BACKGROUNDHereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular dysplasia and severe, recurrent epistaxis is a common clinical phenotype associated with HHT. An intranasal treatment regime of diluted Avastin™ (Bevacizumab; recombinant humanized anti-vascular epithelial growth factor immunoglobin G1) using apulsatile nasal irrigator has proven efficacious in clinical practice. However, concerns regarding the stability of Avastin™ following dilution and prolonged storage in standard containers used for drug delivery, such as polyethylene bottles, have so far prevented a more widespread clinical use. Compatibility with the preservative benzalkonium chloride was also unknown.OBJECTIVEThis study aimed at determining, whether dilution, prolonged refrigerated storage and the presence of the preservative benzalkonium chloride - as required for novel Avastin™ formulations - affected the biochemical and electrochemical properties of the drug.METHODSWe performed a detailed biochemical and electrochemical analysis of Avastin™, including native and sodium dodecyl sulfate polyacrylamide gel electrophoresis, enzyme-linked immunosorbent assay and isoelectric focusing.RESULTSWe did not detect any evidence of degeneration or aggregation following dilution and prolonged, refrigerated storage or from the presence of benzalkonium chloride. All biochemical and electrochemical properties of Avastin™ after dilution and prolonged, refrigerated storage were undistinguishable from control.CONCLUSIONSOur data provide important insight into the stability of Avastin™ and allow the consideration of novel Avastin™ formulations, including its use in a metered-dose nasal spray for the treatment of HHT and other applications.