Vaccination of renal cell cancer patients with modified vaccinia Ankara delivering the tumor antigen 5T4 (TroVax) alone or administered in combination with interferon-alpha (IFN-alpha): a phase 2 trial

A randomized phase II trial to examine modified vaccinia Ankara-5T4 vaccine in patients with relapsed asymptomatic ovarian cancer (TRIOC)

BACKGROUND

Immunotherapy directed at 5T4 tumor antigen may delay the need for further chemotherapy. An attenuated modified vaccinia Ankara virus containing the gene encoding for 5T4 (MVA-5T4) was studied in asymptomatic relapsed ovarian cancer.

OBJECTIVE

To assess the effectiveness and safety of MVA-5T4 as treatment for asymptomatic relapsed ovarian cancer.

METHODS

TRIOC was a phase II randomized (1:1), placebo-controlled, double-blind multicenter study. The primary aim was to assess the effectiveness and safety of MVA-5T4 as a treatment for asymptomatic patients with relapsed ovarian cancer. Eligible patients had International Federation of Gynecology and Obstetrics (FIGO) stage IC1-III or IVA epithelial ovarian, fallopian tube, or primary peritoneal carcinoma, Eastern Cooperative Oncology Group (ECOG) 0-1, with relapse defined by a rise in CA-125 to twice the upper limit of normal or low-volume disease on CT scan. The primary endpoint was disease progression (including deaths from ovarian cancer) at 25 weeks. Following a brief suspension, the trial restarted as a single-arm study. The revised single-arm design required 45 evaluable patients treated with MVA-5T4 to detect a 25-week progression rate of 50%, assuming an expected 70% rate without MVA-5T4; 85% power with one-sided 5% significance.

RESULTS

A total of 94 eligible patients were recruited, median age was 65 years (range 42-82), median follow-up 34 months (range 2-46). Overall, 59 patients received MVA-5T4 and 35 patients received placebo. The median number of MVA-5T4 injections received was 7 (range 0-9), compared with a median of 6 (range 1-12) for patients receiving placebo. Median progression-free survival was the same in both arms (3.0 months). The 25-week progression rate was similar in both arms: 80.0% for patients treated with MVA-5T4 and 85.7% for those receiving placebo (risk difference -5.7%, 95% CI -21.4% to 10.0%). Median time to clinical intervention was improved with MVA-5T4: 7.6 months (range 6.7-9.5) vs 5.6 (range 4.9-7.6), CONCLUSION: MVA-5T4 vaccination in patients with asymptomatic relapse was well-tolerated but did not improve the progression rate at 25 weeks. The majority of patients who received MVA-5T4 had clinical intervention later than those assigned to placebo.

TRIAL REGISTRATION NUMBER

NCT01556841.

Multifaceted applications of genetically modified microorganisms: A biotechnological revolution

BACKGROUND

Genetically modified microorganisms specifically bacteria, viruses, algae and fungi are the novel approaches used in field of healthcare due to more efficacious and targeted delivery in comparison to conventional approaches.

OBJECTIVE

This review article focuses on applications of genetically modified microorganisms such as bacteria, virus, fungi, virus, etc. in treatment of cancer, obesity, and HIV. Gut microbiome is used to cause metabolic disorders but use of genetically-modified bacteria alters the gut microbiota and delivers the therapeutically effective drug in the treatment of obesity.

METHODS

To enhance the activity of different microorganisms for treatment, they are genetically modified by incorporating a fragment into the fungi filaments, integrating a strain into the bacteria, engineer a live-virus with a peptide using methods such as amelioration of NAPE synthesis, silica immobilization, polyadenylation, electrochemical, etc. Results: The development of newer microbial strains using genetic modifications offers higher precision, enhance the molecular multiplicity, prevent the degradation of microbes in atmospheric temperature and reduce the concerned side-effect for therapeutic application. Other side genetically modified microorganisms are used in non-healthcare based sector like generation of electricity, purification of water, bioremediation process etc. Conclusions: The bio-engineered micro-organisms with genetic modification prove the advantage over the treatment of various diseases like cancer, diabetes, malaria, organ regeneration, inflammatory bowel disease, etc. The article provides the insights of various applications of genetically modified microbes in various arena with its implementation for the regulatory approval.

Development of CMV-CD19 bi-specific CAR T cells with post-infusion in vivo boost using an anti-CMV vaccine

Adoptive transfer of in vitro expanded, chimeric antigen receptor (CAR)-redirected CD19-specific T cells can induce dramatic disease regression in patients with leukemia and lymphomas. However, the full potential of this emerging modality is hampered in some cancer settings by a significant rate of therapeutic failure arising from the attenuated engraftment and persistence of CAR-redirected T cells, and tumor relapse following adoptive transfer. Here, we discuss an advanced strategy that facilitates post-infusion in vivo boosting of CAR T cells via CMV vaccination, to mediate durable remission of B cell malignancies by engrafting a CAR molecule onto a CMV-specific T cell. We also discuss a feasible and unique platform for the generation of the CMV-CD19CAR T cells for clinical application. This new approach would overcome multiple challenges in current CAR T cell technology including: short T cell persistence, limited duration of response, and inability to re-stimulate T cells after relapse or persistent disease.

DNA and modified vaccinia Ankara prime-boost vaccination generates strong CD8+ T cell responses against minor histocompatibility antigen HA-1

Allogeneic immune responses underlie the graft-versus-leukaemia effect of stem cell transplantation, but disease relapse occurs in many patients. Minor histocompatibility antigen (mHAg) peptides mediate alloreactive T cell responses and induce graft-versus-leukaemia responses when expressed on patient haematopoietic tissue. We vaccinated nine HA-1-negative donors against HA-1 with a 'prime-boost' protocol of either two or three DNA 'priming' vaccinations prior to 'boost' with modified vaccinia Ankara (MVA). HA-1-specific CD8+ T cell responses were observed in seven donors with magnitude up to 1·5% of total CD8+ T cell repertoire. HA-1-specific responses peaked two weeks post-MVA challenge and were measurable in most donors after 12 months. HA-1-specific T cells demonstrated strong cytotoxic activity and lysed target cells with endogenous HA-1 protein expression. The pattern of T cell receptor (TCR) usage by HA-1-specific T cells revealed strong conservation of T cell receptor beta variable 7-9 (TRBV7-9) usage between donors. These findings describe one of the strongest primary peptide-specific CD8+ T cell responses yet recorded to a DNA-MVA prime-boost regimen and this may reflect the strong immunogenicity of mHAg peptides. Prime-boost vaccination in donors or patients may prove of substantial benefit in boosting graft-versus-leukaemia responses.

Current Advance of Immune Evasion Mechanisms and Emerging Immunotherapies in Renal Cell Carcinoma

Renal cell carcinoma is a highly heterogeneous cancer group, and the complex microenvironment of the tumor provides appropriate immune evasion opportunities. The molecular mechanism of immune escape in renal cell carcinoma is currently a hot issue, focusing primarily on the major complex of histocompatibility, immunosuppressive cells, their secreted immunosuppressive cytokines, and apoptosis molecule signal transduction. Immunotherapy is the best treatment option for patients with metastatic or advanced renal cell carcinoma and combination immunotherapy based on a variety of principles has shown promising prospects. Comprehensive and in-depth knowledge of the molecular mechanism of immune escape in renal cell carcinoma is of vital importance for the clinical implementation of effective therapies. The goal of this review is to address research into the mechanisms of immune escape in renal cell carcinoma and the use of the latest immunotherapy. In addition, we are all looking forward to the latest frontiers of experimental combination immunotherapy.

Current status of antigen-specific T-cell immunotherapy for advanced renal-cell carcinoma

In renal-cell carcinoma (RCC), tumor-reactive T-cell responses can occur spontaneously or in response to systemic immunotherapy with cytokines and immune checkpoint inhibitors. Cancer vaccines and engineered T-cell therapies are designed to selectively augment tumor antigen-specific CD8⁺ T-cell responses with the goal to elicit tumor regression and avoid toxicities associated with nonspecific immunotherapies. In this review, we provide an overview of the central role of T-cell immunity in the treatment of advanced RCC. Clinical outcomes for antigen-targeted vaccines or other T-cell-engaging therapies for RCC are summarized and evaluated, and emerging new strategies to enhance the effectiveness of antigen-specific therapy for RCC are discussed.

