Immunological effects of low-dose cyclophosphamide in cancer patients treated with oncolytic adenovirus

Oncolytic Adenovirus for the Targeting of Paclitaxel-Resistant Breast Cancer Stem Cells

Adjuvant systemic therapies effectively reduce the risk of breast cancer recurrence and metastasis, but therapy resistance can develop in some patients due to breast cancer stem cells (BCSCs). Oncolytic adenovirus (OAd) represents a promising therapeutic approach as it can specifically target cancer cells. However, its potential to target BCSCs remains unclear. Here, we evaluated a Cox-2 promoter-controlled, Ad5/3 fiber-modified OAd designed to encode the human sodium iodide symporter (hNIS) in breast cancer models. To confirm the potential of OAds to target BCSCs, we employed BCSC-enriched estrogen receptor-positive (ER+) paclitaxel-resistant (TaxR) cells and tumorsphere assays. OAd-hNIS demonstrated significantly enhanced binding and superior oncolysis in breast cancer cells, including ER+ cells, while exhibiting no activity in normal mammary epithelial cells. We observed improved NIS expression as the result of adenovirus death protein deletion. OAd-hNIS demonstrated efficacy in targeting TaxR BCSCs, exhibiting superior killing and hNIS expression compared to the parental cells. Our vector was capable of inhibiting tumorsphere formation upon early infection and reversing paclitaxel resistance in TaxR cells. Importantly, OAd-hNIS also destroyed already formed tumorspheres seven days after their initiation. Overall, our findings highlight the promise of OAd-hNIS as a potential tool for studying and targeting ER+ breast cancer recurrence and metastasis.

Reshaping the tumor microenvironment of cold soft-tissue sarcomas with oncolytic viral therapy: a phase 2 trial of intratumoral JX-594 combined with avelumab and low-dose cyclophosphamide

Most soft-tissue sarcomas (STS) exhibit an immunosuppressive tumor microenvironment (TME), leading to resistance against immune checkpoint inhibitors (ICIs) and limited therapeutic response. Preclinical data suggest that oncolytic viral therapy can remodel the TME, facilitating T cell accumulation and enhancing the immunogenicity of these tumors.We conducted the METROMAJX, a phase II clinical trial, to investigate the combination of JX-594, an oncolytic vaccinia virus engineered for selective tumor cell replication, with metronomic cyclophosphamide and the PD-L1 inhibitor avelumab in patients with advanced, 'cold' STS, characterized by an absence of tertiary lymphoid structures. The trial employed a two-stage Simon design. JX-594 was administered intratumorally at a dose of 1.109 pfu every 2 weeks for up to 4 intra-tumoral administrations. Cyclophosphamide was given orally at 50 mg twice daily in a week-on, week-off schedule, and avelumab was administered at 10 mg/kg biweekly. The primary endpoint was the 6-month non-progression rate.Fifteen patients were enrolled, with the most frequent toxicities being grade 1 fatigue and fever. Fourteen patients were assessable for efficacy analysis. At 6 months, only one patient remained progression-free, indicating that the trial did not meet the first stage endpoint of Simon's design. Analysis of sequential tissue biopsies and plasma samples revealed an increase in CD8 density and upregulation of immune-related protein biomarkers, including CXCL10.Intra-tumoral administration of JX-594 in combination with cyclophosphamide and avelumab is safe and capable of modulating the TME in cold STS. However, the limited efficacy observed warrants further research to define the therapeutic potential of oncolytic viruses, particularly in relation to specific histological subtypes of STS.

Anticancer Activity of Measles-Mumps-Rubella MMR Vaccine Viruses against Glioblastoma

BACKGROUND

Oncolytic viruses (OVs) have been utilized since 1990s for targeted cancer treatment. Our study examined the Measles-Mumps-Rubella (MMR) vaccine's cancer-killing potency against Glioblastoma (GBM), a therapy-resistant, aggressive cancer type.

METHODOLOGY

We used GBM cell lines, primary GBM cells, and normal mice microglial cells, to assess the MMR vaccine's efficacy through cell viability, cell cycle analysis, intracellular viral load via RT-PCR, and Transmission Electron Microscopy (TEM).

RESULTS

After 72 h of MMR treatment, GBM cell lines and primary GBM cells exhibited significant viability reduction compared to untreated cells. Conversely, normal microglial cells showed only minor changes in viability and morphology. Intracellular viral load tests indicated GBM cells' increased sensitivity to MMR viruses compared to normal cells. The cell cycle study also revealed measles and mumps viruses' crucial role in cytopathic effects, with the rubella virus causing cell cycle arrest.

CONCLUSION

Herein the reported results demonstrate the anti-cancer activity of the MMR vaccine against GBM cells. Accordingly, the MMR vaccine warrants further study as a potential new tool for GBM therapy and relapse prevention. Therapeutic potential of the MMR vaccine has been found to be promising in earlier studies as well.

Efficacy of Systemically Administered Retargeted Oncolytic Herpes Simplex Viruses-Clearance and Biodistribution in Naïve and HSV-Preimmune Mice

We investigated the anticancer efficacy, blood clearance, and tissue biodistribution of systemically administered retargeted oncolytic herpes simplex viruses (ReHVs) in HSV-naïve and HSV-preimmunized (HSV-IMM) mice. Efficacy was tested against lung tumors formed upon intravenous administration of cancer cells, a model of metastatic disease, and against subcutaneous distant tumors. In naïve mice, HER2- and hPSMA-retargeted viruses, both armed with mIL-12, were highly effective, even when administered to mice with well-developed tumors. Efficacy was higher for combination regimens with immune checkpoint inhibitors. A significant amount of infectious virus persisted in the blood for at least 1 h. Viral genomes, or fragments thereof, persisted in the blood and tissues for days. Remarkably, the only sites of viral replication were the lungs of tumor-positive mice and the subcutaneous tumors. No replication was detected in other tissues, strengthening the evidence of the high cancer specificity of ReHVs, a property that renders ReHVs suitable for systemic administration. In HSV-IMM mice, ReHVs administered at late times failed to exert anticancer efficacy, and the circulating virus was rapidly inactivated. Serum stability and in vivo whole blood stability assays highlighted neutralizing antibodies as the main factor in virus inactivation. Efforts to deplete mice of the neutralizing antibodies are ongoing.

Metronomic chemotherapy as a potential partner of immune checkpoint inhibitors for metastatic colorectal cancer treatment

The use of immune checkpoint inhibitors (ICIs) in clinical practice for the treatment of metastatic colorectal cancer (mCRC) is currently limited to patients with deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H), which comprise less than 5% of all mCRC cases. Combining ICIs with anti-angiogenic inhibitors, which modulate the tumor microenvironment, may reinforce and synergize the anti-tumor immune responses of ICIs. In mCRCs, combinations of pembrolizumab and lenvatinib have shown good efficacy in early phase trials. These results suggest the potential utility of immune modulators as partners in combination treatment with ICIs in immunologically cold microsatellite stable, as well as hot dMMR/MSI-H tumors. Unlike conventional pulsatile maximum tolerated dose chemotherapy, low-dose metronomic (LDM) chemotherapy recruits immune cells and normalizes vascular-immune crosstalk, similar to anti-angiogenic drugs. LDM chemotherapy mostly modulates the tumor stroma rather than directly killing tumor cells. Here, we review the mechanism of LDM chemotherapy in terms of immune modulation and its potential as a combination partner with ICIs for the treatment of patients with mCRC tumors, most of which are immunologically cold.

