For many years, researchers have dreamed of a magical lens that can deliver drugs to the eye consistently in a sustained-release manner. For decades, manufacturers have tried to bring this dream to reality by developing ingenius ways to mitigate the many limitations in contact lens delivery systems.
Are we any closer to a perfectly effective drug delivery system using a lens in tandem with enhanced technology? Or will an entirely new delivery system take over?
This year at the annual meeting of the Association for Research in Vision and Ophthalmology (ARVO), a number of fascinating abstracts addressed the topic of drug delivery and novel ways to deliver drugs to the eye. The systems/devices for ocular drug delivery range from therapeutic agents formulated in nanoparticles to devices that release a drug upon irradiation with low (safe) levels of UV light to drug-eluting intraocular lenses that bypass the ocular surface entirely.
Drug Delivery Systems of the Future?
Below are thumbnail sketches of a few of the promising studies in drug delivery from thisw year’s ARVO:
• The UV-induced nanoparticle platform has the potential to deliver a wide range of molecules (e.g., hydrophobic drugs and proteins) for at least 12 weeks post-injection.
Poster D0061, Shining a Light on Drug Delivery: On-Demand Light-triggered Release of Payload to the Eye, Nguyen Huu VA, Luo J, Zhu J, et al.
• Further research in developing intraocular lenses that release one- and two-layer films to function as intraocular delivery systems seems likely, following an initial pilot report this year. Development of films based on organic polymers and dexamethasone for direct delivery via intraocular lenses may be feasible.
PosterD0062: First Steps Towards a Drug Eluting Intraocular Lens, Lamprogiannis L, Karamitsos A, Logothetidis S, et al.
• Another novel device—using a conjunctival ring—designed for drug delivery to the eye was evaluated. No remarkable side effects were observed in animal experiments and delivery of antibiotics and steroids appears to be feasible even to posterior eye tissues.
Poster D0101, Safety Evaluation of Novel Drug Delivery Device, the Conjunctival Ring, Kinoshito S, Noda K, et al.
• Punctal plugs may be another novel way to deliver drugs to the anterior eye. Corticosteroids were released from punctal plugs on the basis of aqueous solubility in another abstract. The studies demonstrate that plugs containing a high dose of a given steroid will release the same amount per day and will release drug over a longer period of time.
Poster D0091, In Vivo Drug Release of Low Solubility Drugs from Biodegradable Hydrogel Punctal Plugs, McGrath M, Blizzard C, Desai A, et al.
• Because only about 15% of drug doses applied to the eye stay long enough to be effective, drug carriers for prolonged retention make sense. Adherence time was found to be greatly increased using DNA-based nanoparticles that have a high affinity for the cornea. Ideally, a lower concentration of drug may reduce side effects and improve compliance.
Poster D0087, DNA-Based Nanoparticles as a Potential Drug Carrier for the Treatment of Anterior Segment Diseases, Schnichels S, Willem J, Strudel L, et al.
• Increasing contact time and/or drug adherence to the surface of the eye has several benefits. Phenylboronic acid (PBA), a synthetic ligand, may be useful in enhancing muco-adhesion that improves drug delivery to the eye by enhancing site-specific targets and improving bioavailability. PBA was successfully incorporated into pHEMA, PVP and pDMA hydrogels, and demonstrated good muco-adhesion and drug release with good binding potential.
Poster D0074, Development of Phenylboronic Acid Containing Mucoadhesive Hydrogel Materials for Ophthalmic Drug Delivery Applications, Liu L, Sheardown H.
• Micro-engineered delivery systems have the potential to administer a precise concentration—in a sustained fashion—of a drug with a single injection to the ocular surface. This abstract highlights a system that encapsulates a drug within a polymer delivery system using a process that produces monolithic encapsulates. These drug containing microparticles may be a feasible concept for replacement of eye drops delivered multiple times each day.
Poster D0075, Single Administration Sustained Release Formats for Administration of Ophthalmic Medications to the Ocular Surface, Cornea and Anertior Chamber, Barman S, Barman K, Ward K.
Perhaps we have moved past the thought of delivering a consistent dose of drug(s) over time by using a contact lens. These abstracts, at the very least, will spark additional studies. And, who knows—some of these technologies may be ready for prime time in the near future.