Glaucoma is a major cause of blindness, affecting over 70 million people worldwide. It is a neurodegenerative optic neuropathy in which vision loss results from the loss of retinal ganglion cells (RGC). Current therapies are all directed at lowering intraocular pressure (IOP), however, despite IOP lowering, RGC loss still continues in many patients. To improve the visual outcome of patients with glaucoma new treatment strategies are warranted. The identification of an agent that promotes RGC survival to complement IOP lowering would represent a significant treatment advance. Through the screening of over 10,000 compounds, and subsequent generation of structural analogs through medicinal chemistry, we have identified compounds that are highly neuroprotective of cultured primary RGCs. This surprising discovery represents the first description of neuroprotective activity for these agents, one of which is FDA-approved for an unrelated indication. GrayBug has developed a proprietary microparticle ocular drug delivery system that, following intravitreal administration, allows slow release and sustained localized delivery to the eye, without causing inflammation. In this application, we are combining one of the novel neuroprotective drugs with our microparticle delivery system to develop a new therapeutic for the treatment of glaucoma.
In Aim 1, we will generate and characterize microparticles that release the neuroprotective drug continuously over a sustained period. Microparticles that encapsulate the neuroprotective agent(s) will be produced using the proprietary GrayBug technology exclusively licensed from Johns Hopkins. Similar microparticles produced using this technology were noninflammatory when delivered intracamerally to rabbits, an extremely sensitive evaluation model. The drug- releasing particles will be characterized fully and the duration of drug release in vitro will be evaluated. Finally, the biological activity of the drug released from the particles will be verifie in the primary murine RGC survival assay.
In Aim 2, we will test whether the drug-releasing microparticles promote RGC survival and function in the laser-induced rat IOP glaucoma model. A drug dose escalation study will be performed and visual evoked potential (VEP), a clinical assay, will be used to verify and quantitate function of the optic nerve in transmitting visual stimulation from the eye to the brain.
In Aim 3, we will evaluate the duration of drug release over a period of three months and perform preliminary safety analyses following intravitreal administration of microparticles to normal rats. Safety evaluations include fundus exams, IOP, ERG, and retinal morphology analyses, as a preliminary evaluation of the long-term effects of drug exposure to the eye. The demonstration of efficacy in the rodent glaucoma model, including the verification of function of the protected RGCs with long- term drug release and no overt toxicity in the eye, would provide evidence of the therapeutic potential of our neuroprotective drug delivery strategy for the treatment of glaucoma. Successful completion of these specific aims will lead us to Phase II and ultimately to human clinical evaluation.
Glaucoma is a leading cause of blindness, affecting over 70 million people worldwide. Glaucoma is caused by the loss of retinal ganglion cells (RGC). Current therapies are focused on reducing intraocular pressure (IOP), but RGC loss continues in some patients. We identified drugs that prevent RGC loss even when IOP is elevated, and developed a proprietary, sustained-release, ocular drug delivery system. GrayBug seeks to evaluate this delivery system with the novel neuroprotective drug. The GrayBug drug is expected to be synergistic with current IOP-lowering glaucoma therapies, resulting in an improved treatment for glaucoma.
| Sluch, Valentin M; Zack, Donald J (2014) Stem cells, retinal ganglion cells and glaucoma. Dev Ophthalmol 53:111-21 |
