Bi-functional small molecule for glaucomatous optic neuropathy

Abstract

Purpose : The multifaceted pathology associated with glaucoma is difficult to treat by monotherapy such as lowering intraocular pressure (IOP). Oxidative stress is involved in IOP elevation and retinal ganglion cell (RGC) death possibly via decreased activity of antioxidant enzymes. Our hypothesis is that, a small hybrid molecule SA-2 and its PLGA encapsulated nanoparticle (NP) drug delivery vehicle (SA-2-NPs) possessing a nitric oxide (NO) donating group and a redox antioxidant moiety will lower IOP as well as possess neuro/cytoprotective potential.

Methods : IOP-independent neuroprotection of RGCs: Mice (C57BL6, 12 weeks, n=5) were anesthetized and the optic nerve crush (ONC) was performed on one eye followed by intravitreal injection of 2ml of 1% SA-2 formulated in PBS or vehicle to the crushed eye at day 0 and 3. At day 7, pattern electroretinogram (PERG) was performed, following which retinas were flat mounted. Number of surviving, RBPMS positive RGCs were counted. IOP lowering effect: Nine Brown Norway normotensive rats (n=3 per each group) were used to evaluate the IOP-lowering properties of SA-2-NPs under a masked protocol. Topical eye drops (30 µL/drop) containing : A) Vehicle (PBS), B) Travoprost (0.004%)-positive control or C) SA-2-NPs (100 µg/mL) formulated in PBS were administered in three rats and IOP was measured using the TonoLab rebound tonometer at various time points: 0, 3, 6, 24 and 48 h post-dosing. The entire dosing schedule was repeated 3 times in each rat.

Results : Compound SA-2 treatment was significantly (p<0.001, t-test) protecting against RGCs loss following ONC. Number of RGCs for ONC and PBS treated mice was 1000 cells/cm² vs ONC and SA-2 treated group (2100 cells/cm²) and was comparable to the naïve control (2650 cells/cm²), (n = 3 or 4 animals per group). PLGA encapsulated SA-2-NPs (100mg) statistically (t-test, p<0.001) lowered the IOP in treated eyes by 19% and 21% at 24 and 48h respectively in comparison to contralateral control eyes. Travoprost was statistically effective in lowering IOP in treated rat eye by 14% at 6h.

Conclusions : Taken together, our results are consistent with our hypothesis that this novel class of hybrid compound and its PLGA encapsulated nanoparticle will decrease IOP and protect RGCs from cell death. Further structure optimization of the lead compound, dose optimization, IOP lowering study in ocular hypertensive rodent models are underway.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.