Jennifer N. Uram

Evaluation of Ipilimumab in combination with allogeneic pancreatic tumor cells transfected with a GM-CSF gene in previously treated pancreatic cancer

Preclinical reports support the concept of synergy between cancer vaccines and immune checkpoint blockade in nonimmunogenic tumors. In particular, cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) antibodies have been successfully combined with GM-CSF cell-based vaccines (GVAX). Ipilimumab (anti-CTLA-4) has been tested as a single agent in patients with pancreatic ductal adenocarcinoma (PDA) resulting in a delayed response at a dose of 3 mg/kg. Our study evaluated ipilimumab 10 mg/kg (arm 1) and ipilimumab 10 mg/kg+GVAX (arm 2). A total of 30 patients with previously treated advanced PDA were randomized (1:1). Induction doses were administered every 3 weeks for a total of 4 doses followed by maintenance dosing every 12 weeks. Two patients in arm 1 showed evidence of stable disease (7 and 22 wk) but none demonstrated CA19-9 biochemical responses. In contrast, 3 patients in arm 2 had evidence of prolonged disease stabilization (31, 71, and 81 wk) and 7 patients experienced CA19-9 declines. In 2 of these patients, disease stabilization occurred after an initial period of progression. The median overall survival (OS) (3.6 vs. 5.7 mo, hazards ratio: 0.51, P=0.072) and 1 year OS (7 vs. 27%) favored arm 2. Similar to prior ipilimumab studies, 20% of patients in each arm had grade 3/4 immune-related adverse events. Among patients with OS>4.3 months, there was an increase in the peak mesothelin-specific T cells (P=0.014) and enhancement of the T-cell repertoire (P=0.031). In conclusion, checkpoint blockade in combination with GVAX has the potential for clinical benefit and should be evaluated in a larger study.

A Feasibility Study of Cyclophosphamide, Trastuzumab, and an Allogeneic GM-CSF–Secreting Breast Tumor Vaccine for HER2+ Metastatic Breast Cancer

Chen and colleagues show in patients and in a mouse model of HER2+ breast cancer that abrogating immune suppression with low-dose cyclophosphamide along with administration of an allogeneic GM-CSF–secreting HER2+ tumor vaccine and trastuzumab weekly augmented HER2-specific T-cell responses and survival. Granulocyte-macrophage colony-stimulating factor (GM-CSF)–secreting tumor vaccines are bioactive, but limited by disease burden and immune tolerance. Cyclophosphamide augments vaccine activity in tolerant neu mice and in patients with metastatic breast cancer. HER2-specific monoclonal antibodies (mAb) enhance vaccine activity in neu mice. We hypothesized that cyclophosphamide-modulated vaccination with HER2-specific mAb safely induces relevant HER2-specific immunity in neu mice and patients with HER2+ metastatic breast cancer. Adding both cyclophosphamide and the HER2-specific mAb 7.16.4 to vaccination maximized HER2-specific CD8+ T-cell immunity and tumor-free survival in neu transgenic mice. We, therefore, conducted a single-arm feasibility study of cyclophosphamide, an allogeneic HER2+ GM-CSF–secreting breast tumor vaccine, and weekly trastuzumab in 20 patients with HER2+ metastatic breast cancer. Primary clinical trial objectives were safety and clinical benefit, in which clinical benefit represents complete response + partial response + stable disease. Secondary study objectives were to assess HER2-specific T-cell responses by delayed type hypersensitivity (DTH) and intracellular cytokine staining. Patients received three monthly vaccinations, with a boost 6 to 8 months from trial entry. This combination immunotherapy was safe, with clinical benefit rates at 6 months and 1 year of 55% [95% confidence interval (CI), 32%–77%; P = 0.013] and 40% (95% CI, 19%–64%), respectively. Median progression-free survival and overall survival durations were 7 months (95% CI, 4–16) and 42 months (95% CI, 22–70), respectively. Increased HER2-specific DTH developed in 7 of 20 patients [of whom 4 had clinical benefit (95% CI, 18–90)], with a trend toward longer progression-free survival and overall survival in DTH responders. Polyfunctional HER2-specific CD8+ T cells progressively expanded across vaccination cycles. Further investigation of cyclophosphamide-modulated vaccination with trastuzumab is warranted. (Clinicaltrials.gov identifier: NCT00399529) Cancer Immunol Res; 2(10); 949–61. ©2014 AACR.

