Enhancing the hypotensive effect of latanoprost by combining synthetic phosphatidylcholine liposomes with hyaluronic acid and osmoprotective agents

The first line of glaucoma treatment focuses on reducing intraocular pressure (IOP) through the prescription of topical prostaglandin analogues, such as latanoprost (LAT). Topical ophthalmic medicines have low bioavailability due to their rapid elimination from the ocular surface. Nanotechnology offers innovative ways of enhancing the ocular bioavailability of antiglaucoma agents while reducing administration frequency. This study aims to combine LAT-loaded synthetic phosphatidylcholine liposomes with hyaluronic acid (0.2% w/v) and the osmoprotectants betaine (0.40% w/v) and leucine (0.90% w/v) (LAT-HA-LIP) to extend the hypotensive effect of LAT while protecting the ocular surface. LAT-HA-LIP was prepared as a mixture of 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dimyristoyl-sn-glycero-3-phosphocholine, cholesterol and α-tocopherol acetate. LAT-HA-LIP exhibited high drug-loading capacity (104.52 ± 4.10%), unimodal vesicle sizes (195.14 ± 14.34 nm) and a zeta potential of -13.96 ± 0.78 mV. LAT-HA-LIP was isotonic (284.00 ± 1.41 mOsm L-1), had neutral pH (7.63 ± 0.01) and had suitable surface tension (44.07 ± 2.70 mN m-1) and viscosity (2.69 ± 0.15 mPa s-1) for topical ophthalmic administration. LAT-HA-LIP exhibited optimal in vitro tolerance in human corneal and conjunctival epithelial cells. No signs of ocular alteration or discomfort were observed when LAT-HA-LIP was instilled in albino male New Zealand rabbits. Hypotensive studies revealed that, after a single eye drop, the effect of LAT-HA-LIP lasted 24 h longer than that of a marketed formulation and that relative ocular bioavailability was almost three times higher (p < 0.001). These findings indicate the potential ocular protection and hypotensive effect LAT-HA-LIP offers in glaucoma treatment.

Topical Ocular Therapeutics in Small Animals

This article reviews the administration of common topical ophthalmic medications, in relation to factors influencing absorption including composition of topical ophthalmic preparations, and potential systemic effects. Commonly prescribed, commercially available topical ophthalmic medications are discussed with respect to pharmacology, their indications for use, and adverse effects. Knowledge of topical ocular pharmacokinetics is essential for the management of veterinary ophthalmic disease.

Comparative effects of latanoprost and latanoprostene bunod on intraocular pressure and pupil size in ophthalmologically normal Beagle dogs

OBJECTIVE

To compare effects of latanoprost, a topical prostaglandin analogue (PGA) commonly used to treat glaucoma and lens instability in dogs, and latanoprostene bunod, a novel PGA with a nitric oxide-donating moiety, on intraocular pressure (IOP) and pupil diameter (PD).

ANIMALS STUDIED

Ten ophthalmologically normal Beagle dogs.

PROCEDURES

Dogs were treated twice a day for 5 days in a randomly selected eye with either latanoprost or latanoprostene bunod. After a 6-week washout period, dogs were treated with the opposite drug. IOP and PD were measured at treatment times, at midday on days 1 and 5, and for 6 days post-treatment.

RESULTS

Both drugs significantly decreased IOP and PD. At midday on day 5 of treatment, mean IOP in eyes treated with latanoprost was 4.5 mmHg lower than the fellow eye and 3.0 mmHg lower than the same eye at baseline, while mean IOP in eyes treated with latanoprostene bunod was 5.5 mmHg lower than the fellow eye and 3.6 mmHg lower than baseline. Mean PD was 0.94 mm in eyes treated with latanoprost and 0.76 mmHg in eyes treated with latanoprostene bunod. There was no significant difference between the two drugs for either parameter at that time point (p = .372 and .619, respectively, for IOP relative to control and to baseline; p = .076 for PD) or when analyzed longitudinally. Significant diurnal variation in PD was noted and may have implications for treatment of lens' instability.

CONCLUSIONS

Latanoprost and latanoprostene bunod produce similar IOP reduction and miosis in normal canine eyes.

Safety and efficacy of topically administered netarsudil-latanoprost fixed dose combination (FDC; Rocklatan™) in normal and glaucomatous dogs with ADAMTS10-open-angle glaucoma (ADAMTS10-OAG)

OBJECTIVE

The aim of the study was to evaluate safety and efficacy of topically administered 0.02% netarsudil-0.005% latanoprost fixed-dose combination (FDC) (Rocklatan™; Aerie Pharmaceutical) in normal and glaucomatous dogs with ADAMTS10-open-angle glaucoma (ADAMTS10-OAG).