Metronomic Chemotherapy: Anti-Tumor Pathways and Combination with Immune Checkpoint Inhibitors

Increasing evidence pinpoints metronomic chemotherapy, a frequent and low dose drug administration with no prolonged drug-free intervals, as a potential tool to fight certain types of cancers. The primary identified targets of metronomic chemotherapy were the tumor endothelial cells involved in angiogenesis. After this, metronomic chemotherapy has been shown to efficiently target the heterogeneous population of tumor cells and, more importantly, elicit the innate and adaptive immune system reverting the "cold" to "hot" tumor immunologic phenotype. Although metronomic chemotherapy is primarily used in the context of a palliative setting, with the development of new immunotherapeutic drugs, a synergistic therapeutic role of the combined metronomic chemotherapy and immune checkpoint inhibitors has emerged at both the preclinical and clinical levels. However, some aspects, such as the dose and the most effective scheduling, still remain unknown and need further investigation. Here, we summarize what is currently known of the underlying anti-tumor effects of the metronomic chemotherapy, the importance of the optimal therapeutic dose and time-exposure, and the potential therapeutic effect of the combined administration of metronomic chemotherapy with checkpoint inhibitors in preclinical and clinical settings.

The emerging field of oncolytic virus-based cancer immunotherapy

Oncolytic viruses (OVs) provide novel and promising therapeutic options for patients with cancers resistant to traditional therapies. Natural or genetically modified OVs are multifaceted tumor killers. They directly lyse tumor cells while sparing normal cells, and indirectly potentiate antitumor immunity by releasing antigens and activating inflammatory responses in the tumor microenvironment. However, some limitations, such as limited penetration of OVs into tumors, short persistence, and the host antiviral immune response, are impeding the broad translation of oncolytic virotherapy into the clinic. If these challenges can be overcome, combination therapies, such as OVs plus immune checkpoint blockade (ICB), chimeric antigen receptor (CAR) T cells, or CAR natural killer (NK) cells, may provide powerful therapeutic platforms in the clinic.

Randomized phase 2 trial of intravenous oncolytic virus JX-594 combined with low-dose cyclophosphamide in patients with advanced soft-tissue sarcoma

JX-594 is an oncolytic vaccinia virus genetically modified to replicate selectively in tumor cells. Metronomic chemotherapy has shown preclinical synergy with oncolytic viruses. We report here the results of the METROMAJX which is a randomized phase II clinical trial investigating the combination of JX-594 combined with metronomic cyclophosphamide (arm 1) or metronomic cyclophosphamide (arm 2) in patients with advanced STS. A two-stage Simon design was used. JX-594 was administered intra-venously at the dose 1.109 every 2 weeks for the first 3 injections and then every 3 weeks. Cyclophosphamide was given orally at the dose of 50 mg BID 1 week on 1 week off. The primary endpoint was the 6-month non progression rate. 20 patients were included (arm 1:15, arm 2:5). The two most frequent toxicities were grade 1 fatigue and fever and grade 2 fatigue and grade 2 lymphopenia in arms 1 and 2, respectively. In arm 1, 12 patients were assessable for the efficacy analysis. None of them were progression-free at 6 months indicating that the first stage of the Simon's design was not satisfied. One patient out 4 assessable for efficacy was progression-free at 6 months in arm 2. High throughput analysis of sequential plasma samples revealed an upregulation of protein biomarkers reflecting immune induction such as CXCL10 and soluble CD8 antigen in arm 1. Systemic treatment with JX-594 is safe in patients with advanced STS. Further investigations are needed to improve immune response to oncolytic viruses and define their therapeutic potential in patients with STS.

Recombinant Oncolytic Adenovirus Combined with Cyclophosphamide Induces Synergy in the Treatment of Breast Cancer in vitro and in vivo

Purpose

Oncolytic virus therapy has gradually become an integral approach in cancer treatment. We explored the therapeutic effects of the combination of a dual cancer-selective anti-tumor recombinant adenovirus (Ad-Apoptin-hTERTp-E1a) and cyclophosphamide on breast cancer cells.

Methods

The inhibition of MCF-7 and MDA-MB-231 breast cancer cells by Ad-Apoptin-hTERTp-E1a (Ad-VT), cyclophosphamide, and Ad-VT + Cyclophosphamide was investigated using the CCK-8 assay. The combination index (CI) was calculated using CalcuSyn software to determine the best combination based on the inhibition rates of the different treatment combinations. The CCK-8 assay and crystal violet staining were used to detect the cytotoxicity of the combined Ad-VT and cyclophosphamide in breast cancer cells and breast epithelial cells. Subsequently, Hoechst staining, annexin V flow cytometry, and JC-1 staining were used to analyze the inhibitory pathway of Ad-VT plus cyclophosphamide on breast cancer cells. Cell migration and invasion of breast cancer cells were assessed using the cell-scratch and Transwell assays. The anti-tumor effects of different treatment groups in a tumor-bearing nude mouse model also were analyzed.

Results

The treatment combination of Ad-VT (40 MOI) and cyclophosphamide (400 µM) significantly inhibited MCF-7 and MDA-MB-231 cells and reduced the toxicity of cyclophosphamide in normal cells. Ad-VT primarily induced breast cancer cell apoptosis through the endogenous apoptotic pathway. Apoptosis was significantly increased after treatment with Ad-VT plus cyclophosphamide. The combination significantly inhibited the migration and invasion of MCF-7 and MDA-MB-231 cells. The in vivo experiments demonstrated that exposure to Ad-VT plus cyclophosphamide significantly inhibited tumor growth and extended the survival time of the nude mice.

Conclusion

Ad-VT plus cyclophosphamide reduced toxicity and exhibited increased efficacy in treating breast cancer cells.

The Nitrogen Mustards

The nitrogen mustards are powerful cytotoxic and lymphoablative agents and have been used for more than 60 years. They are employed in the treatment of cancers, sarcomas, and hematologic malignancies. Cyclophosphamide, the most versatile of the nitrogen mustards, also has a place in stem cell transplantation and the therapy of autoimmune diseases. Adverse effects caused by the nitrogen mustards on the central nervous system, kidney, heart, bladder, and gonads remain important issues. Advances in analytical techniques have facilitated the investigation of the pharmacokinetics of the nitrogen mustards, especially the oxazaphosphorines, which are prodrugs requiring metabolic activation. Enzymes involved in the metabolism of cyclophosphamide and ifosfamide are very polymorphic, but a greater understanding of the pharmacogenomic influences on their activity has not yet translated into a personalized medicine approach. In addition to damaging DNA, the nitrogen mustards can act through other mechanisms, such as antiangiogenesis and immunomodulation. The immunomodulatory properties of cyclophosphamide are an area of current exploration. In particular, cyclophosphamide decreases the number and activity of regulatory T cells, and the interaction between cyclophosphamide and the intestinal microbiome is now recognized as an important factor. New derivatives of the nitrogen mustards continue to be assessed. Oxazaphosphorine analogs have been synthesized in attempts to both improve efficacy and reduce toxicity, with varying degrees of success. Combinations of the nitrogen mustards with monoclonal antibodies and small-molecule targeted agents are being evaluated. SIGNIFICANCE STATEMENT: The nitrogen mustards are important, well-established therapeutic agents that are used to treat a variety of diseases. Their role is continuing to evolve.

Senecavirus A as an Oncolytic Virus: Prospects, Challenges and Development Directions

Oncolytic viruses have the capacity to selectively kill infected tumor cells and trigger protective immunity. As such, oncolytic virotherapy has become a promising immunotherapy strategy against cancer. A variety of viruses from different families have been proven to have oncolytic potential. Senecavirus A (SVA) was the first picornavirus to be tested in humans for its oncolytic potential and was shown to penetrate solid tumors through the vascular system. SVA displays several properties that make it a suitable model, such as its inability to integrate into human genome DNA and the absence of any viral-encoded oncogenes. In addition, genetic engineering of SVA based on the manipulation of infectious clones facilitates the development of recombinant viruses with improved therapeutic indexes to satisfy the criteria of safety and efficacy regulations. This review summarizes the current knowledge and strategies of genetic engineering for SVA, and addresses the current challenges and future directions of SVA as an oncolytic agent.

Advances in Immunotherapies for Gliomas

PURPOSE OF REVIEW

Immunotherapy-based treatment of glioblastoma has been challenging because of the tumor's limited neoantigen profile and weakly immunogenic composition. This article summarizes the current clinical trials underway by evaluating the leading immunotherapy paradigms, the encountered barriers, and the future directions needed to overcome such tumor evasion.

