Phase I Study of a Poxviral TRICOM-Based Vaccine Directed Against the Transcription Factor Brachyury

A Review of Clinical Trials of Cancer and Its Treatment as a Vaccine

BACKGROUND

Cancer and infectious diseases are one of the greatest challenges of modern medicine. An unhealthy lifestyle, poor drug use, or drug misuse contribute to the rise in morbidity and mortality brought on by these illnesses. The inadequacies of the medications now being used to treat these disorders, along with the growing issue of drug resistance, have compelled researchers to look for novel compounds with therapeutic promise. The number of infections and diseases has significantly abated due to vaccine development and use over time, which is described in detail. Several novel vaccines can now be produced by manipulating Deoxyribonucleic acid (DNA), Ribonucleic acid (RNA), Messenger Ribonucleic acid (mRNA), proteins, viral vector Recombinant, and other molecules due to advances in genetic engineering and our understanding of the immune defense.

OBJECTIVE

The main topic of discussion is cancer-based vaccinations, which were developed less than a decade ago but have already been used to treat a wide range of both life-threatening and deadly diseases. It contains clinical studies for cancer vaccines against kidney, liver, prostate, cervix, and certain RNA-based cancer vaccines against breast and bladder cancer.

RESULTS

Numerous studies using various DNA and RNA-based methods have been conducted on the basis of cancer, with 9-10 diseases related to DNA and 8-9 diseases associated with RNA. Some of these studies have been completed, while others have been eliminated due to a lack of research; further studies are ongoing regarding the same.

CONCLUSION

This brief discussion of vaccines and their varieties with examples also discusses vaccine clinical trials in relation to cancer diseases in this DNA and RNA-based cancer vaccine that has had successful clinical trials like the cervical cancer drug VGX-3100, the kidney cancer drug Pembrolizumab, MGN-1601, the prostate cancer drug pTVG-HP with rhGM-CSF, the melanoma cancer drug proteasome siRNA, and the lung cancer drug FRAME-001.

The role of tumor immune microenvironment in chordoma: promising immunotherapy strategies

Chordoma is a rare malignant bone tumor with limited therapeutic options, which is resistant to conventional chemotherapy and radiotherapy, and targeted therapy is also shown with little efficacy. The long-standing delay in researching its mechanisms of occurrence and development has resulted in the dilemma of no effective treatment targets and no available drugs in clinical practice. In recent years, the role of the tumor immune microenvironment in driving tumor growth has become a hot and challenging topic in the field of cancer research. Immunotherapy has shown promising results in the treatment of various tumors. However, the study of the immune microenvironment of chordoma is still in its infancy. In this review, we aim to present a comprehensive reveal of previous exploration on the chordoma immune microenvironment and propose promising immunotherapy strategies for chordoma based on these characteristics.

Shedding light on emerging therapeutic targets for chordoma

INTRODUCTION

Despite encouraging advances in radiation and surgical treatment, chordomas remain resistant to chemotherapy and local recurrence is common. Although the primary mechanism of recurrence is local, metastatic disease occurs in a small subset of patients. Recurrence may also occur along the surgical trajectory if care is not taken to fully excise the open biopsy pathway. There is increasing morbidity with reoperation upon disease recurrence, and radiation is an option for cytoreduction in primary disease or for recurrent disease, although toxicity may be observed with high-dose therapies. Given these challenges, targeted chemotherapeutic agents for postoperative adjuvant treatment are needed.

AREAS COVERED

In this review, we summarize the genetic drivers of chordoma and the state of the current research in chordoma immunotherapy and epigenetics.

EXPERT OPINION

Chordoma is a heterogenous tumor that should be targeted from different angles and the study of its characteristics, from molecular to immunological to epigenetic, is necessary. Combining different approaches, such as studying noninvasive patient methylation patterns with tissue-based molecular and drug screening, can transform patient care by guiding treatment decisions based on prognostic mechanisms from different sources, while helping individualize surgical planning and treatment.

Armored modified vaccinia Ankara in cancer immunotherapy

Cancer immunotherapy relies on unleashing the patient´s immune system against tumor cells. Cancer vaccines aim to stimulate both the innate and adaptive arms of immunity to achieve durable clinical responses. Some roadblocks for a successful cancer vaccine in the clinic include the tumor antigen of choice, the adjuvants employed to strengthen antitumor-specific immune responses, and the risks associated with enhancing immune-related adverse effects in patients. Modified vaccinia Ankara (MVA) belongs to the family of poxviruses and is a versatile vaccine platform that combines several attributes crucial for cancer therapy. First, MVA is an excellent inducer of innate immune responses leading to type I interferon secretion and induction of T helper cell type 1 (Th1) immune responses. Second, it elicits robust and durable humoral and cellular immunity against vector-encoded heterologous antigens. Third, MVA has enormous genomic flexibility, which allows for the expression of multiple antigenic and costimulatory entities. And fourth, its replication deficit in human cells ensures a excellent safety profile. In this review, we summarize the current understanding of how MVA induces innate and adaptive immune responses. Furthermore, we will give an overview of the tumor-associated antigens and immunomodulatory molecules that have been used to armor MVA and describe their clinical use. Finally, the route of MVA immunization and its impact on therapeutic efficacy depending on the immunomodulatory molecules expressed will be discussed.

Preclinical development of a first-in-class vaccine encoding HER2, Brachyury and CD40L for antibody enhanced tumor eradication

The induction of antiviral innate immunity by systemic immunization with live virus can be employed to positively impact the response to therapeutic vaccination. We previously demonstrated that systemic immunization with a non-replicating MVA encoding CD40 ligand (CD40L) enhances innate immune cell activation and function, and triggers potent antitumor CD8⁺ T cell responses in different murine tumor models. Antitumor efficacy was increased when combined with tumor targeting antibodies. Here we report the development of TAEK-VAC-HerBy (TVH), a first-in-class human tumor antibody enhanced killing (TAEK) vaccine based on the non-replicating MVA-BN viral vector. It encodes the membrane bound form of human CD40L, HER2 and the transcription factor Brachyury. TVH is designed for therapeutic use in HER2- or Brachyury-expressing cancer patients in combination with tumor targeting antibodies. To preclude possible oncogenic activities in infected cells and to prevent binding of vaccine-encoded HER2 by monoclonal antibodies trastuzumab and pertuzumab, genetic modifications of HER2 were introduced in the vaccine. Brachyury was genetically modified to prevent nuclear localization of the protein thereby inhibiting its transcriptional activity. CD40L encoded in TVH enhanced human leukocyte activation and cytokine secretion in vitro. Lastly, TVH intravenous administration to non-human primates was proven immunogenic and safe in a repeat-dose toxicity study. Nonclinical data presented here highlight TVH as a first-in-class immunotherapeutic vaccine platform currently under clinical investigation.

Immunotherapy as a Promising Option for the Treatment of Advanced Chordoma: A Systemic Review

OBJECTIVE

To summarize the function and efficacy of immunotherapy as an adjunctive therapy in the treatment of advanced chordoma.

METHODS

Literature search was conducted by two reviewers independently. Case reports, case series and clinical trials of immunotherapy for chordoma were retrieved systematically from Pubmed, Web of Science, Scoupus and Cochrane Library. Clinical outcome data extracted from the literature included median progression-free survival (PFS), median overall survival (OS), clinical responses and adverse events (AEs).

RESULTS

All studies were published between 2015 and 2022. Twenty-two eligible studies were selected for systemic review. PD-1/PD-L1 immune checkpoint inhibitors (ICIs) were the most common used immunotherapy agents in chordoma, among which Pembrolizumab was the most frequently prescribed. CTLA-4 antibody was only used as combination therapy in chordoma. Dose Limiting Toxicity (DLT) was not observed in any vaccine targeting brachyury, and injection site response was the most frequent AV. The response evaluation criteria in solid tumors (RECIST) were the most generally used evaluation standard in chordoma immunotherapy, and none of the included studies employed the Choi criteria.

