VB-111: a novel anti-vascular therapeutic for glioblastoma multiforme.

Glioblastoma multiforme (GBM) is among the most highly vascularized of solid tumors, contributing to the infiltrative nature of the disease, and conferring poor outcome. Due to the critical dependency of GBM on growth of new endothelial vasculature, we evaluated the preclinical activity of a novel adenoviral gene therapy that targets the endothelium within newly formed blood vessels for apoptosis. VB-111, currently in phase II clinical trials, consists of a non-replicating Adenovirus 5 (El deleted) carrying a proapoptotic human Fas-chimera (transgene) under the control of a modified murine promoter (PPE-1-3×) which specifically targets endothelial cells within the tumor vasculature. Here we report that a single intravenous dose of 2.5 × 10(11) or 1 × 10(11) VPs was sufficient to extend survival in nude rats bearing U87MG-luc2 or nude mice bearing U251-luc, respectively. Bioluminescence imaging of nude rats showed that VB-111 effectively inhibited tumor growth within four weeks of treatment. This was confirmed in a select group of animals by MRI. In our mouse model we observed that 3 of 10 nude mice treated with VB-111 completely lost U251 luciferase signal and were considered long term survivors. To assess the antiangiogenic effects of VB-111, we evaluated the tumor-associated microvaculature by CD31, a common marker of neovascularization, and found a significant decrease in the microvessel density by IHC. We further assessed the neovasculature by confocal microscopy and found that VB-111 inhibits vascular density in two separate mouse models bearing U251-RFP xenografts. Collectively, this study supports the clinical development of VB-111 as a treatment for GBM.

Systemic administration of a conditionally replicating adenovirus, targeted to angiogenesis, reduced lung metastases burden in cotton rats.

PURPOSE: Angiogenesis is an essential process for solid tumor development. To interfere with angiogenesis, AdPPE3x-E1, an adenovirus that is transcriptionally targeted to replicate in angiogenic endothelial cells, was constructed, by replacing the E1 promoter with the modified preproendothelin-1 promoter, PPE-1-3x, previously shown to induce specific transcription in angiogenic endothelial cells. EXPERIMENTAL DESIGN: The specificity of AdPPE3x-E1 to endothelial cells was shown by quantitative PCR and immunostaining, and its antiangiogenic effect was evaluated in Matrigel models. The in vivo efficacy of AdPPE3x-E1 was also tested in a cotton rat lung metastases model. RESULTS: The replication rate of AdPPE3x-E1 in endothelial cells was similar to that of AdCMV-E1, a nonselective replicating adenovector, but the replication rate was reduced up to 60-fold in nonendothelial cells. Moreover, AdPPE3x-E1 reduced endothelial cell viability by 90% whereas nonendothelial cells were not affected. In in vitro and in vivo Matrigel models, endothelial cells infected with AdPPE3x-E1 did not develop capillary-like structures. The systemic administration of AdPPE3x-E1 reduced the lung metastases burden in a cotton rat model by 55%, compared with saline-treated rats, without significant evidence of toxicity. Quantitative PCR analysis showed that the viral copy number of AdPPE3x-E1 was increased 3-fold in the lung metastases but not in the liver, compared with a nonreplicating adenovector control. CONCLUSIONS: We have shown here for the first time an antimetastatic effect induced by an angiogenesis-transcriptionally targeted adenovirus following systemic administration. Because adenovirus replication is more efficient in humans than in cotton rats, we assume a significant effect for AdPPE3x-E1 treatment in fighting human solid tumors and metastases.

Endothelial-targeted gene transfer of hypoxia-inducible factor-1alpha augments ischemic neovascularization following systemic administration.

Hypoxia-inducible factor-1alpha (HIF-1alpha) is a key regulator of the response to low oxygen levels and has been used for therapeutic angiogenesis. Various routes of administration have been used for delivering genes to the ischemic region including the intramuscular (IM) and intraarterial routes. When compared with these delivery methods, the intravenous (IV) route confers many advantages, including less invasiveness and lower cost. However, its use is hampered by the fact that it does not result in specific and robust tissue expression of the genes. Our aim was to determine the feasibility, safety, and therapeutic efficacy of systemic administration of adenoviral-mediated HIF-1alpha targeted to the endothelium. Using confocal microscopy and biodistribution studies we demonstrated that a modified murine preproendothelin-1 promoter (PPE1-3x) can target gene expression specifically to endothelial cells within ischemic muscle following systemic IV administration in C57BL/6 mice. Accordingly, an adenovirus expressing a PPE1-3x-regulated stabilized HIF-1alpha molecule, further activated by constitutive activation of its C-transactivation domain (C-TAD), was created. Systemic tail-vein administration of this adenovirus in a mouse hindlimb ischemia model resulted in enhanced blood perfusion, improved clinical outcome, and increased capillary density without systemic toxicity, in contrast to the profound systemic side effects and lack of therapeutic efficacy following cytomegalovirus (CMV)-regulated HIF-1alpha administration. Collectively, these data suggest that transcriptionally controlled systemic proangiogenic gene therapy is feasible, safe, and efficacious.

