Immune evasion mechanisms in colorectal cancer liver metastasis patients vaccinated with TroVax (MVA-5T4)

Adoptive therapy with CAR redirected T cells: the challenges in targeting solid tumors

Recent spectacular success in the adoptive cell therapy of leukemia and lymphoma with chimeric antigen receptor (CAR)-modified T cells raised the expectations that this therapy may be efficacious in a wide range of cancer entities. The expectations are based on the predefined specificity of CAR T cells by an antibody-derived binding domain that acts independently of the natural T-cell receptor, recognizes targets independently of presentation by the major histocompatibility complex and allows targeting toward virtually any cell surface antigen. We here discuss that targeting CAR T cells toward solid tumors faces certain circumstances critical for the therapeutic success. Targeting tumor stroma and taking advantage of TRUCK cells, in other words, CAR T cells with inducible release of a transgenic payload, are some strategies envisaged to overcome current limitations in the near future.

Cancer Research UK Centre for Drug Development: translating 21st-century science into the cancer medicines of tomorrow

The Cancer Research UK Centre (CRUK) for Drug Development (CDD) can trace its origins back to the Cancer Research Campaign Phase I/II Committee (created in 1980) and to date has tested over 120 potential cancer medicines in early-phase clinical trials. Five drugs are now registered, providing benefit to thousands of patients with cancer as part of their routine standard of care. In recent years, the CDD has established several different business and operating models that provide it with access to the pipelines of pharmaceutical and biotechnology companies. This has enabled potential new treatments to be taken into clinical development that might have otherwise languished on companies' shelves and has increased the number of drug combinations being explored in early-phase clinical trials.

Understanding and exploiting 5T4 oncofoetal glycoprotein expression

Oncofoetal antigens are present during foetal development with generally limited expression in the adult but are upregulated in cancer. These molecules can sometimes be used to diagnose or follow treatment of tumours or as a target for different immunotherapies. The 5T4 oncofoetal glycoprotein was identified by searching for shared surface molecules of 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, potentially influencing growth, invasion or altered immune surveillance of the host. 5T4 tumour selective expression has stimulated the development of 5T4 vaccine, 5T4 antibody targeted-superantigen and 5T4 antibody-drug therapies through preclinical and into clinical studies. It is now apparent that 5T4 expression is a marker of the use (or not) of several cellular pathways relevant to tumour growth and spread. Thus 5T4 expression is mechanistically associated with the directional movement of cells through epithelial mesenchymal transition, facilitation of CXCL12/CXCR4 chemotaxis, blocking of canonical Wnt/beta-catenin while favouring non-canonical pathway signalling. These processes are highly regulated in development and in normal adult tissues but can contribute to the spread of cancer cells. Understanding the differential impact of these pathways marked by 5T4 can potentially improve existing, or aid development of novel cancer treatment strategies.

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.

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.

CAR-T cells and solid tumors: tuning T cells to challenge an inveterate foe

Recent reports on the impressive efficacy of adoptively transferred T cells to challenge cancer in early phase clinical trials have significantly raised the profile of T cell therapy. Concomitantly, general expectations are also raised by these reports, with the natural aspiration to deliver this therapy over a wide range of tumor indications. Chimeric antigen receptors (CARs) endow T cell populations with defined antigen specificities that function independently of the natural T cell receptor and permit targeting of T cells towards virtually any tumor. Here, we review the current clinical application of CAR-T cells and relate clinical efficacy and safety of CAR-T cell trials to parameters considered critical for CAR engineering, classified as the three T's of CAR-T cell manipulation.

The role of classical and non-classical HLA class I antigens in human tumors

In human tumors alterations in the surface expression and/or function of the major histocompatibility complex (MHC) class I antigens are frequently found and equip neoplastic cells with mechanisms to escape immune control. The aberrant expression of HLA class I molecules can be caused by structural alterations or dysregulations of genes encoding the classical HLA class I antigens and/or components of the HLA class I antigen processing machinery (APM). The dysregulation of APM components could occur at the epigenetic, transcriptional or post-transcriptional level. In some malignancies these abnormalities are significantly associated with a higher tumor staging, grading, disease progression and a reduced survival of patients as well as a failure to CD8(+) T cell-based immunotherapies. In addition to HLA class I abnormalities, expression of the non-classical HLA-G antigen is often induced in tumors, which could be mediated by various microenvironmental factors. Interestingly, soluble HLA-G serum and plasma levels have been useful markers for the prediction of some malignancies. The biological consequence of HLA-G expression or sHLA-G is an escape from T and NK cell-mediated recognition. Thus, alterations of non-classical and classical HLA class I antigens and components of the antigen processing pathway provide tumor cells with different mechanisms to inactivate immune responses resulting in tumor growth and evasion from host immune surveillance.

