Recommendations from the iSBTc-SITC/FDA/NCI Workshop on Immunotherapy Biomarkers

Optimization and Validation of a Harmonized Protocol for Generating Therapeutic-Grade Dendritic Cells in a Randomized Phase II Clinical Trial, Using Two Varied Antigenic Sources

Autologous dendritic cell (DC)-based immunotherapy is a cell-based advanced therapy medicinal product (ATMP) that was first introduced more than three decades ago. In the current study, our objective was to establish a harmonized protocol using two varied antigenic sources and a good manufacturing practice (GMP)-compliant, manual method for generating clinical-grade DCs at a limited-resource academic setting. After obtaining ethical committee-approved informed consent, the recruited patients underwent leukapheresis, and single-batch DC production was carried out. Using responder-independent flow cytometric assays as quality control (QC) criteria, we propose a differentiation and maturation index (DI and MI, respectively), calculated with the QC cut-off and actual scores of each batch for comparison. Changes during cryopreservation and personnel variation were assessed periodically for up to two to three years. Using our harmonized batch production protocol, the average DI was 1.39 and MI was 1.25. Allogenic responder proliferation was observed in all patients, while IFN-gamma secretion, evaluated using flow cytometry, was detected in 10/36 patients and significantly correlated with CD8+ T cell proliferation (p value-0.0002). Tracking the viability and phenotype of cryopreserved MDCs showed a >90% viability for up to three years, while a mature DC phenotype was retained for up to one year. Our results confirm that the manual/semi-automated protocol was simple, consistent, and cost-effective, without the requirement for expensive equipment and without compromising on the quality of the final product.

A FluoroSpot B assay for the detection of IgA and IgG SARS-CoV-2 spike-specific memory B cells: Optimization and qualification for use in COVID-19 vaccine trials

BACKGROUND

The generation of antigen-specific memory B cells is crucial to the long-term effectiveness of vaccines. When the protective antibodies circulating in the blood wane, memory B cells (MBC) can be rapidly reactivated and differentiated into antibody-secreting cells during a new infection. Such MBC responses are considered to be key in providing long-term protection after infection or vaccination. Here, we describe the optimization and qualification of a FluoroSpot assay to measure MBCs directed against the SARS-CoV-2 spike protein in the peripheral blood, for use in COVID-19 vaccine trials.

METHODS

We developed a FluoroSpot assay enabling simultaneous enumeration of B cells secreting IgA or IgG spike-specific antibodies after polyclonal stimulation of peripheral blood mononuclear cells (PBMCs) with interleukin-2 and the toll-like receptor agonist R848 for 5 days. The antigen coating was optimized using a capture antibody directed against the spike subunit-2 glycoprotein of SARS-CoV-2 to immobilize recombinant trimeric spike protein onto the membrane.

RESULTS

Compared to a direct spike protein coating, the addition of a capture antibody increased the number and the quality of detected spots for both spike-specific IgA and IgG secreting cells in PBMCs from COVID-19 convalescents. The qualification showed good sensitivity of the dual-color IgA-IgG FluoroSpot assay, with lower limits of quantitation of 18 background-subtracted (BS) antibody-secreting cells (ASCs)/well for spike-specific IgA and IgG responses. Linearity was demonstrated at values ranging from 18 to 73 and from 18 to 607 BS ASCs/well for spike-specific IgA and IgG, respectively, as was precision, with intermediate precision (percentage geometric coefficients of variation) of 12% and 26% for the proportion of spike-specific IgA and IgG MBCs (ratio specific/total IgA or Ig). The assay was specific, since no spike-specific MBCs were detected in PBMCs from pre-pandemic samples; the results were below the limit of detection of 17 BS ASCs/well.

CONCLUSIONS

These results show that the dual-color IgA-IgG FluoroSpot provides a sensitive, specific, linear, and precise tool to detect spike-specific MBC responses. This MBC FluoroSpot assay is a method of choice for monitoring spike-specific IgA and IgG MBC responses induced by COVID-19 candidate vaccines in clinical trials.

Alignment of practices for data harmonization across multi-center cell therapy trials: a report from the Consortium for Pediatric Cellular Immunotherapy

Immune effector cell (IEC) therapies have revolutionized our approach to relapsed B-cell malignancies, and interest in the investigational use of IECs is rapidly expanding into other diseases. Current challenges in the analysis of IEC therapies include small sample sizes, limited access to clinical trials and a paucity of predictive biomarkers of efficacy and toxicity associated with IEC therapies. Retrospective and prospective multi-center cell therapy trials can assist in overcoming these barriers through harmonization of clinical endpoints and correlative assays for immune monitoring, allowing additional cross-trial analysis to identify biomarkers of failure and success. The Consortium for Pediatric Cellular Immunotherapy (CPCI) offers a unique platform to address the aforementioned challenges by delivering cutting-edge cell and gene therapies for children through multi-center clinical trials. Here the authors discuss some of the important pre-analytic variables, such as biospecimen collection and initial processing procedures, that affect biomarker assays commonly used in IEC trials across participating CPCI sites. The authors review the recent literature and provide data to support recommendations for alignment and standardization of practices that can affect flow cytometry assays measuring immune effector function as well as interpretation of cytokine/chemokine data. The authors also identify critical gaps that often make parallel comparisons between trials difficult or impossible.

Monitoring cell-mediated immune responses in AAV gene therapy clinical trials using a validated IFN-γ ELISpot method

Adeno-associated virus (AAV)-based gene therapies have recently shown promise as a novel treatment for hereditary diseases. Due to the viral origin of the vector capsid, however, cellular immune response may be elicited that could eliminate transduced target cells. To monitor cellular immune responses in clinical trials, we optimized and bioanalytically validated a sensitive, robust, and reliable interferon-γ (IFN-γ) enzyme-linked immunospot (ELISpot) assay. For method performance validation, human peripheral blood mononuclear cells (PBMCs) were stimulated with peptides derived from AAV5 capsid proteins and the encoded transgene product, human blood clotting factor VIII (FVIII), in addition to positive controls, such as peptides from the 65-kDa phosphoprotein of cytomegalovirus. We statistically assessed the limit of detection and confirmatory cutpoint, evaluated precision and linearity, and confirmed specificity using HIV peptides. Robustness parameter ranges and sample stability periods were established. The validated IFN-γ ELISpot assay was then implemented in an AAV5-FVIII gene therapy clinical trial. Cellular immune responses against the AAV5 capsid were observed in most participants as soon as 2 weeks following dose administration; only limited responses against the transgene product were detected. These data underscore the value of using validated methods for monitoring cellular immunity in AAV gene therapy trials.

