Release of experimental retinal vein occlusions by direct intraluminal injection of ocriplasmin.

PURPOSE: Retinal vein occlusions (RVO) are a major cause of vision loss in people aged 50 years and older. Current therapeutic options limit the consequences of RVO but do not eliminate the cause. Cannulation of the involved vessel and removal of the clot may provide a more permanent solution with a less demanding follow-up. However, cannulation of smaller retinal veins remains challenging. This paper explores the use of ocriplasmin (recombinant plasmin without its kringles) to clear RVO, using a robotic micromanipulator. METHODS: Branch RVO were induced in a porcine model with rose bengal followed by 532 nm endolaser to the superior venous branch of the optic nerve. The vein was cannulated proximal to the occlusion or beyond the first branching vessel from the obstruction. The vein was infused with a physiologic citric acid buffer solution (CAM) or CAM/ocriplasmin. The time of cannulation, number of attempts, and the ability to release the thrombus were recorded. RESULTS: Cannulation and infusion was possible in all the cases. The use of a micromanipulator allowed for a consistent cannulation of the retinal vein and positional stability allowed the vein to remain cannulated for up to 20 min. In none of the attempts (5/5) with CAM did the thrombus dissolve, despite repeat infusion/relaxation cycles. In 7/7 injections of CAM/ocriplasmin near to the point of obstruction, the clot started to dissolve within a few minutes of injection. An infusion, attempted beyond the first venous branch point proximal to the clot, was unsuccessful in 2/3 attempts. CONCLUSIONS: Ocriplasmin is effective in resolving RVO if injected close to the site of occlusion with the use of a micromanipulator.

Robotic Assisted Cannulation of Occluded Retinal Veins.

PURPOSE: To develop a methodology for cannulating porcine retinal venules using a robotic assistive arm after inducing a retinal vein occlusion using the photosensitizer rose bengal. METHODOLOGY: Retinal vein occlusions proximal to the first vascular branch point were induced following intravenous injection of rose bengal by exposure to 532nm laser light delivered by slit-lamp or endolaser probe. Retinal veins were cannulated by positioning a glass catheter tip using a robotically controlled micromanipulator above venules with an outer diameter of 80µm or more and performing a preset piercing maneuver, controlled robotically. The ability of a balanced salt (BSS) solution to remove an occlusion by repeat distention of the retinal vein was also assessed. RESULTS: Cannulation using the preset piercing program was successful in 9 of 9 eyes. Piercing using the micromanipulator under manual control was successful in only 24 of 52 attempts, with several attempts leading to double piercing. The best location for cannulation was directly proximal to the occlusion. Infusion of BSS did not result in the resolution of the occlusion. CONCLUSION: Cannulation of venules using a robotic microassistive arm can be achieved with consistency, provided the piercing is robotically driven. The model appears robust enough to allow testing of therapeutic strategies aimed at eliminating a retinal vein thrombus and its evolution over time.

Inhibition of Rho-Associated Kinase Prevents Pathological Wound Healing and Neovascularization After Corneal Trauma.

PURPOSE: To investigate the effect of AMA0526, a specific inhibitor of rho-associated protein kinase (ROCK), on corneal neovascularization (NV) and scarring in different in vitro and in vivo experimental models. METHODS: The effect of AMA0526 on cell viability, proliferation, and migration of human umbilical vein endothelial cells was determined. Its in vivo topical effect on NV was investigated in the corneal micropocket mouse model (bevacizumab as a control). The vessel length, clock hours, and NV area were measured on photographs. The effect of AMA0526 on pathological wound healing was investigated in the alkali burn mouse model (dexamethasone as a control). Corneas were scored for corneal opacity (CO) and NV after burn injury. Immunohistochemistry was performed to study inflammation, blood vessel density, and collagen III deposition after 7 days. RESULTS: ROCK inhibition significantly inhibited vascular endothelial cell proliferation and migration in vitro in a dose-dependent manner. In the micropocket model, NV was significantly reduced by AMA0526 (37% reduction, P < 0.05) comparable to bevacizumab. CO and NV were reduced after AMA0526, compared with the vehicle (P < 0.05 at all time points from day 3) after chemical burn. AMA0526 resulted in decreased inflammatory cell infiltration (26% reduction, P < 0.01), angiogenesis (47% reduction, P < 0.01), and collagen III deposition (27% reduction, P = 0.009) in the alkali burn model. AMA0526 administration showed results similar to those of dexamethasone with an additional antifibrotic effect. CONCLUSIONS: The ROCK inhibitor, AMA0526, efficiently inhibited angiogenesis in vitro, reduced CO and NV, and controlled the complete process of wound healing in vivo. These results warrant further investigation of the therapeutic potential of AMA0526 for corneal NV and scarring.