IFN-Alpha-Mediated Differentiation of Dendritic Cells for Cancer Immunotherapy: Advances and Perspectives

The past decade has seen tremendous developments in novel cancer therapies through targeting immune-checkpoint molecules. However, since increasing the presentation of tumor antigens remains one of the major issues for eliciting a strong antitumor immune response, dendritic cells (DC) still hold a great potential for the development of cancer immunotherapy. A considerable body of evidence clearly demonstrates the importance of the interactions of type I IFN with the immune system for the generation of a durable antitumor response through its effects on DC. Actually, highly active DC can be rapidly generated from blood monocytes in vitro in the presence of IFN-α (IFN-DC), suitable for therapeutic vaccination of cancer patients. Here we review how type I IFN can promote the ex vivo differentiation of human DC and orientate DC functions towards the priming and expansion of protective antitumor immune responses. New epigenetic elements of control on activation of the type I IFN signal will be highlighted. We also review a few clinical trials exploiting IFN-DC in cancer vaccination and discuss how IFN-DC could be exploited for the design of effective strategies of cancer immunotherapy as a monotherapy or in combination with immune-checkpoint inhibitors or immunomodulatory drugs.

Combination Treatment with an Antibody-Drug Conjugate (A1mcMMAF) Targeting the Oncofetal Glycoprotein 5T4 and Carboplatin Improves Survival in a Xenograft Model of Ovarian Cancer

Background

Recurrence occurs in over 75% of women with epithelial ovarian cancer despite optimal treatment. Selectively killing tumour cells thought to initiate relapse using an antibody–drug conjugate could prolong progression-free survival and offer an improved side-effect profile. A1mcMMAF is an antibody–drug conjugate designed to target cells expressing the tumour-associated antigen 5T4. It has shown to be efficacious in various cell line models and have a greater impact when combined with routine chemotherapeutic regimes.

Objectives

This study aims to explore the potential for the use of a 5T4 antibody–drug conjugate in women with ovarian cancer both as a monotherapy and in combination with platinum-based chemotherapy.

Methods

Immunohistochemical analysis was used to assess 5T4 expression in tumours from patients with ovarian cancer. Effectiveness of A1mcMMAF therapy as a single agent and in combination with carboplatin was assessed in vitro in the ovarian cancer cell line SKOV3 and confirmed in vivo using a serial bioluminescence assay in a SKOV3 xenograft model of ovarian cancer.

Results

5T4 is confirmed as suitably expressed in epithelial ovarian cancers prior to adjuvant therapy and is an independent predictor of poor survival. A1mcMMAF showed specific activity, both in vitro and in vivo, against SKOV3 ovarian cancer cells. When used in combination with carboplatin, in vivo tumour growth was inhibited resulting in prolonged survival in a SKOV3 xenograft model.

Conclusions

These data support further investigation of A1mcMMAF in combination with platinum-based chemotherapy in ovarian and other cancer treatments.

Electronic supplementary material

The online version of this article (10.1007/s11523-019-00650-8) contains supplementary material, which is available to authorized users.

Preclinical development of T-cell receptor-engineered T-cell therapy targeting the 5T4 tumor antigen on renal cell carcinoma

5T4 (trophoblast glycoprotein, TPBG) is a transmembrane tumor antigen expressed on more than 90% of primary renal cell carcinomas (RCC) and a wide range of human carcinomas but not on most somatic adult tissues. The favorable expression pattern has encouraged the development and clinical testing of 5T4-targeted antibody and vaccine therapies. 5T4 also represents a compelling and unexplored target for T-cell receptor (TCR)-engineered T-cell therapy. Our group has previously isolated high-avidity CD8⁺ T-cell clones specific for an HLA-A2-restricted 5T4 epitope (residues 17-25; 5T4_p17). In this report, targeted single-cell RNA sequencing was performed on 5T4_p17-specific T-cell clones to sequence the highly variable complementarity-determining region 3 (CDR3) of T-cell receptor α chain (TRA) and β chain (TRB) genes. Full-length TRA and TRB sequences were cloned into lentiviral vectors and transduced into CD8⁺ T-cells from healthy donors. Redirected effector T-cell function against 5T4_p17 was measured by cytotoxicity and cytokine release assays. Seven unique TRA-TRB pairs were identified. All seven TCRs exhibited high expression on CD8⁺ T-cells with transduction efficiencies from 59 to 89%. TCR-transduced CD8⁺ T-cells demonstrated redirected cytotoxicity and cytokine release in response to 5T4_p17 on target-cells and killed 5T4⁺/HLA-A2⁺ kidney-, breast-, and colorectal-tumor cell lines as well as primary RCC tumor cells in vitro. TCR-transduced CD8⁺ T-cells also detected presentation of 5T4_p17 in TAP1/2-deficient T2 target-cells. TCR-transduced T-cells redirected to recognize the 5T4_p17 epitope from a broadly shared tumor antigen are of interest for future testing as a cellular immunotherapy strategy for HLA-A2⁺ subjects with 5T4⁺ tumors.

Type I interferons and dendritic cells in cancer immunotherapy

Type I interferons (IFNs) facilitate cancer immunosurveillance, antitumor immunity and antitumor efficacy of conventional cell death-inducing therapies (chemotherapy/radiotherapy) as well as immunotherapy. Moreover, it is clear that dendritic cells (DCs) play a significant role in aiding type I IFN-driven immunity. Owing to these antitumor properties several immunotherapies involving, or inducing, type I IFNs have received considerable clinical attention, e.g., recombinant IFNα2 or agonists targeting pattern recognition receptor (PRR) pathways like Toll-like receptors (TLRs), cGAS-STING or RIG-I/MDA5/MAVS. A series of preclinical and clinical evidence concurs that the success of anticancer therapy hinges on responsiveness of both cancer cells and DCs to type I IFNs. In this article, we discuss this link between type I IFNs and DCs in the context of cancer biology, with particular attention to mechanisms behind type I IFN production, their impact on DC driven anticancer immunity, and the implications of this for cancer immunotherapy, including DC-based vaccines.

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.

Recombinant Viruses for Cancer Therapy

Recombinant viruses are novel therapeutic agents that can be utilized for treatment of various diseases, including cancers. Recombinant viruses can be engineered to express foreign transgenes and have a broad tropism allowing gene expression in a wide range of host cells. They can be selected or designed for specific therapeutic goals; for example, recombinant viruses could be used to stimulate host immune response against tumor-specific antigens and therefore overcome the ability of the tumor to evade the host's immune surveillance. Alternatively, recombinant viruses could express immunomodulatory genes which stimulate an anti-cancer immune response. Oncolytic viruses can replicate specifically in tumor cells and induce toxic effects leading to cell lysis and apoptosis. However, each of these approaches face certain difficulties that must be resolved to achieve maximum therapeutic efficacy. In this review we discuss actively developing approaches for cancer therapy based on recombinant viruses, problems that need to be overcome, and possible prospects for further development of recombinant virus based therapy.

Novel immunotherapy in metastatic renal cell carcinoma

Despite the rapid development of therapeutic modalities for metastatic renal cell carcinoma (mRCC) over the past decade to include a number of targeted antiangiogenic therapies and traditional immunotherapy, such as high-dose interleukin-2 and interferon-α, mRCC continues to be associated with poor prognosis. Currently, several novel immunotherapy agents, such as cancer vaccines, adoptive cell therapy, and checkpoint inhibitors, such as programmed cell death-1 (PD-1 present on T cells), one of its ligands (PD-L1 present on antigen-presenting cells and tumor cells), and cytotoxic T-lymphocyte-associated protein-4 pathways, are being studied in mRCC and are showing promise as important steps in the management of this disease. This review summarizes the current landscape of standard and emerging immune therapeutics and other modalities for mRCC.