RECENT FINDINGS

A limited number of phase III trials have been completed for checkpoint inhibitor, vaccine, as well as gene therapies, and have been unable to show improvement in survival outcomes. Nevertheless, these trials have also shown these strategies to be safe and promising with further adaptations. Further large-scale studies for chimeric antigen receptors T cell therapies and viral therapies are anticipated. Many current trials are broadening the number of antigens targeted and modulating the microtumor environment to abrogate early mechanisms of resistance. Future GBM treatment will also likely require synergistic effects by combination regimens.

A novel oral metronomic chemotherapy provokes tumor specific immunity resulting in colon cancer eradication in combination with anti-PD-1 therapy

In this study, we investigated the immune-modulating effects of a novel metronomic chemotherapy (MCT) featuring combined oral oxaliplatin (OXA) and pemetrexed (PMX) for colon cancer. OXA and PMX were ionically complexed with lysine derivative of deoxycholic acid (DCK), and incorporated into nanoemulsions or colloidal dispersions, yielding OXA/DCK-NE and PMX/DCK-OP, respectively, to improve their oral bioavailabilities. MCT was not associated with significant lymphotoxicity whereas the maximum tolerated dose (MTD) afforded systemic immunosuppression. MCT was associated with more immunogenic cell death and tumor cell MHC-class I expression than was MTD. MCT improved the tumor antigen presentation of dendritic cells and increased the number of functional T cells in the tumor. MCT also helped to enhance antigen-specific memory responses both locally and systemically. By combining MCT with anti-programmed cell death protein-1 (αPD-1) therapy, the tumor volume was suppressed by 97.85 ± 84.88% compared to the control, resulting in a 95% complete response rate. Upon re-challenge, all tumor-free mice rejected secondary tumors, indicating the induction of a tumor specific memory response. Thus, MCT using an OXA and PMX combination, together with αPD-1, successfully treated colon cancer by activating both innate and adaptive immune cells and elicited tumor-specific long-term immune memory while avoiding toxicity caused by MTD treatment.

Clinical Trials of Oncolytic Viruses in Breast Cancer

Breast cancer is the second most common kind of cancer worldwide and oncolytic viruses may offer a new treatment approach. There are three different types of oncolytic viruses used in clinical trials; (i) oncolytic viruses with natural anti-neoplastic properties; (ii) oncolytic viruses designed for tumor-selective replication; (iii) oncolytic viruses modified to activate the immune system. Currently, fourteen different oncolytic viruses have been investigated in eighteen published clinical trials. These trials demonstrate that oncolytic viruses are well tolerated and safe for use in patients and display clinical activity. However, these trials mainly studied a small number of patients with different advanced tumors including some with breast cancer. Future trials should focus on breast cancer and investigate optimal routes of administration, occurrence of neutralizing antibodies, viral gene expression, combinations with other antineoplastic therapies, and identify subtypes that are particularly suitable for oncolytic virotherapy.

A systematic analysis on the clinical safety and efficacy of onco-virotherapy

Several onco-virotherapy candidates have been developed and clinically evaluated for the treatment of cancer, and several are approved for clinical use. In this systematic review we explored the clinical impact of onco-virotherapy compared to other cancer therapies by analyzing factors such as trial design, patient background, therapy design, delivery strategies, and study outcomes. For this purpose, we retrieved clinical studies from three platforms: ClinicalTrials.gov, PubMed, and EMBASE. We found that most studies were performed in patients with advanced and metastatic tumors, using a broad range of genetically engineered vectors and mainly administered intratumorally. Therapeutic safety was the most frequently assessed outcome, while relatively few studies focused on immunological antitumor responses. Moreover, only 59 out of 896 clinical studies were randomized controlled trials reporting comparative data. This systemic review thus reveals the need of more, and better controlled, clinical studies to increase our understanding on the application of onco-virotherapy either as a single treatment or in combination with other cancer immunotherapies.

The Evolution and Future of Targeted Cancer Therapy: From Nanoparticles, Oncolytic Viruses, and Oncolytic Bacteria to the Treatment of Solid Tumors

While many classes of chemotherapeutic agents exist to treat solid tumors, few can generate a lasting response without substantial off-target toxicity despite significant scientific advancements and investments. In this review, the paths of development for nanoparticles, oncolytic viruses, and oncolytic bacteria over the last 20 years of research towards clinical translation and acceptance as novel cancer therapeutics are compared. Novel nanoparticle, oncolytic virus, and oncolytic bacteria therapies all start with a common goal of accomplishing therapeutic drug activity or delivery to a specific site while avoiding off-target effects, with overlapping methodology between all three modalities. Indeed, the degree of overlap is substantial enough that breakthroughs in one therapeutic could have considerable implications on the progression of the other two. Each oncotherapeutic modality has accomplished clinical translation, successfully overcoming the potential pitfalls promising therapeutics face. However, once studies enter clinical trials, the data all but disappears, leaving pre-clinical researchers largely in the dark. Overall, the creativity, flexibility, and innovation of these modalities for solid tumor treatments are greatly encouraging, and usher in a new age of pharmaceutical development.

Harnessing the Immune System to Fight Multiple Myeloma

Multiple myeloma (MM) is a heterogeneous plasma cell malignancy differing substantially in clinical behavior, prognosis, and response to treatment. With the advent of novel therapies, many patients achieve long-lasting remissions, but some experience aggressive and treatment refractory relapses. So far, MM is considered incurable. Myeloma pathogenesis can broadly be explained by two interacting mechanisms, intraclonal evolution of cancer cells and development of an immunosuppressive tumor microenvironment. Failures in isotype class switching and somatic hypermutations result in the neoplastic transformation typical of MM and other B cell malignancies. Interestingly, although genetic alterations occur and evolve over time, they are also present in premalignant stages, which never progress to MM, suggesting that genetic mutations are necessary but not sufficient for myeloma transformation. Changes in composition and function of the immune cells are associated with loss of effective immune surveillance, which might represent another mechanism driving malignant transformation. During the last decade, the traditional view on myeloma treatment has changed dramatically. It is increasingly evident that treatment strategies solely based on targeting intrinsic properties of myeloma cells are insufficient. Lately, approaches that redirect the cells of the otherwise suppressed immune system to take control over myeloma have emerged. Evidence of utility of this principle was initially established by the observation of the graft-versus-myeloma effect in allogeneic stem cell-transplanted patients. A variety of new strategies to harness both innate and antigen-specific immunity against MM have recently been developed and intensively tested in clinical trials. This review aims to give readers a basic understanding of how the immune system can be engaged to treat MM, to summarize the main immunotherapeutic modalities, their current role in clinical care, and future prospects.

Glioblastoma multiforme (GBM): An overview of current therapies and mechanisms of resistance

Glioblastoma multiforme (GBM) is a WHO grade IV glioma and the most common malignant, primary brain tumor with a 5-year survival of 7.2%. Its highly infiltrative nature, genetic heterogeneity, and protection by the blood brain barrier (BBB) have posed great treatment challenges. The standard treatment for GBMs is surgical resection followed by chemoradiotherapy. The robust DNA repair and self-renewing capabilities of glioblastoma cells and glioma initiating cells (GICs), respectively, promote resistance against all current treatment modalities. Thus, durable GBM management will require the invention of innovative treatment strategies. In this review, we will describe biological and molecular targets for GBM therapy, the current status of pharmacologic therapy, prominent mechanisms of resistance, and new treatment approaches. To date, medical imaging is primarily used to determine the location, size and macroscopic morphology of GBM before, during, and after therapy. In the future, molecular and cellular imaging approaches will more dynamically monitor the expression of molecular targets and/or immune responses in the tumor, thereby enabling more immediate adaptation of tumor-tailored, targeted therapies.

