A Highly Selective Rho-Kinase Inhibitor (ITRI-E-212) Potentially Treats Glaucoma Upon Topical Administration With Low Incidence of Ocular Hyperemia

Activation of the ROCK/MYLK Pathway Affects Complex Molecular and Morphological Changes of the Trabecular Meshwork Associated With Ocular Hypertension

Purpose

The Rho-associated protein kinase and myosin light chain kinase (ROCK/MYLK) pathway undeniably plays a pivotal role in the pathophysiology of primary open-angle glaucoma (POAG). In our study, we utilized both ocular hypertension (OHT) rabbit models and clinical investigations to gain invaluable insights that propel the development of novel treatments targeting proteins and genes associated with the trabecular meshwork (TM), thereby offering promising avenues for the management of POAG.

Methods

Following microbead injections into the anterior chamber of the ocular cavity of rabbits, we observed elevated histiocyte numbers and immune scores for MYLK-4/ pMLC-2, alongside a reduction in the void space within the TM. Notably, treatment was performed with 0.1% ITRI-E-(S)-4046, a compound with dual kinase inhibitor (highly specific inhibitor of ROCK1/2 and MYLK4), significantly reduced intraocular pressure (IOP; P < 0.05) and expanded the void space within the TM (P < 0.0001) compared with OHT rabbits. In clinical investigations, we utilized whole transcriptome sequencing to analyze gene expression specifically related to the TM, obtained from patients (5 early-onset and 5 late-onset) undergoing trabeculectomy.

Results

Our findings revealed 103 differential expression genes (DEGs) out of 265 molecules associated with the Rho family GTPase pathway, exhibiting a P value of 1.25E-10 and a z-score of -2.524. These results underscore significant differences between the early-onset and late-onset POAG and highlight the involvement of the ROCK/MYLK pathway.

Conclusions

These findings underscore the critical involvement of the ROCK/MYLK pathway in both OHT-related and different onsets of POAG, providing valuable insights into the TM-related molecular mechanisms underlying the disease.

The Application of Rho Kinase Inhibitors in the Management of Glaucoma

Glaucoma is a chronic neurodegenerative disease that poses a significant threat of irreversible blindness worldwide. Current treatments for glaucoma focus on reducing intraocular pressure (IOP), which is the only modifiable risk factor. Traditional anti-glaucomatous agents, including carbonic anhydrase inhibitors, beta-blockers, alpha-2 agonists, and prostaglandin analogs, work by either improving uveoscleral outflow or reducing aqueous humor production. Rho kinase (ROCK) inhibitors represent a novel class of anti-glaucomatous drugs that have emerged from bench to bedside in the past decade, offering multifunctional characteristics. Unlike conventional medications, ROCK inhibitors directly target the trabecular meshwork outflow pathway. This review aims to discuss the mechanism of ROCK inhibitors in reducing IOP, providing neuroprotection, and preventing fibrosis. We also highlight recent studies and clinical trials evaluating the efficacy and safety of ROCK inhibitors, compare them with other clinical anti-glaucomatous medications, and outline future prospects for ROCK inhibitors in glaucoma treatment.

Identifying new drugs and targets to treat rapidly elevated intraocular pressure for angle closure and secondary glaucomas to curb visual impairment and prevent blindness

