The effect of Rho-associated kinase inhibition on the ocular penetration of timolol maleate

A Bifunctional Peptide with Penetration Ability for Treating Retinal Angiogenesis via Eye Drops

Numerous diseases, such as diabetic retinopathy and age-related macular degeneration, can lead to retinal neovascularization, which can seriously impair the visual function and potentially result in blindness. The presence of the blood-retina barrier makes it challenging for ocularly administered drugs to penetrate physiological barriers and reach the ocular posterior segments, including the retina and choroid. Herein, we developed an innovative bifunctional peptide, Tat-C-RP7, which exhibits excellent penetration capabilities and antiangiogenic properties aimed at treating retinal neovascularization diseases. RP7 is an NRP-1 targeting peptide that blocks vascular endothelial growth factor receptor-2 (VEGFR-2) signaling and inhibits angiogenesis, while Tat facilitates the delivery of various cargoes across biological barriers, such as the blood-retina barrier. By combining these attributes, Tat-C-RP7 is anticipated to traverse ocular barriers via ocular topical administration and exert its antiangiogenic effects in the ocular posterior segment. Experimental results demonstrated that Tat-C-RP7 significantly inhibited the proliferation and migration of rat retinal microvascular endothelial cells and effectively reduced tubule formation in vitro. Its antiangiogenic activity was confirmed in zebrafish. The outstanding penetrative capabilities of FITC-labeled Tat-C-RP7 have been validated through cell uptake assays, in vitro cell barrier models, ex-vivo ocular tissues, and in vivo studies. Besides, the half-life of Tat-C-RP7 was longer than that of RP7. In an oxygen-induced retinopathy model, Tat-C-RP7 was shown to reduce the area of angiogenesis following ocular administration. Additionally, it produced no irritating effects on the eyes of rabbits. Overall, Tat-C-RP7 demonstrates excellent ocular penetrability and antiangiogenic effects and represents a promising therapeutic option for treating retinal neovascularization diseases.

Rho Kinase Inhibitors: Strategies in Glaucoma Treatment in Older Adults

Glaucoma is a leading cause of irreversible blindness which preferentially affects older individuals. No medications or therapies which are currently in our arsenal actually treat glaucoma itself. We know that intraocular pressure (IOP) is currently the only modifiable risk factor for glaucoma. The primary treatments for glaucoma include medications, laser therapies, and surgical therapies. The Rho kinase inhibitors are the newest class of medications currently on the market and in development for topical IOP-lowering therapy. Studies have shown their ability to lower eye pressure individually and in combination with other medications. Their ability to potentially provide neuroprotective effects for disease modification also gives this class exciting potential for glaucoma treatment.

The Effects of ROCK Inhibitor on Prevention of Dexamethasone-Induced Glaucoma Phenotype in Human Trabecular Meshwork Cells

Purpose

This study investigated the effects of dexamethasone (Dex) on human trabecular meshwork (TM) cells, a model of glucocorticoid-induced glaucoma, and evaluated the impact of ripasudil (Rip) as a co-delivery or sequential dosing strategy.

Methods

In vitro experiments were conducted to assess the effects of Dex and Rip on TM cells. Confocal microscopy was used to evaluate the impact of Dex and Rip on F-actin staining signals. Contractility of the TM cells upon Dex and Rip treatment mimicking co-delivery and sequential delivery was quantified using collagen gel contraction assay. Transepithelial electrical resistance (TEER) values and fluorescein isothiocyanate (FITC)-dextran permeability were also measured to assess the impact of Dex and Rip on TM cells.

Results

Dex and Rip did not exhibit cytotoxicity at the maximum tested concentration (20 µM). Dex-treated TM cells exhibited higher F-actin staining signals compared to controls, which were reduced when co-treated with Rip. Rip inhibited Dex-induced collagen gel contraction activity in both co-delivery and sequential treatments. Dex resulted in increased TEER values as the dose increased, whereas TEER values were maintained when co-treated with Rip.

