Effects of Rho Kinase Inhibitors on Intraocular Pressure and Aqueous Humor Dynamics in Nonhuman Primates and Rabbits

NCX 470 Reduces Intraocular Pressure More Effectively Than Lumigan in Dogs and Enhances Conventional and Uveoscleral Outflow in Non-Human Primates and Human Trabecular Meshwork/Schlemm's Canal Constructs

Purpose: To determine NCX 470 (0.1%) and Lumigan® (bimatoprost ophthalmic solution, 0.01%-LUM) intraocular pressure (IOP)-lowering activity after single or repeated (5 days) dosing along with changes in aqueous humor (AH) dynamics. Methods: Ocular hypotensive activity of NCX 470 and LUM was compared with vehicle (VEH) in Beagle dogs using TonoVet®. Non-human primates (NHP) and bioengineered three-dimensional (3D) human Trabecular Meshwork/Schlemm's Canal (HTM/HSC™) constructs exposed to transforming growth factor-β2 (TGFβ2) were used to monitor NCX 470 and LUM-induced changes in AH dynamics. Results: NCX 470 (30 μL/eye) showed greater IOP reduction compared with LUM (30 μL/eye) following single AM dosing [maximum change from baseline (CFBmax) = -1.39 ± 0.52, -6.33 ± 0.73, and -3.89 ± 0.66 mmHg (mean ± standard error of the mean) for VEH, NCX 470, and LUM, respectively]. Likewise, repeated 5 days daily dosing of NCX 470 resulted in lower IOP than LUM across the duration of the study (average IOP decrease across tests was -0.45 ± 0.22, -6.06 ± 0.15, and -3.60 ± 0.22 mmHg for VEH, NCX 470, and LUM, respectively). NCX 470 increased outflow facility (Cfl) in vivo in NHP (CflVEH = 0.37 ± 0.09 μL/min/mmHg and CflNCX470 = 0.64 ± 0.17 μL/min/mmHg) as well as in vitro (CHTM/HSC) in HTM/HSC constructs (CHTM/HSC_VEH = 0.47 ± 0.02 μL/min/mm2/mmHg and CHTM/HSC_NCX470 = 0.76 ± 0.03 μL/min/mm2/mmHg). In addition, NCX 470 increased uveoscleral outflow (FuVEH = 0.62 ± 0.26 μL/min and FuNCX470 = 1.53 ± 0.39 μL/min with episcleral venous pressure of 15 mmHg) leaving unaltered aqueous flow (AHFVEH = 2.03 ± 0.22 μL/min and AHFNCX470 = 1.93 ± 0.31 μL/min) in NHP. Conclusions: NCX 470 elicits greater IOP reduction than LUM following single or repeated dosing. Data in NHP and 3D-HTM/HSC constructs suggest that changes in Cfl and Fu account for the robust IOP-lowering effect of NCX 470.

Effect of genotype on individual response to the pharmacological treatment of glaucoma: a systematic review and meta-analysis

The social impact of glaucoma is worth of note: primary open-angle glaucoma (POAG) is one of the leading causes of irreversible blindness worldwide, affecting some 68.56 million people with overall prevalence of 2.4%. Since one of the main risk factors for the development of POAG is the increase of intraocular pressure (IOP) causing retinal ganglion cells death, the medical treatment of POAG consists in the use of drugs endowed with neuroprotective effect and able to reduce IOP. These drugs include beta-blockers, prostaglandin analogues, carbonic anhydrase inhibitors, alpha or cholinergic agonists and rho kinase inhibitors. However, not all the patients respond to the same extent to the therapy in terms of efficacy and safety. Genetics and genome wide association studies have highlighted the occurrence of mutations and polymorphisms influencing the predisposition to develop POAG and its phenotype, as well as affecting the response to pharmacological treatment. The present systematic review and meta-analysis aims at identifying genetic variants and at verifying whether these can influence the responsiveness of patients to therapy for efficacy and safety. It follows the most updated Preferred Reporting Items for Systematic reviews and Meta-Analyses 2020 recommendations. The literature search was conducted consulting the most relevant scientific databases, i.e. PubMed/MEDLINE, Scopus, Web of Science and Public Health Genomics and Precision Health Knowledge Base up to June 14th, 2023. The search retrieved 1026 total records, among which eight met the eligibility criteria for inclusion in the analysis. The results demonstrated that the most investigated pharmacogenetic associations concern latanoprost and timolol, and that efficacy was studied more in depth than safety. Moreover, the heterogeneity of design and paucity of studies prompt further investigation in randomized clinical trials. In fact, adequately powered and designed pharmacogenetic association studies are needed to provide body of evidence with good certainty for a more appropriate use of medical therapy in POAG.PROSPERO registration: CRD42023434867.