Quality Verification with a Cluster-Controlled Manufacturing System to Generate Monocyte-Derived Dendritic Cells

Dendritic cell (DC) vaccines for cancer immunotherapy have been actively developed to improve clinical efficacy. In our previous report, monocyte−derived DCs induced by interleukin (IL)−4 with a low−adherence dish (low−adherent IL-4−DCs: la−IL-4−DCs) improved the yield and viability, as well as relatively prolonged survival in vitro, compared to IL-4−DCs developed using an adherent culture protocol. However, la−IL-4−DCs exhibit remarkable cluster formation and display heterogeneous immature phenotypes. Therefore, cluster formation in la−IL-4−DCs needs to be optimized for the clinical development of DC vaccines. In this study, we examined the effects of cluster control in the generation of mature IL-4−DCs, using cell culture vessels and measuring spheroid formation, survival, cytokine secretion, and gene expression of IL-4−DCs. Mature IL-4−DCs in cell culture vessels (cluster−controlled IL-4−DCs: cc−IL-4−DCs) displayed increased levels of CD80, CD86, and CD40 compared with that of la−IL-4−DCs. cc−IL-4−DCs induced antigen−specific cytotoxic T lymphocytes (CTLs) with a human leukocyte antigen (HLA)−restricted melanoma antigen recognized by T cells 1 (MART−1) peptide. Additionally, cc−IL-4−DCs produced higher levels of IFN−γ, possessing the CTL induction. Furthermore, DNA microarrays revealed the upregulation of BCL2A1, a pro−survival gene. According to these findings, the cc−IL-4−DCs are useful for generating homogeneous and functional IL-4−DCs that would be expected to promote long−lasting effects in DC vaccines.

Multimodal Molecular Imaging Detects Early Responses to Immune Checkpoint Blockade

Immune checkpoint blockade (ICB) has become a standard therapy for several cancers, however, the response to ICB is inconsistent and a method for noninvasive assessment has not been established to date. To investigate the capability of multimodal imaging to evaluate treatment response to ICB therapy, hyperpolarized ¹³C MRI using [1-¹³C] pyruvate and [1,4-¹³C2] fumarate and dynamic contrast enhanced (DCE) MRI was evaluated to detect early changes in tumor glycolysis, necrosis, and intratumor perfusion/permeability, respectively. Mouse tumor models served as platforms for high (MC38 colon adenocarcinoma) and low (B16-F10 melanoma) sensitivity to dual ICB of PD-L1 and CTLA4. Glycolytic flux significantly decreased following treatment only in the less sensitive B16-F10 tumors. Imaging [1,4-¹³C2] fumarate conversion to [1,4-¹³C2] malate showed a significant increase in necrotic cell death following treatment in the ICB-sensitive MC38 tumors, with essentially no change in B16-F10 tumors. DCE-MRI showed significantly increased perfusion/permeability in MC38-treated tumors, whereas a similar, but statistically nonsignificant, trend was observed in B16-F10 tumors. When tumor volume was also taken into consideration, each imaging biomarker was linearly correlated with future survival in both models. These results suggest that hyperpolarized ¹³C MRI and DCE MRI may serve as useful noninvasive imaging markers to detect early response to ICB therapy. SIGNIFICANCE: Hyperpolarized ¹³C MRI and dynamic contrast enhanced MRI in murine tumor models provide useful insight into evaluating early response to immune checkpoint blockade therapy.See related commentary by Cullen and Keshari, p. 3444.

CTL ELISPOT Assay and T Cell Detection

Enzyme-linked immune absorbent spot (Elispot) is a quantitative method for measuring relevant parameters of T-cell activation. The sensitivity of Elispot allows the detection of low-frequency antigen-specific T-cells that secrete cytokines and effector molecules, such as granzyme B and perforin. Cytotoxic T-cell (CTL) studies have taken advantage with this high-throughput technology by providing insights of quantity and immune kinetics. Accuracy, sensitivity, reproducibility, and robustness of Elispot resulted in a wide range of applications in research as well as in diagnostic field. Actually, CTL monitoring by Elispot is a gold standard for the evaluation of antigen-specific T-cell immunity in clinical trials and vaccine candidates where the ability to detect rare antigen-specific T-cells is of relevance for immune diagnostic. The most utilized Elispot assay is the Interferon-gamma (IFN-γ) test, a marker for CD8⁺ CTL activation, but Elispot can be also used to distinguish different subsets of activated T-cells by using other cytokines such as T-helper (Th) 1 type cells (characterized by the production of IFN-γ, IL-2, IL-6, IL-12, IL-21 and TNF-α), Th2 (producing cytokines like IL-4, IL-5, IL-10 and IL-13), and Th17 (IL-17) cells.The reliability of Elispot generated data, by the evaluation of T-cell frequency recognizing individual antigen/peptide, is the core of this method currently applied widely to investigate specific immune responses in cancer, infections, allergies, and autoimmune diseases. The Elispot Assay is competing with other methods measuring single-cell cytokine production, e.g., intracellular cytokine by FACS or Milteny cytokine secretion assay. Other types of lymphocyte frequency and function assays include limiting dilution assay (LDA), cytotoxic T-cell assay (CTL), and tetramer staining. Compared with respect to sensitivity the Elispot Assay is outranking other methods to define frequency of antigen-specific lymphocytes. The method described herein would like to offer helpful and clear protocols for researchers that apply Elispot. IFN-γ and Perforin Elispot assays will be described.

Evaluation of T-activated proteins as recall antigens to monitor Epstein-Barr virus and human cytomegalovirus-specific T cells in a clinical trial setting

BACKGROUND

Pools of overlapping synthetic peptides are routinely used for ex vivo monitoring of antigen-specific T-cell responses. However, it is rather unlikely that these peptides match those resulting from naturally processed antigens. T-activated proteins have been described as immunogenic and more natural stimulants, since they have to pass through antigen processing and comprise activation of all clinically relevant effector cell populations.

METHODS

We performed comparative analysis of numbers and cytokine expression pattern of CD4 and CD8 T cells after stimulation with recombinant, urea-formulated T-activated EBV-BZLF1, -EBNA3A, and HCMV-IE1, and -pp65 proteins or corresponding overlapping peptide pools. Freshly isolated and cryopreserved PBMC of 30 EBV- and 19 HCMV-seropositive and seven EBV- and HCMV-seronegative subjects were stimulated ex vivo and analysed for IFN-γ, TNF and IL-2 production by flow cytometry-based intracellular cytokine staining.

RESULTS

T-activated proteins showed a high specificity of 100% (EBV-BZLF1, HCMV-IE1, and -pp65) and 86% (EBV-EBNA3A), and a high T-cell stimulatory capacity of 73-95% and 67-95% using freshly isolated and cryopreserved PBMC, respectively. The overall CD4 T-cell response rates in both cohorts were comparable after stimulation with either T-activated protein or peptide pools with the exception of lower numbers of CD8 T cells detected after stimulation with T-activated EBV-EBNA3A- (p = 0.038) and HCMV-pp65- (p = 0.0006). Overall, the number of detectable antigen-specific T cells varied strongly between individuals. Cytokine expression patterns in response to T-activated protein and peptide pool-based stimulation were similar for CD4, but significantly different for CD8 T-cell responses.

CONCLUSION

EBV and HCMV-derived T-activated proteins represent innovative, highly specific recall antigens suitable for use in immunological endpoint assays to evaluate success or failure in immunotherapy clinical trials (e.g. to assess the risk of EBV and/or HCMV reactivation after allogenic hematopoietic stem cell transplantation). T-activated proteins could be of particular importance, if an impaired antigen processing (e.g. in a post-transplant setting) must be taken into account.