Conclusions

Co-delivery of Rip has the potential to prevent glaucoma symptoms when patients are treated with Dex. This study highlights the importance of identifying strategies to reduce the side effects of prolonged use of glucocorticoids, such as Dex, in the treatment of various diseases.

Translational Relevance

This study demonstrates the potential of co-delivering ripasudil with dexamethasone to mitigate glucocorticoid-induced ocular hypertension and a secondary glaucoma that resembles primary open-angle glaucoma, providing insights for the development of novel preventive strategies in clinical care.

In Situ Gelling Electrospun Ocular Films Sustain the Intraocular Pressure-Lowering Effect of Timolol Maleate: In Vitro, Ex Vivo, and Pharmacodynamic Assessment

Most common intraocular pressure (IOP) reduction regimens for the management of glaucoma include the topical use of eye drops, a dosage form that is associated with short residence time at the site of action, increased dosing frequency, and reduced patient compliance. In situ gelling nanofiber films comprising poly(vinyl alcohol) and Poloxamer 407 were fabricated via electrospinning for the ocular delivery of timolol maleate (TM), aiming to sustain the IOP-lowering effect of the β-blocker, compared to conventional eye drops. The electrospinning process was optimized, and the physicochemical properties of the developed formulations were thoroughly investigated. The fiber diameters of the drug-loaded films ranged between 123 and 145 nm and the drug content between 5.85 and 7.83% w/w. Total in vitro drug release from the ocular films was attained within 15 min following first-order kinetics, showing higher apparent permeability (P_app) values across porcine corneas compared to the drug's solution. The fabricated films did not induce any ocular irritation as evidenced by both the hen's egg test on chorioallantoic membrane and the in vivo Draize test. In vivo administration of the ocular films in rabbits induced a faster onset of action and a sustained IOP-lowering effect up to 24 h compared to TM solution, suggesting that the proposed ocular films are promising systems for the sustained topical delivery of TM.

Status of Rho kinase inhibitors in glaucoma therapeutics-an overview

Medical management remains the cornerstone of glaucoma management despite advances in the surgical or laser procedures. After a leap of almost two decades of the advent of prostaglandin analogues, recently a new class of drug, Rho kinase (ROCK) inhibitors, has come to limelight because of their varied therapeutic potential in different clinical conditions of eye, especially glaucoma. Their efficacy of lowering intraocular pressure (IOP) by virtue of an entirely different mechanism of decreasing outflow resistance has ignited a series of clinical trials evaluating their potential as monotherapy or as adjunct to existing antiglaucoma medications, and three of them ripasudil, netarsudil and roclatan have even been approved for clinical use in the recent past. There are evidences suggesting their beneficial effects in glaucoma patients even via non-IOP-dependent mechanisms like neuroprotection by improving blood flow to the optic nerve and increasing ganglion cell survival. They can even act as antifibrotic agents and reduce bleb scarring after glaucoma surgery. Hence, their effective role in glaucomatous optic neuropathy is multifaceted primary being improved drainage through the conventional pathway. On the other hand, certain local adverse effects like conjunctival hyperaemia have been reported in substantial proportion of patients, while some others like blepharitis, subconjunctival haemorrhages and cornea verticillata constitute less common side effects. The purpose of this review is to summarize the discovery, evolution and recent update of clinical trials on Rho kinase inhibitors as antiglaucoma medicine and to delineate their role in existing management protocol.

