How are we improving the delivery to back of the eye? Advances and challenges of novel therapeutic approaches

ABSTRACT

Introduction: Drug delivery to the back of the eye requires strategic approaches that guarantee the long-term therapeutic effect with patient compliance. Current treatments for posterior eye diseases suffer from significant challenges including frequent intraocular injections of anti-VEGF agents and related adverse effects in addition to the high cost of the therapy.

Areas covered: Treatment challenges and promising drug delivery approaches for posterior segment eye diseases, such as age-related macular degeneration (AMD) are summarized. Advances in the development of several nanotechnology-based systems, including stimuli-responsive approaches to enhance drug bioavailability and overcome existing barriers for effective ocular delivery are discussed. Stem cell transplantation and encapsulated cell technology (ECT) approaches to treat posterior eye diseases are elaborated.

Expert opinion: There are several drug delivery systems demonstrating promising results. However, a better understanding of ocular barriers, disease pathophysiology, and drug clearance mechanisms is required for better therapeutic outcomes. The stem cell transplantation strategy and ECT approach provide positive results in AMD therapy, but there are a number of challenges that must be overcome for long-term efficiency. Ultimately, there are numerous multidimensional challenges to cure vision problems and a collaborative approach among scientists is required.

KEYWORDS:

• Ocular barriers
• posterior eye diseases
• age-related macular degeneration
• drug delivery
• stimuli-responsive
• stem cell transplantation
• encapsulated cell technology
• nanocarriers
• nanotechnology

Article highlights

• Drug delivery to the eye is challenging. Conventional formulations are unable to efficiently deliver a drug into the back of the eye due to the presence of complex barriers, elimination mechanisms, thus, resulting in a low ocular drug bioavailability.

• Various routes of drug administration to the back of the eye, elimination pathways, delivery barriers, advantages and challenges are elaborated.

• At present, frequent intravitreal injections are the preferred method for the treatment of posterior eye diseases but have several side effects and high treatment costs.

• The current treatment options and major challenges for AMD and future therapeutics have been described.

• Several nanosystems in addition to their clinical applications for the back of eye diseases emphasizing on AMD are discussed. Furthermore, the current status and clinical applications of ocular implants are reviewed. Stimuli-responsive NCs for back of the eye diseases are also summarized.

• Retinal cell transplantation using stem cells sources and ECT approaches; their challenges with future implications for the retinal diseases are elaborated.

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Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Additional information

Funding

This study is supported by NIH R01EY09171 and NIH R01EY10659.