CONCLUSIONS

No clinical data have demonstrated that CTLA-4 ICIs combined with PD-1/PD-L1 ICIs is more effective than ICIs monotherapy in treating chordoma, and ICIs in combination with other therapies exhibit more toxicity than monotherapy. PD-1/PD-L1 ICIs monotherapy is recommended as an immunotherapy in patients with advanced chordoma, which may even benefit PD-L1-negative patients. The brachyury vaccine has shown good safety in chordoma patients, and future clinical trials should focus on how to improve its therapeutic efficacy. The use of immunomodulatory agents is a promising therapeutic option, though additional clinical trials are required to evaluate their safety and effectiveness. RECIST does not seem to be an appropriate standard for assessing medications of intratumoral immunotherapy.

Recent Advances in DNA Vaccines against Lung Cancer: A Mini Review

Lung cancer is regarded as the major causes of patient death around the world. Although the novel tumor immunotherapy has made great progress in the past decades, such as utilizing immune checkpoint inhibitors or oncolytic viruses, the overall 5-year survival of patients with lung cancers is still low. Thus, development of effective vaccines to treat lung cancer is urgently required. In this regard, DNA vaccines are now considered as a promising immunotherapy strategy to activate the host immune system against lung cancer. DNA vaccines are able to induce both effective humoral and cellular immune responses, and they possess several potential advantages such as greater stability, higher safety, and being easier to manufacture compared to conventional vaccination. In the present review, we provide a global overview of the mechanism of cancer DNA vaccines and summarize the innovative neoantigens, delivery platforms, and adjuvants in lung cancer that have been investigated or approved. Importantly, we highlight the recent advance of clinical studies in the field of lung cancer DNA vaccine, focusing on their safety and efficacy, which might accelerate the personalized design of DNA vaccine against lung cancer.

Indolent multicentric chordoma – A previously undescribed entity: A Case report and literature review

Background:

Chordomas are rare neuraxial tumors arising from remnants of primitive notochord. They are generally slow-growing malignant neoplasms. Only four adult cases of multicentric chordomas have been reported, all with aggressive and rapid growth. Here, we present an unusual case of indolent multicentric chordomas involving cervical and thoracic spine, sacrum, and calvarium.

Case Description:

A 60-year-old male was found to have multiple lesions throughout his neuroaxis incidentally on workup for colitis. A needle biopsy documented the diagnosis of chordoma. This has been followed for more than 4 years with no progression.

Conclusion:

We present the first reported case of indolent multicentric chordomas. Due to the extreme rarity of indolent multicentric chordomas, close follow-up is needed and recommended.

The Role of the Tumor Microenvironment and Treatment Strategies in Colorectal Cancer

Colorectal cancer (CRC) has the second highest mortality rate among all cancers worldwide. Surgery, chemotherapy, radiotherapy, molecular targeting and other treatment methods have significantly prolonged the survival of patients with CRC. Recently, the emergence of tumor immunotherapy represented by immune checkpoint inhibitors (ICIs) has brought new immunotherapy options for the treatment of advanced CRC. As the efficacy of ICIs is closely related to the tumor immune microenvironment (TME), it is necessary to clarify the relationship between the immune microenvironment of CRC and the efficacy of immunotherapy to ensure that the appropriate drugs are selected. We herein review the latest research progress in the immune microenvironment and strategies related to immunotherapy for CRC. We hope that this review helps in the selection of appropriate treatment strategies for CRC patients.

Role of T-box genes in cancer, epithelial-mesenchymal transition, and cancer stem cells

Sharing a common DNA binding motif called T-box, transcription factor T-box gene family controls embryonic development and is also involved in cancer progression and metastasis. Cancer metastasis shows therapy resistance and involves complex processes. Among them, epithelial-mesenchymal transition (EMT) triggers cancer cell invasiveness and the acquisition of stemness of cancer cells, called cancer stem cells (CSCs). CSCs are a small fraction of tumor bulk and are capable of self-renewal and tumorsphere formation. Recent progress has highlighted the critical roles of T-box genes in cancer progression, EMT, and CSC function, and such regulatory functions of T-box genes have emerged as potential therapeutic candidates for cancer. Herein we summarize the current understanding of the regulatory mechanisms of T-box genes in cancer, EMT, and CSCs, and discuss the implications of targeting T-box genes as anticancer therapeutics.

Integrating Cancer Vaccines in the Standard-of-Care of Ovarian Cancer: Translating Preclinical Models to Human

Simple Summary

The overall survival of ovarian cancer (OC) remains poor for most patients. Despite incorporation of novel therapeutic agents such as bevacizumab and PARP inhibitors to OC standard-of-care, efficacy is only observed in a subset of patients. Cancer vaccination has demonstrated effectiveness in OC patients and could be considered for potential incorporation into OC standard-of-care. This review provides an overview of the different types of cancer vaccination strategies and discusses the use of murine OC tumor models to evaluate combinatorial regimens comprising cancer vaccines and OC standard-of-care.

Abstract

As the majority of ovarian cancer (OC) patients are diagnosed with metastatic disease, less than 40% will survive past 5 years after diagnosis. OC is characterized by a succession of remissions and recurrences. The most promising time point for immunotherapeutic interventions in OC is following debulking surgery. Accumulating evidence shows that T cells are important in OC; thus, cancer vaccines capable of eliciting antitumor T cells will be effective in OC treatment. In this review, we discuss different cancer vaccines and propose strategies for their incorporation into the OC standard-of-care regimens. Using the murine ID8 ovarian tumor model, we provide evidence that a cancer vaccine can be effectively combined with OC standard-of-care to achieve greater overall efficacy. We demonstrate several important similarities between the ID8 model and OC patients, in terms of response to immunotherapies, and the ID8 model can be an important tool for evaluating combinatorial regimens and clinical trial designs in OC. Other emerging models, including patient-derived xenograft and genetically engineered mouse models, are continuing to improve and can be useful for evaluating cancer vaccination therapies in the near future. Here, we provide a comprehensive review of the completed and current clinical trials evaluating cancer vaccines in OC.

Phase 1 open-label trial of intravenous administration of MVA-BN-brachyury-TRICOM vaccine in patients with advanced cancer

Background

MVA-BN-brachyury-TRICOM is a recombinant vector-based therapeutic cancer vaccine designed to induce an immune response against brachyury. Brachyury, a transcription factor overexpressed in advanced cancers, has been associated with treatment resistance, epithelial-to-mesenchymal transition, and metastatic potential. MVA-BN-brachyury-TRICOM has demonstrated immunogenicity and safety in previous clinical trials of subcutaneously administered vaccine. Preclinical studies have suggested that intravenous administration of therapeutic vaccines can induce superior CD8⁺ T cell responses, higher levels of systemic cytokine release, and stronger natural killer cell activation and proliferation. This is the first-in-human study of the intravenous administration of MVA-BN-brachyury-TRICOM.

Methods

Between January 2020 and March 2021, 13 patients were treated on a phase 1, open-label, 3+3 design, dose-escalation study at the National Institutes of Health Clinical Center. The study population was adults with advanced solid tumors and was enriched for chordoma, a rare sarcoma of the notochord that overexpresses brachyury. Vaccine was administered intravenously at three DLs on days 1, 22, and 43. Blood samples were taken to assess drug pharmacokinetics and immune activation. Imaging was conducted at baseline, 1 month, and 3 months post-treatment. The primary endpoint was safety and tolerability as determined by the frequency of dose-limiting toxicities; a secondary endpoint was determination of the recommended phase 2 dose.

