFα and IFNγ indicating immune stimulation. PBMC cultures alone were subsequently tested for activation status and only in PBMCs activated by CD3/IL2 stimulation and MBZ, at a clinically achievable concentration, was able to increase PBMC clustering and release of pro-inflammatory IFNγ, TNFα, IL6 and IL1β cytokines. Moreover, when PBMC cultures were functionally tested for immune cell killing of lung cancer A549NucLightRed cells, MBZ significantly increased tumour cell apoptosis and reduced the number of surviving tumour cells. This effect was dependent on the presence of CD14 monocytes/macrophages in the co-culture. In summary, MBZ potentiated the immune stimulatory and anticancer effects of anti-CD3/IL2 activated PBMCs which could be relevant to explain the anticancer activity of MBZ observed in the clinic.

Differences in Expansion Potential of Naive Chimeric Antigen Receptor T Cells from Healthy Donors and Untreated Chronic Lymphocytic Leukemia Patients

Introduction

Therapy with chimeric antigen receptor T (CART) cells for hematological malignancies has shown promising results. Effectiveness of CART cells may depend on the ratio of naive (T_N) vs. effector (T_E) T cells, T_N cells being responsible for an enduring antitumor activity through maturation. Therefore, we investigated factors influencing the T_N/T_E ratio of CART cells.

Materials and methods

CART cells were generated upon transduction of peripheral blood mononuclear cells with a CD19.CAR-CD28-CD137zeta third generation retroviral vector under two different stimulating culture conditions: anti-CD3/anti-CD28 antibodies adding either interleukin (IL)-7/IL-15 or IL-2. CART cells were maintained in culture for 20 days. We evaluated 24 healthy donors (HDs) and 11 patients with chronic lymphocytic leukemia (CLL) for the composition of cell subsets and produced CART cells. Phenotype and functionality were tested using flow cytometry and chromium release assays.

Results

IL-7/IL-15 preferentially induced differentiation into T_N, stem cell memory (T_SCM: naive CD27+ CD95+), CD4+ and CXCR3+ CART cells, while IL-2 increased effector memory (T_EM), CD56+ and CD4+ T regulatory (T_Reg) CART cells. The net amplification of different CART subpopulations derived from HDs and untreated CLL patients was compared. Particularly the expansion of CD4+ CART_N cells differed significantly between the two groups. For HDs, this subtype expanded >60-fold, whereas CD4+ CART_N cells of untreated CLL patients expanded less than 10-fold. Expression of exhaustion marker programmed cell death 1 on CART_N cells on day 10 of culture was significantly higher in patient samples compared to HD samples. As the percentage of malignant B cells was expectedly higher within patient samples, an excessive amount of B cells during culture could account for the reduced expansion potential of CART_N cells in untreated CLL patients. Final T_N/T_E ratio stayed <0.3 despite stimulation condition for patients, whereas this ratio was >2 in samples from HDs stimulated with IL-7/IL-15, thus demonstrating efficient CART_N expansion.

Conclusion

Untreated CLL patients might constitute a challenge for long-lasting CART effects in vivo since only a low number of T_N among the CART product could be generated. Depletion of malignant B cells before starting CART production might be considered to increase the T_N/T_E ratio within the CART product.

An anergic immune signature in the tumor microenvironment of classical Hodgkin lymphoma is associated with inferior outcome

OBJECTIVE

The classical Hodgkin lymphoma (cHL) tumor microenvironment shows an ongoing inflammatory response consisting of varying degrees of infiltrating eosinophils, mast cells, macrophages, regulatory T lymphocytes (Tregs), and activated lymphocytes surrounding the malignant cells. Herein, different immune signatures are characterized and correlated with treatment outcome.

METHODS

Tumor-infiltrating leukocytes were phenotyped in biopsies from 459 patients with cHL. Time to progression (TTP) (primary progression, relapse, or death from cHL) and overall survival were analyzed using Cox proportional hazards regression.

RESULTS

The leukocyte infiltration in the microenvironment was highly diverse between patients and was categorized in 4 immune signatures (active, anergic, innate, or mixed). A high proportion of Tregs (anergic) resulted in shorter TTP (median 12.9-year follow-up) in age-adjusted analyses (hazard ratio = 1.82; 95% confidence interval 1.05-3-15). Epstein-Barr virus (EBV)-positive cases had higher proportions of macrophages and activated lymphocytes than EBV negative, but neither of those leukocytes predicted prognosis.

