Topical Delivery of Avastin to the Posterior Segment of the Eye In Vivo Using Annexin A5‐associated Liposomes

Effective delivery to the retina is presently one of the most challenging areas in drug development in ophthalmology, due to anatomical barriers preventing entry of therapeutic substances. Intraocular injection is presently the only route of administration for large protein therapeutics, including the anti‐Vascular Endothelial Growth Factors Lucentis (ranibizumab) and Avastin (bevacizumab). Anti‐VEGFs have revolutionised the management of age‐related macular degeneration and have increasing indications for use as sight‐saving therapies in diabetes and retinal vascular disease. Considerable resources have been allocated to develop non‐invasive ocular drug delivery systems. It has been suggested that the anionic phospholipid binding protein annexin A5, may have a role in drug delivery. In the present study we demonstrate, using a combination of in vitro and in vivo assays, that the presence of annexin A5 can significantly enhance uptake and transcytosis of liposomal drug carrier systems across corneal epithelial barriers. This system is employed to deliver physiologically significant concentrations of Avastin to the posterior of the rat eye (127 ng/g) and rabbit retina (18 ng/g) after topical application. Our observations provide evidence to suggest annexin A5 mediated endocytosis can enhance the delivery of associated lipidic drug delivery vehicles across biological barriers, which may have therapeutic implications.