Design, synthesis, and biological evaluation of novel, highly active soft ROCK inhibitors.

ROCK1 and ROCK2 play important roles in numerous cellular functions, including smooth muscle cell contraction, cell proliferation, adhesion, and migration. Consequently, ROCK inhibitors are of interest for treating multiple indications including cardiovascular diseases, inflammatory and autoimmune diseases, lung diseases, and eye diseases. However, systemic inhibition of ROCK is expected to result in significant side effects. Strategies allowing reduced systemic exposure are therefore of interest. In a continuing effort toward identification of ROCK inhibitors, we here report the design, synthesis, and evaluation of novel soft ROCK inhibitors displaying an ester function allowing their rapid inactivation in the systemic circulation. Those compounds display subnanomolar activity against ROCK and strong differences of functional activity between parent compounds and expected metabolites. The binding mode of a representative compound was determined experimentally in a single-crystal X-ray diffraction study. Enzymes responsible for inactivation of these compounds once they enter systemic circulation are also discussed.

Inhibition of placental growth factor improves surgical outcome of glaucoma surgery.

Excessive post-operative wound healing with subsequent scarring frequently leads to surgical failure of glaucoma filtration surgery (trabeculectomy). We investigated the hypothesis that placental growth factor (PlGF) plays a role in post-operative scar formation, and that it therefore may be a target for improvement of filtration surgery outcome. ELISA experiments showed that PlGF levels were significantly increased in aqueous humour of glaucoma patients and after VEGF treatment, which may indicate an important contribution of this growth factor to wound healing after trabeculectomy. Using a mouse model of glaucoma filtration surgery, we were able to show that intracameral injection of a previously characterized anti-PlGF antibody (ThromboGenics NV) significantly improved surgical outcome by increasing bleb survival and bleb area. This was associated with a significant reduction in post-operative proliferation, inflammation and angiogenesis during the first post-operative days after surgery, and with a decrease in collagen deposition at later stages. Furthermore, inhibition of PlGF seemed to be more effective than anti-VEGF-R2 treatment in improving surgical outcome, possibly via its additional effect on inflammation. These results render PlGF an appealing target for ocular wound healing and point to potential therapeutic benefits of PlGF inhibition for the prevention of surgical failure.

Placental growth factor supports neuroendocrine tumor growth and predicts disease prognosis in patients.

Placental growth factor (PlGF), a VEGF-homolog implicated in tumor angiogenesis and adaptation to antiangiogenic therapy, is emerging as candidate target in malignancies. Here, we addressed the expression, function, and prognostic value of PlGF in neuroendocrine tumors (NETs). PlGF was determined in NET patients' sera collected retrospectively (n=88) and prospectively (n=87) using Roche-Elecsys and correlated with clinicopathological data. Tumoral PlGF was evaluated by immunohistochemistry, effects of PlGF on proliferation and migration in vitro were assessed using different NET cell lines and effects on tumor growth in vivo in orthotopic xenografts. Circulating and tumoral PlGF was elevated in patients with pancreatic NETs (pNETs) compared with control sera and respective healthy tissue. De novo PlGF expression occurred primarily in the tumor stroma, suggesting paracrine stimulatory circuits. Indeed, PlGF enhanced NET proliferation and migration in vitro and, conversely, neutralizing antibodies to PlGF reduced tumor growth in vivo. Elevated circulating PlGF levels in NET patients correlated with advanced tumor grading and were associated with reduced tumor-related survival in pNETs. Subsequent determinations confirmed and extended our observation of elevated PlGF levels in a prospective cohort of grade 1 and grade 2 pNETs (n=30) and intestinal NETs (n=57). In low-grade pNETs, normal circulating PlGF levels were associated with better survival. In intestinal NETs, circulating PlGF above median emerged as an independent prognostic factor for shorter time-to-progression in multivariate analyses. These data assign to PlGF a novel function in the pathobiology of NETs and propose PlGF as a prognostic parameter and therapeutic target.

