Drug delivery to the posterior segments of the eye.

of blindness among the elderly. In the US, more than eight million people suffer from this disease; this number is projected to increase many-fold by 2020.1 AMD can be of the dry and wet form and is a consequence of excessive aging associated with alterations in the retinal pigment epithelium (RPE). In wet AMD, CNV occurs with fluid build-up in the sub-retinal space. The dry form of AMD is associated with drusen formation and RPE atrophy.2 Diabetic Retinopathy often leads to neovascularisation and macular edema and is the third leading cause of blindness in the US. Macular edema is the swelling of the macula and occurs in approximately 10% of all diabetics.3 Endophthalmitis is another cause of blindness. It is characterised by infection of the interior ocular space by microorganisms, due to post-operative infections. These include gram positive bacteria such as Staphylococcus aureus and streptococci.4,5 The clinical and experimental drugs for the posterior segment treatments include both small and large molecules (such as siRNA, antibodies, growth factors, DNA), but delivering these molecules to the target sites is problematic. When administered topically, drug concentrations in the retina and choroid are many-fold lower than the tear fluid. Drug delivery to the posterior segment of the eye is most efficiently achieved by local, ocular routes of administration, which includes intravitreal, subretinal, suprachoroidal and periocular injections.6,7 Intravitreal injections and implants deliver drugs effectively to the retina and the choroid. For example, intravitreal injections of therapeutics are routinely used in the treatment of wet AMD (LucentisTM, Macugen, VitraveneTM), macular inflammation (TriesenceTM), etc.8 This mode of administration while efficacious is highly invasive; considerable risks exist to developing infections (endophthalmitis) and retinal detachment with repeated injections over a person’s lifetime. However, high concentrations of drug can be achieved with intravitreal injections with sustained presence due to the relative lack of fluid flow in the vitreous humour. Triamcinolone acetonide is the most commonly used steroid treatment for AMD and vitreoretinal disorders. To achieve a dose for prolonged duration and to minimise repeated injections, triamcinolone acetonide suspension must be injected at high concentrations. Due to the presence of high In this article, Shikha Barman, PhD, Chief Executive Officer & Chief Technology Officer, Integral BioSystems, reviews approaches for delivering drugs for diseases of the back of the eye, and introduces EySite-InjecTTM, a biodegradable, precisely tunable sustained-release delivery system which can be administered to suprachoroidal, intravitreal, subconjunctival sites by injections through a 31G needle. SUSTAINED DRUG DELIVERY TO THE POSTERIOR SEGMENTS OF THE EYE