Immunotherapy for metastatic renal cell carcinoma

BACKGROUND

Since the mid-2000s, the field of metastatic renal cell carcinoma (mRCC) has experienced a paradigm shift from non-specific therapy with broad-acting cytokines to specific regimens, which directly target the cancer, the tumour microenvironment, or both.Current guidelines recommend targeted therapies with agents such as sunitinib, pazopanib or temsirolimus (for people with poor prognosis) as the standard of care for first-line treatment of people with mRCC and mention non-specific cytokines as an alternative option for selected patients.In November 2015, nivolumab, a checkpoint inhibitor directed against programmed death-1 (PD-1), was approved as the first specific immunotherapeutic agent as second-line therapy in previously treated mRCC patients.

OBJECTIVES

To assess the effects of immunotherapies either alone or in combination with standard targeted therapies for the treatment of metastatic renal cell carcinoma and their efficacy to maximize patient benefit.

SEARCH METHODS

We searched the Cochrane Library, MEDLINE (Ovid), Embase (Ovid), ISI Web of Science and registers of ongoing clinical trials in November 2016 without language restrictions. We scanned reference lists and contacted experts in the field to obtain further information.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-RCTs with or without blinding involving people with mRCC.

DATA COLLECTION AND ANALYSIS

We collected and analyzed studies according to the published protocol. Summary statistics for the primary endpoints were risk ratios (RRs) and mean differences (MD) with their 95% confidence intervals (CIs). We rated the quality of evidence using GRADE methodology and summarized the quality and magnitude of relative and absolute effects for each primary outcome in our 'Summary of findings' tables.

MAIN RESULTS

We identified eight studies with 4732 eligible participants and an additional 13 ongoing studies. We categorized studies into comparisons, all against standard therapy accordingly as first-line (five comparisons) or second-line therapy (one comparison) for mRCC.Interferon (IFN)-α monotherapy probably increases one-year overall mortality compared to standard targeted therapies with temsirolimus or sunitinib (RR 1.30, 95% CI 1.13 to 1.51; 2 studies; 1166 participants; moderate-quality evidence), may lead to similar quality of life (QoL) (e.g. MD -5.58 points, 95% CI -7.25 to -3.91 for Functional Assessment of Cancer - General (FACT-G); 1 study; 730 participants; low-quality evidence) and may slightly increase the incidence of adverse events (AEs) grade 3 or greater (RR 1.17, 95% CI 1.03 to 1.32; 1 study; 408 participants; low-quality evidence).There is probably no difference between IFN-α plus temsirolimus and temsirolimus alone for one-year overall mortality (RR 1.13, 95% CI 0.95 to 1.34; 1 study; 419 participants; moderate-quality evidence), but the incidence of AEs of 3 or greater may be increased (RR 1.30, 95% CI 1.17 to 1.45; 1 study; 416 participants; low-quality evidence). There was no information on QoL.IFN-α alone may slightly increase one-year overall mortality compared to IFN-α plus bevacizumab (RR 1.17, 95% CI 1.00 to 1.36; 2 studies; 1381 participants; low-quality evidence). This effect is probably accompanied by a lower incidence of AEs of grade 3 or greater (RR 0.77, 95% CI 0.71 to 0.84; 2 studies; 1350 participants; moderate-quality evidence). QoL could not be evaluated due to insufficient data.Treatment with IFN-α plus bevacizumab or standard targeted therapy (sunitinib) may lead to similar one-year overall mortality (RR 0.37, 95% CI 0.13 to 1.08; 1 study; 83 participants; low-quality evidence) and AEs of grade 3 or greater (RR 1.18, 95% CI 0.85 to 1.62; 1 study; 82 participants; low-quality evidence). QoL could not be evaluated due to insufficient data.Treatment with vaccines (e.g. MVA-5T4 or IMA901) or standard therapy may lead to similar one-year overall mortality (RR 1.10, 95% CI 0.91 to 1.32; low-quality evidence) and AEs of grade 3 or greater (RR 1.16, 95% CI 0.97 to 1.39; 2 studies; 1065 participants; low-quality evidence). QoL could not be evaluated due to insufficient data.In previously treated patients, targeted immunotherapy (nivolumab) probably reduces one-year overall mortality compared to standard targeted therapy with everolimus (RR 0.70, 95% CI 0.56 to 0.87; 1 study; 821 participants; moderate-quality evidence), probably improves QoL (e.g. RR 1.51, 95% CI 1.28 to 1.78 for clinically relevant improvement of the FACT-Kidney Symptom Index Disease Related Symptoms (FKSI-DRS); 1 study, 704 participants; moderate-quality evidence) and probably reduces the incidence of AEs grade 3 or greater (RR 0.51, 95% CI 0.40 to 0.65; 1 study; 803 participants; moderate-quality evidence).

AUTHORS' CONCLUSIONS

Evidence of moderate quality demonstrates that IFN-α monotherapy increases mortality compared to standard targeted therapies alone, whereas there is no difference if IFN is combined with standard targeted therapies. Evidence of low quality demonstrates that QoL is worse with IFN alone and that severe AEs are increased with IFN alone or in combination. There is low-quality evidence that IFN-α alone increases mortality but moderate-quality evidence on decreased AEs compared to IFN-α plus bevacizumab. Low-quality evidence shows no difference for IFN-α plus bevacizumab compared to sunitinib with respect to mortality and severe AEs. Low-quality evidence demonstrates no difference of vaccine treatment compared to standard targeted therapies in mortality and AEs, whereas there is moderate-quality evidence that targeted immunotherapies reduce mortality and AEs and improve QoL.

5T4 oncofoetal antigen: an attractive target for immune intervention in cancer

The natural history of a patient's cancer is often characterised by genetic diversity and sequential sweeps of clonal dominance. It is therefore not surprising that identifying the most appropriate tumour-associated antigen for targeted intervention is challenging. The 5T4 oncofoetal antigen was identified by searching for surface molecules shared between human trophoblast and cancer cells with the rationale that they may function to allow survival of the foetus as a semi-allograft in the mother or a tumour in its host. The 5T4 protein is expressed by many different cancers but rarely in normal adult tissues. 5T4 molecules are 72 kD, heavily N-glycosylated proteins with several leucine-rich repeats which are often associated with protein-protein interactions. 5T4 expression is associated with the directional movement of cells through epithelial mesenchymal transition, potentiation of CXCL12/CXCR4 chemotaxis and inhibition of canonical Wnt/beta-catenin while favouring non-canonical pathway signalling; all processes which help drive the spread of cancer cells. The selective pattern of 5T4 tumour expression, association with a tumour-initiating phenotype plus a mechanistic involvement with cancer spread have underwritten the clinical development of different immunotherapeutic strategies including a vaccine, a tumour-targeted superantigen and an antibody drug conjugate. In addition, a chimeric antigen receptor T cell approach targeting 5T4 expressing tumour cells is in pre-clinical development. A key challenge will include how best to combine each 5T4 targeted immunotherapy with the most appropriate standard of care treatment (or adjunct therapy) to maximise the recovery of immune control and ultimately eliminate the tumour.

