The role of sipuleucel-T in therapy for castration-resistant prostate cancer: a critical analysis of the literature

Castration-resistant prostate cancer with bone metastases: toward the best therapeutic choice

The treatment landscape for metastatic castration-resistant prostate cancer has evolved extremely in recent years and several drug classes are now available. Nonetheless, the lack of validated predictive biomarkers makes therapeutic choice and the best sequential approach difficult. The location of the metastatic site could be a valid criterion for choosing among the treatment options available. Although bone remains the most frequent metastatic site and a possible target for many drugs, recent data suggest a profound shift in the disease spectrum with visceral metastases increasing incidence. This review describes the presently available and ongoing therapies for patients with CRPC and bone metastases, focusing on the role of bone metastases as a possible driver for selecting therapies in these patients.

BRCA2 gene mutation and prostate cancer risk. Comprehensive review and update

The second most common type of tumor worldwide is prostate cancer (PCa). Certain genetic factors contribute to a risk of developing PCa of as much as 40%. BRCA1 and BRCA2 mutations have linked with an increased risk for breast, ovarian, and PCa. However, BRCA2 is the most common gene found altered in early-onset of PCa in males younger than 65. BRCA2 mutation has a higher chance of developing an advanced stage of the disease, resulting in short survival time. This review aimed to describe the genetic changes in BRCA2 that contribute to the risk of PCa, to define its role in the early diagnosis in a man with a strong family history, and to outline the purpose of genetic testing and counseling. Also, the review summarizes the impact of BRCA2 gene mutation in localized PCa, and the treatment strategies have used for PCa patients with a BRCA2 modification.

Delivery strategies of cancer immunotherapy: recent advances and future perspectives

Immunotherapy has become an emerging strategy for the treatment of cancer. Immunotherapeutic drugs have been increasing for clinical treatment. Despite significant advances in immunotherapy, the clinical application of immunotherapy for cancer patients has some challenges associated with safety and efficacy, including autoimmune reactions, cytokine release syndrome, and vascular leak syndrome. Novel strategies, particularly improved delivery strategies, including nanoparticles, scaffolds, and hydrogels, are able to effectively target tumors and/or immune cells of interest, increase the accumulation of immunotherapies within the lesion, and reduce off-target effects. Here, we briefly describe five major types of cancer immunotherapy, including their clinical status, strengths, and weaknesses. Then, we introduce novel delivery strategies, such as nanoparticle-based delivery of immunotherapy, implantable scaffolds, injectable biomaterials for immunotherapy, and matrix-binding molecular conjugates, which can improve the efficacy and safety of immunotherapies. Also, the limitations of novel delivery strategies and challenges of clinical translation are discussed.

Linked CD4 T Cell Help: Broadening Immune Attack Against Cancer by Vaccination

In the last decade, immunotherapy with monoclonal antibodies targeting immunological check points has become a breakthrough therapeutic modality for solid cancers. However, only up to 50 % of patients benefit from this powerful approach. For others vaccination might provide a plausible addition or alternative. For induction of effective anticancer immunity CD4+ T cell help is required, which is often difficult to induce to self cancer targets because of tolerogenic mechanisms. Our approach for cancer vaccines has been to incorporate into the vaccine design sequences able to activate foreign T cell help, through genetically linking cancer targets to microbial sequences (King et al. in Nat Med 4(11):1281-1286, 1998; Savelyeva et al. in Nat Biotechnol 19(8):760-764, 2001). This harnesses the non-tolerized CD4 T cell repertoire available in patients to help induction of effective immunity against fused cancer antigens. Multiple immune effector mechanisms including antibody, CD8+ T cells as well as CD4 effector T cells can be activated using this strategy. Delivery via DNA vaccines has already indicated clinical efficacy. The same principle of linked T cell help has now been transferred to other novel vaccine modalities to further potentiate immunity against cancer targets.

[Immunotherapy for the treatment of prostate cancer-a comeback?]

BACKGROUND

Prostate cancer (PCA) seems to be more of an immunologic desert than other tumor entities. It is striking that only rarely does prostate cancer show abundant immune cells and a proimmunogenic microenvironment.

OBJECTIVES

Is immunotherapy in PCA effective and which patients can benefit.

MATERIALS AND METHODS

A review of the literature and recent congress data are presented.

RESULTS

Preliminary results with sipuleucel-T for PCA cancer were very promising showing a significant overall survival benefit in randomised phase III studies and the US Federal Drug Administration (FDA) approval for this individualised vaccine. Contrary to other tumor entities this was not the immediate breakthrough to a new therapeutic era of immunotherapy but remained an isolated case and restricted to the USA. More recently, several trials evaluated immunotherapeutic agents but missed their preliminary endpoints. Interestingly, individual patients did benefit and showed long-term remission.