The Multifaceted Role of Macrophages in Oncolytic Virotherapy

One of the cancer hallmarks is immune evasion mediated by the tumour microenvironment (TME). Oncolytic virotherapy is a form of immunotherapy based on the application of oncolytic viruses (OVs) that selectively replicate in and induce the death of tumour cells. Virotherapy confers reciprocal interaction with the host’s immune system. The aim of this review is to explore the role of macrophage-mediated responses in oncolytic virotherapy efficacy. The approach was to study current scientific literature in this field in order to give a comprehensive overview of the interactions of OVs and macrophages and their effects on the TME. The innate immune system has a central influence on the TME; tumour-associated macrophages (TAMs) generally have immunosuppressive, tumour-supportive properties. In the context of oncolytic virotherapy, macrophages were initially thought to predominantly contribute to anti-viral responses, impeding viral spread. However, macrophages have now also been found to mediate transport of OV particles and, after TME infiltration, to be subjected to a phenotypic shift that renders them pro-inflammatory and tumour-suppressive. These TAMs can present tumour antigens leading to a systemic, durable, adaptive anti-tumour immune response. After phagocytosis, they can recirculate carrying tissue-derived proteins, which potentially enables the monitoring of OV replication in the TME. Their role in therapeutic efficacy is therefore multifaceted, but based on research applying relevant, immunocompetent tumour models, macrophages are considered to have a central function in anti-cancer activity. These novel insights hold important clinical implications. When optimised, oncolytic virotherapy, mediating multifactorial inhibition of cancer immune evasion, could contribute to improved patient survival.

Combining Oncolytic Viruses and Small Molecule Therapeutics: Mutual Benefits

The focus of treating cancer with oncolytic viruses (OVs) has increasingly shifted towards achieving efficacy through the induction and augmentation of an antitumor immune response. However, innate antiviral responses can limit the activity of many OVs within the tumor and several immunosuppressive factors can hamper any subsequent antitumor immune responses. In recent decades, numerous small molecule compounds that either inhibit the immunosuppressive features of tumor cells or antagonize antiviral immunity have been developed and tested for. Here we comprehensively review small molecule compounds that can achieve therapeutic synergy with OVs. We also elaborate on the mechanisms by which these treatments elicit anti-tumor effects as monotherapies and how these complement OV treatment.

Phase II and biomarker study of programmed cell death protein 1 inhibitor nivolumab and metronomic cyclophosphamide in paediatric relapsed/refractory solid tumours: Arm G of AcSé-ESMART, a trial of the European Innovative Therapies for Children With Cancer Consortium

PURPOSE

AcSé-ESMART is a European multicentre, proof-of-concept multiarm phase I/II platform trial in paediatric patients with relapsed/refractory cancer. Arm G assessed the activity and safety of nivolumab in combination with metronomic cyclophosphamide +/- irradiation.

EXPERIMENTAL DESIGN

Following a Phase II Simon two-stage design, nivolumab was administered intravenously at 3 mg/kg every 2 weeks of a 28-day cycle, oral cyclophosphamide at 25 mg/m2 twice a day, 1 week on/1 week off. The primary endpoint was objective response rate. Irradiation/radioablation of primary tumour or metastasis could be administered as per physician's choice. Biomarker evaluation was performed by tumour immunohistochemistry, whole exome and RNA sequencing, and immunophenotyping of peripheral blood by flow cytometry.

RESULTS

Thirteen patients were treated with a median age of 15 years (range: 5.5-19.4). The main histologies were high-grade glioma, neuroblastoma, and desmoplastic small round cell tumour (DSRCT). The safety profile was similar to those of single-agent nivolumab, albeit haematologic toxicity, mainly lymphocytopenia, was commonly reported with the addition of cyclophosphamide +/- irradiation. Two patients with DSRCT and ependymoma presented unconfirmed partial response and prolonged disease stabilisation. Low mutational load with modest intratumour CD3+ T-cell infiltration and immunosuppressive tumour microenvironment were observed in the tumour samples. Under combined treatment, no positive modulation of circulating T cells was displayed, while derived neutrophil-to-lymphocyte ratio increased.

CONCLUSIONS

Nivolumab in combination with cyclophosphamide was well tolerated but had limited activity in this paediatric setting. Metronomic cyclophosphamide did not modulate systemic immune response that could compensate limited T-cell infiltration and the immunosuppressive tumour microenvironment. CLINICALTRIALS.

GOV IDENTIFIER

NCT2813135.

Evolving Status of Clinical Immunotherapy with Oncolytic Adenovirus

Cancer immunotherapy targeting immune checkpoint inhibitors shows efficacy in several human cancers, but "cold tumors" that lack immune cells are typically unresponsive. Among the potential therapeutic approaches that could "heat" or promote lymphocyte infiltration of cold tumors, oncolytic viruses have attracted interest for their lytic and immunogenic mechanisms of action. In this article, we review the use of oncolytic adenoviruses in cancer immunotherapy, with a particular focus on preclinical and clinical data of oncolytic adenovirus-triggered immune responses against tumor antigens. We also discuss parameters to consider in clinical trial design and the combination of oncolytic adenoviruses with conventional treatments or other immunotherapies.

Metronomic oral cyclophosphamide in relapsed ovarian cancer

OBJECTIVES

To describe the clinical activity of metronomic cyclophosphamide in a population of patients with recurrent ovarian cancer, and to identify predictors of clinical response.

METHODS

We retrospectively reviewed all patients treated at our institution with oral metronomic cyclophosphamide for relapsed ovarian cancer between January 2012 and December 2016. These were identified from electronic chemotherapy prescription records. The primary endpoint was response rate by combined Gynecologic Cancer InterGroup (GCIG) criteria. Data on patient demographics, previous therapies, platinum resistance, germline BRCA1/2 (gBRCA1/2) status, disease response by radiological or cancer antigen 125 (CA125) criteria alone, adverse events secondary to metronomic cyclophosphamide treatment, progression-free survival, and overall survival were also evaluated.

RESULTS

50 out of 68 patients treated with oral metronomic cyclophosphamide were evaluable for disease response. By combination criteria (radiological plus CA125), complete response was 0%, partial response 32%, stable disease 16%, and progressive disease 52%. In the intention-to-treat population (n=68), progression-free survival and overall survival were 2.6 months and 6 months, respectively. Having a gBRCA1/2 mutation reduced the risk of disease progression by radiological criteria (OR 0.07, 95% CI 0.008 to 0.67, p=0.02), and patients with gBRCA1/2 mutations had improved progression-free survival (7.9 vs 2.5 months, HR 0.4, 95% CI 0.23 to 0.74, p=0.003) and overall survival (15.5 vs 6 months, HR 0.49, 95% CI 0.28 to 0.85, p=0.02) with metronomic cyclophosphamide when compared with patients without gBRCA1/2 mutations (or unknown gBRCA1/2 status).

CONCLUSION

Oral metronomic cyclophosphamide showed a clinical benefit in 48% of patients with recurrent ovarian cancer. gBRCA1/2 status can be an independent predictor of response.

A phase 1b clinical trial optimizing regulatory T cell depletion in combination with platinum-based chemotherapy in thoracic cancers

Background: Single-agent cyclophosphamide can deplete regulatory T-cells (Treg). We aimed to determine optimal dosing and scheduling of oral cyclophosphamide, alongside pemetrexed-based chemotherapy, to deplete Treg in mesothelioma or non-small-cell lung cancer patients.Methods: 31 Patients received pemetrexed ± cisplatin or carboplatin on day 1 of a 21-day cycle (maximum 6 cycles). From cycle two, patients received cyclophosphamide, 50 mg/day, with intrapatient escalation to maximum 100/150 mg/day alternately. Immunological changes were examined by flow cytometry. Primary endpoint was Treg proportion of CD4⁺ T-cells, with doses tailored to target Treg nadir <4%.Results: Reduction in Treg proportion was observed on day 8 of all cycles, and was not augmented by cyclophosphamide. Few patients achieved the <4% Treg target. Treg proliferation reached nadir one week after chemotherapy, and peaked on day 1 of the subsequent cycle. Efficacy parameters were similar to chemotherapy alone. Seventeen percent of patients ceased cyclophosphamide due to toxicity.Conclusions: Specific Treg depletion to the degree seen with single-agent cyclophosphamide was not observed during pemetrexed-based chemotherapy. This study highlights the poor evidence basis for use of cyclophosphamide as an immunotherapeutic in combination with chemotherapy, and the importance of detailed flow cytometry studies.Trial registration: Clinical trial registration: www.anzctr.org.au identifier is ACTRN12609000260224.

