Nivolumab for classical Hodgkin's lymphoma after failure of both autologous stem-cell transplantation and brentuximab vedotin: a multicentre, multicohort, single-arm phase 2 trial.

BACKGROUND: Malignant cells of classical Hodgkin's lymphoma are characterised by genetic alterations at the 9p24.1 locus, leading to overexpression of PD-1 ligands and evasion of immune surveillance. In a phase 1b study, nivolumab, a PD-1-blocking antibody, produced a high response in patients with relapsed and refractory classical Hodgkin's lymphoma, with an acceptable safety profile. We aimed to assess the clinical benefit and safety of nivolumab monotherapy in patients with classical Hodgkin's lymphoma after failure of both autologous stem-cell transplantation and brentuximab vedotin. METHODS: In this ongoing, single-arm phase 2 study, adult patients (aged ≥18 years) with recurrent classical Hodgkin's lymphoma who had failed to respond to autologous stem-cell transplantation and had either relapsed after or failed to respond to brentuximab vedotin, and with an Eastern Cooperative Oncology Group performance status score of 0 or 1, were enrolled from 34 hospitals and academic centres across Europe and North America. Patients were given nivolumab intravenously over 60 min at 3 mg/kg every 2 weeks until progression, death, unacceptable toxicity, or withdrawal from study. The primary endpoint was objective response following a prespecified minimum follow-up period of 6 months, assessed by an independent radiological review committee (IRRC). All patients who received at least one dose of nivolumab were included in the primary and safety analyses. This trial is registered with ClinicalTrials.gov, number NCT02181738. FINDINGS: Among 80 treated patients recruited between Aug 26, 2014, and Feb 20, 2015, the median number of previous therapies was four (IQR 4-7). At a median follow-up of 8·9 months (IQR 7·8-9·9), 53 (66·3%, 95% CI 54·8-76·4) of 80 patients achieved an IRRC-assessed objective response. The most common drug-related adverse events (those that occurred in ≥15% of patients) included fatigue (20 [25%] patients), infusion-related reaction (16 [20%]), and rash (13 [16%]). The most common drug-related grade 3 or 4 adverse events were neutropenia (four [5%] patients) and increased lipase concentrations (four [5%]). The most common serious adverse event (any grade) was pyrexia (three [4%] patients). Three patients died during the study; none of these deaths were judged to be treatment related. INTERPRETATION: Nivolumab resulted in frequent responses with an acceptable safety profile in patients with classical Hodgkin's lymphoma who progressed after autologous stem-cell transplantation and brentuximab vedotin. Therefore, nivolumab might be a new treatment option for a patient population with a high unmet need. Ongoing follow-up will help to assess the durability of response. FUNDING: Bristol-Myers Squibb.

Pan-Bcl-2 inhibitor, GX15-070 (obatoclax), decreases human T regulatory lymphocytes while preserving effector T lymphocytes: a rationale for its use in combination immunotherapy.

Bcl-2 inhibitors are currently being evaluated in clinical studies for treatment of patients with solid tumors and hematopoietic malignancies. In this study we explored the potential for combining the pan-Bcl-2 inhibitor GX15-070 (GX15; obatoclax) with immunotherapeutic modalities. We evaluated the in vitro effects of GX15 on human T cell subsets obtained from PBMCs in terms of activation, memory, and suppressive function. Our results indicated that in healthy-donor PBMCs, mature-activated T cells were more resistant to GX15 than early-activated T cells, and that GX15 preserved memory but not non-memory T cell populations. Furthermore, GX15 increased the apoptosis of regulatory T cells (Tregs), profoundly downregulated FOXP3 and CTLA-4 in a dose-dependent manner, and decreased their suppressive function. Treating PBMCs obtained from ovarian cancer patients with GX15 also resulted in increased CD8(+):Treg and CD4(+):Treg ratios. These results support preclinical studies in which mice vaccinated before treatment with GX15 showed the greatest reduction in metastatic lung tumors as a result of increased apoptotic resistance of mature CD8(+) T cells and decreased Treg function brought about by GX15. Taken together, these findings suggest that when a Bcl-2 inhibitor is combined with active immunotherapy in humans, such as the use of a vaccine or immune checkpoint inhibitor, immunotherapy should precede administration of the Bcl-2 inhibitor to allow T cells to become mature, and thus resistant to the cytotoxic effects of the Bcl-2 inhibitor.

