Dennis S Rice

Pharmacology of novel intraocular pressure-lowering targets that enhance conventional outflow facility: Pitfalls, promises and what lies ahead?

Intraocular pressure (IOP) lowering drugs that are approved for the treatment of glaucoma and ocular hypertension have limited activity on increasing aqueous humor movement through the trabecular meshwork and Schlemms canal (TM/SC). The TM/SC complex is considered the conventional outflow pathway and is a primary site of increased resistance to aqueous humor outflow in glaucoma. Novel mechanisms that enhance conventional outflow have shown promise in IOP reduction via modulation of several pathways including Rho kinase, nitric oxide/soluble guanylate cyclase/cGMP, adenosine A1, prostaglandin EP4/cAMP, and potassium channels. The clinical translatability of these pharmacological modulators based on pre-clinical efficacy models is currently being explored. In addition, identification of pathways from GWAS and other studies involving transgenic rodent models with elevated/reduced IOP phenotypes have begun to yield additional insights into IOP regulation and serve as a source for the next generation of IOP lowering targets. Lastly, improvements in drug delivery technologies to enable sustained IOP reduction are also discussed.

A Novel Selective Soluble Guanylate Cyclase Activator, MGV354, Lowers Intraocular Pressure in Preclinical Models, Following Topical Ocular Dosing

Purpose The nitric oxide/soluble guanylate cyclase/protein kinase G (NO/sGC/PKG) is known to be involved in the regulation of intraocular pressure (IOP) and may be dysregulated in glaucoma. The purpose is to demonstrate that the sGC activator MGV354 lowers IOP in a monkey model of glaucoma and could be considered as a possible new clinical drug candidate. Methods Changes to cGMP were assessed in primary human trabecular meshwork (hNTM) cells and binding studies were conducted using human sGC full-length protein. Ocular safety tolerability, exposure, and efficacy studies were conducted in rabbit and monkey models following topical ocular dosing of MGV354. Results sGC was highly expressed in the human and cynomolgus monkey outflow pathways. MGV354 had a 7-fold greater Bmax to oxidized sGC compared to that of reduced sGC and generated an 8- to 10-fold greater cGMP compared to that of a reduced condition in hTM cells. A single topical ocular dose with MGV354 caused a significant dose-dependent reduction of 20% to 40% (versus vehicle), lasting up to 6 hours in pigmented rabbits and 24 hours postdose in a cynomolgus monkey model of glaucoma. The MGV354-induced IOP lowering was sustained up to 7 days following once-daily dosing in a monkey model of glaucoma and was greater in magnitude compared to Travatan (travoprost)-induced IOP reduction. Mild to moderate ocular hyperemia was the main adverse effect noted. Conclusions MGV354 represents a novel class of sGC activators that can lower IOP in preclinical models of glaucoma. The potential for sGC activators to be used as effective IOP-lowering drugs in glaucoma patients could be further determined in clinical studies.

Highly efficient scarless knock-in of reporter genes into human and mouse pluripotent stem cells via transient antibiotic selection

Pluripotent stem cells (PSCs) edited with genetic reporters are useful tools for differentiation analysis and for isolation of specific cell populations for study. Reporter integration into the genome is now commonly achieved by targeted DNA nuclease-enhanced homology directed repair (HDR). However, human PSCs are known to have a low frequency of gene knock-in (KI) by HDR, making reporter line generation an arduous process. Here, we report a methodology for scarless KI of large fluorescent reporter genes into PSCs by transient selection with puromycin or zeocin. With this method, we can perform targeted KI of a single reporter gene with up to 65% efficiency, as well as simultaneous KI of two reporter genes into different loci with up to 11% efficiency. Additionally, we demonstrate that this method also works in mouse PSCs.

ADIPOR1 is essential for vision and its RPE expression is lost in the Mfrp rd6 mouse

The knockout (KO) of the adiponectin receptor 1 (AdipoR1) gene causes retinal degeneration. Here we report that ADIPOR1 protein is primarily found in the eye and brain with little expression in other tissues. Further analysis of AdipoR1 KO mice revealed that these animals exhibit early visual system abnormalities and are depleted of RHODOPSIN prior to pronounced photoreceptor death. A KO of AdipoR1 post-development either in photoreceptors or the retinal pigment epithelium (RPE) resulted in decreased expression of retinal proteins, establishing a role for ADIPOR1 in supporting vision in adulthood. Subsequent analysis of the Mfrprd6 mouse retina demonstrated that these mice are lacking ADIPOR1 in their RPE layer alone, suggesting that loss of ADIPOR1 drives retinal degeneration in this model. Moreover, we found elevated levels of IRBP in both the AdipoR1 KO and the Mfrprd6 models. The spatial distribution of IRBP was also abnormal. This dysregulation of IRBP hypothesizes a role for ADIPOR1 in retinoid metabolism.