Antigen-4 Blockade Research Articles

A review of recent advances in the novel therapeutic targets and immunotherapy for lung cancer

Lung cancer is amongst the most pervasive malignancies having high mortality rates. It is broadly grouped into non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). The concept of personalized medicine has overshadowed the conventional chemotherapy given to all patients with lung cancer. The targeted therapy is given to a particular population having specific mutations to help in the better management of lung cancer. The targeting pathways for NSCLC include the epidermal growth factor receptor, vascular endothelial growth factor receptor, MET (Mesenchymal epithelial transition factor) oncogene, Kirsten rat sarcoma viral oncogene(KRAS), and anaplastic lymphoma kinase (ALK). SCLC targeting pathway includes Poly (ADP-ribose) polymerases (PARP) inhibitors, checkpoint kinase 1 (CHK 1) pathway, WEE1 pathway, Ataxia Telangiectasia and Rad3-related (ATR)/Ataxia telangiectasia mutated (ATM), and Delta-like canonical Notch ligand 3 (DLL-Immune checkpoint inhibitors like programmed cell death protein 1 (PD-1)/ programmed death-ligand 1 (PD-L1) inhibitors and Cytotoxic T-lymphocyte-associated antigen-4 (CTLA4) blockade are also utilized in the management of lung cancer. Many of the targeted therapies are still under development and require clinical trials to establish their safety and efficacy. This review summarizes the mechanism of molecular targets and immune-mediated targets, recently approved drugs, and their clinical trials for lung cancer.

Roles of Polymorphonuclear Neutrophils in Ischemic Brain Injury and Post-Ischemic Brain Remodeling.

Following ischemic stroke, polymorphonuclear neutrophils (PMNs) are rapidly recruited to the ischemic brain tissue and exacerbate stroke injury by release of reactive oxygen species (ROS), proteases and proinflammatory cytokines. PMNs may aggravate post-ischemic microvascular injury by obstruction of brain capillaries, contributing to reperfusion deficits in the stroke recovery phase. Thus, experimental studies which specifically depleted PMNs by delivery of anti-Ly6G antibodies or inhibited PMN brain entry, e.g., by CXC chemokine receptor 2 (CXCR2) or very late antigen-4 (VLA-4) blockade in the acute stroke phase consistently reduced neurological deficits and infarct volume. Although elevated PMN responses in peripheral blood are similarly predictive for large infarcts and poor stroke outcome in human stroke patients, randomized controlled clinical studies targeting PMN brain infiltration did not improve stroke outcome or even worsened outcome due to serious complications. More recent studies showed that PMNs have decisive roles in post-ischemic angiogenesis and brain remodeling, most likely by promoting extracellular matrix degradation, thereby amplifying recovery processes in the ischemic brain. In this minireview, recent findings regarding the roles of PMNs in ischemic brain injury and post-ischemic brain remodeling are summarized.

Case report: Minimal change disease and acute interstitial nephritis in a patient with Hodgkin’s lymphoma treated with nivolumab

Programmed cell death receptor-1 blocking antibodies and cytotoxic T-lymphocyte–associated antigen-4 blocking antibodies are referred to as checkpoint inhibitors and are used in cancer immunotherapy. While enhancing T-cell antitumor immunity, checkpoint inhibitors can also cause immune-mediated nephrotoxicities, manifesting mostly in acute kidney injury. Cytotoxic T-lymphocyte–associated antigen-4 blockade was associated with acute interstitial nephritis with variable degrees of podocyte effacement, minimal change disease, and membranous nephropathy. Conversely, programmed cell death receptor-1 blockade has mostly been associated with acute interstitial nephritis, with or without various glomerular diseases. In particular, cases of minimal change disease were reported with programmed cell death receptor-1 blockade, including two cases of minimal change disease reported in Hodgkin’s lymphoma and one with mesothelioma, in addition to one case of focal segmental glomerulosclerosis after treatment of renal cell carcinoma. We report a case of acute interstitial nephritis and minimal change disease in a patient with Hodgkin’s lymphoma treated with nivolumab and discuss pathophysiological hypotheses. The association of minimal change disease with Hodgkin’s lymphoma is well-recognized and may be related to c-mip protein and/or CD80. The checkpoint pathway likely triggers the auto-immune, T-cell-mediated, minimal change disease associated with Hodgkin’s lymphoma; however, this pathogenic process may also involve a programmed cell death receptor-1– fyn-c-mip interaction or a PD-L1–CD80 cross-talk at both T-cell and podocyte level.