Identification by digital immunohistochemistry of intratumoral changes of immune infiltrates after vaccine in the absence of modifications of PBMC immune cell subsets.

Preclinical studies have demonstrated that the combination of systemic subcutaneous (s.c.) vaccination with intratumoral (i.t.) vaccination was superior in the induction of antitumor activity vs. vaccination with either route alone. A subsequent phase I study employing i.t.-s.c. vaccination was carried out in men with locally recurrent or progressive prostate cancer. rF-PSA-TRICOM (PROSTVAC) vaccine was administered intraprostatically and rV-PSA-TRICOM followed by rF-PSA-TRICOM vaccine was administered systemically. In that study no dose limiting toxicities were observed, 19/21 patients had stable or improved prostate-specific antigen (PSA) values and tumor-infiltrating lymphocytes (TILs) increased in post- vs. pre-treatment tumor biopsies, analyzed employing conventional immunohistochemistry (IHC). In the studies reported here, 31 phenotypes of peripheral blood mononuclear cells (PBMCs) were analyzed prevaccination and postvaccination as well as the functions of PBMC regulatory T cells (Tregs) and natural killer cells. A trend was observed in decreases in serum PSA with the reduction of circulating Tregs postvaccination. Digital IHC was employed prevaccination and postvaccination to measure CD4 and CD8 TILs, as well as Treg TILs by conventional IHC. Few correlations were observed with CD4, CD8 or Treg in TILs vs. PBMCs. However, patients with lower levels of CD4 TILs prevaccination showed the greatest increases in CD4 TILs postvaccine, while Treg TILs decreased postvaccine. There was also a strong correlation between decreases in serum PSA and increases in CD8 TILs postvaccine. These studies provide additional rationale for the use of i.t.-s.c. vaccinations and demonstrate a noncoordinate expression of specific immune subsets in PBMCs vs. tumor.

Distinct effects of saracatinib on memory CD8+ T cell differentiation.

Immunologic memory involving CD8(+) T cells is a hallmark of an adaptive Ag-specific immune response and constitutes a critical component of protective immunity. Designing approaches that enhance long-term T cell memory would, for the most part, fortify vaccines and enhance host protection against infectious diseases and, perhaps, cancer immunotherapy. A better understanding of the cellular programs involved in the Ag-specific T cell response has led to new approaches that target the magnitude and quality of the memory T cell response. In this article, we show that T cells from TCR transgenic mice for the nucleoprotein of influenza virus NP68 exhibit the distinct phases--priming, expansion, contraction, and memory--of an Ag-specific T cell response when exposed in vitro to the cognate peptide. Saracatinib, a specific inhibitor of Src family kinases, administered at low doses during the expansion or contraction phases, increased CD62L(high)/CD44(high) central memory CD8(+) T cells and IFN-γ production but suppressed immunity when added during the priming phase. These effects by saracatinib were not accompanied by the expected decline of Src family kinases but were accompanied by Akt-mammalian target of rapamycin suppression and/or mediated via another pathway. Increased central memory cells by saracatinib were recapitulated in mice using a poxvirus-based influenza vaccine, thus underscoring the importance of dose and timing of the inhibitor in the context of memory T cell differentiation. Finally, vaccine plus saracatinib treatment showed better protection against tumor challenge. The immune-potentiating effects on CD8(+) T cells by a low dose of saracatinib might afford better protection from pathogens or cancer when combined with vaccine.

Chemotherapy-induced immunogenic modulation of tumor cells enhances killing by cytotoxic T lymphocytes and is distinct from immunogenic cell death.