A multitude of pharmacological compounds have been shown to lower and control intraocular pressure (IOP) in numerous species of animals and human subjects after topical ocular dosing or via other routes of administration. Most researchers have been interested in finding drug candidates that exhibit a relatively long duration of action from a chronic therapeutic use perspective, for example to treat ocular hypertension (OHT), primary open-angle glaucoma and even normotensive glaucoma. However, it is equally important to seek and characterize treatment modalities which offer a rapid onset of action to help provide fast relief from quickly rising IOP that occurs in certain eye diseases. These include acute angle-closure glaucoma, primary angle-closure glaucoma, uveitic and inflammatory glaucoma, medication-induced OHT, and other secondary glaucomas induced by eye injury or infection which can cause partial or complete loss of eyesight. Such fast-acting agents can delay or prevent the need for ocular surgery which is often used to lower the dangerously raised IOP. This research survey was therefore directed at identifying agents from the literature that demonstrated ocular hypotensive activity, normalizing and unifying the data, determining their onset of action and rank ordering them on the basis of rapidity of action starting within 30-60 min and lasting up to at least 3-4 h post topical ocular dosing in different animal species. This research revealed a few health authority-approved drugs and some investigational compounds that appear to meet the necessary criteria of fast onset of action coupled with significant efficacy to reduce elevated IOP (by ≥ 20%, preferably by >30%). However, translation of the novel animal-based findings to the human conditions remains to be demonstrated but represent viable targets, especially EP2-receptor agonists (e.g. omidenepag isopropyl; AL-6598; butaprost), mixed activity serotonin/dopamine receptor agonists (e.g. cabergoline), rho kinase inhibitors (e.g. AMA0076, Y39983), CACNA2D1-gene product inhibitors (e.g. pregabalin), melatonin receptor agonists, and certain K+-channel openers (e.g. nicorandil, pinacidil). Other drug candidates and targets were also identified and will be discussed.

Identification of Nitric Oxide-Donating Ripasudil Derivatives with Intraocular Pressure Lowering and Retinal Ganglion Cell Protection Activities

Based on the synergistic therapeutic effect of nitric oxide (NO) and Rho-associated protein kinase (ROCK) inhibitors on glaucoma, a new group of NO-donating ripasudil derivatives RNO-1-RNO-6 was designed, synthesized, and biologically evaluated. The results demonstrated that the most active compound RNO-6 maintained potent ROCK inhibitory and NO releasing abilities, reversibly depolymerized F-actin, and suppressed mitochondrial respiration in human trabecular meshwork (HTM) cells. Topical administration of RNO-6 (0.26%) in chronic ocular hypertension glaucoma mice exhibited significant IOP lowering and visual function and retinal ganglion cell (RGC) protection activities, superior to an equal molar dose of ripasudil. RNO-6 could be a promising agent for glaucoma or ocular hypertension, warranting further investigation.

The active kinome: The modern view of how active protein kinase networks fit in biological research

Biological regulatory networks are dynamic, intertwined, and complex systems making them challenging to study. While quantitative measurements of transcripts and proteins are key to investigate the state of a biological system, they do not inform the "active" state of regulatory networks. In consideration of that fact, "functional" proteomics assessments are needed to decipher active regulatory processes. Phosphorylation, a key post-translation modification, is a reversible regulatory mechanism that controls the functional state of proteins. Recent advancements of high-throughput protein kinase activity profiling platforms allow for a broad assessment of protein kinase networks in complex biological systems. In conjunction with sophisticated computational modeling techniques, these profiling platforms provide datasets that inform the active state of regulatory systems in disease models and highlight potential drug targets. Taken together, system-wide profiling of protein kinase activity has become a critical component of modern molecular biology research and presents a promising avenue for drug discovery.

Discovery of 3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-one derivatives as a new class of ROCK inhibitors for the treatment of glaucoma

The Rho-associated protein kinases (ROCKs) are associated with the pathology of glaucoma and discovery of ROCK inhibitors has attracted much attention in recent years. Herein, we report a series of 3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-one derivatives as a new class of ROCK inhibitors. Structure-activity relationship studies led to the discovery of compound 12b, which showed potent activities against ROCK I and ROCK Ⅱ with IC₅₀ values of 93 nM and 3 nM, respectively. 12b also displayed considerable selectivity for ROCKs. The mean IOP-lowering effect of 12b in an ocular normotensive model was 34.3%, and no obvious hyperemia was observed. Overall, this study provides a good starting point for ROCK-targeting drug discovery against glaucoma.

Sampling trabecular meshwork using TrabEx

Background

To report sampling of the trabecular meshwork using the TrabEx+ (MicroSurgical Technology, Redmond, Washington, USA) device in ab interno trabeculectomy. Specifically, this series focusses upon preservation of the trabecular meshwork architecture for assessment of glaucomatous features using common histopathological techniques.

Patients

This series features six glaucomatous eyes undergoing TrabEx+ with or without cataract surgery. Three patients had primary open angle glaucoma and the remaining had pigment dispersion glaucoma, ocular hypertension or uveitic glaucoma. Four eyes had simultaneous cataract surgery.