An Overview of Advanced In Vitro Corneal Models: Implications for Pharmacological Testing

The cornea is an important barrier to consider when developing ophthalmic formulations, but proper modeling of this multilayered tissue remains a challenge. This is due to the varying properties associated with each layer in addition to the dynamics of the tear film. Hence, the most representative models to date rely on animals. Animal models, however, differ from humans in several aspects and are subject to ethical limitations. Consequently, in vitro approaches are being developed to address these issues. This review focuses on the barrier properties of the cornea and evaluates the most advanced three-dimensional cultures of human corneal equivalents in literature. Their application potential is subsequently assessed and discussed in the context of preclinical testing along with our perspective toward the future. Impact statement Most ocular drugs are applied topically, with the transcorneal pathway as the main administration route. Animal corneas are currently the only advanced models available, contributing to the drug attrition rate. Anatomical and physiological interspecies differences might account for a poor translatability of preclinical results to clinical trials, urging researchers to devise better corneal equivalents. This review elaborates on the emerging generation of three-dimensional in vitro models, which comprises spheroids, organoids, and organs-on-chips, which can serve as a stepping stone for advancements in this field.

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.

Sunitinib malate-loaded biodegradable microspheres for the prevention of corneal neovascularization in rats

Corneal neovascularization (NV) predisposes patients to compromised corneal transparency and visional acuity. Sunitinib malate (Sunb-malate) targeting against multiple receptor tyrosine kinases, exerts potent antiangiogenesis. However, the rapid clearance of Sunb-malate eye drops administered through topical instillation limits its therapeutic efficacy and poses a challenge for potential patient compliance. Sunb-malate, the water-soluble form of sunitinib, was shown to have higher intraocular penetration through transscleral diffusion following subconjunctival (SCT) injection in comparison to its sunitinib free base formulation. However, it is difficult to load highly water-soluble drugs and achieve sustained drug release. We developed Sunb-malate loaded poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres (Sunb-malate MS) with a particle size of approximately 15 μm and a drug loading of 7 wt%. Sunb-malate MS sustained the drug release for 30 days under the in vitro infinite sink condition. Subconjunctival (SCT) injection of Sunb-malate MS provided a prolonged ocular drug retention and did not cause ocular toxicity at a dose of 150 μg of active agent. Sunb-malate MS following SCT injection more effectively suppressed the suture-induced corneal NV than either Sunb-malate free drug or the placebo MS. Local sustained release of Sunb-malate through the SCT injection of Sunb-malate MS mitigated the proliferation of vascular endothelial cells and the recruitment of mural cells into the cornea. Moreover, the gene upregulation of proangiogenic factors induced by the pathological process was greatly neutralized by SCT injection of Sunb-malate MS. Our findings provide a sustained release platform for local delivery of tyrosine kinase inhibitors to treat corneal NV.

Ocular co-Delivery of Timolol and Brimonidine from a Self-Assembling Peptide Hydrogel for the Treatment of Glaucoma: In Vitro and Ex Vivo Evaluation

Effective pharmacotherapy during glaucoma treatment depends on interventions that reduce intraocular pressure (IOP) and retain the IOP lowering effect for sufficient time so as to reduce dosing frequency and enhance patient adherence. Combination anti-glaucoma therapy and dosage forms that increase precorneal residence time could therefore constitute a promising therapeutic intervention. The in-situ gel forming self-assembling peptide ac-(RADA)4-CONH2 was evaluated as carrier for the ocular co-delivery of timolol maleate (TM) and brimonidine tartrate (BR). The hydrogel's microstructure and mechanical properties were assessed with atomic force microscopy and rheology, respectively. Drug diffusion from the hydrogel was evaluated in vitro in simulated tear fluid and ex vivo across porcine corneas and its effect on the treated corneas was assessed through physicochemical characterization and histological analysis. Results indicated that TM and BR co-delivery affected hydrogel's microstructure resulting in shorter nanofibers and a less rigid hydrogel matrix. Rapid and complete release of both drugs was achieved within 8 h, while a 2.8-fold and 5.4-fold higher corneal permeability was achieved for TM and BR, respectively. No significant alterations were induced in the structural integrity of the corneas treated with the hydrogel formulation, suggesting that self-assembling peptide hydrogels might serve as promising systems for combination anti-glaucoma therapy.

