Ocular Pharmacology and Toxicology of TRPV1 Antagonist SAF312 (Libvatrep).

Purpose: To evaluate the pharmacology and toxicology of SAF312, a transient receptor potential vanilloid 1 (TRPV1) antagonist. Methods: TRPV1 expression in human ocular tissues was evaluated with immunohistochemistry. Inhibition of calcium influx in Chinese hamster ovary (CHO) cells expressing human TRPV1 (hTRPV1) and selectivity of SAF312 were assessed by a fluorescent imaging plate reader assay. Ocular tissue and plasma pharmacokinetics (PK) were assessed following a single topical ocular dose of SAF312 (0.5%, 1.0%, 1.5%, 2.5%) in rabbits. Safety and tolerability of SAF312 were evaluated in rabbits and dogs. Effects of SAF312 on corneal wound healing after photorefractive keratectomy (PRK) surgery were assessed in rabbits. Results: TRPV1 expression was noted in human cornea and conjunctiva. SAF312 inhibited calcium influx in CHO-hTRPV1 cells induced by pH 5.5 (2-[N-morpholino] ethanesulfonic acid), N-arachidonoylethanolamine, capsaicin, and N-arachidonoyl dopamine, with IC50 values of 5, 10, 12, and 27 nM, respectively, and inhibition appeared noncompetitive. SAF312 demonstrated high selectivity for TRPV1 (>149-fold) over other TRP channels. PK analysis showed highest concentrations of SAF312 in cornea and conjunctiva. SAF312 was found to be safe and well tolerated in rabbits and dogs up to the highest feasible concentration of 2.5%. No delay in wound healing after PRK was observed. Conclusions: SAF312 is a potent, selective, and noncompetitive antagonist of hTRPV1 with an acceptable preclinical safety profile for use in future clinical trials. Translational Relevance: SAF312, which was safe and well tolerated without causing delay in wound healing after PRK in rabbits, may be a potential therapeutic agent for ocular surface pain.

A Randomized, Double-Masked, Multicenter Trial of Topical Acrizanib (LHA510), a Tyrosine Kinase VEGF-Receptor Inhibitor, in Treatment-Experienced Subjects With Neovascular Age-Related Macular Degeneration.

PURPOSE: To evaluate whether topical acrizanib (LHA510), a small-molecule vascular endothelial growth factor receptor inhibitor, could suppress the need for anti-vascular endothelial growth factor therapy over a 12-week period in patients with neovascular age-related macular degeneration. DESIGN: A phase 2 multicenter randomized double-masked, vehicle-controlled proof-of-concept study. METHODS: Trial includes n = 90 patients with active choroidal neovascularization due to neovascular age-related macular degeneration and under anti-vascular endothelial growth factor treatment. All patients received an intravitreal injection of ranibizumab at baseline and were retreated when there was evidence of disease recurrence (rescue). Patients were randomized 1:1 to receive topical LHA510 or vehicle for 12 weeks. Drops were administered twice a day for 8 weeks and then 3 times a day for the last 4 weeks. MAIN OUTCOME MEASURE: The primary outcome was the number of patients requiring rescue over 84 days of topical dosing. Key secondary outcome measures were time to first rescue, total number of ranibizumab injections, changes in central subfield thickness, and changes of visual acuity from baseline to day 84. RESULTS: The extended per protocol set included 70 patients of whom 25 of 33 patients in the LHA510 group (75.8%) and 25 of 37 patients in the placebo group (67.6%) required rescue by day 84 (P = .8466). Secondary and subgroup analysis did not support evidence of efficacy. Twenty-one of 46 patients administered LHA510 developed a reversible corneal haze that resolved with cessation of treatment and did not recur in patients restarted at once daily frequency. CONCLUSION: In spite of extensive optimization for topical efficacy, LHA510 failed to demonstrate clinical efficacy.

Ranibizumab Population Pharmacokinetics and Free VEGF Pharmacodynamics in Preterm Infants With Retinopathy of Prematurity in the RAINBOW Trial.