Certain chemotherapeutic regimens trigger cancer cell death while inducing dendritic cell maturation and subsequent immune responses. However, chemotherapy-induced immunogenic cell death (ICD) has thus far been restricted to select agents. In contrast, several chemotherapeutic drugs modulate antitumor immune responses, despite not inducing classic ICD. In addition, in many cases tumor cells do not die after treatment. Here, using docetaxel, one of the most widely used cancer chemotherapeutic agents, as a model, we examined phenotypic and functional consequences of tumor cells that do not die from ICD. Docetaxel treatment of tumor cells did not induce ATP or high-mobility group box 1 (HMGB1) secretion, or cell death. However, calreticulin (CRT) exposure was observed in all cell lines examined after chemotherapy treatment. Killing by carcinoembryonic antigen (CEA), MUC-1, or PSA-specific CD8(+) CTLs was significantly enhanced after docetaxel treatment. This killing was associated with increases in components of antigen-processing machinery, and mediated largely by CRT membrane translocation, as determined by functional knockdown of CRT, PERK, or CRT-blocking peptide. A docetaxel-resistant cell line was selected (MDR-1(+), CD133(+)) by continuous exposure to docetaxel. These cells, while resistant to direct cytostatic effects of docetaxel, were not resistant to the chemomodulatory effects that resulted in enhancement of CTL killing. Here, we provide an operational definition of "immunogenic modulation," where exposure of tumor cells to nonlethal/sublethal doses of chemotherapy alters tumor phenotype to render the tumor more sensitive to CTL killing. These observations are distinct and complementary to ICD and highlight a mechanism whereby chemotherapy can be used in combination with immunotherapy.

Consequence of dose scheduling of sunitinib on host immune response elements and vaccine combination therapy.

Our study investigated the immunomodulatory effects of sunitinib to rationally design combinational platforms with immunotherapies for the treatment of solid tumors. Using a mouse model, we studied the effects of sunitinib given for 4 weeks at concentrations comparable to 37.5-50 mg/day in humans, followed by 2 weeks off the drug (sunitinib 4/2). We assessed the effect of differently timed combinations of sunitinib and a poxvirus-based vaccine encoding carcinoembryonic antigen (CEA) plus 3 costimulatory molecules on immune responses in CEA-transgenic (CEA-Tg) mice. Antitumor studies were performed in CEA-Tg mice bearing CEA-transfected MC38 murine colon carcinomas (MC38-CEA), treated either concurrently or sequentially with sunitinib and vaccine. In vitro, sunitinib inhibited PDGFR phosphorylation on MC38-CEA cells at concentrations similar to those biologically available during human treatment. In vivo, one cycle of sunitinib 4/2 caused bimodal immune effects: (a) decreased regulatory cells during the 4 weeks of treatment and (b) an immune-suppression rebound during the 2 weeks of treatment interruption. In a model using CEA-Tg mice bearing CEA(+) tumors, continuous sunitinib followed by vaccine increased intratumoral infiltration of antigen-specific T lymphocytes, decreased immunosuppressant T regulatory cells and myeloid-derived suppressor cells, reduced tumor volumes and increased survival. The immunomodulatory activity of continuous sunitinib administration can create a more immune-permissive environment. In combination with immunotherapies, sunitinib treatment should precede vaccine, to precondition the immune system, to maximize the response to vaccine-mediated immune enhancement.

Effect of a small molecule BCL-2 inhibitor on immune function and use with a recombinant vaccine.

