Viral Vectors Expressing Interleukin 2 for Cancer Immunotherapy

Interleukin 2 (IL-2) plays a crucial role in T cell growth and survival, enhancing the cytotoxic activity of natural killer and cytotoxic T cells and thus functioning as a versatile master proinflammatory anticancer cytokine. The FDA has approved IL-2 cytokine therapy for the treatment of metastatic melanoma and metastatic renal cell carcinoma. However, IL-2 therapy has significant constraints, including a short serum half-life, low tumor accumulation, and life-threatening toxicities associated with high doses. Oncolytic viruses (OVs) offer a promising option for cancer immunotherapy, selectively targeting and destroying cancer cells while sparing healthy cells. Numerous studies have demonstrated the successful delivery of IL-2 to the tumor microenvironment without compromising safety using OVs such as vaccinia, Sendai, parvo, Newcastle disease, tanapox, and adenoviruses. Additionally, by engineering OVs to coexpress IL-2 with other anticancer transgenes, the immune properties of IL-2 can be further enhanced. Preclinical and clinical studies have shown promising antitumor effects of IL-2-expressing viral vectors, either alone or in combination with other anticancer therapies. This review summarizes the therapeutic potential of IL-2-expressing viral vectors and their antitumor mechanisms of action.

Syrian hamster as an ideal animal model for evaluation of cancer immunotherapy

Cancer immunotherapy (CIT) has emerged as an exciting new pillar of cancer treatment. Although benefits have been achieved in individual patients, the overall response rate is still not satisfactory. To address this, an ideal preclinical animal model for evaluating CIT is urgently needed. Syrian hamsters present similar features to humans with regard to their anatomy, physiology, and pathology. Notably, the histological features and pathological progression of tumors and the complexity of the tumor microenvironment are equivalent to the human scenario. This article reviews the current tumor models in Syrian hamster and the latest progress in their application to development of tumor treatments including immune checkpoint inhibitors, cytokines, adoptive cell therapy, cancer vaccines, and oncolytic viruses. This progress strongly advocates Syrian hamster as an ideal animal model for development and assessment of CIT for human cancer treatments. Additionally, the challenges of the Syrian hamster as an animal model for CIT are also discussed.

Development of a Syrian hamster anti-PD-L1 monoclonal antibody enables oncolytic adenoviral immunotherapy modelling in an immunocompetent virus replication permissive setting

Introduction

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer, but preclinical testing of hypotheses such as combination therapies has been complicated, in part due to species incompatibility issues. For example, one of few known permissive animal models for oncolytic adenoviruses is the Syrian hamster, for which an ICI, mainly an anti-PD-L1 monoclonal antibody (mAb) was not previously available. In this study, we developed an anti-Syrian hamster PD-L1 mAb to enable the evaluation of safety and efficacy, when combining anti-PD-L1 with an oncolytic adenovirus encoding tumour necrosis factor alpha (TNFα) and interleukin-2 (IL-2) (Ad5/3-E2F-D24-hTNFα-IRES-hIL-2 or TILT-123).

Methods

Recombinant Syrian hamster PD-L1 was expressed and mice immunized for mAb formation using hybridoma technology. Clonal selection through binding and functional studies in vitro, in silico and in vivo identified anti-PD-L1 clone 11B12-1 as the primary mAb candidate for immunotherapy modelling. The oncolytic virus (OV) and ICI combination approach was then evaluated using 11B12-1 and TILT-123 in a Syrian hamster model of pancreatic ductal adenocarcinoma (PDAC).

