Impact of tumour volume on the potential efficacy of therapeutic vaccines

Personalized dendritic cell vaccine in multimodal individualized combination therapy improves survival in high-risk pediatric cancer patients

A lot of hope for high-risk cancers is being pinned on immunotherapy but the evidence in children is lacking due to the rarity and limited efficacy of single-agent approaches. Here, we aim to assess the effectiveness of multimodal therapy comprising a personalized dendritic cell (DC) vaccine in children with relapsed and/or high-risk solid tumors using the N-of-1 approach in real-world scenario. A total of 160 evaluable events occurred in 48 patients during the 4-year follow-up. Overall survival of the cohort was 7.03 years. Disease control after vaccination was achieved in 53.8% patients. Comparative survival analysis showed the beneficial effect of DC vaccine beyond 2 years from initial diagnosis (HR = 0.53, P = .048) or in patients with disease control (HR = 0.16, P = .00053). A trend for synergistic effect with metronomic cyclophosphamide and/or vinblastine was indicated (HR = 0.60 P = .225). A strong synergistic effect was found for immune check-point inhibitors (ICIs) after priming with the DC vaccine (HR = 0.40, P = .0047). In conclusion, the personalized DC vaccine was an effective component in the multimodal individualized treatment. Personalized DC vaccine was effective in less burdened or more indolent diseases with a favorable safety profile and synergized with metronomic and/or immunomodulating agents.

Dendritic cells loaded with allogeneic tumour cell lysate plus best supportive care versus best supportive care alone in patients with pleural mesothelioma as maintenance therapy after chemotherapy (DENIM): a multicentre, open-label, randomised, phase 2/3 study

BACKGROUND

Dendritic cell immunotherapy has proven to be safe and induces an immune response in humans. We aimed to establish the efficacy of dendritic cells loaded with allogeneic tumour cell lysate (MesoPher, Amphera BV, 's-Hertogenbosch, Netherlands) as maintenance therapy in patients with pleural mesothelioma.

METHODS

In this open-label, randomised, phase 2/3 study, patients with histologically confirmed unresectable pleural mesothelioma, aged 18 years or older, with an Eastern Cooperative Oncology Group performance status score of 0-1, and non-progressing disease after four to six cycles of standard chemotherapy (with pemetrexed 500 mg/m2 plus platinum [cisplatin 75 mg/m2 or carboplatin area under the curve of 5]) were recruited from four centres in Belgium, France, and The Netherlands. Participants were randomly assigned (1:1), using block randomisation (block size of 4), stratified by centre and histology (epithelioid vs other), to MesoPher treatment plus best supportive care or best supportive care alone. Patients received up to a maximum of five MesoPher infusions, with treatment administered on days 1, 15, and 29, and weeks 18 and 30. At each timepoint, participants received an injection of 25 × 106 dendritic cells (two-thirds of the dendritic cells were administered intravenously and a third were injected intradermally). Best supportive care was per local institutional standards. The primary endpoint was overall survival, assessed in all participants randomly assigned to treatment (full analysis set) and safety assessed in all randomly assigned participants, and who underwent leukapheresis if they were in the MesoPher group. This study is registered with ClinicalTrials.gov, NCT03610360, and is closed for accrual.

FINDINGS

Between June 21, 2018, and June 10, 2021, 176 patients were screened and randomly assigned to the MesoPher group (n=88) or best supportive care alone group (n=88). One participant in the MesoPher group did not undergo leukapheresis. Mean age was 68 years (SD 8), 149 (85%) of 176 were male, 27 (15%) were female, 173 (98%) were White, two were Asian (1%), and one (1%) was other race. As of data cutoff (June 24, 2023), after a median follow up of 15·1 months (IQR 9·5-22·4), median overall survival was 16·8 months (95% CI 12·4-20·3; 61 [69%] of 88 died) in the MesoPher group and 18·3 months (14·3-21·9; 59 [67%] of 88 died) in the best supportive care group (hazard ratio 1·10 [95% CI 0·77-1·57]; log-rank p=0·62). The most common grade 3-4 treatment-emergent adverse events were chest pain (three [3%] of 87 in the MesoPher group vs two [2%] of 88 in the best supportive care group), dyspnoea (none vs two [2%]), anaemia (two [2%] vs none), nausea (none vs two [2%]), and pneumonia (none vs two [2%]). No deaths due to treatment-emergent adverse events were recorded. Treatment-related adverse events consisted of infusion-related reactions (fever, chills, and fatigue), which occurred in 64 (74%) of 87 patients in the MesoPher group, and injection-site reactions (itch, erythema, and induration), which occurred in 73 (84%) patients, and all were grade 1-2 in severity. No deaths were determined to be treatment related.

INTERPRETATION

MesoPher did not show improvement in overall survival in patients with pleural mesothelioma. Immune checkpoint therapy is now standard of care in pleural mesothelioma. Further randomised studies are needed of combinations of MesoPher and immune checkpoint therapy, which might increase efficacy without adding major toxicities.

FUNDING

Amphera BV and EU HORIZON.

Molecular Imaging of Innate Immunity and Immunotherapy

The innate immune system plays a key role as the first line of defense in various human diseases including cancer, cardiovascular and inflammatory diseases. In contrast to tissue biopsies and blood biopsies, in vivo imaging of the innate immune system can provide whole body measurements of immune cell location and function and changes in response to disease progression and therapy. Rationally developed molecular imaging strategies can be used in evaluating the status and spatio-temporal distributions of the innate immune cells in near real-time, mapping the biodistribution of novel innate immunotherapies, monitoring their efficacy and potential toxicities, and eventually for stratifying patients that are likely to benefit from these immunotherapies. In this review, we will highlight the current state-of-the-art in noninvasive imaging techniques for preclinical imaging of the innate immune system particularly focusing on cell trafficking, biodistribution, as well as pharmacokinetics and dynamics of promising immunotherapies in cancer and other diseases; discuss the unmet needs and current challenges in integrating imaging modalities and immunology and suggest potential solutions to overcome these barriers.

A Phase 2, Double-blind, Randomized Controlled Trial of PROSTVAC in Prostate Cancer Patients on Active Surveillance

BACKGROUND

There is an unmet clinical need for interventions to prevent disease progression in patients with localized prostate cancer on active surveillance (AS).

OBJECTIVE

To determine the immunologic response to the PROSTVAC vaccine and the clinical indicators of disease progression in patients with localized prostate cancer on AS.

DESIGN, SETTING, AND PARTICIPANTS

This was a phase 2, double-blind, randomized controlled trial in 154 men with low- or intermediate-risk prostate cancer on AS.

INTERVENTION

Participants were randomized (2:1) to receive seven doses of subcutaneous PROSTVAC, a vaccinia/fowlpox viral vector-based immunotherapy containing a prostate-specific antigen (PSA) transgene and three T-cell co-stimulatory molecules, or an empty fowlpox vector (EV) over 140 d.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary outcome was the change from baseline in CD4 and CD8 T-cell infiltration in biopsy tumor tissue. Key secondary outcomes were safety and changes in prostate biopsy tumor pathology, peripheral antigen-specific T cells, and serum PSA. Continuous variables were compared using nonparametric tests. Categorical variables were compared using Fisher's exact test.

RESULTS AND LIMITATIONS

The PROSTVAC/EV vaccination was well tolerated. All except one participant completed the vaccination series. Changes in CD4 or CD8 density in biopsy tumor tissue did not differ between the PROSTVAC and EV arms. The proportions of patients with Gleason upgrading to grade group 3 after treatment was similar between the arms. There were no differences in postvaccination peripheral T-cell responses or the PSA change from baseline to 6-mo post-treatment follow-up between the groups.