Results

No dose-limiting toxicities were observed and no serious adverse events were attributed to the vaccine. Vaccine-related toxicities were consistent with class profile (ie, influenza-like symptoms). Cytokine release syndrome up to grade 2 was observed with no adverse outcomes. Dose-effect trend was observed for fever, chills/rigor, and hypotension. Efficacy analysis of objective response rate per RECIST 1.1 at the end of study showed one patient with a partial response, four with stable disease, and eight with progressive disease. Three patients with stable disease experienced clinical benefit in the form of improvement in pain. Immune correlatives showed T cell activation against brachyury and other tumor-associated cascade antigens.

Conclusions

Intravenous administration of MVA-BN-brachyury-TRICOM vaccine was safe and tolerable. Maximum tolerated dose was not reached. The maximum administered dose was 10⁹ infectious units every 3 weeks for three doses. This dose was selected as the recommended phase 2 dose.

Trial registration number

NCT04134312.

Multiple malignant tumors in a patient with familial chordoma, a case report

Background

Chordoma is a rare bone tumor that is typically resistant to chemotherapy and is associated with genetic abnormalities of the T-box transcription factor T (TBXT) gene, which encodes the transcription factor brachyury. Brachyury is felt to be a major contributor to the development of chordomas.

Case presentation

We describe a 67-year-old woman who developed an undifferentiated pleomorphic sarcoma in her thigh. Despite treatment with standard chemotherapy regimens, she had a rapidly progressive course of disease with pulmonary metastases and passed away 8 months from diagnosis with pulmonary complications. Her medical history was remarkable in that she had a spheno-occipital chordoma at age 39 and later developed multiple other tumors throughout her life including Hodgkin lymphoma and squamous cell carcinoma and basal cell carcinoma of the skin. She had a family history of chordoma and her family underwent extensive genetic study in the past and were found to have a duplication of the TBXT gene.

Conclusions

Brachyury has been found to associate with tumor progression, treatment resistance, and metastasis in various epithelial cancers, and it might play roles in tumorigenesis and aggressiveness in this patient with multiple rare tumors and germ line duplication of the TBXT gene. Targeting this molecule may be useful for some malignancies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01064-0.

Chordoma: Current status, problems, and future directions

Chordoma is a rare tumor that occurs along the axial spine in pediatrics and adults, with an incidence of approximately 350 cases per year in the United States. While typically described as slow-growing, many patients will eventually develop loco-regional relapse or metastatic disease with few treatment options. Despite numerous efforts over the last 10+ years, effective treatments for patients are lacking. As subtypes of chordoma are identified and described in more detail, further knowledge regarding the natural history of each type, tumor location, age differences, genomic variability, and an overall better understanding of chordoma may be the key to developing meaningful clinical trials and effective therapies for patients with chordoma.

Combinatorial Approaches for Cancer Treatment Using Oncolytic Viruses: Projecting the Perspectives through Clinical Trials Outcomes

Recent cancer immunotherapy breakthroughs have fundamentally changed oncology and revived the fading hope for a cancer cure. The immune checkpoint inhibitors (ICI) became an indispensable tool for the treatment of many malignant tumors. Alongside ICI, the application of oncolytic viruses in clinical trials is demonstrating encouraging outcomes. Dozens of combinations of oncolytic viruses with conventional radiotherapy and chemotherapy are widely used or studied, but it seems quite complicated to highlight the most effective combinations. Our review summarizes the results of clinical trials evaluating oncolytic viruses with or without genetic alterations in combination with immune checkpoint blockade, cytokines, antigens and other oncolytic viruses as well. This review is focused on the efficacy and safety of virotherapy and the most promising combinations based on the published clinical data, rather than presenting all oncolytic virus variations, which are discussed in comprehensive literature reviews. We briefly revise the research landscape of oncolytic viruses and discuss future perspectives in virus immunotherapy, in order to provide an insight for novel strategies of cancer treatment.

The Brighton Collaboration standardized template for collection of key information for risk/benefit assessment of a Modified Vaccinia Ankara (MVA) vaccine platform

The Brighton Collaboration Viral Vector Vaccines Safety Working Group (V3SWG) was formed to evaluate the safety and characteristics of live, recombinant viral vector vaccines. The Modified Vaccinia Ankara (MVA) vector system is being explored as a platform for development of multiple vaccines. This paper reviews the molecular and biological features specifically of the MVA-BN vector system, followed by a template with details on the safety and characteristics of an MVA-BN based vaccine against Zaire ebolavirus and other filovirus strains. The MVA-BN-Filo vaccine is based on a live, highly attenuated poxviral vector incapable of replicating in human cells and encodes glycoproteins of Ebola virus Zaire, Sudan virus and Marburg virus and the nucleoprotein of the Thai Forest virus. This vaccine has been approved in the European Union in July 2020 as part of a heterologous Ebola vaccination regimen. The MVA-BN vector is attenuated following over 500 serial passages in eggs, showing restricted host tropism and incompetence to replicate in human cells. MVA has six major deletions and other mutations of genes outside these deletions, which all contribute to the replication deficiency in human and other mammalian cells. Attenuation of MVA-BN was demonstrated by safe administration in immunocompromised mice and non-human primates. In multiple clinical trials with the MVA-BN backbone, more than 7800 participants have been vaccinated, demonstrating a safety profile consistent with other licensed, modern vaccines. MVA-BN has been approved as smallpox vaccine in Europe and Canada in 2013, and as smallpox and monkeypox vaccine in the US in 2019. No signal for inflammatory cardiac disorders was identified throughout the MVA-BN development program. This is in sharp contrast to the older, replicating vaccinia smallpox vaccines, which have a known risk for myocarditis and/or pericarditis in up to 1 in 200 vaccinees. MVA-BN-Filo as part of a heterologous Ebola vaccination regimen (Ad26.ZEBOV/MVA-BN-Filo) has undergone clinical testing including Phase III in West Africa and is currently in use in large scale vaccination studies in Central African countries. This paper provides a comprehensive picture of the MVA-BN vector, which has reached regulatory approvals, both as MVA-BN backbone for smallpox/monkeypox, as well as for the MVA-BN-Filo construct as part of an Ebola vaccination regimen, and therefore aims to provide solutions to prevent disease from high-consequence human pathogens.

Randomized, Double-Blind, Placebo-Controlled Phase II Study of Yeast-Brachyury Vaccine (GI-6301) in Combination with Standard-of-Care Radiotherapy in Locally Advanced, Unresectable Chordoma

BACKGROUND

Brachyury is a transcription factor overexpressed in chordoma and is associated with chemotherapy resistance and epithelial-to-mesenchymal transition. GI-6301 is a recombinant, heat-killed Saccharomyces cerevisiae yeast-based vaccine targeting brachyury. A previous phase I trial of GI-6301 demonstrated a signal of clinical activity in chordomas. This trial evaluated synergistic effects of GI-6301 vaccine plus radiation.

MATERIALS AND METHODS

Adults with locally advanced, unresectable chordoma were treated on a randomized, placebo-controlled trial. Patients received three doses of GI-6301 (80 × 107 yeast cells) or placebo followed by radiation, followed by continued vaccine or placebo until progression. Primary endpoint was overall response rate, defined as a complete response (CR) or partial response (PR) in the irradiated tumor site at 24 months. Immune assays were conducted to evaluate immunogenicity.

RESULTS

Between May 2015 and September 2019, 24 patients enrolled on the first randomized phase II study in chordoma. There was one PR in each arm; no CRs were observed. Median progressive-free survival for vaccine and placebo arms was 20.6 months (95% confidence interval [CI], 5.7-37.5 months) and 25.9 months (95% CI, 9.2-30.8 months), respectively. Hazard ratio was 1.02 (95% CI, 0.38-2.71). Vaccine was well tolerated with no vaccine-related serious adverse events. Preexisting brachyury-specific T cells were detected in most patients in both arms. Most patients developed T-cell responses during therapy, with no difference between arms in frequency or magnitude of response.

