Comment on “Topical Delivery of Avastin to the Posterior Segment of the Eye In Vivo Using Annexin A5‐Associated Liposomes”: Topical Liposomal Bevacizumab Results in Negligible Retinal Concentrations

The previously published report suggests that liposomes, functionalized with annexin‐5, can deliver bevacizumab to the retina after topical administration as eyedrops. Topical delivery of bevacizumab would be an attractive alternative to the current treatment that involves monthly intravitreal injections to the eye. In this Comment, the retinal concentrations of topically applied liposomal bevacizumab are compared to the levels reached after intravitreal injections. The comparison reveals that the topical liposomal delivery results in retinal bevacizumab concentrations that are about 3–5 orders of magnitude below the lowest bevacizumab concentrations during clinical treatment with intravitreal injections. Major improvement is needed before topical bevacizumab delivery can be considered clinically feasible. This Comment includes critical discussion on previously published research on retinal delivery of bevacizumab with topically applied liposomes. The Comment indicates that the retinal bevacizumab levels after topical delivery are in fact several orders of magnitude below clinically relevant concentrations.