Results

Supernatants from hybridoma parent subclone 11B12B4 provided the highest positive PD-L1 signal, on Syrian hamster PBMCs and three cancer cell lines (HT100, HapT1 and HCPC1). In vitro co-cultures revealed superior immune modulated profiles of cell line matched HT100 tumour infiltrating lymphocytes when using subclones of 7G2, 11B12 and 12F1. Epitope binning and epitope prediction using AlphaFold2 and ColabFold revealed two distinct functional epitopes for clone 11B12-1 and 12F1-1. Treatment of Syrian hamsters bearing HapT1 tumours, with 11B12-1 induced significantly better (p<0.05) tumour growth control than isotype control by day 12. 12F1-1 did not induce significant tumour growth control. The combination of 11B12-1 with oncolytic adenovirus TILT-123 improved tumour growth control further, when compared to monotherapy (p<0.05) by day 26.

Conclusions

Novel Syrian hamster anti-PD-L1 clone 11B12-1 induces tumour growth control in a hamster model of PDAC. Combining 11B12-1 with oncolytic adenovirus TILT-123 improves tumour growth control further and demonstrates good safety and toxicity profiles.

Protection is not always a good thing: The immune system's impact on gene therapy

There are many clinical trials underway for the development of gene therapies, and some have resulted in gene therapy products being commercially approved already. Significant progress was made to develop safer and more effective strategies to deliver and regulate genetic products. An unsolved aspect is the immune system, which can affect the efficiency of gene therapy in different ways. Here we present an overview of approved gene therapy products and the immune response elicited by gene delivery systems. These include responses against the vector or its content after delivery and against the product of the corrected gene. Strategies to overcome the hurdles include hiding the vector or/and the transgene product from the immune system and hiding the immune system from the vector/transgene product. Combining different strategies, such as patient screening and intelligent vector design, gene therapy is set to make a difference in the life of patients with severe genetic diseases.

Roles for macrophage-polarizing interleukins in cancer immunity and immunotherapy

Macrophages are the most abundant and one of the most critical cells of tumor immunity. They provide a bridge between innate and adaptive immunity through releasing cytokines into the tumor microenvironment (TME). A number of interleukin (IL) cytokine family members is involved in shaping the final phenotype of macrophages toward either a classically-activated pro-inflammatory M1 state with anti-tumor activity or an alternatively-activated anti-inflammatory M2 state with pro-tumor activity. Shaping TME macrophages toward the M1 phenotype or recovering this phenotypic state may offer a promising therapeutic approach in patients with cancer. Here, we focus on the impact of macrophage-polarizing ILs on immune cells and IL-mediated cellular cross-interactions within the TME. The key aim of this review is to define therapeutic schedules for addressing ILs in cancer immunotherapy based on their multi-directional impacts in such a milieu. Gathering more knowledge on this area is also important for defining adverse effects related to cytokine therapy and addressing them for reinforcing the efficacy of immunotherapy against cancer.

Local therapy with an engineered oncolytic adenovirus enables antitumor response in non-injected melanoma tumors in mice treated with aPD-1

Intratumoral immunotherapies are entering clinical use but concerns remain regarding their effects on non-injected tumors. Here, we studied the impact of local treatment with an adenovirus coding for TNFa and IL-2 on systemic antitumor response in animals receiving aPD-1 (anti-programmed cell death protein 1) therapy. Using bilateral murine melanoma models, we tested systemic tumor response to combined therapy with anti-PD-1 and an adenovirus coding for TNFa and IL-2 ("virus"). Virus was given intratumorally (to one of the two tumors only) and aPD-1 monoclonal antibody systemically. We evaluated both tumors' response to treatment, overall survival, metastasis development, and immunological mechanisms involved with response. Consistent tumor control was observed in both injected and non-injected tumors, including complete response in all treated animals receiving aPD-1+ virus therapy. Mechanistically, virus injections enabled potent effector lymphocyte response locally, with systemic effects in non-injected tumors facilitated by aPD-1 treatment. Moreover, adenovirus therapy demonstrated immunological memory formation. Virus therapy was effective in preventing metastasis development. Local treatment with TNFa and IL-2 coding adenovirus enhanced systemic response to aPD-1 therapy, by re-shaping the microenvironment of both injected and non-injected tumors. Therefore, our pre-clinical data support the rationale for a trial utilizing a combination of aPD-1 plus virus for the treatment of human cancer.