Chemoimmunotherapy for advanced gastrointestinal carcinomas: A successful combination of gene therapy and cyclophosphamide

The combination of a single low dose of cyclophosphamide (Cy) with the adenovirus-mediated gene transfer of interleukin-12 (AdIL-12) might represent a successful therapy for experimental gastrointestinal tumors. This approach has been proven to revert immunosuppressive mechanisms elicited by cancer cells and to synergistically promote antitumor immunity. In addition, this therapeutic regimen has been shown to be more efficient in achieving complete tumor regressions in mice than the application of a metronomic schedule of Cy plus AdIL-12.

Virotherapy, gene transfer and immunostimulatory monoclonal antibodies

Malignant cells are susceptible to viral infection and consequent cell death. Virus-induced cell death is endowed with features that are known to stimulate innate and adaptive immune responses. Thus danger signals emitted by cells succumbing to viral infection as well as viral nucleic acids are detected by specific receptors, and tumor cell antigens can be routed to professional antigen-presenting cells. The anticancer immune response triggered by viral infection is frequently insufficient to eradicate malignancy but may be further amplified. For this purpose, transgenes encoding cytokines as co-stimulatory molecules can be genetically engineered into viral vectors. Alternatively, or in addition, it is possible to use monoclonal antibodies that either block inhibitory receptors of immune effector cells, or act as agonists for co-stimulatory receptors. Combined strategies are based on the ignition of a local immune response at the malignant site plus systemic immune boosting. We have recently reported examples of this approach involving the Vaccinia virus or Semliki Forest virus, interleukin-12 and anti-CD137 monoclonal antibodies.

The discovery and development of oncolytic viruses: are they the future of cancer immunotherapy?

Introduction: Despite diverse treatment modalities and novel therapies, many cancers and patients are not effectively treated. Cancer immunotherapy has recently achieved breakthrough status yet is not effective in all cancer types or patients and can generate serious adverse effects. Oncolytic viruses (OVs) are a promising new therapeutic modality that harnesses virus biology and host interactions to treat cancer. OVs, genetically engineered or natural, preferentially replicate in and kill cancer cells, sparing normal cells/tissues, and mediating anti-tumor immunity.Areas covered: This review focuses on OVs as cancer therapeutic agents from a historical perspective, especially strategies to boost their immunotherapeutic activities. OVs offer a multifaceted platform, whose activities are modulated based on the parental virus and genetic alterations. In addition to direct viral effects, many OVs can be armed with therapeutic transgenes to also act as gene therapy vectors, and/or combined with other drugs or therapies.Expert opinion: OVs are an amazingly versatile and malleable class of cancer therapies. They tend to target cellular and host physiology as opposed to specific genetic alterations, which potentially enables broad responsiveness. The biological complexity of OVs have hindered their translation; however, the recent approval of talimogene laherparepvec (T-Vec) has invigorated the field.

Clinical Application of Oncolytic Viruses: A Systematic Review

Leveraging the immune system to thwart cancer is not a novel strategy and has been explored via cancer vaccines and use of immunomodulators like interferons. However, it was not until the introduction of immune checkpoint inhibitors that we realized the true potential of immunotherapy in combating cancer. Oncolytic viruses are one such immunotherapeutic tool that is currently being explored in cancer therapeutics. We present the most comprehensive systematic review of all oncolytic viruses in Phase 1, 2, and 3 clinical trials published to date. We performed a systematic review of all published clinical trials indexed in PubMed that utilized oncolytic viruses. Trials were reviewed for type of oncolytic virus used, method of administration, study design, disease type, primary outcome, and relevant adverse effects. A total of 120 trials were found; 86 trials were available for our review. Included were 60 phase I trials, five phase I/II combination trials, 19 phase II trials, and two phase III clinical trials. Oncolytic viruses are feverously being evaluated in oncology with over 30 different types of oncolytic viruses being explored either as a single agent or in combination with other antitumor agents. To date, only one oncolytic virus therapy has received an FDA approval but advances in bioengineering techniques and our understanding of immunomodulation to heighten oncolytic virus replication and improve tumor kill raises optimism for its future drug development.

Determinants of the efficacy of viro-immunotherapy: A review

Oncolytic virus immunotherapy is rapidly gaining interest in the field of immunotherapy against cancer. The minimal toxicity upon treatment and the dual activity of direct oncolysis and immune activation make therapy with oncolytic viruses (OVs) an interesting treatment modality. The safety and efficacy of several OVs have been assessed in clinical trials and, so far, the Food and Drug Administration (FDA) has approved one OV. Unfortunately, most treatments with OVs have shown suboptimal responses in clinical trials, while they appeared more promising in preclinical studies, with tumours reducing after immune cell influx. In several clinical trials with OVs, parameters such as virus replication, virus-specific antibodies, systemic immune responses, immune cell influx into tumours and tumour-specific antibodies have been studied as predictors or correlates of therapy efficacy. In this review, these studies are summarized to improve our understanding of the determinants of the efficacy of OV therapies in humans and to provide insights for future developments in the viro-immunotherapy treatment field.

A Review on Nano-Based Drug Delivery System for Cancer Chemoimmunotherapy

Although notable progress has been made on novel cancer treatments, the overall survival rate and therapeutic effects are still unsatisfactory for cancer patients. Chemoimmunotherapy, combining chemotherapeutics and immunotherapeutic drugs, has emerged as a promising approach for cancer treatment, with the advantages of cooperating two kinds of treatment mechanism, reducing the dosage of the drug and enhancing therapeutic effect. Moreover, nano-based drug delivery system (NDDS) was applied to encapsulate chemotherapeutic agents and exhibited outstanding properties such as targeted delivery, tumor microenvironment response and site-specific release. Several nanocarriers have been approved in clinical cancer chemotherapy and showed significant improvement in therapeutic efficiency compared with traditional formulations, such as liposomes (Doxil®, Lipusu®), nanoparticles (Abraxane®) and micelles (Genexol-PM®). The applications of NDDS to chemoimmunotherapy would be a powerful strategy for future cancer treatment, which could greatly enhance the therapeutic efficacy, reduce the side effects and optimize the clinical outcomes of cancer patients. Herein, the current approaches of cancer immunotherapy and chemoimmunotherapy were discussed, and recent advances of NDDS applied for chemoimmunotherapy were further reviewed.

Preclinical Toxicology of rQNestin34.5v.2: An Oncolytic Herpes Virus with Transcriptional Regulation of the ICP34.5 Neurovirulence Gene

rQNestin34.5v.2 is an oncolytic herpes simplex virus 1 (oHSV) that retains expression of the neurovirulent ICP34.5 gene under glioma-selective transcriptional regulation. To prepare an investigational new drug (IND) application, we performed toxicology and efficacy studies of rQNestin34.5v.2 in mice in the presence or absence of the immunomodulating drug cyclophosphamide (CPA). ICP34.5 allows HSV1 to survive interferon and improves viral replication by dephosphorylation of the eIF-2α translation factor. rQNestin34.5v.2 dephosphorylated eIF-2α in human glioma cells, but not in human normal cells, resulting in significantly higher cytotoxicity and viral replication in the former compared to the latter. In vivo toxicity of rQNestin34.5v.2 was compared with that of wild-type F strain in immunocompetent BALB/c mice and athymic mice by multiple routes of administration in the presence or absence of CPA. A likely no observed adverse effect level (NOAEL) dose for intracranial rQNestin34.5v.2 was estimated, justifying a phase 1 clinical trial in recurrent glioma patients (ClinicalTrials.gov: NCT03152318), after successful submission of an IND.

Oncolytic viruses: what to expect from their use in cancer treatment

Oncolytic viruses are biologic agents able to selectively infect and destroy cancer cells while sparing the normal ones. Furthermore, they also stimulate the host immune system to combat the tumor growth and to promote tumor removal. This review thoroughly describes different types of viruses developed for targeting specific cancers, as well as the strategies to improve the efficacy and safety of oncolytic virotherapy. It also explores how their potential as anticancer agents may be enhanced through combination with other traditional therapies, such as chemotherapy or more recent approaches, such as checkpoint inhibitors. There are many oncolytic viruses currently being tested in clinical trials for the treatment of various types of cancer, suggesting that this approach could become the near future of the oncology field.

