The immunological era in melanoma treatment: new challenges for heat shock protein-based vaccine in the advanced disease

INTRODUCTION: Tumor-derived heat shock protein (HSP)-peptide complexes (HSPPCs) induced immunity against malignancies in preclinical trials, working across tumor types and bypassing the need to identify single immunogenic peptides. These results paved the way for the use of human gp96 obtained from autologous tumor samples as an anti-cancer vaccine. AREAS COVERED: Autologous tumor-derived HSP gp96 peptide complex (HSPPC-96) vaccine is emerging as a tumor- and patient-specific cancer vaccine, with confirmed activity in several malignancies. It has been tested in Phase III clinical trials in advanced melanoma and kidney cancer with evidence for efficacy in patients with earlier stage disease. HSPPC-96-based vaccine demonstrated an excellent safety profile, thus emerging as a novel therapeutic approach with a suggestive role in cancer therapy. This review summarizes work on the use of HSPPC-96 as an autologous anti-tumor vaccine in advanced melanoma. Data were retrieved by PubMed and Medline research and using the authors' personal experience. EXPERT OPINION: Further investigations are needed to understand the biological basis of immune functions in order to improve the clinical outcome of HSP-based cancer therapy. In the near future, the combination of HSP-based vaccines with other biological compounds might represent a successful strategy in the therapy of advanced melanoma.     

HSPPC-96: a personalised cancer vaccine

HSPPC-96 is a protein peptide complex consisting of a 96 kDa heat shock protein (Hsp), gp96, and an array of gp96-associated cellular peptides. Immunisation with HSPPC-96 induces T-cell specific immunity against these peptides; gp96 is not immunogenic per se. The non-covalent binding of gp96 to peptides is neither selective nor restricted to cell types. Thus, the collection of gp96-associated peptides represents the antigenic peptide pool of a cell; this is the basis of the peptide-specific immunogenicity elicited by HSPPC-96. Since the repertoire of antigenic peptides in the cell is different between normal and tumour cells and is also distinct among tumours of the same histology due to the randomness of tumour-specific mutations, a purified sample of HSPPC-96 can only effectively immunise against the tumour from which it originates. The immunisation effect is, therefore, specific to both the individual patient and the tumour type. This true custom-based vaccine has been shown to induce protective T-cell immunity against a variety of tumours in animal models. The major mechanism of action is thought to be the ability of HSPPC-96 to prime peptide-specific MHC class I-restricted CD8⁺ T-cells by interacting with antigen-presenting cells in a receptor-dependent manner. HSPPC-96 is now being widely tested against human malignancies for which effective therapies do not exist. The major challenges of the human studies are immunological monitoring and the determination of optimal dosing, scheduling and route of administration. HSPPC-96 has been well tolerated at all dose levels. Clinical applications are being addressed by numerous studies including an international, multi-centre, double-blind Phase III trial for the treatment of stage III renal cell carcinoma in the adjuvant setting.     

Heat-shock proteins-based immunotherapy for advanced melanoma in the era of target therapies and immunomodulating agents

Introduction: Heat-shock proteins (HSPs) are highly conserved, stress-induced proteins that function as chaperones, stabilizing proteins and delivering peptides. Tumor-derived HSP peptide complexes (HSPPCs) induced immunity against several malignancies in preclinical models, exhibiting activity across tumor types.

Areas covered: HSPPC-based vaccination showed clinical activity in subsets of patients with different malignancies (e.g., gastric, colorectal, pancreatic, ovarian cancer, and glioblastoma). In Phase III clinical trials for advanced melanoma and renal cell carcinoma patients, HSPPC-based vaccine demonstrated an excellent safety profile, thus emerging as a flexible tumor- and patient-specific therapeutic approach.

Expert opinion: Melanoma, renal clear cell carcinoma, and glioblastoma are among suitable targets for HSP-based treatment as demonstrated by immune responses and clinical activity observed in subsets of patients, mainly those with early stage of disease and limited tumor burden. In order to further improve clinical activity, combinations of HSPPC-based vaccines with mutation-driven therapies, antiangiogenic agents, or immunomodulating monoclonal antibodies should be tested in controlled clinical trials.     

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.     

Recent advances in immunotherapy for the treatment of prostate cancer

Introduction: Prostate cancer vaccines attempt to induce cancer-specific systemic immune responses and represent a new class of targeted therapies, many of which are non-toxic. Several vaccine technologies are in development.