Oncolytic Adenovirus Coding for a Variant Interleukin 2 (vIL-2) Cytokine Re-Programs the Tumor Microenvironment and Confers Enhanced Tumor Control

The notion of developing variants of the classic interleukin 2 (IL-2) cytokine has emerged from the limitations observed with the systemic use of human IL-2 in the clinic: severe adverse events accompanied by low therapeutic response rate in treated patients. Modifications made in the IL-2 receptor-binding structure leads to preferential binding of IL-2 variant cytokine to receptors on effector anti-tumor lymphocytes over T regulatory (TReg) cells. Because of their inherent immunogenicity, oncolytic adenoviruses are useful for expression of immunomodulatory molecules in tumors, for induction of a pro-inflammatory state in the tumor microenvironment. In the present study, we constructed an adenovirus coding for an IL-2 variant (vIL-2) protein, Ad5/3-E2F-d24-vIL2. Functionality of the new virus was tested in vitro, and anti-tumor efficacy and mechanism of action studies were performed in immunocompetent hamsters bearing pancreatic tumors. Ad5/3-E2F-d24-vIL2 treatment elicited efficient anti-tumor response, with 62.5% monotherapy complete response. Moreover, it promoted substantial repression of genes associated with myeloid cells mediated immunosuppression (CD11b, ARG1, CD206). This was seen in conjunction with upregulation of genes associated with tumor-infiltrating lymphocyte (TIL) cytotoxicity (CD3G, SAP, PRF1, GZMM and GZMK). In summary, Ad5/3-E2F-d24-vIL2 demonstrates therapeutic potential by counteracting immunosuppression and in efficiently coordinating lymphocytes mediated anti-tumor response in immunosuppressive tumors. Thus, Ad5/3-E2F-d24-vIL2 is a promising candidate for translation into clinical trials in human immunosuppressive solid tumors.

Oncolytic Adenovirus ORCA-010 Activates Proinflammatory Myeloid Cells and Facilitates T Cell Recruitment and Activation by PD-1 Blockade in Melanoma

Immune checkpoint inhibitors have advanced the treatment of melanoma. Nevertheless, a majority of patients are resistant, or develop resistance, to immune checkpoint blockade, which may be related to prevailing immune suppression by myeloid regulatory cells in the tumor microenvironment (TME). ORCA-010 is a novel oncolytic adenovirus that selectively replicates in, and lyses, cancer cells. We previously showed that ORCA-010 can activate melanoma-exposed conventional dendritic cells (cDCs). To study the effect of ORCA-010 on melanoma-conditioned macrophage development, we used an in vitro co-culture model of human monocytes with melanoma cell lines. We observed a selective survival and polarization of monocytes into M2-like macrophages (CD14⁺CD80^-CD163⁺) in co-cultures with cell lines that expressed macrophage colony-stimulating factor. Oncolysis of these melanoma cell lines, effected by ORCA-010, activated the resulting macrophages and converted them to a more proinflammatory state, evidenced by higher levels of PD-L1, CD80, and CD86 and an enhanced capacity to prime allogenic T cells and induce a type-1 T cell response. To assess the effect of ORCA-010 on myeloid subset distribution and activation in vivo, ORCA-010 was intratumorally injected and tested for T cell activation and recruitment in the human adenovirus nonpermissive B16-OVA mouse melanoma model. While systemic PD-1 blockade in this model in itself did not modulate myeloid or T cell subset distribution and activation, when it was preceded by i.t. injection of ORCA-010, this induced an increased rate and activation state of CD8α⁺ cDC1, both in the TME and in the spleen. Observed increased rates of activated CD8⁺ T cells, expressing CD69 and PD-1, were related to both increased CD8α⁺ cDC1 rates and M1/M2 shifts in tumor and spleen. In conclusion, the myeloid modulatory properties of ORCA-010 in melanoma, resulting in recruitment and activation of T cells, could enhance the antitumor efficacy of PD-1 blockade.