Small molecule BCL-2 inhibitors are being examined as monotherapy in phase I/II clinical trials for several types of tumors. However, few data are available about the effect of BCL-2 inhibitors on immune function. The aims of our study were to investigate the effect of a small molecule BCL-2 inhibitor on immune function and determine the most effective way of combining this inhibitor with a recombinant vaccine to treat tumors. The in vitro effect of the pan-BCL-2 inhibitor GX15-070 was assessed in mouse CD8 T lymphocytes at 2 different stages of activation as well as regulatory T lymphocytes (Treg). The in vivo effect of GX15-070 after recombinant vaccinia/fowlpox CEA-TRICOM vaccination was analyzed in tumor-infiltrating lymphocytes, and in splenocytes of mice bearing subcutaneous tumors. The therapeutic efficacy of such sequential therapy was measured as a reduction of pulmonary tumor nodules. Activated mature CD8 T lymphocytes were more resistant to GX15-070 as compared to early-activated cells. Treg function was significantly decreased after treatment with the BCL-2 inhibitor. In vivo, GX15-070 was given after vaccination so as to not negatively impact the induction of vaccine-mediated immunity, resulting in increased intratumoral activated CD8:Treg ratio and significant reduction of pulmonary tumor nodules. Our study is the first to show the effect of a small molecule BCL-2 inhibitor on the immune system and following a vaccine. It is also the first to demonstrate the efficacy of this sequence in reducing tumors in mouse models, providing a rationale for the design of combinational clinical studies.

TGF-beta modulates the functionality of tumor-infiltrating CD8+ T cells through effects on TCR signaling and Spred1 expression.

This study demonstrates that CD8+ T cells in the tumor microenvironment display reduced functionality and hyporesponsiveness. TGF-beta contributed markedly to the tumor-infiltrating CD8+ T cells' (TILs) reduced functionality, which could be reversed using a small molecule TGF-beta inhibitor. Upon T-cell receptor (TCR) activation, the activation of ITK and ERK kinases were reduced in CD8+ TILs, as compared to splenic CD8+ T cells: TGF-beta inhibitor could reverse this phenomenon. This study demonstrates for the first time the association of the Spred-1 gene, an inhibitor of the Ras/MAPK pathway, with CD8+ TILs and TGF-beta activity. Spred-1 was upregulated in CD8+ TILs and TGF-beta enhanced the expression of Spred-1 in effector/memory CD8+ T cells and not in rested/memory CD8+ T cells. Based on these findings, this study supports the hypothesis that TGF-beta mediates an inhibitory mechanism on CD8+ TILs involving TCR-signaling blockade and the upregulation of Spred-1, thus implicating Spred-1 as a potential new target for future anti-tumor immune studies.

Nivolumab for Relapsed/Refractory Classic Hodgkin Lymphoma After Failure of Autologous Hematopoietic Cell Transplantation: Extended Follow-Up of the Multicohort Single-Arm Phase II CheckMate 205 Trial.

Purpose Genetic alterations causing overexpression of programmed death-1 ligands are near universal in classic Hodgkin lymphoma (cHL). Nivolumab, a programmed death-1 checkpoint inhibitor, demonstrated efficacy in relapsed/refractory cHL after autologous hematopoietic cell transplantation (auto-HCT) in initial analyses of one of three cohorts from the CheckMate 205 study of nivolumab for cHL. Here, we assess safety and efficacy after extended follow-up of all three cohorts. Methods This multicenter, single-arm, phase II study enrolled patients with relapsed/refractory cHL after auto-HCT treatment failure into cohorts by treatment history: brentuximab vedotin (BV)-naïve (cohort A), BV received after auto-HCT (cohort B), and BV received before and/or after auto-HCT (cohort C). All patients received nivolumab 3 mg/kg every 2 weeks until disease progression/unacceptable toxicity. The primary end point was objective response rate per independent radiology review committee. Results Overall, 243 patients were treated; 63 in cohort A, 80 in cohort B, and 100 in cohort C. After a median follow-up of 18 months, 40% continued to receive treatment. The objective response rate was 69% (95% CI, 63% to 75%) overall and 65% to 73% in each cohort. Overall, the median duration of response was 16.6 months (95% CI, 13.2 to 20.3 months), and median progression-free survival was 14.7 months (95% CI, 11.3 to 18.5 months). Of 70 patients treated past conventional disease progression, 61% of those evaluable had stable or further reduced target tumor burdens. The most common grade 3 to 4 drug-related adverse events were lipase increases (5%), neutropenia (3%), and ALT increases (3%). Twenty-nine deaths occurred; none were considered treatment related. Conclusion With extended follow-up, responses to nivolumab were frequent and durable. Nivolumab seems to be associated with a favorable safety profile and long-term benefits across a broad spectrum of patients with relapsed/refractory cHL.