Areas covered: An autologous antigen presenting cell vaccine loaded with prostate acid phosphatase conjugated with GM-CSF, sipuleucel-T confers a survival advantage in men with metastatic castration-resistant prostate cancer (CRPC) and is now FDA approved based on the IMPACT trial. A poxvirus-based vaccine, PROSTVAC-VF TRICOM targeting prostate-specific antigen (PSA), has demonstrated improved survival in a randomized Phase II trial of patients with metastatic CRPC. Novel T lymphocyte checkpoint inhibitors of cytotoxic T lymphocyte antigen 4 and programmed death-1 are also emerging. Recognition of improved survival without an earlier clinical signal of activity by conventional criteria has led to new guidelines to evaluate immunotherapeutic agents. The clinical benefit of combining vaccines with chemotherapy, radiotherapy and other immunotherapeutic and biologic agents is being evaluated in the context of disappointing results of combination GVAX vaccine and docetaxel chemotherapy.

Expert opinion: To build on the success of early phase trials, efforts must be made to optimize vaccine approaches and patient selection.     

Immunotherapy of chronic inflammatory demyelinating polyradiculoneuropathy

Introduction: There are now two chemotherapy agents, one tyrosine kinase inhibitor and three immunotherapy products approved for the treatment of metastatic melanoma, but an unmet need persists because these options are toxic and of limited therapeutic benefit. Active specific immunotherapy with therapeutic vaccines could be a useful addition to the therapeutic armamentarium, especially in patients whose tumor burden has been reduced by other treatment modalities.

Areas covered: This article reviews various sources of melanoma antigens, such as peptides, gangliosides, autologous tumor and cancer stem cells including allogeneic and autologous cell lines. The advantages and disadvantages of various antigen sources and allogeneic and autologous approaches are discussed with an emphasis on the theoretical benefits of immunizing against cancer stem cells. The results from published randomized trials testing the benefit of various vaccine approaches are summarized, as well as promising results from three Phase II trials (one randomized) of patient-specific stem cell antigen-based products.

Expert opinion: Immune responses directed toward the unique neoantigens and stem cell antigens expressed on continuously proliferating, self-renewing, autologous tumor cells could potentially overcome the limitations inherent in these other antigen-based approaches, that to date, have yielded disappointing results in randomized trials.     

Treating human cancers with heat shock protein-peptide complexes: the road ahead

Background: Heat shock proteins (HSPs) chaperone a wide array of peptides generated in cells. Association of HSPs with peptides is critical for loading of MHC I with epitopes, and has been suggested to be essential for cross-presentation. HSP–peptide complexes purified from cancer cells have been shown to chaperone tumor-specific antigenic epitopes, and have been used in experimental immunotherapy of human cancers. Two randomized Phase III trials have been completed recently. Objective: To summarize the lessons learned from the Phase III studies and to opine on the path forward. Results/conclusion: Immunization of human subjects with HSP–peptide complexes derived from autologous tumors mediates substantial clinical benefit in subjects with relatively early stage disease, consistent with results seen in animal models of cancer, and with an immunological mechanism of action. Additional clinical studies are essential for further development of this personalized medicine.     

Interleukin-21: updated review of Phase I and II clinical trials in metastatic renal cell carcinoma,metastatic melanoma and relapsed/refractory indolent non-Hodgkin's lymphoma

Importance to the field: In advanced renal cell cancer and malignant melanoma, the current FDA approved immune modulators, such as IL-2, are the only agents which provide a durable complete remission. These responses, however, occur in < 10% of treated patients and their applicability is limited to selected patients because of their toxicity. The identification of new immunotherapeutic agents with an improved response rate and toxicity profile would represent a significant advancement in the treatment of these malignancies.

Areas covered in this review: This is a comprehensive review of IL-21 including its pharmacology and current developmental status. A literature review was performed using all PubMed listed publications involving IL-21, including original research articles, reviews and abstracts. It also includes a review of current ongoing trials and information from the official product website.

What the reader will gain: Recombinant IL-21 (rIL-21) is a new immune modulator currently undergoing Phase I and II testing. It is a cytokine with a four helix structure that has structural and sequence homology to IL-2 and -15, but also possesses many unique biological properties. In this review, we evaluate the development, pharmacologic properties, safety profile and current clinical efficacy of rIL-21.

Take home message: rIL-21 has an acceptable safety profile and encouraging single agent activity in early phase renal cell carcinoma and melanoma clinical trials.     

Tisagenlecleucel-T for the treatment of acute lymphocytic leukemia

ABSTRACT

Introduction: Cellular immunotherapy with autologous or allogeneic T cells, genetically engineered to express chimeric antigen receptors (CARs) or T-cell receptors, in order to redirect their cytotoxic specificity toward malignant cells, is emerging as a promising new treatment modality. The most advanced approach in clinical development is the use of anti-CD19 CAR T-cells for the treatment of CD19⁺ B-cell malignancies, including acute lymphocytic leukemia (ALL).