Cytokine-Coding Oncolytic Adenovirus TILT-123 Is Safe, Selective, and Effective as a Single Agent and in Combination with Immune Checkpoint Inhibitor Anti-PD-1

Oncolytic viruses provide a biologically multi-faceted treatment option for patients who cannot be cured with currently available treatment options. We constructed an oncolytic adenovirus, TILT-123, to support T-cell therapies and immune checkpoint inhibitors in solid tumors. Adenoviruses are immunogenic by nature, are easy to produce in large quantities, and can carry relatively large transgenes. They are the most commonly used gene therapy vectors and are well tolerated in patients. TILT-123 expresses two potent cytokines, tumor necrosis factor alpha and interleukin-2, to stimulate especially the T-cell compartment in the tumor microenvironment. Before entering clinical studies, the safety and biodistribution of TILT-123 was studied in Syrian hamsters and in mice. The results show that TILT-123 is safe in animals as monotherapy and in combination with an immune checkpoint inhibitor anti-PD-1. The virus treatment induces acute changes in circulating immune cell compartments, but the levels return to normal by the middle of the treatment period. The virus is rapidly cleared from healthy tissues, and it does not cause damage to vital organs. The results support the initiation of a phase 1 dose-escalation trial, where melanoma patients receiving a tumor-infiltrating lymphocyte therapy are treated with TILT-123 (NCT04217473).

Tumor microenvironment remodeling by an engineered oncolytic adenovirus results in improved outcome from PD-L1 inhibition

Checkpoint inhibitors have revolutionized cancer therapy and validated immunotherapy as an approach. Unfortunately, responses are seen in a minority of patients. Our objective is to use engineered adenoviruses designed to increase lymphocyte trafficking and cytokine production at the tumor, to assess if they increase the response rate to checkpoint inhibition, as these features have been regarded as predictive for the responses. When Ad5/3-E2F-d24-hTNFa-IRES-hIL2 (an oncolytic adenovirus coding for TNFa and IL-2, also known as TILT-123) and checkpoint inhibitors were used together in fresh urological tumor histocultures, a significant shift toward immune activity (not only tumor necrosis alpha and interleukin-2 but also interferon gamma and granzyme B) and increased T-cell trafficking signals (CXCL10) was observed. In vivo, our viruses enabled an anti-PD-L1 (a checkpoint inhibitor) delivering complete responses in all the treated animals (hazard ratios versus anti-PD-L1 alone 0.057 [0.007; 0.451] or virotherapy alone 0.067 [0.011; 0.415]). To conclude, when an engineered oncolytic adenovirus was utilized to modify the tumor microenvironment towards what meta-analyses have pointed as predictive markers for checkpoint inhibitory therapy, the response to them increased synergistically. Of note, key findings were confirmed in fresh patient-derived tumor explants.

Development of oncolytic virotherapy: from genetic modification to combination therapy

Oncolytic virotherapy (OVT) is a novel form of immunotherapy using natural or genetically modified viruses to selectively replicate in and kill malignant cells. Many genetically modified oncolytic viruses (OVs) with enhanced tumor targeting, antitumor efficacy, and safety have been generated, and some of which have been assessed in clinical trials. Combining OVT with other immunotherapies can remarkably enhance the antitumor efficacy. In this work, we review the use of wild-type viruses in OVT and the strategies for OV genetic modification. We also review and discuss the combinations of OVT with other immunotherapies.