Dawn of Monitoring Regulatory T Cells in (Pre-)clinical Studies: Their Relevance Is Slowly Recognised

Regulatory T cells (Tregs) have a prominent role in the control of immune homeostasis. Pharmacological impact on their activity or balance with effector T cells could contribute to (impaired) clinical responses or adverse events. Monitoring treatment-related effects on T cell subsets may therefore be part of (pre-)clinical studies for medicinal products. However, the extent of immune monitoring performed in studies for marketing authorisation and the degree of correspondence with data available in the public domain is not known. We evaluated the presence of T cell immunomonitoring in 46 registration dossiers of monoclonal antibodies indicated for immune-related disorders and published scientific papers. We found that the depth of Treg analysis in registration dossiers was rather small. Nevertheless, data on treatment-related Treg effects are available in public academia-driven studies (post-registration) and suggest that Tregs may act as a biomarker for clinical responses. However, public data are fragmented and obtained with heterogeneity of experimental approaches from a diversity of species and tissues. To reveal the potential added value of T cell (and particular Treg) evaluation in (pre-)clinical studies, more cell-specific data should be acquired, at least for medicinal products with an immunomodulatory mechanism. Therefore, extensive analysis of T cell subset contribution to clinical responses and the relevance of treatment-induced changes in their levels is needed. Preferably, industry and academia should work together to obtain these data in a standardised manner and to enrich our knowledge about T cell activity in disease pathogenesis and therapies. This will ultimately elucidate the necessity of T cell subset monitoring in the therapeutic benefit-risk assessment.

Melanoma vaccines: clinical status and immune endpoints

It has been known for decades that the immune system can be spontaneously activated against melanoma. The presence of tumor infiltrating lymphocytes in tumor deposits is a positive prognostic factor. Cancer vaccination includes approaches to generate, amplify, or skew antitumor immunity. To accomplish this goal, tested approaches involve administration of tumor antigens, antigen presenting cells or other immune modulators, or direct modulation of the tumor. Because the success of checkpoint blockade can depend in part on an existing antitumor response, cancer vaccination may play an important role in future combination therapies. In this review, we discuss a variety of melanoma vaccine approaches and methods to determine the biological impact of vaccination.

Addressing current challenges and future directions in immuno-oncology: expert perspectives from the 2017 NIBIT Foundation Think Tank, Siena, Italy

A collaborative think tank involving panellists from immuno-oncology networks, clinical/translational investigators and the pharmaceutical industry was held in Siena, Italy, in October 2017 to discuss the evolving immune-oncology landscape, identify selected key challenges, and provide a perspective on the next steps required in the translation of current research and knowledge to clinical reality. While there is a trend of combining new agents (e.g., co-stimulator agonists) with a PD-1/PD-L1 treatment backbone, use of alternative combination therapy approaches should also be considered. While the rapid evolution in systems biology provides a deeper understanding of tumor and tumor microenvironment heterogeneity, there remains the need to identify and define genuinely predictive biomarkers to guide treatment and patient selection. Cross-specialty and cross-sector collaboration, along with a broader collective data-sharing approach are key to optimizing immuno-oncology therapy in clinical practice. Continued support of younger research-clinicians is essential for future success in clinical, translational and basic science investigations.

Regulatory perspective on in vitro potency assays for human dendritic cells used in anti-tumor immunotherapy

Dendritic cells (DCs) are key connectors between the innate and adaptive immune system and have an important role in modulating other immune cells. Therefore, their therapeutic application to steer immune responses is considered in various disorders, including cancer. Due to differences in the cell source and manufacturing process, each DC medicinal product is unique. Consequently, release tests to ensure consistent quality need to be product-specific. Although general guidance concerning quality control testing of cell-based therapies is available, cell type-specific regulation is still limited. Especially guidance related to potency testing is needed, because developing an in vitro assay measuring cell properties relevant for in vivo functionality is challenging. In this review, we provide DC-specific guidance for development of in vitro potency assays for characterisation and release. We present a broad overview of in vitro potency assays suggested for DC products to determine their anti-tumor functionality. Several advantages and limitations of these assays are discussed. Also, we provide some points to consider for selection and design of a potency test. The ideal functionality assay for anti-tumor products evaluates the capacity of DCs to stimulate antigen-specific T cells. Because this approach may not be feasible for release, use of surrogate potency markers could be considered, provided that these markers are sufficiently linked to the in vivo DC biological activity and clinical response. Further elucidation of the involvement of specific DC subsets in anti-tumor responses will result in improved manufacturing processes for DC-based products and should be considered during potency assay development.

Immunotherapy with cancer peptides in combination with intravesical bacillus Calmette-Guerin for patients with non-muscle invasive bladder cancer

PURPOSE

A phase I study using two peptide vaccines derived from M phase phosphoprotein 1 (MPHOSPH1) and DEP domain containing 1 (DEPDC1) demonstrated promising results for the treatment of advanced bladder cancer. Therefore, we further tested the ability of these peptides to prevent recurrence after transurethral resection of the bladder tumor in patients with non-muscle invasive bladder cancer (NMIBC).

MATERIALS AND METHODS

127 patients were enrolled in a multicenter, non-randomized phase II clinical trial. The primary endpoint was recurrence-free survival (RFS) rate, and secondary endpoints were safety and immunological response. HLA-A24-restricted peptides were subcutaneously administered in addition to intravesical BCG therapy. The exploratory endpoint evaluated differences of RFS rate between HLA-A*2402-positive (A24(+)) and -negative (A24(-)) groups.

RESULTS

A 2-year RFS rate in all patients was 74.0%. The RFS rate in the A24(+) group (n = 75) and in the A24(-) group (n = 52) were 76.0 and 71.2%, respectively. This vaccine therapy was well-tolerated and feasible. MPHOSPH1 and DEPDC1 peptide-specific cytotoxic T lymphocyte responses were observed in 75.8 and 77.5% of the A24(+) group, respectively. Patients having both peptide-specific CTL responses showed significantly better RFS than patients without CTL response (P = 0.014). In the A24(+) group, patients who had positive reaction at the injection sites (RAI) had significantly lower rates of recurrence than RAI-negative patients (P = 0.0019).

CONCLUSIONS

Cancer peptide vaccines in combination with intravesical BCG therapy demonstrated good immunogenicity and safety, and may provide benefit for preventing recurrence of NMIBC.

Folate Receptor Alpha Peptide Vaccine Generates Immunity in Breast and Ovarian Cancer Patients

Purpose: Folate receptor alpha (FR) is overexpressed in several cancers. Endogenous immunity to the FR has been demonstrated in patients and suggests the feasibility of targeting FR with vaccine or other immune therapies. CD4 helper T cells are central to the development of coordinated immunity, and prior work shows their importance in protecting against relapse. Our previous identification of degenerate HLA-class II epitopes from human FR led to the development of a broad coverage epitope pool potentially useful in augmenting antigen-specific immune responses in most patients.Patients and Methods: We conducted a phase I clinical trial testing safety and immunogenicity of this vaccine, enrolling patients with ovarian cancer or breast cancer who completed conventional treatment and who showed no evidence of disease. Patients were initially treated with low-dose cyclophosphamide and then vaccinated 6 times, monthly. Immunity and safety were examined during the vaccine period and up to 1 year later.Results: Vaccination was well tolerated in all patients. Vaccine elicited or augmented immunity in more than 90% of patients examined. Unlike recall immunity to tetanus toxoid (TT), FR T-cell responses developed slowly over the course of vaccination with a median time to maximal immunity in 5 months. Despite slow development of immunity, responsiveness appeared to persist for at least 12 months.Conclusions: The results demonstrate that it is safe to augment immunity to the FR tumor antigen, and the developed vaccine is testable for therapeutic activity in most patients whose tumors express FR, regardless of HLA genotype. Clin Cancer Res; 24(13); 3014-25. ©2018 AACR.