Areas covered: Recently, the Food and Drug Administration (FDA) approved the first anti-CD19 CAR T-cell product, tisagenlecleucel, for the treatment of pediatric and young adult patients with relapsed/refractory ALL. In this overview, we described the advances in the field, including a summary of clinical trials with tisagenlecleucel in ALL published to date.

Expert opinion: CAR T-cell therapy has been developed in the context of small clinical studies and very few centers have had to deal with the challenges of managing CAR T-cells administration. However, this approach is likely to become a standard option for patients with relapsed/refractory B-cell lineage ALL.     

An update on RNA interference-mediated gene silencing in cancer therapy

Introduction: Based on our previous review, this article presents the new progress in RNA interference (RNAi)-mediated gene silencing in cancer therapy, and reviews the hurdles and how they might be overcome.

Areas covered: RNAi-mediated gene silencing approaches have been demonstrated in humans, and ongoing clinical trials hold promise for treating cancer or providing alternatives to traditional chemotherapies. Here we describe the broad range of approaches to achieve targeted gene silencing for cancer therapy, discuss the progress made in developing RNAi as therapeutics for cancer and highlight challenges and emerging solutions associated with its clinical development.

Expert opinion: Although the field of RNAi-based cancer therapy is still an emerging one, we have yet to get solutions for overcoming all obstacles associated with its clinical development. The current rapid advances in development of new targeted delivery strategies and noninvasive imaging methods will be big steps to explore RNAi as a new and potent clinical modality in humans.     

Evaluating the role of IL-12 based therapies in ovarian cancer: a review of the literature

Introduction: Immunotherapy, in its entirety, represents a promising field at the forefront of cancer. Treatment with potent cytokine IL-12 has provided science with many challenges, but has also demonstrated promise as therapeutic strategy in ovarian cancer.

Areas covered: This review examines the anti-tumor mechanism of action of IL-12 and the development of IL-12 as a potential therapeutic option in a variety of malignancies. It also reviews the immunogenicity of ovarian cancer and covers preclinical and clinical trials that have contributed to the advancement of IL-12 as a potential therapy for ovarian malignancy. The obstacles that researchers have overcome and currently face regarding the use of IL-12 in clinical ovarian cancer trials are also discussed.

Expert opinion: IL-12, as a therapeutic modality, is mechanistically logical and shows great promise in preclinical trials. Further clinical studies are warranted to optimize the potential of IL-12 as a treatment strategy for ovarian cancer.     

Velimogene aliplasmid

Importance of the field: Immunotherapy for cancer has been investigated for several decades, achieving limited success. The development of effective new immunotherapeutic agents has reignited interest in the filed. Intralesional injection of plasmids in order to transfect genes capable of stimulating or augmenting immune recognition and destruction of tumors is a relatively new approach.

Areas covered in this review: Our objective is to discuss the role velimogene aliplasmid (Allovectin-7^®, Vical Incorporated), a plasmid–lipid complex containing the DNA sequences encoding HLA-B7 and β2 microglobulin, as an immunotherapeutic agent.

What the reader will gain: Intralesional velimogene aliplasmid induces anti-tumor responses in a proportion of melanoma patients with locoregional and limited distant metastases. Preclinical data and the results of Phase I, II and III clinical trials with this drug are reviewed. The limited data in other malignancies is also reviewed. Velimogene aliplasmid in humans appears safe, with minimal drug-related adverse events.

Take home message: Velimogene aliplasmid has activity in melanoma with local and limited distant disease associated with an excellent safety profile. The activity of this approach is also being investigated in other malignancies.     

Immune alterations and emerging immunotherapeutic approaches in lung cancer

Introduction: Subjects with lung cancer were shown to present a variety of immune abnormalities including cellular immune dysfunction, cytokine alterations, and antigen presentation defects. As discouraging results are commonly seen with the existing therapies in lung cancer, more innovative treatment strategies are needed.

Areas covered: The authors review comprehensively the immune abnormalities in individuals with lung cancer, describe the lung cancer immunotherapy candidates that are most advanced in their clinical development, and summarize recent data from clinical trials of these agents.

Expert opinion: Enhancing the immune system represents an appealing avenue for lung cancer therapy. Several immunomodulating agents have activity in this regard including ipilimumab, a monoclonal antibody against the CTLA-4, and talactoferrin, a dendritic cell activator. In addition, a significant activity was shown with belagenpumatucel-L, a whole-cell-based vaccine that blocks the action of TGF-β2. Other promising vaccines are protein-specific vaccines against tumor antigens such as MAGE-A3, EGF, and MUC1. Although some of these immunotherapies may have lackluster performance as single agents in advanced disease, more impressive results are seen in combination with chemotherapy agents. Given their proven activity in lung cancer, these immunotherapies may soon become a powerful addition to the oncologist's toolbox.     