Vitamin D aggravates breast cancer by inducing immunosuppression in the tumor bearing mouse

The aim of this approach is to test the effects and related mechanism of vitamin D (VD) treatment on the outcomes of breast cancer. BALB/c mice were injected with 4T1 breast cancer cell suspension. The test group was treated with VD reagent. The survival and tumor size of mice were observed. The proliferation of 4T1 in vitro was detected by MTS analysis. The changes of immune parameters and microenvironment in mice were evaluated by flow cytometry and real-time RT-PCR. Our results demonstrate that VD administration caused a decline in survival time and raising the volume of tumor, the decreasing numbers of CD3⁺CD4⁺ T, CD3⁺CD8⁺ T and CD4⁺T-bet⁺IFN-γ⁺ Th1 cells and transcriptions of T-bet and IFN-γ, an increasing number of myeloid-derived suppressor cells and transcription of TGF-β. Our data suggest that the routine clinical application of any strategies targeting VD status for breast cancer therapy is deserved serious consideration.

Modulation of the tumor microenvironment with an oncolytic adenovirus for effective T-cell therapy and checkpoint inhibition

Despite exciting proof-of-concept data mediated by adoptive T-cell transfer and checkpoint blockade, major challenges imposed by the tumor microenvironment restrict clinical benefits to a minority of patients with advanced or metastatic solid malignancies. While employment of toxic pre- and postconditioning regimens to circumvent the inefficacy of T-cell transfer presents a fundamental problem for heavily pretreated cancer patients, for checkpoint blockade, the main issue relates to low single-agent response rates. To overcome these hurdles, combination therapy with oncolytic adenovirus is becoming an attractive solution given multiple intrinsic modulatory effects on the intratumoral immune compartment, engineering capabilities and safety profile. Here, we provide a short overview on the tumor microenvironmental challenges in solid tumors, and how oncolytic adenoviruses can counteract these barriers. Finally, the immunotherapeutic potential of oncolytic adenoviruses will be discussed in the context of clinical experience with adoptive T-cell therapy and immune checkpoint inhibitors.

Oncolytic adenoviruses: a game changer approach in the battle between cancer and the immune system

INTRODUCTION

Oncolytic adenoviruses are among the most studied oncolytic viruses because of their tumor selectivity, safety, and transgene-delivery capability. With a growing number of different immunotherapies against cancer, the extraordinary immunogenicity of the adenovirus has emerged as a differentiating strength. Enabling T-cell related therapies with oncolytic adenoviruses appears a promising approach due to its inherent ability to elicit responses from the adaptive immune compartment.

AREAS COVERED

These viruses have successfully enhanced both adoptive T-cell therapies and immune-checkpoint therapies. Oncolytic viruses induce several effects at the tumor and on the systemic level that help to circumvent current limitations of T-cells and related therapies, such as T-cell trafficking, tumor immune suppressivity and antigen spreading

EXPERT OPINION

Taking into account the multitude of possibilities of treating cancer with immunotherapies, learning to optimize the combinations and administration strategies of these drugs, could lead to durable responses in patients with currently incurable cancers.

Abscopal Effect in Non-injected Tumors Achieved with Cytokine-Armed Oncolytic Adenovirus

Cancer treatment with local administration of armed oncolytic viruses could potentially induce systemic antitumor effects, or the abscopal effect, as they self-amplify in tumors, induce danger signaling, and promote tumor-associated antigen presentation. In this study, oncolytic adenovirus coding for human tumor necrosis factor alpha (TNF-α) and interleukin-2 (IL-2) Ad5/3-E2F-d24-hTNF-α-IRES-hIL-2 (also known as [a.k.a.] TILT-123) provoked antitumor efficacy in tumors that were injected with Ad5/3-E2F-d24-hTNF-α-IRES-hIL-2 and those that were left non-injected in the same animal. Importantly, the virus was able to travel to distant tumors. To dissect the effects of oncolysis and cytokines, we studied replication-incompetent viruses in mice. Systemic antitumor effects were similar in both models, highlighting the importance of the arming device. The cytokines induced positive changes in immune cell infiltrates and induced the expression of several immune-reaction-related genes in tumors. In addition, Ad5/3-E2F-d24-hTNF-α-IRES-hIL-2 was able to increase homing of adoptively transferred tumor-infiltrating lymphocytes into both injected and non-injected tumors, possibly mediated through chemokine expression. In summary, local treatment with Ad5/3-E2F-d24-hTNF-α-IRES-hIL-2 resulted in systemic antitumor efficacy by inducing immune cell infiltration and trafficking into both treated and untreated tumors. Moreover, the oncolytic adenovirus platform had superior systemic effects over replication-deficient vector through spreading into distant tumors.