Folate Receptor Alpha Peptide Vaccine Generates Immunity in Breast and Ovarian Cancer Patients

Purpose: Folate receptor alpha (FR) is overexpressed in several cancers. Endogenous immunity to the FR has been demonstrated in patients and suggests the feasibility of targeting FR with vaccine or other immune therapies. CD4 helper T cells are central to the development of coordinated immunity, and prior work shows their importance in protecting against relapse. Our previous identification of degenerate HLA-class II epitopes from human FR led to the development of a broad coverage epitope pool potentially useful in augmenting antigen-specific immune responses in most patients.Patients and Methods: We conducted a phase I clinical trial testing safety and immunogenicity of this vaccine, enrolling patients with ovarian cancer or breast cancer who completed conventional treatment and who showed no evidence of disease. Patients were initially treated with low-dose cyclophosphamide and then vaccinated 6 times, monthly. Immunity and safety were examined during the vaccine period and up to 1 year later.Results: Vaccination was well tolerated in all patients. Vaccine elicited or augmented immunity in more than 90% of patients examined. Unlike recall immunity to tetanus toxoid (TT), FR T-cell responses developed slowly over the course of vaccination with a median time to maximal immunity in 5 months. Despite slow development of immunity, responsiveness appeared to persist for at least 12 months.Conclusions: The results demonstrate that it is safe to augment immunity to the FR tumor antigen, and the developed vaccine is testable for therapeutic activity in most patients whose tumors express FR, regardless of HLA genotype. Clin Cancer Res; 24(13); 3014-25. ©2018 AACR.

Regulatory perspective on in vitro potency assays for human T cells used in anti-tumor immunotherapy

The adaptive immune system is known to play an important role in anti-neoplastic responses via induction of several effector pathways, resulting in tumor cell death. Because of their ability to specifically recognize and kill tumor cells, the potential use of autologous tumor-derived and genetically engineered T cells as adoptive immunotherapy for cancer is currently being explored. Because of the variety of potential T cell-based medicinal products at the level of starting material and manufacturing process, product-specific functionality assays are needed to ensure quality for individual products. In this review, we provide an overview of in vitro potency assays suggested for characterization and release of different T cell-based anti-tumor products. We discuss functional assays, as presented in scientific advices and literature, highlighting specific advantages and limitations of the various assays. Because the anticipated in vivo mechanism of action for anti-tumor T cells involves tumor recognition and cell death, in vitro potency assays based on the cytotoxic potential of antigen-specific T cells are most evident. However, assays based on other T cell properties may be appropriate as surrogates for cytotoxicity. For all proposed assays, biological relevance of the tests and correlation of the read-outs with in vivo functionality need to be substantiated with sufficient product-specific (non-)clinical data. Moreover, further unraveling the complex interaction of immune cells with and within the tumor environment is expected to lead to further improvement of the T cell-based products. Consequently, increased knowledge will allow further optimized guidance for potency assay development.

Validation of Immunomonitoring Methods for Application in Clinical Studies: The HLA-Peptide Multimer Staining Assay

BACKGROUND

Validated assays are essential to generate data with defined specificity, consistency, and reliability. Although the process of validation is required for applying immunoassays in the context of clinical studies, reports on systematic validation of in vitro T cell assays are scarce so far. We recently validated our HLA-peptide multimer staining assay in a systematic manner so as to qualify the method for monitoring antigen-specific T cell responses after immunotherapy.

METHODS

Parameters of the assay, specificity, precision, linearity, sensitivity, and robustness were assessed systematically. Experiments were designed to address specifically each parameter and are detailed.

RESULTS

Nonspecific multimer staining was below the acceptance limit of 0.02% multimer(+) CD8(+) cells. The assay showed acceptable precision in all dimensions it was repeated (CV < 10%) and also demonstrated a linear detection (R2  > 0.99) of antigen specific cells.

CONCLUSIONS

We succeeded in validating the HLA-multimer staining assay in a systematic manner. Additionally, we propose a technical framework and recommendations that can be applied for validating other T cell assessment methods. © 2016 International Clinical Cytometry Society.

Evolving notions on immune response in colorectal cancer and their implications for biomarker development

INTRODUCTION

Colorectal cancer (CRC) still represents the third most commonly diagnosed type of cancer in men and women worldwide. CRC is acknowledged as a heterogeneous disease that develops through a multi-step sequence of events driven by clonal selections; this observation is sustained by the fact that histologically similar tumors may have completely different outcomes, including a varied response to therapy.

METHODS

In "early" and "intermediate" stage of CRC (stages II and III, respectively) there is a compelling need for new biomarkers fit to assess the metastatic potential of their disease, selecting patients with aggressive disease that might benefit from adjuvant and targeted therapies. Therefore, we review the actual notions on immune response in colorectal cancer and their implications for biomarker development.

RESULTS

The recognition of the key role of immune cells in human cancer progression has recently drawn attention on the tumor immune microenvironment, as a source of new indicators of tumor outcome and response to therapy. Thus, beside consolidated histopathological biomarkers, immune endpoints are now emerging as potential biomarkers.

CONCLUSIONS

The introduction of immune signatures and cellular and molecular components of the immune system as biomarkers is particularly important considering the increasing use of immune-based cancer therapies as therapeutic strategies for cancer patients.

Impact of granulocyte contamination on PBMC integrity of shipped blood samples: Implications for multi-center studies monitoring regulatory T cells

In centralized immune monitoring for a multi-center allergen immunotherapy trial, we observed frequent loss of CD4+ T cell integrity following staining of cultured PBMCs with our regulatory T cell flow cytometry panel. Samples were marked by a loss of total cellular events, altered scatter properties, and reduced CD3+CD4+ events. This occurred only in samples that were stained with Foxp3 and were therefore treated with Foxp3 fixation-permeabilization buffer. We identified granulocyte contamination in samples associated with a loss of integrity, and went on to test the impact of granulocyte depletion on day-old blood samples. Granulocyte depletion prevented loss of cell integrity and CD3+CD4+ events, and reduced variability in detection of Foxp3+ cells. Addition of purified neutrophils back to PBMCs altered scatter properties and detection of CD4+ T cells. Implementation of a granulocyte depletion step in our standard operating protocols has reduced assay failure due to loss of sample integrity from 31% to 0%. Routine incorporation of a granulocyte depletion step during PBMC isolation is recommended prior to downstream immune monitoring in blood with next-day processing.

Decreased intra-lymphocyte cytokines measurement in septic shock patients: A proof of concept study in whole blood

Functional testing protocols are thought to be the gold standard for the exploration of the immune system. However, in terms of routine analysis, they present numerous drawbacks and consequently their use is mainly limited to research applications. In the clinical context of septic shock, characterized by marked lymphocyte alterations, a new approach for lymphocyte intracellular cytokine measurement in whole blood upon was evaluated in a proof-of-concept study. Following lymphocyte activation, simultaneous intracellular labeling of Interferon-γ (IFN-γ), Tumor Necrosis Factor-α (TNF-α), and Interleukin-2 (IL-2) was performed in CD4⁺ and CD8⁺ T cells (identified by surface marking). The analysis was carried out by flow cytometry (6 colors). Results obtained in septic patients (n=22) were compared to those of healthy volunteers (n=8). Independently of lymphopenia, there were significant differences between groups. In particular there was significant decrease in the production of IL-2 and TNF-α in septic patients, while the production of IFN-γ was not significantly altered. Polyfunctional results showed that patients presented with increased percentages of triple negative lymphocytes. In contrast, volunteers had higher proportions of triple positive cells. The approach could be performed in a robust and consistent way, taking 4.5h to complete. Moreover, clear differences could be observed between clinical groups with this modified method. These characteristics illustrate the potential of this novel whole blood protocol for clinical applications. However, further research is required to determine the applicability compared to alternative test and to evaluate clinical performances in larger cohorts of patients.