Comparison of intraocular pressure in New Zealand White rabbits measured using rebound and applanation tonometers and four different methods of physical restraint

AIMS

To compare intraocular pressure (IOP) measurements obtained in rabbits using rebound (TV) and applanation (TPV) tonometers with four different methods of physical restraint.

METHODS

A total of 20 New Zealand White rabbits (40 eyes) were included in this study. IOP readings were obtained from both eyes using the two different tonometers. The rabbits were placed on a table and restrained by wrapping in a cloth (Method I), by scruffing with rear support (Method II), by wrapping in a cloth and cupped in the hands (Method III), or by a box restrainer (Method IV).

RESULTS

The mean IOP measurement obtained by TPV was higher than that obtained with the TV for all handling methods. Mean differences (TV-TPV, in mmHg) in IOP were -5.3 (95% Cl = -6.5 to -4.1) for Method 1, -4.7 (95% Cl = -6.2 to -3.29) for Method II, -4.9 (95% Cl = -6.2 to -3.7) for Method III and -7.6 (95% Cl = -9.2 to -5.9) for Method IV. Using the TV tonometer, mean IOP for Method IV was higher than for Method I (mean difference 2.1 (95% Cl = 1.1-3.1)), whereas using the TPV tonometer, mean IOP for Method IV was significantly higher than Method I, II, and III (mean differences: 4.4 (95% Cl = 2.6-5.9), 3.7 (95% Cl = 2-5.3) and 3.8 (95% Cl = 2-5.4), respectively). According to Bland-Altman plots, IOP readings for TPV tended to be higher than those for TV with all handling methods, but with a lack of agreement. The mean difference and 95% limits of agreement for the differences between TV and TPV were -5.4 mmHg (-12.5-1.9 mmHg), -4.7 mmHg (-12.9-3.5 mmHg), -4.9 mmHg (-12-2.2 mmHg), and -7.5 mmHg (-17.4-2.3 mmHg), with Methods I, II, III, and IV, respectively. Comparing TV and TPV, only 7.5%, 12.5%, 27.5%, and 15% of IOP measurements from 20 rabbits were within the range considered clinically acceptable for IOP (± 2 mmHg) for Method I, II, III, and IV, respectively.

CONCLUSION AND CLINICAL RELEVANCE

In conclusion, the physical restraint method should be recorded when IOP is measured in rabbits, and TV and TPV tonometers cannot be used interchangeably (high bias and low proportion of measurements within ± 2 mmHg).