CONCLUSION

No difference in overall response rate was observed, leading to early discontinuation of this trial due to low conditional power to detect statistical difference at the planned end of accrual.

IMPLICATIONS FOR PRACTICE

Chordoma is a rare neoplasm lacking effective systemic therapies for advanced, unresectable disease. Lack of clinically actionable somatic mutations in chordoma makes development of targeted therapy quite challenging. While the combination of yeast-brachyury vaccine (GI-6301) and standard radiation therapy did not demonstrate synergistic antitumor effects, brachyury still remains a good target for developmental therapeutics in chordoma. Patients and their oncologists should consider early referral to centers with expertise in chordoma (or sarcoma) and encourage participation in clinical trials.

Tumor Immune Microenvironment during Epithelial-Mesenchymal Transition

Epithelial-mesenchymal transition (EMT) has been shown to play a critical role in tumor development from initiation to metastasis. EMT could be regarded as a continuum, with intermediate hybrid epithelial and mesenchymal phenotypes having high plasticity. Classical EMT is characterized by the phenotype change of epithelial cells to cells with mesenchymal properties, but EMT is also associated with multiple other molecular processes, including tumor immune evasion. Some previous studies have shown that EMT is associated with the cell number of immunosuppressive cells, such as myeloid-derived suppressor cells, and the expression of immune checkpoints, such as programmed cell death-ligand 1, in several cancer types. At the molecular level, EMT transcriptional factors, including Snail, Zeb1, and Twist1, produce or attract immunosuppressive cells or promote the expression of immunosuppressive checkpoint molecules via chemokine production, leading to a tumor immunosuppressive microenvironment. In turn, immunosuppressive factors induce EMT in tumor cells. This feedback loop between EMT and immunosuppression promotes tumor progression. For therapy directly targeting EMT has been challenging, the elucidation of the interactive regulation of EMT and immunosuppression is desirable for developing new therapeutic approaches in cancer. The combination of immune checkpoint inhibitors and immunotherapy targeting immunosuppressive cells could be a promising therapy for EMT.

Phase I study of a multitargeted recombinant Ad5 PSA/MUC-1/brachyury-based immunotherapy vaccine in patients with metastatic castration-resistant prostate cancer (mCRPC)

Background

Antitumor vaccines targeting tumor-associated antigens (TAAs) can generate antitumor immune response. A novel vaccine platform using adenovirus 5 (Ad5) vectors [E1–, E2b–] targeting three TAAs—prostate-specific antigen (PSA), brachyury, and MUC-1—has been developed. Both brachyury and the C-terminus of MUC-1 are overexpressed in metastatic castration-resistant prostate cancer (mCRPC) and have been shown to play an important role in resistance to chemotherapy, epithelial–mesenchymal transition, and metastasis. The transgenes for PSA, brachyury, and MUC-1 all contain epitope modifications for the expression of CD8+ T-cell enhancer agonist epitopes. We report here the first-in-human trial of this vaccine platform.

Methods

Patients with mCRPC were given concurrently three vaccines targeting PSA, brachyury, and MUC-1 at 5×10¹¹ viral particles (VP) each, subcutaneously every 3 weeks for a maximum of three doses (dose de-escalation cohort), followed by a booster vaccine every 8 weeks for 1 year (dose-expansion cohort only). The primary objective was to determine the safety and the recommended phase II dose. Immune assays and clinical responses were evaluated.

Results

Eighteen patients with mCRPC were enrolled between July 2018 and September 2019 and received at least one vaccination. Median PSA was 25.58 ng/mL (range, 0.65–1006 ng/mL). The vaccine was tolerable and safe, and no grade >3 treatment-related adverse events or dose-limiting toxicities (DLTs) were observed. One patient had a partial response, while five patients had confirmed PSA decline and five had stable disease for >6 months. Median progression-free survival was 22 weeks (95% CI: 19.1 to 34). Seventeen (100%) of 17 patients mounted T-cell responses to at least one TAA, whereras 8 (47%) of 17 patients mounted immune responses to all three TAAs. Multifunctional T-cell responses to PSA, MUC-1, and brachyury were also detected after vaccination in the majority of the patients.

Conclusions

Ad5 PSA/MUC-1/brachyury vaccine is well tolerated. The primary end points were met and there were no DLTs. The recommended phase II dose is 5×10¹¹ VP. The vaccine demonstrated clinical activity, including one partial response and confirmed PSA responses in five patients. Three patients with prolonged PSA responses received palliative radiation therapy. Further research is needed to evaluate the clinical benefit and immunogenicity of this vaccine in combination with other immuno-oncology agents and/or palliative radiation therapy.

Trial registration number

NCT03481816.

Improving the Odds in Advanced Breast Cancer With Combination Immunotherapy: Stepwise Addition of Vaccine, Immune Checkpoint Inhibitor, Chemotherapy, and HDAC Inhibitor in Advanced Stage Breast Cancer

Breast tumors commonly harbor low mutational burden, low PD-L1 expression, defective antigen processing/presentation, and an immunosuppressive tumor microenvironment (TME). In a malignancy mostly refractory to checkpoint blockade, there is an unmet clinical need for novel combination approaches that increase tumor immune infiltration and tumor control. Preclinical data have guided the development of this clinical trial combining 1) BN-Brachyury (a poxvirus vaccine platform encoding the tumor associated antigen brachyury), 2) bintrafusp alfa (a bifunctional protein composed of the extracellular domain of the TGF-βRII receptor (TGFβ "trap") fused to a human IgG1 anti-PD-L1), 3), entinostat (a class I histone deacetylase inhibitor), and 4) T-DM1 (ado-trastuzumab emtansine, a standard of care antibody-drug conjugate targeting HER2). We hypothesize that this tetratherapy will induce a robust immune response against HER2+ breast cancer with improved response rates through 1) expanding tumor antigen-specific effector T cells, natural killer cells, and immunostimulatory dendritic cells, 2) improving antigen presentation, and 3) decreasing inhibitory cytokines, regulatory T cells, and myeloid-derived suppressor cells. In an orthotopic HER2+ murine breast cancer model, tetratherapy induced high levels of antigen-specific T cell responses, tumor CD8+ T cell/Treg ratio, and augmented the presence of IFNγ- or TNFα-producing CD8+ T cells and IFNγ/TNFα bifunctional CD8+ T cells with increased cytokine production. Similar effects were observed in tumor CD4+ effector T cells. Based on this data, a phase 1b clinical trial evaluating the stepwise addition of BN-Brachyury, bintrafusp alfa, T-DM1 and entinostat in advanced breast cancer was designed. Arm 1 (TNBC) receives BN-Brachyury + bintrafusp alfa. Arm 2 (HER2+) receives T-DM1 + BN-Brachyury + bintrafusp alfa. After safety is established in Arm 2, Arm 3 (HER2+) will receive T-DM1 + BN-Brachyury + bintrafusp alfa + entinostat. Reimaging will occur every 2 cycles (1 cycle = 21 days). Arms 2 and 3 undergo research biopsies at baseline and after 2 cycles to evaluate changes within the TME. Peripheral immune responses will be evaluated. Co-primary objectives are response rate and safety. All arms employ a safety assessment in the initial six patients and a 2-stage Simon design for clinical efficacy (Arm 1 if ≥ three responses of eight then expand to 13 patients; Arms 2 and 3 if ≥ four responses of 14 then expand to 19 patients per arm). Secondary objectives include progression-free survival and changes in tumor infiltrating lymphocytes. Exploratory analyses include changes in peripheral immune cells and cytokines. To our knowledge, the combination of a vaccine, an anti-PD-L1 antibody, entinostat, and T-DM1 has not been previously evaluated in the preclinical or clinical setting. This trial (NCT04296942) is open at the National Cancer Institute (Bethesda, MD).