A Clinical Study Protocol to Identify Serum Biomarkers Predictive of Response to Antipsychotics in Schizophrenia Patients

An increasing number of studies are now exploring the potential of using blood-based biomarkers for prediction of antipsychotic treatment response in studies of schizophrenia patients. Here we describe the detailed setup of a clinical study to identify biomarker candidates for prediction of response of patients prior to receiving antipsychotics over a 6-week treatment period. The main emphasis is on study design, patient recruitment, sampling and outcome measures.

The Society for Immunotherapy of Cancer Biomarkers Task Force recommendations review

The clinical successes in cancer immunotherapy have led to a critical need for biomarkers in cancer immunotherapy. It is of the utmost importance to know who is most likely to benefit from these therapies (predictive biomarkers) but also who is starting to respond (prognostic biomarkers) and how the therapy functions in order to make rational combination choices (mechanism of action biomarkers). The Society for Immunotherapy of Cancer (SITC) Biomarkers Task Force addressed the state of the art and made a series of recommendations for the field, which is summarized here.

Systematic evaluation of immune regulation and modulation

Cancer immunotherapies are showing promising clinical results in a variety of malignancies. Monitoring the immune as well as the tumor response following these therapies has led to significant advancements in the field. Moreover, the identification and assessment of both predictive and prognostic biomarkers has become a key component to advancing these therapies. Thus, it is critical to develop systematic approaches to monitor the immune response and to interpret the data obtained from these assays. In order to address these issues and make recommendations to the field, the Society for Immunotherapy of Cancer reconvened the Immune Biomarkers Task Force. As a part of this Task Force, Working Group 3 (WG3) consisting of multidisciplinary experts from industry, academia, and government focused on the systematic assessment of immune regulation and modulation. In this review, the tumor microenvironment, microbiome, bone marrow, and adoptively transferred T cells will be used as examples to discuss the type and timing of sample collection. In addition, potential types of measurements, assays, and analyses will be discussed for each sample. Specifically, these recommendations will focus on the unique collection and assay requirements for the analysis of various samples as well as the high-throughput assays to evaluate potential biomarkers.

Interferon-α-inducible Dendritic Cells Matured with OK-432 Exhibit TRAIL and Fas Ligand Pathway-mediated Killer Activity

Active human dendritic cells (DCs), which efficiently induce immune responses through their functions as antigen-presenting cells, exhibit direct anti-tumour killing activity in response to some pathogens and cytokines. These antigen-presenting and tumour killing abilities may provide a breakthrough in cancer immunotherapy. However, the mechanisms underlying this killer DC activity have not been fully proven, despite the establishment of interferon-α (IFN-α)-generated killer DCs (IFN-DCs). Here mature IFN-DCs (mIFN-DCs), generated from IFN-DCs primed with OK-432 (streptococcal preparation), exhibited elevated expression of CD86 and human leukocyte antigen-DR (minimum criteria for DC vaccine clinical trials) as well as antigen-presenting abilities comparable with those of mature IL-4-DCs (mIL-4-DCs). Interestingly, the killing activity of mIFN-DCs, which correlated with the expression of CD56 (natural killer cell marker) and was activated via the tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas ligand pathway, was stronger than that of IFN-DCs and remarkably stronger than that of mIL-4-DCs. Therefore, mIFN-DCs exhibit great potential as an anti-cancer vaccine that would promote both acquired immunity and direct tumour killing.

Validation of an IFNγ/IL2 FluoroSpot assay for clinical trial monitoring

Background

The FluoroSpot assay, an advancement of the ELISpot assay, enables simultaneous measurement of different analytes secreted at a single-cell level. This allows parallel detection of several cytokines secreted by immune cells upon antigen recognition. Easier standardization, higher sensitivity and reduced labour intensity render FluoroSpot assays an interesting alternative to flow-cytometry based assays for analysis of clinical samples. While the use of immunoassays to study immunological primary and secondary endpoints becomes increasingly attractive, assays used require pre-trial validation. Here we describe the assay validation (precision, specificity and linearity) of a FluoroSpot immunological endpoint assay detecting Interferon γ (IFNγ) and Interleukin 2 (IL2) for use in clinical trial immune monitoring.

Methods

We validated an IFNγ/IL2 FluoroSpot assay to determine Epstein-Barr virus (EBV)-specific cellular immune responses (IFNγ, IL2 and double positive IFNγ + IL2 responses), using overlapping peptide pools corresponding to EBV-proteins BZLF1 and EBNA3A. Assay validation was performed using cryopreserved PBMC of 16 EBV-seropositive and 6 EBV-seronegative donors. Precision was assessed by (i) testing 16 donors using three replicates per assay (intra-assay precision/repeatability) (ii) using two plates in parallel (intermediate precision/plate-to-plate variability) and (iii) by performing the assays on three different days (inter-assay precision/reproducibility). In addition, we determined specificity, linearity and quantification limits of the assay. Further we tested precision across the two assay systems, IFNγ/IL2 FluoroSpot and the corresponding enzymatic single cytokine ELISpot.

Results

The validation revealed: (1) a high intra-assay precision (coefficient of variation (CV) 9.96, 8.85 and 13.05 %), intermediate precision (CV 6.48, 10.20 and 12.97 %) and reproducibility (CV 20.81 %, 12,75 % and 12.07 %) depending on the analyte and antigen used; (2) a specificity of 100 %; (3) a linearity with R² values from 0.93 to 0.99 depending on the analyte. The testing of the precision across the two assay systems, adduced a concordance correlation coefficient p_c = 0.99 for IFNγ responses and p_c = 0.93 for IL2 responses, indicating a large agreement between both assay methods.

Conclusions

The validated primary endpoint assay, an EBV peptide pool specific IFNγ/IL2 FluoroSpot assay was found to be suitable for the detection of EBV-specific immune responses subject to the requirement of standardized assay procedure and data analysis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0932-7) contains supplementary material, which is available to authorized users.

Immunomonitoring in glioma immunotherapy: current status and future perspectives

Given the continued poor clinical outcomes and refractory nature of glioblastoma multiforme to traditional interventions, immunotherapy is gaining traction due to its potential for specific tumor-targeting and long-term antitumor protective surveillance. Currently, development of glioma immunotherapy relies on overall survival as an endpoint in clinical trials. However, the identification of surrogate immunologic biomarkers can accelerate the development of successful immunotherapeutic strategies. Immunomonitoring techniques possess the potential to elucidate immunological mechanisms of antitumor responses, monitor disease progression, evaluate therapeutic effect, identify candidates for immunotherapy, and serve as prognostic markers of clinical outcome. Current immunomonitoring assays assess delayed-type hypersensitivity, T cell proliferation, cytotoxic T-lymphocyte function, cytokine secretion profiles, antibody titers, and lymphocyte phenotypes. Yet, no single immunomonitoring technique can reliably predict outcomes, relegating immunological markers to exploratory endpoints. In response, the most recent immunomonitoring assays are incorporating emerging technologies and novel analysis techniques to approach the goal of identifying a competent immunological biomarker which predicts therapy responsiveness and clinical outcome. This review addresses the current status of immunomonitoring in glioma vaccine clinical trials with emphasis on correlations with clinical response.