Additive Intraocular Pressure-Lowering Effects of a Novel Selective EP2 Receptor Agonist, Omidenepag Isopropyl, Combined with Existing Antiglaucoma Agents in Conscious Ocular Normotensive Monkeys

Purpose: To investigate the intraocular pressure (IOP)-lowering effects of omidenepag isopropyl (OMDI), a potent and highly selective prostanoid EP2 receptor agonist, as a potential first-line ocular hypotensive agent when combined with existing antiglaucoma agents in conscious ocular normotensive monkeys. Methods: Male cynomolgus monkeys were examined under conscious conditions. OMDI ophthalmic solution alone was topically applied to an eye or combined with other ophthalmic solutions at 5-min intervals. The contralateral eye was left untreated. IOP was measured before and at 2, 4, 6, and 8 h after instillation. Results: Topical application of OMDI to the eye resulted in statistically significant IOP reduction, which lasted for at least 6 h. The IOP-lowering effects of OMDI concomitantly administered with any of the tested antiglaucoma agents (timolol, brinzolamide, netarsudil, ripasudil, and brimonidine) were greater than those of OMDI alone. Furthermore, these enhanced IOP responses to their concomitant use were statistically significant compared with those of the tested antiglaucoma agents alone. Any combination of OMDI with the tested agents did not lead to serious abnormalities either systemically or locally in the eye. Conclusions: We demonstrated that OMDI has additive IOP-lowering effects when administered in combination with various antiglaucoma agents, namely, β-adrenergic antagonist, carbonic anhydrase inhibitor, Rho-associated coiled-coil containing protein kinase inhibitors, and α2-adrenergic agonist. These results suggest that OMDI provides additional clinical benefits because of its unique mechanisms of action when combination therapy is required.

C3 Transferase-Expressing scAAV2 Transduces Ocular Anterior Segment Tissues and Lowers Intraocular Pressure in Mouse and Monkey

Glaucoma is a lifelong disease with elevated intraocular pressure (IOP) as the main risk factor, and reduction of IOP remains the major treatment for this disease. However, current IOP-lowering therapies are far from being satisfactory. We have demonstrated that the lentivirus-mediated exoenzyme C3 transferase (C3) expression in rat and monkey eyes induced relatively long-term IOP reduction. We now show that intracameral injection of self-complementary AAV2 containing a C3 gene into mouse and monkey eyes resulted in morphological changes in trabecular meshwork and IOP reduction. The vector-transduced corneal endothelium and the C3 transgene expression, not vector itself, induced corneal edema as a result of actin-associated endothelial barrier disruption. There was a positive (quadratic) correlation between measured IOP and grade of corneal edema. This is the first report of using an AAV to transduce the trabecular meshwork of monkeys with a gene capable of altering cellular structure and physiology, indicating a potential gene therapy for glaucoma.

Lentiviral Vector-Mediated Expression of Exoenzyme C3 Transferase Lowers Intraocular Pressure in Monkeys

Primary open-angle glaucoma (POAG) is considered a lifelong disease characterized by optic nerve deterioration and visual field damage. Although the disease progression can usually be controlled by lowering the intraocular pressure (IOP), therapeutic effects of current approaches do not last long. Gene therapy could be a promising method for persistent treatment of the disease. Our previous study demonstrated that gene transfer of exoenzyme C3 transferase (C3) to the trabecular meshwork (TM) to inhibit Rho GTPase (Rho), the upstream signal molecule of Rho-associated kinase (ROCK), resulted in lowered IOP in normal rodent eyes. In the present study, we show that the lentiviral vector (LV)-mediated C3 expression inactivates RhoA in human TM cells by ADP ribosylation, resulting in disruption of the actin cytoskeleton and altered cell morphology. In addition, intracameral delivery of the C3 vector to monkey eyes leads to persistently lowered IOP without obvious signs of inflammation. This is the first report of using a vector to transduce the TM of an alive non-human primate with a gene that alters cellular machinery and physiology. Our results in non-human primates support that LV-mediated C3 expression in the TM may have therapeutic potential for glaucoma, the leading cause of irreversible blindness in humans.

Effects of Lentivirus-Mediated C3 Expression on Trabecular Meshwork Cells and Intraocular Pressure

Purpose

We evaluated the effects of lentivirus-mediated exoenzyme C3 transferase (C3) expression on cultured primary human trabecular meshwork (HTM) cells in vitro, and on rat intraocular pressure (IOP).

