Eyeworld

NOV 2012

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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46 EW SECONDARY FEATURE February 2011 Glaucoma devices November 2012 Combating patient noncompliance by Enette Ngoei EyeWorld Contributing Writer Exploring drug delivery devices for glaucoma medication D espite the availability of safe and effective glaucoma drugs on the market, clinical efficacy has been affected by non- compliance in patients. Objective data from electronic monitoring and video records have shown that patients have trouble putting in their eye drops as prescribed. To increase patient adherence, companies have developed gel for- mulations such as timolol (Timop- tic-XE, Merck, Whitehouse, N.J.) that reduce the number of doses needed each day. Practitioners also provide patient education to create a sense of need and try to encourage daily habits such as putting the drops in after brushing teeth in the morning, said Robert Williams, M.D., Louisville, Ky. Electronic methods such as text message reminders have also been explored, Dr. Williams said, but these carry costs in both time and money that most practices can't afford. Even if they remember, some patients can't even get the drops in, he added. Another potential solution is a drug delivery system. According to Gary Novack, president of Pharma- Logic Development Inc., San Rafael, Calif., "There are a number of drug delivery systems being evaluated in various levels of development to provide a longer lasting delivery than what is achieved with patients using daily eye drops. Each of these systems has its own advantages and disadvantages." Potential drug delivery systems Among the various types of delivery systems being explored are ocular inserts, biodegradable micro- and nanoparticles that are injected, as well as devices that require surgical implantation, according to a 2011 review, "Novel drug delivery systems for glaucoma," by Erin Lavik, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, and colleagues, published in Eye. An example is a punctal plug system developed by Ocular Therapeutix (Bedford, Mass.), Dr. Williams said. The company reported some animal results in 2011 and preliminary human results on a punctal plug system. According to a May press release from Ocular Therapeutix, its "travo- prost-loaded punctum plugs use the company's proprietary polyethylene glycol hydrogel technology to re- lease drug in a sustained fashion. At the end of the treatment period, the plug begins to degrade and exits the nasolacrimal system without need for removal by the physician. Each plug contains a visualization agent for retention monitoring through- out the treatment period." While contact lenses that release medications were being explored by some companies, Dr. Williams said they have been pretty much aban- doned because "they just don't pro- vide a prolonged enough delivery to make it viable for glaucoma, but there have been fornix-based devices like the Ocusert, and people have continued to look at fornix-based devices." Amorphex Therapeutics (Andover, Mass.) is developing an ocular insert to be placed on the sclera that will deliver a glaucoma drug for extended periods. There also are subconjunctival reservoirs that are being looked at such as one made of a collagen ma- terial that could be impregnated with latanoprost; it is still in the very early animal testing phase, Dr. Williams said. pSivida (Watertown, Mass.) in collaboration with Pfizer (New York) has developed Durasert, which is a fully bioerodible, long-term, sustained-release implant delivering latanoprost, designed to go into the subconjunctiva. A more active sort of reservoir, the Ophthalmic MicroPump (Replenish Inc., Pasadena, Calif.) can be repeatedly refilled and has a pump in it that pumps out the drug in measured aliquots over prolonged periods of time, he said. In addition, Dr. Williams said, Allergan (Irvine, Calif.) has reported preliminary results of a sustained- release Lumigan (bimatoprost) product in humans that's placed inside the eye itself like in the anterior chamber. According to Dr. Novack, "Most drug delivery systems require exten- sive time and resources to develop. While we are hopeful that these will reach patients soon, unfortunately few are in an advanced development stage." Challenges Regulatory hurdles aside, there are important scientific challenges to developing an effective glaucoma drug delivery device. One consideration is how much drug can be put in a confined space that would be enough to treat a pa- tient for 9 months, Dr. Novack said. Finding a place where you can put enough drug that it will last for the whole period of time is another challenge, Dr. Williams said. With punctal plugs, only a very small vol- ume of space is available, so only drugs that are active in very low concentrations like the prostaglandins can be used.

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