Adenovirus Coding for Interleukin-2 and Tumor Necrosis Factor Alpha Replaces Lymphodepleting Chemotherapy in Adoptive T Cell Therapy

Lymphodepleting preconditioning with high-dose chemotherapy is commonly used to increase the clinical efficacy of adoptive T cell therapy (ACT) strategies, however, with severe toxicity for patients. Conversely, oncolytic adenoviruses are safe and, when engineered to express interleukin-2 (IL-2) and tumor necrosis factor alpha (TNF-α), they can achieve antitumor immunomodulatory effects similar to lymphodepletion. Therefore, we compare the safety and efficacy of such adenoviruses with a cyclophosphamide- and fludarabine-containing lymphodepleting regimen in the setting of ACT. Human adenovirus (Ad5/3-E2F-D24-hTNF-α-IRES-hIL-2; TILT-123) replication was studied using a Syrian hamster pancreatic tumor model (HapT1) infused with tumor-infiltrating lymphocytes (TILs). Using the oncolytic virus instead of lymphodepletion resulted in superior efficacy and survival. Immune cells responsive to TNF-α IL-2 were studied using an immunocompetent mouse melanoma model (B16.OVA) infused with ovalbumin-specific T (OT-I) cells. Here, the adenovirus approach improved tumor control together with increased intratumoral Th1 cytokine levels and infiltration of CD8+ T cells and CD86+ dendritic cells. Similar to humans, lymphodepleting preconditioning caused severe cytopenias, systemic inflammation, and damage to vital organs. Toxicity was minimal in adenovirus- and OT-I-treated mice. These findings demonstrate that ACT can be effectively facilitated by cytokine-coding adenovirus without requiring lymphodepletion, a rationale being clinically investigated.

TNFa and IL-2 armed adenoviruses enable complete responses by anti-PD-1 checkpoint blockade

Releasing the patient's immune system against their own malignancy by the use of checkpoint inhibitors is delivering promising results. However, only a subset of patients currently benefit from them. One major limitation of these therapies relates to the inability of T cells to detect or penetrate into the tumor resulting in unresponsiveness to checkpoint inhibition. Virotherapy is an attractive tool for enabling checkpoint inhibitors as viruses are naturally recognized by innate defense elements which draws the attention of the immune system. Besides their intrinsic immune stimulating properties, the adenoviruses used here are armed to express tumor necrosis factor alpha (TNFa) and interleukin-2 (IL-2). These cytokines result in immunological danger signaling and multiple appealing T-cell effects, including trafficking, activation and propagation. When these viruses were injected into B16.OVA melanoma tumors in animals concomitantly receiving programmed cell-death protein 1 (PD-1) blocking antibodies both tumor growth control (p < 0.0001) and overall survival (p < 0.01) were improved. In this set-up, the addition of adoptive cell therapy with OT-I lymphocytes did not increase efficacy further. When virus injections were initiated before antibody treatment in a prime-boost approach, 100% of tumors regressed completely and all mice survived. Viral expression of IL2 and TNFa altered the cytokine balance in the tumor microenvironment towards Th1 and increased the intratumoral proportion of CD8+ and conventional CD4+ T cells. These preclinical studies provide the rationale and schedule for a clinical trial where oncolytic adenovirus coding for TNFa and IL-2 (TILT-123) is used in melanoma patients receiving an anti-PD-1 antibody.