Methods

HTM cells were cultured and treated with lentivirus vectors expressing either green fluorescent protein (GFP) only (LV-GFP) or GFP and C3 together (LV-C3-GFP). Changes in cell morphology and actin stress fibers were assessed. The vectors were also injected into the anterior chamber of rats, and GFP expression was visualized by a Micron III Retinal Imaging Microscope in vivo and a fluorescence microscope ex vivo. Changes in rat IOP were monitored by using a rebound tonometer and the eyes were evaluated by slit lamp.

Results

LV-mediated C3 expression induced morphologic changes in HTM cells. The cells became retracted and rounded. GFP expression in the anterior chamber angle of rats was observed in vivo from 8 days to 48 days after injection of LV-C3-GFP or LV-GFP. IOP was significantly decreased in the LV-C3-GFP group starting 3 days post injection, and lasting for at least 40 days, when compared to either the contralateral control eyes (the LV-GFP group) or the ipsilateral baseline before injection (P < 0.05). No obvious inflammatory signs were observed in either the LV-C3-GFP or LV-GFP groups.

Conclusions

LV-mediated C3 expression induced changes in morphology of cultured HTM cells. Intracameral injection of LV-C3-GFP lowered rat IOP for at least 40 days. No significant inflammatory reactions were observed in either the LV-C3-GFP or LV-GFP groups. This study supports the possible use of C3 gene therapy for the treatment of glaucoma.

Topical Rho-Associated Kinase Inhibitor, Y27632, Accelerates Corneal Endothelial Regeneration in a Canine Cryoinjury Model

PURPOSE

Corneal endothelial cell regeneration varies by species, with nonhuman primates (NHPs) and rabbits displaying low and high proliferative capacities, respectively. Recent studies report that topical application of rho-associated kinase (ROCK) inhibitors accelerates corneal endothelial wound healing in animal models and human patients with endothelial dysfunction. This study determines the regenerative capacity of canine corneal endothelial cells in vivo and their response to a topical ROCK inhibitor, Y27632, after transcorneal freezing.

METHODS

Right eyes of 6 beagles underwent transcorneal freezing; 10 mM ROCK inhibitor Y27632 or vehicle control was applied topically to both eyes at least 4 times daily for 56 days. Endothelial cell density was evaluated by in vivo confocal microscopy, and corneal thickness was measured by Fourier-domain optical coherence tomography (FD-OCT) and ultrasound pachymetry.

RESULTS

Transcorneal freezing induced severe central corneal edema in dogs, with restoration of transparency occurring within 4 weeks. Y27632 significantly decreased corneal thickness by FD-OCT and ultrasound pachymetry in the acute phase and significantly increased endothelial cell density at days 28 and 42 post-cryoinjury, suggesting faster restoration of endothelial cell recovery.

CONCLUSIONS

Canine corneal endothelial function recovers at a similar rate as NHPs but more slowly than rabbits after cryoinjury. Faster corneal endothelial wound healing was observed by in vivo confocal microscopy and FD-OCT in dogs treated with Y27632 versus vehicle controls. Thus, a canine cryoinjury model may be a useful alternative to NHPs in detecting a response to therapies directed at endothelial regeneration.

A Randomized, Controlled Phase I/II Study to Evaluate the Safety and Efficacy of MGV354 for Ocular Hypertension or Glaucoma

PURPOSE

To assess the clinical safety, tolerability, and efficacy of topically administered MGV354, a soluble guanylate cyclase (sGC) activator, in patients with ocular hypertension (OH) or glaucoma.

DESIGN

Double-masked, randomized, and vehicle-controlled study.