Role of vascular endothelial growth factor in the pathophysiology of nonalcoholic steatohepatitis in two rodent models.

UNLABELLED: The pathophysiology of nonalcoholic steatohepatitis (NASH) should be approached as a multifactorial process. In several stages of NASH, a link between disease progression and hepatic microvasculature changes can be made. In this study we investigated the role of angiogenesis in two mouse models for NASH, and the effect of a preventive and therapeutic antiangiogenic treatment in a diet-induced mouse model for NASH. Protein and RNA levels of angiogenic and inflammatory factors were significantly up-regulated in the liver of C56BL/6 and db/db mice with NASH at different timepoints. To examine the effect of angiogenic factors on the disease progression of NASH, a prevention and treatment study was set up, blocking the placental growth factor (PlGF) or vascular endothelial growth factor receptor 2 (VEGFR2). Our study showed that treatment prevents the progression of NASH by attenuating steatosis and inflammation, both in a preventive and therapeutic setting, thereby confirming the hypothesis that angiogenic factors play an early role in the disease progression from steatosis to NASH. Anti-PlGF (αPlGF) did not significantly improve liver histology. Vascular corrosion casting showed a more disrupted liver vasculature in mice with NASH compared to controls. Treatment with αVEGFR2 showed an improvement of the liver vasculature. Moreover, fat-laden primary hepatocytes treated with αVEGFR2 stored significantly less lipids. CONCLUSION: Our results demonstrate that there is an increased expression of angiogenic factors in the liver in different mouse models for NASH. We found that VEGFR2 blockage attenuates steatosis and inflammation in a diet-induced mouse model for NASH in a preventive and therapeutic setting. Our findings warrant further investigation of the role of angiogenesis in the pathophysiology in NASH.

Serum protein N-glycan alterations of diethylnitrosamine-induced hepatocellular carcinoma mice and their evolution after inhibition of the placental growth factor.

Placental growth factor (PlGF) inhibition produced promising results in reducing tumor burden in a diethylnitrosamine (DEN)-induced mouse model for hepatocellular carcinoma (HCC). The aim of this study was to non-invasively assess the improved histology by performing a serum glycomic analysis. To elucidate the molecular mechanism underlying the observed glycomic effects, we investigated the transcription and expression of E26 transformation-specific sequence 1 (Ets-1), a transcription factor essential for the glycomic and angiogenic changes in malignant transformation, including its different phosphorylated forms that result from activation of the MAP kinase and a Ca(2+)-dependent pathway. In addition, three Ets-1-dependent glycosyltransferase genes, Mgat4a, Mgat4b, and Mgat5, were also evaluated. HCC was induced in mice by weekly injections with DEN for 16, 20, 25, and 30 w. In the treatment study, mice were injected with DEN for 25 w and subsequently treated with PlGF antibodies (5D11D4) for 5 w. Finally, PlGF-/- mice were injected with DEN for 20, 25, and 30 w. Serum N-glycans were analyzed with DNA sequencer-assisted fluorophore-assisted capillary electrophoresis and compared with histology. Maximum altered N-glycan phenotype was reached after 20 w of DEN-injections, i.e., when the first neoplastic lesions started to appear. 5D11D4-treatment improved the glycomic phenotype in that 7 of the 11 altered glycans tended to normalize. The PlGF-/- mice also showed a normalization trend, although not to the same extent of the treatment group. Number of Ets1, Mgat4a, Mgat4b, and Mgat5 transcripts increased considerably in DEN-injected mice, however, a non-significant decrease was observed after 5D11D4-treatment. On the protein level, 5D11D4-treatment had a prominent effect on the MAP kinase pathway with a significant p38 activation, yet independent of Ets-1 function.

The placental growth factor as a target against hepatocellular carcinoma in a diethylnitrosamine-induced mouse model.

