Antiglaucoma EP2 Agonists: A Long Road That Led Somewhere

Human experience and efficacy of omidenepag isopropyl (Eybelis®; Omlonti®): Discovery to approval of the novel non-prostaglandin EP2-receptor-selective agonist ocular hypotensive drug

More than 75 million people worldwide suffer from ocular hypertension (OHT)-associated retinal and optic nerve degenerative diseases that cause visual impairment and can lead to blindness. In an effort to find novel pharmaceutical therapeutics to combat OHT with reduced side-effect potential, several emerging drug candidates have advanced to human proof-of-concept in recent years. One such compound is a nonprostaglandin (non-PG) EP2-receptor-selective agonist (omidenepag isopropyl ester). Omidenepag (OMD; free acid form) is a novel non-PG that selectively binds to and activates the human EP2-prostglandin receptor (EP2R) with a high affinity (Ki = 3.6 nM) and which potently generates intracellular cAMP in living cells (EC50 = 3.9-8.3 nM). OMD significantly downregulated COL12A1 and COL13A1 mRNAs in human trabecular meshwork (TM) cells, a tissue involved in the pathogenesis of OHT. Omidenepag isopropyl (OMDI) potently and efficaciously lowered intraocular pressure (IOP) in ocular normotensive rabbits, dogs, and monkeys, and also in ocular hypertension (OHT) Cynomolgus monkeys, after a single topical ocular (t.o.) instillation at doses of 0.0001-0.01%. No reduction in IOP-lowering response to OMDI was observed after repeated t.o. dosing with OMDI in dogs and monkeys. Additive IOP reduction to OMDI was noted with brinzolamide, timolol, and brimonidine in rabbits and monkeys. OMDI 0.002% t.o. decreased IOP by stimulating the conventional (TM) and uveoscleral (UVSC) outflow of aqueous humor (AQH) in OHT monkeys. In a Phase-III clinical investigation, 0.002% OMDI (once daily t.o.) reduced IOP by 5-6 mmHg in OHT/primary open-angle glaucoma (POAG) patients (22-34 mmHg baseline IOPs) that was maintained over 12-months. In an additional month-long clinical study, 0.002% OMDI induced IOP-lowering equivalent to that of latanoprost (0.005%), a prostanoid FP-receptor agonist, thus OMDI was noninferior to latanoprost. Additive IOPreduction was also noted in OHT/OAG patients when OMDI (0.002%, once daily t.o.) and timolol (0.05%, twice daily t.o.) were administered. Patients with OHT/POAG who were low responders or nonresponders to latanoprost (0.005%, q.d.; t.o.) experienced significant IOP-lowering (additional approximately 3 mmHg) when they were switched over to OMDI 0.002% (q.d.; t.o.). No systemic or ocular adverse reactions (e.g. iris color changes/deepening of the upper eyelid sulcus/abnormal eyelash growth) were noted after a year-long, once-daily t.o. dosing with 0.002 % OMDI in OHT/POAG patients. However, OMDI caused transient conjunctival hyperemia. These characteristics of OMDI render it a suitable new medication for treating OHT and various types of glaucoma, especially where elevated IOP is implicated.

Recently Approved Drugs for Lowering and Controlling Intraocular Pressure to Reduce Vision Loss in Ocular Hypertensive and Glaucoma Patients

Serious vision loss occurs in patients affected by chronically raised intraocular pressure (IOP), a characteristic of many forms of glaucoma where damage to the optic nerve components causes progressive degeneration of retinal and brain neurons involved in visual perception. While many risk factors abound and have been validated for this glaucomatous optic neuropathy (GON), the major one is ocular hypertension (OHT), which results from the accumulation of excess aqueous humor (AQH) fluid in the anterior chamber of the eye. Millions around the world suffer from this asymptomatic and progressive degenerative eye disease. Since clinical evidence has revealed a strong correlation between the reduction in elevated IOP/OHT and GON progression, many drugs, devices, and surgical techniques have been developed to lower and control IOP. The constant quest for new pharmaceuticals and other modalities with superior therapeutic indices has recently yielded health authority-approved novel drugs with unique pharmacological signatures and mechanism(s) of action and AQH drainage microdevices for effectively and durably treating OHT. A unique nitric oxide-donating conjugate of latanoprost, an FP-receptor prostaglandin (PG; latanoprostene bunod), new rho kinase inhibitors (ripasudil; netarsudil), a novel non-PG EP2-receptor-selective agonist (omidenepag isopropyl), and a form of FP-receptor PG in a slow-release intracameral implant (Durysta) represent the additions to the pharmaceutical toolchest to mitigate the ravages of OHT. Despite these advances, early diagnosis of OHT and glaucoma still lags behind and would benefit from further concerted effort and attention.

Influence of 0.002% Omidenepag Isopropyl on Intraocular Pressure and the Cornea in Normal Tension Glaucoma

PRCIS

Although Omidenepag isopropyl drops elicited stable intraocular pressure reductions in NTG patients, transient changes in refraction and corneal endothelial cells, significant increase of central corneal thickness, and corneal erosion should be considered.