METHODS

Parts 1 and 2 evaluated safety and tolerability to identify the maximum tolerated dose (MTD) of once-daily MGV354 in 32 healthy volunteers (Part 1) and 16 patients with OH or glaucoma (Part 2) at a single clinical site. Part 3 was a multisite trial that evaluated intraocular pressure (IOP)-lowering efficacy of the MTD administered nightly for 1 week in 50 patients with minimum IOP of 24 mm Hg at 8 AM, with a main outcome measure of mean diurnal IOP at day 8 compared to baseline (ClinicalTrials.govNCT02743780).

RESULTS

There was no difference in favor of MGV354 for IOP lowering; change from baseline to day 8 in mean diurnal IOP was -0.6 mm Hg for MGV354-treated patients and -1.1 mm Hg for vehicle-treated patients in Part 3, with a confidence interval of -0.7 to 1.7. The most common adverse events reported after MGV354 administration were conjunctival and ocular hyperemia.

CONCLUSIONS

Overall, MGV354 0.1% demonstrated no statistically significant effect compared to vehicle in lowering IOP based on the study's main outcome measure. MGV354 produced ocular hyperemia consistent with its pharmacology.

Effects of a Novel Selective EP2 Receptor Agonist, Omidenepag Isopropyl, on Aqueous Humor Dynamics in Laser-Induced Ocular Hypertensive Monkeys

PURPOSE

To investigate the mechanism of the intraocular pressure (IOP)-lowering effect of a novel selective prostaglandin E2 receptor 2 (EP2) receptor agonist, omidenepag isopropyl (OMDI).

METHODS

The effect of OMDI on IOP and aqueous humor dynamics was evaluated in cynomolgus monkeys with unilateral laser-induced ocular hypertension. In a crossover manner, the hypertensive eye of each monkey was dosed once daily with 20 μL of either 0.002% OMDI or vehicle. On day 7 of dosing, IOP was measured by pneumatonometry, aqueous humor flow and outflow facility were evaluated by fluorophotometry, and uveoscleral outflow was calculated mathematically. Treatments were compared by paired t-tests.

RESULTS

OMDI at 0.002% significantly lowered IOP by 27%, 35%, and 44% at 0.5, 1.5, and 4 h after the last dosing, respectively. There was no difference in aqueous humor flow between vehicle and OMDI treatments. When comparing OMDI to the vehicle treatment, outflow facility and uveoscleral outflow were significantly (P < 0.05) increased by 71% and 176%, respectively.

CONCLUSIONS

OMDI, a novel IOP-lowering compound, reduced IOP by increasing outflow facility and uveoscleral outflow in nonhuman primates.

The Discovery of ( S)-1-(6-(3-((4-(1-(Cyclopropanecarbonyl)piperidin-4-yl)-2-methylphenyl)amino)-2,3-dihydro-1 H-inden-4-yl)pyridin-2-yl)-5-methyl-1 H-pyrazole-4-carboxylic Acid, a Soluble Guanylate Cyclase Activator Specifically Designed for Topical Ocular Delivery as a Therapy for Glaucoma

Soluble guanylate cyclase (sGC), the endogenous receptor for nitric oxide (NO), has been implicated in several diseases associated with oxidative stress. In a pathological oxidative environment, the heme group of sGC can be oxidized becoming unresponsive to NO leading to a loss in the ability to catalyze the production of cGMP. Recently a dysfunctional sGC/NO/cGMP pathway has been implicated in contributing to elevated intraocular pressure associated with glaucoma. Herein we describe the discovery of molecules specifically designed for topical ocular administration, which can activate oxidized sGC restoring the ability to catalyze the production of cGMP. These efforts culminated in the identification of compound (+)-23, which robustly lowers intraocular pressure in a cynomolgus model of elevated intraocular pressure over 24 h after a single topical ocular drop and has been selected for clinical evaluation.

The Effects of Netarsudil Ophthalmic Solution on Aqueous Humor Dynamics in a Randomized Study in Humans

PURPOSE

Netarsudil, an inhibitor of Rho kinase and a norepinephrine transporter, has been shown to lower elevated intraocular pressure (IOP) in controlled studies of patients with open-angle glaucoma and ocular hypertension, and in healthy volunteers. The mechanism of this ocular hypotensive effect in humans is unknown.