BACKGROUND & AIMS: The placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family known to stimulate endothelial cell growth, migration and survival, attract angiocompetent macrophages, and determine the metastatic niche. Unlike VEGF, genetic studies have shown that PlGF is specifically involved in pathologic angiogenesis, thus its inhibition would not affect healthy blood vessels, providing an attractive drug candidate with a good safety profile. METHODS: We assess whether inhibition of PlGF could be used as a potential therapy against hepatocellular carcinoma (HCC), by using PlGF knockout mice and monoclonal anti-PlGF antibodies in a mouse model for HCC. In addition, the effect of PlGF antibodies is compared to that of sorafenib, as well as the combination of both therapies. RESULTS: We have found that both in a transgenic knockout model and in a treatment model, targeting PlGF significantly decreases tumor burden. This was achieved not only by inhibiting neovascularisation, but also by decreasing hepatic macrophage recruitment and by normalising the remaining blood vessels, thereby decreasing hypoxia and reducing the prometastatic potential of HCC. CONCLUSIONS: Considering the favourable safety profile and its pleiotropic effect on vascularisation, metastasis and inflammation, PlGF inhibition could become a valuable therapeutic strategy against HCC.

Increased expression of placental growth factor in high-grade endometrial carcinoma.

Placental growth factor (PlGF), a homolog of vascular endothelial growth factor (VEGF), exerts pleiotropic functions in cancer by affecting tumor cells as well as endothelial and inflammatory cells. Moreover, PlGF expression correlates with tumor stage, recurrence, metastasis and patient outcome in different types of cancer. Recently, administration of anti-PlGF therapy reduced tumor growth and metastasis in preclinical tumor models. In the present study, we evaluated the diagnostic and prognostic value of systemic and local expression of PlGF in primary endometrial carcinomas. PlGF levels in tumor lysates (n=128) and serum (n=88) of patients with primary endometrial cancer were determined using ELISA. PlGF mRNA expression in endometrial carcinoma tissues was quantified by quantitative qRT-PCR. Results were compared to endometrial cancer stage and grade. Systemic PlGF levels were not altered in patients with endometrial cancer (FIGO stage I-II-III) as compared to healthy controls. Only in FIGO stage IV patients, serum PlGF levels were slightly increased. Local PlGF mRNA and protein expression in endometrial tumors progressively increased with tumor grade. In endometrioid carcinomas, PlGF mRNA expression was significantly increased in endometrioid grade 3 tumors as compared to normal endometrial tissue. PlGF protein expression was significantly increased in endometrioid grade 2 and 3 carcinomas and in serous carcinomas as compared to normal endometrial tissue. Our study showed that systemic/serum PlGF levels cannot be used as a diagnostic or prognostic marker in endometrial cancer. However, the increased local expression of PlGF, primarily in high-grade carcinomas, underscores the possibility for preclinical assessment of anti-PlGF therapy in endometrial cancer.

Pharmacokinetics of ocriplasmin in vitreous.

PURPOSE: Ocriplasmin contains the active moiety of plasmin enzyme. At a physiologic pH, ocriplasmin is highly proteolytic and autolytic, limiting its duration of activity. Specific inhibitors of plasmin are present in the vitreous under normal and disease conditions and could affect its activity. Each may contribute to its mode of action. METHODS: Degradation characteristics were determined in porcine, human vitreous, and PBS under reducing conditions with different incubation periods between 0 and 24 hours on SDS-PAGE Tris-glycine gels. Residual activity was determined by spectrophotometry of p-nitroaniline release through hydrolysis of L-pyroglutamyl-L-phenylalanyl-L-lysine-p-nitroaniline hydrochloride. The presence of endogenous inactivators of ocriplasmin in human vitreous was determined in a series of vitreous samples using an ELISA specific for alpha(2)-antiplasmin, antithrombin, and antitrypsin. RESULTS: Degradation productions from autolysis are similar between vitreous and PBS with a significant prolongation of the effect in vitreous. Both follow a nonlinear pattern over time. The degradation corresponds best to a second-order kinetic process. The resulting rate constants were 207 ± 60 M(-1) s(-1) in PBS, 81 ± 15 M(-1) s(-1) in porcine vitreous, and 195 M(-1) s(-1) in human vitreous natural inhibitors were identified in samples of donor vitreous. Amounts differed significantly between samples, which may help explain the observed variability in human subjects. CONCLUSIONS: Ocriplasmin is autolytic in vitreous. Biologic activity extends to several days following injection. The exact duration will vary based on the presence and concentration of serine protease inhibitors.

Inhibition of the placental growth factor decreases burden of cholangiocarcinoma and hepatocellular carcinoma in a transgenic mouse model.