CONCLUSIONS

Genome sequencing and new biomarkers are also paving a novel pathway towards individualised immunotherapy for PCA. On-going research and clinical trials are exploring the question of which patients will benefit.

Next Generation Cancer Vaccines-Make It Personal!

Dramatic success in cancer immunotherapy has been achieved over the last decade with the introduction of checkpoint inhibitors, leading to response rates higher than with chemotherapy in certain cancer types. These responses are often restricted to cancers that have a high mutational burden and show pre-existing T-cell infiltrates. Despite extensive efforts, therapeutic vaccines have been mostly unsuccessful in the clinic. With the introduction of next generation sequencing, the identification of individual mutations is possible, enabling the production of personalized cancer vaccines. Combining immune check point inhibitors to overcome the immunosuppressive microenvironment and personalized cancer vaccines for directing the host immune system against the chosen antigens might be a promising treatment strategy.

Cancer vaccines: what do we need to measure in clinical trials?

Cancer immunotherapy has seen a tremendous number of failures and only few recent regulatory successes. This review is dedicated to evaluate remaining challenges in capturing clinical response with cancer vaccines. Definition of disease progression in context of clinical rather image-specific criteria and interpretation of efficacy in relation to delayed effect of cancer vaccines should be taken into account in the design of future of immunotherapy trials.

Perspectives on treatment of metastatic castration-resistant prostate cancer

The arrival of several new agents--cabazitaxel, abiraterone acetate, enzalutamide, and radium-223--is changing the treatment options and management of patients with metastatic castration-resistant prostate cancer (mCRPC). Many other novel agents are also being investigated. As new drugs become approved, new treatment strategies and markers to best select which patients will best respond to which drug are needed. This review article is a summary of a European Treatment Practices Meeting, which was convened to discuss these latest data on novel agents and current treatment strategies in the mCRPC setting.

Prostate cancer vaccines: Update on clinical development

Prostate cancer is a common malignancy among elderly men and is essentially incurable once it becomes metastatic. Results from clinical trials testing a panel of specific vaccines in patients with castration-resistant prostate cancer (CRPC) suggest that alternative therapies may one day substitute or support the current gold standard (docetaxel plus prednisone). Here, we summarize the results of germane clinical trials completed during the last 12 y and provide updates on some currently ongoing studies. As it stands, prostate cancer vaccines appear to be safe and capable of generating prostate-specific T lymphocyte responses with potential antitumor activity.

Proposed mechanisms of action for prostate cancer vaccines

Prostate cancer is responsible for the deaths of more than 33,000 American men every year. Once this disease has become metastatic, there is no curative treatment. Alternative therapies to chemotherapy and radical prostatectomy are being increasingly explored. Prostate cancer vaccines--which trigger a tumour-specific cytotoxic-T-lymphocyte-mediated immune attack by the patient's immune system--have been investigated in clinical trials with modest, yet encouraging, results. When developing and administering prostate cancer vaccines, it is critical to consider how vital parameters, such as the stage of disease progression and the nature of adjuvant therapies, could influence treatment outcome. Of particular interest are current and future strategies for diminishing the activity of regulatory T lymphocytes.

Sipuleucel-T immunotherapy for castration-resistant prostate cancer. A systematic review and meta-analysis

INTRODUCTION

Sipuleucel-T is a novel active cellular immunotherapy for the treatment of asymptomatic or minimally symptomatic metastatic castrate-resistant prostate cancer (mCRPC). It is assumed to be associated with less adverse events than conventional docetaxel-based chemotherapy.

MATERIAL AND METHODS

A systematic review of literature published between January, 1 1966 and February, 6 2012 was performed to assess the efficacy and safety of sipuleucel-T in patients with mCRPC. Databases were searched: Medline, EMBASE, Cochrane, CancerLit as well as ASCO and ESCO websites.

RESULTS

Three randomized clinical trials with a total of 737 participants fulfilled established criteria. The overall survival of patients who received sipuleucel-T in comparison to the control group was significantly longer with a hazard ratio (HR) of 0.73 (95% CI: 0.61-0.88; p = 0.001). Time to disease progression was not prolonged using sipuleucel-T compared to placebo, HR = 0.89 (95% CI: 0.75-1.05; p = 0.18). Relative benefit (RB) of serum PSA level reduction of at least 50% for sipuleucel-T compared to placebo did not meet statistical significance, RB = 1.97 (95% CI: 0.48-8.14; p = 0.38). The safety population consisted of 729 patients with mCRPC. Compared to the control group, the pooled relative risks (RR) of all adverse events - RR = 1.03 (95% CI: 1.00-1.05; p = 0.06), grade 3 to 5 adverse events - RR = 0.98 (95% CI: 0.79-1.22; p = 0.86) and cerebrovascular events - RR = 1.93 (95% CI: 0.73-5.09; p = 0.18) were not significantly higher for men treated with sipuleucel-T.

