Ocular Normotensive Monkeys Research Articles

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.

Efficacy and safety of the fixed combinations of tafluprost/timolol and latanoprost/carteolol

In this study, we made a comparative efficacy and safety assessment of two different fixed combinations of drugs, viz., tafluprost/timolol (TAF/TIM) and latanoprost/carteolol (LAT/CAR), by determining their effects on intraocular pressure (IOP) in ocular normotensive monkeys and examining their toxic effects on ocular surface using human corneal epithelial cells. TAF/TIM was found to be more effective in lowering IOP for a longer duration compared to LAT/CAR. We found that the difference in the intensity of IOP-lowering effect was because of the differences in the strength of timolol compared with that of carteolol as a beta-adrenergic antagonist and strength of tafluprost compared with that of latanoprost as a prostaglandin analogue. In addition, TAF/TIM showed much less cytotoxic effects compared to LAT/CAR on the human corneal epithelial cells. Our findings showed that TAF/TIM is better than LAT/CAR with regard to the IOP-lowering effect in monkeys and toxicity on ocular surface.

Identification of a Selective, Non-Prostanoid EP2 Receptor Agonist for the Treatment of Glaucoma: Omidenepag and its Prodrug Omidenepag Isopropyl.

EP2 receptor agonists are expected to be effective ocular hypotensive agents; however, it has been suggested that agonism to other EP receptor subtypes may lead to undesirable effects. Through medicinal chemistry efforts, we identified a scaffold bearing a (pyridin-2-ylamino)acetic acid moiety as a promising EP2-selective receptor agonist. (6-((4-(Pyrazol-1-yl)benzyl)(pyridin-3-ylsulfonyl)aminomethyl)pyridin-2-ylamino)acetic acid 13ax (omidenepag, OMD) exerted potent and selective activity toward the human EP2 receptor (h-EP2). Low doses of omidenepag isopropyl (OMDI), a prodrug of 13ax, lowered intraocular pressure (IOP) in ocular normotensive monkeys. OMDI was selected as a clinical candidate for the treatment of glaucoma.

IOP-lowering effect of isoquinoline-5-sulfonamide compounds in ocular normotensive monkeys

Rho-associated coiled coil-formed protein kinase (ROCK) inhibitors are under development as a new class of antiglaucoma agents. Based on the potent ROCK inhibitor H-1152, previously developed by us, we explored the possibility of related compounds as antiglaucoma agents and synthesized seven types of H-1152-inspired isoquinoline-5-sulfonamide compounds (H-0103–H-0107, H-1001, H-1005). Although all of these compounds potently inhibited ROCK (IC50=18–48nM), only H-0104 and H-0106 exerted strong intraocular pressure (IOP)-lowering effects into the eyes of monkeys. These results suggested the possibility that there is no direct relationship between ROCK inhibition and IOP-lowering effects, indicating that the initial screening of compounds based on ROCK inhibitory activity may be an unsuitable strategy for developing antiglaucoma agents with potent IOP-lowering effects.

Ocular Hypotensive Effect of Tafluprost in Latanoprost Low-responder Cynomolgus Monkeys

To determine the proportion of latanoprost low-responders among cynomolgus monkeys, and to evaluate the switching efficacy from latanoprost to tafluprost in latanoprost low-responder monkeys. Thirty-nine ocular normotensive monkeys were used in this study. Latanoprost low-responders were detected using a 2-step evaluation procedure. In the first step, the response to single administration of latanoprost was investigated in all monkeys. In the second step, the response to 7-day administration of latanoprost was evaluated in screened monkeys. We defined latanoprost low-responders as any monkey that showed intraocular pressure (IOP) reduction of 1 mm Hg or less during the 7-day treatment. Switching efficacy from latanoprost to tafluprost was then evaluated in a 3-phase switching study. Latanoprost was topically administered for about 1 week in phases 1 and 3, with tafluprost being topically administered for about 1 week in phase 2. Eleven monkeys were "latanoprost low-responders." The maximal IOP reduction exhibited by these low-responders in the second step of the evaluation was 0.5±0.2 mm Hg (mean±SEM) during saline treatment and 0.8±0.2 mm Hg during latanoprost treatment. In the 3-phase switching study, the maximal IOP reductions were: 0.4±0.2 mm Hg in phase 1 (latanoprost), 2.4±0.3 mm Hg in phase 2 (tafluprost), and 0.5±0.2 mm Hg in phase 3 (latanoprost). Latanoprost low-responders exist among cynomolgus monkeys. Switching from latanoprost to tafluprost reduced IOP, and tafluprost's IOP-lowering effect disappeared after switching back to latanoprost in the latanoprost low-responder monkeys. These results suggested that tafluprost might be effective for latanoprost nonresponder patients.