Standard of Care and Promising New Agents for the Treatment of Mesenchymal Triple-Negative Breast Cancer

The pathologic definition of triple negative breast cancer (TNBC) relies on the absence of expression of estrogen, progesterone and HER2 receptors. However, this BC subgroup is distinguished by a wide biological, molecular and clinical heterogeneity. Among the intrinsic TNBC subtypes, the mesenchymal type is defined by the expression of genes involved in the epithelial to mesenchymal transition, stromal interaction and cell motility. Moreover, it shows a high expression of genes involved in proliferation and an immune-suppressive microenvironment. Several molecular alterations along different pathways activated during carcinogenesis and tumor progression have been outlined and could be involved in immune evasion mechanisms. Furthermore, reverting epithelial to mesenchymal transition process could lead to the overcoming of immune-resistance. This paper reviews the current knowledge regarding the mesenchymal TNBC subtype and its response to conventional therapeutic strategies, as well as to some promising molecular target agents and immunotherapy. The final goal is a tailored combination of cytotoxic drugs, target agents and immunotherapy in order to restore immunocompetence in mesenchymal breast cancer patients.

Vaccine Increases the Diversity and Activation of Intratumoral T Cells in the Context of Combination Immunotherapy

Resistance to immune checkpoint blockade therapy has spurred the development of novel combinations of drugs tailored to specific cancer types, including non-inflamed tumors with low T-cell infiltration. Cancer vaccines can potentially be utilized as part of these combination immunotherapies to enhance antitumor efficacy through the expansion of tumor-reactive T cells. Utilizing murine models of colon and mammary carcinoma, here we investigated the effect of adding a recombinant adenovirus-based vaccine targeting tumor-associated antigens with an IL-15 super agonist adjuvant to a multimodal regimen consisting of a bifunctional anti-PD-L1/TGF-βRII agent along with a CXCR1/2 inhibitor. We demonstrate that the addition of vaccine induced a greater tumor infiltration with T cells highly positive for markers of proliferation and cytotoxicity. In addition to this enhancement of cytotoxic T cells, combination therapy showed a restructured tumor microenvironment with reduced T_regs and CD11b⁺Ly6G⁺ myeloid cells. Tumor-infiltrating immune cells exhibited an upregulation of gene signatures characteristic of a Th1 response and presented with a more diverse T-cell receptor (TCR) repertoire. These results provide the rationale for the addition of vaccine-to-immune checkpoint blockade-based therapies being tested in the clinic.

Disseminated cancer cells in breast cancer: Mechanism of dissemination and dormancy and emerging insights on therapeutic opportunities

Metastatic spread in breast cancer patients is the major driver of cancer-related deaths. A unique subset of cells disseminated from pre-invasive or primary tumor lesions are recognized as the main seeds for metastatic outgrowth. Disseminated cancer cells (DCCs) can migrate to distant organs and settle in a dormant state for a prolonged period until they emerge to overt metastases. Understanding the biology of breast cancer cells dissemination, dormancy and reactivation to form overt metastases has become an important focus. In this review, we discuss the recent advancements of molecular pathways involving breast cancer cell dissemination, role of chemokine-chemokine receptor networks in DCCs migration, DCCs phenotypic heterogeneity and unique genes signatures in tumor dormancy, microenvironmental regulation and specific niches that favors DCCs homing and dormancy. In addition, we also discuss recent findings relating to the role of immune response on DCC dissemination and dormancy. With recent advances in the field of immunotherapy/targeted therapy and its beneficial effects in cancer treatment, this review will focus on their impact on DCCs, reversal of stemness, tumor dormancy and metastatic relapse.

Fast Clearance of the SARS-CoV-2 Virus in a Patient Undergoing Vaccine Immunotherapy for Metastatic Chordoma: A Case Report

The emergence of the SARS-CoV-2 virus has been associated with perplexing clinical sequelae and phenomena that often have no clear link to the underlying infection. There is a wide spectrum of symptoms associated with infection, from minimal respiratory complaints to severe multi-organ failure, often resulting in death. Individuals with malignancies, particularly those whose treatments have left them immunocompromised or immunosuppressed, are among the patient populations thought to be at greater risk for more severe illness. A man with aggressive metastatic chordoma contracted the SARS-CoV-2 virus and was diagnosed with COVID-19 while undergoing intravenous brachyury vaccine immunotherapy. His disease course was remarkably mild, and the virus cleared rapidly. Despite a treatment delay of 3 months due to the COVID-19 pandemic, the patient’s disease has been stable and tumor-related pain has significantly improved. This suggests not only an intact, functional immune system, but also one that appears to have been responsive to cancer treatment. It has been suggested that individuals undergoing treatment for metastatic cancer are at greater risk of severe SARS-CoV-2-related illnesses and complications. While immunosuppression may be a problem, particularly in those receiving conventional chemotherapeutic agents, it is possible that the non-specific effects of immune-enhancing therapies may confer some protection against SARS-CoV-2.

Brachyury Is Associated with Glioma Differentiation and Response to Temozolomide

Glioblastomas (GBMs) are the most aggressive tumor type of the central nervous system, mainly due to their high invasiveness and innate resistance to radiotherapy and chemotherapy, with temozolomide (TMZ) being the current standard therapy. Recently, brachyury was described as a novel tumor suppressor gene in gliomas, and its loss was associated with increased gliomagenesis. Here, we aimed to explore the role of brachyury as a suppressor of glioma invasion, stem cell features, and resistance to TMZ. Using gene-edited glioma cells to overexpress brachyury, we found that brachyury-positive cells exhibit reduced invasive and migratory capabilities and stem cell features. Importantly, these brachyury-expressing cells have increased expression of differentiation markers, which corroborates the results from human glioma samples and in vivo tumors. Glioma cells treated with retinoic acid increased the differentiation status with concomitant increased expression of brachyury. We then selected TMZ-resistant (SNB-19) and TMZ-responsive (A172 and U373) cell lines to evaluate the role of brachyury in the response to TMZ treatment. We observed that both exogenous and endogenous brachyury activation, through overexpression and retinoic acid treatment, are associated with TMZ sensitization in glioma-resistant cell lines. In this study, we demonstrate that brachyury expression can impair aggressive glioma features associated with treatment resistance. Finally, we provide the first evidence that brachyury can be a potential therapeutic target in GBM patients who do not respond to conventional chemotherapeutic drugs.

The Importance of Cellular Immunity in the Development of Vaccines and Therapeutics for COVID-19

It is important to develop vaccines that can also mediate T-cell responses to SARS-CoV-2 to limit severity of infections, and to analyze the cellular immunome in the use of anti-SARS-CoV-2 therapeutics.

Emerging Therapeutic Targets in Chordomas: A Review of the Literature in the Genomic Era

Chordomas are rare primary malignant tumors of the bones that occur along the skull base, spine, and sacrum. Long-term survival and neurological outcome continue to be challenging with continued low percentages of long-term survival. Recent studies have used genome, exome, transcriptome, and proteome sequencing to assess the mutational profile of chordomas. Most notably, Brachyury, or T-protein, has been shown to be an early mutational event in chordoma evolution. Clinically actionable mutations, including in the PI3K pathway, were identified. Preliminary evidence suggests that there may be mutational differences associated with primary tumor location. In this study, we review the therapeutic landscape of chordomas and discuss emerging targets in the genomic era.