Major Histocompatibility Complex Class II and Programmed Death Ligand 1 Expression Predict Outcome After Programmed Death 1 Blockade in Classic Hodgkin Lymphoma.

Purpose Hodgkin Reed-Sternberg (HRS) cells evade antitumor immunity by multiple means, including gains of 9p24.1/ CD274(PD-L1)/ PDCD1LG2(PD-L2) and perturbed antigen presentation. Programmed death 1 (PD-1) receptor blockade is active in classic Hodgkin lymphoma (cHL) despite reported deficiencies of major histocompatibility complex (MHC) class I expression on HRS cells. Herein, we assess bases of sensitivity to PD-1 blockade in patients with relapsed/refractory cHL who were treated with nivolumab (anti-PD-1) in the CheckMate 205 trial. Methods HRS cells from archival tumor biopsies were evaluated for 9p24.1 alterations by fluorescence in situ hybridization and for expression of PD ligand 1 (PD-L1) and the antigen presentation pathway components-ß2-microglobulin, MHC class I, and MHC class II-by immunohistochemistry. These parameters were correlated with clinical responses and progression-free survival (PFS) after PD-1 blockade. Results Patients with higher-level 9p24.1 copy gain and increased PD-L1 expression on HRS cells had superior PFS. HRS cell expression of ß2-microglobulin/MHC class I was not predictive for complete remission or PFS after nivolumab therapy. In contrast, HRS cell expression of MHC class II was predictive for complete remission. In patients with a > 12-month interval between myeloablative autologous stem-cell transplantation and nivolumab therapy, HRS cell expression of MHC class II was associated with prolonged PFS. Conclusion Genetically driven PD-L1 expression and MHC class II positivity on HRS cells are potential predictors of favorable outcome after PD-1 blockade. In cHL, clinical responses to nivolumab were not dependent on HRS cell expression of MHC class I.

Analyses of Pretherapy Peripheral Immunoscore and Response to Vaccine Therapy.

Tumor immunoscore analyses, especially for primary colorectal cancer and melanoma lesions, provide valuable prognostic information. Metastatic lesions of many carcinoma types, however, are often not easily accessible. We hypothesized that immune cells in peripheral blood may differ among individual patients with metastatic disease, which, in turn, may influence their response to immunotherapy. We thus analyzed immune cell subsets within peripheral blood mononuclear cells to determine if a "peripheral immunoscore" could have any prognostic significance for patients before receiving immunotherapy. Patients with metastatic breast cancer were randomly assigned to receive docetaxel ± PANVAC vaccine. In another trial, prostate cancer patients with metastatic bone lesions were randomly assigned to receive a bone-seeking radionuclide ± PROSTVAC vaccine. Predefined analyses of "classic" immune cell types (CD4, CD8, natural killer cells, regulatory T cells, myeloid-derived suppressor cells, and ratios) revealed no differences in progression-free survival (PFS) for either arm in both trials. Predefined analyses of refined immune cell subsets for which a biologic function had been previously reported also showed no significant prognostic value in PFS for patients receiving either docetaxel or radionuclide alone; however, in patients receiving these agents in combination with vaccine, the peripheral immunoscore of refined subsets revealed statistically significant differences in PFS (P < 0.001) for breast cancer patients receiving docetaxel plus vaccine, and in prostate cancer patients receiving radionuclide plus vaccine (P = 0.004). Larger randomized studies will be required to validate these findings. These studies, however, provide the rationale for the evaluation of refined immune cell subsets to help determine which patients may benefit most from immunotherapy. Cancer Immunol Res; 4(9); 755-65. ©2016 AACR.

