Blockade of CTLA-4 and PD-1 Enhances Adoptive T-cell Therapy Efficacy in an ICOS-Mediated Manner.

Adoptive transfer of tumor-reactive T cells (ACT) has led to modest clinical benefit in the treatment of solid tumors. Failures with this therapy are primarily due to inadequate infiltration and poor function of adoptively transferred cells in the tumor microenvironment. To improve the efficacy of ACT, we combined ACT with dual blockade of CTLA-4 and PD-1. Treatment with anti-CTLA-4 plus anti-PD-1 compared with monotherapy resulted in durable antitumor responses, enhanced effector function of ACT, utilizing PMEL-1 transgenic (Tg+) CD8+ T cells, and improved survival. Using PMEL-1ICOS-/- mice, we showed that deletion of the inducible T-cell costimulator (ICOS) receptor abolished the therapeutic benefits, with selective downregulation of Eomesodermin (Eomes), interferon gamma (IFNγ), and perforin. Higher expression of IFNγ and Eomes was noted in human ICOShi CD8+ T cells compared with ICOSlow counterparts. Together, our data provide direct evidence that ACT combined with immune-checkpoint therapy confers durable antitumor responses, which largely depended on CD8+ T-cell-intrinsic expression of ICOS. Our study provides a foundation of testing combinatorial therapy of ACT of CD8 T cells and dual blocking of CTLA-4 and PD-1 in patients with melanoma.

CD4 T cells require ICOS-mediated PI3K signaling to increase T-Bet expression in the setting of anti-CTLA-4 therapy.

The transcription factor T-bet controls the Th1 genetic program in T cells for effective antitumor responses. Anti-CTLA-4 immunotherapy elicits dramatic antitumor responses in mice and in human patients; however, factors that regulate T-bet expression during an antitumor response mediated by anti-CTLA-4 remain to be elucidated. We were the first to report that treatment with anti-CTLA-4 led to an increase in the frequency of T cells expressing inducible costimulator (ICOS). In both treated patients and mice, our data revealed that CD4(+)ICOS(hi) T cells can act as effector T cells, which produce the Th1 cytokine IFN-γ. We also showed in a small retrospective analysis that an increased frequency of CD4(+)ICOS(hi) T cells correlated with better clinical outcome and the absence of ICOS or its ligand (ICOSL) in mouse models led to impaired tumor rejection. Here, we show that CD4(+)ICOS(hi) T cells from anti-CTLA-4-treated patients had an increase in signaling via the phospoinositide-3-kinase (PI3K) pathway and an increase in expression of T-bet. An ICOS-specific siRNA transfected into human T cells led to diminished PI3K signaling and T-bet expression. Therefore, we hypothesized that ICOS, and specifically ICOS-mediated PI3K signaling, was required for T-bet expression. We conducted studies in ICOS-deficient and ICOS-YF mice, which have a single amino acid change that abrogates PI3K signaling by ICOS. We found that ICOS-mediated PI3K signaling is required for T-bet expression during an antitumor response elicited by anti-CTLA-4 therapy. Our data provide new insight into the regulation of T-bet expression and suggest that ICOS can be targeted to improve Th1 antitumor responses.

Increased frequency of ICOS+ CD4 T cells as a pharmacodynamic biomarker for anti-CTLA-4 therapy.

Pharmacodynamic biomarkers can play an important role in understanding whether a therapeutic agent has "hit its target" to impact biologic function. A pharmacodynamic biomarker for anti-CTLA-4 therapy remains to be elucidated. We previously reported that anti-CTLA-4 therapy increases the frequency of CD4 T cells expressing the inducible costimulator (ICOS) molecule. To determine whether the frequency of ICOS(+) CD4 T cells could be used as a pharmacodynamic biomarker for anti-CTLA-4 therapy, we carried out flow cytometric studies and statistical analyses on data from 56 individuals, which included 10 healthy donors, 36 patients who received anti-CTLA-4 monoclonal antibody (mAb), and 10 patients who received treatment with a different immunomodulatory agent (gp100 DNA vaccine). After treatment with anti-CTLA-4 mAb (ipilimumab; Bristol-Myers Squibb), we detected a statistically significant increase in the frequency of ICOS(+) CD4 T-cells. After two doses of anti-CTLA-4 therapy, the assay was found to have an estimated specificity of 96% [95% confidence interval (CI), 88-100] and sensitivity of 71% (95% CI, 54-85), with positive expression defined as a frequency that is more than the upper bound of 95% CI among baseline samples from all subjects. Our data suggest that an increased frequency of ICOS(+) CD4 T cells measured by flow cytometry can be used as a reproducible pharmacodynamic biomarker to indicate biologic activity in the setting of anti-CTLA-4 therapy, which should enable appropriate immune monitoring to determine whether patients receiving anti-CTLA-4 monotherapy or combination treatment strategies are having an adequate biologic response.