Cancer immunotherapy drives implementation science in oncology

Cancer immunotherapy has come a long way. The hope that immunological approaches may help cancer patients has sparked many initiatives in research and development (R&D). For many years, progress was modest and disappointments were frequent. Today, the increasing scientific and medical knowledge has established a solid basis for improvements. Considerable clinical success was first achieved for patients with hematological cancers. More recently, immunotherapy has entered center stage in the development of novel therapies against solid cancers. Together with R&D in angiogenesis, the field of immunology has fundamentally extended the scientific scope, which has evolved from a cancer-cell-centered view to a comprehensive and integrated vision of tumor biology. Current R&D is focused on a large array of possible disease mechanisms, driven by cancer cells, and amplified by tumor stroma, inflammatory and immunological actors, blood and lymph vessels, and the “macroenvironment," i.e. systemic mechanisms of the host, particularly of the haematopoietic system. Contrasting to this large spectrum of pathophysiological events promoting tumor growth, only a small number of biological mechanisms, namely of the immune system, have the potential to counteract tumor growth. They are of prime interest because therapeutic enhancement may result in clinical benefit for patients. This special issue is dedicated to immunotherapeutics against cancer, with particular emphasis on vaccination and combination therapies, providing updates and extended insight in this booming field.

The FDA guidance on therapeutic cancer vaccines: the need for revision to include preventive cancer vaccines or for a new guidance dedicated to them

Cancer vaccines based on antigens derived from self molecules rather than pathogens have been under basic and clinical investigations for many years. Up until very recently, they had been tested primarily in the setting of metastatic disease with the goal to engage the immune system in slowing down disease progression. Many therapeutic vaccine trials, either investigator initiated or led by pharmaceutical companies, have been completed and many are currently ongoing, following the FDA Guidance on therapeutic cancer vaccines published in 2011. In recent years, the target of cancer vaccines is being shifted to early cancer and even premalignant disease with the goal of preventing cancer. Although some issues addressed in the FDA Guidance on therapeutic vaccines apply to preventive vaccines, many do not. Here, we discuss a set of recommendations for revising the current Guidance to also cover preventive vaccines, or to include in a new Guidance dedicated specifically to vaccines for cancer prevention.

Adoptive T-cell therapy: a need for standard immune monitoring

Cancer immune therapy, in particular the use of checkpoint inhibitors and adoptive transfer of T cells has recently demonstrated significant clinical responses against several tumor types. Unfortunately, these therapies are frequently accompanied by severe toxicities, underscoring the need for markers that provide information on therapy response. Monitoring immune responses in the tumor microenvironment and peripheral blood prior to and during these therapies will provide better insight into the mechanisms underlying clinical activities, and will potentially enable the identification of such markers. In this review, we present an overview of adoptive T-cell trials conducted with a special focus on immune monitoring, and argue that accurate monitoring of T cells is pivotal to further development of immune therapies to treat cancer.

Dendritic cell-based vaccination in cancer: therapeutic implications emerging from murine models

Dendritic cells (DCs) play a pivotal role in the orchestration of immune responses, and are thus key targets in cancer vaccine design. Since the 2010 FDA approval of the first cancer DC-based vaccine (Sipuleucel-T), there has been a surge of interest in exploiting these cells as a therapeutic option for the treatment of tumors of diverse origin. In spite of the encouraging results obtained in the clinic, many elements of DC-based vaccination strategies need to be optimized. In this context, the use of experimental cancer models can help direct efforts toward an effective vaccine design. This paper reviews recent findings in murine models regarding the antitumoral mechanisms of DC-based vaccination, covering issues related to antigen sources, the use of adjuvants and maturing agents, and the role of DC subsets and their interaction in the initiation of antitumoral immune responses. The summary of such diverse aspects will highlight advantages and drawbacks in the use of murine models, and contribute to the design of successful DC-based translational approaches for cancer treatment.

Cancer vaccines

Cancer vaccines are designed to promote tumor specific immune responses, particularly cytotoxic CD8 positive T cells that are specific to tumor antigens. The earliest vaccines, which were developed in 1994-95, tested non-mutated, shared tumor associated antigens that had been shown to be immunogenic and capable of inducing clinical responses in a minority of people with late stage cancer. Technological developments in the past few years have enabled the investigation of vaccines that target mutated antigens that are patient specific. Several platforms for cancer vaccination are being tested, including peptides, proteins, antigen presenting cells, tumor cells, and viral vectors. Standard of care treatments, such as surgery and ablation, chemotherapy, and radiotherapy, can also induce antitumor immunity, thereby having cancer vaccine effects. The monitoring of patients' immune responses at baseline and after standard of care treatment is shedding light on immune biomarkers. Combination therapies are being tested in clinical trials and are likely to be the best approach to improving patient outcomes.

Preamble to the 2015 SITC immunotherapy biomarkers taskforce

The Society for Immunotherapy of Cancer (SITC) has regularly hosted workshops and working groups focused on immunologic monitoring and immune biomarkers. Due to advances in cancer immunotherapy, including positive results from clinical trials testing new agents and combinations, emerging new technologies for measuring aspects of immunity, and novel candidate biomarkers from early phase trials, the SITC Immune Biomarkers Taskforce has reconvened to review the state of the art, identify current hurdles to further success and to make recommendations to the field. Topics being addressed by individual working groups include: (1) validation of candidate biomarkers, (2) identification of the most promising technologies, (3) testing of high throughput immune signatures and (4) investigation of the pre-treatment tumor microenvironment. Resultant recommendations will be published in JITC.

Humoral Immune Response against Nontargeted Tumor Antigens after Treatment with Sipuleucel-T and Its Association with Improved Clinical Outcome

PURPOSE

Antitumor activity of cancer immunotherapies may elicit immune responses to nontargeted (secondary) tumor antigens, or antigen spread. We evaluated humoral antigen spread after treatment with sipuleucel-T, an immunotherapy for asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC), designed to target prostatic acid phosphatase (PAP; primary antigen).

EXPERIMENTAL DESIGN

Serum samples from patients with mCRPC enrolled in the placebo-controlled phase III IMPACT study (evaluable n = 142) were used to assess humoral antigen spread after treatment with sipuleucel-T. Immunoglobulin G (IgG) responses to self-antigens (including tumor antigens) were surveyed using protein microarrays and confirmed using Luminex xMAP. IgG responses were subsequently validated in ProACT (n = 33), an independent phase II study of sipuleucel-T. Association of IgG responses with overall survival (OS) was assessed using multivariate Cox models adjusted for baseline prostate-specific antigen (PSA) and lactate dehydrogenase levels.

RESULTS

In patients from IMPACT and ProACT, levels of IgG against multiple secondary antigens, including PSA, KLK2/hK2, K-Ras, E-Ras, LGALS8/PCTA-1/galectin-8, and LGALS3/galectin-3, were elevated after treatment with sipuleucel-T (P < 0.01), but not control. IgG responses (≥ 2-fold elevation posttreatment) occurred in ≥ 25% of patients, appeared by 2 weeks after sipuleucel-T treatment, and persisted for up to 6 months. IgG responses to PSA and LGALS3 were associated with improved OS in sipuleucel-T-treated patients from IMPACT (P ≤ 0.05).