CONCLUSIONS

Abundant Tregs (anergic signature) indicate a shorter TTP, particularly in younger patients. This is probably due to a reduced ability of the immune system to attack the tumor cells. Our data warrant further investigation if these suggested immune signatures could predict outcome of immunotherapy such as immune checkpoint inhibitors.

Local irradiation does not enhance the effect of immunostimulatory AdCD40L gene therapy combined with low dose cyclophosphamide in melanoma patients

Background

AdCD40L is an immunostimulatory gene therapy under evaluation for advanced melanoma, including ocular melanoma. Herein, we present the final data of a Phase I/IIa trial using AdCD40L alone or in combination with low dose cyclophosphamide +/- radiation therapy.

Methods

AdCD40L is a replication-deficient adenovirus carrying the gene for CD40 ligand (CD40L). Twenty-four patients with advanced melanoma were enrolled and treated with AdCD40L monotherapy, or combined with cyclophosphamide +/- single fraction radiotherapy. The patients were monitored for 10 weeks using immunological and radiological evaluations and thereafter for survival.

Results

AdCD40L treatment was safe and well tolerated both alone and in combination with cyclophosphamide as well as local radiotherapy. Four out of twenty-four patients had >1 year survival. Addition of cyclophosphamide was beneficial but adding radiotherapy did not further extend survival. High initial plasma levels of IL12 and MIP3b correlated to overall survival, whereas IL8 responses post-treatment correlated negatively with survival. Interestingly, antibody reactions to the virus correlated negatively with post IL6 and pre IL1b levels in blood.

Conclusions

AdCD40L was safely administered to patients and effect was improved by cyclophosphamide but not by radiotherapy. Immune activation profile at baseline may predict responders better than shortly after treatment.

Abstract 3662: Activation of CD40 while inhibiting IL6/STAT3 using oncolytic viruses induces mature DCs with high cytokine production but blocks PDL1 expression

The tumor microenvironment (TME) consists of tumor cells and stroma, including fibroblasts, blood vessels, immune cells and extracellular matrix. The TME supports tumor progression, metastasis as well as resistance to cancer therapeutics. In pancreatic cancer, the TME is dense due to overproduction of collagen and the tumor is infiltrated with suppressive myeloid cells such as M2 macrophages and myeloid suppressor cells. One key regulator of myeloid cells is CD40, a receptor expressed on a variety of cell types. CD40/CD40L signaling results in production of cytokines and chemokines by myeloid cells but also endothelial and epithelial cells to alert the immune system of immediate danger. 4-1BB is expressed by lymphocytes and dendritic cells (DCs). Stimulation via 4-1BBL drives lymphocyte expansion and regulates memory formation. IL6 signaling leads to STAT3 phosphorylation in myeloid cells and tumor cells leading to suppressive phenotypes, tumor proliferation, and angiogenesis. Further, STAT3 signaling enhances production of TGFb, which in turn leads to overexpression of collagen. We have constructed a family of oncolytic adenoviruses (LOAd) activating the CD40, 4-1BB and/or inhibiting IL6 signaling. The LOAd viruses (-, 700, 703, 713) were investigated for their capacity to activate human monocyte-derived DCs as well as their effect on pancreatic tumor cells and stroma (fibroblastic stellate cells, endothelial cells) using flow cytometry, MTS assay and ProSeek Proteomics. The LOAd viruses expressing a trimerized CD40L, 4-1BBL and/or a scFv IL6R showed efficient oncolysis of tumor cells but primary stellate cells were unaffected. However, stellate cells reduced tumor-promoting factors such as FGF5, PlGF, amphiregulin, Gal3, TGFb and collagen type I. Dendritic cells increased costimulators, cytokines as well as chemokines but PDL1 was not expressed when IL6/STAT3 was blocked. Infected endothelial cells upregulated receptors important for lymphocyte transmigration (ICAM, VCAM and E-Selectin). Taken together, our data demonstrates that it is possible to utilize oncolytic adenoviruses to spark immune activation at the same time changing biological processes via STAT3 blockade and/or CD40/4-1BB pathway activation to reduce factors that promotes tumor progression.