Purpose: To develop a population pharmacokinetic (PK) model for intravitreal ranibizumab in infants with retinopathy of prematurity (ROP) and assess plasma free vascular endothelial growth factor (VEGF) pharmacodynamics (PD). Methods: The RAnibizumab compared with laser therapy for the treatment of INfants BOrn prematurely With retinopathy of prematurity (RAINBOW) trial enrolled 225 infants to receive a bilateral intravitreal injection of ranibizumab 0.1 mg, ranibizumab 0.2 mg, or laser in a 1:1:1 ratio and included sparse sampling of blood for population PK and PD analysis. An adult PK model using infant body weight as a fixed allometric covariate was re-estimated using the ranibizumab concentrations in the preterm population. Different variability, assumptions, and covariate relationships were explored. Model-based individual predicted concentrations of ranibizumab were plotted against observed free VEGF concentrations. Results: Elimination of ranibizumab had a median half-life of 5.6 days from the eye and 0.3 days from serum, resulting in an apparent serum half-life of 5.6 days. Time to reach maximum concentration was rapid (median: 1.3 days). Maximum concentration (median 24.3 ng/mL with ranibizumab 0.2 mg) was higher than that reported in adults. No differences in plasma free VEGF concentrations were apparent between the groups or over time. Plotted individual predicted concentrations of ranibizumab against observed free VEGF concentrations showed no relationship. Conclusions: In preterm infants with ROP, elimination of ranibizumab from the eye was the rate-limiting step and was faster compared with adults. No reduction in plasma free VEGF was observed. The five-year clinical safety follow-up from RAINBOW is ongoing. Translational Relevance: Our population PK and VEGF PD findings suggest a favorable ocular efficacy: systemic safety profile for ranibizumab in preterm infants.

Models and Approaches Describing the Metabolism, Transport, and Toxicity of Drugs Administered by the Ocular Route.

The eye is a complex organ with a series of anatomic barriers that provide protection from physical and chemical injury while maintaining homeostasis and function. The physiology of the eye is multifaceted, with dynamic flows and clearance mechanisms. This review highlights that in vitro ocular transport and metabolism models are confined by the availability of clinically relevant absorption, distribution, metabolism, and excretion (ADME) data. In vitro ocular transport models used for pharmacology and toxicity poorly predict ocular exposure. Although ocular cell lines cannot replicate in vivo conditions, these models can help rank-order new chemical entities in discovery. Historic ocular metabolism of small molecules was assumed to be inconsequential or assessed using authentic standards. While various in vitro models have been cited, no single system is perfect, and many must be used in combination. Several studies document the use of laboratory animals for the prediction of ocular pharmacokinetics in humans. This review focuses on the use of human-relevant and human-derived models which can be utilized in discovery and development to understand ocular disposition of new chemical entities. The benefits and caveats of each model are discussed. Furthermore, ADME case studies are summarized retrospectively and capture the ADME data collected for health authorities in the absence of definitive guidelines. Finally, we discuss the novel technologies and a hypothesis-driven ocular drug classification system to provide a holistic perspective on the ADME properties of drugs administered by the ocular route.

Distribution of topical ocular nepafenac and its active metabolite amfenac to the posterior segment of the eye.