Methods

Trabecular meshwork was excised using the TrabEx+ device and retrieved using vitreoretinal forceps. The samples were then processed into formalin-fixed paraffin-embedded 4 micron tissue segments and stained with haematoxylin and eosin, periodic acid–Schiff and elastin Van Gieson. Collagen IV was labelled using immunohistochemistry for the purpose of identifying the basement membrane of trabecular beams.

Results

Presence of trabecular meshwork was confirmed in five of the six samples taken. One of six samples consisted of blood only, but this was expected following early termination of the procedure due to patient restlessness. In the five positive cases trabecular beams with associated trabecular meshwork cells were identified on hematoxylin-eosin and periodic acid–Schiff staining. The beams retained their lamellar structure. The basement membrane underlying the trabecular cells was evident in three specimens, whilst two specimens were of insufficient size for collagen IV labelling.

Conclusions

This case series illustrates that TrabEx+ can be utilised to successfully retrieve trabecular meshwork samples with sufficient architectural perseveration of the tissue to enable histopathological and laboratory analysis.

Investigational Rho Kinase Inhibitors for the Treatment of Glaucoma

This review provides a comprehensive update on emerging ROCK inhibitors as an innovative treatment option for lowering intraocular pressure (IOP) in glaucoma and aims to describe the structure, mechanism of action, pharmaceutical characteristics, desirable ocular effects, including side effects for each agent. A literature review was conducted using PubMed, Scopus, clinicaltrials.gov, ARVO journals, Cochrane library and Selleckchem. Databases were searched using "investigational Rho kinase inhibitors," and "glaucoma" as keywords. In addition to this building block strategy, successive fractions were employed to further refine the results. Of the several ROCK inhibitors discovered, only two drugs are currently approved for glaucoma treatment; Netarsudil in the USA and Ripasudil in Japan and China. We identified and reviewed 15 agents currently in laboratory or clinical trials. These agents lower IOP mainly by decreasing outflow resistance through pharmacologic relaxation of the trabecular meshwork (TM) cells and reducing episcleral venous pressure. They have an optimistic safety profile; however, conjunctival hyperemia, conjunctival hemorrhage, pain on instillation, and corneal verticillata are common. Other properties such as neuroprotection (enhancing optic nerve blood flow and promoting axonal regeneration), anti-fibrotic activity, and endothelial cell proliferation may improve the visual prognosis and surgical outcomes in glaucoma. In addition, these agents have the potential to work synergistically with other topical glaucoma medications.

The Latest Drugs in Development That Reduce Intraocular Pressure in Ocular Hypertension and Glaucoma

Glaucoma causes irreversible vision loss, with elevated intraocular pressure (IOP) being the only known modifiable risk factor. There are a variety of medical and interventional options for lowering IOP; however, despite these treatments, glaucoma continues to be a leading cause of visual impairment. Further research continues to strive for treatment options with improved side effect profiles, additional IOP-lowering effects, and ease of use. This review provides a brief summary of current IOP-lowering therapies and then outlines pipeline ocular hypotensive agents, their mechanisms of action, benefits, and side effect profiles. Advancements are seen within currently used eye drop classes such as prostaglandin analogues, Rho kinase inhibitors and nitric oxide donors, whilst there are also new drug classes, such as tyrosine protein kinase activators. Most developing drugs are topical drop formulations, with a number already having entered Phase III trials. Alternative drug delivery methods are also in development and will be briefly discussed. Pharmacological and drug delivery developments continue to provide glaucoma patients and clinicians with new options and the promise of better outcomes, particularly in terms of improved tolerance and reduced frequency of dosing.

