A B S T R A C T PurposeGranulocyte-macrophage colony-stimulating factor (GM-CSF) -secreting tumor vaccines have demonstrated bioactivity but may be limited by disease burdens and immune tolerance. We tested the hypothesis that cyclophosphamide (CY) and doxorubicin (DOX) can enhance vaccine-induced immunity in patients with breast cancer. Patients and MethodsWe conducted a 3 ϫ 3 factorial (response surface) dose-ranging study of CY, DOX, and an HER2-positive, allogeneic, GM-CSF-secreting tumor vaccine in 28 patients with metastatic breast cancer. Patients received three monthly immunizations, with a boost 6 to 8 months from study entry. Primary objectives included safety and determination of the chemotherapy doses that maximize HER2-specific immunity. Results Twenty ConclusionFirst, immunotherapy with an allogeneic, HER2-positive, GM-CSF-secreting breast tumor vaccine alone or with CY and DOX is safe and induces HER2-specific immunity in patients with metastatic breast cancer. Second, the immunomodulatory activity of low-dose CY has a narrow therapeutic window, with an optimal dose not exceeding 200 mg/m 2 . Third, factorial designs provide an opportunity to identify the most active combination of interacting drugs in patients. Further investigation of the impact of chemotherapy on vaccine-induced immunity is warranted.

Purpose: Given the complex tumor microenvironment, targeting multiple cellular components may be the most effective cancer treatment strategy. Therefore, we tested whether antiangiogenic and immune-based therapy might synergize by characterizing the activity of DC101, an antiangiogenic monoclonal antibody specific for vascular endothelial growth factor receptor-2 (VEGF-R2), alone and with HER-2/neu (neu)^targeted vaccination. Experimental Design: Neu-expressing breast tumors were measured in treated nontolerant FVB mice and immune-tolerant neu transgenic (neu-N) mice. Neu-specific and tumor cellŝ pecific immune responses were assessed by intracellular cytokine staining, ELISPOT, and CTL assays.Results: DC101 decreased angiogenesis and increased tumor cell apoptosis. Although DC101 increased serum levels of the immunosuppressive cytokine VEGF, no evidence of systemic immune inhibition was detected. Moreover, DC101 did not impede the influx of tumor-infiltrating lymphocytes. In FVB mice, DC101 inhibited tumor growth in part through a T cell^dependent mechanism, resulting in both increased tumor-specific CD8 + T cells and tumor regression. Combining DC101 with neu-specific vaccination accelerated tumor regression, augmenting the lytic activity of CD8 + cytotoxicTcells. In tolerant neu-N mice, DC101only delayed tumor growth without inducing frank tumor regression or antigen-specific T-cell activation. Notably, mitigating immune tolerance by inhibiting regulatoryTcell activity with cyclophosphamide revealed DC101-mediated augmentation of antitumor responses in vaccinated neu-N mice. Conclusions: This is the first report of DC101-induced antitumor immune responses. It establishes the induction of tumor-specificT-cell responses as one consequence of VEGF-R2 targeting with DC101. These data support the development of multitargeted cancer therapy combining immune-based and antiangiogenic agents for clinical translation.

Granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting tumor vaccines are bioactive, but limited by disease burden and immune tolerance. Cyclophosphamide (CY) augments vaccine activity in tolerant neu mice and metastatic breast cancer (MBC) patients. HER-2-specific monoclonal antibodies (MAb) enhance vaccine activity in neu mice. We hypothesized that CY-modulated vaccination with HER-2-specific MAb safely induces relevant HER-2-specific immunity in neu mice and HER-2+ MBC patients. Adding both CY and the HER-2-specific MAb 7.16.4 to vaccination maximized HER-2-specific CD8+ T-cell immunity and tumor-free survival in neu transgenic mice. We therefore conducted a single arm feasibility study of CY, an allogeneic HER-2+ GM-CSF-secreting breast tumor vaccine, and weekly trastuzumab in 20 HER-2+ MBC patients. Primary clinical trial objectives were safety and clinical benefit (CB), in which CB represents complete response+partial response+stable disease. Secondary study objectives were to assess HER-2-specific T-cell responses by delayed type hypersensitivity (DTH) and intracellular cytokine staining. Subjects received three monthly vaccinations, with a boost 6-8 months from trial entry. This combination immunotherapy was safe, with CB rates at 6 months and 1 year of 55% (95% CI:32-77%, p=0.013) and 40% (95% CI:19-64%) respectively. Median progression-free survival (PFS) and overall survival (OS) were 7 (95% CI:4-16) and 42 months (95% CI:22-70) respectively. Increased HER-2-specific DTH developed in 7/20 subjects (of whom 4 had CB (95% CI:18-90)), with a trend toward longer PFS and OS in DTH responders. Polyfunctional HER-2-specific CD8+ T cells progressively expanded across vaccination cycles. Further investigation of CY-modulated vaccination with trastuzumab is warranted. (Clinicaltrials.gov identifier: NCT00399529)