ANIMALS STUDIED

Five normal and five glaucomatous beagle dogs with ADAMTS10-OAG were the study animals.

PROCEDURES

In each dog, left (OS) or right eye (OD) was randomly selected for netarsudil-latanoprost FDC treatment. Contralateral eyes served as latanoprost-treated controls. The study was divided into four consecutive study periods: following a 4-day baseline period, two sequential 8-day study periods followed with once daily (q24h) and twice daily (q12h) treatments and ending with a washout period. Efficacy was measured by diurnal intraocular pressure (IOP) and pupil diameter. Safety was assessed by routine ophthalmic examination, gonioscopy, and pachymetry. Differences in least square means of quantitative outcome measures were compared between FDC and latanoprost treatments by using the linear Gaussian model.

RESULTS

Baseline IOPs were 13.6 ± 0.7 mmHg (mean ± SEM) in normal and 28.3 ± 1.4 mmHg in OAG-affected dogs. There was a significant decrease in mean diurnal IOP following FDC administration in both normal (q24h: -2.1 mmHg; q12h: -4.1 mmHg) and glaucomatous dogs (q24h: -14.2 mmHg; q12h: -17.7 mmHg; p < .0001). There was no significant difference in the treatment effect when comparing FDC to latanoprost. Both FDC and latanoprost administration resulted in similarly significant pupil constriction (p < .0001). The FDC administration was well-tolerated but resulted in conjunctival hyperemia.

CONCLUSIONS

Once or twice daily administration of netarsudil-latanoprost FDC (Rocklatan™) and latanoprost was equally effective in lowering IOP in normal and OAG-affected dogs. There was no netarsudil-related added treatment effect.

Looking into the future: Gene and cell therapies for glaucoma

Glaucoma is a complex group of optic neuropathies that affects both humans and animals. Intraocular pressure (IOP) elevation is a major risk factor that results in the loss of retinal ganglion cells (RGCs) and their axons. Currently, lowering IOP by medical and surgical methods is the only approved treatment for primary glaucoma, but there is no cure, and vision loss often progresses despite therapy. Recent technologic advances provide us with a better understanding of disease mechanisms and risk factors; this will permit earlier diagnosis of glaucoma and initiation of therapy sooner and more effectively. Gene and cell therapies are well suited to target these mechanisms specifically with the potential to achieve a lasting therapeutic effect. Much progress has been made in laboratory settings to develop these novel therapies for the eye. Gene and cell therapies have already been translated into clinical application for some inherited retinal dystrophies and age-related macular degeneration (AMD). Except for the intravitreal application of ciliary neurotrophic factor (CNTF) by encapsulated cell technology for RGC neuroprotection, there has been no other clinical translation of gene and cell therapies for glaucoma so far. Possible application of gene and cell therapies consists of long-term IOP control via increased aqueous humor drainage, including inhibition of fibrosis following filtration surgery, RGC neuroprotection and neuroregeneration, modification of ocular biomechanics for improved IOP tolerance, and inhibition of inflammation and neovascularization to prevent the development of some forms of secondary glaucoma.

Effects of 0.02% netarsudil ophthalmic solution on intraocular pressure of normotensive dogs

OBJECTIVES

To evaluate the effect of QD or BID 0.02% netarsudil ophthalmic solution (Aerie Pharmaceuticals) on intraocular pressure (IOP) in normotensive dogs and to describe any adverse effects.

ANIMALS STUDIED

Normotensive Labrador retriever dogs were included in this study: 10 received netarsudil in one eye and artificial tears in the contralateral eye QD, and 10 received netarsudil in one eye and artificial tears in the contralateral eye BID.

PROCEDURES

Intraocular pressure curves were acquired over a 3-day acclimation period, 5-day dosing period (QD or BID-10 dogs/group), and 3-day recovery period. Toxicity was assessed daily using slit-lamp biomicroscopy and the semiquantitative preclinical ocular toxicology scoring system.

RESULTS

Once-daily dosing did not lower IOP over the entire 5-day dosing period (95% CI 0.1 to -0.9 mm Hg, P = .20) or on the last day of dosing (95% CI 0.4 to -0.9 mm Hg, P = .65). Twice-daily dosing resulted in a statistically significant, but clinically unimportant, IOP reduction over the entire 5-day dosing period (-0.6 mm Hg; 95% CI 0.05 to -1.1 mm Hg, P = .02) and on the last day of dosing (-0.9 mm Hg; 95% CI 0.2 to -1.5 mm Hg, P = .003). Adverse events were limited to transient mild-to-moderate conjunctival hyperemia during the dosing phase in eyes receiving netarsudil vs control (P < .0001).