MVA vaccine encoding CMV antigens safely induces durable expansion of CMV-specific T cells in healthy adults

Attenuated poxvirus modified vaccinia Ankara (MVA) is a useful viral-based vaccine for clinical investigation, because of its excellent safety profile and property of inducing potent immune responses against recombinant (r) antigens. We developed Triplex by constructing an rMVA encoding 3 immunodominant cytomegalovirus (CMV) antigens, which stimulates a host antiviral response: UL83 (pp65), UL123 (IE1-exon4), and UL122 (IE2-exon5). We completed the first clinical evaluation of the Triplex vaccine in 24 healthy adults, with or without immunity to CMV and vaccinia virus (previous DryVax smallpox vaccination). Three escalating dose levels (DL) were administered IM in 8 subjects/DL, with an identical booster injection 28 days later and 1-year follow-up. Vaccinations at all DL were safe with no dose-limiting toxicities. No vaccine-related serious adverse events were documented. Local and systemic reactogenicity was transient and self-limiting. Robust, functional, and durable Triplex-driven expansions of CMV-specific T cells were detected by measuring T-cell surface levels of 4-1BB (CD137), binding to CMV-specific HLA multimers, and interferon-γ production. Marked and durable CMV-specific T-cell responses were also detected in Triplex-vaccinated CMV-seronegatives, and in DryVax-vaccinated subjects. Long-lived memory effector phenotype, associated with viral control during CMV primary infection, was predominantly found on the membrane of CMV-specific and functional T cells, whereas off-target vaccine responses activating memory T cells from the related herpesvirus Epstein-Barr virus remained undetectable. Combined safety and immunogenicity results of MVA in allogeneic hematopoietic stem cell transplant (HCT) recipients and Triplex in healthy adults motivated the initiation of a placebo-controlled multicenter trial of Triplex in HCT patients. This trial was registered at www.clinicaltrials.gov as #NCT02506933.

TroVax in colorectal cancer

Currently, the backbone of therapy for metastatic disease is cytotoxic chemotherapy, along with the recent addition of targeted therapy based on molecular markers with KRAS testing. Despite the improvement in survival for metastatic colon cancer, newer agents are still needed. The clinical activity of TroVax in metastatic colon cancer has been studied in a small number of clinical trials. There is evidence that supports the vaccine's ability to induce humoral and cellular responses, as demonstrated by positive 5T4 and MVA-specific antibody titers and cellular proliferation assays. Future strategies should focus on investigating the immunomodulatory effects of chemotherapy in conjunction with TroVax, understanding the optimal dosing and schedule of the combination, and examining potential predictive biomarkers to determine which patients may benefit from immunotherapy from those who do not.

Clinical outcomes model in renal cell cancer patients treated with modified vaccinia Ankara plus tumor-associated antigen 5T4

AIMS

We developed an outcomes model to select patients for renal cell cancer vaccine immunotherapy.

MATERIALS AND METHODS

We examined clinical data from 2 phase II studies of modified vaccinia Ankara as vector to express 5T4 (MVA-5T4), calculated progression-free survival (PFS) and overall survival (OS), and created risk groups based on the number of factors involved.

RESULTS

Median OS was 12.4 months; median PFS was 3.6 months. Significant factors (p<0.05) included neutrophils (both), bone metastases (OS), ECOG performance status (OS), lactate dehydrogenase levels (both), prior therapy with tyrosine kinase inhibitors plus immunotherapy (OS), Fuhrman grade (OS), and 5T4-specific ELISPOT response (PFS). By group, median OS was not reached in patients with favorable risk (censored at cutoff), was 13.7 months in those with intermediate risk and 4.0 months in those with poor risk.

CONCLUSIONS

Further validation of this model will identify the patients most likely to respond to MVA-5T4 and provide a framework for outcomes models for other vaccine therapies.

Recent advances in the use of therapeutic cancer vaccines in genitourinary malignancies

INTRODUCTION

Despite a recent increase in US FDA-approved treatments, genitourinary malignancies remain a source of significant morbidity and mortality. One focus of research is the use of therapeutic cancer vaccines in these diseases, and a significant body of clinical trial experience now exists for refining vaccine strategies to enhance antitumor efficacy and develop immune-based combination regimens.

AREAS COVERED

In recent years, clinical data from multiple trials in genitourinary malignancies have enhanced our understanding of the potential for immunotherapy in these cancers. There are also emerging clinical strategies that combine cancer vaccines with chemotherapy, radiation, androgen-deprivation therapy and immune checkpoint inhibitors. This review is based on a search of relevant literature for data presented over the past 5 years from clinical trials of cancer vaccines in prostate, bladder and renal carcinomas.

EXPERT OPINION

In the coming years, clinical trials informed by decades of preclinical data and emerging clinical data will help to define the role of immunotherapy in genitourinary malignancies. Combination strategies that capitalize on the immune properties of standard treatments will bring greater clinical benefits, and immune-based combinations will likely be moved to the neoadjuvant setting, where they may have optimal clinical impact.

Role of type I interferon in inducing a protective immune response: perspectives for clinical applications

Type I IFNs (IFN-I) are antiviral cytokines endowed with many biological effects, including antitumor activity. Over the last 15 years, an ensemble of studies has revealed that these cytokines play a crucial role in the induction of a protective antitumor immune response. Early in vivo studies in mouse models have been instrumental for understanding the IFN-I-induced host-mediated mechanisms. IFN-α is currently recognized as a powerful inducer of the differentiation/activation of dendritic cells (DCs) and today IFN-α-conditioned DCs represent promising DC candidates for the development of therapeutic cancer vaccines. Moreover, data from pilot clinical trials support the concept of using IFN-α as an enhancer of the response of patients to cancer vaccines. Notably, endogenous IFN-I production does also play a critical role in the antitumor response to some chemotherapeutic agents. Thus, we can now envisage new strategies of clinical use of IFN-α, based on the injection of IFN-conditioned cells as well as the usage of these cytokines as cancer vaccine adjuvants, alone or in combination with other treatments (including epigenetic drugs) to induce an immunogenic cell death and a long lasting antitumor response.

Identification of an HLA-A2-restricted epitope peptide derived from hypoxia-inducible protein 2 (HIG2)

We herein report the identification of an HLA-A2 supertype-restricted epitope peptide derived from hypoxia-inducible protein 2 (HIG2), which is known to be a diagnostic marker and a potential therapeutic target for renal cell carcinoma. Among several candidate peptides predicted by the HLA-binding prediction algorithm, HIG2-9-4 peptide (VLNLYLLGV) was able to effectively induce peptide-specific cytotoxic T lymphocytes (CTLs). The established HIG2-9-4 peptide-specific CTL clone produced interferon-γ (IFN-γ) in response to HIG2-9-4 peptide-pulsed HLA-A*02:01-positive cells, as well as to cells in which HLA-A*02:01 and HIG2 were exogenously introduced. Moreover, the HIG2-9-4 peptide-specific CTL clone exerted cytotoxic activity against HIG2-expressing HLA-A*02:01-positive renal cancer cells, thus suggesting that the HIG2-9-4 peptide is naturally presented on HLA-A*02:01 of HIG-2-expressing cancer cells and is recognized by CTLs. Furthermore, we found that the HIG2-9-4 peptide could also induce CTLs under HLA-A*02:06 restriction. Taken together, these findings indicate that the HIG2-9-4 peptide is a novel HLA-A2 supertype-restricted epitope peptide that could be useful for peptide-based immunotherapy against cancer cells with HIG2 expression.

Clinical applications of attenuated MVA poxvirus strain

The highly attenuated poxvirus strain modified vaccinia virus Ankara (MVA) has reached maturity as a vector delivery system and as a vaccine candidate against a broad spectrum of diseases. This has been largely recognized from research on virus-host cell interactions and immunological studies in pre-clinical and clinical trials. This review addresses the studies of MVA vectors used in phase I/II clinical trials, with the aim to provide the main findings obtained on their behavior when tested against relevant human diseases and cancer and also highlights the strategies currently implemented to improve the MVA immunogenicity. The authors assess that MVA vectors are progressing as strong vaccine candidates either alone or when administered in combination with other vectors.