Nepafenac ophthalmic suspensions, 0.1% (NEVANAC(®)) and 0.3% (ILEVRO™), are topical nonsteroidal anti-inflammatory drug (NSAID) products approved in the United States, Europe and various other countries to treat pain and inflammation associated with cataract surgery. NEVANAC is also approved in Europe for the reduction in the risk of postoperative macular edema (ME) associated with cataract surgery in diabetic patients. The efficacy against ME suggests that topical administration leads to distribution of nepafenac or its active metabolite amfenac to the posterior segment of the eye. This article evaluates the ocular distribution of nepafenac and amfenac and the extent of local delivery to the posterior segment of the eye, following topical ocular instillation in animal models. Nepafenac ophthalmic suspension was instilled unilaterally in New Zealand White rabbits as either a single dose (0.1%; one drop) or as multiple doses (0.3%, one drop, once-daily for 4 days, or 0.1% one drop, three-times daily for 3 days and one morning dose on day 4). Nepafenac (0.3%) was also instilled unilaterally in cynomolgus monkeys as multiple doses (one drop, three-times daily for 7 days). Nepafenac and amfenac concentrations in harvested ocular tissues were measured using high-performance liquid chromatography/mass spectrometry. Locally-distributed compound concentrations were determined as the difference in levels between dosed and undosed eyes. In single-dosed rabbit eyes, peak concentrations of locally-distributed nepafenac and amfenac showed a trend of sclera > choroid > retina. Nepafenac peak levels in sub-samples posterior to the eye equator and inclusive of the posterior pole (E-PP) were 55.1, 4.03 and 2.72 nM, respectively, at 0.25 or 0.50 h, with corresponding amfenac peak levels of 41.9, 3.10 and 0.705 nM at 1 or 4 h. By comparison, peak levels in sclera, choroid and retina sub-samples in a band between the ora serrata and the equator (OS-E) were 13- to 40-fold (nepafenac) or 11- to 23-fold (amfenac) higher, indicating an anterior-to-posterior directional concentration gradient. In multiple-dosed rabbit eyes, with 0.3% nepafenac instilled once-daily or 0.1% nepafenac instilled three-times daily, cumulative 24-h locally-distributed levels of nepafenac in E-PP retina were similar between these groups, whereas exposure to amfenac once-daily dosing nepafenac 0.3% was 51% of that achieved with three-times daily dosing of 0.1%. In single-dosed monkey eyes, concentration gradients showed similar directionality as observed in rabbit eyes. Peak concentrations of locally-distributed nepafenac were 1580, 386, 292 and 13.8 nM in E-PP sclera, choroid and retina, vitreous humor, respectively, at 1 or 2 h after drug instillation. Corresponding amfenac concentrations were 21.3, 11.8, 2.58 and 2.82 nM, observed 1 or 2 h post-instillation. The data indicate that topically administered nepafenac and its metabolite amfenac reach pharmacologically relevant concentrations in the posterior eye segment (choroid and retina) via local distribution, following an anterior-to-posterior concentration gradient. The proposed pathway involves a choroidal/suprachoroidal or periocular route, along with an inward movement of drug through the sclera, choroid and retina, with negligible vitreal compartment involvement. Sustained high nepafenac concentrations in posterior segment tissues may be a reservoir for hydrolysis to amfenac.

Ocular pharmacokinetics comparison between 0.2% olopatadine and 0.77% olopatadine hydrochloride ophthalmic solutions administered to male New Zealand white rabbits.

PURPOSE: The primary objective of this study was to compare uptake and distribution of the commercially available formulation of 0.2% olopatadine and the newly developed 0.77% olopatadine hydrochloride ophthalmic solution formulation with improved solubility following a single (30 µL), bilateral topical ocular dose in male New Zealand white rabbits. METHODS: Each animal received a single 30-µL topical ocular dose (0.2% olopatadine or 0.77% olopatadine hydrochloride ophthalmic solution) to the right (OD) eye followed by the left (OS) eye for a total dose of 60 µL. Olopatadine concentrations were measured in ocular tissues (cornea, bulbar, conjunctiva, choroid, iris-ciliary body, whole lens, retina), aqueous humor, and plasma at prespecified time points over 24 h using a qualified liquid chromatography coupled with mass spectrometry (LC-MS/MS) analytical method. RESULTS: Olopatadine was absorbed into the eye and reached maximal levels (Cmax) within 30 min (0.5 h) to 2 h (Tmax) in ocular tissues and plasma for both treatment groups, except for the lens in which the Tmax was 4 h in the 0.2% olopatadine group and 8 h in the 0.77% olopatadine hydrochloride group, respectively. Tissues associated with the site of dosing, that is, the conjunctiva and cornea, had the highest concentrations of olopatadine in both the 0.2% olopatadine (609 and 720 ng/g) and 0.77% olopatadine hydrochloride (3,000 and 2,230 ng/g) dose groups. The greatest differences between 0.2% olopatadine and 0.77% olopatadine hydrochloride were associated with the overall duration and level of ocular exposures. CONCLUSIONS: The newly developed 0.77% olopatadine hydrochloride ophthalmic solution formulation resulted in a higher and more prolonged olopatadine concentration in the target tissue, that is, conjunctiva compared to the commercial formulation of 0.2% olopatadine ophthalmic solution.

Intraocular distribution of melanin in human, monkey, rabbit, minipig and dog eyes.

The purpose of this study was to quantify the melanin pigment content in sclera, choroid-RPE, and retina, three tissues encountered during transscleral drug delivery to the vitreous, in human, rabbit, monkey, minipig, and dog models. Strain differences were assessed in NZW × NZR F1 and Dutch belted rabbits and Yucatan and Gottingen minipigs. The choroid-RPE and retina tissues were divided into central (posterior pole area) and peripheral (away from posterior pole) regions while the sclera was analyzed without such division. Melanin content in the tissues was analyzed using a colorimetric assay. In all species the rank order for pigment content was: choroid-RPE >retina ≥ sclera, except in humans, where scleral melanin levels were higher than retina and central choroid. The melanin content in a given tissue differed between species. Further, while the peripheral tissue pigment levels tended to be generally higher compared to the central regions, these differences were significant in human in the case of choroid-RPE and in human, monkey, and dogs in the case of retina. Strain difference was observed only in the central choroid-RPE region of rabbits (NZW × NZR F1 >Dutch Belted). Species, strain, and regional differences exist in the melanin pigment content in the tissues of the posterior segment of the eye, with Gottingen minipig being closest to humans among the animals assessed. These differences in melanin content might contribute to differences in drug binding, delivery, and toxicity.