OBJECTIVES: Hepatocellular carcinoma and cholangiocarcinoma form the majority of primary hepatic tumours and are the third most common cause of cancer-related deaths. These liver tumours rapidly outgrow their vascular supply and become hypoxic, resulting in the production of hypoxia inducible factors and triggering the angiogenic switch. Therefore, inhibiting angiogenesis has proven to be a valuable therapeutic strategy in hepatocellular carcinoma, yet less is known about its use in cholangiocarcinoma. In this study, we assess whether inhibiting the placental growth factor (PlGF) could offer a therapeutic option in mice with hepatocellular carcinoma and cholangiocarcinoma. PlGF is a homologue of the vascular endothelial growth factor, which is only involved in pathological angiogenesis, therefore, its inhibition does not induce adverse effects. METHODS: We have used a chemically induced transgenic mouse model in which both hepatocellular carcinoma and cholangiocarcinoma develop after 25 weeks and are treated with murine monoclonal antibodies targeting PlGF. RESULTS: This study has shown for the first time that inhibiting PlGF decreases the burden of cholangiocarcinoma, by affecting both angiogenesis and inflammation. CONCLUSION: The use of monoclonal antibodies targeting PlGF could thus offer a potential systemic treatment for patients who suffer from primary liver tumours.

Placental growth factor contributes to bronchial neutrophilic inflammation and edema in allergic asthma.

Placental growth factor (PlGF) and its receptor vascular endothelial growth factor receptor 1 (VEGFR1) play an important role in pathological conditions related to angiogenesis, vascular leakage, and inflammation. This study investigated their contributions to inflammation and the formation of edema in allergic asthma. The expression of PlGF and VEGFR1 was measured in induced sputum of patients with asthma (n = 11) and healthy subjects (n = 11), and in bronchial biopsies of house dust mite (HDM)-allergic patients stimulated with HDM allergens. The effects of the endonasal administration of human PlGF-2 and PlGF deficiency on inflammation and edema were evaluated in a murine model of allergic asthma. The migration of human neutrophils in response to hPlGF-2 was tested in vitro. The expression of PlGF and VEGFR1 was significantly higher in the sputum of patients with asthma, and in Der p 1-induced PlGF in biopsies from HDM-allergic patients. PlGF was increased in the bronchi of ovalbumin (OVA)-challenged mice compared with control mice (65 ± 17 pg/mg versus 18 ± 1 pg/mg, respectively; P < 0.01), and VEGFR1 was expressed in bronchial epithelium, endothelium (control mice), and inflammatory cells (OVA-challenged mice). The endonasal instillation of hPlGF-2 in wild-type, OVA-challenged mice led to an increase in bronchial neutrophils, lung tissue wet/dry ratio, and IL-17. PlGF-deficient mice showed lower numbers of BAL-infiltrating neutrophils, a reduced lung wet/dry ratio, and lower production of IL-17, macrophage inflammatory protein-2, and granulocyte chemotactic protein-2/LPS-induced chemokine compared with wild-type, OVA-challenged mice. hPlGF-2 induced the migration of human neutrophils in vitro in a VEGFR1-dependent way. PlGF and its receptor VEGFR1 are up-regulated in allergic asthma and play a proinflammatory role by inducing tissue edema, and increasing tissue neutrophilia and the production of IL-17.

Monoclonal antibody TB-403: a first-in-human, Phase I, double-blind, dose escalation study directed against placental growth factor in healthy male subjects.

BACKGROUND: TB-403 (RO5323441) is a humanized monoclonal antibody directed against placental growth factor (PlGF). Preclinical studies have demonstrated that targeting PlGF can result in significant inhibition of tumor growth and metastasis. OBJECTIVES: The purpose of this study was to assess the safety profile, tolerability, and pharmacokinetics of TB-403, developed for the treatment of solid tumors. METHODS: Healthy male subjects were exposed to a single intravenous infusion of TB-403 or placebo. Blood samples for hematology, clinical chemistry, coagulation factors, and urinalysis were collected; vital signs and ECGs were recorded; and serial blood samples were drawn for pharmacokinetic and immunogenicity measurements and circulating levels of pharmacodynamics markers PlGF and (VEGF) vascular endothelial growth factor. Sixteen subjects received either placebo or TB-403 at doses ranging from 0.3 to 5.0 mg/kg. RESULTS: Mild (grade 1 or 2) nasopharyngitis, headache, neck pain, and joint pain were the most frequently reported adverse events (AEs). There were no serious AEs in the study, and none of the AEs led to withdrawal. None of the safety laboratory assessments was considered clinically significant, and none was reported as an AE. There were no apparent differences in terms of safety profiles among the 3 dose levels of active treatment compared with placebo. Clearance, volume of distribution, and terminal t(½) (mean values) for TB-403 in all 3 cohorts were in the range of 4.2 to 4.9 (mL/d/kg), 56 to 79 (mL/kg), and 8 to 13 (days), respectively. CONCLUSION: The highest dose of TB-403 (5.0 mg/kg) was well tolerated in this study of a single intravenous infusion to healthy males. This result allowed a higher starting dose level in a subsequent Phase I study in cancer patients, the patient population for which this antibody is developed.

