Immune response to sipuleucel-T in prostate cancer.
ABSTRACT: Historically, chemotherapy has remained the most commonly utilized therapy in patients with metastatic cancers. In prostate cancer, chemotherapy has been reserved for patients whose metastatic disease becomes resistant to first line castration or androgen deprivation. While chemotherapy palliates, decreases serum prostate specific antigen and improves survival, it is associated with significant side effects and is only suitable for approximately 60% of patients with castrate-resistant prostate cancer. On that basis, exploration of other therapeutic options such as active secondary hormone therapy, bone targeted treatments and immunotherapy are important. Until recently, immunotherapy has had no role in the treatment of solid malignancies aside from renal cancer and melanoma. The FDA-approved autologous cellular immunotherapy sipuleucel-T has demonstrated efficacy in improving overall survival in patients with metastatic castrate-resistant prostate cancer in randomized clinical trials. The proposed mechanism of action is reliant on activating the patients' own antigen presenting cells (APCs) to prostatic acid phosphatase (PAP) fused with granulocyte-macrophage colony stimulating factor (GM-CSF) and subsequent triggered T-cell response to PAP on the surface of prostate cancer cells in the patients body. Despite significant prolongation of survival in Phase III trials, the challenge to health care providers remains the dissociation between objective changes in serum PSA or on imaging studies after sipleucel-T and survival benefit. On that basis there is an unmet need for markers of outcome and a quest to identify immunologic or clinical surrogates to fill this role. This review focuses on the impact of sipuleucel-T on the immune system, the T and B cells, and their responses to relevant antigens and prostate cancer. Other therapeutic modalities such as chemotherapy, corticosteroids and GM-CSF and host factors can also affect immune response. The optimal timing for immunotherapy, patient selection and best sequencing with other prostate cancer therapies remain to be determined. A better understanding of immune response may help address these issues.
Project description:At present, sipuleucel-T represents the only approved immunotherapy for prostate cancer. Sipuleucel-T is an autologous cellular therapy, which primes autologous antigen-presenting cells against the prostatic acid phosphatase (PAP) antigen. For patients with metastatic castrate-resistant prostate cancer (CRPC) who are asymptomatic or minimally symptomatic, sipuleucel-T monotherapy is one of the standard of care treatment options pre- or postdocetaxel. With the approval of new treatments, including abiraterone and enzatutamide, sequencing and combination of these treatments with sipuleucel-T represent unanswered questions facing the field. Whereas steroids that are coadministered with abiraterone and chemotherapy have long been thought to be immunosuppressive, early results show that concurrent abiraterone and prednisone does not significantly impact the ability to develop immune responses to this treatment. Additional clinical data are needed to elucidate optimal sequencing of therapeutic agents in CRPC. Several novel immunotherapies are currently in development, and enrollment in clinical trials should be considered. These include PROSTVAC-VF, a viral vaccine that encodes PSA and T-cell costimulatory molecules, which is currently undergoing phase III clinical trials. DNA plasmid-based vaccines targeting different antigens, including PAP, also are under investigation. Immune checkpoint blockade with ipilimumab, a monoclonal antibody against CTLA-4, which is approved for metastatic melanoma, also is being evaluated. Whereas this treatment failed to show significant improvement in overall survival in CRPC patients treated with docetaxel, results from a phase III trial in the predocetaxel setting are pending. Conventional therapies for prostate cancer, such as radiation and hormonal therapy, may have immunomodulatory effects. Future areas for research include the sequencing and combination of immunotherapies as well as other conventional therapies.
Project description:Prostate cancer is the most common cancer in men and the second most deadly. About one-third of patients with prostate cancer will develop metastatic disease. We discuss the six United States Food and Drug Administration (FDA) approved treatments for metastatic castrate-resistant prostate cancer (mCRPC) with a strong focus on sipuleucel-T. Sipuleucel-T is the first immunotherapy shown to improve survival in asymptomatic or minimally-symptomatic mCRPC. Herein, we discuss the proposed mechanism of sipuleucel-T and its synthesis. We describe in detail the three randomized controlled trials (RTCs) that led to its approval. We also compiled the newest research regarding use of sipuleucel-T with other agents and in different patient populations. Finally, we discuss the current ongoing trials.