Endothelial-targeted Gene Transfer of Hypoxia-inducible Factor-1α Augments Ischemic Neovascularization Following Systemic Administration.

Hypoxia-inducible factor-1α (HIF-1α) is a key regulator of the response to low oxygen levels and has been used for therapeutic angiogenesis. Various routes of administration have been used for delivering genes to the ischemic region including the intramuscular (IM) and intraarterial routes. When compared with these delivery methods, the intravenous (IV) route confers many advantages, including less invasiveness and lower cost. However, its use is hampered by the fact that it does not result in specific and robust tissue expression of the genes. Our aim was to determine the feasibility, safety, and therapeutic efficacy of systemic administration of adenoviral-mediated HIF-1α targeted to the endothelium. Using confocal microscopy and biodistribution studies we demonstrated that a modified murine preproendothelin-1 promoter (PPE1-3x) can target gene expression specifically to endothelial cells within ischemic muscle following systemic IV administration in C57BL/6 mice. Accordingly, an adenovirus expressing a PPE1-3x-regulated stabilized HIF-1α molecule, further activated by constitutive activation of its C-transactivation domain (C-TAD), was created. Systemic tail-vein administration of this adenovirus in a mouse hindlimb ischemia model resulted in enhanced blood perfusion, improved clinical outcome, and increased capillary density without systemic toxicity, in contrast to the profound systemic side effects and lack of therapeutic efficacy following cytomegalovirus (CMV)-regulated HIF-1α administration. Collectively, these data suggest that transcriptionally controlled systemic proangiogenic gene therapy is feasible, safe, and efficacious.

Activation of C-transactivation domain is essential for optimal HIF-1 alpha-mediated transcriptional and angiogenic effects.

UNLABELLED: HIF-1 is a transcription factor that regulates genes involved in oxygen homeostasis. In normoxia, degradation of the HIF-1 alpha subunit is enabled by two prolyl hydroxylations at residues P402 and P564, while inactivation occurs through asparaginyl hydroxylation at residue N803 within its C-transactivation domain (C-TAD). For therapeutic angiogenesis purposes, HIF-1 alpha stabilization was previously achieved by either deleting its oxygen-dependent degradation domains, or introducing two proline point mutations at residues P402 and P564. We assessed the hypothesis that constitutive activation of HIF-1 alpha in addition to its stabilization would result in greater HIF-1 alpha transcriptional activity and angiogenic effects than mere stabilization of the molecule. For this, we constructed a Triple mutant HIF-1 alpha (TM), bearing mutations P402A and P564G N803A. Transient co-transfections with hypoxia-responsive element-luciferase construct revealed 2 to 2.5-fold increase in transcriptional activity of TM compared with P402A P564G double mutant and wild-type HIF-1 alpha. In-vitro angiogenesis assay using transfected human umbilical vein endothelial cells (HUVEC) showed that TM stimulated tube formation to a greater extent than both P402A P564G mutant and wild-type HIF-1 alpha. Accordingly, ELISA revealed that VEGF levels within the transfected HUVEC were about 10-fold greater with the TM. CONCLUSIONS: Constitutive activation of the HIF-1 alpha C-TAD, and not merely stabilization of the HIF-1 alpha molecule, is essential for optimal HIF-mediated transcriptional and angiogenic effects. This finding could have important implications for therapeutic angiogenesis using HIF-1 alpha.

Transcription-controlled gene therapy against tumor angiogenesis.

A major drawback of current approaches to antiangiogenic gene therapy is the lack of tissue-specific targeting. The aim of this work was to trigger endothelial cell-specific apoptosis, using adenoviral vector-mediated delivery of a chimeric death receptor derived from the modified endothelium-specific pre-proendothelin-1 (PPE-1) promoter. In the present study, we constructed an adenovirus-based vector that targets tumor angiogenesis. Transcriptional control was achieved by use of a modified endothelium-specific promoter. Expression of a chimeric death receptor, composed of Fas and TNF receptor 1, resulted in specific apoptosis of endothelial cells in vitro and sensitization of cells to the proapoptotic effect of TNF-alpha. The antitumoral activity of the vectors was assayed in two mouse models. In the model of B16 melanoma, a single systemic injection of virus to the tail vein caused growth retardation of tumor and reduction of tumor mass with central tumor necrosis. When the Lewis lung carcinoma lung-metastasis model was applied, i.v. injection of vector resulted in reduction of lung-metastasis mass, via an antiangiogenic mechanism. Moreover, by application of the PPE-1-based transcriptional control, a humoral immune response against the transgene was avoided. Collectively, these data provide evidence that transcriptionally controlled, angiogenesis-targeted gene therapy is feasible.