Comparative efficacy and safety of combination therapies for advanced melanoma: a network meta-analysis

BackgroundCurrently, the major treatment modalities of advanced melanoma are immune check point and mitogen-activated protein kinase (MAPK) pathway inhibitors. As lacking head-to-head randomizedcontrolled trials (RCTs) comparing immune check point and MAPK pathway inhibitors, we evaluated the efficacy and toxicity with different treatment combinations of immune check point or MAPK pathway inhibitors for advanced melanoma by network meta-analysis.MethodsWe searched for RCTs in Pubmed, Embase, Ovid MEDLINE, Web of Science and Cochrane Central Register for Controlled Trials through March 2017. Two reviewers performed a network meta-analysis by assessing the hazard ratios (HRs) for overall survival (OS) and progression-free survival (PFS), as well as by evaluating serious adverse events (SAEs).ResultsTwenty-four eligible RCTs involving 10,951 patients assigned to 11 treatment modalities were included. The combination of BRAF and MEK inhibitors demonstrated an improved OS benefit compared with all the other treatments except programmed death-1/ligand-1 (PD-1/L1) blockade because the difference in OS between the BRAF-MEK inhibitor combination and PD-1 blockade (HR: 0.85; 95% credible interval (CrI): 0.59, 1.21) was not significant. For PFS, the BRAF and MEK inhibitor combination showed a significant advantage compared with other treatments apart from the combination of PD-1/L1 and cytotoxic T lymphocyte-associated antigen-4(CTLA-4) blockade (HR:0.61; 95% CrI: 0.30, 1.25). The MEK inhibitor combined with chemotherapy was associated with the highest risk of SAEs (HR: 1.76 95% CrI: 1.21, 2.48).ConclusionsThe combination of BRAF and MEK inhibitors exhibited a survival advantage in OS and PFS and comparable risk of toxicity compared with chemotherapy.

Effectiveness and safety of PD-1/PD-L1 or CTLA4 inhibitors combined with chemotherapy as a first-line treatment for lung cancer: A meta-analysis.

Immune checkpoint inhibitors (ICIs) combined with chemotherapy have been applied as a first-line treatment for lung cancer, but consistent beneficial results have not been documented. Therefore, our meta-analysis aimed to evaluate the effectiveness and safety of combination therapy to promote its application. We searched electronic databases for studies that estimated the safety and efficacy of combined therapy. The objective response rate (ORR) and disease control response (DCR) parameters were evaluated with odds ratio (OR) values of the combination arm over the non-combination arm. Hazard ratios (HR) and its 95% confidence intervals (95% CI) were used to calculate progression-free survival (PFS) and overall survival (OS) in the combination and non-combination arms. All treatment-related adverse events (TRAEs) and 3 to 5 TRAEs were expressed as relative risk (RR) values of the combination arm over the non-combination arm. Ten eligible studies involving 4,887 patients were identified. The pooled ORs for ORR and DCR were 1.85 (95% CI: 1.30-2.63, P<0.01) and 1.14 (95% CI: 0.70-1.86, P<0.01), respectively. The pooled HRs for PFS and OS were 0.67 (95% CI: 0.58-0.79, P<0.001) and 0.76 (95% CI: 0.65-0.88, P<0.001), respectively. In subgroup analysis, ORR and DCR were significantly improved in the programmed cell death-1/L1 (PD-1/L1) blockade for non-small cell lung cancer (NSCLC) group (subgroup A), with a combined OR values of 2.36 (95% CI: 1.79-3.13, P<0.001) and 1.92 (95% CI: 1.10-3.35, P<0.001), respectively. However, no significant benefits were observed in the cytotoxic T lymphocyte antigen-4 (CTLA-4) blockade for small cell lung cancer (SCLC) (subgroup B) and CTLA-4 blockade for NSCLC groups (subgroup C). In addition, a significant improvement in PFS was observed in subgroup A, subgroup B and subgroup C, with pooled HR values of 0.58 (95% CI: 0.52-0.63, P<0.001), 0.86 (95% CI: 0.76-0.97, P<0.05) and 0.83 (95% CI: 0.68-1.00, P<0.05), respectively. Only subgroup A exhibited an OS benefit, with a combined HR value of 0.67 (95% CI: 0.55-0.81, P<0.001). Moreover, as the expression of PD-L1 increased, the PFS and OS benefits were more significantly. Furthermore, patients without central nervous system (CNS) metastasis who were treated with PD-1/L1 inhibitors had a longer OS than patients with CNS metastasis (HR: 0.67, 95% CI: 0.55-0.80, P<0.001). Finally, combined therapy was associated with 3 to 5 TRAEs (RR: 1.26, 95% CI: 1.08-1.47; P<0.01). Patients treated with immunotherapy and chemotherapy in combination exhibited superior in ORR, DCR, PFS and OS as well as slightly increased TRAE levels compared with those of patients treated with either monotherapy.