T-cell-inducing vaccines - what's the future

In the twentieth century vaccine development has moved from the use of attenuated or killed micro-organisms to protein sub-unit vaccines, with vaccine immunogenicity assessed by measuring antibodies induced by vaccination. However, for many infectious diseases T cells are an important part of naturally acquired protective immune responses, and inducing these by vaccination has been the aim of much research. The progress that has been made in developing effective T-cell-inducing vaccines against viral and parasitic diseases such as HIV and malaria is discussed, along with recent developments in therapeutic vaccine development for chronic viral infections and cancer. Although many ways of inducing T cells by vaccination have been assessed, the majority result in low level, non-protective responses. Sufficient clinical research has now been conducted to establish that replication-deficient viral vectored vaccines lead the field in inducing strong and broad responses, and efficacy studies of T-cell-inducing vaccines against a number of diseases are finally demonstrating that this is a valid approach to filling the gaps in our defence against not only infectious disease, but some forms of cancer.

Innate immune recognition of poxviral vaccine vectors

The study of poxviruses pioneered the field of vaccinology after Jenner's remarkable discovery that 'vaccination' with the phylogenetically related cowpox virus conferred immunity to the devastating disease of smallpox. The study of poxviruses continues to enrich the field of virology because the global eradication of smallpox provides a unique example of the potency of effective immunization. Other poxviruses have since been developed as vaccine vectors for clinical and veterinary applications and include modified vaccinia virus strains such as modified vaccinia Ankara and NYVAC as well as the avipox viruses, fowlpox virus and canarypox virus. Despite the empirical development of poxvirus-based vectored vaccines, it is only now becoming apparent that we need to better understand how the innate arm of the immune system drives adaptive immunity to poxviruses, and how this information is relevant to vaccine design strategies, which are the topics addressed in this article.

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.

Colorectal cancer vaccines in clinical trials

This article elucidates current strategies of active immunotherapy for colorectal cancer patients with a focus on T-cell mediated immunotherapy. Poor prognosis of especially stage III and IV colorectal cancer patients emphasizes the need for advanced therapeutic intervention. Here, we refer to clinical trials using either tumor cell-derived vaccines or tumor antigen vaccines with a special interest on safety, induced immune responses, clinical benefit and efforts to improve the clinical impact of these vaccines in the context of colorectal cancer treatment.

Bacterial heat-stable enterotoxins: translation of pathogenic peptides into novel targeted diagnostics and therapeutics

Heat-stable toxins (STs) produced by enterotoxigenic bacteria cause endemic and traveler’s diarrhea by binding to and activating the intestinal receptor guanylyl cyclase C (GC-C). Advances in understanding the biology of GC-C have extended ST from a diarrheagenic peptide to a novel therapeutic agent. Here, we summarize the physiological and pathophysiological role of GC-C in fluid-electrolyte regulation and intestinal crypt-villus homeostasis, as well as describe translational opportunities offered by STs, reflecting the unique characteristics of GC-C, in treating irritable bowel syndrome and chronic constipation, and in preventing and treating colorectal cancer.