Citation Format: Emma Eriksson, Ioanna Milenova, Jessica Wenthe, Anna Dimberg, Rafael Moreno, Gustav Ullenhag, Ramon Alemany, Angelica Loskog. Activation of CD40 while inhibiting IL6/STAT3 using oncolytic viruses induces mature DCs with high cytokine production but blocks PDL1 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3662. doi:10.1158/1538-7445.AM2017-3662

Shaping the Tumor Stroma and Sparking Immune Activation by CD40 and 4-1BB Signaling Induced by an Armed Oncolytic Virus

Purpose: Pancreatic cancer is a severe indication with short expected survival despite surgery and/or combination chemotherapeutics. Checkpoint blockade antibodies are approved for several cancer indications, but pancreatic cancer has remained refractory. However, there are clinical data suggesting that stimulation of the CD40 pathway may be of interest for these patients. Oncolytic viruses armed with immunostimulatory genes represent an interesting approach. Herein, we present LOAd703, a designed adenovirus armed with trimerized CD40L and 4-1BBL that activates the CD40 and 4-1BB pathways, respectively. As many cells in the tumor stroma, including stellate cells and the infiltrating immune cells, express CD40 and some 4-1BB, we hypothesize that LOAd703 activates immunity and simultaneously modulates the biology of the tumor stroma.Experimental Design: Tumor, stellate, endothelial, and immune cells were infected by LOAd703 and investigated by flow cytometry, proteomics, and functional analyses.Results: LOAd703-infected pancreatic cell lines were killed by oncolysis, and the virus was more effective than standard-of-care gemcitabine. In in vivo xenograft models, LOAd703 efficiently reduced established tumors and could be combined with gemcitabine for additional effect. Infected stellate and tumor cells reduced factors that promote tumor growth (Spp-1, Gal-3, HGF, TGFβ and collagen type I), while chemokines were increased. Molecules involved in lymphocyte migration were upregulated on infected endothelial cells. Dendritic cells were robustly stimulated by LOAd703 to produce costimulators, cytokines and chemokines, and such DCs potently expanded both antigen-specific T cells and NK cells.Conclusions: LOAd703 is a potent immune activator that modulates the stroma to support antitumor responses. Clin Cancer Res; 23(19); 5846-57. ©2017 AACR.

The anticancer effect of mebendazole may be due to M1 monocyte/macrophage activation via ERK1/2 and TLR8-dependent inflammasome activation

Mebendazole (MBZ), a drug commonly used for helminitic infections, has recently gained substantial attention as a repositioning candidate for cancer treatment. However, the mechanism of action behind its anticancer activity remains unclear. To address this problem, we took advantage of the curated MBZ-induced gene expression signatures in the LINCS Connectivity Map (CMap) database. The analysis revealed strong negative correlation with MEK/ERK1/2 inhibitors. Moreover, several of the most upregulated genes in response to MBZ exposure were related to monocyte/macrophage activation. The MBZ-induced gene expression signature in the promyeloblastic HL-60 cell line was strongly enriched in genes involved in monocyte/macrophage pro-inflammatory (M1) activation. This was subsequently validated using MBZ-treated THP-1 monocytoid cells that demonstrated gene expression, surface markers and cytokine release characteristic of the M1 phenotype. At high concentrations MBZ substantially induced the release of IL-1β and this was further potentiated by lipopolysaccharide (LPS). At low MBZ concentrations, cotreatment with LPS was required for MBZ-stimulated IL-1β secretion to occur. Furthermore, we show that the activation of protein kinase C, ERK1/2 and NF-kappaB were required for MBZ-induced IL-1β release. MBZ-induced IL-1β release was found to be dependent on NLRP3 inflammasome activation and to involve TLR8 stimulation. Finally, MBZ induced tumor-suppressive effects in a coculture model with differentiated THP-1 macrophages and HT29 colon cancer cells. In summary, we report that MBZ induced a pro-inflammatory (M1) phenotype of monocytoid cells, which may, at least partly, explain MBZ's anticancer activity observed in animal tumor models and in the clinic.