The role of different VEGF isoforms in scar formation after glaucoma filtration surgery.

Vascular endothelial growth factor (VEGF) plays an important role in both physiological and pathological angiogenesis. Our previous studies showed a differential role of VEGF isoforms in retinal physiological angiogenesis. We also demonstrated that non-selective inhibition of VEGF by bevacizumab had a beneficial effect on surgical outcome after glaucoma filtration surgery by reducing angiogenesis as well as fibrosis. However, the function of the VEGF isoforms in pathological angiogenesis and wound healing in the eye still remains unidentified. This study was designed to elucidate the differential roles of VEGF isoforms in scar formation after trabeculectomy. Furthermore, we also investigated whether pegaptanib (Macugen™, Pfizer), an aptamer which specifically blocks VEGF(165), could improve surgical outcome by reducing postoperative scarring. VEGF-R2 and neuropilin-1 (NRP-1) expression was analyzed in vitro by RT-PCR, and were found to be expressed at higher levels in human umbilical vein endothelial cells (HUVEC) as compared to Tenon fibroblasts (TF). The effect of the different VEGF isoforms (VEGF(121), VEGF(165) and VEGF(189)) and pegaptanib on cell proliferation was determined via WST-1 assay. Endothelial cell proliferation was stimulated after addition of VEGF(121) and VEGF(165), whereas VEGF(121) and VEGF(189) increased fibroblast growth. These effects on proliferation were associated with an activation of the ERK pathway, as revealed using the TransAM c-Myc assay. Inhibition of the ERK pathway, by PD98059 administration, significantly reduced VEGF isoform induced cell growth. A dose-dependent reduction of endothelial cell proliferation was observed after pegaptanib administration, while only the highest dose was able to inhibit fibroblast growth. Next, the in vivo effect of pegaptanib was investigated in a rabbit model of trabeculectomy. The surgical outcome was evaluated by performing clinical investigations (IOP, bleb area, height and survival), as well as histomorphometric analyses of angiogenesis (CD31), inflammation (CD45) and fibrosis (Sirius Red). A single postoperative application of pegaptanib had a beneficial impact on surgical outcome, mainly by reducing angiogenesis, but not inflammation or collagen deposition. Repeated injections slightly improved surgical outcome, but again solely by reducing angiogenesis. In summary, our results revealed that the VEGF isoforms play a differential role in ocular wound healing: VEGF(165) and VEGF(121) predominantly affect blood vessel growth, whereas VEGF(189) is rather involved in fibrosis, an important process in wound healing.

Inhibition of placental growth factor activity reduces the severity of fibrosis, inflammation, and portal hypertension in cirrhotic mice.

UNLABELLED: Placental growth factor (PlGF) is associated selectively with pathological angiogenesis, and PlGF blockade does not affect the healthy vasculature. Anti-PlGF is therefore currently being clinically evaluated for the treatment of cancer patients. In cirrhosis, hepatic fibrogenesis is accompanied by extensive angiogenesis. In this paper, we evaluated the pathophysiological role of PlGF and the therapeutic potential of anti-PlGF in liver cirrhosis. PlGF was significantly up-regulated in the CCl(4) -induced rodent model of liver cirrhosis as well as in cirrhotic patients. Compared with wild-type animals, cirrhotic PlGF(-/-) mice showed a significant reduction in angiogenesis, arteriogenesis, inflammation, fibrosis, and portal hypertension. Importantly, pharmacological inhibition with anti-PlGF antibodies yielded similar results as genetic loss of PlGF. Notably, PlGF treatment of activated hepatic stellate cells induced sustained extracellular signal-regulated kinase 1/2 phosphorylation, as well as chemotaxis and proliferation, indicating a previously unrecognized profibrogenic role of PlGF. CONCLUSION: PlGF is a disease-candidate gene in liver cirrhosis, and inhibition of PlGF offers a therapeutic alternative with an attractive safety profile.

