Anti-angiogenic activity of VXM01, an oral T-cell vaccine against VEGF receptor 2, in patients with advanced pancreatic cancer: A randomized, placebo-controlled, phase 1 trial.

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Abstract

VEGFR-2 is expressed on tumor vasculature and a target for anti-angiogenic intervention. VXM01 is a first in kind orally applied tumor vaccine based on live, attenuated Salmonella bacteria carrying an expression plasmid, encoding VEGFR-2. We here studied the safety, tolerability, T effector (Teff), T regulatory (Treg) and humoral responses to VEGFR2 and anti-angiogenic effects in advanced pancreatic cancer patients in a randomized, dose escalation phase I clinical trial. Results of the first 3 mo observation period are reported. Locally advanced or metastatic, pancreatic cancer patients were enrolled. In five escalating dose groups, 30 patients received VXM01 and 15 placebo on days 1, 3, 5, and 7. Treatment was well tolerated at all dose levels. No dose-limiting toxicities were observed. Salmonella excretion and salmonella-specific humoral immune responses occurred in the two highest dose groups. VEGFR2 specific Teff, but not Treg responses were overall increased in vaccinated patients. We furthermore observed a significant reduction of tumor perfusion after 38 d in vaccinated patients together with increased levels of serum biomarkers indicative of anti-angiogenic activity, VEGF-A, and collagen IV. Vaccine specific Teff responses significantly correlated with reductions of tumor perfusion and high levels of preexisting VEGFR2-specific Teff while those showing no antiangiogenic activity had low levels of preexisting VEGFR2 specific Teff, showed a transient early increase of VEGFR2-specific Treg and reduced levels of VEGFR2-specific Teff at later time points - pointing to the possibility that early anti-angiogenic activity might be based at least in part on specific reactivation of preexisting memory T cells.

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Vascular endothelial growth factor and its receptor system: physiological functions in angiogenesis and pathological roles in various diseases.

Masabumi Shibuya (2013)

Vascular endothelial growth factors (VEGFs) belong to the platelet-derived growth factor supergene family, and they play central roles in the regulation of angiogenesis and lymphangiogenesis. VEGF-A, the major factor for angiogenesis, binds to two tyrosine kinase (TK) receptors, VEGFR-1 (Flt-1) and VEGFR-2 (KDR/Flk-1), and regulates endothelial cell proliferation, migration, vascular permeability, secretion and other endothelial functions. VEGFR-2 exhibits a strong TK activity towards pro-angiogenic signals, whereas the soluble VEGFR-1 (sFlt-1) functions as an endogenous VEGF inhibitor. sFlt-1 is abnormally overexpressed in the placenta of preeclampsia patients, resulting in the major symptoms of the disease due to abnormal trapping of VEGFs. The VEGF-VEGFR system is crucial for tumour angiogenesis, and anti-VEGF-VEGFR molecules are now widely used in the clinical field to treat cancer patients. The efficacy of these molecules in prolonging the overall survival of patients has been established; however, some cancers do not respond well and reduced tumour sensitivity to anti-VEGF signals may occur after long-term treatment. The molecular basis of tumour refractoriness should be determined to improve anti-angiogenic therapy.

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Phase III trial of bevacizumab in combination with gemcitabine and erlotinib in patients with metastatic pancreatic cancer.

Sharlene Gill, Jean-Luc Laethem, Chris Verslype … (2009)

Treatment with gemcitabine provides modest benefits in patients with metastatic pancreatic cancer. The addition of erlotinib to gemcitabine shows a small but significant improvement in overall survival (OS) versus gemcitabine alone. Phase II results for bevacizumab plus gemcitabine provided the rationale for a phase III trial of gemcitabine-erlotinib plus bevacizumab or placebo. Patients with metastatic pancreatic adenocarcinoma were randomly assigned to receive gemcitabine (1,000 mg/m(2)/week), erlotinib (100 mg/day), and bevacizumab (5 mg/kg every 2 weeks) or gemcitabine, erlotinib, and placebo in this double-blind, phase III trial. Primary end point was OS; secondary end points included progression-free survival (PFS), disease control rate, and safety. A total of 301 patients were randomly assigned to the placebo group and 306 to the bevacizumab group. Median OS was 7.1 and 6.0 months in the bevacizumab and placebo arms, respectively (hazard ratio [HR], 0.89; 95% CI, 0.74 to 1.07; P = .2087); this difference was not statistically significant. Adding bevacizumab to gemcitabine-erlotinib significantly improved PFS (HR, 0.73; 95% CI, 0.61 to 0.86; P = .0002). Treatment with bevacizumab plus gemcitabine-erlotinib was well tolerated: safety data did not differ from previously described safety profiles for individual drugs. The primary objective was not met. The addition of bevacizumab to gemcitabine-erlotinib did not lead to a statistically significant improvement in OS in patients with metastatic pancreatic cancer. PFS, however, was significantly longer in the bevacizumab group compared with placebo. No unexpected safety events were observed from adding bevacizumab to gemcitabine-erlotinib.

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Controlling escape from angiogenesis inhibitors.

Barbara Sennino, Sarah McDonald (2012)

Selective inhibition of vascular endothelial growth factor (VEGF) increases the efficacy of chemotherapy and has beneficial effects on multiple advanced cancers, but response is often limited and the disease eventually progresses. Changes in the tumour microenvironment--hypoxia among them--that result from vascular pruning, suppressed angiogenesis and other consequences of VEGF inhibition can promote escape and tumour progression. New therapeutic approaches that target pathways that are involved in the escape mechanisms add the benefits of blocking tumour progression to those of slowing tumour growth by inhibiting angiogenesis.