Bimatoprost Effects on Aqueous Humor Dynamics in Monkeys

The effects of bimatoprost on aqueous humor dynamics were quantified in monkey eyes. Uveoscleral outflow was measured by the anterior chamber perfusion method, using FITC-dextran. Total outflow facility was determined by the two-level constant pressure method. Aqueous flow was measured with a scanning ocular fluorophotometer. Uveoscleral outflow was 0.96 ± 0.19 μL min−1 in vehicle-treated eyes and 1.37 ± 0.27 μL min−1 (n = 6; P < .05) in eyes that received bimatoprost 0.01% b.i.d. × 5 days. Bimatoprost had no effect on total outflow facility, which was 0.42 ± 0.05 μL min−1 at baseline and 0.42 ± 0.04 μL min−1 after bimatoprost treatment. Bimatoprost had no significant effect on aqueous humor flow. This study demonstrates that bimatoprost increases uveoscleral outflow but not total outflow facility or aqueous humor flow, indicating that it lowers intraocular pressure in ocular normotensive monkeys by a mechanism that exclusively involves uveoscleral outflow.

The Prostanoid EP2Receptor Agonist Butaprost Increases Uveoscleral Outflow in the Cynomolgus Monkey

To investigate the ocular hypotensive effect of the prostanoid EP2 receptor agonist butaprost and to establish its mechanism of action. All experiments were performed in cynomolgus monkeys after topical application of butaprost (0.1%). The effects of butaprost on aqueous humor flow were determined by fluorophotometry. Total outflow facility was measured by the two-level, constant-pressure perfusion method, and uveoscleral outflow was determined by perfusion of FITC-labeled dextran through the anterior chamber. Effects on ocular morphology were studied after tissue fixation with transcardial perfusion by paraformaldehyde and immersion fixation of the globe, in animals subjected to long-term treatment with butaprost. Conscious ocular normotensive monkeys and monkeys with unilateral ocular hypertension were used for intraocular pressure (IOP) studies. Butaprost had no significant effect on aqueous humor flow or total outflow facility in ocular normotensive monkeys. Uveoscleral outflow was significantly higher in the butaprost treated eyes than in vehicle treated eyes, 1.03 +/- 0.20 vs. 0.53 +/- 0.18 microL.min(-1). After a 1-year treatment with butaprost, the morphology of the ciliary muscle was changed, showing increased spaces between ciliary muscle bundles and the apparent formation of new outflow channels. In many instances, changes were observed in the trabecular meshwork as well. Butaprost, in a single 0.1% dose, decreased IOP significantly in ocular normotensive monkeys and reduced IOP in laser-induced glaucomatous monkey eyes to the same level as that in the ocular normotensive contralateral eyes. The prostanoid EP2 receptor agonist butaprost appears to lower IOP by increasing uveoscleral outflow, according to both physiological and morphologic findings. Although the prostanoid EP2 receptor is structurally and functionally distinct from the FP receptor, the effects of EP2 and FP receptor stimulation on aqueous humor outflow are similar.

Effect of low-dose latrunculin B on anterior segment physiologic features in the monkey eye.