Suppression of early atherosclerosis in LDL-receptor deficient mice by oral tolerance with beta 2-glycoprotein I.

BACKGROUND: Atherosclerosis is considered analogous to chronic inflammatory diseases. Beta 2-glycoprotein I (beta 2GPI) is a phospholipid binding protein shown to serve as a target for prothrombotic antiphospholipid antibodies. It has recently been demonstrated to drive an immune mediated reaction and enhance murine atherosclerosis. Oral tolerance is a method in which feeding a given antigen, downregulates the respective immune responses towards it, and attenuates concomitant organ specific disorders. Herein, we tested the hypothesis, that inhibiting cellular immunity to beta 2GPI would result in suppression of fatty streak formation in mice. METHODS AND RESULTS: LDL receptor deficient mice were fed different doses of human or bovine beta 2GPI or BSA and than switched to an atherogenic diet. To determine the effect of feeding on lymph node proliferative indices, separate groups of mice were fed beta 2GPI and then immunized with the respective antigen. Feeding either human or bovine beta 2GPI was effective in attenuating atherosclerosis as compared to control fed animals. Oral feeding with of beta 2GPI inhibited lymph node cell reactivity to beta 2GPI in mice immunized against the human protein. Oral tolerance was also capable of reducing reactivity to oxidized LDL in mice immunized against oxLDL. IL-4 and IL-10 production was upregulated in lymph node cells of beta 2GPI-tolerant mice immunized against beta 2GPI, upon priming with the respective protein. CONCLUSION: Thus, oral administration of beta 2GPI is an effective means of suppressing atherogenesis in mice and should further be investigated.

Phase I dose-escalation study of VB-111, an antiangiogenic virotherapy, in patients with advanced solid tumors.

PURPOSE: VB-111 is an antiangiogenic agent consisting of a nonreplicating adenovirus vector (Ad-5) with a modified murine pre-proendothelin promoter leading to apoptosis of tumor vasculature by expressing a Fas-chimera transgene in angiogenic endothelial cells. In a phase I dose-escalation study, pharmacokinetics, pharmacodynamics, safety, and efficacy of a single dose of VB-111 in patients with advanced solid tumors were evaluated. EXPERIMENTAL DESIGN: VB-111 was administered as a single i.v. infusion at escalating doses from 1 × 10(10) (cohort 1) to 1 × 10(13) (cohort 7) viral particles (VP) in successive cohorts. Assessments included pharmacokinetic and pharmacodynamic profiles, tumor response, and overall survival. RESULTS: Thirty-three patients were enrolled. VB-111 was safe and well-tolerated; self-limited fever and chills were seen at doses above 3 × 10(11) VPs. Transgene expression was not detected in blood but was detected in an aspirate from a subcutaneous metastasis after treatment. One patient with papillary thyroid carcinoma had a partial response. CONCLUSIONS: VB-111 was safe and well tolerated in patients with advanced metastatic cancer at a single administration of up to 1 × 10(13) VPs. Evidence of transgene expression in tumor tissue and tumor response was observed.

Systemic administration of radiation-potentiated anti-angiogenic gene therapy against primary and metastatic cancer based on transcriptionally controlled HSV-TK.

Transcription-targeted gene delivery directed against angiogenic endothelial cells is a new approach against advanced cancer. Moreover, the herpes simplex virus-thymidine kinase (HSV-TK) gene coupled with low dose radiotherapy is an efficient and externally controlled cytotoxic system. We have previously demonstrated enhanced endothelial-specific cell expression and killing using the modified murine pre-proendothelin-1 promoter (PPE1-3x) to direct adenoviral expression of a pro-apoptotic gene. The purpose of this study was to create an externally potentiated systemic antiangiogenic gene delivery system based on an adenoviral vector expressing HSV-TK under the regulation of PPE1-3X promoter combined with radiotherapy for eradicating metastatic cancer. Ad-PPE1-3x-TK induced endothelial-specific cell killing in-vitro upon introduction of the prodrug ganciclovir (GCV). BALB/c mice bearing a primary CT-26 colon carcinoma tumor showed tumor growth suppression and diminished tumor angiogenesis when the vector was administered intravenously, activated with GCV and potentiated with a single sub-therapeutic and non-toxic radiation dose. Moreover, intravenous administration of the vector, activated with GCV and potentiated with chest aimed radiation, to C57BL/6 mice bearing Lewis lung carcinoma metastases resulted in prolongation of mice survival. PPE1-3x-regulated HSV-TK expression was detected only in lung metastases in contrast to CMV-regulated expression. This novel system may benefit patients with metastatic disease.