Vaccination of castration-resistant prostate cancer patients with TroVax (MVA-5T4) in combination with docetaxel: a randomized phase II trial

The attenuated vaccinia virus, modified vaccinia Ankara, has been engineered to deliver the tumor antigen 5T4 (TroVax®). Here, we report results from a randomized open-label phase II trial in castration-resistant prostate cancer patients in which TroVax was administered in combination with docetaxel and compared against docetaxel alone. The aim was to recruit 80 patients (40 per arm), but the study was terminated early due to recruitment challenges. Therefore, this paper reports the comparative safety and immunological and clinical efficacy in 25 patients, 12 of whom were treated with TroVax plus docetaxel and 13 with docetaxel alone. 5T4-specific immune responses were monitored throughout the study. Clinical responses were assessed by measuring changes in tumor burden by CT and bone scan and by quantifying PSA concentrations. TroVax was well tolerated in all patients. Of 10 immunologically evaluable patients, 6 mounted 5T4-specific antibody responses. Patients treated with TroVax plus docetaxel showed a greater median progression-free survival of 9.67 months compared with 5.10 months for patients on the docetaxel alone arm (P = 0.097; HR = 0.31; 95% CI 0.08-1.24). Importantly, a pre-treatment biomarker previously demonstrated to predict 5T4 immune response and treatment benefit showed a strong association with 5T4 antibody response and a statistically significant association with progression-free survival in patients treated with TroVax plus docetaxel, but not docetaxel alone.

Identification of Pre- and Post-Treatment Markers, Clinical, and Laboratory Parameters Associated with Outcome in Renal Cancer Patients Treated with MVA-5T4

The recent approvals of immunotherapeutic agents (Sipuleucel-T and Ipilimumab) for the treatment of different solid tumors gave a boost to the growing cancer immunotherapy field, even though few immunotherapy studies have demonstrated convincingly that there is a direct link between the predicted mode of action of an immunological compound and therapeutic benefit. MVA-5T4 (TroVax^®) is a novel vaccine combining the tumor-associated antigen 5T4 to an engineered vector-modified vaccinia Ankara (MVA). MVA helps to express the oncofetal 5T4 antigen and subsequently trigger a tumor-directed immune reaction. The safety and clinical benefit reported in multiple phase I and II clinical trials using MVA-5T4 were encouraging; immune responses were induced in almost all treated patients, and associations between 5T4-specific cellular or humoral responses and clinical benefit were reported in most of the nine phase II trials. In particular, clinical studies conducted in renal cell carcinoma (RCC) patients have demonstrated an association between 5T4-specific (but not MVA) antibody responses and enhanced survival. This review describes the clinical studies using MVA-5T4 conducted in RCC that convincingly demonstrated that an antigen-specific immune response induced by vaccination is associated with enhanced patient survival and is not simply a function of the general “health” of patients. We will also provide our expert opinions on possible future better-designed clinical trials based on relevant biomarkers. In addition, various combinations of MVA-5T4 and different and newer immunomodulator agents with promising clinical benefit will be discussed.

Cancer vaccines: identification of biomarkers predictive of clinical efficacy

Personalized medicine is playing an increasingly important role in the treatment of patients living with cancer. This landmark shift has been driven in part by statistics emerging from the "one size fits all" approach to the treatment of cancer patients. Some reports suggest that only a minority of individuals actually benefit from treatment and adverse effects of medications remain a major cause of hospitalization, morbidities and deaths. Although the side-effect profile of most immunotherapy treatment modalities is usually fairly benign, there is no reason to believe that immunotherapy is any different from other oncology therapies in that some patients are likely to receive more benefit than others. Indeed, the fact that generation of the therapeutic modality requires translation through multiple complex biological processes for an immunotherapy product to be effective may mean that such approaches require an even better understanding of the patient being treated. Furthermore, the very low success rate of cancer immunotherapy approaches to deliver benefit to patients demands a more detailed understanding of who will benefit and why. The identification of biomarkers predictive of treatment benefit is one route to improve the success rate of cancer vaccines.

Role of vaccine therapy for renal cell carcinoma in the era of targeted therapy

Renal cell carcinoma is the most common malignant tumor originating from the kidney. Compared with other solid tumors, it does not respond to traditional management modalities, such as chemotherapy and radiotherapy. However, it is well known that renal cell carcinoma represents one of the most immune-responsive cancers and several immunotherapeutic strategies have been investigated in the management of renal cell carcinoma with variable degrees of success. The development of immunotherapy with α-interferon or high-dose interleukin-2 is the best established treatment, and is associated with durable disease control. Although the lack of defined antigens in renal cell carcinoma has hindered more specific vaccine development, research regarding vaccination therapy has been of special interest for the treatment of renal cell carcinoma for more than 30 years. At present, there are three types of cell-based vaccines in renal cell carcinoma treatment: autologous tumor-cell vaccines, genetically modified tumor vaccines and dendritic cell-based vaccines. A further type is peptide-based vaccination with tumor-associated antigens as possible targets, such as carbonic anhydrase IX, survivin and telomerase that are overexpressed in renal cell carcinoma. In the present article, we review data from completed clinical trials of vaccine therapy, and discuss future trials to assess the current knowledge and future role of vaccine therapy for renal cell carcinoma in the era of recently developed targeted therapy.

CD8+ T-cell clones specific for the 5T4 antigen target renal cell carcinoma tumor-initiating cells in a murine xenograft model

The tumor antigen 5T4 is frequently expressed at high levels on renal cell carcinoma (RCC) and other epithelial carcinomas. Surveys of normal tissues demonstrate abundant 5T4 expression on placental trophoblast cells with limited expression elsewhere. 5T4 is the target for a therapeutic cancer vaccine (MVA-5T4) that elicits 5T4-specific serological, proliferative, and cytotoxic T lymphocyte (CTL) responses. However, the antitumor activity of 5T4-specific CTL has not been extensively characterized. CD8 T cells from HLA-A2 healthy donors (n=4) or RCC patients (n=2) were stimulated in vitro with the HLA-A2-binding nonamer peptides 5T417-25 or 5T497-105 and screened by flow cytometry with specific tetramers (TET). CD8/TET T-cell clones specific for 5T417-25 or 5T497-105 peptide were isolated from 4/6 and 1/4 donors, respectively. A subset of clones specific for 5T417-25 was cytolytic for MVA-5T4-infected HLA-A2 EBV-transformed lymphoblastoid cell line target cells and for constitutively HLA-A2-expressing and 5T4-expressing RCC tumor cell lines (including A498 RCC). In a xenoengraftment assay, the coinoculation of a representative 5T417-25-specific CTL clone with A498 RCC tumors cells into immune-deficient mice completely prevented growth of A498 tumors. Taken together, these data demonstrate high-avidity CD8 CTL able to recognize the naturally processed 5T417-25 epitope on RCC tumor cells including putative tumor-initiating cells are present in peripheral blood of both healthy donors and RCC patients. CD8T-cell immunity targeting 5T417-25 is therefore of substantial interest both as a potential target for further development of vaccination or adoptive cellular immunotherapy and for immune monitoring studies in association with nonspecific immunotherapies.

Analysis of pre-treatment markers predictive of treatment benefit for the therapeutic cancer vaccine MVA-5T4 (TroVax)

Cancer vaccines such as MVA-5T4 (TroVax(®)) must induce an efficacious immune response to deliver therapeutic benefit. The identification of biomarkers that impact on the clinical and/or immunological efficacy of cancer vaccines is required in order to select patients who are most likely to benefit from this treatment modality. Here, we sought to identify a predictor of treatment benefit for renal cancer patients treated with MVA-5T4. Statistical modeling was undertaken using data from a phase III trial in which patients requiring first-line treatment for metastatic renal cell carcinoma were randomized 1:1 to receive MVA-5T4 or placebo alongside sunitinib, IL-2 or IFN-α. Numerous pre-treatment factors associated with inflammatory anemia (e.g., CRP, hemoglobin, hematocrit, IL-6, ferritin, platelets) demonstrated a significant relationship with tumor burden and patient survival. From these prognostic factors, the pre-treatment mean corpuscular hemoglobin concentration (MCHC) was found to be the best predictor of treatment benefit (P < 0.01) for MVA-5T4 treated patients and also correlated positively with tumor shrinkage (P < 0.001). Furthermore, MCHC levels showed a significant positive association with 5T4 antibody response (P = 0.01). The latter result was confirmed using an independent data set comprising phase II trials of MVA-5T4 in patients with colorectal, renal and prostate cancers. Retrospective analyses demonstrated that RCC patients who had very large tumor burdens and low MCHC levels received little or no benefit from treatment with MVA-5T4; however, patients with smaller tumor burdens and normal MCHC levels received substantial benefit from treatment with MVA-5T4.