CONCLUSIONS

In this first-of-kind trial of immunotherapy in patients on AS for prostate cancer, PROSTVAC did not elicit more favorable prostate tissue or peripheral T-cell responses than the EV. There was no difference between the arms in clinicopathologic effects. Despite the null findings, this is the first study reporting the feasibility and acceptability of an immunotherapy intervention in the AS setting.

PATIENT SUMMARY

We looked at responses after an experimental prostate cancer vaccine in patients with prostate cancer on active surveillance (AS). Participants who received the vaccine did not show more favorable outcomes than those receiving the control. Despite these findings, this is the first report showing the feasibility and acceptability of immunotherapy for prostate cancer in patients on AS.

Dendritic Cell Vaccines: A Promising Approach in the Fight against Ovarian Cancer

Simple Summary

With an overall 5-year survival of only 20% for advanced-stage ovarian cancer patients, enduring and effective therapies are a highly unmet clinical need. Current standard-of-care therapies are able to improve progression-free survival; however, patients still relapse. Moreover, immunotherapy has not resulted in clear patient benefits so far. In this situation, dendritic cell vaccines can serve as a potential therapeutic addition against ovarian cancer. In the current review, we provide an overview of the different dendritic cell subsets and the roles they play in ovarian cancer. We focus on the advancements in dendritic cell vaccination against ovarian cancer and highlight the key outcomes and pitfalls associated with currently used strategies. Finally, we address future directions that could be taken to improve the dendritic cell vaccination outcomes in ovarian cancer.

Abstract

Ovarian cancer (OC) is the deadliest gynecological malignancy in developed countries and is the seventh-highest cause of death in women diagnosed with cancer worldwide. Currently, several therapies are in use against OC, including debulking surgery, chemotherapy, as well as targeted therapies. Even though the current standard-of-care therapies improve survival, a vast majority of OC patients relapse. Additionally, immunotherapies have only resulted in meager patient outcomes, potentially owing to the intricate immunosuppressive nexus within the tumor microenvironment. In this scenario, dendritic cell (DC) vaccination could serve as a potential addition to the therapeutic options available against OC. In this review, we provide an overview of current therapies in OC, focusing on immunotherapies. Next, we highlight the potential of using DC vaccines in OC by underscoring the different DC subsets and their functions in OC. Finally, we provide an overview of the advances and pitfalls of current DC vaccine strategies in OC while providing future perspectives that could improve patient outcomes.

Current challenges in the manufacture of clinical-grade autologous whole cell vaccines for hematological malignancies

Autologous whole cell vaccines use a patient's own tumor cells as a source of antigen to elicit an anti-tumor immune response in vivo. Recently, the authors conducted a systematic review of clinical trials employing these products in hematological cancers that showed a favorable safety profile and trend toward efficacy. However, it was noted that manufacturing challenges limit both the efficacy and clinical implementation of these vaccine products. In the current literature review, the authors sought to define the issues surrounding the manufacture of autologous whole cell products for hematological cancers. The authors describe key factors, including the acquisition, culture, cryopreservation and transduction of malignant cells, that require optimization for further advancement of the field. Furthermore, the authors provide a summary of pre-clinical work that informs how the identified challenges may be overcome. The authors also highlight areas in which future basic research would be of benefit to the field. The goal of this review is to provide a roadmap for investigators seeking to advance the field of autologous cell vaccines as it applies to hematological malignancies.

Dendritic Cells and Cancer Immunotherapy: The Adjuvant Effect

Dendritic cells (DCs) are immune specialized cells playing a critical role in promoting immune response against antigens, and may represent important targets for therapeutic interventions in cancer. DCs can be stimulated ex vivo with pro-inflammatory molecules and loaded with tumor-specific antigen(s). Protocols describing the specific details of DCs vaccination manufacturing vary widely, but regardless of the employed protocol, the DCs vaccination safety and its ability to induce antitumor responses is clearly established. Many years of studies have focused on the ability of DCs to provide overall survival benefits at least for a selection of cancer patients. Lessons learned from early trials lead to the hypothesis that, to improve the efficacy of DCs-based immunotherapy, this should be combined with other treatments. Thus, the vaccine’s ultimate role may lie in the combinatorial approaches of DCs-based immunotherapy with chemotherapy and radiotherapy, more than in monotherapy. In this review, we address some key questions regarding the integration of DCs vaccination with multimodality therapy approaches for cancer treatment paradigms.

Prostate Cancer Immunotherapy-Finally in From the Cold?

PURPOSE OF REVIEW

Despite significant progress, patients with metastatic prostate cancer continue to have poor prognosis. Immunotherapy has revolutionized cancer care for many tumor types but has a limited role in the treatment of prostate cancer. This review discusses the promise of immunotherapy in prostate cancer treatment with an emphasis on emerging therapeutic targets.

RECENT FINDINGS

Most prostate tumors have low tumor mutational burden and lack immunogenicity, representing significant hurdles to induction of anti-tumor immunity. However, recent research centered on deciphering key mechanisms of immune resistance in the prostate tumor microenvironment has led to the discovery of a range of new treatment targets. These discoveries are currently being translated into innovative immunotherapy clinical trials for patients with prostate cancer. Recent progress includes early evidence of activity for these novel approaches and the identification of potential predictive biomarkers of response. Novel treatment strategies using new antigen-directed therapies, drugs targeting the immunosuppressive tumor microenvironment, and combination immunotherapy therapies show great potential and are currently in clinical development. In addition, a deeper understanding of predictors of response and resistance to immunotherapy in prostate cancer is allowing for a more personalized approach to therapy.

Immunotherapy as a Precision Medicine Tool for the Treatment of Prostate Cancer

Prostate cancer (PCa) is the most frequently diagnosed type of cancer among Caucasian males over the age of 60 and is characterized by remarkable heterogeneity and clinical behavior, ranging from decades of indolence to highly lethal disease. Despite the significant progress in PCa systemic therapy, therapeutic response is usually transient, and invasive disease is associated with high mortality rates. Immunotherapy has emerged as an efficacious and non-toxic treatment alternative that perfectly fits the rationale of precision medicine, as it aims to treat patients on the basis of patient-specific, immune-targeted molecular traits, so as to achieve the maximum clinical benefit. Antibodies acting as immune checkpoint inhibitors and vaccines entailing tumor-specific antigens seem to be the most promising immunotherapeutic strategies in offering a significant survival advantage. Even though patients with localized disease and favorable prognostic characteristics seem to be the ones that markedly benefit from such interventions, there is substantial evidence to suggest that the survival benefit may also be extended to patients with more advanced disease. The identification of biomarkers that can be immunologically targeted in patients with disease progression is potentially amenable in this process and in achieving significant advances in the decision for precision treatment of PCa.

Immunotherapy for Localized Prostate Cancer: The Next Frontier?

Cancer vaccines, cytokines, and checkpoint inhibitors are immunotherapeutic agents that act within the cancer immunity cycle. Prostate cancer has provided unique opportunities for, and challenges to, immunotherapy drug development, including low tumor mutational burdens, limited expression of PD-L1, and minimal T-cell intratumoral infiltrates. Nevertheless, efforts are ongoing to help prime prostate tumors by turning a "cold" prostate cancer "hot" and thus rendering them more susceptible to immunotherapy. Combination treatments, use of molecular biomarkers, and use of new immunotherapeutic agents provide opportunities to enhance the immune response to prostate tumors.