To determine if low doses of topical latrunculin B (LAT-B) will increase outflow facility and decrease intraocular pressure without damaging the cornea and if they will inhibit miotic and accommodative responses to pilocarpine in monkeys. We measured intraocular pressure (Goldmann tonometry) before and after 1 and 9 doses of 0.005% and 0.01% topical LAT-B and vehicle given twice daily on successive weeks; outflow facility (perfusion) following 15 doses; central corneal thickness (ultrasonic pachymetry) before and after 1 and 9 doses of 0.01% LAT-B and vehicle; pupillary diameter (calipers); and accommodation (refractometry) before and after 1 dose of 0.005% and 0.02% LAT-B. Latrunculin-B dose-dependently decreased intraocular pressure, multiple doses more than a single dose. Maximal mean +/- SEM hypotension after 1 dose was 2.5 +/- 0.3 mm Hg (0.005% LAT-B; n = 8; P<.001) or 2.7 +/- 0.6 mm Hg (0.01% LAT-B; n = 8; P<.005); maximal mean +/- SEM hypotension after 9 doses was 3.2 +/- 0.5 mm Hg (0.005% LAT-B; n = 8; P<.001) or 4.4 +/- 0.6 mm Hg (0.01% LAT-B; n = 8; P<.001). Outflow facility was increased by mean +/- SEM 75% +/- 13% (n = 7; P<.005). Central corneal thickness was not changed after 1 or 9 doses of 0.01% LAT-B. Miotic and accommodative responses to intramuscular pilocarpine were dose-dependently inhibited. With 0.02% LAT-B, inhibition of miosis was substantial, whereas the inhibition of accommodation was only about 25%. With 0.005% LAT-B, the effects were trivial. In ocular normotensive monkeys, 0.005% and 0.01% LAT-B administered topically increases outflow facility and/or decreases intraocular pressure without corneal effects. Multiple doses reduce intraocular pressure more than a single dose. Latrunculin-B dose-dependently relaxes the iris sphincter and ciliary muscle, with some separation of miotic and accommodative effects. Clinical Relevance Multiple treatments with low topical doses of LAT-B may substantially reduce outflow resistance in eyes with glaucoma without adversely affecting the cornea.

Effects of bunazosin hydrochloride on ciliary muscle constriction and matrix metalloproteinase activities.

To clarify the mechanism by which bunazosin hydrochloride (BZ), a selective alpha1-adrenoceptor antagonist, increases uveoscleral outflow. The effects of BZ on matrix metalloproteinase (MMP) activities in cultured monkey ciliary muscle cells, and on phenylephrine hydrochloride-induced constriction in bovine ciliary muscles, were examined. Also, the possible additive ocular hypotensive effects of BZ and latanoprost (LP) were evaluated in ocular normotensive monkeys. Although BZ at 10 to 10 M did not increase MMP-2, -3, and -9 activities in the culture medium of ciliary muscle cells, BZ at 10 to 10 M inhibited phenylephrine hydrochloride-induced constriction in ciliary muscles. The maximal reduction in intraocular pressure of concomitant administration of BZ and LP was greater than that of BZ alone and tended to be greater than that of LP alone. These findings, in normotensive monkeys, indicate that the mechanism whereby BZ increases uveoscleral outflow is independent of an effect on MMPs and is partly due to relaxation of the ciliary muscle. This effect is different from that of LP, which might help to explain the finding that topical concomitant administration of BZ and LP increased AUC(0-6h) value (IOP reduction) to 201% and 145% of BZ and LP given alone, respectively.

Pharmacological characteristics of AFP-168 (tafluprost), a new prostanoid FP receptor agonist, as an ocular hypotensive drug