Preoperative CTLA-4 blockade: tolerability and immune monitoring in the setting of a presurgical clinical trial.

PURPOSE: Cytotoxic T lymphocyte associated antigen (CTLA-4) blockade is being explored in numerous clinical trials as an immune-based therapy for different malignancies. Our group conducted the first preoperative clinical trial with the anti-CTLA-4 antibody ipilimumab in 12 patients with localized urothelial carcinoma of the bladder. EXPERIMENTAL DESIGN: Six patients were treated with 3 mg/kg/dose of anti-CTLA-4 and six patients were treated with 10 mg/kg/dose of antibody. Primary end points of the study were safety and immune monitoring. RESULTS: Most drug-related adverse events consisted of grade 1/2 toxicities. All patients had measurable immunologic pharmacodynamic effects, consisting of an increased frequency of CD4+ICOShi T cells in tumor tissues and the systemic circulation. To determine if CD4+ICOShi T cells could be a correlative marker for clinical outcome after treatment with anti-CTLA-4, a cohort of metastatic melanoma patients was studied retrospectively for frequency of CD4+ICOShi T cells and survival. Data from this small cohort of patients indicated that an increased frequency of CD4+ICOShi T cells, sustained over a period of 12 weeks of therapy, correlates with increased likelihood of clinical benefit consisting of overall survival. CONCLUSIONS: Our trial shows that anti-CTLA-4 therapy has a tolerable safety profile in the presurgical setting and that a preoperative model can be used to obtain biological data on human immune responses, which can efficiently guide the monitoring of patients treated in the metastatic disease setting.

Concurrent decrease in IL-10 with development of immune-related adverse events in a patient treated with anti-CTLA-4 therapy.

The cytotoxic T lymphocyte antigen-4 (CTLA-4) molecule on T cells acts to maintain homeostasis by regulating the proliferation of recently activated T cells. Blockade of CTLA-4 by anti-CTLA-4 antibody enhances T cell responses and has elicited significant tumor regression in some cancer patients. Clinical trials are ongoing to investigate the efficacy of anti-CTLA-4 antibody as a cancer therapeutic. Reports from several clinical trials have documented the occurrence of adverse events in patients treated with anti-CTLA-4 antibody which have some similarities with autoimmune conditions and have been termed immune-related adverse events (irAEs). Most irAEs are reversible with corticosteroid therapy. Some investigators suggest that irAEs occur in the same patients who have anti-tumor responses as a result of the anti-CTLA-4 antibody. Immunologic mechanisms to explain why irAEs occur in some patients have not been reported. Here we report that bladder cancer patients treated with anti-CTLA-4 antibody have increased levels of the Th1 cytokine IFN-gamma detected in plasma samples. Although IFN-gamma is a potent anti-tumor and inflammatory cytokine, increased levels of IFN-gamma were not associated with irAEs in our patients. However, in one patient who experienced an irAE consisting of ischemic papillopathy and optic neuritis, we documented high pre-therapy levels of the Th2 cytokine IL-10 which decreased after treatment with anti-CTLA-4 antibody. The decrease in plasma IL-10 concentration coincided with the patient's irAE. We propose that decreased levels of IL-10 after treatment with anti-CTLA-4 therapy may be responsible for irAEs in some patients and needs to be further investigated in larger studies.

Focus on TILs: Prognostic significance of tumor infiltrating lymphocytes in human bladder cancer.

The idea of generating cytotoxic T-lymphocytes that have anti-tumor activity has been the focus of many clinical trials aimed at delivering effective immunotherapy to cancer patients. We have gained insight into the human immune system in cancer patients as a result of these numerous clinical investigations. It is now clear that although various vaccination methods are capable of inducing tumor antigen-specific T-cells in the circulating blood, these immunological responses are infrequently correlated with clinical responses. Therefore, it appears that priming of a T-cell response is not sufficient for tumor regression and other avenues, downstream of the priming phase, need to be investigated. Mechanisms of immune evasion at the effector phase of the anti-tumor phase are currently under investigation, with an increasing focus on the tumor microenvironment. There is evidence indicating that multiple variables may contribute to immune escape, including: regulatory cells; inhibitory ligands on tumor cells, such as PD-L1 and B7x; soluble factors such as TGF-beta and IL-10; and nutrient-catabolizing enzymes, such as indoleamine-2,3-dioxygenase (IDO). In addition, there are ongoing efforts to assess the presence and function of effector cells within the tumor microenvironment. Tumor infiltrating lymphocytes (TILs) have been observed in patients with melanoma, colon cancer, and ovarian cancer. TILs in these patients have been associated with favorable clinical outcomes. In the clinical setting of bladder cancer, as compared to melanoma, there is limited data regarding TILs. This review will focus on immunological responses to bladder cancer and ongoing studies to identify factors that are amenable to therapeutic manipulation.