Topical administration of rapamycin promotes retinal ganglion cell survival and reduces intraocular pressure in a rat glaucoma model

Glaucoma is a progressive optic neuropathy that has become the most common cause of irreversible blindness worldwide. Studies have shown that the protein mammalian target of rapamycin (mTOR) is a serine/threonine kinase that plays a central role in regulating numerous functions, such as growth, proliferation, cytoskeletal organization, metabolism, and autophagy. Clinical trials have shown that Rho-associated protein kinase (ROCK) inhibitors reduced intraocular pressure (IOP) in patients with glaucoma and ocular hypertension (OHT). In this study, we explored whether rapamycin (RAPA) eye drops can reduce IOP and protect retinal ganglion cells (RGCs). Our results indicated that in rats treated with RAPA, the drug was detected in the aqueous humor (AH), and the IOP was reduced. This may be related to the inhibition of RhoA protein activation by RAPA and regulation of the actin cytoskeleton in trabecular meshwork (TM) cells. In addition, the retinal thickness and the survival rate of RGCs were significantly reduced in the OHT group compared with the control group. These changes in the OHT group were significantly improved after treatment with RAPA. This may be because RAPA inhibited the activation of glial cells and the release of proinflammatory factors, thereby attenuating further damage to the retina and RGCs. Taken together, the results of this study demonstrated that RAPA not only reduced IOP but also protected RGCs, suggesting that RAPA is likely to be an effective strategy for the treatment of glaucoma.

TGFβ2-Hepcidin Feed-Forward Loop in the Trabecular Meshwork Implicates Iron in Glaucomatous Pathology

Purpose

Elevated levels of transforming-growth-factor (TGF)-β2 in the trabecular meshwork (TM) and aqueous humor are associated with primary open-angle glaucoma (POAG). The underlying mechanism includes alteration of extracellular matrix homeostasis through Smad-dependent and independent signaling. Smad4, an essential co-Smad, upregulates hepcidin, the master regulator of iron homeostasis. Here, we explored whether TGF-β2 upregulates hepcidin, implicating iron in the pathogenesis of POAG.

Methods

Primary human TM cells and human and bovine ex vivo anterior segment organ cultures were exposed to bioactive TGF-β2, hepcidin, heparin (a hepcidin antagonist), or N-acetyl carnosine (an antioxidant), and the change in the expression of hepcidin, ferroportin, ferritin, and TGF-β2 was evaluated by semiquantitative RT-PCR, Western blotting, and immunohistochemistry. Increase in reactive oxygen species (ROS) was quantified with dihydroethidium, an ROS-sensitive dye.

Results

Primary human TM cells and bovine TM tissue synthesize hepcidin locally, which is upregulated by bioactive TGF-β2. Hepcidin downregulates ferroportin, its downstream target, increasing ferritin and iron-catalyzed ROS. This causes reciprocal upregulation of TGF-β2 at the transcriptional and translational levels. Heparin downregulates hepcidin, and reduces TGF-β2-mediated increase in ferritin and ROS. Notably, both heparin and N-acetyl carnosine reduce TGF-β2-mediated reciprocal upregulation of TGF-β2.

Conclusions

The above observations suggest that TGF-β2 and hepcidin form a self-sustained feed-forward loop through iron-catalyzed ROS. This loop is partially disrupted by a hepcidin antagonist and an anti-oxidant, implicating iron and ROS in TGF-β2-mediated POAG. We propose that modification of currently available hepcidin antagonists for ocular use may prove beneficial for the therapeutic management of TGF-β2-associated POAG.

Improving outcomes in retinal detachment: the potential role of rho-kinase inhibitors

PURPOSE OF REVIEW

Retinal detachment initiates a series of events that lead to degenerative changes in retinal synaptic architecture as well as the well-known phenomena of gliosis and photoreceptor apoptosis. Retinal reattachment does not always result in complete visual recovery, even if the fovea is not directly involved in the detachment. Rho-kinase (ROCK) inhibitors may mitigate some of these deleterious changes including disruption of synaptic architecture, photoreceptor apoptosis, and initiation of the epithelial-mesenchymal transition that characterizes proliferative vitreoretinopathy (PVR). This review focuses on the use of ROCK inhibitors to modulate synaptic disjunction.

RECENT FINDINGS

ROCK inhibition prevents retinal detachment-induced photoreceptor synaptic terminal retraction (i.e., synaptic disjunction), thereby diminishing the damage of the first synapse in the visual pathway. ROCK inhibition also reduces retinal detachment-induced photoreceptor apoptosis and suppresses PVR progression in preclinical models.

SUMMARY

Inhibition of ROCK may help to optimize visual recovery after retinal detachment surgery or iatrogenic detachments during cell transplantation or viral subretinal injection and might play a role in reducing the risk of PVR after retinal detachment surgery.