Herpes simplex virus oncolytic vaccine therapy in melanoma

Importance of the field: Advanced melanoma is a devastating disease with a five year survival for Stage IV disease of 10 – 20% and a median survival of 6 – 18 months depending on sub-stage. Current FDA approved therapies demonstrate limited response rates, few complete remissions and no proven survival benefit. New therapies are clearly needed. JSI/34.5-/47-/GM-CSF is a herpes simplex virus-1 (OncoVEX^GM-CSF) oncolytic vaccine therapy designed to induce local and systemic anti-tumor immune responses.

Areas covered in this review: Evolution of current herpes simplex virus oncolytic vaccines from preclinical to clinical studies from 1994 to 2010.

What the reader will gain: Preclinical studies have shown that herpes simplex virus-1 oncolytic vaccines generate local tumor destruction through the lytic action of the virus and local and systemic immune responses. Phase I studies demonstrated limited toxicities with no neurotoxicty. Phase II studies demonstrated durable regressions in patients with metastatic melanoma. A Phase III trial in melanoma is ongoing to determine clinical effectiveness, and a Phase III trial in head and neck cancer will initiate during 2010.

Take home message: JSI/34.5-/47-/GM-CSF is a new generation herpes simplex virus-1 oncolytic vaccine that demonstrates direct tumor lysis and systemic immune responses. Early clinical studies have yielded preliminary evidence of activity.     

Heat Shock Protein–Peptide Complexes, Reconstituted In Vitro, Elicit Peptide-specific Cytotoxic T Lymphocyte Response and Tumor Immunity

Heat shock protein (HSP) preparations derived from cancer cells and virus-infected cells have been shown previously to elicit cancer-specific or virus-specific immunity. The immunogenicity of HSP preparations has been attributed to peptides associated with the HSPs. The studies reported here demonstrate that immunogenic HSP–peptide complexes can also be reconstituted in vitro. The studies show that (a) complexes of hsp70 or gp96 HSP molecules with a variety of synthetic peptides can be generated in vitro; (b) the binding of HSPs with peptides is specific in that a number of other proteins tested do not bind synthetic peptides under the conditions in which gp96 molecules do; (c) HSP–peptide complexes reconstituted in vitro are immunologically active, as tested by their ability to elicit antitumor immunity and specific CD8⁺ cytolytic T lymphocyte response; and (d) synthetic peptides reconstituted in vitro with gp96 are capable of being taken up and re-presented by macrophage in the same manner as gp96– peptides complexes generated in vivo. These observations demonstrate that HSPs are CD8⁺ T cell response–eliciting adjuvants.     

AE37: a novel T-cell-eliciting vaccine for breast cancer

Introduction: Immunotherapy, including vaccines targeting the human EGFR2 (HER-2/neu) protein, is an active area of investigation in combatting breast cancer. Several vaccines are currently undergoing clinical trials, most of which are CD8⁺ T-cell-eliciting vaccines. AE37 is a promising primarily CD4⁺ T-cell-eliciting HER-2/neu breast cancer vaccine currently in clinical trials.

Areas covered: This article reviews preclinical investigations as well as findings from completed and ongoing Phase I and Phase II clinical trials of the AE37 vaccine.

Expert opinion: Clinical trials have shown the AE37 vaccine to be safe and capable of generating peptide-specific, durable immune responses. This has been shown in patients with any level of HER-2/neu expression. Early clinical findings suggest there may be benefit to AE37 vaccination in preventing breast cancer recurrence.     

Engineered oncolytic viruses to treat melanoma: where are we now and what comes next?

ABSTRACT

Introduction: Melanoma treatments have evolved rapidly in the past decade and have included the use of intratumoral injections of engineered oncolytic viruses. One such oncolytic virus is talimogene laherparepvec (T-VEC), which is the first approved therapy of its kind for use in recurrent, unresectable stage IIIB-IVM1a melanoma. Additional oncolytic viruses and their uses in combination with other interventions are currently under investigation.

Areas covered: Oncolytic viruses are being evaluated as immunotherapies for a variety of advanced malignancies. In this article, we review T-VEC, the only FDA-approved engineered oncolytic virus, in addition to ongoing research regarding other oncolytic viruses for the treatment of advanced melanomas. Finally, we discuss opportunities to improve these therapies through viral, host, and tumor-related modifications.

Expert opinion: Engineered and naturally oncolytic viruses have demonstrable local and systemic efficacy as immunotherapies in cancer. T-VEC leads the way with improved survival outcomes for unresectable, stage IIIB-IVM1a melanoma as a monotherapy, and is demonstrating superior results in combination with systemic checkpoint inhibitors. Additional viral vectors show acceptable safety profiles and varying degrees of efficacy in targeting melanoma. The indications for use of oncolytic viruses will expand as their efficacy and appropriate usage is better understood in coming years.