Project description:Sipuleucel-T was approved by the US Food and Drug Administration on April 29, 2010, as an immunotherapy for late-stage prostate cancer. To manufacture sipuleucel-T, mononuclear cells harvested from the patient are incubated with a recombinant prostatic acid phosphatase (PAP) antigen and reinfused. The manufacturer proposes that antigen-presenting cells exogenously activated by PAP induce endogenous T-cells to attack PAP-bearing prostate cancer cells. However, the lack of demonstrable tumor responses has prompted calls for scrutiny of the design of the trials in which sipuleucel-T demonstrated a 4-month survival benefit. Previously unpublished data from the sipuleucel-T trials show worse overall survival in older vs younger patients in the placebo groups, which have not been shown previously to be prognostic for survival in castration-resistant prostate cancer patients receiving chemotherapy. Because two-thirds of the cells harvested from placebo patients, but not from the sipuleucel-T arm, were frozen and not reinfused, a detrimental effect of this large repeated cell loss provides a potential alternative explanation for the survival "benefit." Patient safety depends on adequately addressing this alternative explanation for the trial results.
Project description:Immunotherapy for castration-resistant prostate cancer has continued to be an area of active research over the last several years. The enthusiasm of this approach has been based on the assumption of better tolerability and that using the body's own immune system may be more effective than either hormonal or chemotherapy. Sipuleucel-T, a dendritic cell-based vaccine, is the only approved agent in this class for the management of castrate-resistant prostate cancer. Although sipuleucel-T increases overall survival without any significant changes in progression-free survival, other forms of immunotherapy such as PSA-TRICOM, ipilimumab, and chimeric antigen receptor T cell therapy are in advanced stages of clinical development. Immune biomarkers are being developed to assess response to these treatments and also to understand how the immune system responds to these respective therapies. Combinations of immunotherapy with androgen deprivation, radiation therapy, and chemotherapy have also been explored with varying results. This review discusses the mechanisms, key preclinical and clinical data, and perspectives for immunotherapeutic agents in the treatment scheme for castrate-resistant prostate cancer.
Project description:Considerable progress has been made in prostate cancer immunotherapy over the last year, and two agents have completed phase III testing. This review will discuss the most promising immune-directed strategies in development for prostate cancer, outlining interventions that mitigate tumor-induced tolerance and highlighting several combination immunotherapy approaches.A pivotal phase III study using Sipuleucel-T, an autologous prostatic acid phosphatase (PAP)-loaded dendritic cell immunotherapy, in men with metastatic castration-resistant prostate cancer (CRPC) demonstrated a survival advantage over placebo. By contrast, two phase III studies of GVAX, an allogeneic tumor cell vaccine, in a similar patient population failed to show a survival benefit of GVAX or GVAX/docetaxel over standard docetaxel/prednisone. Other strategies currently in clinical development include the ProstVac poxviral vaccine, a PAP-encoding DNA vaccine, and immune checkpoint inhibitory approaches.Although Sipuleucel-T may receive FDA approval for patients with metastatic CRPC, challenges remain in identifying immunotherapy strategies that overcome immune tolerance, especially when disease burden is substantial. An emerging paradigm focuses on using immunotherapy together with checkpoint antagonists or in combination with conventional therapies in patients with early-stage disease. Such approaches are likely to yield optimal results, but must carefully be explored in well designed phase II studies before moving forward.
Project description:Sipuleucel-T is an autologous cellular immunotherapy that induces an immune response targeted against prostatic acid phosphatase (PAP) to treat asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer. In the phase III IMPACT study, sipuleucel-T was associated with a statistically significantly increased overall survival (OS) (median = 4.1?months) vs placebo. Patients with baseline prostate-specific antigen levels in the lowest quartile (?22.1?ng/mL) exhibited a 13-month improvement in OS with sipuleucel-T. Together, this led sipuleucel-T to be approved and recommended as first-line therapy in various guidelines for treatment of metastatic castration-resistant prostate cancer. This review discusses the varied findings about the mechanisms of action of sipuleucel-T, bringing them together to form a more coherent picture. These pieces include inducing a statistically significant increase in antigen-presenting cell activation; inducing a peripheral immune response specific to the target (PAP) and/or immunizing (PA2024) antigens; stimulating systemic cytotoxic T-lymphocyte activity; and mediating antigen spread (ie, increased antibody responses to secondary proteins in addition to PAP and PA2024). Each of these pieces individually correlates with OS. Sipuleucel-T also traffics T cells to the prostate and is associated with long-term immune memory such that a second course of treatment induces an anamnestic immune response. Prostate cancer does not have a strongly inflamed microenvironment, thus its response to immune checkpoint inhibitors is limited. Because sipuleucel-T is able to traffic T cells to the tumor, it may be an ideal combination partner with immunotherapies including immune checkpoint inhibitors or with radiation therapy.