Peritransplant VLA-4 blockade inhibits endogenous memory CD8 T cell infiltration into high-risk cardiac allografts and CTLA-4Ig resistant rejection.

Recipient endogenous memory CD8 T cells expressing reactivity to donor class I MHC infiltrate MHC-mismatched cardiac allografts within 24hours after reperfusion and express effector functions mediating graft injury. The current study tested the efficacy of Very Late Antigen-4 (VLA-4) blockade to inhibit endogenous memory CD8 T cell infiltration into cardiac allografts and attenuate early posttransplant inflammation. Peritransplant anti-VLA-4 mAb given to C57BL6 (H-2b ) recipients of AJ (H-2a ) heart allografts completely inhibited endogenous memory CD4 and CD8 T cell infiltration with significant decrease in macrophage, but not neutrophil, infiltration into allografts subjected to either minimal or prolonged cold ischemic storage (CIS) prior to transplant, reduced intra-allograft IFN-γ-induced gene expression and prolonged survival of allografts subjected to prolonged CIS in CTLA-4Ig treated recipients. Anti-VLA-4 mAb also inhibited priming of donor-specific T cells producing IFN-γ until at least day 7 posttransplant. Peritransplant anti-VLA plus anti-CD154 mAb treatment similarly prolonged survival of allografts subjected to minimal or increased CIS prior to transplant. Overall, these data indicate that peritransplant anti-VLA-4 mAb inhibits early infiltration memory CD8 T cell infiltration into allografts with a marked reduction in early graft inflammation suggesting an effective strategy to attenuate negative effects of heterologous alloimmunity in recipients of higher risk grafts.

PPARγ Contributes to Immunity Induced by Cancer Cell Vaccines That Secrete GM-CSF.

Peroxisome proliferator activated receptor-γ (PPARγ) is a lipid-activated nuclear receptor that promotes immune tolerance through effects on macrophages, dendritic cells (DCs), and regulatory T cells (Tregs). Granulocyte-macrophage colony stimulating factor (GM-CSF) induces PPARγ expression in multiple myeloid cell types. GM-CSF contributes to both immune tolerance and protection, but the role of PPARγ in these pathways is poorly understood. Here, we reveal an unexpected stimulatory role for PPARγ in the generation of antitumor immunity with irradiated, GM-CSF-secreting tumor-cell vaccines (GVAX). Mice harboring a deletion of pparg in lysozyme M (LysM)-expressing myeloid cells (KO) showed a decreased ratio of CD8+ T effectors to Tregs and impaired tumor rejection with GVAX. Diminished tumor protection was associated with altered DC responses and increased production of the Treg attracting chemokines CCL17 and CLL22. Correspondingly, the systemic administration of PPARγ agonists to vaccinated mice elevated the CD8+ T effector to Treg ratio through effects on myeloid cells and intensified the antitumor activity of GVAX combined with cytotoxic T lymphocyte-associated antigen-4 antibody blockade. PPARγ agonists similarly attenuated Treg induction and decreased CCL17 and CCL22 levels in cultures of human peripheral blood mononuclear cells with GM-CSF-secreting tumor cells. Together, these results highlight a key role for myeloid cell PPARγ in GM-CSF-stimulated antitumor immunity and suggest that PPARγ agonists might be useful in cancer immunotherapy. Cancer Immunol Res; 6(6); 723-32. ©2018 AACR.