Inhibition of the angiopoietin/Tie2 axis induces immunogenic modulation, which sensitizes human tumor cells to immune attack.

BACKGROUND: The angiopoietin/Tie2 pathway is an attractive target for cancer therapy due to its well-known role in regulating angiogenesis. Trebananib, a recombinant peptide-Fc fusion protein, or peptibody, that binds to angiopoietin-1 (Ang1) and Ang2 to block their interaction with the Tie2 receptor, is under active clinical investigation. We investigated whether suppressing the angiopoietin/Tie2 pathway, using the preclinical version of Trebananib (mL4-3 and L1-7(N)), could increase the sensitivity of human tumor cells to immune-mediated lysis through immunogenic modulation, which would make Trebananib a promising candidate for combination with immunotherapy. METHODS: We assessed human carcinoma cells for expression and activation of Ang1 and Ang2 and their receptor tyrosine kinase Tie2. In vitro, we exposed tumor cell lines expressing Tie2 to the peptibodies mL4-3 and L1-7(N), which inhibit the binding of Ang1 and Ang2 to Tie2, and assessed the cells for changes in viability, proliferation, surface phenotype, and sensitivity to attack by antigen-specific cytotoxic T lymphocytes (CTLs). RESULTS: Suppression of the angiopoietin/Tie2 pathway using mL4-3 and L1-7(N) had no effect on the proliferation or viability of tumor cells. However, these inhibitors markedly altered tumor cell phenotype, rendering tumor cells significantly more sensitive to antigen-specific CTL killing. ICAM-1 was shown to be mechanistically involved in these inhibitors' ability to sensitize tumor cells to immune-mediated attack by functional blocking studies. CONCLUSION: Our findings provide a rationale for the combination of agents targeting the angiopoietin/Tie2 pathway with cancer immunotherapies.

Docetaxel Alone or in Combination With a Therapeutic Cancer Vaccine (PANVAC) in Patients With Metastatic Breast Cancer: A Randomized Clinical Trial.

IMPORTANCE: Previous phase 1 and 2 trials of PANVAC, a poxviral-based cancer vaccine, have suggested clinical efficacy in some patients with breast, ovarian, and colorectal cancer and have shown evidence of immunologic activity. Preclinical data have shown that docetaxel can modify tumor phenotype, making tumor cells more amenable to T cell-mediated killing. OBJECTIVE: The goal of this study was to determine if the treatment combination of docetaxel and PANVAC improves clinical outcomes in patients with metastatic breast cancer compared with docetaxel treatment alone. DESIGN, SETTING, AND PARTICIPANTS: Between May 2006 and February 2012, this open-label, phase 2 randomized clinical trial enrolled 48 patients with metastatic breast cancer of all subtypes, without limitation on other lines of previous therapy, to receive treatment with either docetaxel with PANVAC (arm A) or docetaxel alone (arm B). Final clinical data were collected on September 16, 2013. All patients were treated at either the National Cancer Institute or the Department of Breast Medical Oncology, MD Anderson Cancer Center. MAIN OUTCOMES AND MEASURES: The primary end point was progression-free survival (PFS), using a phase 2.5 statistical design, with the intent of identifying a trend toward benefit (defined as 1-sided P≤.10) to guide a larger trial design. Secondary end points included safety and immunologic correlative studies. RESULTS: Forty-eight participants were enrolled: 25 were randomized to the combination treatment arm A, and 23 to arm B. No patient remained in the study at the time of the final analysis. Patient and tumor characteristics were well matched. Analysis of adverse events in both treatment arms demonstrated very little difference between the 2 groups. In the combination treatment arm (arm A), statistically significant increases were noted in the frequency of grades 1 and 2 edema (P=.02, likely related to greater median number of docetaxel cycles) and injection-site reactions (P<.001). In the final data analysis, median PFS was 7.9 months in arm A vs 3.9 months in arm B (hazard ratio, 0.65 [95% CI, 0.34-1.14]; P=.09). CONCLUSIONS AND RELEVANCE: The results suggest that the combination of PANVAC with docetaxel in metastatic breast cancer may provide a clinical benefit. This study was hypothesis generating and provides both rationale and statistical assumptions for a larger definitive randomized study. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00179309.