Engineered Three-Dimensional Tumor Models to Study Natural Killer Cell Suppression

A critical hurdle associated with natural killer (NK) cell immunotherapies is inadequate infiltration and function in the solid tumor microenvironment. Well-controlled 3D culture systems could advance our understanding of the role of various biophysical and biochemical cues that impact NK cell migration in solid tumors. The objectives of this study were to establish a biomaterial which (i) supports NK cell migration and (ii) recapitulates features of the in vivo solid tumor microenvironment, to study NK infiltration and function in a 3D system. Using peptide-functionalized poly(ethylene glycol)-based hydrogels, the extent of NK-92 cell migration was observed to be largely dependent on the density of integrin binding sites and the presence of matrix metalloproteinase degradable sites. When lung cancer cells were encapsulated into the hydrogels to create tumor microenvironments, the extent of NK-92 cell migration and functional activity was dependent on the cancer cell type and duration of 3D culture. NK-92 cells showed greater migration into the models consisting of nonmetastatic A549 cells relative to metastatic H1299 cells, and reduced migration in both models when cancer cells were cultured for 7 days versus 1 day. In addition, the production of NK cell-related pro-inflammatory cytokines and chemokines was reduced in H1299 models relative to A549 models. These differences in NK-92 cell migration and cytokine/chemokine production corresponded to differences in the production of various immunomodulatory molecules by the different cancer cells, namely, the H1299 models showed increased stress ligand shedding and immunosuppressive cytokine production, particularly TGF-β. Indeed, inhibition of TGF-β receptor I in NK-92 cells restored their infiltration in H1299 models to levels similar to that in A549 models and increased overall infiltration in both models. Relative to conventional 2D cocultures, NK-92 cell mediated cytotoxicity was reduced in the 3D tumor models, suggesting the hydrogel serves to mimic some features of the biophysical barriers in in vivo tumor microenvironments. This study demonstrates the feasibility of a synthetic hydrogel system for investigating the biophysical and biochemical cues impacting NK cell infiltration and NK cell-cancer cell interactions in the solid tumor microenvironment.

Putting the Pieces Together: Completing the Mechanism of Action Jigsaw for Sipuleucel-T

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.

Photodynamic Therapy-Based Dendritic Cell Vaccination Suited to Treat Peritoneal Mesothelioma

The potential of dendritic cell (DC)-based immunotherapy to treat cancer is, nowadays, well documented. Still, the clinical success of immune checkpoint inhibitors has dampened the interest in anticancer DC vaccination. For highly life-threatening tumors that are regarded as nonimmunogenic, such as mesothelioma, however, T helper 1 immunity-biased DC-based immunotherapy could still represent an attractive strategy. In this study, we took advantage of photodynamic therapy (PDT) to induce immunogenic cell death to generate mesothelioma cell lysates for DC priming and evaluated such a vaccine to treat peritoneal mesothelioma. We found that the white light in vitro activation of the photosensitizer OR141 led to mesothelioma cell death, together with the release of bona fide danger signals that promote DC maturation. The administration of a PDT-based DC vaccine to mice bearing peritoneal mesothelioma led to highly significant survival when compared with sham or control animals treated with anti-CTLA4 antibodies. This was further supported by a strong CD8⁺ and CD4⁺ T cell response, characterized by an increased proliferation, cytotoxic activities and the expression of activation markers, including interferon gamma (IFNγ). Moreover, the PDT-based DC vaccine led to a significant increase in IFNγ⁺ T cells infiltered within mesothelioma, as determined by flow cytometry and immunohistochemistry. Finally, in vivo tracking of intraperitoneally administered DCs led us to document rapid chemotaxis towards tumor-occupied lymphatics (vs. lipopolysaccharide (LPS)-treated DC). DCs pulsed with PDT-killed mesothelioma cells also exhibited a significant increase in CCR7 receptors, together with an intrinsic capacity to migrate towards the lymph nodes. Altogether, these results indicate that PDT-based DC vaccination is particularly suited to induce a potent immune response against peritoneal mesothelioma.

Assessment of Immune Response Following Dendritic Cell-Based Immunotherapy in Pediatric Patients With Relapsing Sarcoma

Monocyte-derived dendritic cell (DC)-based vaccines loaded with tumor self-antigens represent a novel approach in anticancer therapy. We evaluated DC-based anticancer immunotherapy (ITx) in an academic Phase I/II clinical trial for children, adolescent, and young adults with progressive, recurrent, or primarily metastatic high-risk tumors. The primary endpoint was safety of intradermal administration of manufactured DCs. Here, we focused on relapsing high-risk sarcoma subgroup representing a major diagnosis in DC clinical trial. As a part of peripheral blood immunomonitoring, we evaluated quantitative association between basic cell-based immune parameters. Furthermore, we describe the pattern of these parameters and their time-dependent variations during the DC vaccination in the peripheral blood immunograms. The peripheral blood immunograms revealed distinct patterns in particular patients in the study group. As a functional testing, we evaluated immune response of patient T-cells to the tumor antigens presented by DCs in the autoMLR proliferation assay. This analysis was performed with T-cells obtained prior to DC ITx initiation and with T-cells collected after the fifth dose of DCs, demonstrating that the anticancer DC-based vaccine stimulates a preexisting immune response against self-tumor antigens. Finally, we present clinical and immunological findings in a Ewing's sarcoma patient with an interesting clinical course. Prior to DC therapy, we observed prevailing CD8+ T-cell stimulation and low immunosuppressive monocytic myeloid-derived suppressor cells (M-MDSC) and regulatory T-cells (Tregs). This patient was subsequently treated with 19 doses of DCs and experienced substantial regression of metastatic lesions after second disease relapse and was further rechallenged with DCs. In this patient, functional ex vivo testing of autologous T-cell activation by manufactured DC medicinal product during the course of DC ITx revealed that personalized anticancer DC-based vaccine stimulates a preexisting immune response against self-tumor antigens and that the T-cell reactivity persisted for the period without DC treatment and was further boosted by DC rechallenge. Trial Registration Number: EudraCT 2014-003388-39.

Perspectives on the clinical development of immunotherapy in prostate cancer

Despite impressive survival benefits with immunotherapy in patients with various solid tumors, the full potential of these agents in prostate cancer has yet to be realized. Sipuleucel-T demonstrated a survival benefit in this population, indicating that prostate cancer is an immunoresponsive disease; however, these results have not been matched by other agents. A large trial with ipilimumab in prostate cancer failed to meet its primary objective, and small trials with PD-1/PD-L1 inhibitors did not yield a significant improvement in overall response. However, several late-stage clinical trials are underway with other vaccines in prostate cancer. Reports of clinical benefit with immunotherapies, particularly when used in combination or a select population, have provided the framework to develop sound clinical trials. Understanding immunogenic modulation, antigen spread, biomarkers, and DNA-repair defects will also help mold future strategies. Through rational patient selection and evidence-based combination approaches, patients with prostate cancer may soon derive durable survival benefits with immunotherapies.

Dendritic Cell-Based Immunotherapy of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a type of blood cancer characterized by the uncontrolled clonal proliferation of myeloid hematopoietic progenitor cells in the bone marrow. The outcome of AML is poor, with five-year overall survival rates of less than 10% for the predominant group of patients older than 65 years. One of the main reasons for this poor outcome is that the majority of AML patients will relapse, even after they have attained complete remission by chemotherapy. Chemotherapy, supplemented with allogeneic hematopoietic stem cell transplantation in patients at high risk of relapse, is still the cornerstone of current AML treatment. Both therapies are, however, associated with significant morbidity and mortality. These observations illustrate the need for more effective and less toxic treatment options, especially in elderly AML and have fostered the development of novel immune-based strategies to treat AML. One of these strategies involves the use of a special type of immune cells, the dendritic cells (DCs). As central orchestrators of the immune system, DCs are key to the induction of anti-leukemia immunity. In this review, we provide an update of the clinical experience that has been obtained so far with this form of immunotherapy in patients with AML.