Virotherapy: From single agents to combinatorial treatments

Virotherpay is emerging as a promising strategy against cancer, and three oncolytic viruses (OVs) have gained approval in different countries for the treatment of several cancer types. Beyond the capability to selectively infect, replicate and lyse cancer cells, OVs act through a multitude of events, including modification of the tumour micro/macro-environment as well as a complex modulation of the anti-tumour immune response by activation of danger signals and immunogenic cell death pathways. Most OVs show limited effects, depending on the viral platform and the interactions with the host. OVs used as monotherapy only in a minority of patients elicited a full response. Better outcomes were obtained using OVs in combination with other treatments, such as immune therapy or chemotherapy, suggesting that the full potential of OVs can be unleashed in combination with other treatment modalities. Here, we report the main described combination of OVs with conventional chemotherapeutic agents: platinum salts, mitotic inhibitors, anthracyclines and other antibiotics, anti-metabolites, alkylating agents and topoisomerase inhibitors. Additionally, our work provides an overview of OV combination with targeted therapies: histone deacetylase inhibitors, kinase inhibitors, monoclonal antibodies, inhibitors of DNA repair, inhibitors of the proteasome complex and statins that demonstrated enhanced OV anti-neoplastic activity. Although further studies are required to assess the best combinations to translate the results in the clinic, it is clear that combined therapies, acting with complementary mechanisms of action might be useful to target cancer lesions resistant to currently available treatments.

Low Dose Cyclophosphamide Modulates Tumor Microenvironment by TGF-β Signaling Pathway

The tumor microenvironment has been recently recognized as a critical contributor to cancer progression and anticancer therapy-resistance. Cyclophosphamide (CTX) is a cytotoxic agent commonly used in clinics for the treatment of cancer. Previous reports demonstrated that CTX given at low continuous doses, known as metronomic schedule, mainly targets endothelial cells and circulating Tregs with unknown mechanisms. Here, we investigated the antitumor activity of two different metronomic schedules of CTX along with their corresponding MTD regimen and further explored their effect on immune function and tumor microenvironment. Toxicity evaluation was monitored by overall survival rate, weight loss, and histopathological analysis. A nude mouse model of Lewis lung cancer was established to assess the anti-metastatic effects of CTX in vivo. CD4⁺, CD8⁺, and CD4⁺CD25⁺FoxP3 T cells were selected by flow cytometry analysis. Low and continuous administration of CTX was able to restore immune function via increase of CD4⁺/CD8⁺ T cells and depletion of T regulatory cells, not only in circulatory and splenic compartments, but also at the tumor site. Low-dose CTX also reduced myofibroblasts, accompanied with an increased level of E-cadherin and low N-cadherin, both in the primary tumor and lung through the TGF-β pathway by the downregulated expression of TGF-β receptor 2. Our data may indicate that several other molecular mechanisms of CTX for tumor may be involved in metronomic chemotherapy, besides targeting angiogenesis and regulatory T cells.

Breaking Therapy Resistance: An Update on Oncolytic Newcastle Disease Virus for Improvements of Cancer Therapy

Resistance to therapy is a major obstacle to cancer treatment. It may exist from the beginning, or it may develop during therapy. The review focusses on oncolytic Newcastle disease virus (NDV) as a biological agent with potential to break therapy resistance. This avian virus combines, upon inoculation into non-permissive hosts such as human, 12 described anti-neoplastic effects with 11 described immune stimulatory properties. Fifty years of clinical application of NDV give witness to the high safety profile of this biological agent. In 2015, an important milestone was achieved, namely the successful production of NDV according to Good Manufacturing Practice (GMP). Based on this, IOZK in Cologne, Germany, obtained a GMP certificate for the production of a dendritic cell vaccine loaded with tumor antigens from a lysate of patient-derived tumor cells together with immunological danger signals from NDV for intracutaneous application. This update includes single case reports and retrospective analyses from patients treated at IOZK. The review also presents future perspectives, including the concept of in situ vaccination and the combination of NDV or other oncolytic viruses with checkpoint inhibitors.

Programmed cell death 1 (PD-1) targeting in patients with advanced osteosarcomas: results from the PEMBROSARC study

PURPOSE

There are some lines of evidence suggesting a potential role of immunotherapy for treating patients with osteosarcomas.

PATIENTS AND METHODS

This was an open-label, multicentre, phase 2 study of pembrolizumab in combination with metronomic cyclophosphamide in patients with advanced osteosarcomas. All patients received 50 mg b.i.d. of cyclophosphamide one week on and one week off and 200 mg of intravenous pembrolizumab (every 3 weeks). There was a dual primary end-point, encompassing both the non-progression and objective responses at 6 months per Response Evaluation Criteria in Solid Tumours (RECIST), version 1.1. An objective response rate of 20% and/or a 6-month non-progression rate of 60% were determined as reasonable objectives for treatment with meaningful effect. Correlative studies of immune biomarkers were planned from the patients' tumour samples.

RESULTS

Between October 13 2015 and July 3 2017, 17 patients were included. Fifty were assessable for the efficacy end-point. Four patients experienced tumour shrinkage, resulting in a partial response (PR) in one patient (6.7%). The 6-month non-progression rate was 13.3% (95% confidence interval [CI]: 1.7-40.5). The most frequent adverse events were grade I or II nausea, anaemia, anorexia and fatigue. programmed death-ligand 1 (PD-L1) expression rate was low, observed in only 2 cases of 14 with available tumour material. The only patient who experienced PR had a PD-L1-negative tumour.

CONCLUSION

Programmed cell death 1 (PD-1) inhibition has limited activity in osteosarcomas. Further studies investigating PD-1 inhibitor in combination with agents modulating the microenvironment are warranted.

TRIAL REGISTRATION

This study is registered with ClinicalTrials.gov, number NCT02406781.

Targeting Palbociclib-Resistant Estrogen Receptor-Positive Breast Cancer Cells via Oncolytic Virotherapy

While clinical responses to palbociclib have been promising, metastatic breast cancer remains incurable due to the development of resistance. We generated estrogen receptor-positive (ER+) and ER-negative (ER−) cell line models and determined their permissiveness and cellular responses to an oncolytic adenovirus (OAd) known as Ad5/3-delta24. Analysis of ER+ and ER− palbociclib-resistant cells revealed two clearly distinguishable responses to the OAd. While ER+ palbociclib-resistant cells displayed a hypersensitive phenotype to the effects of the OAd, ER− palbociclib-resistant cells showed a resistant phenotype to the OAd. Hypersensitivity to the OAd in ER+ palbociclib-resistant cells correlated with a decrease in type I interferon (IFN) signaling, an increase in viral entry receptor expression, and an increase in cyclin E expression. OAd resistance in ER− palbociclib-resistant cells correlated with an increase in type I IFN signaling and a marked decrease in viral entry receptor. Using the OAd as monotherapy caused significant cytotoxicity to both ER+ and ER− palbociclib-sensitive cell lines. However, the addition of palbociclib increased the oncolytic activity of the OAd only in ER+ palbociclib-sensitive cells. Our studies provide a mechanistic base for a novel anti-cancer regimen composed of an OAd in combination with palbociclib for the treatment of ER+ breast cancer.

Addition of Cyclophosphamide "On Demand" to Lenalidomide and Corticosteroids in Patients With Relapsed/Refractory Multiple Myeloma-A Retrospective Review of a Single-center Experience

INTRODUCTION

The combination of lenalidomide and dexamethasone (Len-Dex) is an established regimen for patients with relapsed or refractory myeloma. To prolong the benefit of this effective regimen, the Myeloma Program at Princess Margaret Cancer Centre has routinely added a third agent, oral cyclophosphamide (Cy) given weekly, to Len-Dex at disease progression.