Project description:Sipuleucel-T is an autologous cell immunotherapy for castrate-refractory prostate cancer, with US Food and Drug Administration (FDA) approval in asymptomatic or minimally symptomatic prostate cancer. In this review we address the background of prostate cancer incidence and other available therapy onto which sipuleucel-T treatment has been added, with discussion of hormone-therapy, chemotherapy, and other investigational immunotherapies. The sipuleucel-T manufacturing process, toxicity and clinical benefit are reviewed, along with an examination of the issue of clinical benefit to survival, independent of apparent changes of prostate-specific antigen (PSA) levels. Sipuleucel-T therapy is appraised from clinician, patient and immunotherapeutic perspectives, with reference to the clinical data from the pivotal trial, the mechanism of action, and the treatment process.
Project description:Prostate cancer remains highly prevalent and has a poor clinical outcome once metastatic. Sipuleucel-T is an autologous cellular immunotherapy approved for the treatment of metastatic castration-resistant prostate cancer (mCRPC). Sipuleucel-T treatment extends survival but is independent of traditional short-term markers of treatment response observed with chemotherapy and contemporary hormonal treatments. Therefore, it is essential that clinicians understand the mechanism of action of sipuleucel-T and how this can translate in the clinic.This article aims to summarize the current knowledge of sipuleucel-T therapy and its effects in mCRPC.Relevant publications describing sipuleucel-T clinical data and information relating to immunotherapies were identified.Treatment with sipuleucel-T extends survival, with side effects being usually mild or moderate and manageable within the outpatient setting. The long-term immune responses generated by sipuleucel-T correlate with a survival benefit. Sipuleucel-T shows a greater magnitude of clinical benefit when used in patients earlier in the mCRPC setting.Sipuleucel-T stimulates long-lived immune responses that translate into long-term clinical benefit. The treatment course (three infusions at weeks 0, 2, and 4) is associated with manageable side effects. Short-term markers of future benefit would be clinically useful, and information on effective treatment combinations or sequences is awaited. Sipuleucel-T treatment directs the patient's own immune system to target and remove prostate cancer cells and increases life expectancy. Patients whose cancer is less advanced generally have a more 'active' immune system and may benefit the most from this treatment.
Project description:Prostate cancer is the most common noncutaneous cancer and the second leading cause of death from cancer in men in most western countries. Advanced prostate cancer is typically sensitive to androgen-deprivation therapy, but invariably progresses to the castration-resistant state. Most current prostate cancer treatments are based on cytotoxicity directed against tumor cells via androgen-deprivation therapy or chemotherapy. Chemotherapy with docetaxel represents the standard first-line treatment in patients with castration-resistant prostate cancer (CRPC). Following progression after treatment with docetaxel, cabazitaxel (XRP6258)-prednisone treatment leads to a significantly longer overall survival (OS) time than with mitoxantrone-prednisone. Several other novel agents are currently being evaluated, including sipuleucel-T, abiraterone acetate, and MDV3100, as well as the radionuclide alpharadin. The cell-based immunotherapy sipuleucel-T produces longer OS times in chemotherapy-naïve patients, whereas the androgen biosynthesis inhibitor abiraterone acetate results in longer OS times following docetaxel. It is envisioned that these agents will change the standard of care for patients with metastatic CRPC. This review focuses on the clinical development of cabazitaxel and abiraterone acetate.
Project description:BACKGROUND:Sipuleucel-T is an autologous cellular immunotherapy that is FDA approved for the treatment of asymptomatic or minimally symptomatic metastatic castrate-resistant prostate cancer (mCRPC). The IMPACT registry trial demonstrated a 4.1 month survival benefit, but not a consistent PSA response or improvement in progression-free survival. Based upon several factors, including this lack of objective treatment response, sipuleucel-T has been under-utilized in this patient population, despite current NCCN recommendations. METHODS:In order to explore if delayed treatment response occurs in a subset of patients, we performed a single institutional retrospective analysis of mCRPC patients treated with sipuleucel-T and ongoing ADT alone. Within that group, we then identified a subset of sipuleucel-T-treated men with long-term disease control and no additional interventions. To independently confirm this finding, we evaluated a total of 336 patients from 4 large urology group practices treated with sipuleucel-T between 2010 and 2014 and identified 44 patients who met the same criteria and demonstrated evidence of PSA stabilization post sipuleucel-T treatment. RESULTS:For this subgroup of patients, 79% (95% CI: 64.5%, 88.1%) survived 36 months with a median time to subsequent therapy of 17.8 months (95% CI 10.3, 25.3). CONCLUSIONS:Although patient selection could account for some or all of these results, these data support the utilization of sipuleucel-T alone in select mCRPC patients that is associated with a delay in disease progression and a good overall prognosis.