The role of blood-ocular barrier transporters in retinal drug disposition: an overview

Importance of the field: Delivery of drugs to the retina remains a major challenge which needs to be addressed urgently because retinal disorders are leading causes of visual impairment and significantly affect a patient's quality of life. Systemic drug administration is one possible route for treating retinal disorders; however, retinal transfer of drugs from the circulating blood is strictly regulated by two blood-ocular barrier systems, the blood-aqueous barrier and the blood-retinal barrier. Areas covered in this review: This review summarizes the latest biological research regarding blood-ocular barrier drug transporters. What the reader will gain: The blood-ocular barrier sites and their respective roles in aqueous humor dynamics and retinal homeostasis are briefly presented. The potential impact of ATP-binding cassette (ABC) and solute carrier (SLC) drug transporters, such as ABCB, ABCC, ABCG, SLC7, SLC16, SLC19, SLCO/SLC21A, SLC22A and SLC29 transporters, on the permeability of drugs across the blood-ocular barriers is then illustrated. Take home message: As more information becomes available regarding the blood-ocular barrier transporters, we may be able to design simpler and more effective routes for drug delivery to the retina and, consequently, improve the treatment of retinal diseases.