Oncolysis of canine tumor cells by myxoma virus lacking the serp2 gene

OBJECTIVE

To determine the oncolytic efficacy of an attenuated form of myxoma virus lacking the serp2 gene in canine tumor cells.

SAMPLE

Primary cells were isolated from tumors that were surgically removed from dogs and from connective tissue obtained from the cadaver of a dog. Cells of various established cell lines from tumors and nontumorous tissues were obtained.

PROCEDURES

Experiments were performed with cells in monolayer culture. Cell cultures were inoculated with wild-type myxoma viruses or myxoma viruses lacking the serp2 gene, and measures of cytopathic effects, viral growth kinetics, and cell death and apoptosis were determined.

RESULTS

Myxoma viruses replicated in cells of many of the primary and established canine tumor cell lines. Canine tumor cells in which expression of activated protein kinase B was upregulated were more permissive to myxoma virus infection than were cells in which expression of activated protein kinase B was not upregulated. Myxoma viruses lacking the serp2 gene caused more cytopathic effects in canine tumor cells because of apoptosis than did wild-type myxoma viruses.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of the present study indicated myxoma viruses lacking the serp2 gene may be useful for treatment of cancer in dogs. Impact for Human Medicine-Results of the present study may be useful for development of novel oncolytic treatments for tumors in humans.

Recombinant viral vaccines for cancer

Cancer arises from 'self' in a series of steps that are all subject to immunoediting. Therefore, therapeutic cancer vaccines must stimulate an immune response against tumour antigens that have already evaded the body's immune defences. Vaccines presenting a tumour antigen in the context of obvious danger signals seem more likely to stimulate a response. This approach can be facilitated by genetic engineering using recombinant viral vectors expressing tumour antigens, cytokines, or both, from an immunogenic virus particle. We overview clinical attempts to use these agents for systemic immunisation and contrast the results with strategies employing direct intratumoural administration. We focus on the challenge of producing an effective response within the immune-suppressive tumour microenvironment, and discuss how the technology can overcome these obstacles.

SYT-SSX breakpoint peptide vaccines in patients with synovial sarcoma: a study from the Japanese Musculoskeletal Oncology Group

In the present study, we evaluated the safety and effectiveness of SYT-SSX-derived peptide vaccines in patients with advanced synovial sarcoma. A 9-mer peptide spanning the SYT-SSX fusion region (B peptide) and its HLA-A*2402 anchor substitute (K9I) were synthesized. In Protocols A1 and A2, vaccines with peptide alone were administered subcutaneously six times at 14-day intervals. The B peptide was used in Protocol A1, whereas the K9I peptide was used in Protocol A2. In Protocols B1 and B2, the peptide was mixed with incomplete Freund's adjuvant and then administered subcutaneously six times at 14-day intervals. In addition, interferon-α was injected subcutaneously on the same day and again 3 days after the vaccination. The B peptide and K9I peptide were used in Protocols B1 and B2, respectively. In total, 21 patients (12 men, nine women; mean age 43.6 years) were enrolled in the present study. Each patient had multiple metastatic lesions of the lung. Thirteen patients completed the six-injection vaccination schedule. One patient developed intracerebral hemorrhage after the second vaccination. Delayed-type hypersensitivity skin tests were negative in all patients. Nine patients showed a greater than twofold increase in the frequency of CTLs in tetramer analysis. Recognized disease progression occurred in all but one of the nine patients in Protocols A1 and A2. In contrast, half the 12 patients had stable disease during the vaccination period in Protocols B1 and B2. Of note, one patient showed transient shrinkage of a metastatic lesion. The response of the patients to the B protocols is encouraging and warrants further investigation.

Evaluation of MVA-5T4 as a novel immunotherapeutic vaccine in colorectal, renal and prostate cancer

This paper reviews the development of the combination of modified vaccinia Ankara (MVA) to deliver the tumor-associated antigen 5T4 as a novel immunotherapeutic vaccine. The oncofetal antigen 5T4 is highly expressed in 80% of breast, kidney, colorectal, prostate and ovarian carcinomas, making it an ideal antigen for vaccine therapy. To date, more than 3000 doses of MVA-5T4 have been administered to colorectal, renal and prostate cancer patients, with rare occurrences of grade 3 or 4 vaccination-related adverse events being observed. Studies have demonstrated that MVA-5T4 is safe and highly immunogenic, both as monotherapy and in combination with other standard of care therapies. Although an immune response has been observed, antitumor activity has been modest or absent in clinical trials. A Phase III trial resulted in the development of an immune response surrogate that is to be applied to all future MVA-5T4 clinical trials. With minimal side effects and the ability to produce a strong immunogenic response, MVA-5T4 is a viable addition to the cancer therapy arsenal.

Overexpression and potential targeting of the oncofoetal antigen 5T4 in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is resistant to conventional treatments. Novel, targeted treatments are hampered by the relative lack of MPM-associated tumour antigens. The aim of this study was to evaluate the level of expression and the relevance of 5T4 as a tumour-associated antigen in MPM. 5T4 expression was assessed by Western blotting, flow cytometry, immuno-cytochemistry and -histochemistry in 11 mesothelioma cell lines, 21 tumour biopsies, and ex vivo tumour cells obtained from the pleural fluid (PF) of 10 patients. 5T4 antibody levels were also determined in the plasma of patients and healthy donors. The susceptibility of MPM cells to 5T4-specific T-cell-mediated killing was determined using an HLA-A2(+), CD8(+) T-cell line, developed against the 5T4(17-25) peptide. We report here that cell surface 5T4 expression was detected in all mesothelioma cell lines and PF cell samples. Mesothelin and CD200, a suggested mesothelioma marker, were co-expressed with 5T4 on tumour cells in PF. Immunohistochemistry confirmed overexpression of 5T4, similar to mesothelin, on tumour cells but not on reactive stroma in all tissue sections tested. Median 5T4 antibody levels were 46% higher in patient than in healthy donor plasma, indicating immune recognition. Importantly, 5T4-specific CD8(+) T-cells were able to kill four out of six HLA-A2(+) MPM cell lines but not an HLA-A2(-) cell line, demonstrating immune recognition of MPM-associated 5T4 antigen at the effector T-cell level. We conclude that 5T4 is a potential new antigen for targeted therapies such as immunotherapy in MPM, as it is overexpressed on mesothelioma cells and recognised by 5T4-specific cytotoxic T-cells. Our findings have been translated into a Phase II clinical trial applying 5T4-targeted therapies in MPM patients.

Vaccines for colorectal cancer and renal cell carcinoma

Vaccines have shown promise for the prevention and treatment of solid tumors. Colorectal cancer and renal cell carcinoma are common malignancies that may be amenable to vaccine strategies. This review summarizes target antigens in colorectal and renal cell carcinoma, discusses some of the vaccine approaches in development, and details the results of pivotal phase III trials evaluating therapeutic vaccines in patients with advanced colorectal and renal cell carcinoma. Finally, some of the challenges with vaccine development for colorectal and renal cell carcinoma are described.

Viral vector-based therapeutic cancer vaccines

Most viruses are naturally immunogenic and can be engineered to express tumor antigen transgenes. Moreover, many types of recombinant viruses have been shown to infect professional antigen-presenting cells, specifically dendritic cells, and express their transgenes. This enhanced presentation of tumor antigens to the immune system has led to an increase in the frequency and avidity of cytotoxic T lymphocytes that target tumor cells expressing the tumor antigen(s) encoded in the vaccine vector. Logistically, recombinant viruses can be produced, administered, and quality controlled more easily compared with other immunotherapy strategies. The intrinsic properties of each virus have distinct advantages and disadvantages, which can determine their applicability in a particular therapeutic setting. The disadvantage of some vectors is the development of host-induced neutralizing antibodies to the vector itself, thus limiting its continued use. The "off-the-shelf" nature of viral vaccine platforms renders them exceptionally suitable for multicenter randomized trials. This review described and discussed the strategies used and results using viral-based vaccines, with emphasis on phases II and III clinical trials. Future directions will involve the evaluation of viral-based vaccines in the adjuvant and neoadjuvant settings, in patients with low burden metastatic disease, and in combination with other forms of therapy including immunotherapy.