Immune consequences of decreasing tumor vasculature with antiangiogenic tyrosine kinase inhibitors in combination with therapeutic vaccines.

This study investigated the effects on the tumor microenvironment (TME) of combining antiangiogenic tyrosine kinase inhibitors (TKI) with therapeutic vaccines, and in particular, how vascular changes affect tumor-infiltrating immune cells. We conducted studies using a TKI (sunitinib or sorafenib) in combination with recombinant vaccines in two murine tumor models: colon carcinoma (MC38-CEA) and breast cancer (4T1). Tumor vasculature was measured by immunohistochemistry using three endothelial cell markers: CD31 (mature), CD105 (immature/proliferating), and CD11b (monocytic). We assessed oxygenation, tight junctions, compactness, and pressure within tumors, along with the frequency and phenotype of tumor-infiltrating lymphocytes (TIL), myeloid-derived suppressor cells (MDSC), and tumor-associated macrophages (TAM) following treatment with antiangiogenic TKIs alone, vaccine alone, or the combination of a TKI with vaccine. The combined regimen decreased tumor vasculature, compactness, tight junctions, and pressure, leading to vascular normalization and increased tumor oxygenation. This combination therapy also increased TILs, including tumor antigen-specific CD8 T cells, and elevated the expression of activation markers FAS-L, CXCL-9, CD31, and CD105 in MDSCs and TAMs, leading to reduced tumor volumes and an increase in the number of tumor-free animals. The improved antitumor activity induced by combining antiangiogenic TKIs with vaccine may be the result of activated lymphoid and myeloid cells in the TME, resulting from vascular normalization, decreased tumor-cell density, and the consequent improvement in vascular perfusion and oxygenation. Therapies that alter tumor architecture can, thus, have a dramatic impact on the effectiveness of cancer immunotherapy.

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.

Immune impact induced by PROSTVAC (PSA-TRICOM), a therapeutic vaccine for prostate cancer.

PSA-TRICOM (PROSTVAC) is a novel vector-based vaccine designed to generate a robust immune response against prostate-specific antigen (PSA)-expressing tumor cells. The purpose of this report is to present an overview of both published studies and new data in the evaluation of immune responses to the PSA-TRICOM vaccine platform, currently in phase III testing. Of 104 patients tested for T-cell responses, 57% (59/104) demonstrated a ≥ 2-fold increase in PSA-specific T cells 4 weeks after vaccine (median 5-fold increase) compared with pre-vaccine, and 68% (19/28) of patients tested mounted post-vaccine immune responses to tumor-associated antigens not present in the vaccine (antigen spreading). The PSA-specific immune responses observed 28 days after vaccine (i.e., likely memory cells) are quantitatively similar to the levels of circulating T cells specific for influenza seen in the same patients. Measurements of systemic immune response to PSA may underestimate the true therapeutic immune response (as this does not account for cells that have trafficked to the tumor) and does not include antigen spreading. Furthermore, although the entire PSA gene is the vaccine, only one epitope of PSA is evaluated in the T-cell responses. Because this therapeutic vaccine is directed at generating a cellular/Th1 immune response (T-cell costimulatory molecules and use of a viral vector), it is not surprising that less than 0.6% of patients (2/349) tested have evidence of PSA antibody induction following vaccine. This suggests that post-vaccine PSA kinetics were not affected by PSA antibodies. An ongoing phase III study will evaluate the systemic immune responses and correlation with clinical outcomes.

Combination therapy with a second-generation androgen receptor antagonist and a metastasis vaccine improves survival in a spontaneous prostate cancer model.