A CTLA-4 Antagonizing DNA Aptamer with Antitumor Effect.

The successful translation of cytotoxic T lymphocyte antigen-4 (CTLA-4) blockade has revolutionized the concept of cancer immunotherapy. Although monoclonal antibody therapeutics remain the mainstream in clinical practice, aptamers are synthetic oligonucleotides that encompass antibody-mimicking functions. Here, we report a novel high-affinity CTLA-4-antagonizing DNA aptamer (dissociation constant, 11.84 nM), aptCTLA-4, which was identified by cell-based SELEX and high-throughput sequencing. aptCTLA-4 is relatively stable in serum, promotes lymphocyte proliferation, and inhibits tumor growth in cell and animal models. Our study demonstrates the developmental pipeline of a functional CTLA-4-targeting aptamer and suggests a translational potential for aptCTLA-4.

Recent Progress in Mutation-driven Therapy, Immunotherapy and Combination Therapy for the Treatment of Melanoma.

With increases in our understanding of the human genome and immune system, the treatment armamentarium for melanoma has benefitted from the development and approval of BRAF inhibitors, MEK inhibitors, immune checkpoint modulators via cytotoxic T-lymphocyte antigen-4 blockade, and PD-1 and PD-L1 inhibitors. These advances, however, have raised questions about combination therapy, the optimal sequential use of these agents, the limited assessment of response using traditional metrics, and the optimal selection of the population to be treated. In this review we summarize recent breakthroughs and then itemize the development of newer agents, potential prognostic and predictive biomarkers, resistance mechanisms, and strategies of combination therapy. We also emphasize the multifaceted attributes of immunotherapy in terms of durable responses and longterm survival that paradoxically necessitate further research into the underlying mechanisms and longer patient follow-up.

P2.03b-090 A CTLA-4 Antagonizing DNA Aptamer with Anti-Tumor Effect: Topic: Biomarkers

The discovery of cytotoxic T lymphocyte antigen-4 (CTLA-4) blockade and its successful clinical translation has revolutionized the concept of cancer immunotherapy. Although immunecheckpoint-targeting antibody has shown impressive results in a diverse array of cancers, their cell-based manufacturing process influences production capacity and cause variation between batches. Aptamers are synthetic DNA or RNA oligonucleotides that encompass antibody-mimicking functions. With its chemically synthetic nature, aptamer can be produced in large scale with controllable batch variations and lower manufacturing cost. Here, we report the development of a CTLA-4 antagonizing DNA aptamer, termed aptCTLA-4, using the cell-based SELEX and next-generation sequencing. The aptCTLA-4 exhibits good binding affinity (dissociation constant, 11.8 nM). In vitro lymphocyte proliferation assays demonstrated that the aptCTLA-4 promotes T cell proliferation, and in vivo murine syngeneic tumor models further revealed its tumor-inhibitory effects. Our data suggest the translational potential of the aptCTLA-4 to be developed into a therapeutic aptamer.

T-Cell Therapy Using Interleukin-21-Primed Cytotoxic T-Cell Lymphocytes Combined With Cytotoxic T-Cell Lymphocyte Antigen-4 Blockade Results in Long-Term Cell Persistence and Durable Tumor Regression.