To evaluate the pharmacological characteristics of AFP-168 (tafluprost), a new prostaglandin (PG) F 2α derivative, we examined its receptor-binding affinities, intraocular pressure (IOP)-lowering effect, effects on aqueous humor dynamics, and stimulating effect on melanogenesis. The receptor-binding profile for AFP-172, a carboxylic acid of AFP-168, was determined by measuring muscle contractions in an organ bath, inhibition of platelet aggregation, and competitive binding of a radio-labelled ligand. For the IOP-measurement study, ocular normotensive and laser-induced ocular hypertensive cynomolgus monkeys were used, and IOP was measured using a pneumatonograph. For the studies of aqueous humor dynamics, IOP (Goldmann applanation tonometry), fluorophotometry, two-level constant pressure perfusion, and isotope dilution and accumulation techniques were used in ocular normotensive monkeys. The melanin contents in the medium and in the cell bodies of cultured B16-F0 melanoma cells were measured. The affinity for the FP receptor shown by AFP-172 ( K i: 0·4 n m) was 12 times that of PhXA85 ( K i: 4·7 n m), a carboxylic acid of latanoprost. A single application of AFP-168 at 0·0025% significantly lowered IOP in both ocular normotensive and hypertensive monkeys (3·1 and 11·8 mmHg, respectively, p<0·01) and latanoprost at 0·005% significantly lowered IOP (2·1 mmHg, p<0·01 and 9·5 mmHg, p=0·059, respectively). Once daily instillation of AFP-168 at 0·001, 0·0025, or 0·005% for 5 days in normotensive monkeys significantly reduced IOP not only for a few hours, but also at the drug-trough time 24 hr after application. Latanoprost at 0·005% also reduced IOP, but not at the drug-trough time. AFP-168 decreased IOP mainly by increasing uveoscleral outflow by 65% ( p<0·05) and, as sometimes seen with other prostanoids, also increased total outflow facility (33% increase, p<0·05). In cultured B16-F0 melanoma cells, AFP-172 (100 μM) did not stimulate melanogenesis, but PhXA85 (100 μM) did. These findings indicate that AFP-168 has a high affinity for the prostanoid FP receptor, has potent IOP-lowering effects in both ocular normotensive and hypertensive monkeys that exceed those of latanoprost, and has less stimulating effect on melanogenesis in melanoma cells.

Apraclonidine and Brimonidine Effects on Anterior Ocular and Cardiovascular Physiology in Normal and Sympathectomized Monkeys

Apraclonidine and brimonidine administered topically to one eye of ketamine-anesthetized normal cynomolgus monkeys each produced a dose-related bilateral reduction in intraocular pressure which was not dependent on intact sympathetic innervation. Brimonidine was more potent and efficacious (10-12 mmHg maximum intraocular pressure reduction 2 hr after 200 μg) but produced a shorter-lasting effect than apraclonidine [4 mmHg maximum intraocular pressure reduction 1-6 hr after 600-1000 μg). Apraclonidine had little effect on pupil diameter, but brimonidine produced a dose-related bilateral miosis which was dependent on intact sympathetic innervation. Neither drug significantly affected refractive error. Topical brimonidine, but not apraclonidine, produced a dose-dependent reduction in mean arterial blood pressure, while both drugs lowered heart rate. A dose-dependent bilateral reduction in aqueous humor flow rate calculated over a 6-hr period following drug administration was produced by both topical apraclonidine (maximum 30-35% reduction with 600 μg) and brimonidine (maximum 30-45% reduction with 50-250 μg), which was not dependent on intact sympathetic innervation. Maintenance of blood pressure by intravenous infusion of angiotensin II had no effect on the aqueous humor flow suppression produced by 100 μg of topical brimonidine, but pentobarbital anesthesia abolished it. Intracameral injection of 10 μg brimonidine in rhesus monkeys produced an ipsilatera ∼ 15% reduction in aqueous humor flow calculated for the 1-3 hr post-injection period. The cardiovascular and contralateral ocular effects observed with both drugs are presumably related to the monkeys' small body weight, and the magnitude of IOP reduction for a given degree of flow suppression would be greater in hypertensive than in normotensive eyes. Caution must therefore be exercised in extrapolating from our data in ocular normotensive monkeys to the glaucomatous human.

The DP-Receptor Agonist SQ27986 Raises but Does Not Lower Intraocular Pressure in Ocular Normotensive Monkeys

The DP-Receptor Agonist SQ27986 Raises but Does Not Lower Intraocular Pressure in Ocular Normotensive Monkeys