Characterization of a stabilized form of microplasmin for the induction of posterior vitreous detachment.

PURPOSE: To investigate the stability and safety of a diluted acidified form of microplasmin and its ability to induce a posterior vitreous detachment (PVD) following intravitreal injection in post-mortem porcine eyes. METHODS: Microplasmin diluted in normal saline (NS) and balanced salt solution (BSS+) was assayed for residual activity by hydrolysis of the chromogenic substrate Glu-Phe-Lys-pNA. Residual activity on vitreous was determined by injecting aliquots of microplasmin reconstituted in balanced salt solution (BSS+) or normal saline (NS) kept at room temperature (RT) for up to 1 hr, then injected in aliquots of porcine vitreous and incubated for 2 hr at 37°C. The breakdown products were submitted to SDS Page electrophoresis and compared to determine the level of enzymatic activity. Pig eyes were incubated with graded concentrations of microplasmin 0.625, 1.25, or 2.50 mg/mL reconstituted in BBS+ or NS. Morphologic alterations and the ability to induce a PVD was assessed by light and electron microscopy. RESULTS: Microplasmin's enzymatic activity in an in vitro assay in BSS+ was 70% of its baseline value after 30 min, and about 50% after 60 min at RT. The corresponding effect on degradation of vitreous gel was 60 and 40% baseline at 30 and 60 min. There was no loss of activity in the microplasmin diluted in normal saline over this time period. Dilution of acidified microplasmin in normal saline did not lead to structural changes within the retina. A dose dependent PVD was observed in eyes treated with microplasmin diluted in NS. CONCLUSIONS: Acidified (stabilized) microplasmin has the same intraocular activity profile as microplasmin at a neutral pH. Better retention of activity at room temperature makes it a better candidate for use in clinical practice.

Anti-placental growth factor reduces bone metastasis by blocking tumor cell engraftment and osteoclast differentiation.

Treatment of bone metastases is largely symptomatic and is still an unmet medical need. Current therapies mainly target the late phase of tumor-induced osteoclast activation and hereby inhibit further metastatic growth. This treatment method is, however, less effective in preventing initial tumor engraftment, a process that is supposed to depend on the bone microenvironment. We explored whether bone-derived placental growth factor (PlGF), a homologue of vascular endothelial growth factor-A, regulates osteolytic metastasis. Osteogenic cells secrete PlGF, the expression of which is enhanced by bone-metastasizing breast tumor cells. Selective neutralization of host-derived PlGF by anti-mouse PlGF (alphaPlGF) reduced the incidence, number, and size of bone metastases, and preserved bone mass. alphaPlGF did not affect metastatic tumor angiogenesis but inhibited osteoclast formation by preventing the upregulation of the osteoclastogenic cytokine receptor activator of NF-kappaB ligand in osteogenic cells, as well as by blocking the autocrine osteoclastogenic activity of PlGF. alphaPlGF also reduced the engraftment of tumor cells in the bone and inhibited their interaction with matrix components in the metastatic niche. alphaPlGF therefore inhibits not only the progression of metastasis but also the settlement of tumor in the bone. These findings identify novel properties of PlGF and suggest that alphaPlGF might offer opportunities for adjuvant therapy of bone metastasis.

Tolerability and pharmacokinetics of TB-402 in healthy male volunteers.