Dendritic Cell Cancer Therapy: Vaccinating the Right Patient at the Right Time

Immune checkpoint inhibitors propelled the field of oncology with clinical responses in many different tumor types. Superior overall survival over chemotherapy has been reported in various metastatic cancers. Furthermore, prolonged disease-free and overall survival have been reported in the adjuvant treatment of stage III melanoma. Unfortunately, a substantial portion of patients do not obtain a durable response. Therefore, additional strategies for the treatment of cancer are still warranted. One of the numerous options is dendritic cell vaccination, which employs the central role of dendritic cells in activating the innate and adaptive immune system. Over the years, dendritic cell vaccination was shown to be able to induce an immunologic response, to increase the number of tumor infiltrating lymphocytes and to provide overall survival benefit for at least a selection of patients in phase II studies. However, with the success of immune checkpoint inhibition in several malignancies and considering the plethora of other treatment modalities being developed, it is of utmost importance to delineate the position of dendritic cell therapy in the treatment landscape of cancer. In this review, we address some key questions regarding the integration of dendritic cell vaccination in future cancer treatment paradigms.

A Randomized, Double-blind, Phase II Trial of PSA-TRICOM (PROSTVAC) in Patients with Localized Prostate Cancer: The Immunotherapy to Prevent Progression on Active Surveillance Study

The Immunotherapy to Prevent Progression on Active Surveillance Study is the first trial of immunotherapy for localized prostate cancer. We randomized active surveillance patients to PSA-TRICOM (PROSTVAC) or placebo for 5mo. Final results will be available in 2019.

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.

Injectable, Tough Alginate Cryogels as Cancer Vaccines

A covalently crosslinked methacrylated (MA)-alginate cryogel vaccine has been previously shown to generate a potent response against murine melanoma, but is not mechanically robust and requires a large 16G needle for delivery. Here, covalent and ionic crosslinking of cryogels are combined with the hypothesis that this will result in a tough MA-alginate cryogel with improved injectability. All tough cryogels can be injected through a smaller, 18G needle without sustaining any damage, while covalently crosslinked-only cryogels break after injection. Cytosine-phosphodiester-guanine (CpG)-delivering tough cryogels effectively activate dendritic cells (DCs). Granulocyte macrophage colony-stimulating factor releasing tough cryogels recruit four times more DCs than blank gels by day 7 in vivo. The tough cryogel vaccine induces strong antigen-specific cytotoxic T-lymphocyte and humoral responses. These vaccines prevent tumor formation in 80% of mice inoculated with HER2/neu-overexpressing DD breast cancer cells. The MA-alginate tough cryogels provide a promising minimally invasive delivery platform for cancer vaccinations.

Targeting the Leukemia Antigen PR1 with Immunotherapy for the Treatment of Multiple Myeloma

Purpose: PR1 is a human leukocyte antigen (HLA)-A2 nonameric peptide derived from neutrophil elastase (NE) and proteinase 3 (P3). We have previously shown that PR1 is cross-presented by solid tumors, leukemia, and antigen-presenting cells, including B cells. We have also shown that cross-presentation of PR1 by solid tumors renders them susceptible to killing by PR1-targeting immunotherapies. As multiple myeloma is derived from B cells, we investigated whether multiple myeloma is also capable of PR1 cross-presentation and subsequently capable of being targeted by using PR1 immunotherapies.Experimental Design: We tested whether multiple myeloma is capable of cross-presenting PR1 and subsequently becomes susceptible to PR1-targeting immunotherapies, using multiple myeloma cell lines, a xenograft mouse model, and primary multiple myeloma patient samples.Results: Here we show that multiple myeloma cells lack endogenous NE and P3, are able to take up exogenous NE and P3, and cross-present PR1 on HLA-A2. Cross-presentation by multiple myeloma utilizes the conventional antigen processing machinery, including the proteasome and Golgi, and is not affected by immunomodulating drugs (IMiD). Following PR1 cross-presentation, we are able to target multiple myeloma with PR1-CTL and anti-PR1/HLA-A2 antibody both in vitro and in vivoConclusions: Collectively, our data demonstrate that PR1 is a novel tumor-associated antigen target in multiple myeloma and that multiple myeloma is susceptible to immunotherapies that target cross-presented antigens. Clin Cancer Res; 24(14); 3386-96. ©2018 AACR.

Abscopal effects of radiotherapy and combined mRNA-based immunotherapy in a syngeneic, OVA-expressing thymoma mouse model

BACKGROUND

Tumor metastasis and immune evasion present major challenges of cancer treatment. Radiotherapy can overcome immunosuppressive tumor microenvironments. Anecdotal reports suggest abscopal anti-tumor immune responses. This study assesses abscopal effects of radiotherapy in combination with mRNA-based cancer vaccination (RNActive®).

METHODS

C57BL/6 mice were injected with ovalbumin-expressing thymoma cells into the right hind leg (primary tumor) and left flank (secondary tumor) with a delay of 4 days. Primary tumors were irradiated with 3 × 2 Gy, while secondary tumors were shielded. RNA and combined treatment groups received mRNA-based RNActive® vaccination.

RESULTS

Radiotherapy and combined radioimmunotherapy significantly delayed primary tumor growth with a tumor control in 15 and 53% of mice, respectively. In small secondary tumors, radioimmunotherapy significantly slowed growth rate compared to vaccination (p = 0.002) and control groups (p = 0.01). Cytokine microarray analysis of secondary tumors showed changes in the cytokine microenvironment, even in the non-irradiated contralateral tumors after combination treatment.

CONCLUSION

Combined irradiation and immunotherapy is able to induce abscopal responses, even with low, normofractionated radiation doses. Thus, the combination of mRNA-based vaccination with irradiation might be an effective regimen to induce systemic anti-tumor immunity.

Immunotherapy in pancreatic adenocarcinoma-overcoming barriers to response

Pancreatic adenocarcinoma (PAC) remains one of the leading causes of cancer-related death. Despite multiple advances in targeted and immune therapies, the 5-year survival in advanced PAC remains poor. In this review, we discuss some of the unique aspects of the tumor microenvironment (TME) in PAC that may contribute to its resistance to immune therapies, as well as opportunities to potentially overcome some of these inherent barriers. Furthermore, we discuss strategies to enable immune therapies in PAC such as cytotoxic chemotherapy and radiation therapy, cancer vaccines, cytokine based therapy, oncolytic viruses, and adoptive T-cell therapy. Finally, we address a variety of targeted therapies as a strategy to further amplify immune responses in PAC.

Effect of Modified Vaccinia Ankara-5T4 and Low-Dose Cyclophosphamide on Antitumor Immunity in Metastatic Colorectal Cancer: A Randomized Clinical Trial

IMPORTANCE

The success of immunotherapy with checkpoint inhibitors is not replicated in most cases of colorectal cancer; therefore, different strategies are urgently required. The oncofetal antigen 5T4 is expressed in more than 90% of cases of metastatic colorectal cancer (mCRC). Preliminary data using modified vaccinia Ankara-5T4 (MVA-5T4) in mCRC demonstrated that it safely induced serologic and T-cell responses.

