Conference report highlights new research into drug delivery to treat eye disease

Researchers are investigating microneedles, nanoparticles and polymer carriers as potential new techniques to combat the leading cause of visual impairment and blindness in the United States, according to a report from the Third Annual ARVO/Pfizer Ophthalmics Research Institute Conference. The report (http://www.iovs.org/cgi/content/full/49/11/4712) includes summaries from seven sessions on techniques for ocular drug delivery to the posterior segment of the eye and includes the findings of and opinions of more than 30 top ophthalmic researchers, brought together by the ARVO Foundation for Eye Research. The article in the November issue of Investigative Opthalmology & Visual Science defines the current research and the future needs for ocular drug delivery.

Diseases of the posterior segment of the eye are responsible for the majority of visual impairment and blindness cases in the United States, according to George Williams, MD. Until recently, these diseases were primarily treated with surgery, but recent developments in drug therapies have either replaced or complemented surgery.

But the challenge lies in delivering the drugs. Topical delivery such as ointments and drops are fairly ineffective, and delivery via intravitreous injection (an injection into the fluid in the behind the lens in the eye) can be hard on the patient. According to the report, "Improved drug delivery technologies that provide optimal pharmacokinetics, dose intervals and less invasive routes of administration are needed."

During the two-day event, John Heckenlively, MD, joined Jayakrishna Ambarti, MD, in a session on animal models of posterior ocular diseases. Allan Hoffman, ScD, discussed the design of polymer carriers for intracellular delivery of biomolecular drugs, such as peptides, proteins and nucleic acid drugs. His group is focused on using a family of acid-sensitive polymers to help deliver one of the latest drugs, silencing RNA (siRNA).

Another group of presenters discussed the use of nanoparticles, microbeads and microneedles. Mansoor M. Amiji, PhD, said that nanoparticles can help overcome barriers to drug delivery from the organ level to the subcellular level. Another research laboratory was investigating the effectiveness of hollow and solid microneedles that penetrate only hundreds of micrometers into the cornea or sclera to deliver drugs.

A safer alternative to direct intravitreous injections might be transscleral delivery into the vitreous using subconjunctival injections, said Michael Robinson, MD, adding that researchers needed a clear understanding of the dynamic barriers for the technique to work in treating retinal diseases. Another researcher in this area, Dayle H. Geroski, PhD, suggested that the relatively high permeability of the sclera offers great potential for transscleral drug delivery, especially for administration to the posterior part of the eye.

Other research focused on photodynamic therapy, which uses a photosensitizer agent that localizes more or less selectively to the target tissue and is activated by light, triggering chemical reactions that injure the target tissue.

Source: Association for Research in Vision and Ophthalmology