In vitro transport and partitioning of AL-4940, active metabolite of angiostatic agent anecortave acetate, in ocular tissues of the posterior segment.

PURPOSE: The purpose of this study was to evaluate partitioning into and transport across posterior segment tissues (sclera, retinal pigment epithelium (RPE)-choroid) of AL-4940, the active metabolite of angiostatic cortisene anecortave acetate (AL-3789). METHODS: Transport of [(14)C]-AL-4940 was measured through RPE-choroid-sclera (RCS) and sclera, excised from Dutch Belted pigmented rabbits' eyes, in the directions of scleral to vitreal (S-->V) and vitreal to scleral (V-->S) for 3 h at 37 degrees C using Ussing chambers. Tissue integrity was monitored by transepithelial electrical resistance (TEER), potential difference (PD), and biochemical assay (LDH). Partitioning in RPE-choroid and sclera was determined separately for both [(14)C]-AL-4940 and [(14)C]-AL-3789. Mathematical analysis for bilaminate membranes used partitioning and transport data to derive diffusion coefficients for 2 tissue layers sclera and RPE-choroid. RESULTS: Partitioning of drug in tissue was comparable for both [(14)C]-AL-4940 and [(14)C]-AL-3789. Partition coefficients of drug in tissue were 2.2 for sclera and about 4 for RPE-choroid. Permeability through sclera alone was about 3 x 10(-5) cm/s and about 1 x 10(-5) cm/s through the RCS tissue, irrespective of the direction of transport (S-->V) or (V-->S). Results from bioelectrical and biochemical evaluation of tissue with modified LDH assay provided evidence that the RCS tissue preparation remained viable during the period of transport study. CONCLUSIONS: The thin RPE-choroid layer contributes significantly to resistance to drug transport, and diffusivity in this layer is 10 times less than in sclera. This experimental scheme is proposed as an important component for the development of a general ocular physiologically based pharmacokinetic model.

Concentrations of betaxolol in ocular tissues of patients with glaucoma and normal monkeys after 1 month of topical ocular administration.

PURPOSE: To measure the concentration of betaxolol in tissues of humans with glaucoma and normal monkeys after topical administration. METHODS: Enucleated eyes (n = 7) of patients with glaucoma (age range, 27-79 years), without apparent anatomic disruption that would be likely to influence betaxolol absorption and intraocular distribution (exceptions: one pseudophakic, one aphakic) or other disease, were analyzed for betaxolol concentrations after self-administration of 0.25% betaxolol twice daily for 28 days or longer. The last instillation was made within 6 hours of surgery. Cynomolgus monkeys (n = 3) received 0.25% betaxolol twice daily unilaterally for 30 days. Betaxolol was measured by HPLC and tandem mass spectrometry (MS/MS) in plasma and ocular tissues. RESULTS: In humans, mean betaxolol concentrations (excluding the aphakic patient) were 71.4 +/- 41.8 ng/g in the retina, 31.2 +/- 14.8 ng/g in the optic nerve head, and 1290 +/- 1170 ng/g in the choroid. Mean concentrations in the iris and ciliary body were 73,200 +/- 89,600 and 4,250 +/- 3,020 ng/g, respectively. Betaxolol concentration was higher in all ocular tissues than in the plasma (0.59 +/- 0.32 ng/mL). In the monkeys the concentrations in the posterior tissues of the treated eyes were higher than in the untreated eyes, with mean differences in the retina and optic nerve head of 121 and 130 ng/g, respectively. CONCLUSIONS: Topically applied betaxolol was bioavailable to posterior ocular tissues, including the retina and optic nerve head, of patients with glaucoma and of normal cynomolgus monkeys. The higher betaxolol levels in the treated versus untreated monkey eyes are consistent with betaxolol's reaching posterior tissues by local absorption and distribution.