OBJECTIVE

To determine whether antitumor immunity in mCRC could be increased using MVA-5T4, metronomic low-dose cyclophosphamide, or a combination of both treatments.

DESIGN, SETTING, AND PARTICIPANTS

In this randomized clinical trial, 55 patients with inoperable mCRC and prior stable disease after standard chemotherapy were enrolled at a single center and randomized to watch and wait (n = 9), cyclophosphamide treatment only (n = 9), MVA-5T4 only (n = 19), and a combination of MVA-5T4 and cyclophosphamide (n = 18). Patients were enrolled and treated from July 9, 2012, through February 8, 2016, and follow-up was completed on December 13, 2016. Data were analyzed based on intention to treat.

INTERVENTIONS

Patients randomized to a cyclophosphamide group received 50 mg twice daily on treatment days 1 to 7 and 15 to 21. Patients randomized to a MVA-5T4 group received an intramuscular injection at a dose of 1 × 109 50% tissue culture infectious dose on treatment days 22, 36, 50, 64, 78, and 106.

MAIN OUTCOMES AND MEASURES

The predefined primary end point was the magnitude of anti-5T4 immune responses (5T4-specific T-cell and antibody levels) generated at treatment week 7. Secondary end points included analysis of the kinetics of anti-5T4 responses, progression-free survival (PFS), and overall survival (OS).

RESULTS

Fifty-two patients (38 men and 14 women; mean [SD] age, 64.2 [10.1] years) were included in the study analysis. The 5T4-specific antibody immune responses were significantly increased in the MVA-5T4 (83.41 [36.09] relative units [RU]; P = .02) and combination treatment (65.81 [16.68] RU; P = .002) groups compared with no treatment (20.09 [7.20] RU). Cyclophosphamide depleted regulatory T cells in 24 of 27 patients receiving MVA-5T4, independently prolonging PFS (5.0 vs 2.5 months; hazard ratio [HR], 0.48; 95% CI, 0.21-1.11; P = .09). MVA-5T4 doubled baseline anti-5T4 responses in 16 of 35 patients, resulting in significantly prolonged PFS (5.6 vs 2.4 months; HR, 0.21; 95% CI, 0.09-0.47; P < .001) and OS (20.0 vs 10.3 months; HR, 0.32; 95% CI, 0.14-0.74; P = .008). No grade 3 or 4 adverse events were observed.

CONCLUSIONS AND RELEVANCE

This initial randomized clinical immunotherapy study demonstrates a significant survival benefit in mCRC. Prior depletion of regulatory T cells by cyclophosphamide did not increase immune responses generated by MVA-5T4 vaccination; however, cyclophosphamide and MVA-5T4 each independently induced beneficial antitumor immune responses, resulting in prolonged survival without toxic effects. Larger clinical trials are planned to further validate these data.

TRIAL REGISTRATION

isrctn.org Identifier: ISRCTN54669986.

Dendritic cell vaccination as postremission treatment to prevent or delay relapse in acute myeloid leukemia

Relapse is a major problem in acute myeloid leukemia (AML) and adversely affects survival. In this phase 2 study, we investigated the effect of vaccination with dendritic cells (DCs) electroporated with Wilms' tumor 1 (WT1) messenger RNA (mRNA) as postremission treatment in 30 patients with AML at very high risk of relapse. There was a demonstrable antileukemic response in 13 patients. Nine patients achieved molecular remission as demonstrated by normalization of WT1 transcript levels, 5 of which were sustained after a median follow-up of 109.4 months. Disease stabilization was achieved in 4 other patients. Five-year overall survival (OS) was higher in responders than in nonresponders (53.8% vs 25.0%; P = .01). In patients receiving DCs in first complete remission (CR1), there was a vaccine-induced relapse reduction rate of 25%, and 5-year relapse-free survival was higher in responders than in nonresponders (50% vs 7.7%; P < .0001). In patients age ≤65 and >65 years who received DCs in CR1, 5-year OS was 69.2% and 30.8% respectively, as compared with 51.7% and 18% in the Swedish Acute Leukemia Registry. Long-term clinical response was correlated with increased circulating frequencies of polyepitope WT1-specific CD8⁺ T cells. Long-term OS was correlated with interferon-γ⁺ and tumor necrosis factor-α⁺ WT1-specific responses in delayed-type hypersensitivity-infiltrating CD8⁺ T lymphocytes. In conclusion, vaccination of patients with AML with WT1 mRNA-electroporated DCs can be an effective strategy to prevent or delay relapse after standard chemotherapy, translating into improved OS rates, which are correlated with the induction of WT1-specific CD8⁺ T-cell response. This trial was registered at www.clinicaltrials.gov as #NCT00965224.

Role of Antigen Spread and Distinctive Characteristics of Immunotherapy in Cancer Treatment

Immunotherapy is an important breakthrough in cancer. US Food and Drug Administration-approved immunotherapies for cancer treatment (including, but not limited to, sipuleucel-T, ipilimumab, nivolumab, pembrolizumab, and atezolizumab) substantially improve overall survival across multiple malignancies. One mechanism of action of these treatments is to induce an immune response against antigen-bearing tumor cells; the resultant cell death releases secondary (nontargeted) tumor antigens. Secondary antigens prime subsequent immune responses (antigen spread). Immunotherapy-induced antigen spread has been shown in clinical studies. For example, in metastatic castration-resistant prostate cancer patients, sipuleucel-T induced early immune responses to the immunizing antigen (PA2024) and/or the target antigen (prostatic acid phosphatase). Thereafter, most patients developed increased antibody responses to numerous secondary proteins, several of which are expressed in prostate cancer with functional relevance in cancer. The ipilimumab-induced antibody profile in melanoma patients shows that antigen spread also occurs with immune checkpoint blockade. In contrast to chemotherapy, immunotherapy often does not result in short-term changes in conventional disease progression end points (eg, progression-free survival, tumor size), which may be explained, in part, by the time taken for antigen spread to occur. Thus, immune-related response criteria need to be identified to better monitor the effectiveness of immunotherapy. As immunotherapy antitumor effects take time to evolve, immunotherapy in patients with less advanced cancer may have greater clinical benefit vs those with more advanced disease. This concept is supported by prostate cancer clinical studies with sipuleucel-T, PSA-TRICOM, and ipilimumab. We discuss antigen spread with cancer immunotherapy and its implications for clinical outcomes.

Tumor Vaccines for Malignant Gliomas

Despite continued research efforts, glioblastoma multiforme (GBM) remains the deadliest brain tumor. Immunotherapy offers a novel way to treat this disease, the genetic signature of which is not completely elucidated. Additionally, these tumors are known to induce immunosuppression in the surrounding tumor microenvironment via an array of mechanisms, making effective treatment all the more difficult. The immunotherapeutic strategy of using tumor vaccines offers a way to harness the activity of the host immune system to potentially control tumor progression. GBM vaccines can react to a variety of tumor-specific antigens, which can be harvested from the patient's unique pathological condition using selected immunotherapy techniques. This article reviews the rationale behind and development of GBM vaccines, the relevant clinical trials, and the challenges involved in this treatment strategy.