Recent advances in understanding and managing chordomas: an update

Chordomas are rare and difficult-to-treat tumors arising from the embryonic notochord. While surgery is the mainstay of treatment, and despite new techniques aimed at maximizing total tumoral resection, recurrence remains high and the probability of disease-free survival low. New breakthroughs in genetics, targeted molecular therapy, and heavy-particle beam therapy offer some promise as adjuvant treatments in addition to surgical resection. A multidisciplinary approach encompassing genetics, immunotherapy, radiation therapy, and surgery, at a facility experienced in the management of this complex disease, offers the best chance of survival and quality of life to patients while limiting the intrinsic morbidity of these treatments.

The Roles of Embryonic Transcription Factor BRACHYURY in Tumorigenesis and Progression

Transcription factor brachyury, with a DNA-binding T-domain, regulates posterior mesoderm formation and notochord development through binding with highly conserved palindromic consensus sequence in a variety of organisms. The absence of brachyury expression in majority of adult normal tissues and exclusive tumor-specific expression provides the potential to be developed into a novel and promising diagnostic and therapeutic target in cancer. As a sensitive and specific marker in the diagnosis of chordoma, brachyury protein has been verified to involve in the process of carcinogenesis and progression of chordoma and several epithelial carcinomas in various studies, but the mechanism by which brachyury promotes tumor cells migrate, invade and metastasis still remains less clear. To this end, we attempt to summarize the literature on the upstream regulatory pathway of brachyury transcription and downstream controlling network by brachyury activation, all of which involve in both the embryonic development and tumor progression. We present the respective correlation of brachyury expression with tumor progression, distant metastasis, survival rate and prognosis in several types of tumor samples (including chordoma, lung cancer, breast carcinoma, and prostate cancer), and various brachyury gain-of-function and loss-of-function experiments are summarized to explore its specific role in respective tumor cell line in vitro. In addition, we also discuss another two programs relating to brachyury function: epithelial-to-mesenchymal transition (EMT) and cell cycle control, both of which implicate in the regulation of brachyury on biological behavior of tumor cells. This review will provide an overview of the function of master transcriptional factor brachyury, compare the similarities and differences of its role between embryonic development and carcinogenesis, and list the evidence on which brachyury-target therapies have the potential to help control advanced cancer populations.

Cancer Vaccines and Oncolytic Viruses Exert Profoundly Lower Side Effects in Cancer Patients than Other Systemic Therapies: A Comparative Analysis

This review compares cytotoxic drugs, targeted therapies, and immunotherapies with regard to mechanisms and side effects. Targeted therapies relate to small molecule inhibitors. Immunotherapies include checkpoint inhibitory antibodies, chimeric antigen receptor (CAR) T-cells, cancer vaccines, and oncolytic viruses. All these therapeutic approaches fight systemic disease, be it micro-metastatic or metastatic. The analysis includes only studies with a proven therapeutic effect. A clear-cut difference is observed with regard to major adverse events (WHO grades 3-4). Such severe side effects are not observed with cancer vaccines/oncolytic viruses while they are seen with all the other systemic therapies. Reasons for this difference are discussed.

Tumor Plasticity and Resistance to Immunotherapy

Tumor cell plasticity exhibited as an epithelial-mesenchymal transition (EMT) has been identified as a major obstacle for the effective treatment of many cancers. This process, which involves the dedifferentiation of epithelial tumor cells towards a motile, metastatic, and mesenchymal tumor phenotype, mediates resistance to conventional therapies and small-molecule targeted therapies. In this review, we highlight current research correlating the role of tumor plasticity with resistance to current immunotherapy approaches and discuss future and ongoing combination immunotherapy strategies to reduce tumor cell plasticity-driven resistance in cancer.

Poxvirus Vectored Cytomegalovirus Vaccine to Prevent Cytomegalovirus Viremia in Transplant Recipients: A Phase 2, Randomized Clinical Trial

Background

Triplex vaccine was developed to enhance cytomegalovirus (CMV)-specific T cells and prevent CMV reactivation early after hematopoietic stem cell transplant (HCT).

Objective

To determine the safety and efficacy of Triplex.

Design

First-in-patient, phase 2 trial. (ClinicalTrials.gov: NCT02506933).

Setting

3 U.S. HCT centers.

Participants

102 CMV-seropositive HCT recipients at high risk for CMV reactivation.

Intervention

Intramuscular injections of Triplex or placebo were given on days 28 and 56 after HCT. Triplex is a recombinant attenuated poxvirus (modified vaccinia Ankara) expressing immunodominant CMV antigens.

Measurements

The primary outcomes were CMV events (CMV DNA level ≥1250 IU/mL, CMV viremia requiring antiviral treatment, or end-organ disease), nonrelapse mortality, and severe (grade 3 or 4) graft-versus-host disease (GVHD), all evaluated through 100 days after HCT, and grade 3 or 4 adverse events (AEs) within 2 weeks after vaccination that were probably or definitely attributable to injection.

Results

A total of 102 patients (51 per group) received the first vaccination, and 91 (89.2%) received both vaccinations (46 Triplex and 45 placebo). Reactivation of CMV occurred in 5 Triplex (9.8%) and 10 placebo (19.6%) recipients (hazard ratio, 0.46 [95% CI, 0.16 to 1.4]; P = 0.075). No Triplex recipient died of nonrelapse causes during the first 100 days or had serious AEs, and no grade 3 or 4 AEs related to vaccination were observed within 2 weeks after vaccination. Incidence of severe acute GVHD after injection was similar between groups (hazard ratio, 1.1 [CI, 0.53 to 2.4]; P = 0.23). Levels of long-lasting, pp65-specific T cells with effector memory phenotype were significantly higher in Triplex than placebo recipients.

Limitation

The lower-than-expected incidence of CMV events in the placebo group reduced the power of the trial.

Conclusion

No vaccine-associated safety concerns were identified. Triplex elicited and amplified CMV-specific immune responses, and fewer Triplex-vaccinated patients had CMV viremia.

Primary Funding Source

National Cancer Institute and Helocyte.

New Prospects for Molecular Targets for Chordomas

Chordomas are malignant, highly recurrent tumors of the midline skeleton that arise from the remnants of the notochord. The development of systemic therapy is critically important to ultimately managing this tumor. Several ongoing trials are attempting to use molecular targeted therapies for mutated pathways in recurrent and advanced chordomas and have shown promise. In addition, immunotherapies, including brachyury-directed vaccination and checkpoint inhibition, have also been attempted with encouraging results. This article discusses the major pathways that have been implicated in the pathogenesis of chordoma with an emphasis on molecular vulnerabilities that future therapies are attempting to exploit.

Phase I Trial of a Modified Vaccinia Ankara Priming Vaccine Followed by a Fowlpox Virus Boosting Vaccine Modified to Express Brachyury and Costimulatory Molecules in Advanced Solid Tumors

LESSONS LEARNED

Modified vaccinia Ankara-Bavarian Nordic (MVA-BN)-Brachyury followed by fowlpox virus-BN-Brachyury was well tolerated upon administration to patients with advanced cancer. Sixty-three percent of patients developed CD4+ and/or CD8+ T-cell responses to brachyury after vaccination. BN-Brachyury vaccine also induced T-cell responses against CEA and MUC1, which are cascade antigens, that is, antigens not encoded in the vaccines.

BACKGROUND

Brachyury, a transcription factor, plays an integral role in the epithelial-mesenchymal transition, metastasis, and tumor resistance to chemotherapy. It is expressed in many tumor types, and rarely in normal tissues, making it an ideal immunologic target. Bavarian Nordic (BN)-Brachyury consists of vaccination with modified vaccinia Ankara (MVA) priming followed by fowlpox virus (FPV) boosting, each encoding transgenes for brachyury and costimulatory molecules.