PURPOSE

To analyze the efficacy and safety of 0.002% omidenepag Isopropyl (OMDI) eye drops in patients with normal tension glaucoma (NTG).

METHODS

Medical records for 62 eyes treated with OMDI for ≥6 months were analyzed. Intraocular pressure (IOP), refraction, keratometry, central corneal thickness (CCT), endothelial cell count, coefficient of variation of endothelial cell area (CV), corneal erosion, and central retinal thickness were compared at baseline and 1, 3, and 6 months.

RESULTS

IOP significantly decreased from 13.4±3.8 to 11.9±3.0, 11.7±2.9, and 12.2±3.3 mm Hg at each follow-up ( P <0.001). Endothelial cell count did not change, but CV transiently increased from 12.6 to 17.0 at 1 month, CCT increased from 531.5 to 538.4 μm, myopia changed from -1.5 to -1.9 D, and keratometry changed from 44.5 to 44.7 D. CV, myopia, and keratometry recovered to baseline at 6 months; however, CCT remained high. Significant corneal erosion was observed at 6 months. Central retinal thickness changes were not observed. There were improvements in prostaglandin-associated skin pigmentation (86.7%), eyelash elongation (40.0%), and deepening of the upper eyelid sulcus and ptosis (~30%) at 3 months after exchange to OMDI. Adverse reactions were corneal erosion (27.4%), corneal thickening (21.0%), conjunctival hyperemia (11.3%), photophobia (5.7%), blurred vision (5.7%), and anterior chamber cells (4.8%).

CONCLUSIONS

OMDI eye drops elicited significant and stable IOP reductions after 6 months in NTG patients with low IOP. However, transient myopic and corneal endothelial cell changes, development of corneal thickening, and corneal erosion should be considered when using OMDI.

FP and EP2 prostanoid receptor agonist drugs and aqueous humor outflow devices for treating ocular hypertension and glaucoma

Prostaglandin (PG) receptors represent important druggable targets due to the many diverse actions of PGs in the body. From an ocular perspective, the discovery, development, and health agency approvals of prostaglandin F (FP) receptor agonists (FPAs) have revolutionized the medical treatment of ocular hypertension (OHT) and glaucoma. FPAs, such as latanoprost, travoprost, bimatoprost, and tafluprost, powerfully lower and control intraocular pressure (IOP), and became first-line therapeutics to treat this leading cause of blindness in the late 1990s to early 2000s. More recently, a latanoprost-nitric oxide (NO) donor conjugate, latanoprostene bunod, and a novel FP/EP3 receptor dual agonist, sepetaprost (ONO-9054 or DE-126), have also demonstrated robust IOP-reducing activity. Moreover, a selective non-PG prostanoid EP2 receptor agonist, omidenepag isopropyl (OMDI), was discovered, characterized, and has been approved in the United States, Japan and several other Asian countries for treating OHT/glaucoma. FPAs primarily enhance uveoscleral (UVSC) outflow of aqueous humor (AQH) to reduce IOP, but cause darkening of the iris and periorbital skin, uneven thickening and elongation of eyelashes, and deepening of the upper eyelid sulcus during chronic treatment. In contrast, OMDI lowers and controls IOP by activation of both the UVSC and trabecular meshwork outflow pathways, and it has a lower propensity to induce the aforementioned FPA-induced ocular side effects. Another means to address OHT is to physically promote the drainage of the AQH from the anterior chamber of the eye of patients with OHT/glaucoma. This has successfully been achieved by the recent approval and introduction of miniature devices into the anterior chamber by minimally invasive glaucoma surgeries. This review covers the three major aspects mentioned above to highlight the etiology of OHT/glaucoma, and the pharmacotherapeutics and devices that can be used to combat this blinding ocular disease.

Efficacy and Patient Tolerability of Omidenepag Isopropyl in the Treatment of Glaucoma and Ocular Hypertension

Current therapeutic approaches for glaucoma aim to reduce intraocular pressure (IOP), which is the only available and reliable strategy proven to control the risk of disease development and progression. Omidenepag isopropyl (OMDI) is a novel topical ocular hypotensive agent that was launched onto the market for the treatment of glaucoma and ocular hypertension (OHT). After topical instillation and during corneal penetration, OMDI is converted into the active metabolite omidenepag (OMD), which behaves as a non-prostaglandin, selective E-prostanoid subtype 2 (EP2) receptor agonist. The topical administration of 0.002% OMDI once-daily (QD) possesses a 20–35% IOP-lowering effect, comparable to that of prostaglandin analogs targeting F-prostanoid (FP) receptor QD, which are the current first-line for pharmaceutical reduction of IOP. However, the mechanism of action and adverse events (AEs) of OMDI are different from those of FP receptor agonists. OMDI reduces IOP by enhancing both conventional trabecular and uveoscleral outflow facilities without complications of prostaglandin-associated periorbitopathy (PAP) seen with FP receptor agonists. Moreover, OMDI was also effective and well-tolerated in non-/poor responders to latanoprost and showed a stable IOP-lowering effect for one year, and its concomitant use with timolol enhanced the IOP-lowering effect. OMDI demonstrated acceptable safety and tolerability with good adherence and can be used in almost every patient. However, OMDI has some AEs such as conjunctival hyperemia, corneal thickening, macular edema/cystoid macular edema and ocular inflammation. Moreover, OMDI is contraindicated in patients who are allergic to the product, in aphakic or pseudophakic eyes, and in combination with tafluprost eye drops. If used appropriately in the right patients, OMDI could be an effective treatment option for glaucoma and OHT as a first-line alternative to FP agonists. Here, we summarize the results of clinical studies of OMDI and discuss its efficacy and patient tolerability in glaucoma and OHT in this review.