A comprehensive review of immunotherapies in prostate cancer

Prostate cancer is the second most common malignant neoplasm in men worldwide and the fifth cause of cancer-related death. Although multiple new agents have been approved for metastatic castration resistant prostate cancer over the last decade, it is still an incurable disease. New strategies to improve cancer control are needed and agents targeting the immune system have shown encouraging results in many tumor types. Despite being attractive for immunotherapies due to the expression of various tumor associated antigens, the microenvironment in prostate cancer is relatively immunosuppressive and may be responsible for the failures of various agents targeting the immune system in this disease. To date, sipuleucel-T is the only immunotherapy that has shown significant clinical efficacy in this setting, although the high cost and potential trial flaws have precluded its widespread incorporation into clinical practice. Issues with patient selection and trial design may have contributed to the multiple failures of immunotherapy in prostate cancer and provides an opportunity to tailor future studies to evaluate these agents more accurately. We have reviewed all the completed immune therapy trials in prostate cancer and highlight important considerations for the next generation of clinical trials.

Dendritic cell vaccines based on immunogenic cell death elicit danger signals and T cell-driven rejection of high-grade glioma

The promise of dendritic cell (DC)-based immunotherapy has been established by two decades of translational research. Of the four malignancies most targeted with clinical DC immunotherapy, high-grade glioma (HGG) has shown the highest susceptibility. HGG-induced immunosuppression is a roadblock to immunotherapy, but may be overcome by the application of T helper 1 (T(H)1) immunity-biased, next-generation, DC immunotherapy. To this end, we combined DC immunotherapy with immunogenic cell death (ICD; a modality shown to induce T(H)1 immunity) induced by hypericin-based photodynamic therapy. In an orthotopic HGG mouse model involving prophylactic/curative setups, both biologically and clinically relevant versions of ICD-based DC vaccines provided strong anti-HGG survival benefit. We found that the ability of DC vaccines to elicit HGG rejection was significantly blunted if cancer cell-associated reactive oxygen species and emanating danger signals were blocked either singly or concomitantly, showing hierarchical effect on immunogenicity, or if DCs, DC-associated MyD88 signal, or the adaptive immune system (especially CD8(+) T cells) were depleted. In a curative setting, ICD-based DC vaccines synergized with standard-of-care chemotherapy (temozolomide) to increase survival of HGG-bearing mice by ~300%, resulting in ~50% long-term survivors. Additionally, DC vaccines also induced an immunostimulatory shift in the brain immune contexture from regulatory T cells to T(H)1/cytotoxic T lymphocyte/T(H)17 cells. Analysis of the The Cancer Genome Atlas glioblastoma cohort confirmed that increased intratumor prevalence of T(H)1/cytotoxic T lymphocyte/T(H)17 cells linked genetic signatures was associated with good patient prognosis. Therefore, pending final preclinical checks, ICD-based vaccines can be clinically translated for glioma treatment.

The evolving role of immunotherapy in prostate cancer

PURPOSE OF REVIEW

In recent clinical trials, immunotherapeutic agents have demonstrated promising results for the treatment of prostate cancer. This review discusses emerging immunotherapies for prostate cancer and their evolving role in sequencing and combination therapy.

RECENT FINDINGS

Therapeutic vaccines including PROSTVAC and DCVAC/PCa have completed promising phase 2 trials for the treatment of prostate cancer and phase 3 trials are underway. Recent evidence supports a synergistic relationship between immunotherapy agents themselves, antiandrogens and with cytotoxic chemotherapy. Prostate cancer patients with good prognostic factors, such as minimal disease burden, appear to achieve the optimal benefit from immunotherapy.

SUMMARY

Therapeutic cancer vaccines and immunomodulating agents have demonstrated activity in the treatment of prostate cancer. Immunotherapies may alter the prostate tumor microenvironment and ongoing studies aim to provide guidance on effective sequencing and combination strategies.

Improvement of anti-tumor immunity of fibroblast activation protein α based vaccines by combination with cyclophosphamide in a murine model of breast cancer

Fibroblast activation protein α (FAPα) is expressed in cancer-associated fibroblasts (CAFs), which are the main type of cells in the tumor microenvironment. CAFs exert immunosuppressive activity, which can weaken the effects of cancer immunotherapy and mainly account for poor outcomes with therapeutic vaccines. To better target and destroy CAFs, a FAPα vaccine using a modified vaccinia ankara (MVA) vector was constructed and used with a DNA vaccine reported in our previous work for heterologous prime-boost immunizations in mice. This strategy to generate anti-tumor immunity partly reduced 4T1 tumor growth through producing FAPα-specific cytotoxic T lymphocyte responses in a preventive model, but the effect required improvement. Combining the FAPα-based cancer vaccines (CpVR-FAP/MVA-FAP) with cyclophosphamide (CY), which can be used not only as a chemotherapeutic but also an immunomodulatory agent to promote a shift from immunosuppression to immunopotentiation, resulted in markedly enhanced tumor growth inhibition compared with the CpVR-FAP/MVA-FAP group. This strategy achieved synergistic effects in a therapeutic model by improving the tumor inhibition rate by 2.5-fold (90.2%), significantly enhancing cellular immunity and prolonging the survival of 4T1 tumor-bearing mice by 35% compared with the PBS group. Furthermore, CAFs, stromal factors and immunosuppressive factors such as IL-10 and Tregs were also markedly decreased by the CY combination. These results indicated that FAPα-targeted MVA boosting in combination with CY is an effective approach to improving specific anti-tumor immune responses through overcoming immunosuppression. This study may offer important advances in research on clinical cancer immunotherapies by modulating immunosuppressive factors.

Hollow Structure Improved Anti-Cancer Immunity of Mesoporous Silica Nanospheres In Vivo

Hollow and non-hollow mesoporous silica nanospheres are synthesized and used for cancer vaccine adjuvants. The hollow structure of mesoporous silica nanospheres significantly promote cellular uptake of a model cancer antigen by macrophage-like cells in vitro, improve anti-cancer immunity, CD4(+) and CD8(+) T cell populations in splenocytes of mice in vivo.

Surgical Stress Abrogates Pre-Existing Protective T Cell Mediated Anti-Tumor Immunity Leading to Postoperative Cancer Recurrence

Anti-tumor CD8+ T cells are a key determinant for overall survival in patients following surgical resection for solid malignancies. Using a mouse model of cancer vaccination (adenovirus expressing melanoma tumor-associated antigen (TAA)-dopachrome tautomerase (AdDCT) and resection resulting in major surgical stress (abdominal nephrectomy), we demonstrate that surgical stress results in a reduction in the number of CD8+ T cell that produce cytokines (IFNγ, TNFα, Granzyme B) in response to TAA. This effect is secondary to both reduced proliferation and impaired T cell function following antigen binding. In a prophylactic model, surgical stress completely abrogates tumor protection conferred by vaccination in the immediate postoperative period. In a clinically relevant surgical resection model, vaccinated mice undergoing a positive margin resection with surgical stress had decreased survival compared to mice with positive margin resection alone. Preoperative immunotherapy with IFNα significantly extends survival in surgically stressed mice. Importantly, myeloid derived suppressor cell (MDSC) population numbers and functional impairment of TAA-specific CD8+ T cell were altered in surgically stressed mice. Our observations suggest that cancer progression may result from surgery-induced suppression of tumor-specific CD8+ T cells. Preoperative immunotherapies aimed at targeting the prometastatic effects of cancer surgery will reduce recurrence and improve survival in cancer surgery patients.