Purpose Peripheral blood-derived antigen-specific cytotoxic T cells (CTLs) provide a readily available source of effector cells that can be administered with minimal toxicity in an outpatient setting. In metastatic melanoma, this approach results in measurable albeit modest clinical responses in patients resistant to conventional therapy. We reasoned that concurrent cytotoxic T-cell lymphocyte antigen-4 (CTLA-4) checkpoint blockade might enhance the antitumor activity of adoptively transferred CTLs. Patients and Methods Autologous MART1-specific CTLs were generated by priming with peptide-pulsed dendritic cells in the presence of interleukin-21 and enriched by peptide-major histocompatibility complex multimer-guided cell sorting. This expeditiously yielded polyclonal CTL lines uniformly expressing markers associated with an enhanced survival potential. In this first-in-human strategy, 10 patients with stage IV melanoma received the MART1-specific CTLs followed by a standard course of anti-CTLA-4 (ipilimumab). Results The toxicity profile of the combined treatment was comparable to that of ipilimumab monotherapy. Evaluation of best responses at 12 weeks yielded two continuous complete remissions, one partial response (PR) using RECIST criteria (two PRs using immune-related response criteria), and three instances of stable disease. Infused CTLs persisted with frequencies up to 2.9% of CD8+ T cells for as long as the patients were monitored (up to 40 weeks). In patients who experienced complete remissions, PRs, or stable disease, the persisting CTLs acquired phenotypic and functional characteristics of long-lived memory cells. Moreover, these patients also developed responses to nontargeted tumor antigens (epitope spreading). Conclusion We demonstrate that combining antigen-specific CTLs with CTLA-4 blockade is safe and produces durable clinical responses, likely reflecting both enhanced activity of transferred cells and improved recruitment of new responses, highlighting the promise of this strategy.

Analysis of Immune Signatures in Longitudinal Tumor Samples Yields Insight into Biomarkers of Response and Mechanisms of Resistance to Immune Checkpoint Blockade.

Immune checkpoint blockade represents a major breakthrough in cancer therapy; however, responses are not universal. Genomic and immune features in pretreatment tumor biopsies have been reported to correlate with response in patients with melanoma and other cancers, but robust biomarkers have not been identified. We studied a cohort of patients with metastatic melanoma initially treated with cytotoxic T-lymphocyte-associated antigen-4 (CTLA4) blockade (n = 53) followed by programmed death-1 (PD-1) blockade at progression (n = 46), and analyzed immune signatures in longitudinal tissue samples collected at multiple time points during therapy. In this study, we demonstrate that adaptive immune signatures in tumor biopsy samples obtained early during the course of treatment are highly predictive of response to immune checkpoint blockade and also demonstrate differential effects on the tumor microenvironment induced by CTLA4 and PD-1 blockade. Importantly, potential mechanisms of therapeutic resistance to immune checkpoint blockade were also identified. These studies demonstrate that adaptive immune signatures in early on-treatment tumor biopsies are predictive of response to checkpoint blockade and yield insight into mechanisms of therapeutic resistance. These concepts have far-reaching implications in this age of precision medicine and should be explored in immune checkpoint blockade treatment across cancer types. Cancer Discov; 6(8); 827-37. ©2016 AACR.See related commentary by Teng et al., p. 818This article is highlighted in the In This Issue feature, p. 803.

Ipilimumab and Bevacizumab in Glioblastoma

The median survival in glioblastoma is just over a year, with no standard second-line therapy. Ipilimumab is an immune checkpoint inhibitor that activates the anti-tumour immune response by cytotoxic T-lymphocyte antigen-4 blockade. There is significant evidence supporting its role in the treatment of malignant melanoma, including in patients with brain metastases. The addition of the anti-angiogenesis agent, bevacizumab, seems to offer additional benefit and limit the immune-related side-effects of ipilimumab in melanoma. To date there have been no clinical trials investigating this combination in glioblastoma. In this single practice case series, 20 patients with glioblastoma were consented for and treated with ipilimumab and bevacizumab in combination. Safety, tolerability and the response to treatment were reviewed for all patients. Three patients were treated after palliative first-line radiotherapy, one patient after first-line chemoradiation and 16 patients were treated with recurrent disease. Sixty-five per cent of patients completed four cycles of 3 weekly ipilimumab therapy, administered with 2 weekly bevacizumab. Radiographic responses for patients with recurrent disease were evaluated by Response Assessment in Neuro-oncology (RANO) criteria; 31% of patients showed a partial response, 31% had stable disease and 38% had disease progression. The treatment combination was well tolerated, with treatment terminated before completion due to adverse events in two patients. Autoimmune toxicity was manageable with systemic corticosteroid therapy. Ipilimumab and bevacizumab in combination show promising activity with a predictable and manageable toxicity profile, warranting further clinical studies.