PATIENTS AND METHODS

In the present report, we describe the cases of 53 patients who had received Len-Dex-Cy for a minimum of 4 weeks from January 2007 to December 2014 after progression with Len-Dex alone. The dose of added Cy ranged from 250 to 500 mg weekly. The median number of previous regimens, including Len-Dex, was 2 (range, 2-4); 80% of patients had undergone previous autologous stem cell transplantation.

RESULTS

The overall rate of response equal to or greater than a partial response was 34%, and clinical benefit (stable disease or better) was observed in 87% of the patients. The median duration of Len-Dex-Cy therapy was 6.9 months (range, 0.9-55.1 months). The median progression-free survival was 6.1 months (range, 4.2-8.1 months) from the addition of Cy and 24.1 months (range, 15.9-32.0 months) from start of Len-Dex.

CONCLUSION

The addition of Cy for patients with myeloma developing progression with Len-Dex was an inexpensive option with manageable toxicity that resulted in a clinically meaningful extension of disease control.

Oncolytic Viruses on Drugs: Achieving Higher Therapeutic Efficacy

Over the past 20 years there has been a dramatic expansion in the testing of oncolytic viruses (OVs) for the treatment of cancer. OVs are unique biotherapeutics that induce multimodal responses toward tumors, from direct cytopathic effects on cancer cells, to tumor associated blood vessel disruption, and ultimately potent stimulation of anti-tumor immune activation. These agents are highly targeted and can be efficacious as cancer treatments resulting in some patients experiencing complete tumor regression and even cures from OV monotherapy. However, most patients have limited responses with viral replication in tumors often found to be modest and transient. To augment OV replication, increase bystander killing of cancer cells, and/or stimulate stronger targeted anti-cancer immune responses, drug combination approaches have taken center stage for translation to the clinic. Here we comprehensively review drugs that have been combined with OVs to increase therapeutic efficacy, examining the proposed mechanisms of action, and we discuss trends in pharmaco-viral immunotherapeutic approaches currently being investigated.

Lenalidomide combined with low-dose cyclophosphamide and prednisone modulates Ikaros and Aiolos in lymphocytes, resulting in immunostimulatory effects in lenalidomide-refractory multiple myeloma patients

We recently showed that the outcome of multiple myeloma (MM) patients treated in the REPEAT study (evaluation of lenalidomide combined with low-dose cyclophosphamide and prednisone (REP) in lenalidomide-refractory MM) was markedly better than what has been described with cyclophosphamide-prednisone alone. The outcome with REP was not associated with plasma cell Cereblon expression levels, suggesting that the effect of REP treatment may involve mechanisms independent of plasma cell Cereblon-mediated direct anti-tumor activity. We therefore hypothesized that immunomodulatory effects contribute to the anti-MM activity of REP treatment, rather than plasma cell Cereblon-mediated effects. Consequently, we now characterized the effect of REP treatment on immune cell subsets in peripheral blood samples collected on day 1 and 14 of cycle 1, as well as on day 1 of cycle 2. We observed a significant mid-cycle decrease in the Cereblon substrate proteins Ikaros and Aiolos in diverse lymphocyte subsets, which was paralleled by an increase in T-cell activation. These effects were restored to baseline at day one of the second cycle, one week after lenalidomide interruption. In vitro, lenalidomide enhanced peripheral blood mononuclear cell-mediated killing of both lenalidomide-sensitive and lenalidomide-resistant MM cells in a co-culture system. These results indicate that the Cereblon-mediated immunomodulatory properties of lenalidomide are maintained in lenalidomide-refractory MM patients and may contribute to immune-mediated killing of MM cells. Therefore, combining lenalidomide with other drugs can have potent effects through immunomodulation, even in patients considered to be lenalidomide-refractory.

Combining radiation therapy and cancer immune therapies: From preclinical findings to clinical applications

Besides its direct cytotoxic effect on the tumor cells, radiation therapy is also able to elicit an immune-mediated systemic anti-tumor response, resulting in tumor regression in irradiated sites but also within distant out of field secondary lesions and providing a long-term anti-tumor response. It is now clear that associating ionizing radiation with immune therapies can enhance radio-induced anti-tumor immune responses. Over the last decade, such a combination aroused considerable interest among the scientific community, with many preclinical models and clinical trials, using many types of immune therapies and radiation regimens. In this article, we summarize the main mechanisms underlying radio-induced anti-tumor responses. We will then present an extended overview of the recent preclinical and clinical research built on this background of combined radiation and immune therapy, shedding light on what we know so far about such a promising strategy.

Oncolytic virus immunotherapies in ovarian cancer: moving beyond adenoviruses

Ovarian cancer is the 5th most common cancer in UK women with a high relapse rate. The overall survival for ovarian cancer has remained low for decades prompting a real need for new therapies. Recurrent ovarian cancer remains confined in the peritoneal cavity in >80% of the patients, providing an opportunity for locoregional administration of novel therapeutics, including gene and viral therapy approaches. Immunotherapy is an expanding field, and includes oncolytic viruses as well as monoclonal antibodies, immune checkpoint inhibitors, and therapeutic vaccines. Oncolytic viruses cause direct cancer cell cytolysis and immunogenic cell death and subsequent release of tumor antigens that will prime for a potent tumor-specific immunity. This effect may be further enhanced when the viruses are engineered to express, or coadministered with, immunostimulatory molecules. Currently, the most commonly used and well-characterized vectors utilized for virotherapy purposes are adenoviruses. They have been shown to work synergistically with traditional chemotherapy and radiotherapy and have met with success in clinical trials. However, pre-existing immunity and poor in vivo models limit our ability to fully investigate the potential of oncolytic adenovirus as effective immunotherapies which in turn fosters the need to develop alternative viral vectors. In this review we cover recent advances in adenovirus-based oncolytic therapies targeting ovarian cancer and recent advances in mapping immune responses to oncolytic virus therapies in ovarian cancer.

Immunotherapy using regulatory T cells in cancer suggests more flavors of hypersensitivity type IV

Regulatory T cells (Tregs) profoundly affect tumor microenvironment and exert dominant suppression over antitumor immunity in response to self-antigen expressed by tumor. Immunotherapy targeting Tregs lead to a significant improvement in antitumor immunity. Intradermal injection of tumor antigen results in negative delayed-type hypersensitivity (DTH) type IV. However, anti-Tregs treatment/use of adjuvant along with tumor antigens turns DTH to positive. Considering Tregs as the earliest tumor sensor/responders, tumor can be regarded as Treg-mediated type IV hypersensitivity and negative DTH to tumor antigen is due to anti-inflammatory action of Tregs to tumor antigens at the injection site. Such a view would help us in basic and clinical situations to testify a candidate vaccine via dermal administration and evaluation of Treg proportion at injection site.

Interleukin 8 activity influences the efficacy of adenoviral oncolytic immunotherapy in cancer patients

After the landmark approval of T-VEC, oncolytic viruses are finding their way to the clinics. However, response rates have still room for improvement, and unfortunately there are currently no available markers to predict responses for oncolytic immunotherapy. Interleukin 8 (IL-8) production is upregulated in many cancers and it also connects to several pathways that have been shown to impair the efficacy of adenoviral immunotherapy. We studied the role of IL-8 in 103 cancer patients treated with oncolytic adenoviruses. We found high baseline serum IL-8 concentration to be independently associated with poor prognosis (p<0.001). Further, normal baseline IL-8 was associated with improved prognostic potential of calculation of the neutrophil-to-lymphocyte ratio (p<0.001). Interestingly, a decrease in IL-8 concentration after treatment with oncolytic adenovirus predicted better overall survival (p<0.001) and higher response rate, although this difference was not significant (p=0.066). We studied the combination of adenovirus and IL-8 neutralizing antibody ex vivo in single cell suspensions and in co-cultures of tumor-associated CD15+ neutrophils and CD3+ tumor-infiltrating lymphocytes derived from fresh patient tumor samples. These results indicate a role for IL-8 as a biomarker in oncolytic virotherapy, but additionally provide a rationale for targeting IL-8 to improve treatment efficacy. In conclusion, curtailing the activity of IL-8 systemically or locally in the tumor microenvironment could improve anti-tumor immune responses resulting in enhanced efficacy of adenoviral immunotherapy of cancer.