Exploiting natural anti-tumor immunity for metastatic renal cell carcinoma

Clinical observations of spontaneous disease regression in some renal cell carcinoma (RCC) patients implicate a role for tumor immunity in controlling this disease. Puzzling, however, are findings that high levels of tumor infiltrating lymphocytes (TIL) are common to RCC. Despite expression of activation markers by TILs, functional impairment of innate and adaptive immune cells has been consistently demonstrated contributing to the failure of the immune system to control RCC. Immunotherapy can overcome the immunosuppressive effects of the tumor and provide an opportunity for long-term disease free survival. Unfortunately, complete response rates remain sub-optimal indicating the effectiveness of immunotherapy remains limited by tumor-specific factors and/or cell types that inhibit antitumor immune responses. Here we discuss immunotherapies and the function of multiple immune system components to achieve an effective response. Understanding these complex interactions is essential to rationally develop novel therapies capable of renewing the immune system's ability to respond to these tumors.

Dendritic Cell-Based Immunotherapy: State of the Art and Beyond

Dendritic cell (DC) vaccination in cancer patients aims to induce or augment an effective antitumor immune response against tumor antigens and was first explored in a clinical trial in the 1990s. More than two decades later, numerous clinical trials have been performed or are ongoing with a wide variety of DC subsets, culture protocols, and treatment regimens. The safety of DC vaccination and its ability to induce antitumor responses have clearly been established; however, although scattered patients with long-term benefit were reported, DC vaccines have not yet fulfilled their promise, perhaps mainly due to the lack of large-scale well-conducted phase II/III trials. To allow meaningful multicenter phase III trials, the production of DC vaccines should be standardized between centers which is now becoming feasible. To improve the efficacy of DC-based immunotherapy, it could be combined with other treatments.

Novel non-AR therapeutic targets in castrate resistant prostate cancer

Castrate resistant prostate cancer (CRPC) remains a disease with significant morbidity and mortality. The recent approval of abiraterone and enzalutamide highlight the improvements which can be made targeting the androgen receptor (AR) axis. Nonetheless, resistance inevitably develops and there is continued interest in targeting alternate pathways which cause disease resistance and progression. Here, we review non-AR targets in CRPC, with an emphasis on novel agents now in development. This includes therapeutics which target the tumour microenvironment, the bone metastatic environment, microtubules, cellular energetics, angiogenesis, the stress response, survival proteins, intracellular signal transduction, DNA damage repair and dendritic cells. Understanding the hallmarks of prostate cancer resistance in CRPC has led to the identification and development of these new targets. We review the molecular rationale, as well at the clinical experience for each of these different classes of agents which are in clinical development.

Perspectives on sipuleucel-T: Its role in the prostate cancer treatment paradigm

Sipuleucel-T is an autologous cellular immunotherapy approved in the US for patients with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). This significant advance for mCRPC treatment provides healthcare professionals with another effective therapy to extend survival. As an immunotherapy, sipuleucel-T possesses specific characteristics differentiating it from traditional therapies. At a roundtable meeting of experts, sipuleucel-T data were discussed, focusing on interpretation and clinical implications. Important differences between immunotherapies and traditional therapies were explored, e.g., mode of action, outcomes, data consistency and robustness, timing of sipuleucel-T treatment, and future perspectives in areas such as short-term markers of long-term benefit.

Refining the treatment of NSCLC according to histological and molecular subtypes

In the past decade, the characterization of non-small-cell lung cancer (NSCLC) into subtypes based on genotype and histology has resulted in dramatic improvements in disease outcome in select patient subgroups. In particular, molecularly targeted agents that inhibit EGFR or ALK are approved for the treatment of NSCLC harbouring genetic alterations in the genes encoding these proteins. Although acquired resistance usually limits the duration of response to these therapies, a number of new agents have proven effective at tackling specific resistance mechanisms to first-generation inhibitors. Large initiatives are starting to address the role of biomarker-driven targeted therapy in squamous lung cancers, and in the adjuvant setting. Immunotherapy undeniably holds great promise and our understanding of subsets of NSCLC based on patterns of immune response is continuing to evolve. In addition, efforts are underway to identify rare genomic subsets through genomic screening, functional studies, and molecular characterization of exceptional responders. This Review provides an overview of the key developments in the treatment of NSCLC, and discusses potential strategies to further optimize therapy by targeting disease subtypes.

Peptide Immunotherapy in Vaccine Development: From Epitope to Adjuvant

Vaccines are designed to educate the host immune system to prevent infectious disease or to fight against various diseases such as cancers. Peptides were first employed to provide specific immune responses while minimizing unintended allergenic or reactogenic adverse effects. Discoveries of virus or cancer-specific antigens and the advanced knowledge of immunology accelerate the peptide vaccine development. Despite the overwhelming research pipelines, a very few of them reached to market approvals or phase III clinical trials, because of the lack of efficacy. Several strategies for the next generation peptide vaccines are devised to overcome the weak immunogenicity and the poor delivery. In this review, we discuss the new promising strategies of peptide vaccine development which are recently developed in preclinical and/or clinical stage focusing the roles of peptides in the vaccine formulation from epitope to adjuvant. Additionally, we discuss the future perspectives of peptide vaccine and immunotherapy.

Prostate cancer vaccines: the long road to clinical application

Cancer vaccines as a modality of immune-based cancer treatment offer the promise of a non-toxic and efficacious therapeutic alternative for patients. Emerging data suggest that response to vaccination largely depends on the magnitude of the type I immune response generated, epitope spreading and immunogenic modulation of the tumor. Moreover, accumulating evidence suggests that cancer vaccines will likely induce better results in patients with low tumor burden and less aggressive disease. To induce long-lasting clinical responses, vaccines will need to be combined with immunoregulatory agents to overcome tumor-related immune suppression. Immunotherapy, as a treatment modality for prostate cancer, has received significant attention in the past few years. The most intriguing characteristics that make prostate cancer a preferred target for immune-based treatments are (1) its relative indolence which allows sufficient time for the immune system to develop meaningful antitumor responses; (2) prostate tumor-associated antigens are mainly tissue-lineage antigens, and thus, antitumor responses will preferentially target prostate cancer cells. But, also in the event of eradication of normal prostate epithelium as a result of immune attack, this will have no clinical consequences because the prostate gland is not a vital organ; (3) the use of prostate-specific antigen for early detection of recurrent disease allows for the initiation of vaccine immunotherapy while tumor burden is still minimal. Finally, for improving clinical outcome further to increasing vaccine potency, it is imperative to recognize prognostic and predictive biomarkers of clinical benefit that may guide to select the therapeutic strategies for patients most likely to gain benefit.

Approaches to improve development methods for therapeutic cancer vaccines

Therapeutic cancer vaccines are an immunotherapy that amplify or induce an active immune response against tumors. Notably, limitations in the methodology for existing anti-cancer drugs may subsist while applying them to cancer vaccine therapy. A retrospective analysis was performed using information obtained from ClinicalTrials.gov, PubMed, and published articles. Our research evaluated the optimal methodologies for therapeutic cancer vaccines based on (1) patient populations, (2) immune monitoring, (3) tumor response evaluation, and (4) supplementary therapies. Failure to optimize these methodologies at an early phase may impact development at later stages; thus, we have proposed some points to be considered during the early phase. Moreover, we compared our proposal with the guidance for industry issued by the US Food and Drug Administration in October 2011 entitled "Clinical Considerations for Therapeutic Cancer Vaccines". Consequently, while our research was aligned with the guidance, we hope it provides further insights in order to predict the risks and benefits and facilitate decisions for a new technology. We identified the following points for consideration: (1) include in the selection criteria the immunological stage with a prognostic value, which is as important as the tumor stage; (2) select immunological assays such as phenotype analysis of lymphocytes, based on their features and standardize assay methods; (3) utilize optimal response criteria for immunotherapy in therapeutic cancer vaccine trials; and (4) consider supplementary therapies, including immune checkpoint inhibitors, for future therapeutic cancer vaccines.

