PEGylation Potentiates the Effectiveness of an Antagonistic Peptide That Targets the EphB4 Receptor with Nanomolar Affinity

The EphB4 receptor tyrosine kinase together with its preferred ligand, ephrin-B2, regulates a variety of physiological and pathological processes, including tumor progression, pathological forms of angiogenesis, cardiomyocyte differentiation and bone remodeling. We previously reported the identification of TNYL-RAW, a 15 amino acid-long peptide that binds to the ephrin-binding pocked of EphB4 with low nanomolar affinity and inhibits ephrin-B2 binding. Although ephrin-B2 interacts promiscuously with all the EphB receptors, the TNYL-RAW peptide is remarkably selective and only binds to EphB4. Therefore, this peptide is a useful tool for studying the biological functions of EphB4 and for imaging EphB4-expressing tumors. Furthermore, TNYL-RAW could be useful for treating pathologies involving EphB4-ephrin-B2 interaction. However, the peptide has a very short half-life in cell culture and in the mouse blood circulation due to proteolytic degradation and clearance by the kidneys and reticuloendothelial system. To overcome these limitations, we have modified TNYL-RAW by fusion with the Fc portion of human IgG1, complexation with streptavidin or covalent coupling to a 40 KDa branched polyethylene glycol (PEG) polymer. These modified forms of TNYL-RAW all have greatly increased stability in cell culture, while retaining high binding affinity for EphB4. Furthermore, PEGylation most effectively increases peptide half-life in vivo. Consistent with increased stability, submicromolar concentrations of PEGylated TNYL-RAW effectively impair EphB4 activation by ephrin-B2 in cultured B16 melanoma cells as well as capillary-like tube formation and capillary sprouting in co-cultures of endothelial and epicardial mesothelial cells. Therefore, PEGylated TNYL-RAW may be useful for inhibiting pathological forms of angiogenesis through a novel mechanism involving disruption of EphB4-ephrin-B2 interactions between endothelial cells and supporting perivascular mesenchymal cells. Furthermore, the PEGylated peptide is suitable for other cell culture and in vivo applications requiring prolonged EphB4 receptor targeting

The Safety of Tranexamic Acid in Total Joint Arthroplasty: A Direct Meta-Analysis

© 2018 Elsevier Inc. Background: Tranexamic acid (TXA) is effective in reducing blood loss in total joint arthroplasty (TJA), but concerns still remain regarding the drug\u27s safety. The purpose of this direct meta-analysis was to evaluate and establish a basis for the safety recommendations of the combined clinical practice guidelines on the use of TXA in primary TJA. Methods: A search was completed for studies published before July 2017 on TXA in primary TJA. We performed qualitative and quantitative homogeneity testing and a direct comparison meta-analysis. We used the American Society of Anesthesiologists (ASA) score of 3 or greater as a proxy for patients at higher risk for complications in general and performed a meta-regression analysis to investigate the influence of comorbidity burden on the risk of arterial thromboembolic event and venous thromboembolic event (VTE). Results: Topical, intravenous, and oral TXA were not associated with an increased risk of VTE after TJA. In addition, meta-regression demonstrated that TXA use in patients with an ASA status of 3 or greater was not associated with an increased risk of VTE after total knee arthroplasty. Conclusion: Although most studies included in our analysis excluded patients with a history of prior thromboembolic events, our findings support the lack of evidence of harm from TXA administration in patients undergoing TJA. Moderate evidence supports the safety of TXA in patients undergoing total knee arthroplasty with an ASA score of 3 or greater. The benefits of using TXA appear to outweigh the potential risks of thromboembolic events even in patients with a higher comorbidity