Cytotoxic T lymphocyte antigen-4 and immune checkpoint blockade.

The relationship between cancer and the immune system is complex and provides unique therapeutic opportunities. Cytotoxic T lymphocyte antigen-4 (CTLA-4) is a regulatory molecule that suppresses T cell effector function following initial activation by costimulatory signals. Fully human monoclonal antibodies targeting CTLA-4 have been shown to increase T cell function and antitumor responses in patients with advanced metastatic melanoma. Responses observed with such immune checkpoint therapy can follow a different pattern from that seen with cytotoxic chemotherapy or targeted therapy and may continue after therapy is discontinued. In addition, the toxicities that are associated with anti-CTLA-4 therapy may differ from those of conventional therapies and consist of inflammatory events in parts of the body that do not contain cancerous cells. Early recognition of these inflammatory events and intervention is important, and the identification of predictive biomarkers continues to be an unfulfilled need in the field of immunotherapy. Combinatorial approaches with targeted therapies, radiation therapy, chemotherapy, or other immune checkpoint agonists/antagonists have the potential to increase the efficacy of CTLA-4 blockade.

Cytotoxic T lymphocyte antigen-4 blockade enhances antitumor immunity by stimulating melanoma-specific T-cell motility.

It is now clear that anti-CTLA-4 (α-CTLA-4) antibodies stimulate tumor immunity either by relieving inhibition of effector T-cell function or by depletion of regulatory T cells (Treg). Several recent reports, however, have suggested that these antibodies may deliver a "go" signal to effector T cells, thus interrupting T-cell receptor signaling and subsequent T-cell activation. We examined the behavior of melanoma-specific CD8+ pmel-1 T cells in the B16/BL6 mouse model using intravital microscopy. Pmel-1 velocities in progressively growing tumors were lower than their velocities in tumors given a therapeutic combination that included α-CTLA-4 antibodies, suggesting that successful immunotherapy correlates with greater T-cell motility. When α-CTLA-4 antibodies were injected during imaging, the velocities of pmel-1 T cells in tumor-draining lymph nodes also increased. Because α-CTLA-4 Fab fragments had the same effect as the intact antibody, the higher T-cell motility does not seem to be due to CTLA-4 inhibitory signaling but rather to the release of nonproductive stable interactions between tumor-infiltrating T cells and tumor targets or antigen-presenting cells subsequent to CTLA-4 blockade. This phenomenon resembles the recently described reversal of the antiviral T-cell motility paralysis by programmed death 1 (PD-1)-specific antibodies during T-cell exhaustion in persistent viral infections.

Clinical evaluation of compounds targeting PD-1/PD-L1 pathway for cancer immunotherapy.

Significant enthusiasm currently exists for new immunotherapeutic strategies: blocking the interaction between programmed death-1 receptor on T-cells and programmed death-ligand 1 on tumor cells to boost immune system stimulation to fight cancer. Immunomodulation with the antiprogrammed death-1/programmed death-ligand 1 monoclonal antibodies has shown to mediate tumor shrinkage and extend overall survival from several pivotal phase I/II studies in melanoma, renal cell carcinoma, and non-small cell lung cancer. This has prompted multiple large ongoing phase III trials with the expectation for fast-track FDA approvals to satisfy unmet medical needs. Compounds targeting the programmed death-1 pathway that are in clinical trials fall into two major categories, namely antiprogrammed death-1 antibodies: Nivolumab, MK-3475, and pidilizumab; and antiprogrammed death-ligand 1 antibodies: MPDL3280A, BMS-936559, MEDI4736, and MSB0010718C. We reviewed the clinical efficacy and safety of each compound based upon major registered clinical trials and published clinical data. Overall, response rate of more than 20% is consistently seen across all these trials, with maximal response of approximately 50% achieved by certain single antiprogrammed death-1 agents or when used in combination with cytotoxic T-lymphocyte antigen-4 blockade. The responses seen are early, durable, and have continued after treatment discontinuation. Immune-related adverse events are the most common side effects seen in these clinical trials. Overall, the skin and gastrointestinal tract are the most common organ systems affected by these compounds while hepatic, endocrine, and neurologic events are less frequent. These side effects are low grade, manageable, and typically resolve within a relatively short time frame with a predictable resolution pattern given proper management. We therefore propose detailed guidelines for management of major immune-related adverse events that are anticipated with antiprogrammed death-1/programmed death-ligand 1 therapies based on general experience with other monoclonal antibodies and the established management algorithms for immune-related adverse events for cytotoxic T-lymphocyte antigen-4 blockade with ipilimumab. We anticipate that the antiprogrammed death-1 strategy will become a viable and crucial clinical strategy for cancer therapy.