Controlled release of corticosteroid with biodegradable nanoparticles for treating experimental autoimmune uveitis

Noninfectious uveitis is a potentially blinding ocular condition that often requires treatment with corticosteroids to prevent inflammation-related ocular complications. Severe forms of uveitis such as panuveitis that affects the whole eye often require a combination of topical and either regional or systemic corticosteroid. Regional corticosteroids are currently delivered inside the eye by intravitreal injection (e.g. Ozurdex®, an intravitreal dexamethasone implant). Intravitreal injection is associated with rare but potentially serious side effects, including endophthalmitis, retinal and vitreous hemorrhage, and retinal detachment. Subconjunctival (SCT) injection is a less invasive option that is a common route used for post-surgical drug administration and treatment of infection and severe inflammation. However, it is the water soluble form of dexamethasone, dexamethasone sodium phosphate (DSP), that has been demonstrated to achieve high intraocular penetration with subconjunctival injection. It is difficult to load highly water soluble drugs, such as DSP, and achieve sustained drug release using conventional encapsulation methods. We found that use of carboxyl-terminated poly(lactic-co-glycolic acid) (PLGA) allowed encapsulation of DSP into biodegradable nanoparticles (NP) with relatively high drug content (6% w/w) if divalent zinc ions were used as an ionic "bridge" between the PLGA and DSP. DSP-Zn-NP had an average diameter of 210 nm, narrow particle size distribution (polydispersity index ~0.1), and near neutral surface charge (-9 mV). DSP-Zn-NP administered by SCT injection provided detectable DSP levels in both the anterior chamber and vitreous chamber of the eye for at least 3 weeks. In a rat model of experimental autoimmune uveitis (EAU), inflammation was significantly reduced in both the front and back of the eye in animals that received a single SCT injection of DSP-Zn-NP as compared to animals that received either aqueous DSP solution or phosphate buffered saline (PBS). DSP-Zn-NP efficacy was evidenced by a reduced clinical disease score, decreased expression of various inflammatory cytokines, and preserved retinal structure and function. Furthermore, SCT DSP-Zn-NP significantly reduced microglia cell density in the retina, a hallmark of EAU in rats. DSP-Zn-NP hold promise as a new strategy to treat noninfectious uveitis and potentially other ocular inflammatory disorders.

The Ocular Hypotensive Efficacy of Topical Fasudil, a Rho-Associated Protein Kinase Inhibitor, in Patients With End-Stage Glaucoma

To investigate the effects of topical administration of a selective Rho-associated kinase (ROCK) inhibitor, fasudil 0.5% and 1.2% in glaucomatous patients. In this interventional case series study, 4 eyes of 4 patients with unilateral end-stage primary open-angle glaucoma and no light perception vision were assigned to receive topical fasudil 0.5% (in 3 eyes) or 1.2% (in 1 eye) ophthalmic solution twice daily for 8 weeks. At weeks 1, 2, 3, 4, and 8, intraocular pressure (IOP) and adverse events were evaluated. Baseline mean IOP was 53.5 ± 3.4 mm Hg and mean IOP reductions of the last visit were -8.25 ± 1.2 mm Hg at 2 hours and -8.75 ± 2.2 mm Hg at 4 hours. Mean IOP reductions were clinically and statistically significant with 0.5% and 1.2% fasudil and peak effects occurred 2-4 hours after application (P = 0.0002). The largest IOP reductions were produced by 1.2% fasudil (up to -12 mm Hg). Conjunctival hyperemia was found in 1 patient with 1.2% fasudil. Topical administration of fasudil in end-stage primary open-angle glaucoma patients, caused reduction in IOP and was well tolerated. ROCK inhibitors could be considered as a candidate for glaucoma therapy in future.