METHODS

The objective of this study was to evaluate the effect of netarsudil 0.02% on aqueous humor dynamics (AHD) parameters. In this double-masked, vehicle-controlled, paired-eye comparison study, 11 healthy volunteers received topical netarsudil ophthalmic solution 0.02% or its vehicle once daily for 7 days (morning dosing). The primary endpoints were the change in AHD parameters, compared between active and vehicle-treated eyes.

RESULTS

In netarsudil-treated eyes, diurnal outflow facility increased from 0.27 ± 0.10 μL/min/mmHg to 0.33 ± 0.11 μL/min/mmHg (+22%; P = 0.02) after 7 days of treatment. In placebo-treated eyes, diurnal outflow facility did not significantly change (P = 0.94). The difference between netarsudil and placebo eyes in diurnal change of outflow facility was 0.08 μL/min/mmHg (P < 0.001). Diurnal episcleral venous pressure (EVP) in netarsudil-treated eyes decreased from 7.9 ± 1.2 mmHg to 7.2 ± 1.8 (-10%; P = 0.01). Diurnal EVP was not significantly different between netarsudil- and placebo-treated eyes. There was a trend toward decreasing aqueous humor flow rate (-15%; P = 0.08). No treatment changes were seen in uveoscleral outflow rate.

CONCLUSIONS

Once-daily dosing of netarsudil ophthalmic solution 0.02% lowered IOP through increasing trabecular outflow facility and reducing EVP. This suggests a combination of mechanisms that affect both the proximal and distal outflow pathways.

iDrugs and iDevices Discovery Research: Preclinical Assays, Techniques, and Animal Model Studies for Ocular Hypotensives and Neuroprotectants

Discovery ophthalmic research is centered around delineating the molecular and cellular basis of ocular diseases and finding and exploiting molecular and genetic pathways associated with them. From such studies it is possible to determine suitable intervention points to address the disease process and hopefully to discover therapeutics to treat them. An investigational new drug (IND) filing for a new small-molecule drug, peptide, antibody, genetic treatment, or a device with global health authorities requires a number of preclinical studies to provide necessary safety and efficacy data. Specific regulatory elements needed for such IND-enabling studies are beyond the scope of this article. However, to enhance the overall data packages for such entities and permit high-quality foundation-building publications for medical affairs, additional research and development studies are always desirable. This review aims to provide examples of some target localization/verification, ocular drug discovery processes, and mechanistic and portfolio-enhancing exploratory investigations for candidate drugs and devices for the treatment of ocular hypertension and glaucomatous optic neuropathy (neurodegeneration of retinal ganglion cells and their axons). Examples of compound screening assays, use of various technologies and techniques, deployment of animal models, and data obtained from such studies are also presented.

Effect of Cromakalim Prodrug 1 (CKLP1) on Aqueous Humor Dynamics and Feasibility of Combination Therapy With Existing Ocular Hypotensive Agents

Purpose

Cromakalim prodrug 1 (CKLP1) is a water-soluble ATP-sensitive potassium channel opener that has shown ocular hypotensive properties in ex vivo and in vivo experimental models. To determine its mechanism of action, we assessed the effect of CKLP1 on aqueous humor dynamics and in combination therapy with existing ocular hypotensive agents.

Methods

Outflow facility was assessed in C57BL/6 mice by ex vivo eye perfusions and by in vivo constant flow infusion following CKLP1 treatment. Human anterior segments with no trabecular meshwork were evaluated for effect on pressure following CKLP1 treatment. CKLP1 alone and in combination with latanoprost, timolol, and Rho kinase inhibitor Y27632 were evaluated for effect on intraocular pressure in C57BL/6 mice and Dutch-belted pigmented rabbits.