BACKGROUND: TB-402, a human monoclonal antibody that partially inhibits Factor VIII activity (FVIII:C), is being developed as a long-acting antithrombotic agent. OBJECTIVES: The primary goal of this study was to investigate the tolerability of TB-402 in healthy male volunteers. Secondary objectives were to determine the pharmacokinetics and pharmacodynamics of TB-402. METHODS: In this ascending-dose study, healthy subjects aged 18 to 45 years were randomly assigned in a 2:1 ratio to receive TB-402 administered as a single intravenous bolus at 0.015, 0.1, 0.5, 2.5, 12.5, 37.5, 188, 620, or 1860 microg/kg or matching inactive vehicle (placebo). An older group (55-75 years) was also administered the highest dose that was well tolerated in the younger group (1860 microg/kg). Adverse events (AEs) were obtained from spontaneous reporting and from answers to nonleading questions asked by the principal investigator and study staff during follow-up visits on days 4, 7 (+/-1 day), 14 (+/-1 day), 21 (+/-2 days), 28 (+/-3 days), 42 (+/-3 days), and 56 (+/-3 days) after TB-402 administration. AEs were monitored up to the last study visit on day 56 after the administration of TB-402 or placebo, with special attention to bleeding events. The pharma-codynamic assessment of TB-402 included changes in FVIII:C, activated partial thromboplastin time (APTT), and prothrombin time (PT). RESULTS: The study enrolled 56 subjects (mean ages: younger group, 28 years [range, 20-45 years]; older group, 65 years [range, 58-76 years]; weight, 79 kg [range, 60-104 kg] and 81 kg [range, 64-94 kg], re-spectively). Thirty-one of the 38 subjects who received TB-402 (82%) experienced a total of 85 treatment-emergent AEs (TEAEs), and 14 of 18 subjects who received placebo (78%) experienced 35 TEAEs. A total of 34 bleeding events were reported in 13 of 38 subjects (34%) who received TB-402 and 7 of 18 subjects (39%) who received placebo. Most common AEs reported in subjects who received TB-402 were headache (11 [29%]), vessel puncture-site hematoma (7 [18%]), and traumatic hematoma (5 [13%]); with placebo, these AEs were vessel puncture-site hematoma (4 [22%]), headache (3 [17%]), vasovagal reaction (3 [17%]), and hematuria (3 [17%]). No serious AEs considered to be related to TB-402 were reported, and no dose-dependent increases in bleeding events were observed. On pharmacokinetic analysis of TB-402, the t(1/2) values across doses were 22.9 days (age 18-45 years) and 19.5 days (age 55-75 years). TB-402 was associated with a reduction in FVIII:C over a period of approximately 48 hours in the d37.5-microg/kg dose groups. TB-402 was associated with a prolonged APTT at doses >or=2.5 microg/kg approximately 1.1-1.2-fold predose APTT). Administration of a higher dose of TB-402 was associated with an extended duration of APTT prolongation. No significant effect on PT was found. CONCLUSIONS: In this study in healthy male volunteers, TB-402 was well tolerated in the population studied. Based on the findings from this study, the long t(1/2) of TB-402 may allow a pharmacodynamic effect over a prolonged period after single-dose administration. Further trials are needed to address the tolerability and efficacy of this agent in preventing thromboembolism. Clinicaltrials.gov identifier: NCT00612196.

Differential vitreous dye diffusion following microplasmin or plasmin pre-treatment.

PURPOSE: Plasmin and microplasmin are related enzymes that differ mainly in size. The differential effect of plasmin and microplasmin on vitreous structure, protein degradation, and dye diffusion through porcine vitreous was evaluated. METHODS: The enzymatic effect was examined using a number of approaches on fresh porcine eyes: (1) structural integrity of vitreous after a 2-hr incubation using the electron microscope (EM); (2) effect on soluble proteins within the vitreous using gel electrophoresis after incubation at various time points over a 24-hr period; (3) fluorescein dye diffusion within the vitreous cavity measured over a 1-hr period following a 2-hr incubation. The chosen enzymatic activities for plasmin 0.5 IU and microplasmin 125 microg were within the clinical range, and were chosen for equipotence. A saline control was also used in all experiments. RESULTS: Significant structural changes were seen with both microplasmin and plasmin when examined by EM. Gel electrophoresis showed that microplasmin and plasmin digested the same proteins, mainly molecular weights above 50 kDa. The enzymatic effect was noticeable earlier in microplasmin-treated eyes and was more significant by the end of the incubation period. Differential fluorescein diffusion rates were seen between normal saline, plasmin, and microplasmin within the vitreous cavity. The greatest diffusion rate was seen with microplasmin and was statistically significantly higher than plasmin. CONCLUSION: Microplasmin and plasmin have a similar enzymatic effect on vitreous. However, an equipotent amount of microplasmin appears to have a more extended effect on vitreous gel. This may, in part, be related to its smaller size allowing it to diffuse more readily through the vitreous matrix.