METHODS

Patients with metastatic solid tumors were treated with two monthly doses of MVA-brachyury s.c., 8 × 10⁸ infectious units (IU), followed by FPV-brachyury s.c., 1 × 10⁹ IU, for six monthly doses and then every 3 months for up to 2 years. The primary objective was to determine safety and tolerability.

RESULTS

Eleven patients were enrolled from March 2018 to July 2018 (one patient was nonevaluable). No dose-limiting toxicities were observed. The most common treatment-related adverse event was grade 1/2 injection-site reaction observed in all patients. Best overall response was stable disease in six patients, and the 6-month progression-free survival rate was 50%. T cells against brachyury and cascade antigens CEA and MUC1 were detected in the majority of patients.

CONCLUSION

BN-Brachyury vaccine is well tolerated and induces immune responses to brachyury and cascade antigens and demonstrates some evidence of clinical benefit.

Single peptides and combination modalities for triple negative breast cancer

Unlike other types of breast cancers (BCs), no specific therapeutic targets have been established for triple negative breast cancer (TNBC). Therefore, chemotherapy and radiotherapy are the only available adjuvant therapeutic choices for TNBC. New emerging reports show that TNBC is associated with higher numbers of intratumoral tumor infiltrating lymphocytes. This is indicative of host anti-TNBC immune surveillance and suggesting that immunotherapy can be considered as a therapeutic approach for TNBC management. Recent progress in molecular mechanisms of tumor-immune system interaction and cancer vaccine development studies, fast discoveries and FDA approvals of immune checkpoint inhibitors, chimeric antigen receptor T-cells, and oncolytic virotherapy have significantly attracted attention and research directions toward the immunotherapeutic approach to TNBC. Here in this review different aspects of TNBC immunotherapies including the host immune system-tumor interactions, the tumor microenvironment, the relevant molecular targets for immunotherapy, and clinical trials in the field are discussed.

A Phase I Dose-Escalation Trial of BN-CV301, a Recombinant Poxviral Vaccine Targeting MUC1 and CEA with Costimulatory Molecules

PURPOSE

BN-CV301 is a poxviral-based vaccine comprised of recombinant (rec.) modified vaccinia Ankara (MVA-BN-CV301; prime) and rec. fowlpox (FPV-CV301; boost). Like its predecessor PANVAC, BN-CV301 contains transgenes encoding tumor-associated antigens MUC1 and CEA as well as costimulatory molecules (B7.1, ICAM-1, and LFA-3). PANVAC was reengineered to make it safer and more antigenic.

PATIENTS AND METHODS

This open-label, 3+3 design, dose-escalation trial evaluated three dose levels (DL) of MVA-BN-CV301: one, two, or four subcutaneous injections of 4 × 10⁸ infectious units (Inf.U)/0.5 mL on weeks 0 and 4. All patients received FPV-CV301 subcutaneously at 1 × 10⁹ Inf.U/0.5 mL every 2 weeks for 4 doses, then every 4 weeks. Clinical and immune responses were evaluated.

RESULTS

There were no dose-limiting toxicities. Twelve patients enrolled on trial [dose level (DL) 1 = 3, DL2 = 3, DL3 = 6). Most side effects were seen with the prime doses and lessened with subsequent boosters. All treatment-related adverse events were temporary, self-limiting, grade 1/2, and included injection-site reactions and flu-like symptoms. Antigen-specific T cells to MUC1 and CEA, as well as to a cascade antigen, brachyury, were generated in most patients. Single-agent BN-CV301 produced a confirmed partial response (PR) in 1 patient and prolonged stable disease (SD) in multiple patients, most notably in KRAS-mutant gastrointestinal tumors. Furthermore, 2 patients with KRAS-mutant colorectal cancer had prolonged SD when treated with an anti-PD-L1 antibody following BN-CV301.

CONCLUSIONS

The BN-CV301 vaccine can be safely administered to patients with advanced cancer. Further studies of the vaccine in combination with other agents are planned.See related commentary by Repáraz et al., p. 4871.

Novel Modified Vaccinia Virus Ankara Vector Expressing Anti-apoptotic Gene B13R Delays Apoptosis and Enhances Humoral Responses

Modified vaccinia virus Ankara (MVA), an attenuated poxvirus, has been developed as a potential vaccine vector for use against cancer and multiple infectious diseases, including human immunodeficiency virus (HIV). MVA is highly immunogenic and elicits strong cellular and humoral responses in preclinical models and humans. However, there is potential to further enhance the immunogenicity of MVA, as MVA-infected cells undergo rapid apoptosis, leading to faster clearance of recombinant antigens and potentially blunting a greater response. Here, we generated MVA-B13R by replacing the fragmented 181R/182R genes of MVA with a functional anti-apoptotic gene, B13R, and confirmed its anti-apoptotic function against chemically induced apoptosis in vitro In addition, MVA-B13R showed a significant delay in induction of apoptosis in muscle cells derived from mice and humans, as well as in plasmacytoid dendritic cells (pDCs) and CD141+ DCs from rhesus macaques, compared to the induction of apoptosis in MVA-infected cells. MVA-B13R expressing simian immunodeficiency virus (SIV) Gag and Pol and HIV envelope (SHIV) (MVA-B13R/SHIV) produced higher levels of envelope in the supernatants than MVA/SHIV-infected DF-1 cells in vitro Immunization of BALB/c mice showed induction of higher levels of envelope-specific antibody-secreting cells and memory B cells, higher IgG antibody titers, and better persistence of antibody titers with MVA-B13R/SHIV than with MVA/SHIV. Gene set enrichment analysis of draining lymph node cells from day 1 after immunization showed negative enrichment for interferon responses in MVA-B13R/SHIV-immunized mice compared to the responses in MVA/SHIV-immunized mice. Taken together, these results demonstrate that restoring B13R functionality in MVA significantly delays MVA-induced apoptosis in muscle and antigen-presenting cells in vitro and augments vaccine-induced humoral immunity in mice.IMPORTANCE MVA is an attractive viral vector for vaccine development due to its safety and immunogenicity in multiple species and humans even under conditions of immunodeficiency. Here, to further improve the immunogenicity of MVA, we developed a novel vector, MVA-B13R, by replacing the fragmented anti-apoptotic genes 181R/182R with a functional version derived from vaccinia virus, B13R Our results show that MVA-B13R significantly delays apoptosis in antigen-presenting cells and muscle cells in vitro and augments vaccine-induced humoral immunity in mice, leading to the development of a novel vector for vaccine development against infectious diseases and cancer.

Vaccinia virus-mediated cancer immunotherapy: cancer vaccines and oncolytics

Cancer vaccines and oncolytic immunotherapy are promising treatment strategies with potential to provide greater clinical benefit to patients with advanced-stage cancer. In particular, recombinant vaccinia viruses (VV) hold great promise as interventional agents. In this article, we first summarize the current understanding of virus biology and viral genes involved in host-virus interactions to further improve the utility of these agents in therapeutic applications. We then discuss recent findings from basic and clinical studies using VV as cancer vaccines and oncolytic immunotherapies. Despite encouraging results gleaned from translational studies in animal models, clinical trials implementing VV vectors alone as cancer vaccines have yielded largely disappointing results. However, the combination of VV vaccines with alternate forms of standard therapies has resulted in superior clinical efficacy. For instance, combination regimens using TG4010 (MVA-MUC1-IL2) with first-line chemotherapy in advanced-stage non-small cell lung cancer or combining PANVAC with docetaxel in the setting of metastatic breast cancer have clearly provided enhanced clinical benefits to patients. Another novel cancer vaccine approach is to stimulate anti-tumor immunity via STING activation in Batf3-dependent dendritic cells (DC) through the use of replication-attenuated VV vectors. Oncolytic VVs have now been engineered for improved safety and superior therapeutic efficacy by arming them with immune-stimulatory genes or pro-apoptotic molecules to facilitate tumor immunogenic cell death, leading to enhanced DC-mediated cross-priming of T cells recognizing tumor antigens, including neoantigens. Encouraging translational and early phase clinical results with Pexa-Vec have matured into an ongoing global phase III trial for patients with hepatocellular carcinoma. Combinatorial approaches, most notably those using immune checkpoint blockade, have produced exciting pre-clinical results and warrant the development of innovative clinical studies. Finally, we discuss major hurdles that remain in the field and offer some perspectives regarding the development of next generation VV vectors for use as cancer therapeutics.