Self-Assembling Peptide Nanofiber Hydrogels for Controlled Ocular Delivery of Timolol Maleate

The self-assembling peptides Ac-(RADA)₄-CONH₂ and Ac-(IEIK)₃I-CONH₂, which form hydrogels in physiological conditions, were evaluated as carriers for ocular delivery of the β-blocker timolol maleate. Electron microscopy studies revealed that hydrogels contain nanofibers, whereas rheological studies showed that the Ac-(IEIK)₃I-CONH₂ self-assembles in a stiffer hydrogel compared with the Ac-(RADA)₄-CONH₂ peptide. The in vitro release and ex vivo permeation studies demonstrated controlled release and transport of the drug through the cornea, which depended on the self-assembling peptide sequence. In vivo studies in rabbits showed significant increase in the area under the concentration-time curve (AUC) after administration of the drug through the Ac-(RADA)₄-CONH₂ hydrogel compared to drug solution, whereas a sustained reduction of intraocular pressure for up to 24 h after instillation was achieved for both drug-loaded hydrogels. Histological studies revealed good ocular tolerability upon application of the formulations, suggesting that self-assembling peptide hydrogels are promising systems for sustained ocular drug delivery.

Ocular Penetration and Pharmacokinetics of Ripasudil Following Topical Administration to Rabbits

PURPOSE

We evaluated the ocular pharmacokinetics of ripasudil (K-115), a selective Rho-associated coiled-coil containing protein kinase (ROCK) inhibitor, following topical administration to rabbits.

METHODS

We determined the ocular distribution of [(14)C]ripasudil by whole-head autoradiography and the radioactivity of each ocular tissue after single and multiple instillation of [(14)C]ripasudil to pigmented rabbits. We also measured the aqueous humor concentrations after concomitant instillation of ripasudil and a combination agent (0.005% latanoprost and 0.5% timolol) to pigmented rabbits as well as the tear fluid concentrations after instillation into rabbits, dogs, and monkeys using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Membrane permeability was evaluated using an in vitro parallel artificial membrane permeability assay system and Ussing chamber with rabbit cornea and conjunctiva.

RESULTS

[(14)C]Ripasudil was rapidly absorbed into the cornea and distributed throughout the eye after topical instillation. The melanin-containing ocular tissues, such as the iris-ciliary body and retina-choroid, showed much higher concentrations of radioactivity than the other nonpigmented tissues. Concomitant instillation showed minor effects on the aqueous humor concentrations of each compound in rabbits. Membrane permeability of ripasudil was higher than other glaucoma drugs in vitro and ex vivo. The aqueous humor concentrations of ripasudil in rabbits were higher than those in dogs and monkeys in the early period after instillation and associated with tear turnover rate.

CONCLUSIONS

These results indicate favorable intraocular penetration characteristics of ripasudil following topical administration.

Topical delivery of a Rho-kinase inhibitor to the cornea via mucoadhesive film

The application of inhibitors of the Rho kinase pathway (ROCK inhibitors) to the surface of the eye in the form of eyedrops has beneficial effects which aid the recovery of diseased or injured endothelial cells that line the inner surface of the cornea. The aim of this study was to test the plausibility of delivering a selective ROCK inhibitor, Y-27632, to the cornea using a thin polymeric film. Mucoadhesive polymeric thin films were prepared incorporating Y-27632 and diffusional release into PBS was determined. Topical ocular delivery from the applied film was investigated using freshly excised porcine eyes and eyedrops of equivalent concentration acted as comparators; after 24h the formulations were removed and the corneas extracted. Drug-loaded thin polymeric films, with high clarity and pliability were produced. ROCK inhibitor Y-27632 was weakly retained within the film, with release attaining equilibrium after 1h. This in turn facilitated its rapid ocular delivery, and an approximately three-fold greater penetration of Y-27632 into cryoprobe-treated corneas was observed from the thin film (p<0.01) compared to eyedrops. These findings support the further development of ROCK inhibitor delivery to the cornea via release from thin mucoadhesive films to treat vision loss cause by corneal endothelial dysfunction.