Improved survival with T cell clonotype stability after anti-CTLA-4 treatment in cancer patients.

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) blockade can promote antitumor T cell immunity and clinical responses. The mechanism by which anti-CTLA-4 antibodies induces antitumor responses is controversial. To determine the effects of CTLA-4 blockade on the T cell repertoire, we used next-generation deep sequencing to measure the frequency of individual rearranged T cell receptor β (TCRβ) genes, thereby characterizing the diversity of rearrangements, known as T cell clonotypes. CTLA-4 blockade in patients with metastatic castration-resistant prostate cancer and metastatic melanoma resulted in both expansion and loss of T cell clonotypes, consistent with a global turnover of the T cell repertoire. Overall, this treatment increased TCR diversity as reflected in the number of unique TCR clonotypes. The repertoire of clonotypes continued to evolve over subsequent months of treatment. Whereas the number of clonotypes that increased with treatment was not associated with clinical outcome, improved overall survival was associated with maintenance of high-frequency clones at baseline. In contrast, the highest-frequency clonotypes fell with treatment in patients with short overall survival. Stably maintained clonotypes included T cells having high-avidity TCR such as virus-reactive T cells. Together, these results suggest that CTLA-4 blockade induces T cell repertoire evolution and diversification. Moreover, improved clinical outcomes are associated with less clonotype loss, consistent with the maintenance of high-frequency TCR clonotypes during treatment. These clones may represent the presence of preexisting high-avidity T cells that may be relevant in the antitumor response.

Engagement of the ICOS pathway markedly enhances efficacy of CTLA-4 blockade in cancer immunotherapy

Cytotoxic T lymphocyte antigen-4 (CTLA-4) blockade with a monoclonal antibody yields durable responses in a subset of cancer patients and has been approved by the FDA as a standard therapy for late-stage melanoma. We recently identified inducible co-stimulator (ICOS) as a crucial player in the antitumor effects of CTLA-4 blockade. We now show that concomitant CTLA-4 blockade and ICOS engagement by tumor cell vaccines engineered to express ICOS ligand enhanced antitumor immune responses in both quantity and quality and significantly improved rejection of established melanoma and prostate cancer in mice. This study provides strong support for the development of combinatorial therapies incorporating anti-CTLA-4 and ICOS engagement.

Ipilimumab, Vemurafenib, Dabrafenib, and Trametinib: Synergistic Competitors in the Clinical Management of BRAF Mutant Malignant Melanoma

There have been significant advances in the treatment of malignant melanoma with the U.S. Food and Drug Administration approval of two drugs in 2011, the first drugs approved in 13 years. The developments of immune checkpoint modulation via cytotoxic T-lymphocyte antigen-4 blockade, with ipilimumab, and targeting of BRAF(V600), with vemurafenib or dabrafenib, as well as MEK, with trametinib, have been paradigm changing both for melanoma clinical practice and for oncology therapeutic development. These advancements, however, reveal new clinical questions regarding combinations and optimal sequencing of these agents in patients with BRAF mutant disease. We review the development of these agents, putative biomarkers, and resistance mechanisms relevant to their use, and possibilities for sequencing and combining these agents.

Requirement of Antitumor Immunity and Enhancement by CTL-associated Antigen-4 Blockade on Therapeutic Efficacy of Radiation Therapy in a Mouse Tumor Model

Requirement of Antitumor Immunity and Enhancement by CTL-associated Antigen-4 Blockade on Therapeutic Efficacy of Radiation Therapy in a Mouse Tumor Model