Nondominant CD8 T Cells Are Active Players in the Vaccine-Induced Antitumor Immune Response

We previously reported that CD8+ T cells are directed predominantly toward the immunodominant Her-2/neu (neu) epitope RNEU420–429 in nontolerized FVB/N but not tolerized HER-2/neu (neu-N) mice. In this study, we screened overlapping peptides of the entire neu protein and identified six new epitopes recognized by vaccine-induced neu-N–derived T cells. Evaluation of individual nondominant responses by tetramer staining and IFN-γ secretion demonstrate that this repertoire is peripherally tolerized. To address the role that the complete CD8+ T cell repertoire plays in vaccine-induced antitumor immunity, we created a whole-cell vaccine-expressing neu cDNA that has been mutated at the RNEU420–429 anchor residue, thereby abrogating activation of immunodominant epitope responses. Studies comparing the mutated and nonmutated vaccines indicate that nondominant CD8+ T cells can induce antitumor immunity when combined with regulatory T cell-depleting agents in both neu-N and FVB/N mice. Collectively, these studies demonstrate that the neu-directed T cell repertoire is not intrinsically incapable of eradicating tumors. Rather, they are suppressed by mechanisms of peripheral tolerance. Thus, these studies provide new insights into the function of the complete T cell repertoire directed toward a clinically relevant tumor Ag in tumor-bearing hosts.

Abstract B27: IgE-independent hypersensitvity reactions are associated with prolonged survival in advanced pancreatic cancer patients receiving a GM-CSF cell-based vaccine plus cyclophosphamide (Cy) and cetuximab.

Background: Pre-clinical and clinical studies demonstrate that combining Cy with granulocyte-macrophage colony-stimulating factor (GM-CSF) secreting irradiated allogeneic pancreatic tumor cells (pancGVAX) enhances clinical and vaccine induced anti-tumor immune responses. The mechanism is thought to occur by inhibiting suppressor T-cell activity and promoting a type 1 cytotoxic immune response by promoting dendritic cell (DC) activation. Additional pre-clinical evidence support monoclonal antibodies such as Cetuximab that target growth factor receptors (GFRs) in synergistic anti-tumor immune responses. It is estimated that >70% of pancreatic cancers overexpress EGFR. This supports a role for combinatorial immunotherapies in advanced pancreatic cancer. Methods: Sixty patients with advanced pancreatic cancer who progressed on, or refused, first line standard therapy received six cycles of Cy (250 mg/m2) on day 0, pancGVAX (5x108 cells) on day 1, and Cetuximab on days 1, 8 and 15 (initial dose of 400 mg/m2 and subsequent doses of 250 mg/m2) every three weeks. Patients who experienced grade 3 Cetuximab hypersensitivity reactions continued to receive Cy and pancGVAX treatments without further Cetuximab. Serum cytokines and immunoglobulins were analyzed by ELISA and serum cell populations were evaluated using flow cytometry. Results: Twelve out of the 60 patients were hypersensitive to Cetuximab. Median survival was 4.5 months overall. Survival in the hypersensitivity group was 7.1 versus 4.1 months in the non-hypersensitivity group (p=0.026). Baseline characteristics were similar except for the increased number of metastatic disease sites in the hypersensitivity group (2 or more, 100% versus 69%, p=0.027). There was a significant difference in the association between serum IgE levels at enrollment and overall survival for hypersensitive as compared to non-hypersensitive patients (p=0.004). Among hypersensitive patients, higher serum IgE levels at enrollment was associated with increased risk of death (p=0.019, HR =1.05, 95% CI: 1.009 to 1.099). The baseline serum IgE level was not predictive of overall survival for non-hypersensitive patients (p=0.75); however, higher serum IgE levels following the first vaccine was associated with increased risk (p=0.010, HR = 1.026, 95% CI: 1.006 to 1.046). Lower levels of surface IgE bound to plasmacytoid DCs (pDCs), but not monocytoid DCs or basophils, correlated with overall survival both at baseline (p=0.019) and after vaccination (p=0.006). Overall survival also correlated with lower levels of serum IL-6 (p=0.031) and IL-8 (p=0.043). This suggests that a pDC-mediated skewing towards type 2 inflammatory responses is associated with poor prognosis in these patients. Conclusions: Prolonged survival in advanced pancreatic cancer patients correlated with IgE-independent hypersensitivity to Cetuximab. IgE mediated type 2 inflammatory responses are associated with poor prognosis in patients receiving immunotherapy. Blockade of IgE may enhance the efficacy of immunotherapy in pancreatic cancer patients. Citation Format: Julie Ng, Jennifer Uram, Beth Onners, Barbara Biedrzycki, Elizabeth Sugar, Sara Solt, Todd Armstrong, Dung Le, Lei Zheng, John Schroeder, Elizabeth Jaffee, Daniel Laheru. IgE-independent hypersensitvity reactions are associated with prolonged survival in advanced pancreatic cancer patients receiving a GM-CSF cell-based vaccine plus cyclophosphamide (Cy) and cetuximab. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B27.