Use of PD-1 Targeting, Macrophage Infiltration, and IDO Pathway Activation in Sarcomas: A Phase 2 Clinical Trial

IMPORTANCE

There is a strong rationale for treating sarcomas with immunotherapy.

OBJECTIVE

To assess the efficacy and safety of programmed cell death protein 1 (PD-1) targeting in combination with metronomic chemotherapy in sarcomas.

DESIGN, SETTING, AND PARTICIPANTS

This was an open-label, multicenter, phase 2 study of 4 cohorts of patients with advanced soft-tissue sarcoma (STS), including leiomyosarcoma (LMS), undifferentiated pleomorphic sarcoma (UPS), other sarcomas (others), and gastrointestinal stromal tumor (GIST). All patients received 50 mg twice daily cyclophosphamide 1 week on and 1 week off and 200 mg of intravenous pembrolizumab every 3 weeks.

INTERVENTION OR EXPOSURE

Pembrolizumab in combination with metronomic cyclophosphamide.

MAIN OUTCOMES AND MEASURES

There was a dual primary end point, encompassing both the nonprogression and objective responses at 6 months per Response Evaluation Criteria in Solid Tumours (RECIST) v1.1 for LMS, UPS, and others and 6-month nonprogression for GIST. An objective response rate of 20% and/or a 6-month nonprogression rate of 60% were determined as reasonable objectives for treatment with meaningful effect. Correlative studies of immune biomarkers were planned from patient tumor and plasma samples.

RESULTS

Between June 2015 and July 2016, 57 patients were included (median [range] age, 59.5 [18.5-84.0] years; 24 women [42%]); 50 patients were assessable for the efficacy end point. Three patients experienced tumor shrinkage, resulting in a partial response in a single solitary fibrous tumor. The 6-month nonprogression rates were 0%, 0%, 14.3% (95% CI, 1.8%-42.8%) for LMS, UPS, and others, respectively, and 11.1% (95% CI, 2.8%-48.3%) for GIST. The most frequent adverse events were grade 1 or 2 fatigue, diarrhea, and anemia. The only patient who experienced partial response was the only one with strong programmed cell death 1 ligand 1-positive staining in immune cell. Strong infiltration by macrophage expressing the inhibitory enzyme indoleamine 2,3-dioxygenase 1 (IDO1) was observed in the majority of cases. Moreover, a significant increase in the kynurenine to tryptophan ratio was observed in patient plasma samples during the study treatment.

CONCLUSIONS AND RELEVANCE

We found that PD-1 inhibition has limited activity in selected STS and GIST. This may be explained by an immunosuppressive tumor microenvironment resulting from macrophage infiltration and IDO1 pathway activation.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02406781.

Low-Dose Cyclophosphamide Induces Antitumor T-Cell Responses, which Associate with Survival in Metastatic Colorectal Cancer

Purpose: Anticancer T-cell responses can control tumors, but immunosuppressive mechanisms in vivo prevent their function. The role of regulatory T cells (Tregs) in metastatic colorectal cancer is unclear. We have previously shown depletion of Tregs enhances colorectal cancer-specific effector T-cell responses. Low-dose cyclophosphamide targets Tregs in animal models and some human studies; however, the effect of cyclophosphamide in metastatic colorectal cancer is unknown.Experimental Design: Fifty-five patients with metastatic colorectal cancer were enrolled in a phase I/II trial and randomly assigned to receive 2-week-long courses of low-dose (50 mg twice a day) cyclophosphamide or not. The absolute number, phenotype, and antitumor function of peripheral blood-derived lymphocyte subsets were monitored throughout treatment, as well as during 18-month follow-up.Results: Initially, cyclophosphamide reduced proliferation in all lymphocyte subsets; however, a rapid mobilization of effector T cells overcame this decrease, leading to increased absolute T-cell numbers. In contrast, a reduction in proportional and absolute Treg, B-cell, and NK-cell numbers occurred. The expansion and subsequent activation of effector T cells was focused on tumor-specific T cells, producing both granzyme B and IFNγ. Cyclophosphamide-treated patients demonstrating the most enhanced IFNγ+ tumor-specific T-cell responses exhibited a significant delay in tumor progression [HR = 0.29; 95% confidence interval (CI), 0.12-0.69; P = 0.0047), compared with nonresponders and no-treatment controls.Conclusions: Cyclophosphamide-induced Treg depletion is mirrored by a striking boost in antitumor immunity. This study provides the first direct evidence of the benefit of naturally primed T cells in patients with metastatic colorectal cancer. Our results also support the concept that nonmutated self-antigens may act as useful targets for immunotherapies. Clin Cancer Res; 23(22); 6771-80. ©2017 AACR.

Immunotherapy for breast cancer: past, present, and future

Immunotherapy has shown promise in many solid tumors including melanoma and non-small cell lung cancer with an evolving role in breast cancer. Immunotherapy encompasses a wide range of therapies including immune checkpoint inhibition, monoclonal antibodies, bispecific antibodies, vaccinations, antibody-drug conjugates, and identifying other emerging interventions targeting the tumor microenvironment. Increasing efficacy of these treatments in breast cancer patients requires identification of better biomarkers to guide patient selection; recognizing when to initiate these therapies in multi-modality treatment plans; establishing novel assays to monitor immune-mediated responses; and creating combined systemic therapy options incorporating conventional treatments such as chemotherapy and endocrine therapy. This review will focus on the current role and future directions of many of these immunotherapies in breast cancer, as well as highlighting clinical trials that are investigating several of these active issues.

Development of a Curative Therapeutic Vaccine (TheraVac) for the Treatment of Large Established Tumors

Harnessing immune system to treat cancer requires simultaneous generation of tumor-specific CTLs and curtailment of tumor immunosuppressive environment. Here, we developed an immunotherapeutic regimen capable of eliminating large established mouse tumors using HMGN1, a DC-activating TLR4 agonist capable of inducing anti-tumor immunity. Intratumoral delivery of HMGN1 with low dose of Cytoxan cured mice bearing small (∅ ≈ 0.5 cm), but not large (∅ ≈ 1.0 cm) CT26 tumors. Screening for activators capable of synergizing with HMGN1 in activating DC identified R848. Intratumoral delivery of HMGN1 and R848 plus Cytoxan eradicated large established CT26 tumors. The resultant tumor-free mice were resistant to subsequent challenge with CT26, indicating the generation of CT26-specific protective immunity. This immunotherapeutic regimen caused homing of tumor-infiltrating DC to draining lymph nodes and increased infiltration of T cells into tumor tissues. Cytoxan in this regimen could be replaced by anti-CTLA4) or anti-PD-L1. Importantly, this immunotherapeutic regimen was also curative for large established mouse Renca and EG7 tumors. Thus, we have developed a curative therapeutic vaccination regimen dubbed ‘TheraVac’ consisting of HMGN1 and R848 plus a checkpoint inhibitor, that can, without using exogenous tumor-associated antigen(s), eliminate various large tumors and induce tumor-specific immunity.

Systemic virotherapy for multiple myeloma

INTRODUCTION

The multiple myeloma (MM) treatment scenario has changed considerably over the past few years. Several novel targeted therapies are currently under consideration including oncolytic virotherapy. Areas covered: This review provides an analysis of the mechanisms of action of virotherapy, and summarizes the preclinical and clinical studies of systemic virotherapy developed for the treatment of MM. Different types of viruses have been identified, including: adenovirus, vaccinia virus, herpes simplex virus 1, myxoma virus, reovirus, measles virus, vesicular stomatitis virus and coxsackievirus A21. Expert opinion: The above-mentioned viruses can do more than simply infect and kill malignant plasma cells alone or in combination with chemo and/or radiotherapy. In fact, some of them can also be used to purge myeloma cells from an autologous bone marrow (BM) transplant. Further investigations are required to better explore the best therapeutic combinations for MM and to also overcome antiviral response immunity that can limit the efficacy of this therapeutic strategy.