TroVax® vaccine therapy for renal cell carcinoma

Renal cell carcinoma (RCC) is the most common primary malignancy affecting the kidney. In the past decade, several well-designed clinical trials have shifted the treatment paradigm for RCC to favor targeted therapies as first-line agents. Recognition of the immunogenic nature of RCC has also resulted in the development of immunotherapy approaches with high-dose IL-2 treatment being the best established and associated with durable disease control. The lack of defined antigens in RCC has hindered more specific vaccine development. TroVax® is a novel vaccine based on a modified vaccinia virus Ankara vector engineered to express the 5T4 tumor-associated antigen, found on over 95% of clear cell and papillary RCC tumors. The safety and efficacy of TroVax has been evaluated in several Phase I/II clinical trials and in a multicenter Phase III trial. This article will discuss the clinical background of RCC, the rationale for TroVax development, results of several TroVax clinical trials and future directions for optimizing TroVax therapy in patients with RCC and other cancers.

Immunotherapy for renal cell carcinoma

Although several cytokines have shown antitumor activity in renal cell carcinoma (RCC), the most consistent results have been reported with interleukin-2 (IL-2) and interferon (IFN). Recent insights into how the immune response to a tumor is regulated hold the promise of allowing patients to obtain a durable response to immunotherapy, perhaps without the significant toxicity associated with conventional approaches. This review describes how improvements in patient selection, combination therapy, and investigational agents might expand and better define the role of immunotherapy in metastatic RCC.

Role of immunotherapy for renal cell cancer in 2011

High-dose interleukin-2 (IL-2) and interferon were the most commonly administered therapies before the recent introduction of targeted agents, including vascular endothelial growth factor and mammalian target of rapamycin pathway inhibitors. Although the new agents result in a progression-free survival benefit, high-dose IL-2 remains the only agent with proven efficacy in producing durable complete and partial responses in patients with metastatic renal cell carcinoma (RCC). Furthermore, although the use of single-agent interferon has decreased significantly since the introduction of targeted therapy, it remains in the frontline setting in combination with bevacizumab as a result of 2 large phase III trials. Lastly, improved understanding of immune regulation has led to the advancement of targeted immunotherapy using immune checkpoint inhibitors that have shown promising activity and are moving forward in clinical development. This article focuses on the current status of immunotherapy in the management of metastatic RCC.

Tumor immunotherapy using adenovirus vaccines in combination with intratumoral doses of CpG ODN

The combination of viral vaccination with intratumoral (IT) administration of CpG ODNs is yet to be investigated as an immunotherapeutic treatment for solid tumors. Here, we show that such a treatment regime can benefit survival of tumor-challenged mice. C57BL/6 mice bearing ovalbumin (OVA)-expressing EG.7 thymoma tumors were therapeutically vaccinated with adenovirus type 5 encoding OVA (Ad5-OVA), and the tumors subsequently injected with the immunostimulatory TLR9 agonist, CpG-B ODN 1826 (CpG), 4, 7, 10, and 13 days later. This therapeutic combination resulted in enhanced mean survival times that were more than 3.5× longer than naïve mice, and greater than 40% of mice were cured and capable of resisting subsequent tumor challenge. This suggests that an adaptive immune response was generated. Both Ad5-OVA and Ad5-OVA + CpG IT treatments led to significantly increased levels of H-2 K(b)-OVA-specific CD8+ lymphocytes in the peripheral blood and intratumorally. Lymphocyte depletion studies performed in vivo implicated both NK cells and CD8+ lymphocytes as co-contributors to the therapeutic effect. Analysis of tumor infiltrating lymphocytes (TILs) on day 12 post-tumor challenge revealed that mice treated with Ad5-OVA + CpG IT possessed a significantly reduced percentage of regulatory T lymphocytes (Tregs) within the CD4+ lymphocyte population, compared with TILs isolated from mice treated with Ad5-OVA only. In addition, the proportion of CD8+ TILs that were OVA-specific was reproducibly higher in the mice treated with Ad5-OVA + CpG IT compared with other treatment groups. These findings highlight the therapeutic potential of combining intratumoral CpG and vaccination with virus encoding tumor antigen.

Viral delivery for gene therapy against cell movement in cancer

Viral delivery for cancer gene therapy is a promising approach, where traditional radiotherapy or chemotherapy to limit proliferation and movement of cancer cells has met resistance. Based on the new understanding of the biology of the viral vectors, therapeutic viral vectors for cancer gene therapy have been improved for greater safety and efficacy as well as transitioned from being non-replicating to replication-competent. Traditional oncolytic vectors have focused on eliminating tumor growth, while novel vectors simultaneously target epithelial-to-mesenchymal transition (EMT) in cancer cells, which could further prevent and reverse the aggressive tumor progression. In this review, we highlight the illustrative examples of cancer gene therapy in clinical trials as well as preclinical data and include proposals on methods to further enhance the safety and efficacy of oncolytic viral vectors in cancer gene therapy.

Therapeutic vaccines in renal cell carcinoma

Metastatic renal cell carcinoma (mRCC) is a lethal disease. The advent of tyrosine kinase inhibitors (TKIs) has changed the disease process, yet the majority of patients will develop treatment-resistant disease. IL-2 based immunotherapy in mRCC is the only US FDA-approved treatment with curative results. Immunotherapeutic vaccine approaches to mRCC have been under investigation for several decades with mixed results. The recent FDA-approval of the first cellular immunotherapy in prostate cancer (Provenge(®)) has reinvigorated the search for similar vaccines approaches in mRCC. This review introduces the concepts and different features required for a successful anticancer vaccine approach.

MVA-5T4-induced immune responses are an early marker of efficacy in renal cancer patients

Few immunotherapy compounds have demonstrated a direct link between the predicted mode of action of the product and benefit to the patient. Since cancer vaccines are thought to have a delayed therapeutic effect, identification of the active moiety may enable the development of an early marker of efficacy. Patients with renal cancer and requiring first-line treatment for metastatic disease were randomized 1:1 to receive MVA-5T4 (TroVax(®)) or placebo alongside Sunitinib, IL-2 or IFN-α in a multicentre phase III trial. Antibody responses were quantified following the 3rd and 4th vaccinations. A surrogate for 5T4 antibody response (the immune response surrogate; IRS) was constructed and then used in a survival analysis to evaluate treatment benefit. Seven hundred and thirty-three patients were randomized, and immune responses were assessed in 590 patients. A high 5T4 antibody response was associated with longer survival within the MVA-5T4-treated group. The IRS was constructed as a linear combination of pre-treatment 5T4 antibody levels, hemoglobin and hematocrit and was shown to be a significant predictor of treatment benefit in the phase III study. Importantly, the IRS was also associated with antibody response and survival in an independent dataset comprising renal, colorectal and prostate cancer patients treated with MVA-5T4 in phase I-II studies. The derivation of the IRS formed part of an exploratory, retrospective analysis; however, if confirmed in future studies, the results have important implications for the development and use of the MVA-5T4 vaccine and potentially for other similar vaccines.

A novel candidate HIV vaccine vector based on the replication deficient Capripoxvirus, Lumpy skin disease virus (LSDV)

BACKGROUND

The Capripoxvirus, Lumpy skin disease virus (LSDV) has a restricted host-range and is being investigated as a novel HIV-1 vaccine vector. LSDV does not complete its replication cycle in non-ruminant hosts.