Targeting localized immune suppression within the tumor through repeat cycles of immune cell-oncolytic virus combination therapy

A major limitation to the use of immunotherapy in the treatment of cancer has been the localized immune suppressive environment within the tumor. Although there is evidence that tumor-selective (oncolytic) viruses may help to overcome this immune suppression, a primary limitation to their use has been limited systemic delivery potential, especially in the face of antiviral immunity. We recently demonstrated that tumor-trafficking immune cells can efficiently deliver oncolytic viral therapies to their tumor targets. These cells act as both a therapeutic agent and also a carrier vehicle for the oncolytic virus. Here, we demonstrate that such delivery is also possible in the face of pre-existing antiviral immunity, so overcoming the limited systemic delivery of naked, cell-free virus. It was also found that treatment of previously immunized mice or repeat treatments leading to immunization resulted in a switch from a primarily oncolytic to an immunotherapeutic mechanism of action. Furthermore, repeat cycles of treatment with combination immune cell-viral therapy resulted in increased tumor infiltration of effector T-cells and a general reduction in the levels of known immune suppressive lymphocyte populations. This therefore represents a novel and effective means to overcome localized immune suppression within the tumor microenvironment.

In vivo delivery of antigens by adenovirus dodecahedron induces cellular and humoral immune responses to elicit antitumor immunity

Cancer vaccines based on virus-like particles (VLPs) vectors may offer many advantages over other antigen-delivery systems and represent an alternative to the ex vivo cell therapy approach. In this study, we describe the use of penton-dodecahedron (Pt-Dd) VLPs from human adenovirus type 3 (Ad3) as cancer vaccine vehicle for specific antigens, based on its unique cellular internalization properties. WW domains from the ubiquitin ligase Nedd4 serve as an adapter to bind the antigen to Pt-Dd. By engineering fusion partners of WW with the model antigen ovalbumin (OVA), Pt-Dd can efficiently deliver WW-OVA in vitro and the Pt-Dd/WW complex can be readily internalized by dendritic cells (DCs). Immunization with WW-OVA/Pt-Dd results in 90% protection against B16-OVA melanoma implantation in syngeneic mice. This high level of protection correlates with the development of OVA-specific CD8(+) T cells. Moreover, vaccination with WW-OVA Pt-Dd induces robust humoral responses in mice as shown by the high levels of anti-OVA antibodies (Abs) detected in serum. Importantly, treatment of mice bearing B16-OVA tumors with WW-OVA/Pt-Dd results in complete tumor regression in 100% of cases. Thus, our data supports a dual role of Pt-Dd as antigen-delivery vector and natural adjuvant, able to generate integrated cellular and humoral responses of broad immunogenic complexity to elicit specific antitumor immunity. Antigen delivery by Pt-Dd vector is a promising novel strategy for development of cancer vaccines with important clinical applications.

Modulation of lymphocyte regulation for cancer therapy: a phase II trial of tremelimumab in advanced gastric and esophageal adenocarcinoma

PURPOSE

Cytotoxic T lymphocyte antigen 4 (CTLA4), a key negative regulator of T-cell activation, is targeted by the antibody tremelimumab to release potentially useful antitumor activity.

EXPERIMENTAL DESIGN

This phase II trial investigated tremelimumab as a second-line treatment for patients with metastatic gastric and esophageal adenocarcinomas. Tremelimumab was given every 3 months until symptomatic disease progression. Safety, clinical efficacy, and immunologic activity were evaluated.

RESULTS

Eighteen patients received tremelimumab. Most drug-related toxicity was mild; however, there was a single death due to bowel perforation that complicated colitis. Four patients had stable disease with clinical benefit; one patient achieved a partial response after eight cycles (25.4 months) and remains well on study at 32.7 months. Markers of regulatory phenotype, forkhead box protein 3 and CTLA4, doubled transiently in CD4(+)CD25(high) lymphocytes in the first month after tremelimumab before returning to baseline. In contrast, CTLA4 increased in CD4(+)CD25(low/negative) lymphocytes throughout the cycle of treatment. De novo proliferative responses to tumor-associated antigens 5T4 (8 of 18 patients) and carcinoembryonic antigen (5 of 13) were detected. Patients with a posttreatment carcinoembryonic antigen proliferative response had median survival of 17.1 months compared with 4.7 months for nonresponders (P = 0.004). Baseline interleukin-2 release after T-cell activation was higher in patients with clinical benefit and toxicity.

CONCLUSION

Despite the disappointing response rate of tremelimumab, one patient had a remarkably durable benefit for this poor-prognosis disease. In vitro evidence of enhanced proliferative responses to relevant tumor-associated antigens suggests that combining CTLA4 blockade with antigen-targeted therapy may warrant further investigation.