Low interleukin-2 concentration favors generation of early memory T cells over effector phenotypes during chimeric antigen receptor T-cell expansion

BACKGROUND

Adoptive T-cell therapy offers new options for cancer treatment. Clinical results suggest that T-cell persistence, depending on T-cell memory, improves efficacy. The use of interleukin (IL)-2 for in vitro T-cell expansion is not straightforward because it drives effector T-cell differentiation but does not promote the formation of T-cell memory. We have developed a cost-effective expansion protocol for chimeric antigen receptor (CAR) T cells with an early memory phenotype.

METHODS

Lymphocytes were transduced with third-generation lentiviral vectors and expanded using CD3/CD28 microbeads. The effects of altering the IL-2 supplementation (0-300 IU/mL) and length of expansion (10-20 days) on the phenotype of the T-cell products were analyzed.

RESULTS

High IL-2 levels led to a decrease in overall generation of early memory T cells by both decreasing central memory T cells and augmenting effectors. T memory stem cells (T_SCM, CD95⁺CD45RO^-CD45RA⁺CD27⁺) were present variably during T-cell expansion. However, their presence was not IL-2 dependent but was linked to expansion kinetics. CD19-CAR T cells generated in these conditions displayed in vitro antileukemic activity. In summary, production of CAR T cells without any cytokine supplementation yielded the highest proportion of early memory T cells, provided a 10-fold cell expansion and the cells were functionally potent.

DISCUSSION

The number of early memory T cells in a T-cell preparation can be increased by simply reducing the amount of IL-2 and limiting the length of T-cell expansion, providing cells with potentially higher in vivo performance. These findings are significant for robust and cost-effective T-cell manufacturing.

Preclinical Evaluation of AdVince, an Oncolytic Adenovirus Adapted for Treatment of Liver Metastases from Neuroendocrine Cancer

Cancer immunotherapy is becoming a cornerstone in the clinical care of cancer patients due to the breakthrough trials with immune checkpoint blockade antibodies and chimeric antigen receptor T cells. The next breakthrough in cancer immunotherapy is likely to be oncolytic viruses engineered to selectively kill tumor cells and deceive the immune system to believe that the tumor is a foreign entity that needs to be eradicated. We have developed AdVince, an oncolytic adenovirus for treatment of liver metastases from neuroendocrine tumor (NET). AdVince includes the gene promoter from human chromogranin A for selective replication in neuroendocrine cells, miR122 target sequences for reduced liver toxicity, and a cell-penetrating peptide in the capsid for increased infectivity of tumor cells and optimized spread within tumors. This paper describes the preclinical evaluation of AdVince on freshly isolated human gastrointestinal NET cells resected from liver metastases and freshly isolated human hepatocytes as well as in fresh human blood. AdVince selectively replicates in and kills NET cells. Approximately 73-fold higher concentration of AdVince is needed to induce a similar level of cytotoxicity in NET cells as in hepatocytes. AdVince did not activate complement or induce considerable amount of proinflammatory cytokines or chemokines in human blood. The data presented herein indicate that AdVince can be safely evaluated in a phase I/IIa clinical trial for patients with liver-dominant NET.

Gemcitabine reduces MDSCs, tregs and TGFβ-1 while restoring the teff/treg ratio in patients with pancreatic cancer

Background

Cancer immunotherapy can be potentiated by conditioning regimens such as cyclophosphamide, which reduces the level of regulatory T cells (tregs). However, myeloid suppressive cells are still remaining. Accordingly to previous reports, gemcitabine improves immune status of cancer patients. In this study, the role of gemcitabine was further explored to map its immunological target cells and molecules in patients with pancreatic cancer.

Methods

Patient blood was investigated by flow cytometry and cytokine arrays at different time points during gemcitabine treatment.

Results

The patients had elevated myeloid-derived suppressor cells (MDSCs), and Tregs at diagnosis. Myeloid cells were in general decreased by gemcitabine. The granulocytic MDSCs were significantly reduced while monocytic MDSCs were not affected. In vitro, monocytes responding to IL-6 by STAT3 phosphorylation were prevented to respond in gemcitabine medium. However, gemcitabine could not prevent STAT3 phosphorylation in IL-6-treated tumor cell lines. TGFβ-1 was significantly reduced after only one treatment and continued to decrease. At the same time, the effector T cell:Treg ratio was increased and the effector T cells had full proliferative capacity during the gemcitabine cycle. However, after a resting period, the level of suppressor cells and TGFβ-1 had been restored showing the importance of continuous conditioning.