METHODS

The safety of LSDV was tested at doses of 104 and 106 plaque forming units in two strains of immunocompromised mice, namely RAG mice and CD4 T cell knockout mice. LSDV expressing HIV-1 subtype C Gag, reverse transcriptase (RT), Tat and Nef as a polyprotein (Grttn), (rLSDV-grttn), was constructed. The immunogenicity of rLSDV-grttn was tested in homologous prime-boost regimens as well as heterologous prime-boost regimes in combination with a DNA vaccine (pVRC-grttn) or modified vaccinia Ankara vaccine (rMVA-grttn) both expressing Grttn.

RESULTS

Safety was demonstrated in two strains of immunocompromised mice.In the immunogenicity experiments mice developed high magnitudes of HIV-specific cells producing IFN-gamma and IL-2. A comparison of rLSDV-grttn and rMVA-grttn to boost a DNA vaccine (pVRC-grttn) indicated a DNA prime and rLSDV-grttn boost induced a 2 fold (p < 0.01) lower cumulative frequency of Gag- and RT-specific IFN-γ CD8 and CD4 cells than a boost with rMVA-grttn. However, the HIV-specific cells induced by the DNA vaccine prime rLSDV-grttn boost produced greater than 3 fold (p < 0.01) more IFN- gamma than the HIV-specific cells induced by the DNA vaccine prime rMVA-grttn boost. A boost of HIV-specific CD4 cells producing IL-2 was only achieved with the DNA vaccine prime and rLSDV-grttn boost. Heterologous prime-boost combinations of rLSDV-grttn and rMVA-grttn induced similar cumulative frequencies of IFN- gamma producing Gag- and RT-specific CD8 and CD4 cells. A significant difference (p < 0.01) between the regimens was the higher capacity (2.1 fold) of Gag-and RT-specific CD4 cells to produce IFN-γ with a rMVA-grttn prime - rLSDV-grttn boost. This regimen also induced a 1.5 fold higher (p < 0.05) frequency of Gag- and RT-specific CD4 cells producing IL-2.

CONCLUSIONS

LSDV was demonstrated to be non-pathogenic in immunocompromised mice. The rLSDV-grttn vaccine was immunogenic in mice particularly in prime-boost regimens. The data suggests that this novel vaccine may be useful for enhancing, in particular, HIV-specific CD4 IFN- gamma and IL-2 responses induced by a priming vaccine.

An update on TroVax for the treatment of progressive castration-resistant prostate cancer

Prostate cancer is a common human malignancy with few effective therapeutic options for treating advanced castration-resistant disease. The potential therapeutic effectiveness of immunotherapy and vaccines, in particular, has gained popularity based on the identification of prostate-associated antigens, potent expression vectors for vaccination, and data from recent clinical trials. A modified vaccinia Ankara (MVA) virus expressing 5T4, a tumor-associated glycoprotein, has shown promise in preclinical studies and clinical trials in patients with colorectal and renal cell carcinoma. This review will discuss the rationale for immunotherapy in prostate cancer and describe preclinical and limited clinical data in prostate cancer for the MVA-5T4 (TroVax^®) vaccine.

Immunotherapy for treating metastatic colorectal cancer

BACKGROUND

Colorectal cancer remains one of the leading causes of death in the world. Surgery still remains the mainstay of treatment for primary and metastatic colorectal cancer. Immunotherapy used as an adjunct to surgery can play an important role in controlling the spread of tumour.

METHODS

The online databases PubMed, Medline, Scirus and Medscape Oncology were used to identify articles of relevance. Keywords included; "Immunotherapy", "Cellular Immunotherapy", "Metastatic Colorectal Cancer", "Monoclonal Antibody" "Tumour Vaccines" and "Adoptive Cell Therapy". The databases search was from the period of June 1995 until May 2010 inclusive.

RESULTS

Our understanding of tumour immunology has allowed the development of some successful therapies. Immunotherapy through the use of monoclonal antibodies is an effective adjunct to chemotherapy for metastatic colorectal cancer. Other modalities that are in the stages of development are cellular and conjugated vaccines. However, these vaccines are being experimented in advanced stages of colorectal tumours.

CONCLUSION

Colorectal cancer vaccines are being developed for advanced stages of colorectal tumour. However, their use as an early adjunct could potentially limit the spread of tumour or even result in cure. Further trials are required to ensure the safety and efficacy of cellular vaccines against colorectal tumours to allow their use on patients early in their disease presentation.

Therapeutic cancer vaccines: are we there yet?

Enthusiasm for therapeutic cancer vaccines has been rejuvenated with the recent completion of several large, randomized phase III clinical trials that in some cases have reported an improvement in progression free or overall survival. However, an honest appraisal of their efficacy reveals modest clinical benefit and a frequent requirement for patients with relatively indolent cancers and minimal or no measurable disease. Experience with adoptive cell transfer-based immunotherapies unequivocally establishes that T cells can mediate durable complete responses, even in the setting of advanced metastatic disease. Further, these findings reveal that the successful vaccines of the future must confront: (i) a corrupted tumor microenvironment containing regulatory T cells and aberrantly matured myeloid cells, (ii) a tumor-specific T-cell repertoire that is prone to immunologic exhaustion and senescence, and (iii) highly mutable tumor targets capable of antigen loss and immune evasion. Future progress may come from innovations in the development of selective preparative regimens that eliminate or neutralize suppressive cellular populations, more effective immunologic adjuvants, and further refinement of agents capable of antagonizing immune check-point blockade pathways.

Vaccination of metastatic renal cancer patients with MVA-5T4: a randomized, double-blind, placebo-controlled phase III study

PURPOSE

The TroVax Renal Immunotherapy Survival Trial was a randomized, placebo-controlled phase III study that investigated whether modified vaccinia Ankara encoding the tumor antigen 5T4 (MVA-5T4) prolonged survival of patients receiving first-line standard-of-care (SOC) treatment for metastatic renal cell cancer.

EXPERIMENTAL DESIGN

Patients with metastatic clear cell renal cancer, prior nephrectomy, and good or intermediate prognosis were randomized 1:1 to receive up to 13 immunizations of MVA-5T4/placebo in combination with either sunitinib, interleukin-2 or interferon-α. The primary end point was overall survival. Secondary end points included progression-free survival, overall response rate, and safety.

RESULTS

Seven hundred thirty-three patients were recruited (365 MVA-5T4 and 368 placebo). Treatment arms were well balanced for SOC and prognosis. No significant difference in the incidence of adverse events or serious adverse events was observed. No significant difference in overall survival was evident in the two treatment arms (median 20.1 months MVA-5T4 versus 19.2 months placebo; P = 0.55). The magnitude of the 5T4-specific antibody response induced by vaccination with MVA-5T4 was associated with enhanced patient survival. Furthermore, exploratory analyses suggested a number of pretreatment hematologic factors that could identify patients who derive significant benefit from this vaccine.

CONCLUSION

MVA-5T4 in combination with SOC was well tolerated, but no difference in survival was observed in the overall study population. Exploratory analyses indicate that there may be subsets of patients who could gain significant benefit from MVA-5T4, but such results would need to be confirmed in future randomized clinical studies.

Update on vaccine development for renal cell cancer

Renal cell carcinoma (RCC) remains a significant health concern that frequently presents as metastatic disease at the time of initial diagnosis. Current first-line therapeutics for the advanced-stage RCC include antiangiogenic drugs that have yielded high rates of objective clinical response; however, these tend to be transient in nature, with many patients becoming refractory to chronic treatment with these agents. Adjuvant immunotherapies remain viable candidates to sustain disease-free and overall patient survival. In particular, vaccines designed to optimize the activation, maintenance, and recruitment of specific immunity within or into the tumor site continue to evolve. Based on the integration of increasingly refined immunomonitoring systems in both translational models and clinical trials, allowing for the improved understanding of treatment mechanism(s) of action, further refined (combinational) vaccine protocols are currently being developed and evaluated. This review provides a brief history of RCC vaccine development, discusses the successes and limitations in such approaches, and provides a rationale for developing combinational vaccine approaches that may provide improved clinical benefits to patients with RCC.