Poxvirus-based vector systems and the potential for multi-valent and multi-pathogen vaccines

INTRODUCTION

With the increasing number of vaccines and vaccine-preventable diseases, the pressure to generate multi-valent and multi-pathogen vaccines grows. Combining individual established vaccines to generate single-shot formulations represents an established path, with significant ensuing public health and cost benefits. Poxvirus-based vector systems have the capacity for large recombinant payloads and have been widely used as platforms for the development of recombinant vaccines encoding multiple antigens, with considerable clinical trials activity and a number of registered and licensed products.

AREAS COVERED

Herein we discuss design strategies, production processes, safety issues, regulatory hurdles and clinical trial activities, as well as pertinent new technologies such as systems vaccinology and needle-free delivery. Literature searches used PubMed, Google Scholar and clinical trials registries, with a focus on the recombinant vaccinia-based systems, Modified Vaccinia Ankara and the recently developed Sementis Copenhagen Vector.

EXPERT COMMENTARY

Vaccinia-based platforms show considerable promise for the development of multi-valent and multi-pathogen vaccines, especially with recent developments in vector technologies and manufacturing processes. New methodologies for defining immune correlates and human challenge models may also facilitate bringing such vaccines to market.

Quick efficacy seeking trial (QuEST1): a novel combination immunotherapy study designed for rapid clinical signal assessment metastatic castration-resistant prostate cancer

Advances in immunotherapy utilizing immune checkpoint inhibitors (ICIs) have transformed the treatment landscapes of several malignancies in recent years. Oncologists are now tasked with extending these benefits to a greater number of patients and tumor types. Metastatic castration-resistant prostate cancer (mCRPC) infrequently responds to ICIs, while the cellular vaccine approved for mCRPC, sipuleucel-T, provides a 4-month survival benefit but does not produce clinical responses as monotherapy. However, many novel and generally well-tolerated immune oncology agents with potential for immune synergy and/or additive effects are undergoing clinical development. This availability presents opportunities to develop adaptive-design combination clinical trials aimed to generate, expand, and facilitate antitumor immune responses. Here we describe a currently accruing phase I/II trial (NCT03493945) testing a brachyury-targeted antitumor vaccine, TGF-β TRAP/anti-PD-L1 antibody, an IL-15 agonist, and an IDO1 inhibitor in mCRPC.

TRIAL REGISTRATION

This trial ( NCT03493945 ) was registered in National Clinical Trials on April 11th 2018.

The Interplay between Circulating Tumor Cells and the Immune System: From Immune Escape to Cancer Immunotherapy

Circulating tumor cells (CTCs) have aroused increasing interest not only in mechanistic studies of metastasis, but also for translational applications, such as patient monitoring, treatment choice, and treatment change due to tumor resistance. In this review, we will assess the state of the art about the study of the interactions between CTCs and the immune system. We intend to analyze the impact that the cells of the immune system have in limiting or promoting the metastatic capability of CTCs. To this purpose, we will examine studies that correlate CTCs, immune cells, and patient prognosis, and we will also discuss relevant animal models that have contributed to the understanding of the mechanisms of immune-mediated metastasis. We will then consider some studies in which CTCs seem to play a promising role in monitoring cancer patients during immunotherapy regimens. We believe that, from an accurate and profound knowledge of the interactions between CTCs and the immune system, new immunotherapeutic strategies against cancer might emerge in the future.

Loss of the Cyclin-Dependent Kinase Inhibitor 1 in the Context of Brachyury-Mediated Phenotypic Plasticity Drives Tumor Resistance to Immune Attack

The acquisition of mesenchymal features by carcinoma cells is now recognized as a driver of metastasis and tumor resistance to a range of anticancer therapeutics, including chemotherapy, radiation, and certain small-molecule targeted therapies. With the recent successful implementation of immunotherapies for the treatment of various types of cancer, there is growing interest in understanding whether an immunological approach could be effective at eradicating carcinoma cells bearing mesenchymal features. Recent studies, however, demonstrated that carcinoma cells that have acquired mesenchymal features may also exhibit decreased susceptibility to lysis mediated by immune effector cells, including antigen-specific CD8⁺ T cells, innate natural killer (NK), and lymphokine-activated killer (LAK) cells. Here, we investigated the mechanism involved in the immune resistance of carcinoma cells that express very high levels of the transcription factor brachyury, a molecule previously shown to drive the acquisition of mesenchymal features by carcinoma cells. Our results demonstrate that very high levels of brachyury expression drive the loss of the cyclin-dependent kinase inhibitor 1 (p21CIP1, p21), an event that results in decreased tumor susceptibility to immune-mediated lysis. We show here that reconstitution of p21 expression markedly increases the lysis of brachyury-high tumor cells mediated by antigen-specific CD8⁺ T cells, NK, and LAK cells, TNF-related apoptosis-inducing ligand, and chemotherapy. Several reports have now demonstrated a role for p21 loss in cancer as an inducer of the epithelial–mesenchymal transition. The results from the present study situate p21 as a central player in many of the aspects of the phenomenon of brachyury-mediated mesenchymalization of carcinomas, including resistance to chemotherapy and immune-mediated cytotoxicity. We also demonstrate here that the defects in tumor cell death described in association with very high levels of brachyury could be alleviated via the use of a WEE1 inhibitor. Several vaccine platforms targeting brachyury have been developed and are undergoing clinical evaluation. These studies provide further rationale for the use of WEE1 inhibition in combination with brachyury-based immunotherapeutic approaches.

Cancer immunotherapy beyond immune checkpoint inhibitors

Malignant cells have the capacity to rapidly grow exponentially and spread in part by suppressing, evading, and exploiting the host immune system. Immunotherapy is a form of oncologic treatment directed towards enhancing the host immune system against cancer. In recent years, manipulation of immune checkpoints or pathways has emerged as an important and effective form of immunotherapy. Agents that target cytotoxic T lymphocyte-associated molecule-4 (CTLA-4), programmed cell death receptor-1 (PD-1), and programmed cell death ligand-1 (PD-L1) are the most widely studied and recognized. Immunotherapy, however, extends beyond immune checkpoint therapy by using new molecules such as chimeric monoclonal antibodies and antibody drug conjugates that target malignant cells and promote their destruction. Genetically modified T cells expressing chimeric antigen receptors are able to recognize specific antigens on cancer cells and subsequently activate the immune system. Native or genetically modified viruses with oncolytic activity are of great interest as, besides destroying malignant cells, they can increase anti-tumor activity in response to the release of new antigens and danger signals as a result of infection and tumor cell lysis. Vaccines are also being explored, either in the form of autologous or allogenic tumor peptide antigens, genetically modified dendritic cells that express tumor peptides, or even in the use of RNA, DNA, bacteria, or virus as vectors of specific tumor markers. Most of these agents are yet under development, but they promise to be important options to boost the host immune system to control and eliminate malignancy. In this review, we have provided detailed discussion of different forms of immunotherapy agents other than checkpoint-modifying drugs. The specific focus of this manuscript is to include first-in-human phase I and phase I/II clinical trials intended to allow the identification of those drugs that most likely will continue to develop and possibly join the immunotherapeutic arsenal in a near future.