CONCLUSIONS

The use of sipuleucel-T prolonged the overall survival among men with mCRPC. No effect on time to disease progression was observed and the safety profile was acceptable.

Clinical development of novel therapeutics for castration-resistant prostate cancer: historic challenges and recent successes

There have been more drugs approved by the US Food and Drug Administration for the treatment of castration-resistant prostate cancer in the past 3 years than in the prior 3 decades, with additional drugs on the verge of approval based on the results of recently reported randomized trials. While an improvement in the understanding of the pathogenesis of castration-resistant prostate cancer has undeniably accelerated the transition of novel approaches from "bench to bedside," the recent successes in the treatment of prostate cancer are also a result of the efforts of clinical investigators to redefine the framework in which drugs for castration-resistant disease are evaluated. This review will explore the shifting paradigm in drug development for castration-resistant prostate cancer over the past several decades, and highlight how new definitions, trial designs, and endpoints have facilitated the emergence of new therapies for this challenging disease.

Castration-resistant prostate cancer: potential targets and therapies

The treatment landscape for patients with castration-resistant prostate cancer (CRPC) is undergoing significant changes with the advent of new therapies and multidisciplinary efforts by scientists and clinicians. As activation of multiple molecular pathways in the neoplastic prostate makes it impossible for single-target drugs to be completely effective in treating CRPC, this has led to combination therapy strategy, where several molecules involved in tumor growth and disease progression are targeted by a therapeutic regimen. In the present review, we provide an update on the molecular pathways that play an important role in the pathogenesis of CRPC and discuss the current wave of new treatments to combat this lethal disease.

Overview of cancer vaccines: considerations for development

Cancer immunotherapy has seen a tremendous number of failures and only few recent regulatory successes. This is a review dedicated to determine major regulatory and developmental issues around cancer immunotherapeutics. A three pillar approach should be used in setting a development path: discovery platforms and sufficient pool of validated tumor antigens, product development strategy enabling to bring the product closer to the patient and clinical development strategy accounting for competitive landscape, treatment paradigm, technical and commercial risks. Regulatory framework existing around cancer vaccines in the EU, US, Japan and some developing countries is outlined. In addition, the review covers some specific issues on the design and conduct of clinical trials with cancer vaccines.

Emerging targeted therapies for castration-resistant prostate cancer

Until recently, few therapeutic options were available for patients with castration-resistant prostate cancer (CRPC). Since 2010, four new molecules with a demonstrated benefit (sipuleucel-T, cabazitaxel, abiraterone, and denosumab) have been approved in this setting, and to-date several other agents are under investigation in clinical trials. The purpose of this review is to present an update of targeted therapies for CRPC. Presented data are obtained from literature and congress reports updated until December 2011. Targeted therapies in advanced phases of clinical development include novel androgen signaling inhibitors, inhibitors of alternative signaling pathways, anti-angiogenic agents, inhibitors that target the bone microenvironment, and immunotherapeutic agents. Radium-223 and MDV3100 demonstrated a survival advantage in phase III trials and the road for their introduction in clinical practice is rapidly ongoing. Results are also awaited for phase III studies currently underway or planned with new drugs given as monotherapy (TAK-700, cabozantinib, tasquinimod, PROSTVAC-VF, ipilimumab) or in combination with docetaxel (custirsen, aflibercept, dasatinib, zibotentan). The optimal timing, combination, and sequencing of emerging therapies remain unknown and require further investigation. Additionally, the identification of novel markers of response and resistance to these therapies may better individualize treatment for patients with CRPC.

Melanoma vaccines and modulation of the immune system in the clinical setting: building from new realities

To endow the immune system with the capacity to fight cancer has always attracted attention, although the clinical results obtained have been until recently disappointing. Cutaneous melanoma is a highly immunogenic tumor; therefore most of the attempts to produce cancer vaccines have been addressed to this disease. New advances in the comprehension of the mechanisms of antigen presentation by dendritic cells, in the immune responses triggered by adjuvants, as well as the understanding of the role of immunosuppressor molecules such as cytotoxic T-lymphocyte antigen-4 (CTLA-4), which led to the recent approval of the anti-CTLA-4 monoclonal antibody ipilimumab, have opened new hopes about the installment of immunotherapy as a new modality to treat cancer.