CONCLUSIONS

Sipuleucel-T induced humoral antigen spread in patients with mCRPC. IgG responses were associated with improved OS in IMPACT. The methods and results reported may identify pharmacodynamic biomarkers of clinical outcome after sipuleucel-T treatment, and help in clinical assessments of other cancer immunotherapies. See related commentary by Hellstrom and Hellstrom, p. 3581.

Phase II clinical trial of multiple peptide vaccination for advanced head and neck cancer patients revealed induction of immune responses and improved OS

PURPOSE

The peptides derived from ideal cancer-testis antigens, including LY6K, CDCA1, and IMP3 (identified using genome-wide cDNA microarray analyses), were used in immunotherapy for head and neck squamous cell cancer (HNSCC). In this trial, we analyzed the immune response to and safety and efficacy of vaccine therapy.

EXPERIMENTAL DESIGN

A total of 37 patients with advanced HNSCC were enrolled in this trial of peptide vaccine therapy, and the OS, PFS, and immunologic response were evaluated using enzyme-linked ImmunoSpot (ELISPOT) and pentamer assays. The peptides were subcutaneously administered weekly with IFA. The primary endpoints were evaluated on the basis of differences between HLA-A*2402-positive [A24(+)] patients treated with peptide vaccine therapy and -negative [A24(-)] patients treated without peptide vaccine therapy among those with advanced HNSCC.

RESULTS

Our cancer vaccine therapy was well tolerated. The OS of the A24(+) vaccinated group (n = 37) was statistically significantly longer than that of the A24(-) group (n = 18) and median survival time (MST) was 4.9 versus 3.5 months, respectively; P < 0.05. One of the patients exhibited a complete response. In the A24(+) vaccinated group, the ELISPOT assay identified LY6K-, CDCA1-, and IMP3-specific CTL responses in 85.7%, 64.3%, and 42.9% of the patients, respectively. The patients showing LY6K- and CDCA1-specific CTL responses demonstrated a longer OS than those without CTL induction. Moreover, the patients exhibiting CTL induction for multiple peptides demonstrated better clinical responses.

CONCLUSIONS

The immune response induced by this vaccine may improve the prognosis of patients with advanced HNSCC.

Immune-based therapies in pancreatic and colorectal cancers and biomarkers of responsiveness

Immune-based strategies are the most promising treatments to improve cancer disease control. Early clinical trials are ongoing to test the safety and feasibility of immune-based therapies for gastrointestinal cancers. However, to date, immunotherapy has been only an experimental option for these diseases and a better understanding of their molecular, cellular, structural and clinical dissimilarities is crucial in the generation of tailored immunotherapeutic treatments. In this review, we will summarize the key mechanisms that regulate the action of immune system in cancer and the different immune-based approaches aimed at improving disease control in patients with advanced disease. We will then move on to discussing the current immunotherapeutic approaches in two types of gastrointestinal (colo-rectal and pancreatic) cancers, whose immune microenvironment has been lately object of intense analyses and has emerged as an important determinant of clinical outcome.

Therapeutic cancer vaccines: a long and winding road to success

Harnessing the immune system to achieve therapeutic efficacy in cancer has been a milestone in immuno-oncology. Tumor-induced suppression works as an obstacle for the effectiveness of immunotherapies. Advances in our understanding of the interrelationship between cancer immunoediting and immunotherapy led to successful manipulation of anticancer immunity; this provided the platform for combining cancer vaccines with chemotherapies counteracting, to some extent, tumor-induced suppressive entities and demonstrating clinical efficacy. Targeting co-inhibitory and co-stimulatory receptors with immunostimulatory antibodies has also shown clinical promise and its combined use with vaccines is a promising new approach of immunotherapy for cancer. Recent evidence supporting vaccine administration in patients with early and less aggressive disease should be additionally placed to select the appropriate patient population and to identify earlier markers of clinical benefit and immunological parameters that correlate with survival. This review focuses on promising vaccination platforms and essential perspectives in the treatment of cancer.

Tumor-associated immune parameters for personalized patient care

The implementation of a robust technology adapted to clinical practice for the evaluation of the tumor-immune infiltrate is required to exploit its prognostic and theranostic value (Robins et al., this issue).

What have we learned from cancer immunotherapy in the last 3 years?

Until recently, most immunotherapeutic approaches used to fight cancer were ineffective, counteracted by the tumour's ability to evade immune attack. However, extensive research has improved our understanding of tumour immunology and enabled the development of novel treatments that can harness the patient's immune system and prevent immune escape. Over the last few years, through numerous clinical trials and real-world experience, we have accumulated a large amount of evidence regarding the potential for long-term survival with immunotherapy agents in various types of malignancy. The results of these studies have also highlighted a number of recurring observations with immuno-oncology agents, including their potential for clinical application across a broad patient population and for both conventional and unconventional response patterns. Furthermore, given the numerous immune checkpoints that exist and the multiple mechanisms used by tumours to escape the immune system, targeting distinct checkpoint pathways using combination approaches is an attractive therapeutic strategy with the potential to further enhance the antitumour immune response.

The role of relative lymphocyte count as a biomarker for the effect of catumaxomab on survival in malignant ascites patients: results from a phase II/III study

PURPOSE

We report the role of relative lymphocyte count (RLC) as a potential biomarker with prognostic impact for catumaxomab efficacy and overall survival (OS) based on a post hoc analysis of the pivotal phase II/III study of intraperitoneal catumaxomab treatment of malignant ascites.

EXPERIMENTAL DESIGN

The impact of treatment and RLC on OS was evaluated using multivariate Cox models. Kaplan-Meier and log-rank tests were used for group comparisons. Survival analyses were performed on the safety population [patients with paracentesis plus ≥ 1 dose of catumaxomab (n = 157) and paracentesis alone (n = 88)]. Determination of the optimal cutoff value for RLC was based on five optimality criteria.

RESULTS

OS was significantly longer with catumaxomab versus paracentesis alone (P = 0.0219). The 6-month OS rate with catumaxomab was 28.9% versus 6.7% with paracentesis alone. RLC had a positive impact on OS and was an independent prognostic factor (P < 0.0001). In patients with RLC > 13% (n = 159: catumaxomab, 100 and control, 59), catumaxomab was associated with a favorable effect on OS versus paracentesis alone (P = 0.0072), with a median/mean OS benefit of 41/131 days and an increased 6-month survival rate of 37.0% versus 5.2%, respectively. In patients with RLC ≤ 13% at screening (n = 74: catumaxomab, 50 and control, 24), the median (mean) OS difference between the catumaxomab and the control group was 3 (16) days, respectively (P = 0.2561).

CONCLUSIONS

OS was significantly improved after catumaxomab treatment in patients with malignant ascites. An RLC > 13% at baseline was a significant prognostic biomarker.

Tumor radiation therapy creates therapeutic vaccine responses to the colorectal cancer antigen GUCY2C

PURPOSE

Radiation therapy (RT) is thought to produce clinical responses in cancer patients, not only through direct toxicity to cancer cells and supporting tumor stroma cells, but also through activation of immunologic effectors. More recently, RT has potentiated the local and systemic effects of cancer immunotherapy (IT). However, combination regimens that maximize immunologic and clinical efficacy remain undefined.

METHODS AND MATERIALS

We evaluated the impact of local RT on adenoviral-mediated vaccination against the colorectal cancer antigen GUCY2C (Ad5-GUCY2C) in a murine subcutaneous tumor model using mouse CT26 colon cancer cells (CT26-GUCY2C). Immune responses were assessed by ELISpot, and clinical responses were assessed by tumor size and incidence.