Rho Kinase (ROCK) Inhibitors and Their Therapeutic Potential

Rho kinases (ROCKs) belong to the serine-threonine family, the inhibition of which affects the function of many downstream substrates. As such, ROCK inhibitors have potential therapeutic applicability in a wide variety of pathological conditions including asthma, cancer, erectile dysfunction, glaucoma, insulin resistance, kidney failure, neuronal degeneration, and osteoporosis. To date, two ROCK inhibitors have been approved for clinical use in Japan (fasudil and ripasudil) and one in China (fasudil). In 1995 fasudil was approved for the treatment of cerebral vasospasm, and more recently, ripasudil was approved for the treatment of glaucoma in 2014. In this Perspective, we present a comprehensive review of the physiological and biological functions for ROCK, the properties and development of over 170 ROCK inhibitors as well as their therapeutic potential, the current status, and future considerations.

An emerging treatment option for glaucoma: Rho kinase inhibitors

Rho kinase (ROCK) inhibitors are a novel potential class of glaucoma therapeutics with multiple compounds currently in Phase II and III US Food and Drug Administration trials in the United States. These selective agents work by relaxing the trabecular meshwork through inhibition of the actin cytoskeleton contractile tone of smooth muscle. This results in increased aqueous outflow directly through the trabecular meshwork, achieving lower intraocular pressures in a range similar to prostaglandins. There are also animal studies indicating that ROCK inhibitors may improve blood flow to the optic nerve, increase ganglion cell survival, and reduce bleb scarring in glaucoma surgery. Given the multiple beneficial effects for glaucoma patients, ROCK inhibitors are certainly a highly anticipated emerging treatment option for glaucoma.

Rho kinase inhibitors: a patent review (2012 - 2013)

INTRODUCTION

The Rho kinase/ROCK is critical in vital signal transduction pathways central to many essential cellular activities. Since ROCK possess multiple substrates, modulation of ROCK activity is useful for treatment of many diseases.

AREAS COVERED

Significant progress has been made in the development of ROCK inhibitors over the past two years (Jan 2012 to Aug 2013). Patent search in this review was based on FPO IP Research and Communities and Espacenet Patent Search. In this review, patent applications will be classified into four groups for discussions. The grouping is mainly based on structures or scaffolds (groups 1 and 2) and biological functions of ROCK inhibitors (groups 3 and 4). These four groups are i) ROCK inhibitors based on classical structural elements for ROCK inhibition; ii) ROCK inhibitors based on new scaffolds; iii) bis-functional ROCK inhibitors; and iv) novel applications of ROCK inhibitors.

EXPERT OPINION

Although currently only one ROCK inhibitor (fasudil) is used as a drug, more drugs based on ROCK inhibition are expected to be advanced into market in the near future. Several directions should be considered for future development of ROCK inhibitors, such as soft ROCK inhibitors, bis-functional ROCK inhibitors, ROCK2 isoform-selective inhibitors, and ROCK inhibitors as antiproliferation agents.

Rho-kinase inhibitors offer a new approach in the treatment of glaucoma

INTRODUCTION

Primary open-angle glaucoma (POAG) is a leading cause for worldwide blindness and is characterized by progressive optic nerve damage. The etiology of POAG is unknown, but elevated intraocular pressure (IOP) and advanced age have been identified as risk factors. IOP reduction is the only known treatment for glaucoma. Recently, drugs that inhibit rho-associated protein kinase (ROCK) have been studied in animals and people for their ability to lower IOP and potentially treat POAG. ROCK inhibitors lower IOP through a trabecular mechanism and may represent a new therapeutic paradigm for the treatment of POAG.

AREAS COVERED

Exploring the place that ROCK inhibitors may occupy in our treatment of POAG requires a thorough understanding of pathophysiology and treatment. This article summarizes current research on the incidence, proposed etiologies and mechanisms of action for this drug class. ROCK inhibitor research is presented and considered in light of the current standard of pharmacologic care.

EXPERT OPINION

ROCK inhibitors alter the cell shape and extracellular matrix (ECM) of the trabecular meshwork. Preclinical studies demonstrate that these drugs have the potential to become a new therapy for glaucoma. However, ROCK inhibitors can affect multiple cell types, and their utility can be proven only after clinical studies in patients.