Conclusions

Gemcitabine regulates the immune system in patients with pancreatic cancer including MDSCs, Tregs and molecules such as TGFβ-1 but does not hamper the ability of effector lymphocytes to expand to stimuli. Hence, it may be of high interest to use gemcitabine as a conditioning strategy together with immunotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1037-z) contains supplementary material, which is available to authorized users.

Abstract 1474: A novel oncolytic adenovirus expressing tumor microenvironment modulators that activates myeloid cells, lymphocytes and endothelial cells

Immunotherapy is becoming a cornerstone in cancer treatment of many indications. So far, pancreatic cancer has shown little response to so called checkpoint blockade antibodies. However, animal data suggests that activating immunotherapies releases the effect of checkpoint blockade also in pancreatic cancer. The tumor microenvironment (TEM) supports the growth of the tumor cells and consists of stroma cells, fibroblasts, blood vessels and immune cells. In some tumor lesions, such as those in pancreatic cancer, the TEM is dense and comprises most of the lesion. The TEM regulates immune activity via its high content of M2 macrophages, myeloid derived suppressor cells and T regulatory cells. Further, the dysfunctional blood vessels in lesions are not optimal for recruiting lymphocytes. With these aspects in mind, LOAd703 was developed. LOAd703 is an oncolytic adenovirus carrying TEM modulators.

LOAd703 was constructed from the ICOVIR system of oncolytic adenoviruses in which replication depends on a dysfunctional, hyperphosphorylated retinoblastoma pathway. The genome was further altered by removing E3-6.7K and gp19K, changing the serotype 5 fiber to a serotype 35 fiber to target CD46 expressed by most tumors, as well as by adding a CMV-driven transgene cassette with the human transgenes for TMZ-CD40L and 4-1BBL. Hence, the transgenes will be expressed in both tumor and stroma while oncolysis is initiated in the tumor cells. We demonstrate herein that LOAd703 infection of a panel of pancreatic cancer cell lines efficiently induced tumor cell death within 48-72 hrs post infection while LOAd703 infection of dendritic cells demonstrated an increased maturation of myeloid cells including dendritic cells (DCs). These DCs could in turn potently activate and promote expansion of both T- and NK cells. Further, LOAd703 infection of endothelial cells (HUVEC) induced upregulation of molecules involved in lymphocyte attachment, rolling and transmigration. In conclusion, LOAd703 is a novel oncolytic virus that targets both the tumor and its TME and a clinical trial is underway to elucidate its effect in pancreatic cancer.

Citation Format: Angelica Loskog, Emma Eriksson, Ioanna Milenova, Rafael Moreno, Ramon Alemany. A novel oncolytic adenovirus expressing tumor microenvironment modulators that activates myeloid cells, lymphocytes and endothelial cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1474.

Optimization of the MB49 mouse bladder cancer model for adenoviral gene therapy

Bladder cancer is regarded as a promising candidate for innovative therapies in the field of immune and gene therapy. In this paper, we present the subcutaneous, metastatic and a novel orthotopic model of murine MB49 bladder cancer in C57BL/6 mice. We further show the potential of using adenoviral vectors together with different transduction enhancers to augment in vivo gene delivery. Finally, we present candidate genes for tumour detection, therapy or targeting.

The MB49 tumour grew rapidly in mice. The subcutaneous model allowed for tumour detection within a week and the possibility to monitor growth rate on a day-by-day basis. Injection of MB49 cells intravenously into the tail vein gave rise to lung metastases within 16 days, while instillation of tumour cells into pretreated bladders led to a survival time of 20–40 days. Adenoviral vectors can be used as a vehicle for gene transfer to the bladder. By far, the most potent transduction enhancer was Clorpactin, also known as oxychlorosene. Last, we show that MB49 cells express tumour-associated antigens like bladder cancer-4, prostate stem cell antigen and six-transmembrane epithelial antigen of the prostate.

Given the possibility for efficient genetic modification of the bladder and the presence of known tumour antigens, the MB49 models can be used in innovative ways to explore immunogene therapy.