RESULTS

The specific sequence of tumor-directed RT preceding Ad5-GUCY2C IT transformed inactive therapeutic Ad5-GUCY2C vaccination into a curative vaccine. GUCY2C-specific T cell responses were amplified (P<.05), tumor eradication was maximized (P<.01), and tumor volumes were minimized (P<.001) in mice whose tumors were irradiated before, compared with after, Ad5-GUCY2C vaccination. The immunologic and antitumor efficacy of Ad5-GUCY2C was amplified comparably by unfractionated (8 Gy × 1), or biologically equivalent doses of fractionated (3.5 Gy × 3), RT. The antitumor effects of sequential RT and IT (RT-IT) depended on expression of GUCY2C by tumor cells and the adenoviral vaccine vector, and tumor volumes were inversely related to the magnitude of GUCY2C-specific T cell responses. Moreover, mice cured of CT26-GUCY2C tumors by RT-IT showed long-lasting antigen-dependent protection, resisting tumors formed by GUCY2C-expressing 4T1 breast cancer cells inoculated 50 days after CT26 cells.

CONCLUSIONS

Optimal sequencing of RT and IT amplifies antigen-specific local and systemic immune responses, revealing novel acute and long-term therapeutic antitumor protection. These observations underscore the importance of modality sequence optimization before the initiation of clinical trials of RT and IT to maximize immune and antitumor responses.

Therapeutic cancer vaccines

Therapeutic cancer vaccines have the potential of being integrated in the therapy of numerous cancer types and stages. The wide spectrum of vaccine platforms and vaccine targets is reviewed along with the potential for development of vaccines to target cancer cell "stemness," the epithelial-to-mesenchymal transition (EMT) phenotype, and drug-resistant populations. Preclinical and recent clinical studies are now revealing how vaccines can optimally be used with other immune-based therapies such as checkpoint inhibitors, and so-called nonimmune-based therapeutics, radiation, hormonal therapy, and certain small molecule targeted therapies; it is now being revealed that many of these traditional therapies can lyse tumor cells in a manner as to further potentiate the host immune response, alter the phenotype of nonlysed tumor cells to render them more susceptible to T-cell lysis, and/or shift the balance of effector:regulatory cells in a manner to enhance vaccine efficacy. The importance of the tumor microenvironment, the appropriate patient population, and clinical trial endpoints is also discussed in the context of optimizing patient benefit from vaccine-mediated therapy.

CTL ELISPOT assay

Enzyme-linked immune absorbent spot (Elispot) is a quantitative method for measuring relevant parameters of T cell activation. The sensitivity of Elispot allows the detection of low-frequency antigen-specific T cells that secrete cytokines and effector molecules, such as granzyme B and perforin. Cytotoxic T cell (CTL) studies have taken advantage with this high-throughput technology by providing insights into quantity and immune kinetics. Accuracy, sensitivity, reproducibility, and robustness of Elispot resulted in a wide range of applications in research as well as in diagnostic field. Actually, CTL monitoring by Elispot is a gold standard for the evaluation of antigen-specific T cell immunity in clinical trials and vaccine candidates where the ability to detect rare antigen-specific T cells is of relevance for immune diagnostic. The most utilized Elispot assay is the interferon-gamma (IFN-γ) test, a marker for CD8(+) CTL activation, but Elispot can also be used to distinguish different subsets of activated T cells by using other cytokines such as T-helper (Th) 1-type cells (characterized by the production of IFN-γ, IL-2, IL-6, IL-12, IL-21, and TNF-α), Th2 (producing cytokines like IL-4, IL-5, IL-10, and IL-13), and Th17 (IL-17) cells. The reliability of Elispot-generated data, by the evaluation of T cell frequency recognizing individual antigen/peptide, is the core of this method currently applied widely to investigate specific immune responses in cancer, infections, allergies, and autoimmune diseases. The Elispot assay is competing with other methods measuring single-cell cytokine production, e.g., intracellular cytokine by FACS or Miltenyi cytokine secretion assay. Other types of lymphocyte frequency and function assays include limiting dilution assay (LDA), cytotoxic T cell assay (CTL), and tetramer staining. Compared with respect to sensitivity the Elispot assay is outranking other methods to define frequency of antigen-specific lymphocytes. The method described herein would like to offer helpful and clear protocols for researchers that apply Elispot. IFN-γ and perforin Elispot assays are described.

Immunologic monitoring of cancer vaccine trials using the ELISPOT assay

Cancer vaccines are designed to activate an immune response to tumor-specific or tumor-associated antigens expressed by the tumor. Cancer vaccines take many forms, including synthetic peptides, tumor cells and lysates, cell lines, and autologous antigen presenting cells like dendritic cells. The target antigens may be known, or "defined" in the vaccine, or unknown. In melanoma, more so than in other cancers, a large number of immunogenic "shared" antigens (tumor-specific or tumor-associated) have been identified. This allows for vaccination of groups of patients with the same vaccine, and also allows for testing for melanoma tumor immunity even when the vaccine does not include defined antigens. For the cancer vaccine field, the goal of a prognostic or predictive biomarker has yet to be achieved. However, the primary immunologic goal of any cancer vaccine is the induction (or amplification) of an immune response against the tumor, therefore the primary goal of immunologic monitoring in this setting, is testing for that response. In this chapter, we present standardized methodology from a central immunologic monitoring laboratory for melanoma cancer vaccine immune response assessment by the Enzyme-Linked Immunosorbant Spot (ELISPOT) assay. This assay allows for enumeration of antigen-specific cells in a plate format. We present the Interferon (IFN)-γ-producing lymphocyte assay, but the platform is easily adjusted to several cell types and several secreted molecules.

Future of cancer vaccines

Extensive research in the area of active-specific immunotherapy has led to the approval of the first therapeutic cancer vaccine sipuleucel-T (Provenge™) in 2010. Even though a major milestone for the field of cancer immunotherapy, many obstacles towards successful integration of vaccination strategies into the oncologists' armamentarium remain. This chapter discusses possible future perspectives for cancer vaccines as a treatment modality in oncology with special focus on biomarkers (response prediction and patient selection), requirements for clinical trial design, and combination therapies (standard of care and new molecular entities).Extensive research in the area of active-specific immunotherapy has led to the approval of the first therapeutic cancer vaccine sipuleucel-T (Provenge™) in 2010. Even though a major milestone for the field of cancer immunotherapy, many obstacles towards successful integration of vaccination strategies into the oncologists' armamentarium remain. This chapter discusses possible future perspectives for cancer vaccines as a treatment modality in oncology with special focus on biomarkers (response prediction and patient selection), requirements for clinical trial design, and combination therapies (standard of care and new molecular entities).

Dendritic cells in cancer immunotherapy clinical trials: are we making progress?

Dendritic cells (DC) have been tested in cancer immunotherapy clinical trials for two decades. Over this time, the methods of DC culture (or manufacture) have evolved, the approaches for antigen loading have broadened, the maturation signals have varied and different sites of administration have been tested. The post-vaccination immunologic questions asked have also varied between trials and over time. In this review, I will consider multiple aspects of DC-based vaccines tested in cancer patients, including the cell culture, antigen loading, maturation, and delivery, as well as what we have learned from testing immune responses in vaccinated patients who have benefited clinically, and those who have not measurably benefited.