CONCLUSIONS

Netarsudil 0.02% ophthalmic solution twice daily resulted in a small, statistically significant, but clinically unimportant, IOP reduction in normotensive dogs. Future studies should investigate efficacy in glaucomatous dogs.

Safety and efficacy of topically administered netarsudil (Rhopressa™) in normal and glaucomatous dogs with ADAMTS10-open-angle glaucoma (ADAMTS10-OAG)

OBJECTIVE

To evaluate safety and efficacy of topically administered 0.02% netarsudil ophthalmic solution (Rhopressa™; Aerie Pharmaceutical) in normal and glaucomatous dogs with ADAMTS10-open-angle glaucoma (ADAMTS10-OAG).

ANIMALS STUDIED

Five normal and 5 glaucomatous Beagle dogs with ADAMTS10-OAG.

PROCEDURES

In each dog, left or right eye was randomly selected for netarsudil treatment. Contralateral eyes were sham-treated with balanced salt solution (BSS). Following a 1-week baseline period, dogs were treated once daily (q24h) during week 2, and twice daily (q12h) during week 3; week 4 served as washout period. Efficacy was measured by diurnal intraocular pressure (IOP) and pupil diameter. Safety was assessed by routine ophthalmic examination, gonioscopy, and pachymetry. Differences in least square means of quantitative outcome measures were compared between netarsudil and BSS sham-treated eyes by linear Gaussian model.

RESULTS

Baseline IOPs were 18.5 ± 0.5 mm Hg (mean ± SEM) in normal and 27.8 ± 1.0 mm Hg in OAG dogs. Even though mean IOPs were lower in netarsudil- vs sham-treated eyes, the overall differences were neither significant nor clinically relevant, regardless of treatment frequency (q24h-normal: sham 16.4 ± 1.1 mm Hg vs treatment 15.6 ± 1.0 mm Hg; q24hr-OAG: sham 25.8 ± 2.3 mm Hg vs. treatment 25.7 ± 2.4 mm Hg; q12hr-normal: sham 15.4 ± 0.8 mm Hg vs. treatment 14.4 ± 0.8 mm Hg; q12hr-OAG: sham 26.3 ± 1.7 mm Hg vs. treatment 25.4 ± 1.8 mm Hg). Netarsudil administration was well tolerated but resulted in significant, moderate-to-severe conjunctival hyperemia (P < .001).

CONCLUSIONS

Once or twice daily administration of netarsudil resulted in marginal and clinically irrelevant IOP decreases in normal and OAG-affected dogs. Except for conjunctival hyperemia, the drug was well tolerated.

Effect of topical ophthalmic administration of 0.005% latanoprost solution on aqueous humor flow rate and intraocular pressure in ophthalmologically normal adult Beagles

OBJECTIVE

To determine the effect of topical ophthalmic administration of 0.005% latanoprost solution on aqueous humor flow rate (AHFR) and intraocular pressure (IOP) in ophthalmologically normal dogs.

ANIMALS

12 adult Beagles.

PROCEDURES

In a masked crossover design involving two 10-day experimental periods separated by a 7-day washout period, dogs were randomly assigned to first receive latanoprost or artificial tears (control) solution and then the opposite treatment in the later experimental period. Each experimental period was divided into a baseline phase (days 1 to 3), baseline fluorophotometry assessment (day 4), treatment phase (1 drop of latanoprost or artificial tears solution administered twice daily in each eye on days 5 to 9 and once on day 10), and posttreatment fluorophotometry assessment (day 10). Measured fluorescein concentrations were used to calculate baseline and posttreatment AHFRs. The IOP was measured 5 times/d in each eye during baseline and treatment (days 5 to 9) phases.

RESULTS

Mean baseline and posttreatment AHFR values did not differ significantly in either experimental period (latanoprost or control). In the latanoprost period, mean IOP was significantly lower during treatment than at baseline; there was no difference in corresponding IOP values during the control period. In the latanoprost period, mean IOP was significantly higher on the first day of treatment than on subsequent treatment days.

CONCLUSIONS AND CLINICAL RELEVANCE

In ophthalmologically normal dogs, topical ophthalmic administration of 0.005% latanoprost solution significantly decreased IOP but did not affect AHFR. Thus, the ocular hypotensive effect of latanoprost did not appear to have been caused by a reduction in aqueous humor production. (Am J Vet Res 2019;80:498-504).