A national multicenter phase 2 study of prostate-specific antigen (PSA) pox virus vaccine with sequential androgen ablation therapy in patients with PSA progression: ECOG 9802

BACKGROUND

E9802 was a phase 2 multi-institution study conducted to evaluate the safety and effectiveness of vaccinia and fowlpox prostate-specific antigen (PSA) vaccine (step 1) followed by combination with androgen ablation therapy (step 2) in patients with PSA progression without visible metastasis.

OBJECTIVE

To test the hypothesis that vaccine therapy in this early disease setting will be safe and have a biochemical effect that would support future studies of immunotherapy in patients with minimal disease burden.

DESIGN, SETTING, AND PARTICIPANTS

Patients who had PSA progression following local therapy were treated with PROSTVAC-V (vaccinia)/TRICOM on cycle 1 followed by PROSTVAC-F (fowlpox)/TRICOM for subsequent cycles in combination with granulocyte-macrophage colony-stimulating factor (step 1). Androgen ablation was added on progression (step 2).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Step 1 primary end points included progression at 6 mo and characterization of change in PSA velocity pretreatment to post-treatment. Step 2 end points included PSA response with combined vaccine and androgen ablation.

RESULTS AND LIMITATIONS

In step 1, 25 of 40 eligible patients (63%) were progression free at 6 mo after registration (90% confidence interval [CI], 48-75). The median pretreatment PSA velocity was 0.13 log(PSA)/mo, in contrast to median postregistration velocity of 0.09 log(PSA)/mo (p=0.02), which is an increase in median PSA doubling time from 5.3 mo to 7.7 mo. No grade ≥4 treatment-related toxicity was observed. In the 27 patients eligible and treated for step 2, 20 patients achieved a complete response (CR) at 7 mo (CR rate: 74%; 90% CI, 57-87). Although supportive of larger studies in the cooperative group setting, this study is limited by the small number of patients and the absence of a control group as in a phase 3 study.

CONCLUSIONS

A viral PSA vaccine can be administered safely in the multi-institutional cooperative group setting to patients with minimal disease volume alone and combined with androgen ablation, supporting the feasibility of future phase 3 studies in this population.

PATIENT SUMMARY

These data support consideration of vaccine therapy earlier in the course of prostate cancer progression with minimal disease burden in future studies of vaccine approaches in earlier stages of disease.

Challenges in the development of a survivin vaccine (SurVaxM) for malignant glioma

There is growing interest in immunotherapy for malignant gliomas. This interest stems from a number of immunological observations, together with the failure of conventional therapeutic agents to produce broad and clinically meaningful improvements in survival and quality of life. The challenges faced in translating laboratory-based immunological observations to Phase I and II clinical trials for immunotherapy of gliomas are substantial. Nevertheless, as our understanding of the effects of active specific vaccination in glioma patients grows, results support optimism that such methods may eventually prove useful as an adjunctive treatment for these cancers. This paper highlights a number of barriers encountered in the translational development of a survivin-targeted peptide vaccine (SurVaxM) for patients with malignant gliomas.

Long-term remission of prostate cancer with extensive bone metastases upon immuno- and virotherapy: A case report

The present study reports the case of a patient with hormone-refractory metastatic prostate cancer who had failed standard therapy, but then achieved complete remission following combined treatment with local hyperthermia (LHT), Newcastle disease virus and dendritic cell (DC) vaccination, which was an unusual combination. In August 2005, the patient underwent a radical prostatectomy. Despite standard treatment, the patient developed progressive bone metastases and stopped conventional therapy in June 2007. Starting in October 2007, the patient was treated with LHT, oncolytic virotherapy and DC vaccination. Prostate-specific antigen (PSA)-levels, with the highest level of 233.8 ng/ml in January 2008, decreased to 0.8 ng/ml in late February 2008. In March 2008, a reduction in bone metastases could be detected by positron emission tomography/computed tomography. Since then, the PSA levels have remained low and the patient is doing well. The treatment induced a long-lasting antitumor memory T-cell response. This possibly explains the long-term effectiveness of this novel experimental combined treatment approach.

Therapeutic cancer vaccines and combination immunotherapies involving vaccination

Recent US Food and Drug Administration approvals of Provenge(®) (sipuleucel-T) as the first cell-based cancer therapeutic factor and ipilimumab (Yervoy(®)/anticytotoxic T-lymphocyte antigen-4) as the first "checkpoint blocker" highlight recent advances in cancer immunotherapy. Positive results of the clinical trials evaluating additional checkpoint blocking agents (blockade of programmed death [PD]-1, and its ligands, PD-1 ligand 1 and 2) and of several types of cancer vaccines suggest that cancer immunotherapy may soon enter the center stage of comprehensive cancer care, supplementing surgery, radiation, and chemotherapy. This review discusses the current status of the clinical evaluation of different classes of therapeutic cancer vaccines and possible avenues for future development, focusing on enhancing the magnitude and quality of cancer-specific immunity by either the functional reprogramming of patients' endogenous dendritic cells or the use of ex vivo-manipulated dendritic cells as autologous cellular transplants. This review further discusses the available strategies aimed at promoting the entry of vaccination-induced T-cells into tumor tissues and prolonging their local antitumor activity. Finally, the recent improvements to the above three modalities for cancer immunotherapy (inducing tumor-specific T-cells, prolonging their persistence and functionality, and enhancing tumor homing of effector T-cells) and rationale for their combined application in order to achieve clinically effective anticancer responses are addressed.

Clinical use of dendritic cells for cancer therapy

Since the mid-1990s, dendritic cells have been used in clinical trials as cellular mediators for therapeutic vaccination of patients with cancer. Dendritic cell-based immunotherapy is safe and can induce antitumour immunity, even in patients with advanced disease. However, clinical responses have been disappointing, with classic objective tumour response rates rarely exceeding 15%. Paradoxically, findings from emerging research indicate that dendritic cell-based vaccination might improve survival, advocating implementation of alternative endpoints to assess the true clinical potency of dendritic cell-based vaccination. We review the clinical effectiveness of dendritic cell-based vaccine therapy in melanoma, prostate cancer, malignant glioma, and renal cell carcinoma, and summarise the most important lessons from almost two decades of clinical studies of dendritic cell-based immunotherapy in these malignant disorders. We also address how the specialty is evolving, and which new therapeutic concepts are being translated into clinical trials to leverage the clinical effectiveness of dendritic cell-based cancer immunotherapy. Specifically, we discuss two main trends: the implementation of the next-generation dendritic cell vaccines that have improved immunogenicity, and the emerging paradigm of combination of dendritic cell vaccination with other cancer therapies.

Therapeutic cancer vaccines: past, present, and future

Therapeutic vaccines represent a viable option for active immunotherapy of cancers that aim to treat late stage disease by using a patient's own immune system. The promising results from clinical trials recently led to the approval of the first therapeutic cancer vaccine by the U.S. Food and Drug Administration. This major breakthrough not only provides a new treatment modality for cancer management but also paves the way for rationally designing and optimizing future vaccines with improved anticancer efficacy. Numerous vaccine strategies are currently being evaluated both preclinically and clinically. This review discusses therapeutic cancer vaccines from diverse platforms or targets as well as the preclinical and clinical studies employing these therapeutic vaccines. We also consider tumor-induced immune suppression that hinders the potency of therapeutic vaccines, and potential strategies to counteract these mechanisms for generating more robust and durable antitumor immune responses.