Prostaglandin-associated periorbitopathy syndrome (PAPS): Addressing an unmet clinical need

BACKGROUND

Topical prostaglandin analogs (PGAs) are widely approved and preferred first-line options for glaucoma and elevated intraocular pressure (IOP). However, prostaglandin-associated periorbitopathy syndrome (PAPS) is now a well-recognized clinical and cosmetic concern for patients receiving PGAs, especially during long-term and unilateral therapy. PGA-associated periocular changes occur in a substantial proportion of patients, with older patients (>60 years) at greater risk of clinical presentation. PAPS may hinder long-term management of glaucoma, including treatment adherence, ophthalmic surgery outcomes, and reliable IOP measurements.

RECOMMENDATION

New therapeutic approaches may address this unmet clinical need. Omidenepag isopropyl (OMDI) is a novel, non-prostaglandin, selective EP₂ receptor agonist in ongoing development, which provides a unique pharmacological mechanism of action. OMDI appears to provide IOP reductions comparable to PGAs, but without PAPS-related undesirable effects. OMDI may offer a suitable long-term option for patients who demonstrate decreased efficacy, or failure, of PGAs, plus patients with significant PAPS, while fulfilling international guidelines.

Prostanoid receptor agonists for glaucoma treatment

Intraocular pressure reduction is the only available and evidence-based medical therapy for glaucoma. Currently, the first-line eye drops are prostaglandin analogues including latanoprost, travoprost, bimatoprost, and tafluprost. These drugs stimulate intraocular prostanoid false positive (FP) receptors and reduce intraocular pressure by increasing mainly uveoscleral aqueous outflow. For 2 decades since latanoprost was launched, no drug has been comparable in its efficacy. In 2018, a prostanoid EP2 agonist, omidenepag, was launched in Japan. Current FP agonists and EP2 agonists indicate comparable intraocular pressure reduction by stimulating prostanoid FP or EP2 receptors. However, their safety profiles are quite different because of the differences between the intracellular signaling pathways through their own receptors. Including these commercially available FP and EP2 receptor agonists, prostanoid receptors have a large potential to control intraocular pressure. In this review I will trace the history and development of FP and EP2 receptor agonists from their original function, and explain their potential as first-line drugs including elucidation of their efficacy and safety.

The role of EP2 receptors in mediating the ultra-long-lasting intraocular pressure reduction by JV-GL1

BACKGROUND

A single application of JV-GL1 substantially lowers non-human primate intraocular pressure (IOP) for about a week, independent of dose. This highly protracted effect does not correlate with its ocular biodisposition or correlate with the once-daily dosing regimen for other prostanoid EP₂ receptor agonists such as trapenepag or omidenepag. The underlying pharmacological mechanism for the multiday extended activity of JV-GL1 is highly intriguing. The present studies were intended to determine EP₂ receptor involvement in mediating the long-term ocular hypotensive activity of JV-GL1 by using mice genetically deficient in EP₂ receptors.

METHODS

The protracted IOP reduction produced by JV-GL1 was investigated in C57BL/6J and EP₂ receptor knock-out mice (B6.129-Ptger2^tm1Brey /J; EP₂KO). Both ocular normotensive and steroid-induced ocular hypertensive (SI-OHT) mice were studied. IOP was measured tonometrically under general anaesthesia. Aqueous humour outflow facility was measured ex vivo using iPerfusion in normotensive C57BL/6J mouse eyes perfused with 100 nM de-esterified JV-GL1 and in SI-OHT C57BL/6J mouse eyes that had received topical JV-GL1 (0.01%) 3 days prior.

RESULTS

Both the initial 1-day and the protracted multiday effects of JV-GL1 in the SI-OHT model for glaucoma were abolished by deletion of the gene encoding the EP₂ receptor. Thus, JV-GL1 did not lower IOP in SI-OHT EP₂KO mice, but in littermate SI-OHT EP₂WT control mice, JV-GL1 statistically significantly lowered IOP for 4-6 days.

CONCLUSIONS

Both the 1-day and the long-term effects of JV-GL1 on IOP are entirely EP₂ receptor dependent.