Results

CKLP1 lowered episcleral venous pressure (control: 8.9 ± 0.1 mm Hg versus treated: 6.2 ± 0.1 mm Hg, P < 0.0001) but had no detectable effect on outflow facility, aqueous humor flow rate, or uveoscleral outflow. Treatment with CKLP1 in human anterior segments without the trabecular meshwork resulted in a 50% ± 9% decrease in pressure, suggesting an effect on the distal portion of the conventional outflow pathway. CKLP1 worked additively with latanoprost, timolol, and Y27632 to lower IOP, presumably owing to combined effects on different aspects of aqueous humor dynamics.

Conclusions

CKLP1 lowered intraocular pressure by reducing episcleral venous pressure and lowering distal outflow resistance in the conventional outflow pathway. Owing to this unique mechanism of action, CKLP1 works in an additive manner to lower intraocular pressure with latanoprost, timolol, and Rho kinase inhibitor Y27632.

Topical treatment of glaucoma: established and emerging pharmacology

INTRODUCTION

Glaucoma is a collection of optic neuropathies consisting of retinal ganglion cell death and corresponding visual field loss. Glaucoma is the leading cause of irreversible vision loss worldwide and is forecasted to precipitously increase in prevalence in the coming decades. Current treatment options aim to lower intraocular pressure (IOP) via topical or oral therapy, laser treatment to the trabecular meshwork or ciliary body, and incisional surgery. Despite increasing use of trabecular laser therapy, topical therapy remains first-line in the treatment of most forms of glaucoma. Areas covered: Novel glaucoma therapies are a long-standing focus of investigational study. More than two decades have passed since the last United States Food and Drug Administration (FDA) approval of a topical glaucoma drug. Here, the authors review established topical glaucoma drops as well as those currently in FDA phase 2 and 3 clinical trial, nearing clinical use. Expert opinion: Current investigational glaucoma drugs lower IOP, mainly through enhanced trabecular meshwork outflow. Although few emerging therapies show evidence of retinal ganglion cell and optic nerve neuroprotection in animal models, emerging drugs are focused on lowering IOP, similar to established medicines.

Netarsudil Increases Outflow Facility in Human Eyes Through Multiple Mechanisms

Purpose

Netarsudil is a Rho kinase/norepinephrine transporter inhibitor currently in phase 3 clinical development for glaucoma treatment. We investigated the effects of its active metabolite, netarsudil-M1, on outflow facility (C), outflow hydrodynamics, and morphology of the conventional outflow pathway in enucleated human eyes.

Methods

Paired human eyes (n = 5) were perfused with either 0.3 μM netarsudil-M1 or vehicle solution at constant pressure (15 mm Hg). After 3 hours, fluorescent microspheres were added to perfusion media to trace the outflow patterns before perfusion-fixation. The percentage effective filtration length (PEFL) was calculated from the measured lengths of tracer distribution in the trabecular meshwork (TM), episcleral veins (ESVs), and along the inner wall (IW) of Schlemm's canal after global and confocal imaging. Morphologic changes along the trabecular outflow pathway were investigated by confocal, light, and electron microscopy.

Results

Perfusion with netarsudil-M1 significantly increased C when compared to baseline (51%, P < 0.01) and to paired controls (102%, P < 0.01), as well as significantly increased PEFL in both IW (P < 0.05) and ESVs (P < 0.01). In treated eyes, PEFL was significantly higher in ESVs than in the IW (P < 0.01) and was associated with increased cross-sectional area of ESVs (P < 0.01). Percentage effective filtration length in ESVs positively correlated with the percentage change in C (R² = 0.58, P = 0.01). A significant increase in juxtacanalicular connective tissue (JCT) thickness (P < 0.05) was found in treated eyes compared to controls.

Conclusions

Netarsudil acutely increased C by expansion of the JCT and dilating the ESVs, which led to redistribution of aqueous outflow through a larger area of the IW and ESVs.