PURPOSE: Enzalutamide, a second-generation androgen antagonist, was approved by the U.S. Food and Drug Administration (FDA) for castration-resistant prostate cancer (CRPC) treatment. Immunotherapy has been shown to be a promising strategy for prostate cancer. This study was performed to provide data to support the combination of enzalutamide and immunotherapy for CRPC treatment. EXPERIMENTAL DESIGN: Male C57BL/6 or TRAMP (transgenic adenocarcinoma of the mouse prostate) prostate cancer model mice were exposed to enzalutamide and/or a therapeutic vaccine targeting Twist, an antigen involved in epithelial-to-mesenchymal transition and metastasis. The physiologic and immunologic effects of enzalutamide were characterized. The generation of Twist-specific immunity by Twist-vaccine was assessed. Finally, the combination of enzalutamide and Twist-vaccine to improve TRAMP mice overall survival was evaluated. RESULTS: Enzalutamide mediated immunogenic modulation in TRAMP-C2 cells. In vivo, enzalutamide mediated reduced genitourinary tissue weight, enlargement of the thymus, and increased levels of T-cell excision circles. Because no changes were seen in T-cell function, as determined by CD4(+) T-cell proliferation and regulatory T cell (Treg) functional assays, enzalutamide was determined to be immune inert. Enzalutamide did not diminish the ability of Twist-vaccine to generate Twist-specific immunity. Twist was confirmed as a valid tumor antigen in TRAMP mice by immunohistochemistry. The combination of enzalutamide and Twist-vaccine resulted in significantly increased overall survival of TRAMP mice compared with other treatment groups (27.5 vs. 10.3 weeks). Notably, the effectiveness of the combination therapy increased with disease stage, i.e., the greatest survival benefit was seen in mice with advanced-stage prostate tumors. CONCLUSIONS: These data support the combination of enzalutamide and immunotherapy as a promising treatment strategy for CRPC. Clin Cancer Res; 19(22); 6205-18. ©2013 AACR.

Effects of conventional therapeutic interventions on the number and function of regulatory T cells.

Several lines of investigation have revealed the apparent interplay between the immune system of the host and many conventional, "standard-of-care" anticancer therapies, including chemotherapy and small molecule targeted therapeutics. In particular, preclinical and clinical studies have demonstrated the important role of regulatory T cells (Tregs) in inhibiting immune responses elicited by immunotherapeutic regimens such as those based on anticancer vaccines or checkpoint inhibitors. However, how the number and immunosuppressive function of Tregs change in cancer patients undergoing treatment with non-immune anticancer therapies remains to be precisely elucidated. To determine whether immunostimulatory therapies can be employed successfully in combination with conventional anticancer regimens, we have investigated both the number and function of Tregs obtained from the peripheral blood of carcinoma patients before the initiation and during the course of chemotherapeutic and targeted agent regimens. Our studies show that the treatment of breast cancer patients with tamoxifen plus leuprolide, a gonadotropin releasing hormone agonist, has minimal effects on Tregs, while sunitinib appears to exert differential effects on Tregs among patients with metastatic renal carcinoma. However, the administration of docetaxel to patients with metastatic prostate or breast cancer, as well as that of cisplatin plus vinorelbine to non-small cell lung cancer patients, appears to significantly increase the ratio between effector T cells and Tregs and to reduce the immunosuppressive activity of the latter in the majority of patients. These studies provide the rationale for the selective use of active immunotherapy regimens in combination with specific standard-of-care therapies to achieve the most beneficial clinical outcome among carcinoma patients.

The tipping point for combination therapy: cancer vaccines with radiation, chemotherapy, or targeted small molecule inhibitors.

Therapeutic cancer vaccines are a unique treatment modality in that they initiate a dynamic process of activating the host immune system, which can then be exploited by concurrent or subsequent therapies. The addition of immunotherapy to standard-of-care cancer therapies has shown evidence of efficacy in preclinical models and in the clinical setting. This review examines the preclinical and clinical interactions between vaccine-mediated tumor-specific immune responses and local radiation, systemic chemotherapy, or select small molecule inhibitors, as well as the potential synergy between these modalities.