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Researchers look to fill need for longer duration medications, delivery systems
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KOLOA, Hawaii — Because a longer duration medication that delivers therapy without creating therapeutic peaks and troughs is a desirable goal, a variety of approaches to improving drug delivery to the posterior segment are being researched, according to a speaker here.
Intravitreal injections or use of sustained release solid implant intravitreal devices are the most common techniques currently employed, William F. Mieler, MD, Professor and Vice-Chairman, Department of Ophthalmology & Visual Sciences, University of Illinois, Chicago, told colleagues at Retina 2014.
“We all recognize the multitude of injections we give for age-related macular degeneration. … While we’re all incredibly grateful that we’re able to help these patients today, we certainly wish there was a longer duration medication that would make the number of injections less frequent,” Mielersaid.
However, Mieler said, the determination of timing and dosing are ongoing challenges. Timing and dosing should deliver a consistent, steady level of drug concentration that avoids therapeutic peaks and troughs. Also important is the location of the implant, which could greatly impact drug concentrations and their potential side effects, he said. Potential delivery sites are topical, systemic, intravitreal and transscleral.
There are advantages to periocular delivery, Mieler said. Due to large surface area and fibrous tissue, sclera offers the ideal site where drug can reach the posterior segment transsclerally. The choroid (via systemic circulation) and the cornea (via tear film) are potential sites of drug delivery as well, he said. However, molecules up to approximately 70 kDa can penetrate the sclera, whereas only 1 kDa molecules can penetrate the cornea.
Disclosure: Mieler is a consultant for Genentech.